Abstract
We report the measurements of the CP -violating parameters in B 0 s → D ∓ s K± decays observed in pp collisions, using a data set corresponding to an integrated luminosity of 3.0 fb−1 recorded with the LHCb detector. We measure Cf = 0.73 ± 0.14 ± 0.05, A ΔΓ f = 0.39 ± 0.28 ± 0.15, \( {A}_{\overline{f}}^{\varDelta \varGamma }=0.31\pm 0.28\pm 0.15 \), Sf = −0.52 ± 0.20 ± 0.07, \( {S}_{\overline{f}}=-0.49\pm 0.20\pm 0.07 \), where the uncertainties are statistical and systematic, respectively. These parameters are used together with the world-average value of the B 0 s mixing phase, −2βs, to obtain a measurement of the CKM angle γ from B 0 s → D ∓ s K± decays, yielding γ = (128 + 17− 22 )° modulo 180°, where the uncertainty contains both statistical and systematic contributions. This corresponds to 3.8 σ evidence for CP violation in the interference between decay and decay after mixing.

References
N. Cabibbo, Unitary symmetry and leptonic decays, Phys. Rev. Lett. 10 (1963) 531 [INSPIRE].
M. Kobayashi and T. Maskawa, CP violation in the renormalizable theory of weak interaction, Prog. Theor. Phys. 49 (1973) 652 [INSPIRE].
C. Jarlskog, Commutator of the quark mass matrices in the standard electroweak model and a measure of maximal CP nonconservation, Phys. Rev. Lett. 55 (1985) 1039 [INSPIRE].
R. Huerta and R. Pérez-Marcial, Comment on “commutator of the quark mass matrices in the standard electroweak model and a measure of maximal CP nonconservation”, Phys. Rev. Lett. 58 (1987) 1698.
C. Jarlskog, Jarlskog responds, Phys. Rev. Lett. 57 (1986) 2875 [INSPIRE].
LHCb collaboration, Measurement of the CKM angle γ from a combination of LHCb results, JHEP 12 (2016) 087 [arXiv:1611.03076] [INSPIRE].
I. Dunietz and R.G. Sachs, Asymmetry between inclusive charmed and anticharmed modes in B 0 , \( {\overline{B}}^0 \) decay as a measure of CP violation, Phys. Rev. D 37 (1988) 3186 [Erratum ibid. D 39 (1989) 3515] [INSPIRE].
R. Aleksan, I. Dunietz and B. Kayser, Determining the CP-violating phase γ, Z. Phys. C 54 (1992) 653 [INSPIRE].
R. Fleischer, New strategies to obtain insights into CP-violation through B (s) → D ±( s) K ∓ , D ∗ ±( s) K ∓ ,. . . and B (d) → D ± π ∓ , D ∗ ± π ∓ ,. . . decays, Nucl. Phys. B 671 (2003) 459 [hep-ph/0304027] [INSPIRE].
K. De Bruyn, R. Fleischer, R. Knegjens, M. Merk, M. Schiller and N. Tuning, Exploring B s → D (∗) ± s K ∓ decays in the presence of a sizable width difference ΔΓs, Nucl. Phys. B 868 (2013) 351 [arXiv:1208.6463] [INSPIRE].
BaBar collaboration, B. Aubert et al., Measurement of time-dependent CP-violating asymmetries and constraints on sin(2β + γ) with partial reconstruction of B → D ∗∓ π ± decays, Phys. Rev. D 71 (2005) 112003 [hep-ex/0504035] [INSPIRE].
BaBar collaboration, B. Aubert et al., Measurement of time-dependent CP asymmetries in B 0 → D (∗)± π ∓ and B 0 → D ± ρ ∓ decays, Phys. Rev. D 73 (2006) 111101 [hep-ex/0602049] [INSPIRE].
Belle collaboration, F.J. Ronga et al., Measurements of CP violation in B 0 → D ∗− π + and B 0 → D − π + decays, Phys. Rev. D 73 (2006) 092003 [hep-ex/0604013] [INSPIRE].
Belle collaboration, S. Bahinipati et al., Measurements of time-dependent CP asymmetries in B → D ∗∓ π ± decays using a partial reconstruction technique, Phys. Rev. D 84 (2011) 021101 [arXiv:1102.0888] [INSPIRE].
Heavy Flavor Averaging Group (HFAG) collaboration, Y. Amhis et al., Averages of b-hadron, c-hadron and τ -lepton properties as of summer 2014, arXiv:1412.7515 [INSPIRE].
L. Wolfenstein, Parametrization of the Kobayashi-Maskawa matrix, Phys. Rev. Lett. 51 (1983) 1945 [INSPIRE].
Particle Data Group collaboration, C. Patrignani et al., Review of particle physics, Chin. Phys. C 40 (2016) 100001 [INSPIRE].
LHCb collaboration, Measurement of CP-violation and the B 0 s meson decay width difference with B 0 s → J/ψK + K − and B 0 s → J/ψπ + π − decays, Phys. Rev. D 87 (2013) 112010 [arXiv:1304.2600] [INSPIRE].
LHCb collaboration, Measurement of CP asymmetry in B 0 s → D ∓ s K ± decays, JHEP 11 (2014) 060 [arXiv:1407.6127] [INSPIRE].
LHCb collaboration, Measurement of the CP asymmetry in \( {B}_s^0-{\overline{B}}_s^0 \) mixing, Phys. Rev. Lett. 117 (2016) 061803 [Addendum ibid. 118 (2017) 129903] [arXiv:1605.09768] [INSPIRE].
M. Pivk and F.R. Le Diberder, SPlot: a statistical tool to unfold data distributions, Nucl. Instrum. Meth. A 555 (2005) 356 [physics/0402083] [INSPIRE].
