Measurement of the angular coefficients in $Z$-boson events using electron and muon pairs from data taken at $\sqrt{s}=8$ TeV with the ATLAS detector

G. Aad (1) , Z. Barnovska (2) , N. Berger (2) , M. Delmastro (2) , L. Di Ciaccio (2) , S. Elles (2) , K. Grevtsov (2) , T. Hryn’ova (2) , S. Jézéquel (2) , I. Koletsou (2) , R. Lafaye (2) , Jérémy Lévêque (2) , P. Mastrandea (2) , G. Sauvage (2) , E. Sauvan (2) , O. Simard (2) , T. Todorov (2) , I. Wingerter-Seez (2) , E. Yatsenko (2) , M.K. Ayoub (3) , A. Bassalat (3) , S. Binet (3) , C. Becot , C. Bourdarios (3) , J.B. de Vivie De Regie (3) , D. Delgove (3) , L. Duflot (3) , M. Escalier (3) , L. Fayard (3) , D. Fournier (3) , E.L. Gkougkousis (3) , J.-F. Grivaz (3) , T. Guillemin (3) , F. Hariri (3) , S. Henrot-Versille (3) , J. Hrivnac (3) , L. Iconomidou-Fayard (3) , M. Kado (3) , A. Lounis (3) , N. Makovec (3) , N. Morange (3) , C. Nellist (3) , P. Petroff (3) , L. Poggioli (3) , P. Puzo (3) , A. Renaud (3) , G. Rybkin (3) , D. Rousseau (3) , A.C. Schaffer (3) , L. Serin (3) , E. Scifo (3) , S. Simion (3) , R. Tanaka (3) , D. Zerwas (3) , Zhongkai Zhang (3) , Y. Zhao (3) , D. Boumediene (4) , E. Busato (4) , D. Calvet (4) , S. Calvet (4) , A.R. Chomont (4) , J. Donini (4) , Ph. Gris (4) , R. Madar (4) , D. Pallin (4) , S.M. Romano Saez (4) , C. Santoni (4) , D. Simon (4) , F. Vazeille (4) , M. Alstaty (1) , M. Barbero (1) , A. Calandri (1) , T.P. Calvet (1) , Y. Coadou (1) , C. Diaconu (1) , Sara Diglio (1) , F. Djama (1) , V. Ellajosyula (1) , L. Feligioni (1) , J. Gao (1) , A. Hadef (1) , G.D. Hallewell (1) , F. Hubaut (1) , S.J. Kahn (1) , E. B. F. G. Knoops (1) , E. Le Guirriec (1) , J. Liu (1) , K. Liu (1) , D. Madaffari (1) , E. Monnier (1) , S. Muanza (1) , E. Nagy (1) , P. Pralavorio (1) , Y. Rodina (1) , A. Rozanov (1) , M. Talby (1) , T. Theveneaux-Pelzer (1) , R.E. Ticse Torres (1) , S. Tisserant (1) , J. Toth (1) , F. Touchard (1) , L. Vacavant (1) , Chen Wang (1) , S. Albrand (5) , S. Berlendis (5) , C. Camincher (5) , J. Collot (5) , S. Crépé-Renaudin (5) , P.A. Delsart (5) , C. Gabaldon (5) , M.H. Genest (5) , P.O.J. Gradin (5) , J.Y. Hostachy (5) , F. Ledroit-Guillon (5) , A. Lleres (5) , A. Lucotte (5) , F. Malek (5) , E. Petit (5) , J. Stark (5) , B. Trocmé (5) , M. Wu (5)

1 CPPM - Centre de Physique des Particules de Marseille
2 LAPP - Laboratoire d'Annecy de Physique des Particules
3 LAL - Laboratoire de l'Accélérateur Linéaire
4 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
5 LPSC - Laboratoire de Physique Subatomique et de Cosmologie

The angular distributions of Drell-Yan charged lepton pairs around the $Z$-boson mass peak probe the underlying QCD dynamics of $Z$-boson production. This paper presents a measurement of the complete set of angular coefficients $A_{0-7}$ describing these distributions in the $Z$-boson Collins-Soper frame. The data analysed correspond to 20.3 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 8$ TeV, collected by the ATLAS detector at the CERN LHC. The measurements are compared to the most precise fixed-order calculations currently available ($\mathcal{O}(\alpha^{2}_{s})$) and with theoretical predictions embedded in Monte Carlo generators. The measurements are precise enough to probe QCD corrections beyond the formal accuracy of these calculations and to provide discrimination between different parton-shower models. A significant deviation from the $\mathcal{O}(\alpha^{2}_{s})$ predictions is observed for $A_{0}-A_{2}$. Evidence is found for non-zero $A_{5,6,7}$, consistent with expectations.

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

G. Aad, Z. Barnovska, N. Berger, M. Delmastro, L. Di Ciaccio, et al.. Measurement of the angular coefficients in $Z$-boson events using electron and muon pairs from data taken at $\sqrt{s}=8$ TeV with the ATLAS detector. Journal of High Energy Physics, 2016, 08, pp.159. ⟨10.1007/JHEP08(2016)159⟩. ⟨in2p3-01326882⟩