Measurement of the CP-violating weak phase φs and the decay width difference δΓc using the Bs 0→J/ψφ(1020) decay channel in pp collisions at √ s=8 TeV

Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Measurement

of

the

CP-violating

weak

phase

φ

_s

and

the

decay

width

difference

"#

_s

using

the

B

0

_s

→

J

/ψ φ (

1020

)

decay

channel

in

pp

collisions

at

√

s

₌

8 TeV

.

CMS

Collaboration

%

CERN,Switzerland

a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory: Received27July2015

Receivedinrevisedform11March2016 Accepted16March2016

Availableonline23March2016 Editor:M.Doser Keywords: CMS Physics B-physics CPviolation

The CP-violating weak phase φs of the B0s meson and the decay width difference "#s of the B0s

lightand heavy masseigenstates are measuredwiththe CMSdetectoratthe LHCusingadata sam-ple ofB0

s→J/ψ φ (1020)→

µ

+

µ

−K+K− decays. The analysed data set corresponds to an integrated

luminosity of 19.7 fb−1 collected in pp collisions at a centre-of-mass energy of 8 TeV. A total of

49 200 reconstructed B0

s decays are usedto extract thevalues ofφs and "#s by performinga

time-dependentand flavour-taggedangularanalysisofthe

µ

+

µ

−K+_K− _{finalstate.Theweakphaseis}

mea-sured to be φs= −0.075±0.097(stat)±0.031(syst) rad,and the decay width difference is "#s=

0.095±0.013(stat)±0.007(syst)ps−1.

2016CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.Thisisanopenaccess articleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

Whilenodirectevidenceofphysicsbeyondthestandardmodel (SM)hasyetbeenfoundattheCERNLHC,theB0

s mesonprovides

a rich sourceof possibilitiesto probe itsconsistency. Inthis Let-ter,ameasurementoftheweakphase

φ

softheB0s mesonandthe

decaywidthdifference

"#

s betweenthelightand heavyB0s mass

eigenstates ispresented,usingthedata collectedby theCMS ex-perimentinppcollisionsattheLHCwithacentre-of-massenergy of8TeV,correspondingtoanintegratedluminosityof19

.

7fb−1.

The CP-violating weak phase

φ

s originates from the

interfer-ence between direct B0

s meson decays into a CP eigenstate ccss

and decays through B0

s–B0s mixing to the same final state.

Ne-glecting penguindiagram contributions [1,2],

φ

s isrelatedto the

elementsoftheCabibbo–Kobayashi–Maskawaquarkmixingmatrix by

φ

s

$ −

2

β

s,where

β

s

=

arg

(

−

VtsV_tb∗

/

VcsV_cb∗

)

.Thepredictionfor

2

β

s, determined via a global fit to experimental data within the

SM, is 2

β

s

=

0

.

0363+₋0_0..0016₀₀₁₅ rad [3]. Since the value predicted by

the SMis veryprecise, anysignificantdeviationofthe measured value fromthispredictionwouldbe particularlyinteresting, as it wouldindicateapossiblecontributionofnew,unknown particles to the loop diagrams describing B0

s mixing. The theoretical

pre-dictionforthedecaywidthdifference

"#

s betweenthelightand

% _{E-mailaddress:cms-publication-committee-chair@cern.ch.}

heavyB0

s masseigenstatesBLandBH,assumingnonewphysicsin

B0

s–B0s mixing,is

"#

s

= #

L

− #

H

=

0

.

087

±

0

.

021 ps−1 [4].

Theweakphase

φ

s wasfirstmeasured bytheTevatron

exper-iments [5–8], and then at the LHC by the LHCb and ATLAS ex-periments[9–13],usingB0

s

→

J

/ψ φ (

1020

)

,B0s

→

J

/ψ

f0

(

980

)

,and

B0

s

→

J

/ψ

π

+

π

−decaysto

(

+

(

−h+h−,where

(

denotesamuonin

thepresentanalysisandhstandsforakaonorapion.Finalstates thatdonothaveasingleCPeigenvaluerequireanangularanalysis to disentangle the CP-odd and CP-even components. The time-dependent angular analysis can be performed by measuring the decayanglesofthefinal-stateparticles

(

+

(

−h+h−andtheproper

decay time of the B0

s multiplied by the speed of light [14],

re-ferredtoasctinwhatfollows.InthisLetter,theB0

s

→

J

/ψ φ (

1020

)

decaytothefinalstate

µ

+

_µ

−_K+_K− _{isanalysed,and possible}

ad-ditional contributions to the result from the nonresonant decay B0

s

→

J

/ψ

K+K−aretakenintoaccountbyincludingatermforan

additionalamplitude(S-wave)inthefit.

In this measurement the transversity basis is used [14]. The three angles

)

= (θ

T

,

ψ

T

,

ϕ

T

)

of the transversity basis are

illus-tratedin

Fig. 1

.Theangles

θ

T and

ϕ

T arethepolarandazimuthal

angles,respectively,ofthe

µ

+ _{intherestframeoftheJ}

_/ψ

_where

thexaxisisdefinedbythedirectionofthe

φ (

1020

)

mesoninthe

J

/ψ

restframe,andthex–y planeisdefinedbythedecayplaneof the

φ (

1020

)

→

K+K−.Thehelicityangle

ψ

TistheangleoftheK+

inthe

φ (

1020

)

rest frame with respect to thenegative J

/ψ

mo-mentumdirection.

http://dx.doi.org/10.1016/j.physletb.2016.03.046

0370-2693/2016CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

Table 1

Angularandtime-dependenttermsofthesignalmodel.

i gi(θT, ψT,ϕT) Ni ai bi ci di 1 2 cos2_ψT(1−sin2_θ Tcos2ϕT) |A0(0)|2 1 D C −S 2 sin2_ψ T(1−sin2_θ Tsin2ϕT) _|A_&(0)_|2 1 D C ₋S 3 sin2_ψ Tsin2θT |A⊥(0)_|2 1 −D C S

4 −sin2ψTsin 2θTsinϕT |A&(0)||A⊥(0)| Csin(δ⊥− δ&) Scos(δ⊥− δ&) sin(δ⊥− δ&) Dcos(δ⊥− δ&)

5 _√1

2sin 2ψTsin 2_θ

Tsin 2ϕT |A0(0)_||A_&(0)_| cos(δ_{&− δ}0) Dcos(δ_{&− δ}0) Ccos(δ_{&− δ}0) ₋Scos(δ_{&− δ}0)

6 _√1

2sin 2ψTsin 2θTsinϕT |A0(0)||A⊥(0)| Csin(δ⊥− δ0) Scos(δ⊥− δ0) sin(δ⊥− δ0) Dcos(δ⊥− δ0)

7 2

3(1−sin2θTcos2ϕT) |AS(0)|2 1 −D C S

8 1

3

√

6 sinψTsin2θTsin 2ϕT |AS(0)_||A_&(0)_| Ccos(δ_{&− δ}S) Ssin(δ_{&− δ}S) cos(δ_{&− δ}S) Dsin(δ_{&− δ}S)

9 1

3

√

6 sinψTsin 2θTcosϕT |AS(0)_||A_⊥(0)_| sin(δ_{⊥− δ}S) ₋Dsin(δ_{⊥− δ}S) Csin(δ_{⊥− δ}S) Ssin(δ_{⊥− δ}S)

10 4 3

√

3 cosψT(1−sin2θTcos2ϕT) _|AS(0)_||A0(0)_| Ccos(δ0− δS) Ssin(δ0− δS) cos(δ0− δS) Dsin(δ0− δS)

Fig. 1. DefinitionofthethreeanglesθT,ψT,andϕTdescribingthedecaytopology ofB0

s→J/ψ φ(1020).Seetextfordetails.

The differentialdecayrate ofB0

s

→

J

/ψ φ (

1020

)

isrepresented

usingthefunction f

(),

ct

,

α

)

asinRef.[15]:

d4

_#

!

_B0 s

"

d

)

d

(

ct

)

=

f

(),

ct

,

α

)

∝

10

#

i=1 O_i

(

ct

,

α

)

gi

()),

(1)

where Oi are time-dependentfunctions, gi areangularfunctions,

and

α

isasetofphysicsparameters. Thefunctions Oi

(

ct

,

α

)

are:

Oi

(

ct

,

α

)

=

Nie−ct/cτ

$

aicosh

%

"#

st 2

&

+

bisinh

%

"#

st 2

&

+

cicos

("

mst

)

+

disin

("

mst

)

'

,

where

"

msisthemassdifferencebetweentheheavyandlightB0s

masseigenstates,c

τ

isdefinedastheproductofthelifetimeand thespeed oflight,thefunction gi

())

and thetermsNi,ai,bi,ci,

anddi aregivenin

Table 1

.

