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(Phys) Fundamental Particles

 
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adedios
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PostPosted: Sat Sep 09, 2006 7:11 am    Post subject: (Phys) Fundamental Particles Reply with quote






Neutrinos and other fundamental particles

Angel C. de Dios
9 September 2006

Neutrinos are among the most elusive fundamental particles. Neutrinos unlike electrons do not carry an electrical charge. They are neutral. Their existence was first suggested by Pauli who noticed that in some radioactive decays, energy and momentum are not strictly conserved. Therefore, there must be additional particles that has mass and can carry this missing energy, but are not detected because they do not interact with electrical fields.

In this topic, neutrinos and other fundamental particles will be explored.

*************************************************************

Questions to explore further this topic:

What are the fundamental particles?

http://education.jlab.org/atom.....icles.html
http://www2.slac.stanford.edu/.....ental.html
http://pdg.lbl.gov/fireworks/intro_eng.swf
http://www.pbs.org/wgbh/nova/e.....flash.html
http://www.pp.rhul.ac.uk/hep/talk/pptalk.ppt
http://www.physics.usyd.edu.au.....ntals.html
http://particleadventure.org/p.....chart.html
http://www.lns.cornell.edu/pub.....quark.html
http://na47sun05.cern.ch/targe.....icles.html

A world of particles



How are fundamental particles detected and discovered?

http://ed.fnal.gov/projects/exhibits/searching/

The Particle Adventure

http://particleadventure.org/f.....ndard.html

The ABC's of Nuclear Science

http://www.lbl.gov/abc/Basic.html

Classroom activities for particle physics

http://particleadventure.org/o.....index.html
http://eddata.fnal.gov/lasso/q.....view.lasso

The Elegant Universe: The Video

http://www.pbs.org/wgbh/nova/elegant/program.html

A Particle Accelerator

http://microcosm.web.cern.ch/M.....ty/ex.html

What are neutrinos?

http://www.pparc.ac.uk/Ps/bbs/bbs_neut.asp
http://www.ps.uci.edu/~superk/neutrino.html

Lesson Plans (high school level)

http://www.soudan.umn.edu/outreach/6_9.html
http://www.soudan.umn.edu/outreach/9_12.html


GAMES

http://ed.fnal.gov/projects/labyrinth/games/
http://education.jlab.org/indexpages/paper.html
http://www.sudan.umn.edu/outre.....opardy.ppt
http://www.soudan.umn.edu/outr.....0bingo.doc
http://chainreaction.asu.edu/


Last edited by adedios on Tue Oct 30, 2007 1:28 pm; edited 5 times in total
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PostPosted: Mon Oct 23, 2006 11:19 am    Post subject: Experimenters at Fermilab discover exotic relatives of proto Reply with quote

October 23, 2006

Fermilab - Kurt Riesselmann
Photos and graphics at:
http://www.fnal.gov/pub/pressp.....mages.html

Experimenters at Fermilab discover exotic relatives of protons and neutrons

Batavia, Illinois-Scientists of the CDF collaboration at the Department of Energy's Fermi National Accelerator Laboratory announced today (October 23, 2006) the discovery of two rare types of particles, exotic relatives of the much more common proton and neutron.

"These particles, named Sigma-sub-b [Σb], are like rare jewels that we mined out of our data," said Jacobo Konigsberg, University of Florida, a spokesperson for the CDF collaboration. "Piece by piece, we are developing a better picture of how matter is built out of quarks. We learn more about the subatomic forces that hold quarks together and tear them apart. Our discovery helps complete the 'periodic table of baryons.'"

Baryons (derived from the Greek word "barys", meaning "heavy") are particles that contain three quarks, the most fundamental building blocks of matter. The CDF collaboration discovered two types of Sigma-sub-b particles, each one about six times heavier than a proton.

There are six different types of quarks: up, down, strange, charm, bottom and top (u, d, s, c, b and t). The two types of baryons discovered by the CDF experiment are made of two up quarks and one bottom quark (u-u-b), and two down quarks and a bottom quark (d-d-b). For comparison, protons are u-u-d combinations, while neutrons are d-d-u. The new particles are extremely short-lived and decay within a tiny fraction of a second.

Utilizing Fermilab's Tevatron collider, the world's most powerful particle accelerator, physicists can recreate the conditions present in the early formation of the universe, reproducing the exotic matter that was abundant in the moments after the big bang. While the matter around us is comprised of only up and down quarks, exotic matter contains other quarks as well.

The Tevatron collider at Fermilab accelerates protons and antiprotons close to the speed of light and makes them collide. In the collisions, energy transforms into mass, according to Einstein's famous equation E=mc2. To beat the low odds of producing bottom quarks--which in turn transform into the Sigma-sub-b according to the laws of quantum physics--scientists take advantage of the billions of collisions produced by the Tevatron each second.

"It's amazing that scientists can build a particle accelerator that produces this many collisions, and equally amazing that the CDF collaboration was able to develop a particle detector that can measure them all," said CDF cospokesperson Rob Roser, of Fermilab. "We are confident that our data hold the secret to even more discoveries that we will find with time."

The CDF experiment identified 103 u-u-b particles, positively charged Sigma-sub-b particles (Σ+b), and 134 d-d-b particles, negatively charged Sigma-sub-b particles (Σ-b). In order to find this number of particles, scientists culled through more than 100 trillion high-energy proton-antiproton collisions produced by the Tevatron over the last five years.

In a scientific presentation on Friday, October 20, CDF physicist Petar Maksimovic, professor at Johns Hopkins University, presented the discovery to the particle physics community at Fermilab. He explained that the two types of Sigma-sub-b particles are produced in two different spin combinations, J=1/2 and J=3/2, representing a ground state and an excited state, as predicted by theory.

Quark theory predicts six different types of baryons with one bottom quark and spin J=3/2 (see graphic). The CDF experiment now accounts for two of these baryons.

CDF is an international experiment of 700 physicists from 61 institutions and 13 countries. It is supported by the Department of Energy, the National Science Foundation, and a number of international funding agencies. (The full list can be found at http://www-cdf.fnal.gov/collab.....cies.html.) Using the Tevatron, the CDF and DZero collaborations at Fermilab discovered the top quark, the final and most massive quark, in 1995.

Fermilab is a national laboratory funded by the Office of Science of the U.S. Department of Energy, operated under contract by Universities Research Association, Inc.
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PostPosted: Wed Dec 06, 2006 7:34 pm    Post subject: Long the Fixation of Physicists Worldwide, a Tiny Particle I Reply with quote

Long the Fixation of Physicists Worldwide, a Tiny Particle Is Found
University of Buffalo
6 December 2006


Buffalo, N.Y. -- After decades of intensive effort by both experimental and theoretical physicists worldwide, a tiny particle with no charge, a very low mass and a lifetime much shorter than a nanosecond, dubbed the "axion," has now been detected by the University at Buffalo physicist who first suggested its existence in a little-read paper as early as 1974.

