118407947
Probing the Anomalous FCNC Interactions in Top-Higgs Final State and Charge Ratio Approach
We study the anomalous production of a single top quark in association with a Higgs boson at the LHC originating from flavor changing neutral current (FCNC) interactions in $tqg$ and $tqH$ vertices. We derive the discovery potentials and $68\%$ C.L. upper limits considering leptonic decay of the top quark and the Higgs boson decay into a $b\bar{b}$ pair with 10 fb$^{-1}$ integrated luminosity of data in proton-proton collisions at the center-of-mass energy of 14 TeV. We propose a charge ratio for the lepton in top quark decay in terms of lepton $p_{T}$ and $\eta$ as a strong tool to observe the signal. In particular, we show that the charge ratio increases significantly at large $p_{T}$ of the charged lepton. While the main background from $t\bar{t}$ is nearly charge symmetric and $W+jets$ background has much smaller charge ratio with respect to the signal. We show that this feature can also be used in the probe of anomalous single top production with a $Z-$boson or a photon which are under the attention of the experimental collaborations.
119292661
Impact of torsion space?time on $t\bar{t}$ observables at hadron colliders
Starting from the effective torsion space-time model, we study its effects on the top pair production cross section at hadron colliders. We also study the effect of this model on top pair asymmetries at the Tevatron and the LHC. We find that torsion space-time can explain forward-backward asymmetry according to measured anomaly at Tevatron. We find an allowed region in the parameters space which
14038525
Heavy Charged Gauge Bosons with General CP Violating Couplings
Heavy gauge bosons such as W' are expected to exist in many extensions of the Standard Model. In this paper, the most general Lagrangian for the interaction of W' with top and bottom quarks is considered. This Lagrangian consists of V–A and V+A structure with in general complex couplings. Such interactions produce an Electric Dipole Moment (EDM) for the top quark at one loop level. We predict the allowed ranges for the mass and couplings of W' by using the upper limit on the top quark EDM.
118539892
PROBING THE ANOMALOUS COUPLINGS OF THE TOP QUARK WITH GLUON AT THE LHC AND TEVATRON
In this paper, we study the sensitivity of the fraction of events arising from gluon–gluon fusion to the chromoelectric and chromomagnetic dipole moments (CEDM and CMDM) as well as the total and differential cross-sections at the LHC and Tevatron. The sensitivity of measured charged asymmetry at the LHC to CEDM and CMDM is also studied. We find that at the Tevatron and the LHC, nonzero values of CMDM could suppress the production rate. It is shown that the ratio of at the Tevatron is more sensitive to CEDM and CMDM than the LHC case. The presence of CEDM always increases the contribution of gluon–gluon fusion process in top pair rate at the Tevatron and LHC. Except for a small range of CMDM, the presence of CEDM and CMDM can increase the fraction of gluon–gluon fusion at the Tevatron and LHC. The measured ratio of at the Tevatron is used to derive bounds on the chromoelectric and chromomagnetic dipole moments as well as the total and differential cross-sections at the LHC and Tevatron, and the measured charged asymmetry at the LHC. The combination of and σLHC provides stringent limits on CMDM and CEDM.
119119331
Probing of Wtb anomalous couplings via the tW channel of single top production
The potential of LHC for investigation of the W-t-b vertex through the tW channel of single top quark production is studied. Unlike the other two single top quark production processes (t-channel and s-channel), the tW channel provides the possibility to study the Wtb vertex without receiving contamination from FCNC. This study has been done at parton level but is involved the separation of signal from backgrounds when both W-bosons decay to leptons. In this study is assumed to be conserved. The 68% C.L. bounds on the non-Standard Model couplings are estimated.
18095986
On the Charged Higgs Bosons Effects in the Top Quark Decays
The collider experiments at the Tevatron and the LHC provide us the possibility of probing the existence of a light charged Higgs boson. In this paper we study semi-leptonic decay of a polarized top quark via the charged Higgs boson ($t(\uparrow)\to H^{+}b \to l^{+}\nu_{l}b$). It is shown that the asymmetry or spin correlation coefficient of the charged lepton depends on the $\tan\beta$ and $M_{H^{\pm}}$ and is quite different from the Standard Model. This sensitivity of asymmetry to $\tan\beta$ and $M_{H^{\pm}}$ could be utilized in the experimental searches for the light charged Higgs for separation of the signal from backgrounds in the $t\bar{t}\to H^{+}W^{-}b\bar{b}\to\tau^{+}\nu_{\tau}\l^{-}\bar{\nu_{\l}}b\bar{b}$ (and vice versa). It might be useful for obtaining better bounds in the ($\tan\beta,M_{H^{\pm}}$) plane too.
119845469
Expectations for first single-top studies in CMS in proton-proton collisions
The first long physics run of LHC is taking place at a center-of-mass energy of 7 TeV, and is expected to continue until an integrated luminosity of 1 inverse femtobarn will have been collected. We present an analysis technique to measure the t-channel cross section for single top-quark production in CMS, that can confirm the recent observation of single-top quark production by the Tevatron experiments. Events leading to a signature of exactly one muon and two jets are selected and specific data-driven methods have been developed to reduce the sensitivity to the unknown level of background contamination. Single top quarks provide the possibility to study the polarization of an "isolated quark". This feature is exploited in the presented analysis for the measurement of SM-like single top; with more statistics, the chiral structure of the W-t-b vertex could be probed via the study of the top polarization and any sizable deviation from the Standard Model expectation would be a hint to new physics beyond the Standard Model.
12635873
Single Top production at LHC
The Production of single top quarks at LHC provides an ideal framework to investigate the properties of electroweak interaction, in particular of the {\it tWb} coupling. Moreover, single top is a powerful mean to identify physics beyond the standard model. All three different production mechanisms of single top are expected to be observed at LHC. Recent studies from ATLAS and CMS are presented.