ThetermsC,S,andD aredefinedas: C

=

1₁

− |λ|

2

+ |λ|

2

,

S

= −

2

|λ|

sin

φ

s 1

+ |λ|

2

,

D

= −

2

|λ|

cos

φ

s 1

+ |λ|

2

,

using the same sign convention as the LHCb experiment [10]. Equation(1)representsthemodelforB0

s.ThemodelforB0s is

ob-tainedbychangingthesignoftheciandditerms.Theparameters

|

A_⊥

|

2_,

_|

_A

0

|

2,and

|

A&

|

2arethemagnitudessquaredofthe

perpen-dicular,longitudinal,andparallel P-waveamplitudes,respectively;

|

AS

|

2 is the magnitude squared of the S-wave amplitude

repre-sentingthefractionofnonresonantdecayB0

s

→

J

/ψ

K+K−;the

pa-rameters

δ

_⊥,

δ

0,

δ

_&,and

δ

S aretheircorrespondingstrongphases.

Thecomplexparameters

λ

f aredefinedas

λ

f

= (

q

/

p

)(

Af

/

Af

)

,

wheretheamplitudesAf

(

Af

)

describethedecayofaB0_s (B0s)

me-sontoafinalstate f,andtheparameters pandqrelatethemass andflavoureigenstatesasBH

=

pB0s

−

qBs0 andBL

=

pB0s

+

qB0s [16].

Assumingpolarisation-independentCP-violationeffects,

λ

f canbe

simplifiedas

λ

f

=

η

f

λ

,where

η

f istheCPeigenvalue.Theamount

ofCPviolationinmixingisassumedtobenegligible[17].Thus,no

|

q

/

p

|

termsareusedinEq.(1)whengoingfromtheB0

s modelto

theB0

s model.SincedirectCPviolationisexpectedtobesmall

the-oretically[3]andismeasuredtobesmall[9],

|λ|

issetto1.0.

2. TheCMSdetector

ThecentralfeatureoftheCMSapparatusisa13 m long super-conductingsolenoidof6 m internaldiameter,providingamagnetic field of3.8 T.Within thesolenoidvolume area siliconpixeland strip tracker,a leadtungstatecrystal electromagneticcalorimeter, anda brassandscintillatorhadroncalorimeter,eachcomposedof a barrel and two endcap sections. Muons are measured in gas-ionisationdetectorsembeddedinthesteelflux-returnyokeoutside thesolenoid.Extensiveforwardcalorimetrycomplementsthe cov-erageprovidedbythebarrelandendcapdetectors.

The main subdetectors used for the present analysis are the silicon tracker and the muon detection system. The sili-contrackermeasures chargedparticles withinthe pseudorapidity range

|

η

| <

2

.

5.Itconsistsof66million100

×

150µm2 silicon

pix-elsandmorethan9millionsiliconstrips.Fornonisolatedparticles oftransversemomentum1

<

pT

<

10GeV and

|

η

|

<

1

.

4,thetrack

resolutionsaretypically1.5%inpT and25–90(45–150)µminthe

transverse(longitudinal)impactparameter[18].

Muons are measured in the pseudorapidity range

|

η

|

<

2

.

4,

with detectionplanesmadeusingthreetechnologies:drift tubes, cathode strip chambers, and resistive plate chambers. The rel-ative pT resolution for low transverse momentum muons with

pT

<

10GeV isbetween0.8%and3.0%dependingon

|

η

|

[19]. Thefirstlevel(L1)oftheCMStriggersystem,composedof cus-tom hardwareprocessors, usesinformationfromthecalorimeters andmuondetectorstoselectthemostinterestingeventsinafixed timeintervaloflessthan4µs.Thehigh-leveltrigger(HLT) proces-sor farmfurther reducesthe event rate fromaround 100 kHz to around 400 Hz,beforedatastorage.AttheHLTstagethere isfull access toallthe eventinformation, includingtracking,and there-foreselectionssimilartothoseappliedofflinecanbeused.

AmoredetaileddescriptionoftheCMSdetector,togetherwith a definitionofthecoordinatesystemusedand therelevant kine-maticvariables,canbefoundinRef.[20].

3. Eventselectionandsimulatedsamples

A trigger optimised for the detection of B hadrons decaying to J

/ψ

is used to collect the data sample. The L1 trigger used in this analysis requires two muons, each with pT greater than

3GeV and

|

η

|

<

2

.

1. TheHLT requiresa J

/ψ

candidatedisplaced

from the luminous region. Each muon pT is required to be at

greater than6.9 GeV. TheJ

/ψ

candidatesare reconstructedfrom

themuonpairsselectedbythetriggerintheinvariantmass win-dow 2.9–3.3 GeV. The three-dimensional (3D) distanceof closest approachofthetwomuonstoeachotherisrequiredtobesmaller than 0

.

5 cm.The two muon trajectoriesare fittedto a common decayvertex. Thetransversedecaylength significanceLxy

/

σ

Lxy is

requiredtobe greaterthan 3,where Lxy isthe distancebetween

thecentreoftheluminousregionandthesecondaryvertexinthe transverse plane,and

σ

Lxy is the Lxy uncertainty.The

secondary-vertex fitprobability,calculated usingthe

χ

2 _{and thenumberof}

degrees of freedom of the vertex fit, must be greater than 10%. The angle

ρ

between thedimuontransverse momentumand the

Lxy directionisrequiredtosatisfycos

ρ

>

0

.

9.

Offline selection criteria are applied to the sample. The indi-vidual muon candidates are required to lie within a kinematic acceptance region of pT

>

4 GeV and

|

η

|

<

2

.

1. Two oppositely chargedmuoncandidatesarepairedandrequiredtooriginatefrom a commonvertex. Dimuoncandidateswith invariantmasswithin 150 MeV of the world-average J

/ψ

mass [21] are selected. Can-didate

φ (

1020

)

mesonsarereconstructedfrompairsofoppositely

chargedtrackswith pT

>

0

.

7GeV,afterremovingthe muon

can-didatetracks formingthe J

/ψ

.Each selectedtrack is assumed to beakaon,andtheinvariantmassofatrackpairisrequiredtobe within10 MeV oftheworld-average

φ (

1020

)

mass[21].

The B0

s candidates areformed by combining J

/ψ

and

φ (

1020

)

candidates. A kinematicfit of thetwo muon and two kaon can-didatesisperformed,with acommonvertex,and thedimuon in-variant mass is constrained to the nominal J

/ψ

mass [21]. A B0

s

candidateisretainediftheJ

/ψ φ (

1020

)

pairhasaninvariantmass

between 5.20 and 5.65 GeV and the

χ

2 _{vertex fit probability is}

greaterthan2%.

Multiple pp collisions can occur in the same beam crossing (pileup).Theaveragenumberofprimaryverticesinaneventis ap-proximately16,andeachselectedeventisrequiredtohaveatleast one reconstructed primary vertex. If there are multiple vertices, theonethatminimisestheanglebetweentheflightdirectionand themomentumoftheB0

s isselected.Theselectedprimaryvertex

isusedtomeasurect.Thequantityctiscalculatedfromthe trans-verse decaylength vectorofthe B0

s,

*

L B0 s xy,as ct

=

mB 0 s PDG

*

L B0 s xy

· *

pT

/

p2_T, wheremB0s

PDG is theworld-average B0s mass [21] and

*

pT isthe B0s

transversemomentumvector.Thedecaylengthiscalculatedinthe transverseplanetominimiseeffectsduetopileup.

Simulatedeventsare producedusingthe pythia v6.424Monte Carloeventgenerator[22].TheBhadrondecaysaremodelledwith the evtgen simulationpackage[23].FortheB0

s signalgeneration,

the evtpvvcplh moduleisused,whichsimulatesthedoublevector decaytaking intoaccount neutralmesonmixingand CP-violating time-dependent asymmetries. Final-state radiation is included in evtgen through the photos package [24,25].The eventsare then passed through a detailed Geant4-based simulation [26] of the CMSdetector.Thepredicteddistributionsfromsimulationofmany kinematic and geometric variables are compared to those from data and found to be in agreement. The simulated samples are used to determine the signal reconstruction efficiencies, and to studythebackgroundcomponentsintheB0

s signalmasswindow.