The finding caps nearly three decades of research both by Piyare Jain, Ph.D., UB professor emeritus in the Department of Physics and lead investigator on the research, who works independently -- an anomaly in the field -- and by large groups of well-funded physicists who have, for three decades, unsuccessfully sought the recreation and detection of axions in the laboratory, using high-energy particle accelerators.

The paper, available online in the British Journal of Physics G: Nuclear and Particle Physics at http://www.iop.org/EJ/abstract/0954-3899/34/1/009, will be published in the January 2007 issue.

Results first were presented during a two-day symposium held in October at UB that celebrated Jain's 50-year career in the physics department in the College of Arts and Sciences.

During that symposium, the world-renowned and Nobel Prize-winning scientists in attendance expressed astonishment and delight that the axion finally might have been found.

The axion has been seen as critical to the Standard Model of Physics and is believed to be a component of much of the dark matter in the universe.

"These results show that we have detected axions, part of a family of particles that likely also includes the very heavy Higgs-Boson particle, which at present is being sought after at different laboratories," said Jain.

The story of the search for the axion particle in high-energy physics -- not to be confused with the search by cosmologists and astrophysicists for axions produced by the sun -- reads almost like a novel, with veritable armies of physicists committing many years of research and passion to its discovery starting in the 1970s.

In 1977, theoretical physicists predicted that there should exist a particle with characteristics very similar to those described in Jain's papers; in that publication, the term "axion" was coined. After that theoretical work, there was a mushrooming of papers from both theoretical and experimental physicists all chasing the axion using low-, medium- and high-energy accelerator beams from different laboratories worldwide.

But when it proved to be too elusive, many in the physics community then abandoned the search in the 1990s, based on puzzling evidence that perhaps this tantalizing particle didn't exist after all. Some groups flatly denied its existence and began referring to it as a "phantom."

Jain's initial interest in the elusive particles originated with work he began publishing in 1974 in Physical Review Letters and other journals that demonstrated evidence for particles with very low mass and very short lifetimes during particle accelerator experiments he conducted at Fermilab and Brookhaven National Laboratory.

At the time, Jain's papers elicited little interest from other physicists.

"This particle was there in my original paper in 1974," he said. "The experiment gave a hint that these particles existed but did not generate sufficient statistics to prove it. I knew I had to wait until a heavy ion beam at very high energy was available at a new accelerator."

As recently as 1999, a project called the CERES experiment at CERN in Geneva again focused on attempting to detect the axion, but that project also was unsuccessful.

The problem, according to Jain, was with their detector, which was electronic, the standard used in high-energy physics experiments today.

"They didn't know how to handle the detector for short-lived particles," Jain said. "I knew that for this very short-lived particle -- 10 to the power minus 13 seconds -- the detector must be placed very near the interaction point where the collision between the projectile beam and the target takes place so that the produced particle doesn't run away too far; if it does, it will decay quickly and it will be completely missed. That is what happened in most of the unsuccessful experiments."

Instead, Jain used a visual detector, made of three-dimensional photographic emulsions, which act as both target and detector and that therefore can detect very short-lived particles, such as the axion. However, use of such a detector is so specialized that to be successful, it requires intensive training and experience.

In the 1950s, Jain was trained to use this type of detector by its developer, the Nobel laureate, British physicist Cecil F. Powell. Jain has used it throughout his career to successfully detect other exotic phenomena, such as the charm particle, the anomalon, the quark-gluon plasma and the nuclear collective flow. In Jain's successful experiment, the axions were produced under extreme conditions of high temperature and high pressure, using a heavy ion lead beam with a total energy of 25 trillion electron volts at CERN in Geneva.

His experiments generated 1,220 electron pairs with identified vertices, the origin of each pair. They peaked at a distance of just 200-300 microns from the interaction point where the collisions take place in the emulsion.

"Only at that very short distance did I find the peak signal of this very-low-mass, short-lived particle with a neutral charge," he said.

After they are produced, axions rapidly decay into two electron pairs, the electron and the positron, he explained.

"We identified each vertex for each electron pair and we would not accept any electron pair unless we knew its vertex," he said. "There was a congestion of all kinds of low mass particles, including axions, near the detector. The background has to be filtered out from this congestion in order to obtain the signal of the axion."

Jain's co-author on the paper is Gurmukh Singh, then a post-doctoral researcher at UB and now a visiting assistant professor in the Department of Computer and Information Sciences at the State University of New York at Fredonia.

During Jain's long and illustrious career at UB, he published 175 scientific papers on a wide variety of physics topics, ranging from cosmic ray research performed on balloon flights to National Institutes of Health-funded studies on bone tissue to find more effective cancer therapies.

"After half a century as a scientist at UB, I find that with the discovery of this axion, my mission is complete," he concluded.

The University at Buffalo is a premier research-intensive public university, the largest and most comprehensive campus in the State University of New York.
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PostPosted: Thu Dec 14, 2006 8:59 am    Post subject: UCR-led research team detects 'top quark' Reply with quote

University of California - Riverside
13 December 2006

UCR-led research team detects 'top quark,' a basic constituent of matter
Subatomic particle appeared without its antimatter partner, says physicist Ann Heinson, co-leader of of group of 50 scientists.


RIVERSIDE, Calif. – A group of 50 international physicists, led by UC Riverside’s Ann Heinson, has detected for the first time a subatomic particle, the top quark, produced without the simultaneous production of its antimatter partner – an extremely rare event. The discovery of the single top quark could help scientists better explain how the universe works and how objects acquire their mass, thereby assisting human understanding of the fundamental nature of the universe.

The heaviest known elementary particle, the top quark has the same mass as a gold atom and is one of the fundamental building blocks of nature. Understood to be an ingredient of the nuclear soup just after the Big Bang, today the top quark does not occur naturally but must be created experimentally in a high-energy particle accelerator, an instrument capable of recreating the conditions of the early universe.

“We’ve been looking for single top quarks for 12 years, and until now no one had seen them,” said Heinson, a research physicist in the Department of Physics and Astronomy. “The detection of single top quarks – we detected 62 in total – will allow us to study the properties of top quarks in ways not accessible before. We are now able to study how the top quark is produced and how it decays. Do these happen as theory says they should" Are new particles affecting what we see" We're now better positioned to answer such questions.”

The detection of the top quark on its own was the outcome of a time-consuming process involving hundreds of scientists who constitute the “DZero” collaboration, a team of experimenters studying the top quark in particle collisions.

For its part, Heinson’s team first collected data from collision experiments conducted between 2002 and 2005 at the Tevatron Collider, the world’s highest energy particle accelerator that is comprised of a four-mile long underground ring at the Department of Energy’s Fermi National Accelerator Laboratory in Batavia, Ill. The collisions recorded were those between protons and antiprotons (the antimatter counterparts of protons).

