Measurements of the CKM angle g in tree-dominated decays at LHCb

Measurements of the CKM angle g in tree-dominated decays at LHCb

Stefania Ricciardi(STFC Rutherford Appleton Laboratory)

on behalf of the LHCb Collaboration

Hadron Collider Physics Symposium, Kyoto, November 12-16, 2012

Stefania Ricciardi 2

OutlineA very productive year for g at LHCb!

Results from time-integrated methods B+ D(KK,pp,Kp)K+ [PLB 712(2012),213] B+ D(Kppp)K+ [LHCB-CONF-2012-030] B+ D(KSpp,KSKK)K+ [PLB 718(2012) 43]

First g average from LHCb [LHCB-CONF-2012-032] First measurements with neutral B decays

B0 D(KK,Kp)K*0 [LHCB-CONF-2012-024]

First time-dependent measurements B0

sDS K± [LHCB-CONF-2012-029]

Other promising multibody decays first observation B0

sDS K ± p+p-

[LHCB-PAPER-2012-033]

All results based on 1 fb-1 (2011 data-set)

14/11/2012


Precision on , g a path to NP discovery

CKM fits: overall a triumph for SM! However, a few tensions exist More precision needed to unravel subtle

NP effects

g at tree-level largely unaffected by NP, essentially no theoretical uncertainties

g still least-well measured angle of the UT

14/11/2012

66 ± 12 CKMFITTER72 ± 9 UTFIT

g from tree-level decays: theoretically very clean, but experimentally very challenging![Zupan, arXiv:1101.0134]

Post-ICHEP 2012 average using BaBar, Belle, CDF and first LHCB results

fD H

D0H

D0H

B

g from trees: time-integrated methods

14/11/2012 Stefania Ricciardi 4

Sensitivity to g through interference of b → c and b → u tree-level amplitudes Interference requires D0 and D0 decay to common final state fD

D0 GLW -CP eigenstates: KK, pp [Gronau-London-Wyler]PLB 253,483(1991), PLB 265,172 1991)

ADS- Quasi-flavour-specific: Kp, Kppp [Atwood-Dunietz-Soni] PRL 78,257(1997), PRD 63,036005 (2001)

GGSZ - Self-conjugate 3-body : KSpp, KSKK [Giri-Grossman-Soffer-Zupan] PRD 68,054018(2003)Bondar,PRD 70,072003 (2004)

Vcb

Favoured

B-

Suppressed

B-

Vub

)( BiBer

DiDer

D0

H-

H-

u u

u u

D0

H Expected rB

K 0.1 p 0.005Naïve assumptions , charged B decays only

Hadronic unknowns: rB, dB

rD , dD All from data No hadronic uncertaintiesMethod to extract them depends on D decay


Experimental challenges

14/11/2012

Large data samplededicated triggerEfficient retention of fully hadronic B decays while limiting the overall output <5KHz

Precision @VERTEXLHCB Vertex detector and trackingExcellent invariant mass resolution Excellent vertex resolution

Mass resolution and displaced vertices for separation from low-mass background and rejection of combinatorial background

PID : 2 RICH detectors @LHCb K-p separation over 2—100GeV/c

Effectively separate B→DK from10x more abundant B→Dp

KS reconstruction(specific to GGSZ mode)About 2/3 of KS decay downstream of vertex detector


GLW with B+→D(hh)K+

14/11/2012

coscos21

sinsin2

)()(

)()(2

BBB

BB

CPCP

CPCPCP rr

r

KDBKDB

KDBKDBA

ACP+ (KK)= (-14.8 ± 3.7 ± 1.0)% ACP+ (pp)= (-13.5 ± 6.6 ± 1.0)%

DCP H

D0H

D0H

B

B±DK± : clear asymmetryB± Dp± : no significant asymmetry

Evidence of non-zero ACP+ in B±DK± with 4.5 s significance (KK+pp)

coscos21)()(

)()(2 2

00 BBBCPCP

CP rrKDBKDB

KDBKDBR

B±DK±

B± Dp±

[PLB 712(2012),213]


ADS with B+→D(Kp)K+

14/11/2012

Large asymmetry in BDK : AADS = (-52 ± 15 ± 2)% [4 ]s

Hint of asymmetry in BDp: AADS = (14.3 ± 6.2 ± 1.1)% [2.4s]

First observation of rare ADS OS B+ D(K-p+)K +

(Opposite Sign kaons) [10s]

