First observation of CP violation in the decays of Bs mesons

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 (2) , F. Polci (2) , Ziad Zj Ajaltouni (3) , E. Cogneras (3) , O. Deschamps (3) , I. El Rifai (3) , M. Grabalosa Gándara (3) , Pierre Henrard (3) , M. Hoballah (3) , R. Lefèvre (3) , L. Li Gioi (3) , S. Monteil (3) , V. Niess (3) , Pascal Perret (3) , Diego Alejandro Roa Romero (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) , C. Adrover (5) , E. Aslanides (5) , J. Cogan (5) , R. Legac (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 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
4 LAPP - Laboratoire d'Annecy de Physique des Particules
5 CPPM - Centre de Physique des Particules de Marseille

Using pp collision data, corresponding to an integrated luminosity of $1.0 \mathrm{fb}^{-1}$, collected by LHCb in 2011 at a center-of-mass energy of 7 TeV, we report the measurement of direct CP violation in $B^0_s \to K^-\pi^+$ decays, $A_{C/!P}(B^0_s \rightarrow K^- \pi^+)=0.27 \pm 0.04\,\mathrm{(stat)} \pm 0.01\,\mathrm{(syst)}$, with significance exceeding five standard deviations. This is the first observation of CP violation in the decays of $B^0_s$ mesons. Furthermore, we provide an improved determination of direct CP violation in $B^0 \to K^+\pi^-$ decays, $A_{C/!P}(B^0\rightarrow K^+ \pi^-)=-0.080 \pm 0.007\,\mathrm{(stat)} \pm 0.003\,\mathrm{(syst)}$, which is the most precise measurement of this quantity to date.

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

R. Aaij, Y. Amhis, S. Barsuk, O. Callot, J. He, et al.. First observation of CP violation in the decays of Bs mesons. Physical Review Letters, 2013, 110, pp.221601. ⟨10.1103/PhysRevLett.110.221601⟩. ⟨in2p3-00817212⟩