Prospects for at LHCb

Val Gibson

(University of Cambridge)

On behalf of the LHCb collaboration

Physics at the LHCSplit, October 3rd 2008

3/10/08 Prospects for gamma at LHCb 2/20

Introduction plays a unique role in flavour physics

— Can be measured via both tree and loop processes

Trees— Benchmark Standard Model reference point

Loops— Sensitive to New Physics

Very impressive measurements from the

B factories

To fully test SM and unitarity need — ~ few % precision

— measurements in B, B0 and Bs systems)100,54(]2[,)1278(

)113,29(]2[,)70( 2729

K.TrabelsiCKM 2008

V.SordiniCKM 2008

3/10/08 Prospects for gamma at LHCb 3/20

LHCb High statistics

— bb ~ 500 b at 14 TeV

— ℒ ~ 2 x 1032 cm-2s-1

— 1012 bb per 2 fb-1 (1 year)

— All B species (B0, Bs, Bc, b …)

Excellent tracking system— VELO and tracking detectors

— Mass resolution, B(D)~15 (7) MeV

— B vertex resolution, z~ 200 m

— Proper time resolution, ~ 40 fs

Excellent particle identification— 2 RICH detectors— separation over p ~2100 GeV

Trigger— High pT hadron trigger at L0

VELOFirst real tracks

RICH HPDs

with trees

B DK Strategies

Time integrated analyses based on:

“ADS”: Atwood, Dunietz, Soni; Phys. Rev. Lett. 78 (1997) 3257;

Phys Rev. D63 (2001) 036005.

“GLW”: Gronau, London, Wyler; Phys. Lett. B253 (1991) 483;

Phys. Lett. B265 (1991)172.

“Dalitz” or “GGSZ”: Giri, Grossman, Soffer, Zupan, Phys. Rev. D68 054018 (2003)

3/10/08 Prospects for gamma at LHCb 5/20

B DK Strategies Measure through interference in decays Provided and decay to common final state Common parameters

CKM angle Amplitude ratio, rB

Strong phase difference, B

KDDB 000D 0D

u

b

u

s

c

u 0D–K

colour-suppressed

u

u

b

c

u

s

0D

–K

colour-allowed

B

d

b

s

c 0D0*K

colour-suppressed

u

d

b

s

c

u 0D

colour-suppressedd d

0*K

0B

Bi

BerKDB

KDB

0

0

1.0Br

BBrr 0

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BD(hh)K (ADS+GLW) 6 rates, 5 parameters

rB = 0.10

B = 130o (PDG)

D decay parameters:

r = 0.0616 (PDG)

= -158o

(ADS formalism requires -180o phase

shift w.r.t published result)

Constraints

from CLEO-c

PRL 100(2008) 221801

LHCb-2008-011LHCb-2008-031

Mode Sig. Yield* B/S

B+D (fav.) 28k 0.6

B+D (sup.) 650 1.2

B+D( 3k 1.2

B+D()K 1k 3.6

911111222K (o) -190 -174 -158 -144 -130

(o) 12.7 10.8 13.8 12.6 10.8

017.0023.0103.0

Br

ICHEP 2008

Sensitivity 2 fb-1

*All signal yieldspresented are for 2 fb-1

3/10/08 Prospects for gamma at LHCb 7/20

B0 D(hh)K*0 (ADS+GLW) 6 rates, 5 parameters

rB0 = 0.40

B0 (scan)

D decay parameters:

r = 0.0616 (PDG)

= -158o

(ADS formalism requires -180o phase

shift w.r.t published result)

Constraints

from CLEO-c

PRL 100(2008) 221801

LHCb-2007-050LHCb-2008-031

Mode Sig. Yield B/S

B0D( (fav.) 3.4k [0.4,2.0]

B0D( (sup.) O(500) [2.0,13.0]

B0D( O(500) [0,0.4]

B0D( O(100) [0,14.0]

B0 (o) 0 45 90 135 180

(o) 6.2 10.8 12.7 9.5 5.2

911111222K

..%95@]41.0,07.0[

..%68@]34.0,18.0[0

lc

lcrB

ICHEP 2008

Sensitivity 2 fb-1

68%95%

3/10/08 Prospects for gamma at LHCb 8/20

BD(ADS) Br(DK3) = 8.1% c.f. Br(D K)=3.89% 4 rates Multi-body final state

— Integrate over ALL phase space

— “Coherence factor” R

r = 0.0568 (PDG)

Constraints

Mode Sig. Yield B/S

B+D 31k 0.7

B+D 530 2.3

LHCb-2007-004LHCb-2008-031

RK3π

K3π

(o )

Prelim: arXiv:0805.1722 CLEO-c

3332

32 cos2 KBKKBKB RrrrrKKDB

Atwood and Soni, PRD 68 033003(2003)

Sensitivity 2 fb-1

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BDs(“Dalitz”)

sDalitz plots contain a CP-violating contribution from the

B and B interference which is sensitive to .