Next, Heinson and her colleagues analyzed the record of high-energy collisions using powerful computers that helped the researchers determine which types of particles resulted from the collisions.

When a proton smashes head-on into an antiproton at nearly the speed of light, the collision occasionally produces a top quark. This heavy, unstable particle exists, however, for only a tiny fraction of a second before it decays into lighter particles, thereby complicating its detection. Physicists therefore must look at the top quark's descendents to identify it.

“We detected the top quark using the electronic signature of its decay products,” said Heinson, the primary author of a research paper on the single top quark’s detection that her group will submit to Physical Review Letters. “We measured the position of charged particles using a silicon vertex detector, which is an instrument – first encountered by the particles after the collision – that can precisely reconstruct the trajectories of charged particles. Since theory predicts single top quark production, we knew what to look for. It was extremely difficult, however, to find.”

In the near future, Heinson’s team plans to analyze more data generated by the Tevatron and also work with a new particle accelerator – the Large Hadron Collider – being built on the outskirts of Geneva, Switzerland, and scheduled to begin operation at the end of 2007.


###
UCR’s Liang Li, a postdoctoral researcher, and Philip Perea, a graduate student, were among the 50 physicists who joined Heinson in the research. Major funding for the study was provided by the U.S. Department of Energy.

The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment of about 17,000 is projected to grow to 21,000 students by 2010. The campus is proposing a medical school and already has reached the heart of the Coachella Valley by way of the UCR Palm Desert Graduate Center. With an annual statewide economic impact of nearly $1 billion, UCR is actively shaping the region's future. To learn more, visit www.ucr.edu or call (951) UCR-NEWS.
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PostPosted: Sat Jan 20, 2007 8:30 am    Post subject: From Collision to Discovery Reply with quote

From Collision to Discovery
20 January 2007

See in this website how data from the Large Hadron Collider are transmitted and analyzed:

http://gridcafe.web.cern.ch/gr.....Cdata.html
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PostPosted: Fri Feb 16, 2007 7:48 am    Post subject: Nobel laureate Burton Richter to speak about future of parti Reply with quote

Stanford University
16 February 2007

Nobel laureate Burton Richter to speak about future of particle physics

Particle physics is about to transform our thinking once again. Experiments of the last 15 years suggest new forms of matter, new forces of nature and perhaps even new dimensions of space and time. Pinning down the new ideas will require more data from larger and more expensive machines-at a time when funding is more difficult than ever to secure.

"As Dickens wrote, it is the best of times and the worst of times," says Nobel laureate Burton Richter, the Paul Pigott Professor in the Physical Sciences, Emeritus, at the Stanford Linear Accelerator Center and a pioneer of the particle colliders that now dominate high-energy physics. "We are in the midst of a revolution in understanding, but accelerator facilities are shutting down before new ones can open, and there is great uncertainty about future funding."

On Feb. 16, at the annual meeting of the American Association for the Advancement of Science in San Francisco, Richter will speak about the future course for elementary particle physics. He will offer a short overview of current research and explain his view of the most important opportunities for the field today.

Over the last 15 years, physicists discovered that they understand much less of the universe than they thought. No longer do they believe that luminous matter alone fills up the vacuum of space. Instead, two mysterious substances-dark matter and dark energy-comprise 96 percent of the universe. Neutrinos, very light elementary particles that stream from the sun, change from one type of matter to another as they travel close to the speed of light. And the Standard Model-the theory once believed to describe all fundamental interactions-no longer describes all that we observe.

The next 15 years are likely to answer some questions and raise new ones, Richter says. Physicists hope to find what is beyond the Standard Model, what at least some of the dark matter is made of and what is driving the accelerating expansion of the universe. The next few years may even see an experimental test of theories that posit more dimensions than just three of space and one of time, including string theory.

Yet none of this can happen without new experiments and new machinery, Richter says. In choosing which experiments to fund, the particle physics community must make choices that will severely limit the pace of discovery in some areas.

"This is a time where we cannot afford the merely good, but must focus on the really important if we are to continue our quest to learn what the universe is made of and how it works," Richter says.

In the lecture, Richter will present his views on which experiments must be funded and which will have to wait. Specifically, he will discuss the Large Hadron Collider (LHC), the proposed International Linear Collider (ILC), the need for accelerator research and development, the Joint Dark Energy Mission (JDEM) and Large Synoptic Survey Telescope (LSST) astroparticle experiments, and the critical questions that must be addressed regarding neutrinos.

The experiments

The LHC, now under construction at the European Laboratory for Particle Physics (CERN), will begin colliding protons at the end of this year. Researchers hope this machine will finally reveal the Higgs boson, a particle theorized to give mass to matter. The LHC also may discover whether particles have supersymmetric partners and determine if extra dimensions exist, among other things.

If built, the ILC would offer a more detailed perspective of what the LHC finds. By colliding electrons and positrons at higher energies than ever before, the machine would allow physicists to see new particles in unprecedented detail. Experiments at the ILC also could help explain the dominance of matter over antimatter in the universe by exploring "charge-parity violation," an asymmetry between the behavior of matter and antimatter, and could identify the particles predicted by theories of supersymmetry and extra dimensions. If the LHC turns up nothing, however, it is unlikely that the ILC will get built, Richter says.

Searches for dark matter and dark energy underground, on the Earth's surface and in space also will be an essential element of progress, Richter says. This area includes JDEM, a space-based instrument to search for supernovae, and LSST, a ground-based telescope that will provide digital imaging of faint astronomical objects across the entire sky.

In the coming years, various neutrino experiments with reactors, accelerators and cosmic rays may even offer insight into charge-parity violation.

"There's a huge opportunity here," he says. "While we may not be able to do all of this as fast as we would like, we need to get the really important done even if it takes longer than we would wish. The results will tell us much more about the universe and how it works."

Also speaking at the session are Nobel laureate David Gross of the University of California-Santa Barbara (matter, space and time); Young-Kee Kim of the University of Chicago (today's particle physics frontier); Philip Bryant of CERN (the LHC); Albert De Roeck of CERN (the LHC); and Jonathan Bagger of Johns Hopkins University (the ILC).


###
News Service website:
http://www.stanford.edu/news/

Stanford Report (university newspaper):
http://news.stanford.edu

Most recent news releases from Stanford:
http://www.stanford.edu/dept/n.....eases.html

COMMENT:
Burton Richter, Stanford Linear Accelerator Center: (650) 926-2601

EDITORS NOTE:

The symposium will take place Friday, Feb. 16, from 1:45 p.m. to 4:45 p.m. at the Hilton San Francisco, 333 O'Farrell St., San Francisco, CA 94102, in Continental Ballroom 3. A photo of Richter is available on the web at http://newsphotos.stanford.edu/.

