Measurement of the $W$ boson polarisation in $t\bar{t}$ events from $pp$ collisions at $\sqrt{s}$ = 8 TeV in the lepton+jets channel with ATLAS - Université Clermont Auvergne Accéder directement au contenu
Article Dans Une Revue European Physical Journal C: Particles and Fields Année : 2017

Measurement of the $W$ boson polarisation in $t\bar{t}$ events from $pp$ collisions at $\sqrt{s}$ = 8 TeV in the lepton+jets channel with ATLAS

M Aaboud , N. Berger (1) , A.M. Burger (1) , M. Delmastro (1) , L. Di Ciaccio (1) , S. Elles (1) , K. Grevtsov (1) , T. Guillemin (1) , T. Hryn’ova (1) , S. Jézéquel (1) , I. Koletsou (1) , R. Lafaye (1) , Jérémy Lévêque (1) , P. Mastrandea (1) , E. Sauvan (1) , B.H. Smart (1) , T. Todorov (1) , I. Wingerter-Seez (1) , E. Yatsenko (1) , D. Boumediene (2) , E. Busato (2) , D. Calvet (2) , S. Calvet (2) , A.R. Chomont (2) , J. Donini (2) , S. Ganguly (2) , Ph. Gris (2) , R. Madar (2) , D. Pallin (2) , S.M. Romano Saez (2) , C. Santoni (2) , D. Simon (2) , F. Vazeille (2) , G. Aad (3) , M. Alstaty (3) , M. Barbero (3) , A. Calandri (3) , T.P. Calvet (3) , Y. Coadou (3) , C. Diaconu (3) , F. Djama (3) , V. Ellajosyula (3) , L. Feligioni (3) , A. Hadef (3) , G.D. Hallewell (3) , F. Hubaut (3) , S.J. Kahn (3) , E. B. F. G. Knoops (3) , E. Le Guirriec (3) , K. Liu (3) , D. Madaffari (3) , E. Monnier (3) , S. Muanza (3) , E. Nagy (3) , P. Pralavorio (3) , Y. Rodina (3) , A. Rozanov (3) , M. Talby (3) , T. Theveneaux-Pelzer (3) , R.E. Ticse Torres (3) , S. Tisserant (3) , J. Toth (4, 3) , F. Touchard (3) , L. Vacavant (3) , Chen Wang (5, 3) , R. Wolff (3) , S. Albrand (6) , S. Berlendis (6) , A. Bethani (6) , C. Camincher (6) , J. Collot (6) , S. Crépé-Renaudin (6) , P.A. Delsart (6) , C. Gabaldon (6) , M.H. Genest (6) , P.O.J. Gradin (6) , J.Y. Hostachy (6) , F. Ledroit-Guillon (6) , A. Lleres (6) , A. Lucotte (6) , F. Malek (6) , E. Petit (6) , J. Stark (6) , B. Trocmé (6) , M. Wu (6) , G. Rahal (7)
M Aaboud
  • Fonction : Auteur
N. Berger
T. Hryn’ova
S. Calvet
G. Aad
Y. Coadou

Résumé

This paper presents a measurement of the polarisation of $W$ bosons from $t\bar{t}$ decays, reconstructed in events with one high-$p_{\mbox{T}}$ lepton and at least four jets. Data from $pp$ collisions at the LHC were collected at $\sqrt{s}$ = 8 TeV and correspond to an integrated luminosity of 20.2 fb$^{-1}$. The angle $\theta^{*}$ between the $b$-quark from the top quark decay and a direct $W$ boson decay product in the $W$ boson rest frame is sensitive to the $W$ boson polarisation. Two different $W$ decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying $W$ boson, respectively. The most precise measurement of the $W$ boson polarisation via the distribution of $\cos{\theta^{*}}$ is obtained using the leptonic analyser and events in which at least two of the jets are tagged as $b$-quark jets. The fitted fractions of longitudinal, left- and right-handed polarisation states are $F_{\mathrm{0}}= 0.709 \pm {0.019}$, $F_{\mathrm{L}}= 0.299 \pm {0.015}$ and $F_{\mathrm{R}}= -0.008 \pm {0.014}$, and are the most precisely measured $W$ boson polarisation fractions to date. Limits on anomalous couplings of the $Wtb$ vertex are set.

Dates et versions

in2p3-01412923 , version 1 (09-12-2016)

Identifiants

Citer

M Aaboud, N. Berger, A.M. Burger, M. Delmastro, L. Di Ciaccio, et al.. Measurement of the $W$ boson polarisation in $t\bar{t}$ events from $pp$ collisions at $\sqrt{s}$ = 8 TeV in the lepton+jets channel with ATLAS. European Physical Journal C: Particles and Fields, 2017, 77, pp.264. ⟨10.1140/epjc/s10052-017-4819-4⟩. ⟨in2p3-01412923⟩
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