Author: Publisher:
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Languages : de
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Book Description
Measurement of the asymmetry of b quark production in e+e- annihilation at √s
Author: Measurement of the Asymmetry of B Quark Production in E+e- Annihilation at [square Root of S]
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Author: TASSO CollaborationMeasurement of Forward-backward Charge Asymmetry in the Process of B-quark Production in E + E - Annihilation Around √s
Author: M. ShirakataMEASUREMENT OF FORWARD-BACKWARD CHARGE ASYMMETRY IN THE PROCESS OF B-QUARK PRODUCTION IN E+E- ANNIHILATION AROUND SQUARE ROOT OF S
Author: M. ShirakataA Measurement of the B-quark Forward-backward Charge Asymmetry in Electron-positron Annihilation at a Center-of-mass Energy of 58 GeV
Author: Timothy Lester ThomasPublisher:
ISBN:
Category :
Languages : en
Pages : 548
Book Description
Measurement of the C and B Quark Asymmetries in Electron Positron Annihilation
Author: T. J. GreenshawMeasurement of the Forward-backward Charge Asymmetry in Electron-positron Annihilation Into a Quark-antiquark Pair
Author: David Donald StuartFirst Measurement of the Forward-backward Asymmetry in Bottom-quark Pair Production at High Mass
Author: Publisher:
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Languages : en
Pages : 11
Book Description
We measure the particle-level forward-backward production asymmetry in $\mathrm{b\bar{b}}$ pairs with masses (m$\mathrm{b\bar{b}}$) larger than 150 GeV/c2, using events with hadronic jets and employing jet charge to distinguish b from $\bar{b}$. The measurement uses 9.5 fb-1 of $\mathrm{p\bar{p}}$ collisions at a center-of-mass energy of 1.96 TeV recorded by the CDF II detector. The asymmetry as a function of m$\mathrm{b\bar{b}}$ is consistent with zero, as well as with the predictions of the standard model. The measurement disfavors a simple model including an axigluon with a mass of 200 GeV/c2, whereas a model containing a heavier 345 GeV/c2 axigluon is not excluded.
Measurement of the Charge Asymmetry in Top Quark Pair Production in Pp Collisions at $\sqrt{s}$
Author: Publisher:
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Languages : en
Pages : 42
Book Description
The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 fb -1 were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is Ayc= [0.33_0.26 (stat)_0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.
Measurement of the Front Back Asymmetry in Top-antitop Quark Pairs Produced in Proton-antiproton Collisions at Center of Mass Energy
Author: Thomas A. SchwarzPublisher:
ISBN:
Category :
Languages : en
Pages : 110
Book Description
Quarks, along with leptons and force carrying particles, are predicted by the Standard Model to be the fundamental constituents of nature. In distinction from the leptons, the quarks interact strongly through the chromodynamic force and are bound together within the hadrons. The familiar proton and neutron are bound states of the light ''up'' and ''down'' quarks. The most massive quark by far, the ''top'' quark, was discovered by the CDF and D0 experiments in March, 1995. The new quark was observed in p{bar p} collisions at 1.8 TeV at the Fermilab Tevatron. The mass of the top quark was measured to be 176 {+-} 13 GeV/c{sup 2} and the cross section 6.8{sub -2.4}{sup +3.6} pb. It is the Q = 2/3, T{sub 3} = +1/2 member of the third generation weak-isospin doublet along with the bottom quark. The top quark is the final Standard Model quark to be discovered. Along with whatever is responsible for electroweak symmetry breaking, top quark physics is considered one of the least understood sectors of the Standard Model and represents a front line of our understanding of particle physics. Currently, the only direct measurements of top quark properties come from the CDF and D0 experiments observing p{bar p} collisions at the Tevatron. Top quark production at the Tevatron is almost exclusively by quark-antiquark annihilation, q{bar q} {yields} t{bar t} (85%), and gluon fusion, gg {yields} t{bar t} (15%), mediated by the strong force. The theoretical cross-section for this process is {sigma}{sub t{bar t}} = 6.7 {+-} 0.8 pb for m{sub t} = 175 GeV/c{sup 2}. Top quarks can also be produced at the Tevatron via q{bar b}{prime} {yields} tb and qg {yields} q{prime}tb through the weak interaction. The cross section for these processes is lower (3pb) and the signal is much more difficult to isolate as backgrounds are much higher. The top quark is predicted to decay almost exclusively into a W-boson and a bottom quark (t {yields} Wb). The total decay width t {yields} Wb is {Lambda} = 1.50 GeV. This corresponds to an incredibly short lifetime of 0.5 x 10{sup -24} seconds. This happens so quickly that hadronization and bound states do not take place, which leads to the interesting consequence that the top quark spin information is passed to the decay products.