The main backgroundfor the B0

s

→

J

/ψ φ (

1020

)

decays

origi-nates fromnonpromptJ

/ψ

mesons fromthe decayofBhadrons,

suchasB0_,B±_,

₄

_{b,andBc.SincetheBccrosssectionissmall[21]}

compared tothat oftheB0

s [21],the Bc decayscanbe neglected.

Thecontributionofthe

4

b

→

J

/ψ

X channelstotheselectedevents

isalsofoundtobesmall,anditsmassdistributionintheselected massrangeisobservedtobeflat.Theeffectofbackgroundwith a similarsignalsignatureonthephysicsobservablesisstudiedusing simulated events, and found tobe negligible.The mass

distribu-Fig. 2. TheJ/ψK+_K−_{invariantmassdistributionoftheB}0

s candidates.Thesolidline

isafittothedata(solidmarkers),thedashedlineisthesignalcomponentandthe dot-dashedlineisthebackgroundcomponent.

tioninthesignalregionisshownin

Fig. 2

,andthedistributionof

ctanditsuncertainty

σ

ct in

Fig. 3

.

Efficiencycorrectionsowingtothedetectoracceptance, trigger selection, and selection criteria applied in the data analysis are taken into account in the modelling of the angular observables. The angularefficiency

5

())

is calculatedusing a fully simulated

sample ofB0

s

→

J

/ψ φ (

1020

)

→

µ

+

µ

−K+K− decays.Inthis

sam-ple,the

"#

sparameterissettozerotoavoidcorrelationsbetween

thedecaytime and theangularvariables. The

5

())

isfittedtoa

3D function of

)

to properly account for the correlation among

theangularobservables.

Thetriggerincludesadecaylengthsignificancerequirementfor theJ

/ψ

candidates.Accordingly, thevalue ofct is requiredtobe

greaterthan200 µminordertoavoidalifetimebiascomingfrom theturn-oncurveofthetriggerefficiency.Theefficiencyhistogram ofctisthenfittedwithastraightlineplusasigmoidfunction.

4. Flavourtagging

The flavour ofeach B0

s candidateatproduction time is

deter-minedwithanopposite-side (OS)flavourtaggingalgorithm.Since b quarks are produced as bb pairs,

¯

the flavour of the signal B0

s

mesonatproductiontimecanbeinferredfromtheflavourofthe other B hadron in the event. The tagging algorithm used in this analysisrequiresanadditionalmuonorelectronintheevents con-taining a reconstructed B0

s

→

J

/ψ φ (

1020

)

decay. The additional

lepton is assumed to originate from a semileptonicdecay ofthe OSBhadron, b

→ (

ν

X decay,with

(

=

e

,

µ

.Forallthe eventsin

whichanOStagleptonisfoundthealgorithmprovidesatag de-cision

ξ

basedonthecharge ofthelepton:

ξ

= +

1 forsignalB0_s,

and

ξ

= −

1 forsignalB0s.

The tag decision is affected by processes that reverse the charge-flavourcorrelation, such as cascade decaysb

→

c

→ (

, or semileptonicdecaysofneutralOSB mesonsthathaveoscillatedto theirantiparticlesbeforedecaying.Leptonsproducedfrom flavour-uncorrelatedsources,suchassemileptonicdecaysofpromptly pro-duced charmed hadrons, pion and kaon decays, J

/ψ

decays, and Dalitz decays of neutral pions further contribute to diluting the tag information. The probability of assigning a wrong flavour to thesignalB0

s isdescribedbythemistagprobability

ω

,definedas

theratioofthe numberofwronglytagged eventsdividedby the totalnumberoftaggedevents, whichisdirectlyrelatedtothe

di-Fig. 3. Thectdistribution(top)anditsuncertaintyσct (bottom)oftheB0s

candi-dates.Thesolidlineisafittothedata(solidmarkers),thedashedlineisthesignal componentandthedot-dashedlineisthebackgroundcomponent.Forthect dis-tributionthepull,definedasthedifferencebetweentheobservedeventsandthe fitfunctionappliedtothesumofthesignalandbackground,dividedbythe statis-ticaluncertaintyintheobservedevents,isdisplayedinthehistograminthelower panel.

lutionfactor D

_{= (}

1

−

2

ω

)

.Thevalueof

ω

isestimatedfromdata

onaper-eventbasis,asdescribedbelow.

The taggingalgorithmisoptimised bymaximisingthetagging power

P

tag

=

ε

tag

(

1

−

2

ω

)

2, whichrepresentstheequivalent

effi-ciency ofasample with perfecttagging(

ω

=

0).The term

ε

tag is

thetaggingefficiency,definedasthefractionofeventstowhicha tagdecisionisfoundbythetaggingalgorithm.

Opposite-side muonsandelectrons arereconstructed withthe particle-flow algorithm [27,28]. In each event, the muons (elec-trons) that are not part of the reconstructed B0

s

→

J

/ψ φ (

1020

)

decay are required to be identified with loose identification cri-teria.Iftherearemultiplemuons(electrons)intheevent,theone with the highest pT ischosen atthisstage. Thetag lepton

selec-tionsarethenoptimisedseparatelyformuonsandelectronsusing simulatedsignalsamplesofB0

s

→

J

/ψ φ (

1020

)

decays.Acut-based

opposite-side lepton selection is applied to reduce the number of leptons notoriginating fromB-hadron decays.To optimise the selection, severalvariables are studied,and a setof five

discrim-inating variables (pT,

η

, dxyz,

"

R, Isolation) is identified. A total

number of more than four million alternative cut configurations have been testedto determine the configurationthat maximises the tagging power, independently for muons and electrons. The tag muon is thus requiredto have pT

>

2

.

2GeV, the 3D impact

parameterdxyz withrespecttotheprimaryvertexassociatedwith

the signal B0

s isrequiredto be smallerthan 0

.

1 cm, and the

an-gular separation,

"

R

₌

(

("φ)

2

_{+ ("}

η

)

2,between the muonand thesignalB0

s isrequiredtobegreaterthan0.3,where

"φ

and

"

η

are the azimuthal angle and pseudorapidity differences between the directions of the tag muon and the B0

s candidate. Electrons

are requiredtohave pT

>

2

.

0 GeV,dxyz

<

0

.

1 cm,and

"

R

>

0

.

2.

Inaddition,amultivariatediscriminator(MVAe−π )tunedto sepa-rategenuineelectronsreconstructedbytheparticle-flowalgorithm from pions and photonsis applied to tag electrons by requiring thatthediscriminatorisgreaterthan0.2[28].

Amultilayerperceptronneuralnetwork(MLP-NN)oftheTMVA toolkit [29] is used to further separate the right- and wrong-tag leptons. Training and testing is performed using approximately 24 000 and 20 400 simulated B0

s

→

J

/ψ φ (

1020

)

events for the

muonand electronMLP-NNs,respectively,and twoindependently optimisedsets ofvariables.Halfofeachsample isusedfor train-ingand theotherhalffortesting.The inputvariablescommonto bothMLP-NNsare pT,

η

,anddxyz ofthetaglepton,andtwo

vari-ables relatedto activityin a conearound the leptondirection: a particle-flowrelativeisolationvariable[28]anda pT-weighted

av-erageofthechargesoftheparticlesinthecone.Specificvariables are furtherintroduced inthe MLP-NNsseparately formuonsand electrons.Formuons,thepTrelativetotheaxisofthejet

contain-ingthemuonisused,whileforelectronstheMVAe−π isexploited. Themistagprobabilitiesareobtainedfromdatausingthe self-tagging channel B±

_→

_J

_/ψ

_K±_{, where the charge of the}

recon-structedkaondeterminestheflavouroftheB±_{and,intheabsence}

ofmixing,oftheopposite-sideBhadronaswell.Themistag prob-abilitiesareparametrisedseparatelyformuonsandelectronswith analytic functions of theMLP-NN discriminators in order to pro-vide aper-eventvalue ofthepredicted mistagprobability

ω

.The functional forms of the parametrisations are obtained from the simulated B0

s sample. The candidate B± mesons are required to

pass aselection as similar as possibleto that appliedforthe re-construction of the signal B0

s candidates. The same trigger and

J

/ψ

reconstruction requirements as for the B0

s signal sample are

applied. A charged particle with pT

>

2 GeV, assumed to be a

kaon,iscombinedwiththedimuonpairinakinematicfit.An un-binned extended maximum-likelihoodfit to the invariant J

/ψ

K±

massisperformed,yieldingatotalof

(

707

±

2

)

×

103reconstructed

B±

→

J

/ψ

K± events. The tagging efficiency evaluated with the B±

_→

_J

_/ψ

_K± _{data sample is}

₍

₄

_.

