592 research outputs found
Object ID performance for top physics at the ATLAS detector
No full textVarious objects that are important for top physics at ATLAS are described. These objects include, jets, electrons, muons, and taus. Reconstruction methods are described, as well as the calibrations of their energies, resolutions, and reconstruction efficiencies. Algorithms to identify -jets and their calibrations are also described
Common Objects and Backgrounds for Top at Atlas
No full textObjects tools and backgrounds that are common to most top analyses at Atlas are presented. Reconstruction, performance and calibration measurements are explained
Differential measurements at ATLAS
No full textAbstract from the EPS conference website: Measurements of the top quark production cross sections in proton proton collisions with the ATLAS detector at the Large Hadron Collider are presented. The main focus are measurements of differential spectra of ttbar final states, in particular, measurements that are able to constrain the modelling of additional parton radiation like the jet multiplicity distribution
Measurement of differential cross sections in top pair production in pp collisions with the ATLAS detector
No full textMeasurements of the differential spectra of ttbar pairs in sqrt s = 7 TeV collisions at the ATLAS experiment at the LHC are presented. In the decay channel where exactly one top quark decays to a prompt electron or muon, measurements are presented of the invariant mass of the ttbar system, the pT of the ttbar system, and the rapidity of the ttbar system. Additionally, measurements are presented of the multiplicity of extra jets that are radiated in association with the ttbar pair. Radiated jets are also studied in the channel where both top quarks decay to a prompt electron or a muon. In this case the flavour of the jets is studied using b-tagging, and the fraction of radiated jets that are heavy flavour (bottom or charm quark-initiated) is measured. In all cases the measurements are unfolded to particle or parton-level quantities and comparisons are made with various predictions from theory. A precise understanding of these distributions is necessary to constrain the backgrounds for many searches for new physics
Magazine Market Demand for the Factual Article
No full text These excerpts of case histories in fact writing are from Mr. Garberson's talk at the AASDJ-AATJ convention in Lexington, Ky., January 11. The author is connected with the Educational Services of the Saturday Evening Post. </jats:p
Generalization of exotic quark searches
No full textGeneral limits on exotic heavy quarks T, B, and X with masses above 300 GeV are presented for arbitrary branching fractions of T→W+b, T→Zt, T→Ht, B→W-t, B→Zb, B→Hb, and X→W+t. The results are based on a CMS search in final states with three isolated leptons (e or μ) or two isolated leptons with the same electric charge. Exotic heavy quark pair production through the strong interaction is considered. In the context of vectorlike quark models, T quarks with a mass mTWb, T=>Zt, T=>Ht, B=>Wt, B=>Zb, B=>Hb and X=>Wt. The results are based on a CMS search in final states with three isolated leptons (electron or muon) or two isolated leptons with the same electric charge. Exotic heavy quark pair production through the strong interaction is considered. In the context of vector-like quark models, T quarks with a mass mT < 480 GeV and mT < 550 GeV are excluded for weak isospin singlets and doublets, respectively, and B quarks with a mass mB < 480 GeV are excluded for singlets, all at 95% confidence level. Mass limits at 95% confidence level for T and B singlets, (T,B) doublets and (X,T) doublets are presented as a function of the corresponding heavy quark masses. For equal mass mT = mB and mX = mT vector-like quarks are excluded at 95% confidence level with masses below 550 GeV for T and B singlets, 640 GeV for a (T,B) doublet and 640 GeV for a (X,T) doublet
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Measurement of the Top Quark Mass using Quantities with Minimal Dependence on the Jet Energy Scale
No full textComparing the Health Workforce Provider Mix and the Distance Travelled for Mental Health Services by Rural and Urban Medicare Beneficiaries
No full textMeasurement of W-Boson Polarization in Top-Quark Decay in p(p)over-bar Collisions at root s=1.96 TeV
No full textWe report measurements of the polarization of W bosons from top-quark decays using 2.7 fb(-1) of p (p) over bar collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c(2), three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f(0)) and right-handed (f(0)) W bosons yields the model- independent results f(0) =0. 88 +/- 0.11(stat) +/- 0.06(syst) and f(+) = 0.15 +/- 0.07(stat) +/- 0.06(syst) with a correlation coefficient of -0.59. A measurement of f(0) [f(+)] constraining f(+) [f(0)] to its standard model value of 0.0 [0.7] yields f(0) 0.70 + 0.07(stat) +/- 0.04(syst) [f(+) - 0.01 +/- 0.02(stat) +/- 0.05(syst)]. All these results are consistent with standard model expectations. We achieve the single most precise measurements of f(0) for both the model- independent and modeldependent determinations
Measurement of ratios of fragmentation fractions for bottom hadrons in p(p)over-bar collisions at root s=1.96 TeV
No full textThis paper describes the first measurement of b-quark fragmentation fractions into bottom hadrons in Run II of the Tevatron Collider at Fermilab. The result is based on a 360 pb(-1) sample of data collected with the CDF II detector in p (p) over bar collisions at root s = 1.96 TeV. Semileptonic decays of (B) over bar (0), B-, and (B) over bar (0)(s) mesons, as well as Lambda(0)(b) baryons, are reconstructed. For an effective bottom hadron p(T) threshold of 7 GeV/c, the fragmentation fractions are measured to be f(u)/f(d)=1.054 +/- 0.018(stat)(-0.045)(+0.025)(sys)+/- 0.058(B), f(s)/(f(u)+f(d))=0.160 +/- 0.005(stat)(-0.010)(+0.011)(sys)(-0.034)(+0.057)(B), and f(Lambda b)/(f(u)+f(d))=0.281 +/- 0.012(stat)(-0.056)(+0.058)(sys)(-0.087)(+0.128)(B), where the uncertainty B is due to uncertainties on measured branching ratios. The value of f(s)/(f(u)+f(d)) agrees within one standard deviation with previous CDF measurements and the world average of this quantity, which is dominated by LEP measurements. However, the ratio f(Lambda b)/(f(u)+f(d)) is approximately twice the value previously measured at LEP. The approximately 2 sigma discrepancy is examined in terms of kinematic differences between the two production environments
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