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	Pentaquark - Wikipedia, the free encyclopedia
		A pentaquark is an hypothetical subatomic particle consisting of a group of five quarks (compared to three quarks in normal baryons and two in mesons), or more specifically four quarks and one anti-quark and is represented by Θ.
		The existence of pentaquarks was originally hypothesized by Maxim Polyakov, Dmitri Diakonov, and Victor Petrov at the Petersburg Nuclear Physics Institute in Russia in 1997, but their predictions were met with skepticism.
		Nevertheless, the existence of pentaquarks was first reported in July 2003 from experiments run at LEPS by Takashi Nakano of Osaka University, Japan, and by Stepan Stepanyan (for CLAS) at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Newport News, Virginia.
	en.wikipedia.org /wiki/Pentaquark (520 words)

	Physics News Graphics: Pentaquark
		A schematic drawing of how a pentaquark particle is created in high energy collisions at the SPring-8 accelerator in Japan and at the Jefferson Lab in the US.
		In some collisions, the debris particles will include a pentaquark (consisting of 2 up quarks, 2 down quarks, and a strange antiquark), a negative K meson (a strange quark and an up antiquark), and other particles.
		Studying the properties of the end-product neutrons and K+ mesons is what determines the existence of the pentaquark.
	www.aip.org /mgr/png/2003/193.htm (169 words)

	Do pentaquarks really exist? (February 2005) - Physics World - PhysicsWeb (Site not responding. Last check: 2007-11-01)
		Particle physicists think of the lifetime of a particle in terms of its "width", which is basically the spread in its rest energy or mass: the larger the width, the shorter the lifetime.
		It is perhaps this feature of pentaquarks that creates the most tantalizing challenge from the perspective of QCD: while it is possible to interpret the pentaquark as a combination of four quarks and an antiquark, the challenge is to explain why it survives of the order of 100 times longer than expected.
		Claims for the existence of pentaquarks have inspired intense studies of the theory and phenomenology of QCD in the so-called strong-interaction regime.
	physicsweb.org /articles/world/18/2/4 (1156 words)

	Turner
		A hedgehog is a small nocturnal insect-eating mammal with a spiny coat, able to roll itself into a ball for defense; it is also a whimsically named mathematical configuration in which fields point outward like the spines of a frightened hedgehog.
		Pentaquarks are supposed exotic particles composed of four quarks and an anti-quark (in contrast to usual particles such as protons or neutrons which are made of three quarks).
		The discovery of pentaquarks based on a wrong theory could be an example of serendipity in science---a surprisingly common occurrence in the history of science.
	www.physics.umd.edu /events/colloquia/Fall2005/cohen.htm (267 words)

	APS Division of Nuclear Physics - Current Research Topic
		From decuplets to anti-decuplets and quarks to pentaquarks
		In the fall of 2002, evidence for a narrow baryon state having an exotic strangeness quantum number, consistent with a pentaquark structure, was presented at the PANIC conference [1].
		The prediction of pentaquarks and subsequent experimental verification of their existence has renewed the interest in how quarks are bound inside hadrons.
	dnp.nscl.msu.edu /current/pentaquark.html (1365 words)

	The Interaction Point, May 6, 2005
		Pentaquarks are mysterious particles—whose existence is still in question—composed of four quarks and an antiquark.
		A meson (shown top) is composed of a quark and an antiquark, a regular baryon (center) consists of three quarks, and a pentaquark (bottom) is proposed to have four quarks and an antiquark.
		The smaller the sample, the easier it is to mistake a statistical fluctuation for a signal, or to accidentally include or exclude background events that affect the strength of the signal.
	www2.slac.stanford.edu /tip/2005/may6/pentaquarks.htm (848 words)

	Pentaquark Did You Mean pentaquark
		A pentaquark is a subatomic particle consisting of a group of five quarks (compared to three quarks in normal baryons and two in mesons), or more specifically four quarks and one anti-quark and is represented by ?.
		Nevertheless, the existence of pentaquarks was first reported in July 2003 from experiments run by Takashi Nakano of Osaka University, Japan, and by Ken Hicks at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Newport News, Virginia.
		It is worth noting that the experiments that fail to see the pentaquark are at higher energy where the meson exchange production mechanism dies out in favor of flavor neutral gluon exchange; the latter is doubly suppressed by the OZI rule.
	www.did-you-mean.com /Pentaquark.html (628 words)