₅₆

_±

₀

_.

₀₂

₎

_{% and}

₍

₃

_.

₉₂

_±

₀

_.

₀₂

₎

_%

formuonsandelectrons,respectively,wheretheuncertaintiesare statistical.

Themistagparametrisationcurvesevaluated withtheB±

con-trolchannel formuonsand electrons are shownin

Fig. 4

,where the parametrisations for the B± _{and B}0

s simulated samples are

shownforcomparison.

Most tagged eventshave only a single electron or muon tag. If both tags are available for a specific event (about 3.5% of the cases), thetaglepton with thegreatest value ofthedilution fac-torisretained,and thetagdecisionandtheestimatedmistagare takenfromthistaglepton.Theoverallleptontaggingefficiencyis

(

8

.

31

±

0

.

03

)

%, as measured indata with the B±

→

J

/ψ

K± data

sample.

To correctfor potential effectsinduced by the dependenceof the tagging algorithm on the B0

s

→

J

/ψ φ (

1020

)

simulation, the

mistag probability is calibratedby comparing the per-event pre-dicted

ω

tothemeasured

ω

meas _{obtainedfromthe B}±

_→

_J

_/ψ

_K±

Fig. 4. Themistagprobabilitiesω,definedastheratioofthenumberofwrongly taggedeventsdividedbythetotalnumberoftaggedevents,asafunctionofthe MLP-NNdiscriminators formuons(top)andelectrons (bottom).Thedata points (solidmarkers) areplacedatthe average weightedvalue oftheevents ineach bin. The verticalbarsshow the statisticaluncertaintiesand the horizontalbars thebinwidth.Thesolidlinerepresentstheparametrisationcurveextractedfrom thebackground-subtractedB± _{data;thedashedanddot-dashedlinesrefertothe}

parametrisationsextractedfromthesimulatedB0

sandB±samples,respectively.

data control channel. This is then fit to the function

ω

meas

₌

p0

+

p1

(

ω

−

ω

+

)

,chosentolimitthecorrelationbetweenthe

func-tion parameters p0 and p1.The parameter

ω

+ is fixedto a value

roughlycorrespondingtothemeanofthecalculatedmistag prob-ability,

ω

+

₌

₀

_.

_{35. The resulting calibration parameters are p0}

₌

0

.

348

±

0

.

003 and p1

=

1

.

01

±

0

.

03, and their uncertainties are

propagatedasastatisticaluncertaintyintheOStagger.

The systematic uncertainties related tothe calibration param-eters p0 and p1 are dominatedby the dependenceof these

pa-rameters on the flavour of the signal-side B hadron. The uncer-taintiesare estimatedfromB± _{dataand simulatedsamplesof B}0

s

and B± _{events. Systematic uncertainties originatingfrompossible}

variations intheCMSdata-takingconditions, thesignal B hadron kinematics,the analyticformofthemistag parametrisation func-tions,andthemodelusedtofittheB±_{invariantmassdistribution}

aretestedandfoundtobenegligible.

The overall tagging power of the OS lepton tagger, mea-sured with a sample of B±

_→

_J

_/ψ

_K± _{events, is}

_P

_tag

_{= (}

₁

_.

₃₀₇

_±

0

.

031

(

stat

)

±

0

.

007

(

syst

))

%,correspondingtothecombinedmistag

probability

ω

= (

30

.

17

±

0

.

24

(

stat

)

±

0

.

05

(

syst

))

%.

5. Maximum-likelihoodfit

Anunbinnedmaximum-likelihoodfittothedataisperformed byincludingthe informationontheB0

s invariant mass(mB0 s), the

three decay angles (

)

) of the reconstructed B0_s candidates, the

flavour tag decision (

ξ

), ct, and

σ

ct, obtained by summing in

quadraturethedecaylengthuncertaintyandtheuncertaintyinthe transversemomentum.The fitisapplied tothesample of70500 events,outofwhich5650 aretaggedevents,selectedinthemass range5.24–5.49 GeV and ct

₌

200–3000µm. From this multidi-mensional fit,the physics parametersof interest

"#

s,

φ

s, theB0s

mean lifetimec

τ

,

|

A_⊥

_|

2_,

_|

_A

0

|

2,

|

AS

|

2, and the strong phases

δ

_&,

δ

_⊥, and

δ

S⊥ are determined,where

δ

S⊥ is definedas the

differ-ence

δ

S

− δ

⊥. TheP-wave amplitudesare normalisedto unityby

constraining

|

A_&

_|

2 _to1

_{− |}

_A

⊥

|

2

− |

A0

|

2.Thefitmodelisvalidated

with simulated pseudo-experiments and with simulated samples withdifferentparametersets.

Thelikelihoodfunctioniscomposedofprobabilitydensity func-tions(pdf)describingthesignalandbackgroundcomponents.The likelihood fit algorithm is implemented using the RooFit pack-age from the ROOT framework [30]. The signal and background pdfs are formed as the product ofpdfs that modelthe invariant massdistribution and the time-dependent decay ratesof the re-constructed candidates. In addition, the signal pdf also includes the efficiencyfunction. Theevent likelihoodfunction

L

is repre-sented as:

L

=

Ls

+

Lbkg

,

Ls

=

Ns

)

˜

f

(),

ct

,

α

)

⊗

G

(

ct

,

σ

ct

)

5

())

*

×

Ps

(

m_B0 s

)

Ps

(

σ

ct

)

Ps

(ξ ),

L_bkg

₌

N_bkgP_bkg

(

cos

θ

T

,

ϕ

T

)

Pbkg

(

cos

ψ

T

)

Pbkg

(

ct

)

×

Pbkg

(

m_B0 s

)

Pbkg

(

σ

ct

)

Pbkg

(ξ ),

whereLsandLbkgarethepdfsthatdescribetheB0s

→

J

/ψ φ (

1020

)

signal and backgroundcontributions,respectively. Thenumber of signal(background)eventsisNs (Nbkg).Thepdf

˜

f

(),

ct

,

α

)

isthe

differentialdecayratefunction f

(),

ct

,

α

)

definedinEq.(1), mod-ified to includethe flavour tagging informationand the dilution term

(

1

−

2

ω

)

, whichare appliedto eachof theci anddi terms

oftheequation.Inthe

˜

f expression,thevalueof

δ

0issettozero,

followinga generalconvention. The function

5

())

isthe angular efficiencyand G

(

ct

,

σ

ct

)

is a Gaussian resolution function, which

makesuseoftheevent-by-eventdecaytimeuncertainty

σ

ct,scaled

byafactor

κ

.The

κ

factorisafunctionofct andisintroducedas acorrection totake care ofresidualeffectswhen thedecaytime uncertaintyisusedtomodelthectresolution.Thefunction

κ

(

ct

)

is measured using simulated samples and, on average, its value equals1.0towithinafewpercent.Theaveragedecaytime uncer-taintyincludingthe

κ

(

ct

)

factorequals23.4 µm.Alltheparameters

of thepdfs are left free to floatin the final fit, unless explicitly statedotherwise.The value of

"#

s is constrained to be positive,

basedonrecentmeasurements[31]. ThesignalmasspdfPs

(

m_B0

s

)

isthesumofthreeGaussian

func-tions with a common mean; the two smaller widths, the mean, andthefractionofeachGaussianfunctionarefixed tothevalues obtainedinaone-dimensionalmassfit.Thebackgroundmass dis-tribution Pbkg

(

m_B0

s

)

is described by an exponential function. The

background decay time component Pbkg

(

ct

)

is described by the

sumoftwoexponential functions.The angularparts ofthe back-groundspdfs Pbkg

(

cos

θ

T

,

ϕ

T

)

and Pbkg

(

cos

ψ

T

)

are described ana-lyticallyby aseriesofLegendrepolynomials forcos

θ

T and cos

ψ

T

Table 2

Resultsofthefittothedata.Uncertaintiesare statisticalonly.

Parameter Fit result

φs[rad] −0.075±0.097 "#s[ps−1] 0.095±0.013 |A0|2 0.510±0.005 |AS|2 0.012+₋0₀._.009₀₀₇ |A_⊥|2 _0.243±0.008 δ_&[rad] 3.48+0.07 −0.09 δS⊥[rad] 0.37+0.28 −0.12 δ_⊥[rad] 2.98±0.36 cτ[µm] 447.2±2.9

and sinusoidalfunctions for

ϕ

T.Forthe cos

θ

T and

ϕ

T variablesa

two-dimensional pdf is usedto take intoaccount the correlation amongthevariables.