RELEVANT WEB URLS:

BURTON RICHTER'S FACULTY PROFILE
http://www.slac.stanford.edu/s.....chter.html

STANFORD LINEAR ACCELERATOR CENTER
http://slac.stanford.edu/

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE
http://www.aaas.org/

EMBARGOED FOR RELEASE until Friday, Feb. 16, at 1:45 p.m. Pacific Time
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PostPosted: Wed Apr 04, 2007 7:04 am    Post subject: Oops! Giant Particle Collider Magnet Self-Destructs Reply with quote

Oops! Giant Particle Collider Magnet Self-Destructs

By The Associated Press

posted: 03 April 2007
04:23 pm ET


GENEVA (AP)—A 43-foot-long magnet for the world's largest particle collider broke "with a loud bang and a cloud of dust'' during a high-pressure test, and officials said Tuesday they are working to find a replacement part.

The part that failed March 27 was in a super-cooled magnet designed to focus streams of protons so that they collide and allow scientists to study the results of the collision, giving them a better understanding of the makeup of matter, according to Fermilab, based in suburban Chicago, which has an accelerator of its own and is helping build one deep beneath the Swiss and French countryside outside Geneva.

Fermilab, which built the magnet for the 17-mile circular collider, said its teams, working with colleagues from the European Organization for Nuclear Research, have determined what caused the "serious failure'' and are working on a solution.

For the full article:

http://www.livescience.com/tec....._prob.html
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PostPosted: Wed Apr 11, 2007 1:13 pm    Post subject: Long-standing neutrino question resolved Reply with quote

Virginia Tech

Long-standing neutrino question resolved
Scientists at Virginia Tech to probe the mystery of sterile neutrinos even further

Blacksburg, Va., April 11, 2007 -- An announcement by scientists at the Department of Energy’s Fermilab today significantly clarifies the overall picture of how neutrinos behave.

The results of the so-named MiniBooNE project resolve questions raised by observations an earlier DOE experiment – Liquid Scintillator Neutrino Detector (LSND) - in the 1990s that appeared to contradict findings of other neutrino experiments worldwide. The announcement today significantly clarifies the overall picture of how neutrinos behave.

In addition, scientists at Virginia Tech have proposed a new experiment, known as LENS (Low Energy Neutrino Spectroscopy), which will push the search for sterile neutrinos well beyond the scope of the MiniBooNE project.

"The possibility of sterile-neutrino-induced oscillation observed by LSND now seems to be ruled out," said Virginia Tech College of Science physicist Jonathan Link, who, along with 77 scientists from 16 other universities around the world, was a member of the MiniBooNE collaboration. "But there may still be sterile neutrinos with somewhat different properties."

Since the LSND result, theorists have used sterile neutrinos to solve many problems in physics from supernova explosions to the mysterious dark matter that binds galaxies together. Virginia Tech’s LENS (full name here) project will push the search for mysterious sterile neutrinos even further.

Currently, three types or "flavors" of neutrinos are known to exist: electron neutrinos, muon neutrinos and tau neutrinos. In the last 10 years, several experiments—including the LSND collaboration—have shown that neutrinos can oscillate from one flavor to another and back. However, reconciling the LSND observations with the oscillation results of other neutrino experiments would have required the presence of a fourth, or "sterile" type of neutrino, with properties different from the three standard neutrinos. The existence of sterile neutrinos would throw serious doubt on the current structure of particle physics, known as the Standard Model of Particles and Forces. Because of the far-reaching consequences of this interpretation, the LSND findings cried out for independent verification.

The MiniBooNE experiment, approved in 1998, took data for the current analysis from 2002 until the end of 2005 using neutrinos produced by the Booster accelerator at the Fermilab. The experiment’s goal was either to confirm or to refute the startling observations reported by the LSND collaboration, thus answering a long-standing question that has troubled the neutrino physics community for more than a decade.

The MiniBooNE collaboration used a blind-experiment technique to ensure the credibility of their analysis and results. While collecting their neutrino data, the MiniBooNE collaboration did not permit themselves access to data in the region, or "box," where they would expect to see the same signature of oscillations as LSND. When the MiniBooNE collaboration opened the box and "unblinded" its data less than three weeks ago, the telltale oscillation signature was absent.

Simply put, neutrinos are particles that originate from the center of the sun. They are one of the fundamental particles of the universe but also one of the least understood. Neutrinos differ from electrons in that they do not carry an electric charge and can pass through great distances in matter without being affected by it.

Studying neutrinos helps scientists understand about the sun, stars, and even the deep core of the Earth. It also provides the capability to detect extremely small trace amounts of radioactivity contained in samples of material, resulting in applications for homeland security, microelectronics, and space science.

For its observations, MiniBooNE relied on a 250,000-gallon tank filled with ultra pure mineral oil, clearer than water from a faucet. A layer of 1280 light-sensitive photomultiplier tubes, mounted inside the tank, detects collisions between neutrinos made by the Booster accelerator and carbon nuclei of oil molecules. Since January 2006, the MiniBooNE experiment has been collecting data using beams of antineutrinos instead of neutrinos and expects further results from these new data.

###
The College of Science at Virginia Tech gives students a comprehensive foundation in the scientific method. Outstanding faculty members teach courses and conduct research in biology, chemistry, economics, geosciences, mathematics, physics, psychology, and statistics. The college is dedicated to fostering a research intensive environment and offers programs in many cutting edge areas, including those in nanotechnology, biological sciences, information theory and science, and supports the university’s research initiatives through the Institute for Critical Technologies and Applied Sciences, and the Institute for Biomedical and Public Health Sciences. The College of Science also houses programs in intellectual property law and pre-medicine.
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PostPosted: Wed Jun 06, 2007 1:56 pm    Post subject: Home Movies of Atomic Size Reply with quote

Home Movies of Atomic Size
Researchers Catch Motion of a Single Electron on Video

6 June 2007
Brown University

Using pulses of high-intensity sound, two Brown University physicists have succeeded in making a movie showing the motion of a single electron. Humphrey Maris, a physics professor at Brown University, and Wei Guo, a Brown doctoral student, were able to film the electron as it moved through a container of superfluid helium.

PROVIDENCE, R.I. [Brown University] — To observe the motion of an electron – an elementary particle with a mass that is one billionth of a billionth of a billionth of a gram – has been considered to be impossible. So when two Brown University physicists showed movies of electrons moving through liquid helium at the 2006 International Symposium on Quantum Fluids and Solids in Kyoto, they raised some eyebrows.

The images, which were published online on April 28, 2007, in the Journal of Low Temperature Physics, show scattered points of light moving down the screen – some in straight lines, some following a snakelike path. The Matrix it’s not. Still, the fact that they can be seen at all is astounding. “We were astonished when we first saw an electron moving across the screen,” said Humphrey Maris, a professor of physics at Brown University. “Once we had the idea, setting it up was surprisingly easy.”