Y. Xie, sFit: a method for background subtraction in maximum likelihood fit, arXiv:0905.0724 [INSPIRE].
LHCb collaboration, The LHCb detector at the LHC, 2008 JINST 3 S08005 [INSPIRE].
LHCb collaboration, LHCb detector performance, Int. J. Mod. Phys. A 30 (2015) 1530022 [arXiv:1412.6352] [INSPIRE].
R. Aaij et al., Performance of the LHCb vertex locator, 2014 JINST 9 09007 [arXiv:1405.7808] [INSPIRE].
LHCb Outer Tracker Group collaboration, R. Arink et al., Performance of the LHCb outer tracker, 2014 JINST 9 P01002 [arXiv:1311.3893] [INSPIRE].
LHCb RICH Group collaboration, M. Adinolfi et al., Performance of the LHCb RICH detector at the LHC, Eur. Phys. J. C 73 (2013) 2431 [arXiv:1211.6759] [INSPIRE].
R. Aaij et al., The LHCb trigger and its performance in 2011, 2013 JINST 8 P04022 [arXiv:1211.3055] [INSPIRE].
V.V. Gligorov and M. Williams, Efficient, reliable and fast high-level triggering using a bonsai boosted decision tree, 2013 JINST 8 P02013 [arXiv:1210.6861] [INSPIRE].
T. Sjöstrand, S. Mrenna and P.Z. Skands, A brief introduction to PYTHIA 8.1, Comput. Phys. Commun. 178 (2008) 852 [arXiv:0710.3820] [INSPIRE].
T. Sjöstrand, S. Mrenna and P.Z. Skands, PYTHIA 6.4 physics and manual, JHEP 05 (2006) 026 [hep-ph/0603175] [INSPIRE].
I. Belyaev et al., Handling of the generation of primary events in Gauss, the LHCb simulation framework, J. Phys. Conf. Ser. 331 (2011) 032047 [INSPIRE].
D.J. Lange, The EvtGen particle decay simulation package, Nucl. Instrum. Meth. A 462 (2001) 152 [INSPIRE].
P. Golonka and Z. Was, PHOTOS Monte Carlo: a precision tool for QED corrections in Z and W decays, Eur. Phys. J. C 45 (2006) 97 [hep-ph/0506026] [INSPIRE].
GEANT4 collaboration, J. Allison et al., GEANT4 developments and applications, IEEE Trans. Nucl. Sci. 53 (2006) 270 [INSPIRE].
GEANT4 collaboration, S. Agostinelli et al., GEANT4: a simulation toolkit, Nucl. Instrum. Meth. A 506 (2003) 250 [INSPIRE].
M. Clemencic et al., The LHCb simulation application, Gauss: design, evolution and experience, J. Phys. Conf. Ser. 331 (2011) 032023 [INSPIRE].
W.D. Hulsbergen, Decay chain fitting with a Kalman filter, Nucl. Instrum. Meth. A 552 (2005) 566 [physics/0503191] [INSPIRE].
L. Breiman, J.H. Friedman, R.A. Olshen and C.J. Stone, Classification and regression trees. Wadsworth international group, Belmont CA U.S.A., (1984) [INSPIRE].
B.P. Roe, H.-J. Yang, J. Zhu, Y. Liu, I. Stancu and G. McGregor, Boosted decision trees, an alternative to artificial neural networks, Nucl. Instrum. Meth. A 543 (2005) 577 [physics/0408124] [INSPIRE].
T. Skwarnicki, A study of the radiative cascade transitions between the Upsilon-prime and Upsilon resonances, Ph.D. thesis, Institute of Nuclear Physics, Krakow Poland, (1986) [INSPIRE].
K.S. Cranmer, Kernel estimation in high-energy physics, Comput. Phys. Commun. 136 (2001) 198 [hep-ex/0011057] [INSPIRE].
A. Powell et al., Particle identification at LHCb, PoS(ICHEP 2010)020 [INSPIRE].
LHCb collaboration, A new algorithm for identifying the flavour of B 0 s mesons at LHCb, 2016 JINST 11 P05010 [arXiv:1602.07252] [INSPIRE].
LHCb collaboration, Opposite-side flavour tagging of B mesons at the LHCb experiment, Eur. Phys. J. C 72 (2012) 2022 [arXiv:1202.4979] [INSPIRE].
LHCb collaboration, Measurement of CP violation in B 0 → J/ψK 0 S decays, Phys. Rev. Lett. 115 (2015) 031601 [arXiv:1503.07089] [INSPIRE].
T.M. Karbach, G. Raven and M. Schiller, Decay time integrals in neutral meson mixing and their efficient evaluation, arXiv:1407.0748 [INSPIRE].
LHCb collaboration, Precision measurement of the \( {B}_s^0-{\overline{B}}_s^0 \) oscillation frequency with the decay B 0 s → D − s π +, New J. Phys. 15 (2013) 053021 [arXiv:1304.4741] [INSPIRE].
LHCb collaboration, Measurement of the \( {\overline{B}}^0-{B}^0 \) and \( {\overline{B}}_s^0-{B}_s^0 \) production asymmetries in pp collisions at \( \sqrt{s}=7 \) TeV, Phys. Lett. B 739 (2014) 218 [arXiv:1408.0275] [INSPIRE].
LHCb collaboration, Measurement of CP asymmetry in D 0 → K − K + and D 0 → π − π + decays, JHEP 07 (2014) 041 [arXiv:1405.2797] [INSPIRE].
LHCb collaboration, Measurement of the CKM angle γ from a combination of B ± → Dh ± analyses, Phys. Lett. B 726 (2013) 151 [arXiv:1305.2050] [INSPIRE].
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