The signaldecaytimeuncertaintypdf Ps

(

σ

ct

)

isa sumoftwo

Gammafunctions, withalltheparametersfixed tothevalues ob-tained by fitting a sample of background-subtracted events. The backgrounddecaytimeuncertaintypdf Pbkg

(

σ

ct

)

isrepresentedby

a Gammafunction.Alltheparametersarefixed tothevalues ob-tained by fittingthe B0

s invariant mass sidebandregions, defined

by themassrangesm_B0

s

=

5

.

24–5

.

28GeV and5.45–5.49 GeV.The

functions Ps

(ξ )

and Pbkg

(ξ )

are the tag decision

ξ

pdfs, which

havebeenobtainedfromthedata.

6. Resultsandsystematicuncertainties

The resultsof the fit are givenin Table 2, where the quoted uncertainties are statistical only. The corresponding correlation matrix for the statistical uncertainties in the physics fit

parame-ters isshownin Table 3.Since thelikelihood profiles of

δ

_&,

δ

S⊥,

and

|

AS

|

2 are not parabolic, the statistical uncertainties quoted

for these parameters are found from the increase in

−

log

L

by 0.5. In the fit, the value of

"

ms is allowed to vary following a

Gaussian distribution with mean and standard deviation set to

(

17

.

69

±

0

.

08

)

×

1012h

_¯

/

s[32].Asacross-check,the

"

ms valueis

alsoleftfreetofloatanditsbestfitvalueisfoundtobein statis-tical agreementwith thesetvalue. Thevariousdata distributions and the fit projectionsare shownin Figs. 2, 3,and 5. The drop inthecos

θ

T distributionattherangelimits isidentified asbeing

causedby close-by,high-anglekaontracks.Thecentral valueand the68%,90%,and95%confidencelevel(CL)likelihoodcontoursof

thefitinthe

"#

s–

φ

splaneareshownin

Fig. 6

.

Severalsourcesofsystematicuncertaintiesintheprimary mea-sured quantities are investigated by testing the various assump-tions made in the fit model and those associated with the fit procedure.

The systematic uncertainty associatedwith theassumption of aconstantefficiencyas afunctionofct isevaluatedbyfittingthe datawithanalternativectefficiencyparametrisation,whichtakes into account a small contribution of the decaytime significance requirement at small ct and first-order polynomial variations at highct.Thedifferencesfoundinthefitresultswithrespecttothe nominalfitareusedassystematicuncertainties.

The uncertainties associated with the variables cos

θ

T

,

ϕ

T,and

cos

ψ

T ofthe3Dangularefficiencyfunctionarepropagatedtothe

fit results by varying the corresponding parameters within their statisticaluncertainties,accountingforthecorrelationsamongthe parameters. The maximum variation of the parameters extracted fromthefitistakenasthesystematicuncertainty.Thesystematic uncertaintyowingtoasmalldiscrepancyinthekaonpT spectrum

betweendataandsimulationisevaluatedbyweightingtheevents tomakethesimulatedkaonpT spectrummatchthatindata.

Table 3

Correlationmatrixforthestatisticaluncertaintiesinthephysicsfitparameters.

|A0|2 |AS|2 |A⊥|2 δ& δS⊥ δ⊥ cτ "#s φs |A0|2 +1.00 +0.19 −0.64 −0.08 −0.18 −0.02 +0.38 +0.70 +0.11 |AS|2 – +1.00 −0.02 −0.32 −0.79 −0.10 −0.16 +0.01 +0.03 |A_⊥|2 _{– – +1.00 −0.27 +0.03 −0.06 −0.50 −0.77 −0.11} δ& – – – +1.00 +0.26 +0.21 +0.11 +0.03 −0.02 δS⊥ – – – – +1.00 +0.06 +0.11 −0.04 −0.06 δ⊥ – – – – – +1.00 +0.03 +0.01 +0.01 cτ – – – – – – +1.00 +0.55 +0.10 "#s – – – – – – – +1.00 +0.10 φs – – – – – – – – +1.00

Fig. 5. The angulardistributions(cosθT,cosψT, ϕT)oftheB0s candidatesfromdata(solidmarkers).Thesolidlineistheresultofthefit,thedashedlineisthesignal

Fig. 6. TheCMSmeasuredcentralvalueandthe68%,90%,and95%CLcontoursin the"#s versusφs plane,togetherwiththeSMprediction[3,4].Uncertaintiesare statisticalonly.

Theuncertaintyinthectresolutionassociatedwiththe

κ

factor ispropagatedtotheresults.Asetoftestsamplesisproducedwith the

κ

(

ct

)

factor varying within their uncertainty, assumed to be Gaussian.Onestandarddeviationofthedistributiondescribingthe differencebetweenthectresolutionwiththenominalfitandwith a varying

κ

(

ct

)

is taken as the systematic uncertainty. Since the

κ

(

ct

)

factorisobtainedfromsimulation,theassociatedsystematic

uncertainty isassessed by using a sample of prompt J

/ψ

decays obtainedwithanunbiasedtriggerandcomparingthemtosimilarly processed simulated data.In thisway the decay time resolution forct

_≈

0 isobtained.The

κ

(

ct

)

factorisvariedwithinthevalues

observed in data and simulation. The resulting variations of the physicsparametersaretakenassystematicuncertainties.

Although the likelihood function makes use of a per-event mistagparameter, itdoesnot containa pdfmodelforthemistag distribution. The associated systematic uncertainty is estimated bygeneratingsimulatedpseudo-experimentswithdifferentmistag distributionsforsignal andbackgroundandfittingthemwith the nominalfit.

The dominant tagging systematic uncertainty originates from the assumptionthat thesignal and calibration channelshavethe sametaggingperformance.Itisevaluatedusingacalibrationcurve, obtainedfromsimulatedsamples,thatdescribes themistag prob-ability of B0

s as function ofthe mistag probability of B±. The fit

tothedata isrepeated,re-calibrating themistagprobability with the B0

s–B± calibrationcurve, and thedifferences found in the fit

resultswithrespecttothenominalfitareusedas thesystematic uncertainties.

Possiblebiasesintrinsictothefitmodelarealsotakeninto ac-count. The nominal model function is tested by using simulated pseudo-experiments,and the averageofthepulls(defined asthe differencebetweentheresultoffittothepseudo-experiment sam-pleandthenominalvalue)isusedasasystematicuncertaintyifit exceedsonestandarddeviationstatisticaluncertainty.

Thevarioushypothesesthathavebeenassumedwhenbuilding thelikelihoodfunctionaretestedbygeneratingsimulated pseudo-experiments with different hypotheses and fitting the samples withthenominallikelihoodfunction.Theobtainedpullhistograms ofthephysicsvariablesarefittedwithGaussianfunctions,andthe averageofthepullisusedasasystematicuncertaintyifthe differ-ence with respect tothe average exceedsone standard deviation statistical uncertainty.Concerningthemodellingofthe J

/ψ

K+K− invariant mass distribution,the background model ischanged to a Chebyshev function from the nominal exponential pdf. The ct

backgroundpdfischangedtothe sumofthreeexponential func-tionsinstead ofthetwoexponential functionsofthe nominalfit. Theangularbackgroundpdfisgeneratedbyusingthebackground simulationangularshapesinsteadofthefitones.Theeffectofnot includingtheangular resolutionisalso tested, usingthe residual distributions obtained fromsimulations. The RMS of the angular resolutions were found to be 5.9, 6.3, and 10 mrad, for cos

θ

T,

cos

ψ

T,and

ϕ

T respectively.Thecontributiontothesystematic

un-certaintyfromthebackgroundtaggingasymmetryisnegligible. The hypothesis that

|λ|

=

1 is tested by leaving that param-eter free in the fit. The obtained value of

|λ|

is consistent with 1.0withinonestandarddeviation.Thedifferencesfoundinthefit resultswithrespecttothenominalfitareusedas systematic un-certainties.

Thealignmentsystematic uncertaintyaffectsthevertex recon-structionandthereforethedecaytimes.Thateffectisestimatedto be1

.

5 µm fromstudiesofknownBhadronlifetimes[33].The

sys-tematiceffect owing to thevery small numberof B0

s originating

fromB+_c

_→

_B0

s

π

+ feed-down,whichwouldbereconstructedwith

largevaluesofct,hasbeenfoundtobenegligible.

The measured values for the weak phase

φ

s and the decay

widthdifference

"#

sare:

φ

s

= −

0

.

075

±

0

.

097

(

stat

)

±

0

.

