Measurement of the jet mass in highly boosted ${\mathrm{t}}\overline{\mathrm{t}}$ events from pp collisions at $\sqrt{s}=8$ $\,\text {TeV}$

• Main Author: CMS collaboration (2230 authors)
• Publication Date: 2017
• Other Authors: Nayak, Aruna, Bargassa, Pedrame, Beirão Da Cruz E Silva, Cristóvão, Calpas, Betty, Di Francesco, Agostino, Faccioli, Pietro, Ferreira Parracho, Pedro Guilherme, Gallinaro, Michele, Hollar, Jonathan, Leonardo, Nuno, Lloret Iglesias, Lara, Rodrigues Antunes, Joao, Seixas, Joao, Toldaiev, Oleksii, Vadruccio, Daniele, Varela, Joao, Vischia, Pietro, David Tinoco Mendes, Andre, Silva, Pedro, Musella, Pasquale, Pela, Joao
• Format: Article
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://dx.doi.org/10.1140/epjc/s10052-017-5030-3; http://hdl.handle.net/10400.26/27310

The first measurement of the jet mass $m_{\text {jet}}$ of top quark jets produced in ${\mathrm{t}}\overline{\mathrm{t}} $ events from pp collisions at $\sqrt{s}=8$ $\,\text {TeV}$ is reported for the jet with the largest transverse momentum $p_{\mathrm{T}}$ in highly boosted hadronic top quark decays. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 19.7 $\,\text {fb}^{-1}$ . The measurement is performed in the lepton+jets channel in which the products of the semileptonic decay ${\mathrm{t}} \rightarrow \mathrm{b} \mathrm {W}$ with $\mathrm {W}\rightarrow \ell \nu $ where $\ell $ is an electron or muon, are used to select ${\mathrm{t}}\overline{\mathrm{t}} $ events with large Lorentz boosts. The products of the fully hadronic decay ${\mathrm{t}} \rightarrow \mathrm{b} \mathrm {W}$ with $\mathrm {W}\rightarrow \mathrm{q} \overline{\mathrm{q}} '$ are reconstructed using a single Cambridge–Aachen jet with distance parameter $R=1.2$ , and $p_{\mathrm{T}} >400$ $\,\text {GeV}$ . The ${\mathrm{t}}\overline{\mathrm{t}} $ cross section as a function of $m_{\text {jet}}$ is unfolded at the particle level and is used to test the modelling of highly boosted top quark production. The peak position of the $m_{\text {jet}}$ distribution is sensitive to the top quark mass $m_{{\mathrm{t}}}$ , and the data are used to extract a value of $m_{{\mathrm{t}}}$ to assess this sensitivity.