For the full article:

http://www.brown.edu/Administr.....6-174.html
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PostPosted: Thu Jun 14, 2007 9:35 am    Post subject: Fermilab physicists discover "triple-scoop" baryon Reply with quote

Fermilab physicists discover "triple-scoop" baryon
Fermi laboratory
Three-quark particle contains one quark from each family.

Batavia, Ill. - Physicists of the DZero experiment at the Department of Energy's Fermi National Accelerator Laboratory have discovered a new heavy particle, the Ξb (pronounced "zigh sub b") baryon, with a mass of 5.774±0.019 GeV/c2, approximately six times the proton mass. The newly discovered electrically charged Ξb baryon, also known as the "cascade b," is made of a down, a strange and a bottom quark. It is the first observed baryon formed of quarks from all three families of matter. Its discovery and the measurement of its mass provide new understanding of how the strong nuclear force acts upon the quarks, the basic building blocks of matter.

The DZero experiment has reported the discovery of the cascade b baryon in a paper submitted to Physical Review Letters on June 12.

For the full article:

http://www.fnal.gov/pub/pressp.....aryon.html
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PostPosted: Fri Jun 15, 2007 12:57 pm    Post subject: Tech researchers help find new sub-atomic particle - shollis Reply with quote

Thursday, June 14, 2007
Louisiana Tech University

Tech researchers help find new sub-atomic particle - shollis

Six Louisiana Tech researchers in the physics department played a role in discovering a new sub-atomic particle whose existence was announced this week.

For the full article:


http://www.latech.edu/technews.....1181847357
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PostPosted: Thu Jul 05, 2007 12:05 pm    Post subject: UNH researchers prove existence of new type of electron wave Reply with quote

University of New Hampshire
4 July 2007

UNH researchers prove existence of new type of electron wave

DURHAM, N.H. – New research led by University of New Hampshire physicists has proved the existence of a new type of electron wave on metal surfaces: the acoustic surface plasmon, which will have implications for developments in nano-optics, high-temperature superconductors, and the fundamental understanding of chemical reactions on surfaces. The research, led by Bogdan Diaconescu and Karsten Pohl of UNH, is published in the July 5 issue of the journal “Nature.”

“The existence of this wave means that the electrons on the surfaces of copper, iron, beryllium and other metals behave like water on a lake’s surface,” says Diaconescu, a postdoctoral research associate in the Condensed Matter Group of the physics department at UNH. “When a stone is thrown into a lake, waves spread radially in all directions. A similar wave can be created by the electrons on a metal surface when they are disturbed, for instance, by light.”

Acoustic surface plasmons have long been predicted on merely theoretical grounds, their existence has been extraordinarily difficult to prove experimentally. “Just one year ago, another group of scientists concluded that these waves do not exist,” says Karsten Pohl, associate professor of physics at UNH. “These researchers have probably not been able to find the acoustic plasmon because the experiments require extreme precision and great patience. One attempt after the other did not show anything if, for example, the surface was not prepared well enough or the detectors were not adjusted precisely enough.”

The new experiment that found the acoustic surface plasmon used an extremely precise electron gun, which shoots slow electrons on a specially prepared surface of a beryllium crystal. When the electrons are reflected back from the electron lake on the surface of the metal, some of them loose an amount of energy that corresponds to the excitation of an acoustic plasmon wave. This energy loss could be measured with a detector that was placed in an ultra-high vacuum chamber, together with the beryllium sample. The energy loss is small but corresponds exactly to the theoretical prediction.

Research on metal surfaces is important for the development of new industrial catalysts and for the cleaning the exhaust of factories and cars. As the new plasmons are very likely to play a role in chemical reactions on metal surfaces, theoretical and experimental research will have to take them into account as a new phenomenon in the future. In addition, there are several promising perspectives in nano-microscopy and optical signal processing when the new plasmons are excited directly with light diffracted off very small nano-features. The researchers estimate that, depending on their energy, the waves spread down to a few nanometers (one millionth of a millimeter), and die out after a few femtoseconds (one millionth of a billionth of a second) after they have been created, thus witnessing very fast chemical processes on atomic scale.

Another potential application is using the waves to carry optical signals along nanometer-wide channels for up to few micrometers and as such allowing the integration of optical signal propagation and processing devices on nanometer-length scales. And one of the most interesting but still very speculative applications of the plasmons relates to high temperature superconductivity. It is known today that the superconductivity happens in two-dimensional sheets in the material, which give rise to the special electron pairs which can move without resistance through the conductor. How this happens precisely is unclear but acoustic plasmons could be part of the explanation. If this is the case, it is a great advantage that it is now possible to study the plasmons on surfaces, where they is much easier to probe them than inside the material.


###
Diaconescu and Pohl received funding for this research from the National Science Foundation.
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PostPosted: Wed Jul 18, 2007 8:39 am    Post subject: New particle explains odd behavior in cuprate superconductor Reply with quote

University of Illinois at Urbana-Champaign
17 July 2007

New particle explains odd behavior in cuprate superconductors

CHAMPAIGN, Ill. -- New fundamental particles aren’t found only at Fermilab and at other particle accelerators. They also can be found hiding in plain pieces of ceramic, scientists at the University of Illinois report.

The newly formulated particle is a boson and has a charge of 2e, but does not consist of two electrons, the scientists say. The particle arises from the strong, repulsive interactions between electrons, and provides another piece of the high-temperature superconductivity puzzle.

Twenty-one years ago, superconductivity at high temperatures was discovered in copper-oxide ceramics (cuprates). Existing explanations of superconductivity proved inadequate because, unlike low-temperature superconductors, which are metals, the parent materials from which all high-temperature superconductors arise are insulators.

Now, a new theory suggests something has been overlooked. “Hidden in the copper-oxide materials is a new particle, a boson with a charge of 2e,” said Philip Phillips, a professor of physics at Illinois.

Surprisingly, this boson is not formed from the elementary excitations – that is, electrons and ions. Instead, the particle emerges as a remnant of the strong interactions between electrons in the normal state.

“High- and low-energy scales are inextricably coupled in the cuprates,” Phillips said. “Normally, when you remove a single electron from most systems, one empty state is created. In the cuprates, however, when you remove an electron, you create two empty states – both of which occur at low energy, but paradoxically, one of the states comes from the high-energy scale.”

Experimental evidence of this “one to two” phenomenon was first reported in 1990 and explained phenomenologically by University of Groningen physicist George A. Sawatzky (now at the University of British Columbia) and colleagues. What was missing was a low-energy theory that explained how a high-energy state could live at low energy.

Phillips, with physics professor Robert G. Leigh and graduate student Ting-Pong Choy, have constructed such a theory, and have shown that a charged 2e boson makes this all possible.

“When this 2e boson binds with a hole, the result is a new electronic state that has a charge of e,” Phillips said. “In this case, the electron is a combination of this new state and the standard, low-energy state. Electrons are not as simple as we thought.”

