First measurement of the CP-violating phase in $B_s^0 \to \phi \phi$ decays

R. Aaij , Y. Amhis (1) , S. Barsuk (1) , O. Callot (1) , J. He (1) , O. Kochebina (1) , J. Lefrançois (1) , F. Machefert (1) , A. Martin Sanchez (1) , M. Nicol (1) , P. Robbe (1) , M.-H. Schune (1) , M. Teklishyn (1) , B. Viaud (1) , E. Ben-Haim (2) , M. Benayoun (2) , P. David (2) , L. del Buono (2) , A. Martens (2) , D.A. Milanes , F. Polci (2) , C. Adrover (3) , E. Aslanides (3) , J. Cogan (3) , R. Legac (3) , O. Leroy (3) , G. Mancinelli (3) , E. Maurice (3) , M. Perrin-Terrin (3) , M. Sapunov (3) , J. Serrano (3) , A. Tsaregorodtsev (3) , I. de Bonis (4) , D. Decamp (4) , Ph. Ghez (4) , P. Hopchev (4) , J.-P. Lees (4) , I.V. Machikhiliyan (4) , M.-N. Minard (4) , B. Pietrzyk (4) , W. Qian (4) , S. t'Jampens (4) , V. Tisserand (4) , E. Tournefier (4) , Ziad Zj Ajaltouni (5) , E. Cogneras (5) , O. Deschamps (5) , I. El Rifai (5) , M. Grabalosa Gándara (5) , Pierre Henrard (5) , M. Hoballah (5) , R. Lefèvre (5) , L. Li Gioi (5) , S. Monteil (5) , V. Niess (5) , Pascal Perret (5) , Diego Alejandro Roa Romero (5)

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

A first flavour-tagged measurement of the time-dependent CP-violating asymmetry in $B_s^0 \to \phi\phi$ decays is presented. In this decay channel, the CP-violating weak phase arises due to CP violation in the interference between $B_s^0$-$\bar{B}_s^0$ mixing and the $b \to s \bar{s} s $ gluonic penguin decay amplitude. Using a sample of $pp$ collision data corresponding to an integrated luminosity of $1.0\; fb^{-1}$ and collected at a centre-of-mass energy of $7 \rm TeV$ with the LHCb detector, $880\ \B_s^0 \to \phi\phi$ signal decays are obtained. The CP-violating phase is measured to be in the interval [-2.46, -0.76] \rm rad$ at 68% confidence level. The p-value of the Standard Model prediction is 16%.

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

R. Aaij, Y. Amhis, S. Barsuk, O. Callot, J. He, et al.. First measurement of the CP-violating phase in $B_s^0 \to \phi \phi$ decays. Physical Review Letters, 2013, 110, pp.241802. ⟨10.1103/PhysRevLett.110.241802⟩. ⟨in2p3-00805894⟩