	Multiquarks: Theory
		The resulting chiral multiplet structure recovers the ideally-mixed pentaquark mass spectrum of the diquark model, and interestingly, requires that the axial couplings of the pentaquarks to states outside the degenerate multiplets vanish in the chiral limit.
		The mass difference between the Theta^+ and the pentaquark with the quantum numbers of the nucleon amounts to 70 MeV and is consistent with the interpretation of the N(1440) as a pentaquark.
		First, the flavor wave functions of all the pentaquark baryons are constructed in SU(3) quark model and then the flavor SU(3) symmetry relations for the interactions of the pentaquarks with three-quark baryons and pentaquark baryons are obtained.
	fafnir.phyast.pitt.edu /exotica/bib/MultiTh.html (12619 words)

	Pentaquark discovery confounds sceptics - 02 July 2003 - New Scientist
		The pentaquark may have been common in the Universe just after the Big Bang, 14 billion years ago.
		They predicted that one particular pentaquark - containing two "up" quarks, two "down" quarks and an "anti-strange" quark - should be about 1.5 times as heavy as a proton.
		A team led by Takashi Nakano of Osaka University and another led by Ken Hicks at the Jefferson lab in Virginia made a high-energy gamma ray interact with a neutron to create a meson and a pentaquark.
	www.newscientist.com /news/news.jsp?id=ns99993903 (523 words)

	CERN Courier - The challenge of the pentaqu - IOP Publishing - article
		Volker Burkert reports on Pentaquark 2003, the first topical workshop on exotic baryons, which was held at Jefferson Lab in November.
		Within a chiral soliton model, they predicted an antidecuplet of 10 ground-state pentaquarks, three of which had exotic-flavour quantum numbers, meaning that their quantum numbers cannot be constructed from only three quarks.
		These data lend support to the symmetry properties of pentaquark states as predicted in the chiral soliton model, or in the quark-cluster picture.
	www.cerncourier.com /main/article/44/3/18 (1471 words)

	BBC NEWS \| Science/Nature \| Behold the pentaquark
		The new particle is the so-called pentaquark - five quarks in formation.
		In 2002, the first tentative evidence of the pentaquark was put forward at an international scientific conference in Japan.
		The discovery of the pentaquark, also known as a new exotic baryon state, should have far-reaching consequences for our theory of particle interactions that attempt to explain the structure of matter.
	news.bbc.co.uk /2/hi/science/nature/3034754.stm (401 words)

	Physics News Update
		The Jefferson Lab result was announced at the Conference on the Intersections of Nuclear and Particle Physics held on May 19-24, 2003, at New York City.
		Stepan Stepanyan (757-269-7196) reported at this meeting that the mass measured for the pentaquark, 1.543 GeV (with an uncertainty of 5 MeV), is very close to the LEPS value.
		The discovery of a 5-quark state should be of compelling interest to particle physicists, and this might be only the first of a family of such states.
	www.aip.org /enews/physnews/2003/split/644-1.html (698 words)

	The pentaquark: The strongest confirmation to date
		The team announced the initial discovery of a pentaquark on a proton target at an international physics conference in New York City in May 2003.
		According to CLAS researchers, further experimentation is needed to increase the pentaquark detection rate per particle explosion, to better understand the details of how the pentaquark is produced, and its internal characteristics.
		The Institute is especially well known for its success in the transfer of technology from the laboratory to the marketplace so that new discoveries and inventions benefit human life, protect the environment, and strengthen economic development.
	www.eurekalert.org /pub_releases/2004-01/rpi-tpt012304.php (670 words)

	Pentaquarks: HERA-B finds no evidence for the existence of pentaquarks, exotic bound states of four quarks and an ... (Site not responding. Last check: 2007-11-01)
		Pentaquarks: HERA-B finds no evidence for the existence of pentaquarks, exotic bound states of four quarks and an anti-quark
		In the year 2003 leading world scientific journals and daily newspapers reported on the experimental discovery of pentaquarks - exotic bound states of four quarks and an antiquark.
		In an analysis of about 200 million proton-nucleus collisions, the HERA-B collaboration, in which the Ljubljana team is an active member, set stringent upper limits on the probability for production of pentaquarks, putting their existence under question.
	www-f9.ijs.si /~zivko/pentakvark/pqintro.html (103 words)

