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Register a new userA search for top decay into tau, neutrino and quark in top-antitop production
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The CDF Collaboration
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We present a search for top-antitop events with a tau lepton in the final state. The data sample corresponds to an integrated luminosity of 194/pb collected with the CDF II detector from proton-antiproton collisions at a center of mass energy of 1.96 TeV. We observe two events with an expected signal of 1.0+/-0.2 events and a background of 1.3+/-0.3 events. We determine a 95% confidence level upper limit on r_tau, the ratio of the measured rate of top->tau nu quark to the expectation, of 5.2.
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In this report a new search for a narrow-width heavy resonance decaying into top quark pairs (X -> ttbar) in ppbar collisions at sqrt(s)=1.96 TeV has been performed using data collected by the D0 detector at the Fermilab Tevatron collider. The analysis considers ttbar candidate events in the lepton+jets channel using a lifetime tag to identify b-jets and the ttbar invariant mass distribution to search for evidence of resonant production. The analyzed dataset corresponds to an integrated luminosity of approximately 370 pb^-1. Since no evidence for a ttbar resonance X is found, upper limits on sigma(X) x B(X -> ttbar) for different hypothesized resonance masses using a Bayesian approach are set. Within a topcolor-assisted technicolor model, the existence of a leptophobic Z boson with M(Z) < 680 GeV and width Gamma(Z) = 0.012 M(Z) can be excluded at 95% C.L..
We present details of a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb.
We present a search for the pair production of scalar top quarks ($tilde{t}_{1}$), the lightest supersymmetric partners of the top quarks, in $pbar{p}$ collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of {7.3 $fb^{-1}$} collected with the dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a $b$ quark, a charged lepton, and a scalar neutrino ($tilde{ u}$). We investigate final states arising from $tilde{t}_{1} bar{tilde{t}_{1}} rightarrow bbar{b}mutau tilde{ u} tilde{ u}$ and $tilde{t}_{1} bar{tilde{t}_{1}} rightarrow bbar{b}tautau tilde{ u} tilde{ u}$. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the ($m_{tilde{t}_{1}}$,$m_{tilde{ u}}$) plane.
We review the current status of the cross sections measurement of the top-quark at the LHC and at the Tevatron. Total production cross sections, studies using single top quark events and differential $rm{t}bar{rm t}$ cross sections are discussed. The associated production of top quark pairs with photons, Z and W bosons, including $rm{t}bar{rm t}$Z and $rm{t}bar{rm t}$W measurements shown for the first time at LHCP2014, are presented.
Top quark flavor changing neutral current (FCNC) interactions are highly suppressed in the Standard Model. Therefore, any large signal of FCNCs will indicate the existence of new interactions. In this paper, searches for FCNC interactions in top quark production and decay at the Tevatron and LHC are presented. FCNC searches in $trightarrow qZ$ and $trightarrow Hq$ decays, and in top quark production in $pprightarrow t+j$, $pprightarrow t+Z$ are summarized. Effect of top quark FCNCs on single top quark cross-section, and the searches for same-sign top quark pair production through FCNCs are also described. None of the searches yielded positive results and exclusion limits on branching rations, coupling strengths and cross-sections are obtained. Future prospects of FCNC searches are also briefly discussed.
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