S-channel Single Top Quark Production Research Articles

The s-Channel Single Top Quark Production as a Constraint for W ' Boson Contribution

An analysis is performed to constrain the W' boson production using the measurement of the s‑channel single top quark production cross section. Both phenomenological and statistical approaches are examined and results are presented. In the best case, W' bosons that interact only to the right-handed fermions are excluded below 1390 GeV. To our knowledge, it is the first time that the measured cross section of the s-channel single top quark production from the colliders is used to rule out a part of the phase space of the W' boson.

S -channel single top quark production and decay at next-to-next-to-leading-order in QCD

We report on a fully differential next-to-next-to-leading order (NNLO) calculation of s-channel single top (anti-)quark production with a semi-leptonic decay at the LHC, neglecting the color correlation between the light and heavy quark lines and in the narrow width approximation. The NNLO corrections can increase the cross section by about 10% in the low transverse momentum region of the top quark and reduce scale variation uncertainty. In order to compare with experimental results without unfolding procedures, we also present theoretical predictions with fiducial cuts, including total cross sections and distributions of observables used in the experimental multivariate analysis. The NNLO corrections are found to be about -8% for fiducial cross sections.

Measurements of single top quark cross sections in pp collisions at 8 TeV with the CMS detector

Measurements are presented of the single top quark production in proton-proton collisions at the LHC at a centre-of-mass energy of 8 TeV, using data collected with the CMS experiment during 2012. The first analysis, in the t-channel single top production mode, considers decay channels where the W comes from the top decays into electron-neutrino or muon-neutrino. It makes use of a template fit exploiting the pseudorapidity distribution of the recoil jet and the reconstructed top quark mass, using background estimates determined from control samples in data. The measurement of top/antitop cross section ratio is also presented.The second analysis, measuring the associated production cross section of single top quark and W boson, considers final states in which the associated W boson, as well as the one originating from the top quark, decay leptonically. Multivariate methods are used to separate the signal from the topologically similar top pair production background. Multivariate techniques are also adopted in the search for s-channel single top quark production finally reported, in order to discriminate the very small signal from the huge background processes.

Single top quark production at CDF

We present the most recent CDF measurements of single top quark production in proton-antiproton collisions, performed using the lepton plus jets and missing transverse energy plus jets final states. We also present the simultaneous measurements of single top quark production in s-channel and t-channel separately. The extraction of the CKM matrix element |Vtb| from the single top quark cross section is discussed as well. A recent analysis aimed at identifying the s-channel single top quark production is described and the evidence for this process is presented.

Search for s-channel single top-quark production in pp collisions at 8 TeV with the CMS experiment at the LHC

A search for single top-quark production in the s channel in proton-proton collisions at a centre-of-mass energy of s=8 TeV by the CMS detector at the LHC is presented. Leptonic decay modes of the top quark with an electron or muon in the final state are considered. The signal is extracted by performing a maximum-likelihood fit to the distribution of a multivariate discriminant defined using Boosted Decision Trees to separate the expected signal contribution from the background processes. Data collected in 2012, corresponding to an integrated luminosity of 19.3/fb, lead to an upper limit on the cross section times branching ratio of 11.5 pb at 95% confidence level.

Search for s-channel single top-quark production in proton–proton collisions at [formula omitted] with the ATLAS detector

This Letter presents a search at the LHC for s-channel single top-quark production in proton–proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb−1. Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of σs=5.0±4.3 pb, consistent with the Standard Model expectation.

The impact of the Kaluza–Klein excited W boson on the single top at the LHC and comparison with other models

We study the s-channel single top quark production at the Large Hadron Collider (LHC) in the context of extra dimension theories, including the Kaluza–Klein (KK) decomposition. It is shown that the presence of the first KK excitation of the W gauge boson can reduce the total cross section of the s-channel single top production considerably if (3.5 TeV) for 7 TeV (14 TeV) in proton–proton collisions. Then the results will be compared with the impacts of other beyond standard model (SM) theories on the cross section of a single top s-channel. The possibility of distinguishing different models via their effects on the production cross section of the s-channel is discussed.