	"Pentaquarks" by Edward Willett
		University of Saskatchewan particle physicist Chary Rangacharyulu has reached that pinnacle, as part of an international team that recently discovered the first known "pentaquark," a new sub-atomic particle that could change our understanding of physics and the very early universe.
		Russian theorists Maxim Polyakov, Dmitri Diakonov and Victor Petrov predicted in 1997 that a pentaquark containing two up quarks, two down quarks and an anti-strange quark should be about 1.5 times as heavy as a proton.
		But at the urging of the Russian theorists, in 2002 the team that Rangacharyulu is on, led by Takashi Nakano of Osaka University, took another look at results from a 2001 experiment in which they fired high-energy gamma rays at carbon atoms, using a synchrotron located at Japan’s SPring-8 physics lab.
	www.edwardwillett.com /Columns/pentaquarks.htm (802 words)

	BioEd Online: Doubt is cast on pentaquarks
		The pentaquark was discovered at the SPring-8 synchrotron in Harima, Japan.
		The particle, thought to be made up of five quarks, is so unstable that physicists inferred its existence from the debris of collisions between gamma rays and carbon atoms.
		The results fuel a controversy that has raged since the first pentaquark sighting was confirmed by more than ten other labs, which looked back through the results of similar collisions to search for evidence of the particle.
	www.bioedonline.org /news/news-print.cfm?art=1718 (586 words)

	pentaquarks Text - Physics Forums Library
		For example, the first observed (to be confirmed!) pentaquark is the Theta+.
		This particle has positive strangeness, therefore one is forced to introduce an anti-strange quark (strange antiquark) (you know what I mean, right?) in the valence structure.
		This in turn implies that this pentaquark is NOT just a regular 3-quark structure plus a vacuum fluctuation of meson orbiting around, but rather a resonant structure involving 5 quarks.
	www.physicsforums.com /archive/index.php/t-34637.html (483 words)

	Pentaquarks: HERA-B finds no evidence for the existence of pentaquarks, exotic bound states of four quarks and an ...
		Half of the 30 most cited publications in 2003 and 2004 are on the subject of exotic bound states of quarks.
		In particular, they were responsible for one of the essential components of the detector, the ring imaging Cherenkov counter (RICH).
		Pentaquarks should appear as high and narrow peaks at positions denoted with arrows in histograms a) and b).
	www-f9.ijs.si /~zivko/pentakvark/pqmain.html (780 words)

	PARTICLE PHYSICS: ON THE NON-EXISTENCE OF PENTAQUARKS
		Such a correlation was not possible within the simplest quark model, where most strongly interacting particles (known as hadrons) are either mesons, which contain a quark and an antiquark, or baryons, which comprise three quarks.
		The first pentaquark sighting was announced by them[2] in early 2003, exactly at the predicted mass and with a narrow width.
		There was some surprise that the first sighting of a particle with such a narrow width should have occurred in such a complex environment: the nuclear constituents are bound and have kinetic energy, which tends to smear any signals.
	scienceweek.com /2005/sw050617-2.htm (1753 words)

	NSDL Metadata Record -- $J^P={1/2}^-$ Pentaquarks in Jaffe and Wilczek's Diquark Model (Site not responding. Last check: 2007-11-01)
		If Jaffe and Wilczek's diquark picture for $\Theta_5$ pentaquark is correct, there should also exist a $SU_F$(3) pentaquark octet and singlet with no orbital excitation between the diquark pair, hence $J^P={1/2}^-$.
		These states are lighter than the $\Theta_5$ anti-decuplet and lie close to the orbitally excited (L=1) three-quark states in the conventional quark model.
		Among them two pentaquarks with nucleon quantum numbers may be narrow.
	nsdl.org /mr/1279149 (181 words)

	Ohio University Outlook (Site not responding. Last check: 2007-11-01)
		Hicks took part in the experiment to discover the pentaquarks and an effort to confirm the results at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility.
		Hicks and Carman, along with their colleagues, have been working at the Jefferson Laboratory to confirm the existence of pentaquarks since October.
		Discussions of pentaquarks, written for individuals of all levels of physics expertise, can be found on Hicks' Web site, www.phy.ohiou.edu/~hicks/thplus.html.
	www.ohiou.edu /outlook/7-23-03/pentaquark.htmlx (401 words)

