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Measurement ofCPasymmetries in two-bodyB

0ðsÞ

-meson decays to charged pions and kaons

R. Aaijet al.

(LHCb Collaboration) (Received 30 May 2018; published 10 August 2018)

The time-dependentCPasymmetries inB

0 andB 0s →K K decays are measured using a data sample ofppcollisions corresponding to an integrated luminosity of3.0fb

1, collected with

the LHCb detector at center-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integratedCPasymmetries inB 0 →K andB 0s K decays. The results areC -¼-0.34?0.06?0.01,S -¼-0.63?0.05?0.01,C K K -¼0.20?0.06?0.02, S K K -¼0.18?0.06?0.02,A

ΔΓK

K -¼-0.79?0.07?0.10,AB 0 CP

¼-0.084?0.004?0.003, and

A B 0s CP ¼0.213?0.015?0.007, where the first uncertainties are statistical and the second systematic.

Evidence forCPviolation is found in theB

0s →K K decay for the first time.

DOI:10.1103/PhysRevD.98.032004

I. INTRODUCTION

The study ofCPviolation in charmless decays ofB

0ðsÞ

mesons to charged two-body final states represents a powerful tool to test the Cabibbo-Kobayashi-Maskawa (CKM) picture[1,2]of the quark-flavor mixing in the Standard Model (SM) and to investigate the presence of physics lying beyond[3-9]. As discussed in Refs.[5,8,9], the hadronic parameters entering theB 0 and B 0s →K K decay amplitudes are related by U-spin symmetry, i.e., by the exchange ofdandsquarks in the decay diagrams. 1

It has been shown that a combined

analysis of the branching fractions andCPasymmetries in two-bodyB-meson decays, accounting for U-spin breaking effects, allows stringent constraints on the

CKM angleγand on theCP-violating phase-2β

s to be set[10,11]. More recently, it has been proposed to combine theCPasymmetries of theB 0 andB 0s →K K decays with information provided by the semileptonic decaysB 0 l

νandB

0s →K l

ν, in order to achieve

a substantial reduction of the theoretical uncertainty on the determination of-2βs [12,13]. TheCPasymmetry in the B 0 decay is also a relevant input to the determi- nation of the CKM angleα, when combined with othermeasurements from the isospin-related decaysB 0 0 0 andB 0 [14-16]. In this paper, measurements of the time-dependentCP asymmetries inB 0 andB 0s →K K decays and of the time-integratedCPasymmetries inB 0 →K and B 0s þK decays are presented. The analysis is based on a data sample ofppcollisions corresponding to an integrated luminosity of3.0fb -1 , collected with the

LHCb detector at center-of-mass energies of 7 and

8 TeV. The results supersede those from previous analyses

performed with1.0fb -1 of integrated luminosity at

LHCb[17,18].

AssumingCPTinvariance, theCPasymmetry as a

function of decay time forB

0ðsÞ

mesons decaying to aCP eigenstatefis given by A CP

ðtÞ¼

B 0

ðsÞ

→f

ðtÞ-Γ

B 0

ðsÞ

→f

ðtÞ

B 0

ðsÞ

→f

ðtÞþΓ

B 0

ðsÞ

→fðtÞ -C f cosðΔm d;s tÞþS f sinðΔm d;s tÞ coshð d;s 2 tÞþA

ΔΓf

sinhð d;s 2 tÞ;ð1Þ whereΔm d;s andΔΓ d;s are the mass and width differences of the mass eigenstates in theB

0ðsÞ

-B

0ðsÞ

system. The quantitiesC f ,S f andA

ΔΓf

are defined as C f

1-jλ

f j 2

1þjλ

f j2 ;S f

2Imλ

f

1þjλ

f j 2 ;A

ΔΓf

2Reλ

f

1þjλ

f j 2

ð2Þ

whereλ f is given by

Full author list given at the end of the article.

Published by the American Physical Society under the terms of theCreative Commons Attribution 4.0 Internationallicense. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAPquotesdbs_dbs33.pdfusesText_39

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