Factorization and resummation of s-channel single top quark production

In this paper we study the factorization and resummation of s-channel single top quark production in the Standard Model at both the Tevatron and the LHC. We show that the production cross section in the threshold limit can be factorized into a convolution of hard function, soft function and jet function via soft-collinear-effective-theory (SCET), and resummation can be performed using renormalization group equation in the momentum space resummation formalism. We find that in general, the resummation effects enhance the Next-to-Leading-Order (NLO) cross sections by about $3%-5%$ at both the Tevatron and the LHC, and significantly reduce the factorization scale dependence of the total cross section at the Tevatron, while at the LHC we find that the factorization scale dependence has not been improved, compared with the NLO results.

Next-to-next-to-leading logarithm resummation fors-channel single top quark production

I present the next-to-next-to-leading-logarithm (NNLL) resummation of soft and collinear gluon corrections to single top quark production in the s channel. Attaining NNLL accuracy involves the calculation of the two-loop soft anomalous dimension for the partonic subprocesses. Finite-order expansions of the resummed cross section are calculated through next-to-next-to-leading order (NNLO). Numerical results are presented for s-channel single top quark production at the Tevatron and the LHC, including the dependence of the cross sections on the top quark mass and the uncertainties in the theoretical prediction. The higher-order corrections are significant for energies at both colliders and they decrease the theoretical uncertainty.

SEARCH FOR SINGLE TOP QUARK PRODUCTION AT DØ

We present a review of searches for electroweak production of single top quarks at the Fermilab Tevatron proton–antiproton collider at [Formula: see text]. Searches for s-channel and t-channel single top quark production have been carried out using secondary-vertex b-quark tagging and advanced event analysis methods in order to maximize the sensitivity to single top quark production. So far, no evidence for a single top quark signal has been found. However, 95% confidence level upper limits on the production cross-section have been set that improve upon previous limits by factors of two to three and are approaching the cross-section region predicted by the standard model.

Next-to-leading order corrections to single top quark production and decay at the Fermilab Tevatron:s-channel process

We present a study of s-channel single top quark production at the upgraded Tevatron $p\bar{p}$ collider, including the next-to-leading order (NLO) QCD corrections to the production and the decay of the top quark. The "modified" narrow width approximation was adopted to preserve the spin of the top quark in its production and decay. We discuss the effect of the different $O(\alpha_s)$ contributions on the inclusive cross section as well as various kinematic distributions after imposing the relevant cuts to select s-channel single top signal events. In particular the $O(\alpha_s)$ decay contribution, while small in size, has a significant impact on several distributions. With the help of the best-jet algorithm to reconstruct the top quark we demonstrate that it is possible to study kinematical and spin correlations in s-channel single top events. We furthermore compare top quark spin measurements in two different basis and show how NLO corrections have to be taken into consideration in searches for the Higgs boson through $W^{\pm}H$ associated production at the Tevatron.

Search for electroweak single-top-quark production inpp¯collisions ats=1.96 TeV

We report on a search for Standard Model t-channel and s-channel single top quark production in ppbar collisions at a center of mass energy of 1.96 TeV. We use a data sample corresponding to 162 pb^{-1} recorded by the upgraded Collider Detector at Fermilab. We find no significant evidence for electroweak top quark production and set upper limits at the 95% confidence level on the production cross section, consistent with the Standard Model: 10.1 pb for the t-channel, 13.6 pb for the s-channel and 17.8 pb for the combined cross section of t- and s-channel.

The computer-based dynamic gait index: A multimedia approach to teaching functional rating scales

This Letter presents a search at the LHC for s-channel single top-quark production in proton–proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb−1. Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of σs=5.0±4.3pb, consistent with the Standard Model expectation.