031

(

syst

)

rad

,

"#

s

=

0

.

095

±

0

.

013

(

stat

)

±

0

.

007

(

syst

)

ps−1

.

Thesystematicuncertaintiesaresummarisedin

Table 4

.The uncer-taintiesinthe

φ

s and

"#

s resultsaredominatedbythestatistical

uncertainties. Table 4

SummaryoftheuncertaintiesinthemeasurementsofthevariousB0

s parameters.Ifnovalueisreported,thenthesystematicuncertaintyisnegligiblewithrespecttothe

statisticalandothersystematicuncertainties.Thetotalsystematicuncertaintyisthequadraticsumofthelistedsystematicuncertainties.

Source of uncertainty φs[rad] "#s[ps−1] |A0|2 |AS|2 |A⊥|2 δ&[rad] δS⊥[rad] δ⊥[rad] cτ[µm] ctefficiency 0.002 0.0057 0.0015 – 0.0023 – – – 1.0 Angular efficiency 0.016 0.0021 0.0060 0.008 0.0104 0.674 0.14 0.66 0.8 Kaon pTweighting 0.014 0.0015 0.0094 0.020 0.0041 0.085 0.11 0.02 1.1

ctresolution 0.006 0.0021 0.0009 – 0.0008 0.004 – 0.02 2.9 Mistag distribution modelling 0.004 0.0003 0.0006 – – 0.008 0.01 – 0.1 Flavour tagging 0.003 0.0003 – – – 0.006 0.02 – – Model bias 0.015 0.0012 0.0008 – – 0.025 0.03 – 0.4 pdf modelling assumptions 0.006 0.0021 0.0016 0.002 0.0021 0.010 0.03 0.04 0.2

|λ|as a free parameter 0.015 0.0003 0.0001 0.005 0.0001 0.002 0.01 0.03 –

Tracker alignment – – – – – – – – 1.5

Total systematic uncertainty 0.031 0.0070 0.0114 0.022 0.0116 0.680 0.18 0.66 3.7 Statistical uncertainty 0.097 0.0134 0.0053 0.008 0.0075 0.081 0.17 0.36 2.9

7. Summary

Using pp collision data collected by the CMS experiment at a centre-of-mass energyof 8 TeV and corresponding to an inte-grated luminosity of 19

.

7 fb−1, 49 200 B0

s

→

J

/ψ φ (

1020

)

signal

candidates wereusedtomeasure theweakphase

φ

s and the

de-cay width difference

"#

s. The analysis was performed by using

opposite-side lepton tagging of the B0

s flavour atthe production

time.Bothmuonandelectrontagswereused.

The measuredvaluesfortheweakphaseand thedecaywidth difference between the B0

s mass eigenstates are

φ

s

= −

0

.

075

±

0

.

097

(

stat

)

±

0

.

031

(

syst

)

rad and

"#

s

=

0

.

095

±

0

.

013

(

stat

)

±

0

.

007

(

syst

)

ps−1, respectively. The measured values are

consis-tent with those obtained by the LHCb Collaboration using B0

s

→

J

/ψ

K+K−decays[34].

Ourmeasured value of

φ

s agrees with theSM prediction. Our

result confirms

"#

s tobe nonzero, with a value consistent with

theoreticalpredictions.Theuncertaintiesinour

φ

s and

"#

s

mea-surements are dominatedby statistical uncertainties. Ourresults provideindependentreference measurementsof

φ

s and

"#

s,and

contribute to improving the overall precision of these quantities andtherebyprobingtheSMfurther.Sinceourmeasurement preci-sion isstilllimitedbystatistical uncertainty,substantial improve-mentisexpectedfromLHC

√

s

₌

13TeV high-luminosityrunning thatwillbeavailableoverthenextfewyears.

Acknowledgements

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technical and administrativestaffsatCERN and atother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentresand personneloftheWorldwideLHCComputingGridfordeliveringso effectively thecomputing infrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tion and operationoftheLHC and theCMSdetectorprovidedby thefollowingfundingagencies:BMWFWandFWF(Austria);FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES(Bulgaria);CERN;CAS,MOST,andNSFC(China);COLCIENCIAS (Colombia);MSESandCSF(Croatia);RPF(Cyprus);MoER,ERCIUT and ERDF(Estonia);Academy ofFinland,MEC,and HIP(Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia); CINVESTAV, CONACYT,SEP,andUASLP-FAI(Mexico);MBIE(NewZealand);PAEC (Pakistan);MSHEand NSC(Poland);FCT(Portugal);JINR(Dubna); MON,RosAtom,RASandRFBR(Russia);MESTD(Serbia);SEIDIand CPAN(Spain);SwissFundingAgencies(Switzerland);MST(Taipei); ThEPCenter,IPST, STARandNSTDA(Thailand);TUBITAKand TAEK (Turkey);NASU andSFFR(Ukraine); STFC(United Kingdom);DOE andNSF(USA).

Individuals have received support from the Marie-Curie pro-gramme and theEuropean ResearchCouncil and EPLANET (Euro-peanUnion);theLeventisFoundation;theAlfredP.Sloan Founda-tion; the Alexander von Humboldt Foundation; the Belgian Fed-eral Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technolo-gie (IWT-Belgium); the Ministry of Education, Youth and Sports (MEYS)oftheCzechRepublic;theCouncilofScienceandIndustrial Research,India;the HOMINGPLUSprogramme oftheFoundation forPolish Science,cofinancedfromEuropean Union,Regional De-velopment Fund; the Compagniadi SanPaolo (Torino); the

Con-sorzio per la Fisica (Trieste); MIUR project 20108T4XTM (Italy); theThalisandAristeiaprogrammescofinancedbyEU-ESFandthe Greek NSRF; the National Priorities Research Program by Qatar National ResearchFund;theRachadapisek SompotFund for Post-doctoral Fellowship,ChulalongkornUniversity (Thailand);and the WelchFoundation.

References

[1] B.Bhattacharya,A.Datta,D.London,Reducingpenguinpollution,Int.J.Mod. Phys.A28(2013)1350063,http://dx.doi.org/10.1142/S0217751X13500632. [2] S.Faller,R.Fleischer,T. Mannel,Precisionphysics with B0

s→J/ψ φ at the

LHC:thequestfornewphysics,Phys.Rev.D79(2009)014005,http://dx.doi. org/10.1103/PhysRevD.79.014005,arXiv:0810.4248.

[3] J.Charles,O. Deschamps, S. Descotes-Genon, R.Itoh, H. Lacker,A.Menzel, S. Monteil, V.Niess,J. Ocariz, J. Orloff,S. T’Jampens, V. Tisserand,K. Tra-belsi,Predictionsofselectedflavourobservableswithinthestandardmodel, Phys.Rev.D84(2011)033005,http://dx.doi.org/10.1103/PhysRevD.84.033005, arXiv:1106.4041.

[4]A.Lenz,U.Nierste,Numericalupdatesoflifetimesandmixingparametersof Bmesons,in:T.Gershon(Ed.),Proceedingsofthe6thInternationalWorkshop on the CKM Unitarity Triangle, University of Warwick, United Kingdom, 2010, arXiv:1102.4274.

[5] T. Aaltonen, et al., CDF Collaboration, First flavor-tagged determination of boundsonmixing-inducedCPviolationinB0

s→J/ψ φdecays,Phys.Rev.Lett. 100 (2008) 161802, http://dx.doi.org/10.1103/PhysRevLett.100.161802, arXiv: 0712.2397.

[6] V.M.Abazov,etal.,D0Collaboration,MeasurementofB0

s mixingparameters fromtheflavor-taggeddecayB0

s→J/ψ φ,Phys.Rev.Lett.101(2008)241801,

http://dx.doi.org/10.1103/PhysRevLett.101.241801,arXiv:0802.2255.

[7] T.Aaltonen,etal.,CDFCollaboration,MeasurementoftheCP-violatingphase

βsJ/ψ φ inB0s→J/ψ φdecayswiththeCDFIIdetector,Phys.Rev.D85(2012)

072002,http://dx.doi.org/10.1103/PhysRevD.85.072002,arXiv:1112.1726. [8] V.M.Abazov,etal.,D0Collaboration,MeasurementoftheCP-violatingphase

φJs/ψ φusingtheflavor-taggeddecayBs0→J/ψ φin8 fb−1ofpp collisions,Phys. Rev.D85(2012)032006,http://dx.doi.org/10.1103/PhysRevD.85.032006,arXiv: 1109.3166.