(K-p+) H+

D0H

D0H

B+

CF DCS

DKADSDBDB

DD

DDDKADS

DBDBDBDD

DDDKADS

RrrKKKK

KKKKA

rrrrKKKK

KKKKR

/)sin(sin2)]([)]([

)]([)]([

)cos(cos2)]([)]([

)]([)]([ 22


GLW and ADS with B+→D(Kp)K+

14/11/2012

GLW ADS

LHCb results on ADS and GLW observables more precise than B-factories and Tevatron results


ADS with B+→D(K3p)K+

14/11/2012

First observation of rare ADS mode in BDK [5.1s] and BDp [>10s]

ADS

KDBK

KDB

ADS R

Rrr

KKDBKKDB

KKDBKKDBA

sin)sin(2

))3(())3((

))3(())3(( 33

3

CLEO-cPRD 0031105(2009)

Hint of asymmetry in BDK: AADS = (-42 ± 22 )%

BDp: AADS = (13 ± 10 )%

Same rB and dB, but different D decay parametersComplementary information to B D(Kp)K not just additional statistics

RADS (K) = (1.24 ± 0.27 )% RADS (p) = (0.369 ± 0.036 )%

[LHCB-CONF-2012-030]


GGSZ: g from B+→D(KSh+h-)K+

14/11/2012

Exploits interference pattern in the D→KSh+h- Dalitz plots (different for B+ and B-)

Extraction of g requires information on the D→KShh decay amplitude variation over Dalitz plot: both magnitude and phase dD

1. model of decay amplitude or2. external measurements (model independent approach)

Rich resonance structure powerful method (dominates precision on g from B-factories)

DKSp+p-

690 signal events

DKSK+K-

110 signal events

B+ B-

B+ B-

m± = m(KSh ±)

m+ (G

eV2 /

c4 )m

+ (G

eV2 /

c4 )

[PLB 718(2012) 43]


GGSZ: binned approach

14/11/2012

}{2)()( 22iiiiiii sycxKKKyxKBN

Use discrete measurements of dD in Dalitz plot bins from CLEO-c: ci,si [PRD82(2010)112006]

Ki = i |AD(m+ 2,m-

2)|2 dm+2dm-

2

from flavour specific D decaysiDic cos iDis sin

x±,y± extracted from a simultaneous fit to the signal yields in each Dalitz-plot bin

Chosen binning optimise g sensitivity

KSKK sample adds just 2 bins

DKSp+p- DKSK+K-

)sin(

)cos(

BB

BB

ry

rx


GGSZ results

14/11/2012

Likelihood scan (statistical error only)

x+ = (-10.3 ± 4.4 ± 1.8 ± 1.4) x 10-2

y+ = (-0.9 ± 3.7 ± 0.8 ± 3.0) x 10-2 x- = (0.0 ± 4.3 ± 1.5 ± 0.6) x 10-2

y- = (2.7 ± 5.2 ± 0.8 ± 2.3) x 10-2

Uncertainties: 1. Statistical2. Experimental systematic3. CLEO-c inputs

Leading source of experimental systematic uncertainty: assumption of no CPV in BD pused to determine efficiency

Results on x,y have similar precision to those from BaBar and Belle

Lower rB implies larger uncertainty on g compared to B-factories from this mode

g = (44 +43 -38) ⁰

rB = 0.07 ± 0.04(0,0)rB

rB2g

[PLB 718(2012) 43]


Combination of B+→DK+ results

14/11/2012

Precision achieved by combination of GLW, ADS and GGSZ measurements Frequentist method adopted using LHCb only results + constraints on D parameters from CLEO-c

< > = 71.1 g +16.1-15.2

()

<rB > = 0.092 ± 0.008

<dB> = 112.0 +12.6-15.5 ()

[43.9 – 98.8] @ 95%C.L.


Comparable precision to g averagesfrom BaBar and Belle

BaBar : < > = 69 g +17 -16

() Belle : < > = 68 g +15

-14

()


Including B+Dp+ in the g average

14/11/2012

g, rBp and dB

p from combination of B+Dp+ GLW and ADS results only

B+→DK+ and B+→Dp+

[43.8 – 101.5] @ 95%C.L.

< > g [61.8-67.8] [77.9-92.4] @ 68%C.L.