The new boson is an example of an emergent phenomenon – something that can’t be seen in any of the constituents, but is present as the constituents interact with one another.

By constructing a low-energy theory of the cuprates, the researchers have moved a step closer to unraveling the mystery of high-temperature superconductivity.

“Until we understand how these materials behave in their normal state, we cannot understand the mechanism behind their high-temperature superconductivity,” Phillips said.

###
Phillips, Leigh and Choy present their mathematical proof for the new boson in a paper accepted for publication in the journal Physical Review Letters. The National Science Foundation provided partial funding for this work.
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PostPosted: Mon Aug 20, 2007 3:26 pm    Post subject: Princeton scientists confirm long-held theory about source o Reply with quote

For immediate release: August 20, 2007
Princeton University

Princeton scientists confirm long-held theory about source of sunshine

Scientists are a step closer to understanding sunshine. A monumental experiment buried deep beneath the mountains of Italy has provided Princeton physicists with a clearer understanding of the sun's heart -- and of a mysterious class of subatomic particles born there.

The researchers, working as part of an international collaboration at the underground Gran Sasso National Laboratory near L'Aquila, Italy, have made the first real-time observation of low-energy solar neutrinos, which are fundamental particles created by nuclear reactions that stream in vast numbers from the sun's core.

"Our observations essentially confirm that we understand how the sun shines," said Frank Calaprice, a professor of physics and principal investigator of the Princeton team. "Physicists have had theories regarding the nuclear reactions within the sun for years, but direct observations have remained elusive. Now we understand these reactions much better."

The scientists' precise measurements of the neutrinos' energy provide long-sought proof of the theory regarding how these neutrinos are produced.

In stars the size of the sun, most solar energy is produced by a complex chain of nuclear reactions that converts hydrogen into helium. Beginning with protons from hydrogen's nucleus, the chain takes one of several routes that all end with the creation of a helium nucleus and the production of sunlight.

Steps along two of these routes require the presence of the element beryllium, and physicists have theorized that these steps are responsible for creating about 10 percent of the sun's neutrinos. But technological limitations had made the theory difficult to test until now.

The Gran Sasso lab's giant Borexino detector, located more than a kilometer below the Earth's surface, overcame these limitations, permitting the team to observe low-energy neutrinos, which interact extremely rarely with other forms of matter. Scientists have desired a way to detect them, because they emerge largely unchanged from their journey through the sun's interior to the Earth -- offering an unsullied glimpse into the processes that forged them. Most particles that emerge from the sun take so long to escape the interior that they change drastically before scientists can study them, so it has been difficult to prove how the sun creates energy. Neutrinos provide a key because they escape before they have time to change.

"The findings show that science's understanding of the chain of nuclear processes that make the sun shine is essentially correct, as least as far as the part of the chain that involves beryllium is concerned," Calaprice said. "The reaction does not generate a large percentage of the sun's energy, but confirming that we understand it makes us more certain that we know how the other processes that create sunlight work."

The results address other longstanding questions as well. The highly sensitive detector has confirmed theories regarding why previous experiments had found fewer solar neutrinos than expected at higher energies, a problem that stemmed from the particles' odd capacity to oscillate from one form to another as they travel through space. While the sun only produces electron neutrinos, these can change into tau or muon neutrinos, which have proved more difficult to detect.

Observing lower-energy neutrinos may also help physicists understand other predicted effects of neutrino oscillation that have not yet been tested.

"This experiment is an important step along the way toward understanding the details of neutrino physics using neutrinos from the sun," said physicist Morgan Wascko, co-spokesman for SciBooNE neutrino experiment at Fermi National Accelerator Laboratory. "Using these particles to observe the sun is important because they give us a lot of information about the way the universe functions, because it's full of stars."

The Borexino experiment's entire research team, which includes more than 100 scientists from many institutions worldwide, will publish its findings in an upcoming edition of the scientific journal Physics Letters B. Calaprice's Princeton colleagues include Cristiano Galbiati, assistant professor of physics, and Jay Benziger, professor of chemical engineering.

The experiment is funded by the National Science Foundation.

Abstract:
First real time detection of 7Be solar neutrinos by Borexino

This paper reports a direct measurement of the 7Be solar neutrino signal rate performed with the Borexino low background liquid scintillator detector. This is the first real-time spectral measurement of sub-MeV solar neutrinos. The result for 0.862 MeV 7Be is 47 ± 7stat ± 12sys counts/(day · 100 ton), consistent with predictions of Standard Solar Models and neutrino oscillations with LMA-MSW parameters.
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PostPosted: Tue Aug 21, 2007 1:03 pm    Post subject: Greatest Mysteries: Is There a Theory of Everything? Reply with quote

Greatest Mysteries: Is There a Theory of Everything?
By Dave Mosher, LiveScience Staff Writer

posted: 21 August 2007 07:37 am ET


Ancient philosophers thought wind, water, fire and earth were the most basic elements of the cosmos, but the study of the small has since grown up. Physicists continue to carve the known universe into particles to describe everything from magnetism to what atoms are made of and how they remain stable.

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http://www.livescience.com/str.....heory.html
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PostPosted: Sat Sep 15, 2007 9:00 am    Post subject: Alliance of Opposites: Electrons and positrons make new mole Reply with quote

Week of Sept. 15, 2007; Vol. 172, No. 11 , p. 163

Alliance of Opposites: Electrons and positrons make new molecule
Davide Castelvecchi

By soaking a silica sponge with antimatter, physicists have made the first matter-antimatter molecules. With further refinement, the technique might be used to briefly condense antimatter into fluid or solid states or even to create the first gamma-ray laser.

About 10 years ago, researchers created atoms of antihydrogen by combining antiprotons and positrons, the antimatter equivalents of protons and electrons. By itself, antihydrogen is as stable as hydrogen, though it's difficult to store in our matter world because of antimatter's propensity to vanish in a flash of gamma rays as soon as it comes into contact with matter.

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http://sciencenews.org/articles/20070915/fob1.asp
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PostPosted: Mon Sep 17, 2007 1:52 pm    Post subject: Research overturns accepted notion of neutron's electrical p Reply with quote

University of Washington
17 September 2007

Research overturns accepted notion of neutron's electrical properties

For two generations of physicists, it has been a standard belief that the neutron, an electrically neutral elementary particle and a primary component of an atom, actually carries a positive charge at its center and an offsetting negative charge at its outer edge.

The notion was first put forth in 1947 by Enrico Fermi, a Nobel laureate noted for his role in developing the first nuclear reactor. But new research by a University of Washington physicist shows the neutron's charge is not quite as simple as Fermi believed.

Using precise data recently gathered at three different laboratories and some new theoretical tools, Gerald A. Miller, a UW physics professor, has found that the neutron has a negative charge both in its inner core and its outer edge, with a positive charge sandwiched in between to make the particle electrically neutral.