Two analysis methods:— Unbinned fit based on amplitude model

— Model independent binned fit using results from (3770) on D decays

Giri et. al., PRD 68 (2003) 054018;

Bondar and Poluektov, EPJ C47 (2006) 347; hep-ph/0703267;arXiv:0801.0840

LHCb 2 fb-1

BB

3/10/08 Prospects for gamma at LHCb 10/20

BDs(“Dalitz”)

Signal yield ~ 5k (total) per year

BDsbackground suppressed with max. momentum cut (good for RICH pid)

Dominant physics background

BDsX plus random “”

~16% prob. of picking up “” from

underlying event or other B.

LHCb-2008-028

Background type B/S

BDs < 0.095 (90% c.l.)

BD*X+K < 0.05 (90% c.l.)

DK-signal < 0.09 (90% c.l.)

DK-random 0.350.03

Loose K pid

2 fb-1

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BDs(“Dalitz”) Amplitude Fit: Generate and fit events assuming isobar model.

— Models of BaBar [PRL 95 (2005) 121802] and Belle [hep-ex/0411049] give consistent results.

— Total error will include model uncertainty, currently ~ 7o [BaBar PRD 78 (2008) 034023]

Binned Fit: Removes model dependence by relating bins of Dalitz plot to experimental observables— Slight degradation in statistical precision— Residual error on from CLEO-c statistics ~1-2o [Asner, ICHEP 08]

(o) rB(

o)

Amp. Fit 9.8 0.018 9.3

Binned Fit 12.8 0.020 12.6

LHCb-2007-048LHCb-2007-141

Sensitivity 2 fb-1

Amplitude fit, model error 7o

Binned fit, CLEO-c error 2o

Fit assumes pure combinatorialbackground same level as DK-random

with trees

Time Dependent B DhStrategies

Bs DsK: Aleskan, Dunietz and Kayser, Z. Phys. C54 (1992) 653.

B0 Dand Bs DsK “Uspin Approach”: Fleischer, Nuc. Phys. B671 (2003) 459.

3/10/08 Prospects for gamma at LHCb 13/20

BsDs Measure s from interference between mixing and decay amplitudes.

Large interference effects

s input from Bs J/(s~ 0.03 mrad for 2 fb-1 see A.Satta talk)

Include Bs Ds(20x Br) to determine ms and tagging dilution

Simultaneous fit to Bs Dsand Bs Ds decay time distributions (tagged and untagged)

Bs→Ds-K+ Bs→Ds

-K+

LHCb-2007-017LHCb-2007-041

Mode Sig. yield B/S

Bs Ds 6.2k 0.7

Bs Ds 140k 0.2

Sensitivity 2 fb-1 10 fb-1

10.3 4.6

ms (ps-1) 0.007 0.003

Input parameters: , ms = 17.5 ps-1

s

b

cu

s

sD

–K

ssB ss

b uc

s sD

K

4.01

~ cb

ubDK V

Vr

3/10/08 Prospects for gamma at LHCb 14/20

B0 D Measure d analogous to Bs Ds

d input from B0 J/s(d = 0.02 mrad for 2 fb-1 see ? talk)

Problems— Interference small

— 8 fold ambiguity ( small) Potential solutions

— “Conventional approach”: compare with other channels e.g. B0 D— “Uspin approach”: B0 Dand Bs Ds

LHCb-2008-035LHCb-2007-044

02.0~ cb

ubD V

Vr

Mode Sig. yield B/S

Bs Ds 6.2k 0.7

B D 1340k 0.22

Sensitivity 2 fb-1 10 fb-1

for

for Input :

349 35

2210

3020

415

128

Uspin approach shows verypromising results.

3

0% U

spin

brea

king

2 fb-1

(stat. 30% Upsin breaking)

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with trees : Global Sensitivity Perform global fit to B DK with common parameters.

Include results from B0 and Bs time dependent analyses.

