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Blobrana


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RE: Top Quark
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Asymmetric quarks defy standard model of physics

Newly released observations of the top quark - the heaviest of all known fundamental particles - could topple the standard model of particle physics. Data from collisions at the Tevatron particle accelerator at Fermilab in Batavia, Illinois, hint that some of the top quark's interactions are governed by an as-yet unknown force, communicated by a hypothetical particle called the top gluon. The standard model does not allow for such a force or particle.
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Blobrana


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The Tevatron was (until the start of LHC operation at CERN in 2009) the only hadron collider powerful enough to produce top quarks. In order to be able to confirm a future discovery, a second detector, the DO detector, was added to the complex (in addition to the Collider Detector at Fermilab (CDF) already present). In October 1992, the two groups found their first hint of the top, with a single creation event that appeared to contain the top. In the following years more evidence was collected and on April 22, 1994, the CDF group submitted their paper presenting tentative evidence for the existence of a top quark with a mass of about 175 GeV/c2.
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Blobrana


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Title: T-Quarks at the Large Hadron Collider: 2010-12
Authors: Maxim Perelstein, Jing Shao

We study the potential of the current Large Hadron Collider (LHC) 7 TeV run to search for heavy, coloured vector-like fermions, which are assumed to carry a conserved Z2 quantum number forcing them to be pair-produced. Each fermion is assumed to decay directly into a Standard Model quark and an invisible stable particle. T-odd quarks (T-quarks) and the lightest T-odd particle (LTP) of the Littlest Higgs model with T-parity provide an example of this setup. We estimate the bounds based on the published CMS search for events with jets and missing transverse energy in the 35 pb-1 data set collected in the 2010 run. We find that T-quark masses below about 450 GeV are ruled out for the LTP mass about 100 GeV. This bound is somewhat stronger than the published Tevatron constraint. We also estimate the reach with higher integrated luminosities expected in the 2011-12 run. If no deviation from the SM is observed, we expect that a bound on the T-quark mass of about 650 GeV, for the LTP mass of 300 GeV and below, can be achieved with 1 fb-1 of data. We comment on the possibility of using initial-state radiation jets to constrain the region with nearly-degenerate T-quark and LTP.

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Blobrana


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LHC closes in on massive particle

Physicists at the Large Hadron Collider (LHC) have seen several candidates for the heaviest sub-atomic particle known to science.
If the observations are confirmed, it would be a first for Europe; so far, the top quark particle has only been generated by one lab in the US.
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Blobrana


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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.

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