"Nobody realized this was the case," Miller said. "It is significant because it is a clear fact of nature that we didn't know before. Now we know it."

The discovery changes scientific understanding of how neutrons interact with negatively charged electrons and positively charged protons. Specifically, it has implications for understanding the strong force, one of the four fundamental forces of nature (the others are the weak force, electromagnetism and gravity).

The strong force binds atomic nuclei together, which makes it possible for atoms, the building blocks of all matter, to assemble into molecules.

"We have to understand exactly how the strong force works, because it is the strongest force we know in the universe," Miller said.

The findings are based on data collected at the Thomas Jefferson National Accelerator Facility in Newport News, Va., the Bates Linear Accelerator at the Massachusetts Institute of Technology and the Mainz Microtron at Johannes Gutenberg University in Germany.

The three labs examine various aspects of the properties and behavior of subatomic particles, and Miller studied data they collected about neutrons. His analysis was published online Sept. 13 in Physical Review Letters. The work was funded in part by the U.S. Department of Energy.

Since the analysis is based on data gathered from direct observations, the picture could change even more as more data are collected, Miller said.

"A particle can be electrically neutral and still have properties related to charge. We've known for a long time that the neutron has those properties, but now we understand them more clearly," he said.

He noted that the most important aspect of the finding confirms that a neutron carries a negative charge at its outer edge, a key piece of Fermi's original idea.

The strong force that binds atomic nuclei is related to nuclear energy and nuclear weapons, and so it is possible the research could have practical applications in those areas.

It also could lend to greater understanding of the interactions that take place in our sun's nuclear furnace, and a greater understanding of the strong force in general, Miller said.

"We already know that without the strong force you wouldn't have atoms – or anything else that follows from atoms," he said.
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PostPosted: Sat Oct 27, 2007 6:25 am    Post subject: Big Machine Reveals Small Worlds Reply with quote

Big Machine Reveals Small Worlds
Emily Sohn


Oct. 24, 2007

Inside a shiny new machine in suburban Melbourne, Australia, tiny particles are whizzing around at nearly the speed of light.
The football-field–size machine, called a synchrotron, uses tubes, magnets, vacuum pumps, and other gadgetry to produce intensely powerful beams of light. The giant contraption looks like something out of a science fiction movie.

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http://www.sciencenewsforkids......ature1.asp
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PostPosted: Thu Nov 08, 2007 5:04 pm    Post subject: Smile, protons, you're on camera Reply with quote

Michigan State University

Smile, protons, you're on camera
8 November 2007

WARSAW, Poland -- Radioactivity, discovered more than 100 years ago and studied by physicists ever since, would seem to be a relatively closed subject in science. However, since the 1960s, the pursuit of at least one open question about how nuclei spontaneously eject various particles has continued to nag experimentalists, largely because of an inability to make precise measurements of fleeting, exotic nuclei.

In a paper published this week in Physical Review Letters, an international collaboration of researchers, led by Marek Pfutzner, a physicist from Warsaw University in Poland, takes several steps toward an answer. The scientists describe a first-ever success in peering closely at radioactive decay of a rare iron isotope at the ragged edge of the known nuclear map. The tools used to achieve this result include a novel combination of advanced physics equipment and imaging technology that is found in most off-the-shelf digital cameras.

"We have proved in a direct and clear way that this extremely neutron-deficient nucleus disintegrates by the simultaneous emission of two protons," write the authors.

Pfutzner and his collaborators set out to better understand an exotic form of radioactivity -- two-proton emissions from iron-45, a nucleus with 26 protons and 19 neutrons. The stable form of iron that is most abundant on Earth has 26 protons and 30 neutrons. One possibility was that the iron-45 isotope might occasionally release an energetically linked two-proton pair, known as a diproton. Other possibilities were that the protons, whether emitted in quick succession or simultaneously, were unlinked.

The research was performed at Michigan State University's National Superconducting Cyclotron Laboratory (NSCL), but the key device was a detector built by Pfutzner and his Warsaw University colleagues. Though nicknamed "the cannon" because of its vague resemblance to some sort of space age military device, the detector didn't shoot anything but rather was the target for the beam of rare isotopes produced at the NSCL Coupled Cyclotron Facility.

The detector included a front-end gas chamber that accepted and then slowed rare isotopes traveling at half the speed of light. The back-end imaging system, built around a high-end digital camera with standard charge-coupled device, or CCD, technology, recorded ghostly images of trajectories of emitted protons from the decaying iron-45 nuclei shot into the cannon's mouth.

Analysis of these images ruled out the theorized diproton emission and indicated that the observed correlations between emitted protons were best described by a form of nuclear transformation known as three-body decay. A theory of this process had previously been described by Leonid Grigorenko, a physicist at the Joint Institute for Nuclear Research in Dubna, Russia and a coauthor of the paper.

"There is amazing agreement between the experiment and Grigorenko's theory, which takes into account the complex interplay between emitted pairs of protons and the daughter nucleus," said Robert Grzywacz, a physicist at the University of Tennessee and Oak Ridge National Laboratory and a coauthor of the paper.

Besides shedding light on a novel form of radioactive decay, the technique also could lead to additional discoveries about fleeting, rare isotopes studied at accelerator facilities such as NSCL and Oak Ridge National Laboratory. These isotopes may hold the key to understanding processes inside neutron stars and determining the limits of nuclear existence.

The experiment itself also harkens back to the early days of experimental nuclear physics in which visual information served as the raw data. Before the days of cameras, this information was usually captured by scientists hunched over a microscope counting, for example, tiny flashes as alpha particles struck a zinc sulfide screen under the lens.

"It's perhaps the first time in modern nuclear physics that fundamentally new information about radioactive decay was captured in a picture taken by a digital camera," said Andreas Stolz, NSCL assistant professor and a coauthor on the paper. "Usually, in nuclear physics experiments you have digitized data and several channels of information from electronics equipment, but never images."


###
An audio interview with Stolz is available at: http://www.nscl.msu.edu/media/audio/stolz

Additional information:

Two proton Correlations in the decay of 45Fe: http://www.phys.utk.edu/expnuclear/2p_reshigh.html

This research was supported by the Polish Ministry of Science and Higher Education, the U.S. National Science Foundation and the U.S. Department of Energy.

NSCL is a world-leading laboratory for rare isotope research and nuclear science education.
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PostPosted: Sat Dec 08, 2007 7:46 am    Post subject: Muons Meet the Maya Reply with quote

Week of Dec. 8, 2007; Vol. 172, No. 23 , p. 360

Muons Meet the Maya
Physicists explore subatomic particle strategy for revealing archaeological secrets
Betsy Mason

At its most glamorous, the life of an experimental high-energy physicist consists of smashing obscure subatomic particles with futuristic-sounding names into each other to uncover truths about the universe—using science's biggest, most expensive toys in exciting locations such as Switzerland or Illinois. But it takes a decade or two to plan and build multibillion-dollar atom smashers. While waiting, what's a thrill-seeking physicist to do?