B (o) 0 45 90 135 180

for 0.5 fb-1 (o) 8.1 10.1 9.3 9.5 7.8

for 2 fb-1 (o) 4.1 5.1 4.8 5.1 3.9

for 10 fb-1 (o) 2.0 2.7 2.4 2.6 1.9

LHCb-2008-031

Input measurements:

BD0K

• D0(LHCb-2008-011)

• D0 (LHCb-2007-004)

• D0s(LHCb-

2007-048)

B0D0

• D0 (LHCb-2007-050)

Time dependent measurements:

• B0 D(LHCb-2008-035)

• Bs Ds(LHCb-

2007-041)

Parameters (input value):

BD0K

• (60o) • rB – ratio of magnitude of diagrams (0.1)• B – strong phase difference (130)

B0D0analogues: rB0 (0.4), B0 (scan)

D decay parameters for , :

• r, r well known (PDG)• (158 (144o)• R – coherence factor

Constrained by CLEO-c

“Conventional” approach used for B0 D( with 2 fb-1) to avoid large correlations with Bs DsK.

with loops

New physics in B hh and B hhh modes

B0 and Bs :

“Uspin Approach”, Fleischer, Phys. Lett B458 (1999) 306.

B and B s: “Dalitz Approach”, Bediaga, Guerrer and Miranda, Phys Rev D76 073011 (2007).

3/10/08 Prospects for gamma at LHCb 17/20

B0 and Bs Measure from interference between mixing

and tree and penguin decay diagrams

Demonstrates excellence of RICH pid

LHCb-2007-059

Mode Sig. yield

(untagged)

B/S

(incl. bb)

B0 36k 0.5

Bs 36k 0.15

B0 140k < 0.06

Bs 10k 1.9

)(sd

b

u

sd

sdu

sBB0

)(sd

bW

)(sd

u

sdu

hypothesis

mhh (GeV/c2)

hypothesis

mhh (GeV/c2)

3/10/08 Prospects for gamma at LHCb 18/20

B0 and Bs Fit CP asymmetries of B0 and Bsevents

— 4 observables:

Parameters— — penguin to tree amplitude ratio dede

— Input d and s

Weak Uspin constraint— dd 20%,indep.

Measures and tests Uspin symmetry

2sinh

2cosh

)sin()cos()(

f

mixf

dirfCP

f

A

mAmAA

Sensitivity 2 fb-1 10 fb-1

(o) 10 5

d0.18 0.09

(o) 9 5

(o) 17 8

LHCb-2007-059

mixKK

dirKK

mixdir AAAA ,,,

2 fb-1Bs

(ps)

3/10/08 Prospects for gamma at LHCb 19/20

B and B0 s Measure from a Dalitz analysis of B K and B0Ks decays

— K* resonance (dominant contributions)

Extract penguin contribution from B K — Use Dalitz anistropy to measure CP

asymmetry including phase differences

Dalitz analysis of B0/ B0 Ks

— Untagged analysis possible since B0 and

B0 interference regions do not overlap

Promising results: ~5o with 2 fb-1

G.Guerrer CKM 2008

Mode Sig. yield B/S

B+ K 494k 0.3

B0 s 90k t.b.d.

)(du

b ud

s

,

duud d

bW

d

u

s

u

I

II

III

IV

m2

m2

S

I

ii

iii

NN

NNS

CP

S

III no-CP

3/10/08 Prospects for gamma at LHCb 20/20

SummaryLHCb offers exciting prospects for a precision measurement of

with trees— Standard Model benchmark

— External input from CLEO-c of upmost importance

— A combined sensitivity of ~2-3o is expected with 10 fb-1 of data

— Many channels still to be investigated

DDsDsD((sDs(etc

with loops — Sensitive to New Physics

— B hh analysis can measure ( ~ 5o with 10 fb-1) and test Upsin symmetry

— B hhh very promising first studies

— Other channels to investigate: Bd , Bs Bs Ketc

First challenge: reconstruct hadronic final states with real data….. coming soon

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Backup Slides

3/10/08 Prospects for gamma at LHCb 22/20

B Tagging

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with trees : Global Sensitivity

Weight (in %) of each contributing analysis with 2 fb-1 for two values of B0

Sensitivity of B0D0K*0 improves by a factor of two in going from B0 =45 180o. Residual dependence remains in global fit, but diluted due to other measurements.

Analysis B0 B0

BD0(hh)K, BD0()K

25 38

BD0(s)K 12 25

B0D0(hh)K*0 44 8

BsDsK 16 24

B0D 3 5

LHCb-2008-031

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B and B0 s G.Guerrer CKM 2008