	Pentaquark Pursuit: Five-Quark Particle Charms Physicists
		Crucially, Diakonov suggested a new method of data analysis that should, he thought, reveal the pentaquark’s presence.
		This can be attributed to a meson-baryon molecular resonance, or, much more exciting, an exotic five-quark baryon composed of two ups, one down, one strange, and one anti-down quark.
		The half-life of the pentaquark, essentially a fleeting fusion of a neutron and a K
	www.sciencewatch.com /july-aug2004/sw_july-aug2004_page6.htm (914 words)

	University of Michigan
		ANN ARBOR, Mich.—Evidence for the pentaquark has very recently been reported by experiments in Japan, Russia and the United States.
		The new particle's properties like mass, decay time and decay mode fit to theoretical predictions of a five-quark system, a pentaquark.
		This enhances the credibility of the existence of this new particle," said Wolfgang Lorenzon, who participated in a University of Michigan team that confirmed the existence of the new particle in the debris of high-energy collisions, together with a team led by Moskov Amarian from the German Zeuthen research group.
	www.umich.edu /news/index.html?Releases/2003/Jul03/r072203 (382 words)

	Redshifts and Pentaquarks
		In their efforts to unravel the secrets of matter, scientists have tried for three decades to come up with different combinations.
		Quarks come in six types, or "colours." The type of quarks inside protons and neutrons determines the mass, energy and magnetism of those particles.
		The pentaquark's stability likely comes from a unique combination of quarks, says physicist Peter Barnes of Los Alamos (NM) National Lab.
	www.flatrock.org.nz /topics/science/a_very_different_universe.htm (4270 words)

	Pentaquark 04: Proceedings of International Workshop, Spring-8, Japan, 20-23 July 2004
		Study of Narrow Baryonic Pentaquark Candidates with the ZEUS Detector at HERA
		Pentaquark with Diquark Correlations in a Quark Model
		Pentaquark Baryon from the QCD Sum Rule with the Ideal Mixing
	www.booksmatter.com /b9812563385.htm (499 words)

	APS - 2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan - Event - ... (Site not responding. Last check: 2007-11-01)
		The experiments have covered a wide range of beam energies, different types of beam particles, and target materials.
		The evidence that supports the discovery of pentaquarks has been challenged by experimental data in which there is no evidence for pentaquarks.
		It is in this context that recent results in the search for pentaquarks will be reviewed.
	meetings.aps.org /Meeting/HAW05/Event/33782 (139 words)

	Anuj Purwar: Free Coca Cola and Pentaquarks
		I won't even try to calculate how far this is from norm in terms of sigma, the favorite term that physicists like to use to determine the likelihood of a signal.
		But there are several experiments which show pentaquark results: effects of several sigmas even and then there are several experiments which published results indicating no pentaquarks.
		For instance with regard to pentaquarks, I know that my experiment PHENIX had "Seen" a pentaquark signal last year.
	qd.typepad.com /35/2005/09/free_coca_cola_.html (468 words)

	CERN Courier - Four labs find five-quark pa - IOP Publishing - article (Site not responding. Last check: 2007-11-01)
		in April this year, as suggested by Russian theorist Dmitri Diakonov, the exact nature of the so-called "pentaquark" is not yet clear.
		Further experiments should reveal whether it is a tightly bound five-quark object or a molecular meson-baryon state, and will provide measurements of its spin, and the angular distribution and energy dependence of its production.
		The most recent experimental evidence for the pentaquark comes from the SAPHIR collaboration at the Electron Stretcher Accelerator (ELSA) in Bonn, Germany.
	www.cerncourier.com /main/article/43/7/1 (733 words)

	RPI: News & Information - The Pentaquark: The Strongest Confirmation to Date
		Troy, N.Y. — An international team of physicists has provided the best evidence to date of the existence of a new form of atomic matter, dubbed the "pentaquark." The research team confirmed the existence of pentaquarks by using a different approach that greatly increased the rate of detection compared to previous experiments.
		The results are published as the cover story in today's issue of the journal Physical Review Letters.
		Why not change the world?(SM) is a service mark of Rensselaer Polytechnic Institute.
	news.rpi.edu /update.do?artcenterkey=52&setappvar=page(1) (726 words)

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