[9] LHCb Collaboration, Measurement of the CP-violating phase φs in B0s → J/ψπ+π− decays, Phys. Lett. B 736 (2014) 186, http://dx.doi.org/10.1016/ j.physletb.2014.06.079,arXiv:1405.4140.

[10] LHCb Collaboration, Measurement of CP violation and the B0

s meson de-cay width difference with B0

s →J/ψK+K− and B0s →J/ψπ+π− decays, Phys.Rev.D87(2013)112010,http://dx.doi.org/10.1103/PhysRevD.87.112010, arXiv:1304.2600.

[11] LHCb Collaboration, Measurement of the CP-violating phase φs in B0s → J/ψπ+π− decays, Phys. Lett. B 713 (2012) 378, http://dx.doi.org/10.1016/ j.physletb.2012.06.032,arXiv:1204.5675.

[12] ATLAS Collaboration, Time-dependent angular analysis of the decay B0 s→ J/ψ φ and extractionof"#s andtheCP-violatingweakphaseφs byATLAS, J. HighEnergyPhys.12(2012)072,http://dx.doi.org/10.1007/JHEP12(2012)072, arXiv:1208.0572.

[13] ATLAS Collaboration, Flavortagged time-dependent angular analysisof the B0

s→J/ψ φdecayandextractionofδγsandtheweakphaseφsinATLAS,Phys. Rev.D90(2014)052007,http://dx.doi.org/10.1103/PhysRevD.90.052007. [14] A.S.Dighe,I.Dunietz,R.Fleischer,ExtractingCKMphasesandB0

s− ¯Bsmixing parametersfromangulardistributionsofnon-leptonicBdecays,Eur.Phys.J.C 6(1999)647,http://dx.doi.org/10.1007/s100529800954,arXiv:hep-ph/9804253. [15] A.S.Dighe,I. Dunietz,H.J.Lipkin,J.L.Rosner,Angulardistributionsand

life-timedifferencesinB0

s→J/ψ φdecays,Phys.Lett.B369(1996)144,http://dx.

doi.org/10.1016/0370-2693(95)01523-X,arXiv:hep-ph/9511363.

[16]G.Branco,L.Lavoura,J.Silva,CPViolation,Int.Ser.Monogr. Phys.,vol. 103, Clarendon Press, Oxford, 1999.

[17] LHCbCollaboration,Measurementoftheflavour-specificCP-violating asymme-tryas

sl inB0s decays,Phys.Lett.B728(2014)607,http://dx.doi.org/10.1016/

j.physletb.2013.12.030,arXiv:1308.1048.

[18] CMS Collaboration, Description and performance of track and primary-vertex reconstruction with the CMS tracker, J. Instrum. 9(2014) P10009,

http://dx.doi.org/10.1088/1748-0221/9/10/P10009,arXiv:1405.6569.

[19] CMSCollaboration,PerformanceofCMSmuonreconstructioninpp collision eventsat √s₌7TeV,J.Instrum.7(2012)P10002,http://dx.doi.org/10.1088/ 1748-0221/7/10/P10002,arXiv:1206.4071.

[20] CMSCollaboration,TheCMSexperimentattheCERNLHC,J.Instrum.3(2008) S08004,http://dx.doi.org/10.1088/1748-0221/3/08/S08004.

[21] ParticleDataGroup,K.A.Olive,etal.,Reviewofparticlephysics,Chin.Phys.C 38(2014)090001,http://dx.doi.org/10.1088/1674-1137/38/9/090001. [22] T.Sjöstrand,S.Mrenna,P.Z.Skands,PYTHIA6.4physicsandmanual,J.High

EnergyPhys.05(2006)026,http://dx.doi.org/10.1088/1126-6708/2006/05/026, arXiv:hep-ph/0603175.

[23] D.J.Lange,TheEvtGenparticledecaysimulationpackage,Nucl.Instrum. Meth-odsPhys.Res.,Sect.A,Accel.Spectrom.Detect.Assoc.Equip.462(2001)152,

http://dx.doi.org/10.1016/S0168-9002(01)00089-4.

[24] E.Barberio,B.vanEijk,Z.Was,PHOTOS–auniversalMonte Carlo forQED ra-diativecorrectionsindecays,Comput.Phys.Commun.66(1991)115,http://dx. doi.org/10.1016/0010-4655(91)90012-A.

[25] E.Barberio,Z.W ˛as,PHOTOS–auniversalMonteCarloforQEDradiative cor-rections:version2.0,Comput.Phys.Commun.79(1994)291,http://dx.doi.org/ 10.1016/0010-4655(94)90074-4.

[26] S.Agostinelli,etal.,GEANT4Collaboration,GEANT4—asimulationtoolkit,Nucl. Instrum.MethodsPhys.Res.,Sect.A,Accel.Spectrom.Detect.Assoc.Equip.506 (2003)250,http://dx.doi.org/10.1016/S0168-9002(03)01368-8.

[27] CMSCollaboration,Particle–floweventreconstructioninCMSandperformance forjets,taus,andEmiss

T ,CMSPhysicsAnalysisSummaryCMS-PAS-PFT-09-001,

http://cdsweb.cern.ch/record/1194487,2009.

[28] CMSCollaboration, Commissioningofthe particle-flowevent reconstruction withthefirstLHCcollisionsrecordedintheCMSdetector,CMSPhysics Anal-ysis Summary CMS-PAS-PFT-10-001, http://cdsweb.cern.ch/record/1247373, 2010.

[29] H.Voss,A.Höcker,J. Stelzer,F. Tegenfeldt,TMVA,thetoolkitfor multivari-ate dataanalysiswith ROOT,in: XIthInternationalWorkshopon Advanced ComputingandAnalysisTechniquesinPhysicsResearch(ACAT),2007,p. 40,

http://pos.sissa.it/archive/conferences/050/040/ACAT_040.pdf, arXiv:physics/ 0703039.

[30] I.Antcheva,etal.,ROOT—AC++frameworkforpetabytedatastorage, sta-tisticalanalysisandvisualization,Comput.Phys.Commun.180 (2009)2499,

http://dx.doi.org/10.1016/j.cpc.2009.08.005.

[31] LHCb Collaboration, Determination of the sign of the decay width differ-enceintheB0

s system,Phys.Rev.Lett.108(2012)241801,http://dx.doi.org/

10.1103/PhysRevLett.108.241801,arXiv:1202.4717.

[32] ParticleDataGroup,J.Beringer,etal.,Reviewofparticlephysics,Phys.Rev.D 86(2012)010001,http://dx.doi.org/10.1103/PhysRevD.86.010001.

[33] CMS_√ Collaboration, Measurement of the 40_b lifetime in pp collisions at s₌7TeV, J. High Energy Phys. 07(2013) 163,http://dx.doi.org/10.1007/ JHEP07(2013)163.

[34] LHCb Collaboration, Precision measurement of CP violation in B0 s → J/ψk+_k−_{decays,Phys.Rev.Lett.114(2015)041801,http://dx.doi.org/10.1103/} PhysRevLett.114.041801,arXiv:1411.3104.

