Measurement of Top-Quark Polarization in t-channel Single-Top Production

Abstract

The measurement of the top quark polarization, sensitive to the electroweak coupling structure, in t-channel single-top production is presented. Events are analyzed corresponding to an integrated luminosity of approximately $20\mathrm{f}{\mathrm{b}}^{-1}$ recorded with the CMS detector during pp collisions at $\sqrt{s}=8\mathrm{TeV}$. By requiring one isolated lepton (muon or electron), two jets, and missing transverse energy, an angular asymmetry, sensitive to the polarization of the top quark, is reconstructed in the top-quark rest frame. The corresponding angular asymmetry at parton level is inferred from data in a phase space with enhanced single-top t-channel candidates through unfolding. Remaining background contributions are estimated through a ML-fit and subtracted. A polarization of $P_t=0.82\pm 0.12(stat.)\pm 0.32(syst.)$ is measured assuming a spin-analyzing power of the charged lepton stemming from the top decay of $100\%$.

Presented at 7th International Workshop on Top Quark Physics 2014, 4 pages, 3 figures

Cited by in corpus (3)

• Polarization of top quark as a probe of its chromomagnetic and chromoelectric couplings in $tW$ production at the Large Hadron Collider
• The Top Quark
• Single top measurements and the $|V_{\mathrm{tb}}|$ extraction at the LHC