Inclusive $W$ and $Z$ production in the forward region at $\sqrt{s} = 7$ TeV

R. Aaij , S. Barsuk (1) , O. Callot (1) , J. He (1) , B. Jean-Marie (1) , J. Lefrançois (1) , F. Machefert (1) , A. Martin Sanchez (1) , M. Nicol (1) , P. Robbe (1) , M.-H. Schune (1) , B. Viaud (1) , I. Videau (1) , E. Ben-Haim (2) , M. Benayoun (2) , P. David (2) , L. del Buono (2) , A. Martens (2) , I. de Bonis (3) , D. Decamp (3) , Ph. Ghez (3) , P. Hopchev (3) , J.-P. Lees (3) , I.V. Machikhiliyan (3) , M.-N. Minard (3) , B. Pietrzyk (3) , S. t'Jampens (3) , V. Tisserand (3) , E. Tournefier (3) , Ziad Zj Ajaltouni (4) , O. Deschamps (4) , Pierre Henrard (4) , Marwa Jahjah-Hussein (4) , R. Lefèvre (4) , L. Li Gioi (4) , S. Monteil (4) , V. Niess (4) , Pascal Perret (4) , Diego Alejandro Roa Romero (4) , Krzysztof Grzegorz Sobczak (4) , C. Adrover (5) , E. Aslanides (5) , J. Cogan (5) , B. Khanji (5) , R. Le Gac (5) , O. Leroy (5) , G. Mancinelli (5) , E. Maurice (5) , M. Perrin-Terrin (5) , M. Sapunov (5) , J. Serrano (5) , A. Tsaregorodtsev (5)

1 LAL - Laboratoire de l'Accélérateur Linéaire
2 LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
3 LAPP - Laboratoire d'Annecy de Physique des Particules
4 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
5 CPPM - Centre de Physique des Particules de Marseille

Measurements of inclusive $W$ and $Z$ boson production cross-sections in $pp$ collisions at $\sqrt{s}=7$ TeV using final states containing muons are presented. The data sample corresponds to an integrated luminosity of 37 pb$^{-1}$ collected with the LHCb detector. The $W$ and $Z$ bosons are reconstructed from muons with a transverse momentum above 20 GeV$/c$ and pseudorapidity between 2.0 and 4.5, and, in the case of the $Z$ cross-section, a dimuon invariant mass between 60 and 120 GeV$/c^2$. The cross-sections are measured to be {$831\pm9\pm27\pm 29$ pb} for $W^+$, {$656\pm8\pm19\pm 23$ pb} for $W^-$ and {$76.7\pm1.7\pm3.3\pm2.7$ pb} for $Z$, where the first uncertainty is statistical, the second is systematic and the third is due to the luminosity. Differential cross-sections, $W$ and $Z$ cross-section ratios and the lepton charge asymmetry are also measured in the same kinematic region. The ratios are determined to be $\sigma_{W^+\rightarrow\mu^+\nu} / \sigma_{W^-\rightarrow\mu^-\bar{\nu}}= ${$1.27\pm0.02\pm0.01$}, and $\sigma_{W^+\rightarrow\mu^+\nu} + \sigma_{W^-\rightarrow\mu^-\bar{\nu}})/\sigma_{Z\rightarrow\mu\mu}= ${$19.4\pm0.5\pm0.9$}. The results are in general agreement with theoretical predictions, performed at next-to-next-to-leading order in QCD using recently calculated parton distribution functions.

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

R. Aaij, S. Barsuk, O. Callot, J. He, B. Jean-Marie, et al.. Inclusive $W$ and $Z$ production in the forward region at $\sqrt{s} = 7$ TeV. Journal of High Energy Physics, 2012, 06, pp.058. ⟨10.1007/JHEP06(2012)058⟩. ⟨in2p3-00686501⟩