Non-Gaussian behaviour Impact on best-fit value: 71 85 (<1s) 95% confidence level essentially unchanged

g

rB( )p

dB(p)


GLW with B0 →D(KK)K*0

14/11/2012

Self-tagged mode time-integrated methods similar to B+ D(hh)K+

Interfering diagrams both colour suppressed: Larger rB (3x) larger interference Low yields

B0

Bs

B

Bs

D0D0 b u

sd

c

d

b c

sd

u

d K(*)0 K(*)0B0 B0

Vcb Vub

Hint of large asymmetry in B0DK0* : AdCP+ = (-47 ± 25 ± 2)%

No significant asymmetry in BsDK*0 : AsCP+ = (4 ± 17 ± 1)%



Bs→Ds

K: time-dependent method

14/11/2012

Two final states: Ds

+K- and Ds-K+

Both accessible to Bs and Bs

CPV in decay w & w/out mixing sensitive to -2g bs

Time-dependent analysis and flavour tagging requiredUnique to LHCb

CP sensitivity in Stagged events only

CP sensitivity in Dthanks to DGs 0 untagged&tagged events

b→c b→u

)]sin()cos()2

sinh()2

[cosh()(

)]sin()cos()2

sinh()2

[cosh()(

tmStmCt

Dt

edt

td

tmStmCt

Dt

edt

td

sfss

fstfB

sfss

fstfB

ss

ss

2

2

1

1

KD

KD

s

s

r

rC

21

))2(cos(2

KD

sDsKf

sr

rD

rDsK ~0.4

relative magnitude of the CKM-suppressed to CKM-favoured amplitudes

21

))2(sin(2

KD

sDsKf

sr

rS

+ other2 equations for f

ff

ff

DD

SS

C

,

,

:sObservable 5


Bs→Ds

K : analysis ingredients

14/11/2012

Tagging:OS only used in this first analysis, eD2=1.9%

Proper time acceptance:a,b,n,b from fit to BsDs p data

Precision tracking and PID: for background suppressionB mass fit: statistical separation of signal from remaining background

Signal yield = 1390±98

Bs DsKDs KK p / /ppp Kpp

<st>~50 fs

Proper time resolution:from MC corrected for data/MC differences

psttbat

tan

2.0)1()(1(

11)(


Bs→Ds

K : time-dependent analysis results

14/11/2012

First measurement of the CP parameters in Bs→Ds K

Extraction of g sensitive to correlations: work in progress to determine systematic error covariance matrix Includes both tagged (40%) and untagged (60%) events

Main systematic uncertainties:fixed parameters (Gs, DGs, Dms, acceptance); tagging calibration



More under way: Bs→Ds

K p+p-

14/11/2012

Bs→Ds

K p+p-

can also be used to measure -2g bs

with TD analysis (similar to Bs→Ds

K )Bs and B0

→DsKpp (first observation)

First step: measurement of the branching fractions

Selected Ds decays only: Ds K*K and DsfpExpect yield 40% of Bs→Ds

K

when other Ds modes added and selection tuned for CP analysis

ArXiv:1211.1541 NEW


Conclusions First results on g from GLW/ADS/GGSZ measurements at LHCb

No single method dominates sensitivity

Combined measurement from B+ →DK+ decays (1/fb, 2011 data sample)

similar precision to Belle and Babar

First results from other sensitive modes

B0 →D(KK)K*0 first observation

B+→D (hh)K+p+p- first observation

Bs→Ds

K

Bs→Ds

K p+p- first observation

will provide additional measurements of g with 2011+2012 data sample

Additional g-sensitive B+,B0, Bs, Lb decays under study

Excellent prospects for big improvements on g precision from tree-dominated decays!

14/11/2012

< >g = 71.1 +16.1-15.2 ()

Stefania Ricciardi 2114/11/2012

Thank You

Kyoto, HCP2012 < >g = 71.1 +16.1

-15.2 ()from tree decays [B+ →DK+ only]

…and Thanks to Nature for these beautiful trees!


GLW-like with B+→D K+p+p-

14/11/2012

First observation of B+DK+p+p-

with D CP eigenstates and first measurement of CP observables (GLW)

Larger data-samples needed to perform ADS analysis andconstrain g from these decays



GGSZ

14/11/2012

Sum of B+ and B- yieldsDifference of B+ and B- yields

Measurements of the CKM angle g in tree-dominated decays at LHCb

Documents

Transcript of Measurements of the CKM angle g in tree-dominated decays at LHCb