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http://sciencenews.org/articles/20071208/bob8.asp
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PostPosted: Wed Jan 09, 2008 11:58 am    Post subject: Proton-powered pooping Reply with quote

University of Utah
8 January 2008

Proton-powered pooping
Discovery: Subatomic protons act like nerve-signal transmitters


Muscles usually contract when a neurotransmitter molecule is released from nerve cells onto muscle cells. But University of Utah scientists discovered that bare subatomic protons can act like larger, more complex neurotransmitters, making gut muscles contract in tiny round worms so the worms can poop.

“There are relatively few molecules that serve as neurotransmitters to trigger electrical changes in cells. Protons are the only new members of this group in nearly 20 years,” says biology Professor Erik Jorgensen, scientific director of the Brain Institute at the University of Utah and senior author of the study in the Jan. 11 issue of the journal Cell.

While conventional neurotransmitters such as serotonin, dopamine and GABA are molecules made of many atoms, the new study revealed a surprise: Protons – which are single hydrogen atoms stripped of their electrons – are pumped out of a round worm’s gut by one kind of protein and then bind to receptor proteins on neighboring muscles, making the muscles contract so the worm defecates.

Not only did the researchers show protons can act like neurotransmitters, they identified the genes and proteins involved in the process in round worms, which are about 1 millimeter (a 25th of an inch) long and also are known as nematodes.

Previous research indicated the brains of humans and mice also have proton pumps and receptors to move protons between cells. The new study raises the possibility those protons may be transmitting nerve signals in the brain, says Jorgensen and study co-author Wayne Davis, a research assistant professor of biology.


“This is the first time we have found protons acting as transmitters,” Davis says. “It could be that these processes occur in humans. There are proton pumps present in intestinal cells and in the brain of humans and mice. Some of the pumps are thought to make acid for the gut to digest food. But why are proton pumps in the brain"”

Jorgensen adds: “Mice lacking the proton receptor cannot learn. It may be that the proton pump and receptor are required for learning,” and thus protons may act like neurotransmitters in the brain.

Utah graduate student Asim Beg (now at Columbia University) conducted the study with Jorgensen, Davis, graduate student Paola Nix and postdoctoral researcher Glen Ernstrom.

A Discovery from Constipated Worms

Atoms are made of nuclei that contain positively charged protons and uncharged neutrons, orbited by negatively charged electrons. So protons are among the smallest components of matter.


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The top diagram shows the cross-section of worm, including muscles that surround the intestine to help the worm defecate. The bottom diagram shows how protons act like neurotransmitters. The protons...

Click here for more information.
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Previously recognized neurotransmitters such as serotonin (known for its role in preventing depression) and dopamine (involved in addiction to cocaine and other drugs) are more than 100 times larger than protons. That makes protons “the world’s smallest transmitter,” says Jorgensen, also a Howard Hughes Medical Institute investigator.

Acids burn because they contain high concentrations of protons, which already were known to help the stomach digest food.

The new study shows that at least in some circumstances, protons also may be used by cells to communicate. “Normally you think of proton concentration increasing to digest food,” Davis says. “Now we see the cell is using these protons to communicate. The protons are acting like a word in a language that cells use to talk to each other.”

When the study began, nobody thought a new transmitter would be identified. Instead, the researchers were trying to understand how worms poop. Why" “Eating, moving, having sex and pooping are common things that all animals do,” says Davis.

Nematodes, or Caenorhabditis elegans, have about 1,000 cells and are simple animals studied by researchers worldwide. Nematodes have many of the same tissues – nerves, muscle and intestine – that are found in humans, and most of the same genes, making the worm a model for studying human biology.

Defecation in round worms is surprisingly complex. The animal has muscle contractions every 50 seconds that result in expulsion of intestinal contents. The 50-second cycle is an example of a biological clock, like those that regulate wake-sleep cycles and many other behaviors in animals.

“We were interested in teasing apart the components required for [defecation] clock function,” says Nix. “To do that we searched for mutations that affected the clock.”

By exposing worms to chemicals that altered their DNA, the researchers found mutant worms that couldn’t defecate or had trouble doing so. “The worms are constantly eating, so if they don’t poop regularly, they become very constipated,” says Nix.

In the round worm’s tail, muscles surround the tube-shaped intestine, and there is a fluid-filled space between the intestine and the surrounding muscles. The muscles contract to help the worm defecate. The researchers identified two different gene mutations that prevented such contractions.

Proteins and Protons Propel Pooping Process

One gene, named pbo-4 (for posterior body contraction), produces a protein that pumps protons out of the intestine, acting “like a revolving door where sodium is allowed in [the gut] while protons go out [of the gut] into the fluid-filled space that is very close to the surrounding muscle,” says Davis.

The second gene, pbo-5, makes a receptor protein on the muscles that surround the gut. After the protons are released from the intestine, they bind to the receptor protein.

“The receptor acts like an ear that allows the muscle to hear that protons are present,” says Beg. The receptor opens when the proton binds to it, forming a hole in the muscle cell that allows large numbers of ions like sodium to flow in. The ions make the muscle contract.

The researchers knew protons were being released from the gut because they could see their effects through a microscope.

They bred worms with a green fluorescent protein that loses it color when many protons are present. The adult worms had the green protein in the fluid-filled space between the intestine and the surrounding muscle – a space that Ernstrom says “is approximately 1,000 times smaller than the width of a hair.”

The scientists were able to show protons were pumped from the intestinal wall and to the surrounding muscle because, under a microscope, the fluid-filled space became less green. In mutant worms lacking the proton pump, the green remained unchanged, showing that protons were not released from the gut into the space.

In the next experiment, the researchers added protons to the fluid-filled space between the intestine and surrounding muscle in the mutants lacking the proton pump. The added protons made the muscle contract. That indicated protons indeed were acting like a neurotransmitter to carry the signal for contraction from the intestine to the surrounding muscle.

“To prove that it is the protons triggering the contraction, we want to supply the protons ourselves,” says Davis. “A fine needle filled with protons was used to inject protons in the space between the muscle and gut. We can bypass the gut and fool the muscle into thinking the gut is releasing protons, and the muscle contracts.”
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PostPosted: Sun Jun 29, 2008 5:07 am    Post subject: For Kids: IceCube Science Reply with quote

For Kids: IceCube Science
By Stephen Ornes
June 27th, 2008

To find some of the smallest things in the universe, scientists have to think big

Halzen has an unusual job. This scientist studies itsy bitsy, teeny tiny objects zipping through the universe. They’re called neutrinos.

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http://sciencenews.org/view/ge.....be_Science
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