Observation and measurement of Higgs boson decays to $WW^{\ast}$ with the ATLAS detector

G. Aad (1) , S. Albrand (2) , J. Brown (2) , J. Collot (2) , S. Crépé-Renaudin (2) , B. Dechenaux (2) , P.A. Delsart (2) , C. Gabaldon (2) , M.H. Genest (2) , J.Y. Hostachy (2) , F. Ledroit-Guillon (2) , A. Lleres (2) , A. Lucotte (2) , F. Malek (2) , C. Monini (2) , J. Stark (2) , B. Trocmé (2) , M. Wu (2) , G. Rahal (3) , Z. Barnovska (4) , N. Berger (4) , M. Delmastro (4) , L. Di Ciaccio (4) , T.K.O. Doan (4) , S. Elles (4) , C. Goy (4) , T. Hryn’ova (4) , S. Jézéquel (4) , H. Keoshkerian (4) , I. Koletsou (4) , R. Lafaye (4) , J. Leveque (4) , V.P. Lombardo (4) , N. Massol (4) , H. Przysiezniak (4) , G. Sauvage (4) , E. Sauvan (1, 4) , M. Schwoerer (4) , O. Simard (4) , T. Todorov (4) , I. Wingerter-Seez (4) , L. Alio (1) , M. Barbero (1) , J.-C. Clémens (1) , Y. Coadou (1) , Sara Diglio (1) , F. Djama (1) , L. Feligioni (1) , G Hallewell (1) , D. Hoffmann (1) , F. Hubaut (1) , E.B.F.G. Knoops (1) , E. Le Guirriec (1) , B. Li (1) , D. Madaffari (1) , K. Mochizuki (1) , E. Monnier (1) , G.S. Muanza (1) , Y. Nagai (1) , P. Pralavorio (1) , A.N. Rozanov (1) , T. Serre (1) , M. Talby (1) , E. Tiouchichine (1) , S. Tisserant (1) , J. Toth (1) , F. Touchard (1) , M. Ughetto (1) , L. Vacavant (1) , M.K. Ayoub (5) , A. Bassalat (5) , C. Bécot (5) , S. Binet (5) , C. Bourdarios (5) , D. Delgove (5) , J-B. de Vivie De Regie (5) , L. Duflot (5) , M. Escalier (5) , L. Fayard (5) , D. Fournier (5) , E.L. Gkougkousis (5) , J-F. Grivaz (5) , T. Guillemin (5) , F. Hariri (5) , S. Henrot-Versille (5) , J. Hrivnac (5) , L. Iconomidou-Fayard (5) , M. Kado (5) , A. Lounis (5) , N. Makovec (5) , N. Morange (5) , C. Nellist (5) , P. Petroff (5) , L. Poggioli (5) , P. Puzo (5) , A. Renaud (5) , D. Rousseau (5) , G. Rybkin (5) , A.C. Schaffer (5) , E. Scifo (5) , L. Serin (5) , S. Simion (5) , R. Tanaka (5) , D. Zerwas (5) , Zhiqing Zhang (5) , Y. Zhao (5)

1 CPPM - Centre de Physique des Particules de Marseille
2 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
3 CC-IN2P3 - Centre de Calcul de l'IN2P3
4 LAPP - Laboratoire d'Annecy de Physique des Particules
5 LAL - Laboratoire de l'Accélérateur Linéaire

We report the observation of Higgs boson decays to $WW^{\ast}$ based on an excess over background of 6.1 standard deviations in the dilepton final state, where the Standard Model expectation is 5.8 standard deviations. Evidence for the vector-boson fusion (VBF) production process is obtained with a significance of 3.2 standard deviations. The results are obtained from a data sample corresponding to an integrated luminosity of $25 \textrm{pb}^{-1}$ from $\sqrt{s}=7$ and 8 TeV $pp$ collisions recorded by the ATLAS detector at the LHC. For a Higgs boson mass of 125.36 GeV, the ratio of the measured value to the expected value of the total production cross section times branching fraction is $1.09^{+0.16}_{-0.15} \textrm{(stat.)}^{+0.17}_{-0.14} \textrm{(syst.)}$. The corresponding ratios for the gluon fusion and vector-boson fusion production mechanisms are $1.02\pm 0.19 \textrm{(stat.)}^{+0.22}_{-0.18} \textrm{(syst.)}$ and $1.27^{+0.44}_{-0.40} \textrm{(stat.)}^{+0.30}_{-0.21} \textrm{(syst.)}$, respectively. At $\sqrt{s}=8$ TeV, the total production cross sections are measured to be $\sigma(gg\to H\rightarrow WW^\ast) = 4.6\pm0.9\,\textrm{(stat.)}\,^{+0.8}_{-0.7}\,\textrm{(syst.)}\textrm{pb}$ and $\sigma(\textrm{VBF} H\rightarrow WW^\ast) = 0.51\,^{+0.17}_{-0.15}\,\textrm{(stat.)}\,^{+0.13}_{-0.08}\,\textrm{(syst.)}\textrm{pb}$. The fiducial cross section is determined for the gluon-fusion process in exclusive final states with zero or one associated jet.

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

G. Aad, S. Albrand, J. Brown, J. Collot, S. Crépé-Renaudin, et al.. Observation and measurement of Higgs boson decays to $WW^{\ast}$ with the ATLAS detector. Physical Review D, 2015, 92, pp.012006. ⟨10.1103/PhysRevD.92.012006⟩. ⟨in2p3-01092569⟩