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Topic: Top quark

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In the News (Tue 19 Mar 19)

Quarks are observed to occur only in combinations of two quarks (mesons), three quarks (baryons), and the recently discovered particles with five quarks (pentaquark).
Quarks undergo transformations by the exchange of W bosons, and those transformations determine the rate and nature of the decay of hadrons by the weak interaction.
Convincing evidence for the observation of the top quark was reported by Fermilab 's Tevatron facility in April 1995.
hyperphysics.phy-astr.gsu.edu /hbase/particles/quark.html   (1357 words)

 Vertices Fall94: Top Quark
The top quark, for which experimenters have been searching for 17 years, is a subatomic particle whose existence is necessary to corroborate a theory that seeks to explain how matter and energy interact at the most basic, subatomic level.
The top quark, sometimes called "truth," is one of six different types or "flavors" of quarks, which are subatomic particles that serve as the basic building blocks for hadrons, which encompass all particles that interact by means of the strong nuclear force.
If quarks and leptons prove to be truly elementary, then the discovery of the top quark (when and if its existence is finally confirmed) will represent the culmination of a 2400-year-old struggle to identify the fundamental building blocks of matter.
www.duke.edu /vertices/update/fall94/quark.html   (2931 words)

 The Top Quark's Discovery
It took this long because the top quark was much more massive than was originally imagined, so it required a more powerful accelerator to create it.
Although the top quark decays too fast to be observed, it does leave behind particles that give evidence of its existence - a top quark "signature".
Since a top quark appears only once in several billion collisions, it was necessary to perform trillions of collisions.
www.particleadventure.org /frameless/topquark.html   (169 words)

 9 September 2004 - Fermilab: Why We Care About the Top Quark: CDF Explains
Top quarks and their antimatter partners, antitop quarks, are predominately produced in pairs from high-energy proton-antiproton collisions.
Because the top decays so quickly, the helicity of emitted W bosons, which is related to the boson's internal angular momentum, carries essential information about the top quark's fundamental interactions.
Research on the top quark is proceeding at Fermilab in tandem with preparations for the next collider on the frontier of particle physics--the Large Hadron Collider at CERN in Geneva, Switzerland.
www.interactions.org /cms/?pid=1014993   (1335 words)

 Quark Top
Ci è voluto molto tempo, perché il quark top era molto più massivo di quanto si prevedesse originariamente, e perciò occorreva un acceleratore molto più potente per riuscire a crearlo.
Anche se il quark top decade troppo velocemente per poter essere osservato, si lascia dietro delle particelle che permettono di identificare la sua esistenza -- una specie di "firma".
Dato che un quark top appare solo una volta su vari miliardi di collisioni, è stato necessario realizzare milioni di miliardi di collisioni.
www.infn.it /multimedia/particle/paitaliano/top_quark.html   (232 words)

 Physics News Update Number 216 - THE TOP QUARK AT LAST!
Establishing a mass for the top quark and a cross section for producing tops in proton- antiproton collisions are also important.
Put another way, the overall possibility of the observed top quark events being purely due to some background phenomenon is less than one part in a million for both experiments.
Quarks have hitherto never been seen in isolation; instead they always are seen in clumps of two (particles called mesons) or three (baryons).
www.aip.org /pnu/1995/split/pnu216-1.htm   (543 words)

 Inquiring Minds
Physicists at the Department of Energy's Fermi National Accelerator Laboratory announced on March 2, 1995 the discovery of a subatomic particle called the top quark, the last undiscovered particle of the six-member quark family predicted by current scientific theory.
Scientists worldwide had sought the top quark since the discovery of the bottom quark at Fermilab in 1977.
The top quark is one of the building blocks of nature.
www.fnal.gov /pub/inquiring/physics/discoveries/top_quark.html   (204 words)

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 Measurement of the Top Quark Cross Section
From the theory we expect top quarks to be produced predominately in pairs, and that each top quark will decay into the lighter mass b quark and a W boson (a carrier of the weak force).
The mass of the top quark is the topic of a jointly submitted publication.
Studies of the top quark will be a "top" priority, and with our cross section measurement in hand we can now reliably estimate that we will have tens of times more statistics in our data sample enabling precision study of this heavyweight member of the quark family.
www-d0.fnal.gov /public/pubs/topxsec_prl_sum.html   (1018 words)

