LHCb-Babar Meeting 8 April 2005.

LHCb-Babar MeetingLHCb-Babar Meeting8 April 2005.8 April 2005.

Paul SolerUniversity of Glasgow and

Rutherford Appleton Laboratory

A first look at BA first look at Bss→→J/J/ in in LHCbLHCb

A first look at BA first look at Bss→→J/J/ in in LHCbLHCb

LHCb-Babar Meeting, 4 April 2005

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ContentsContents1.1. MotivationMotivation

2.2. Physics aimsPhysics aims

3.3. Angle Angle from Bs →J/

4. LHCb Experiment

5. Analysis of Bs →J/

6. Toy Monte Carlo

7. Sensitivity

8. New Physics

9. Conclusions

Work carried out in

collaboration with:

Stuart Paterson (Glasgow)

Andrew Pickford (Glasgow)

Borrowed from:

G. Raven’s analysis in 2003


3

MotivationMotivation BBss → J/ → J/ is the “gold plated” decay mode in the Bs

system, similar to the BBdd → J/ → J/ss in the Bd system This mode is theoretically clean (very small penguin

contributions). It provides a measurement of the unitarity angle ,

which is predicted to be very small (~0.02) in the SM. Sensitive to new physics Exploits the production capabilities of Bs mesons at the

LHC (not available at B-factories) Exploits UK investment in the RICH and VELO detectors


4

Physics aimsPhysics aims CKM matrix:

CKM matrix provides link between mass eigenstates and weak eigenstatesijijijij

CKM

sandcwhere

cs

sc

iδecs

sccs

sc

V

sin,cos

0

010

0

00

010

001

0

0

001

100

0

0

1313

1313

2323

23231212

1212

b

s

d

V

b

s

d

CKM

'

'

'

132313231223121323122312

132313231223121323122312

1313121312

ccescsscesccss

csesssccessccs

escscc

VVV

VVV

VVV

Vii

ii

i

tbtstd

cbcscd

ubusud

CKM

Experimentally:

9992.09990.0043.0037.0014.00048.0

044.0039.09744.09730.0227.0221.0

0045.00029.0227.0221.09751.09739.0

CKMV


5

Physics aimsPhysics aims

_: Bd-Bd Mixing Phase : Weak Decay Phase _ : Bs-Bs Mixing Phase

Standard Model:

CKM matrix in Wolfenstein parametrization ~O(5):

2312

13

2312

13212

2312

sincos801.02265.0

ss

s

ss

s

s

sAs

tbi

tsi

td

cbcscd

iubusud

CKM

VeVeV

VVV

eVVV

O

AiAAiA

AAiAA

iA

V

6

42423

224252

44

342

21211

421

212

421

358.0,189.0,21, 2

02.0

;tan;1

tan

2

11

(From CKM-fit hep-ph/0406184)


6

Physics aimsPhysics aims Two main unitarity triangles:

0*** tbtdcbcdubud VVVVVV 0*** udtdustsubtb VVVVVV

3

*

AVV udub

Re

Im

1

3

*

AVV tdtb

3

*

AVV cdcb

Re

Im

3

*

AVV tbub 3

*

AVV tdud

3

*

AVV tsus

22

21

(db) (ut)

,21, 2


7

Physics aimsPhysics aims

/0 JBs

0*** tbtdcbcdubud VVVVVV 0*** udtdustsubtb VVVVVV

Channels to be used to extract unitarity triangles:


8

from Bfrom Bss →→J/J/Diagrams)Diagrams)

itsts eVV

b c

cs*

csV

ss

0SB

cbV

/J

bc

c

scsV

ss

0SB

*cbV

/J

b stsV

bs

0SB

tbV

*tbV

*tsV

0SB

tcu ,,

tcu ,,

b stsV

bs

0SB

tbV

*tbV

*tsV

0SBtcu ,, tcu ,,

Decay

Mixing

2

22

2

21

1

4)(0 10)3.33.9(/

BJBs

ii

ts

its

cscb

cscb

tstb

tstb

J

J eeV

eV

VV

VV

VV

VV

A

A

p

q 2*

*

*

*

/

/

(This is not Wolfenstein parameter!)


9

from Bfrom Bss →→J/J/Asymmetry)Asymmetry)

)2sin( mixA

Asymmetry:

(if J/ is eigenstate)

11)1(0 1 CPPL L

2sinh)2cos(

2cosh

)sin(

2sinh}Re{

2cosh

)sin(}Im{/ tt

tmAtt

tmA smixsJ

But J/ is not pure CP eigenstate:

11)1(1 1 CPPL L

11)1(2 1 CPPL L

1C

CP even

CP odd

CP even

)/()/(

)/()/(/

JBAJBA

JBAJBAA

ss

ssJ


10

from Bfrom Bss →→ J/ J/Non-CP)Non-CP)

Change due to mixed eigenstate:

2sinh}Re{2

2cosh)1(

)sin(}Im{2)cos()1(

2

2

/ tt

tmtmA ssJ

i

t

ts e

R

RJB 20

1

1)/(

)1(

)1(

/

/

CPA

CPAR

J

Jt

The effect of the CP admixture is to dilute extraction of and to add a small coefficient in front of cos(ms) since:

1


11

from Bfrom Bss →→ J/ J/Transversity)Transversity)

Extraction of CP eigenstates (transversity analysis):

Three polarization states

pCPA

iCPA

CPE

mAA

JTT

J

LLJJ

ˆ)1(2

)1(2

)1(

**/

**/

||

**/

00/

Bs→J/(l+l-)(K+K-) has

three angles but can be put into J/reference frame with only one angle (the transversity tr) that comes out of (K+K-) decay plane . J/ rest frame


12

Angular distribution in transversity:

2222sin)(

4

3)cos1()(

8

3

cos

)/(tAtA

dtd

JBd s

tstt etmeeA

tAtAtACP

HL

)2sin()sin()(sin)(cos)0(

)()()(1

222

2

||

2

0

2

tstt etmeeA

tAtACP

HL

)2sin()sin()(cos)(sin)0(

)()(1

222

22

Once CP eigenstates established, the analysis proceeds in the same

manner to establish CP asymmetries. References:

– Durham workshop CERN-TH/2001-034 (hep-ph/0102159)

– LHCb notes: LHCb 98-067 & G. Raven, LHCb 2003-118 and LHCb 2003-119

– “B decays at the LHC”: CERN-TH/2000-101

from Bfrom Bss → J/ → J/ (Transversity) (Transversity)


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LHCb ExperimentLHCb Experiment LHCb Detector: forward single arm spectrometer at LHC

Acceptance:10-300 mrad bending

10-250 mrad non-bending


14

LHCb ExperimentLHCb Experiment Exploit VELO for Bs proper time

measurement (Bs oscillations) Proper time resolution: ~40 fs ms sensitivity: 68 ps-1(Standard

Model ~ 20 ps-1)

Exploit RICH for particle identification: (K+K-)

PID: -K separation 1-100 GeV

RICH1RICH2


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BBss → J/ → J/ (Da Vinci Analysis) (Da Vinci Analysis)

Real MC Data

Combine to select Bs

Select Ф

Select J/ψ

Calculate

Transversity

Write Histos &

NTuples

Work flow of BBss → J/ → J/ analysis using Da Vinci (LHCb analysis package) First ever LHCb analysis run on the Grid (GLite) by S Paterson


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BBss → J/ → J/ (Da Vinci Analysis) (Da Vinci Analysis) Ran with 100,000 BBss → J/ → J/ signal events

Efficiency J/14.4%Energy resolution: 13 MeV

Efficiency 9.8%Energy resolution: 9 MeV


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BBss → J/ → J/ (Da Vinci Analysis) (Da Vinci Analysis)

Bs Efficiency ~ 8.2%

Energy resolution: 17 MeV

Event selection quite clean

Transversity distribution looks promising

Contributions from CP odd (ℓ=1) & CP even (ℓ=0,2) states


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BBss → J/ → J/ (Da Vinci Analysis) (Da Vinci Analysis) LHCb 2003-119 by Gerhard Raven, used a toy MC for re-optimization TDR (20% CP odd; 80% CP even)

Very similar to distribution extracted. Need to fit to CP-odd versus CP-even


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BBss → J/ → J/ (G. Raven toy MC) (G. Raven toy MC) Proper time resolution: 38 fs (G Raven LHCb 2003-118)

Annual yield:

Assume Lint=2 fb-1(107 s at 2x1032 cm-2s-1); bb=500b; fB=10% for Bs hadronization; BRvis=3.1x10-5 Implies: 113 k events per year (with 8.2% efficiency)

visBbb BRfLS 2int


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BBss → J/ → J/ (G. Raven toy MC) (G. Raven toy MC)

LH

G. Raven’s toy Monte Carlo varied a number of parameters to extract sensitivities

tsmixt etmqAweAtACP L

)sin()21()0()(122

tsmixt etmqAweAtACP H

)sin()21()0()(12

_q=+1(-1) for events tagged as Bs (Bs)w=wrong tag fraction (=0.5 for untagged)Assumed Q=tag(1-2w)2=4.5% (w=35%, tag =50%).

Untagged sample can be used to extract lifetime difference:

One can fit for 5 parameters:

stmix mCPA

CPARA

,,,)1(

)1(,)2sin(


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BBss → J/ → J/ (G. Raven toy MC) (G. Raven toy MC) Results:


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Sensitivity BSensitivity Bss →→ J/ J/ In one year expect ~ 113 k events (negligible background)

sindepending on ) In five years:sin(Standard Model:

sin

ss

mx

One year


23

New PhysicsNew Physics Left-Right symmetric models (eg. SB-LR)


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ConclusionsConclusions

Bs →J/is a very promising channel to study at LHCb Not accessible at B factories or Tevatron Standard Model prediction for is very small (~ 0.02) New Physics could make significantly larger than SM Started analysis of Bs →J/and can achieve yields of

~100k events per year Using Toy Monte Carlo (G Raven), LHCb can probe to

values very close to SM predictions, sin0.064 within 1 year

LHCb-Babar Meeting 8 April 2005.

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Transcript of LHCb-Babar Meeting 8 April 2005.