CMSCollaboration

V. Khachatryan,

A.M. Sirunyan,

A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam,

E. Asilar,

T. Bergauer,

J. Brandstetter,

E. Brondolin,

M. Dragicevic,

J. Erö,

M. Flechl,

M. Friedl,

R. Frühwirth

1

,

V.M. Ghete,

C. Hartl,

N. Hörmann,

J. Hrubec,

M. Jeitler

1

,

V. Knünz,

A. König,

M. Krammer

1

,

I. Krätschmer,

D. Liko,

T. Matsushita,

I. Mikulec,

D. Rabady

2

,

B. Rahbaran,

H. Rohringer,

J. Schieck

1

_,

_{R. Schöfbeck,}

_{J. Strauss,}

_{W. Treberer-Treberspurg,}

_{W. Waltenberger,}

_{C.-E. Wulz}

1

InstitutfürHochenergiephysikderOeAW,Wien,Austria

V. Mossolov,

N. Shumeiko,

J. Suarez Gonzalez

NationalCentreforParticleandHighEnergyPhysics,Minsk,Belarus

S. Alderweireldt,

T. Cornelis,

E.A. De Wolf,

X. Janssen,

A. Knutsson,

J. Lauwers,

S. Luyckx,

S. Ochesanu,

R. Rougny,

M. Van De Klundert,

H. Van Haevermaet,

P. Van Mechelen,

N. Van Remortel,

A. Van Spilbeeck

UniversiteitAntwerpen,Antwerpen,Belgium

S. Abu Zeid,

F. Blekman,

J. D’Hondt,

N. Daci,

I. De Bruyn,

K. Deroover,

N. Heracleous,

J. Keaveney,

S. Lowette,

L. Moreels,

A. Olbrechts,

Q. Python,

D. Strom,

S. Tavernier,

W. Van Doninck,

P. Van Mulders,

G.P. Van Onsem,

I. Van Parijs

VrijeUniversiteitBrussel,Brussel,Belgium

P. Barria,

H. Brun,

C. Caillol,

B. Clerbaux,

G. De Lentdecker,

H. Delannoy,

G. Fasanella,

L. Favart,

A.P.R. Gay,

A. Grebenyuk,

G. Karapostoli,

T. Lenzi,

A. Léonard,

T. Maerschalk,

A. Marinov,

L. Perniè,

A. Randle-conde,

T. Reis,

T. Seva,

C. Vander Velde,

P. Vanlaer,

R. Yonamine,

F. Zenoni,

F. Zhang

3

UniversitéLibredeBruxelles,Bruxelles,Belgium

K. Beernaert,

L. Benucci,

A. Cimmino,

S. Crucy,

D. Dobur,

A. Fagot,

G. Garcia,

M. Gul,

J. Mccartin,

A.A. Ocampo Rios,

D. Poyraz,

D. Ryckbosch,

S. Salva,

M. Sigamani,

N. Strobbe,

M. Tytgat,

W. Van Driessche,

E. Yazgan,

N. Zaganidis

GhentUniversity,Ghent,Belgium

S. Basegmez,

C. Beluffi

4

,

O. Bondu,

S. Brochet,

G. Bruno,

R. Castello,

A. Caudron,

L. Ceard,

V. Lemaitre,

A. Mertens,

C. Nuttens,

L. Perrini,

A. Pin,

K. Piotrzkowski,

A. Popov

6

,

L. Quertenmont,

M. Selvaggi,

M. Vidal Marono

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

N. Beliy,

G.H. Hammad

UniversitédeMons,Mons,Belgium

W.L. Aldá Júnior,

G.A. Alves,

L. Brito,

M. Correa Martins Junior,

M. Hamer,

C. Hensel,

C. Mora Herrera,

A. Moraes,

M.E. Pol,

P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

E. Belchior Batista Das Chagas,

W. Carvalho,

J. Chinellato

7

,

A. Custódio,

E.M. Da Costa,

D. De Jesus Damiao,

C. De Oliveira Martins,

S. Fonseca De Souza,

L.M. Huertas Guativa,

H. Malbouisson,

D. Matos Figueiredo,

L. Mundim,

H. Nogima,

W.L. Prado Da Silva,

A. Santoro,

A. Sznajder,

E.J. Tonelli Manganote

7

_,

_{A. Vilela Pereira}

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

S. Ahuja

a

,

C.A. Bernardes

b

,

A. De Souza Santos

b

,

S. Dogra

a

,

T.R. Fernandez Perez Tomei

a

,

E.M. Gregores

b

_,

_{P.G. Mercadante}

b

_,

_{C.S. Moon}

a

,

8

_,

_{S.F. Novaes}

a

_,

_{Sandra S. Padula}

a

_,

_{D. Romero Abad,}

J.C. Ruiz Vargas

a_{UniversidadeEstadualPaulista,SãoPaulo,Brazil} b_{UniversidadeFederaldoABC,SãoPaulo,Brazil}

A. Aleksandrov,

R. Hadjiiska,

P. Iaydjiev,

M. Rodozov,

S. Stoykova,

G. Sultanov,

M. Vutova

InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria

A. Dimitrov,

I. Glushkov,

L. Litov,

B. Pavlov,

P. Petkov

UniversityofSofia,Sofia,Bulgaria

M. Ahmad,

J.G. Bian,

G.M. Chen,

H.S. Chen,

M. Chen,

T. Cheng,

R. Du,

C.H. Jiang,

R. Plestina

9

,

F. Romeo,

S.M. Shaheen,

J. Tao,

C. Wang,

Z. Wang,

H. Zhang

InstituteofHighEnergyPhysics,Beijing,China

C. Asawatangtrakuldee,

Y. Ban,

Q. Li,

S. Liu,

Y. Mao,

S.J. Qian,

D. Wang,

Z. Xu,

W. Zou

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

C. Avila,

A. Cabrera,

L.F. Chaparro Sierra,

C. Florez,

J.P. Gomez,

B. Gomez Moreno,

J.C. Sanabria

UniversidaddeLosAndes,Bogota,Colombia

N. Godinovic,

D. Lelas,

I. Puljak,

P.M. Ribeiro Cipriano

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia

Z. Antunovic,

M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,

K. Kadija,

J. Luetic,

S. Micanovic,

L. Sudic

InstituteRudjerBoskovic,Zagreb,Croatia

A. Attikis,

G. Mavromanolakis,

J. Mousa,

C. Nicolaou,

F. Ptochos,

P.A. Razis,

H. Rykaczewski

UniversityofCyprus,Nicosia,Cyprus

M. Bodlak,

M. Finger

10

,

M. Finger Jr.

10 CharlesUniversity,Prague,CzechRepublic

M. El Sawy

11

,

12

_,

_{E. El-khateeb}

13

_,

_{T. Elkafrawy}

13

_,

_{A. Mohamed}

14

_,

_{A. Radi}

12

,

13

_,

_{E. Salama}

12

,

13

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

B. Calpas,

M. Kadastik,

M. Murumaa,

M. Raidal,

A. Tiko,

C. Veelken

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,

J. Pekkanen,

M. Voutilainen

DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

J. Härkönen,

T. Jarvinen,

V. Karimäki,

R. Kinnunen,

T. Lampén,

K. Lassila-Perini,

S. Lehti,

T. Lindén,

P. Luukka,

T. Mäenpää,

T. Peltola,

E. Tuominen,

J. Tuominiemi,

E. Tuovinen,

L. Wendland

HelsinkiInstituteofPhysics,Helsinki,Finland

J. Talvitie,

T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,

F. Couderc,

M. Dejardin,

D. Denegri,

B. Fabbro,

J.L. Faure,

C. Favaro,

F. Ferri,

S. Ganjour,

A. Givernaud,

P. Gras,

G. Hamel de Monchenault,

P. Jarry,

E. Locci,

M. Machet,

J. Malcles,

J. Rander,

A. Rosowsky,

M. Titov,

A. Zghiche

DSM/IRFU,CEA/Saclay,Gif-sur-Yvette,France

I. Antropov,

S. Baffioni,

F. Beaudette,

P. Busson,

L. Cadamuro,

E. Chapon,

C. Charlot,

T. Dahms,

O. Davignon,

N. Filipovic,

A. Florent,

R. Granier de Cassagnac,

S. Lisniak,

L. Mastrolorenzo,

P. Miné,

I.N. Naranjo,

M. Nguyen,

C. Ochando,

G. Ortona,

P. Paganini,

P. Pigard,

S. Regnard,

R. Salerno,

J.B. Sauvan,

Y. Sirois,

T. Strebler,

Y. Yilmaz,

A. Zabi

LaboratoireLeprince-Ringuet,EcolePolytechnique,IN2P3-CNRS,Palaiseau,France

J.-L. Agram

15

,

J. Andrea,

A. Aubin,

D. Bloch,

J.-M. Brom,

M. Buttignol,

E.C. Chabert,

N. Chanon,

C. Collard,

E. Conte

15

,

X. Coubez,

J.-C. Fontaine

15

,

D. Gelé,

U. Goerlach,

C. Goetzmann,

A.-C. Le Bihan,

J.A. Merlin

2

,

K. Skovpen,

P. Van Hove

InstitutPluridisciplinaireHubertCurien,UniversitédeStrasbourg,UniversitédeHauteAlsaceMulhouse,CNRS/IN2P3,Strasbourg,France

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,

C. Bernet,

G. Boudoul,

E. Bouvier,

C.A. Carrillo Montoya,

R. Chierici,

D. Contardo,

B. Courbon,

P. Depasse,

H. El Mamouni,

J. Fan,

J. Fay,

S. Gascon,

M. Gouzevitch,

B. Ille,

F. Lagarde,

I.B. Laktineh,

M. Lethuillier,

L. Mirabito,

A.L. Pequegnot,

S. Perries,

J.D. Ruiz Alvarez,

D. Sabes,

L. Sgandurra,

V. Sordini,

M. Vander Donckt,

P. Verdier,

S. Viret,

H. Xiao

UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France

T. Toriashvili

16

GeorgianTechnicalUniversity,Tbilisi,Georgia

Z. Tsamalaidze

10