 The Top Quark
The top quark is the sixth, and according to the Standard Model, the last to be found.
During the discovery of the top quark, the Fermilab accelerator, called the Tevatron, collided 900 GeV protons and 900 GeV anti-protons (1 GeV is the kinetic energy that a 1 billion volt battery could give to 1 proton), allowing the creation of top quarks.
Since the top quark mass is not predicted by the Standard Model (actually the SM doesn't predict any particle mass), the theory allows prediction of the cross section in terms of the top quark's mass.
conferences.fnal.gov /lp2003/forthepublic/topquark   (1570 words)

 A. Gray's Web Page: Top Quark
It is expected that the Top quark has more mass than the Higgs boson, which is predicted by both the standard model and the minimal supersymmetric model, but has not yet been discovered.
The precision with which the the Top quark is measured determines how well the Higgs mass can be predicted; given good predicted mass for the Higgs boson, experimenters "would know its cross-section and how it would decay, allowing their searches...
Measurement of the Top Quark Mass with In Situ Determination of the Jet Energy Scale (April 2005), Arguin, Jean-Francois, et al.
students.washington.edu /graya/TopHistory.html   (714 words)

 symmetry - June/July 2007 - Secrets of a Heavyweight
In fact, the top is so heavy–about 40 times more massive than its cousin, the bottom quark–that some people wonder whether it also plays a role in giving other particles their mass, another intriguing question to explore.
As more and more particle accelerators came up short in their efforts to produce the elusive top quark, it became clear that the top was much heavier than anticipated and would require much more energetic collisions to force it out into the open.
By examining this deluge of top quarks in detail, scientists hope to learn why the top quark is so heavy and how its properties are tied to the breaking of one of the fundamental symmetries of particle theory, thereby giving some mass to elementary particles.
www.symmetrymagazine.org /cms/?pid=1000496   (1755 words)

 UCR-led research team detects 'top quark,' a basic constituent of matter
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.
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.
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.
www.eurekalert.org /pub_releases/2006-12/uoc--urt121306.php   (696 words)

 DZero: Elusive Top Quark Discovery
The top quark was the 16th particle to be discovered, and it also proved to be the most elusive.
Part of a family of quarks that are believed to form the nuclei of atoms, the top quark was identified by measurements of particles produced by its decay.
The top quark mass is 40 times greater than the next heaviest quark and equal to the mass of a gold atom, which is made up of many particles and has a complex structure.
www.physorg.com /news7306.html   (1220 words)

 Science: Will Americans be first to catch the top quark? - 23 June 1990 - New Scientist
This particle is neither a quark nor a lepton but is the neutral carrier of the weak force, with a mass corresponding to 91 gigaelectronvolts (GeV), that is, nearly 100 times the mass of the proton.
One way in which the top quark's mass can influence results at lower energies is through the effect of 'radiative corrections' to the electroweak sector of the standard model.
If that fails to reveal the top quark, then there is hope that a new linear accelerator, which forms the initial stage in the acceleration cycle, might do the trick by 1993.
www.newscientist.com /article.ns?id=mg12617223.400   (1374 words)

The top quark is the heaviest of the six quarks, with a mass of about 175 GeV, the same as that of a gold nucleus.
At the Tevatron the top quark is produced mostly as t-tbar pairs.
The mass of the associated Higgs particle depends most sensitively on the top (and the W) mass, and therefore it is important to pin down the top mass as accurately as possible.
myweb.cebridge.net /hem/hem/topquark.htm   (296 words)

 Discovery of the Top Quark
Ever since the existence of the bottom (or ;) quark was inferred from the discovery of the Upsilon family of resonances at Fermilab in 1977, particle physicists have been on the lookout for its partner, called top (or t ).
Top is the last of the fundamental constituents of subnuclear matter that theories of the strong, weak, and electromagnetic interactions and a wealth of experimental information had led particle physicists to expect.
Because of the great mass and short lifetime, it is popular to say that top quarks were produced in great numbers in the fiery cauldron of the Big Bang, that they disintegrated in the merest fraction of a second, and then vanished from the scene until physicists learned to create them in the Tevatron.
lutece.fnal.gov /Papers/PhysNews95.html   (1142 words)

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