Search for anomalous Wtb couplings and flavour-changing neutral currents in t-channel single top quark production in pp collisions at √s=7 and 8 TeV

• Main Authors: Khachatryan, V., Sirunyan, A. M., Tumasyan, A. R., Adam, Wolfgang, Asilar, Ece, Md. Ali, Mohd. Adli
• Format: Article
• Language: English; English
• Published: Springer Nature 2017
• Subjects: Q Science (General); QC Physics
• Online Access: http://irep.iium.edu.my/63059/1/63059_Search%20for%20anomalous%20Wtb%20couplings%20_article.pdf; http://irep.iium.edu.my/63059/2/63059_Search%20for%20anomalous%20Wtb%20couplings%20_scopus.pdf; http://irep.iium.edu.my/63059/; https://link.springer.com/content/pdf/10.1007%2FJHEP02%282017%29028.pdf

Single top quark events produced in the t channel are used to set limits on anomalous Wtb couplings and to search for top quark flavour-changing neutral current (FCNC) interactions. The data taken with the CMS detector at the LHC in proton-proton collisions at √ s = 7 and 8 TeV correspond to integrated luminosities of 5.0 and 19.7 fb−1 , respectively. The analysis is performed using events with one muon and two or three jets. A Bayesian neural network technique is used to discriminate between the signal and backgrounds, which are observed to be consistent with the standard model prediction. The 95% confidence level (CL) exclusion limits on anomalous right-handed vector, and left- and righthanded tensor Wtb couplings are measured to be |f R V | < 0.16, |f L T | < 0.057, and −0.049 < f R T < 0.048, respectively. For the FCNC couplings κtug and κtcg, the 95% CL upper limits on coupling strengths are |κtug|/Λ < 4.1 × 10−3 TeV−1 and |κtcg|/Λ < 1.8 × 10−2 TeV−1 , where Λ is the scale for new physics, and correspond to upper limits on the branching fractions of 2.0 × 10−5 and 4.1 × 10−4 for the decays t → ug and t → cg, respectively.