LHCb Physics Programme

Marcel MerkFor the LHCb Collaboration

May 26, 2008

Contents:• The LHCb Experiment• Physics Programme:

• CP Violation• Rare Decays

CERN Theory Institute: Flavour as a window to New Physics at the LHC: May 5 –June 13, 2008

LHCb @ LHC

A Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays

CMS ALICE

ATLASLHCb CERN

√s = 14 TeVLHCb: L=2-5 x 1032 cm-2 s-1

sbb = 500 mbsinel / s bb = 160=> 1 “year” = 2 fb-1

b

bb

b

3

The LHCb Detector

31-3-2008

VELO

Muon det Calo’s RICH-2 MagnetOT RICH-1

VELO

Muon det Calo’s RICH-2 MagnetOT+IT RICH-1

Installation of major structures is complete

4

A walk through the LHCb spectrometer…

5

B-Vertex Measurement

31-3-2008

Vertex Locator (Velo)Silicon strip detector with ~ 5 mm hit resolution 30 mm IP resolution

Vertexing:• Impact parameter trigger• Decay distance (time) measurement

Ds

Bs K

K

K

d

47 mm 144 mm

440 mmPrimary vertex

Decay time resolution = 40 fs

s(t) ~40 fs

Example: Bs → Ds K

6

Momentum and Mass measurement

Momentum meas.: Mass resolution for background suppression

7

Momentum and Mass measurement

Momentum meas.: Mass resolution for background suppression

bt

Bs K

K

, K

Ds

Primary vertex

Bs→ Ds KBs →Ds

Mass resolutions ~14 MeV

8

Particle Identification

RICH2: 100 m3 CF4 n=1.0005

RICH: K/ identification using Cherenkov light emission angle

RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014

9

Particle Identification

RICH2: 100 m3 CF4 n=1.0005

RICH: K/ identification; eg. distinguish Ds and DsK events.

RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014

Cerenkov light emission angle

bt

Bs K

K

,K

Ds

Primary vertex

KK : 97.29 ± 0.06%K : 5.15 ± 0.02%

Bs → Ds K

10

LHCb calorimeters

e

h

Calorimeter system : • Identify electrons, hadrons, neutrals• Level 0 trigger: high ET electron and hadron

bt

Bs K

K

K

Ds

Primary vertex

11

LHCb muon detection

m

Muon system: • Level 0 trigger: High Pt muons• Flavour tagging: eD2 = e (1-2w)2 6% btag

Bs K

K

K

Ds

Primary vertex

12

LHCb trigger

HLT rate Event type Physics

200 Hz Exclusive B candidates

B (core program)

600 Hz High mass di-muons

J/, bJ/X (unbiased)

300 Hz D* candidates Charm (mixing & CPV)

900 Hz Inclusive b (e.g. bm)

B (data mining)

HLT: high IP, high pT tracks [software] then full reconstruction of event

40 MHz

1 MHz

2 kHz

L0: high pT (m, e, g, h) [hardware, 4 ms]

Storage (event size ~ 50 kB)

Detector L0, HLT and L0×HLT efficiency

Note: decay time dependent efficiency: eg. Bs → Ds K

Proper time [ps]

Effici

ency

bt

Bs KK

K

Ds

Primary vertex

12

13

Measuring time dependent decays

bt

Bs K

K

Ds

Primary vertex

Measurement of Bs oscillations:

Bs->Ds– (2 fb-1)Experimental Situation:

• Ideal measurement (no dilutions)

14

Measuring time dependent decays

bt

Bs K

K

Ds

Primary vertex

Bs->Ds– (2 fb-1)

Measurement of Bs oscillations:

Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging dilution

15

Measuring time dependent decays

bt

Bs K

K

Ds

Primary vertex

Bs->Ds– (2 fb-1)

Measurement of Bs oscillations:

Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging dilution+ Realistic decay time resolution

16

Measuring time dependent decays

bt

Bs K

K

Ds

Primary vertex

Bs->Ds– (2 fb-1)

Measurement of Bs oscillations:

Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging+ Realistic decay time resolution+ Background events

17

Measuring time dependent decays

bt

Bs K

K

Ds

Primary vertex

Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging dilution+ Realistic decay time resolution+ Background events+ Trigger and selection acceptance

Two equally important aims for the experiment:• Limit the dilutions: good resolution, tagging etc.• Precise knowledge of dilutions

Bs->Ds– (2 fb-1)

Measurement of Bs oscillations:

18

Expected Performance: GEANT MC simulation

Used to optimise the experiment and to test physics sensitivities

Simulation software:• Pythia+EvtGen• GEANT simulation• Detector response

Reconstruction software:• Event Reconstruction• Decay Selection• Trigger/Tagging• Physics Fitting

Physics Programme

LHCb is a heavy flavour precision experiment searching for new physics

in CP-Violation and Rare Decays

• CP Violation• Rare Decays

19

CP Violation – LHCb Program

*cd cbV V

*ud ubV V

*td tbV V

g *

cs cbV V*

us ubV V*

ts tbV V s

* *

*

*

*

*

*

*

arg ; arg

arg ; arg

tb cd cb

ud tb

ud tb

td

ub td

ub ts

cd cb s cbs

c

V V VVV VV V

V VV

VV V VV

g

s mixing phase (SM): 2 ssB d mixing phase (SM): 2 dB

Bd triangle

Bs triangle

2 3

2 2

3 2

1 / 21 / 2

1CKM

i

i d si

eA

eA A e

V A

g

CP Program: Is CKM fully consistent for trees, boxes and penguins?1. g measurements from trees2. g measurement from penguins3. s from the box: “Bs mixing phase”4. s in penguins

b q1

d, sq2W−

g

d (s)

q

q

W −

b u,c,t

b

q

u, c, tu, c, t

q

bqBqB W+ W−

V*ib Viq

Viq V*ib 20

1.a g +s from trees: Bs→DsK

( ( ( (

( ( (

2

2

1 cos 2 sin sin

1 cosh 2 sins2 2

c ho

/ s

s

s

ss

mt mt

t tB BD KA

g

g

• Time dependent CP violation in interference of bc and bu decays:

Bs

Bs

sD K sie

sie ie g

Bs

Bs

sD K sie

sie ie g

Time

21

Bs/Bs →Ds–K+ (10 fb-1)

10 fb-1 data:Bs→ Ds

-

Bs→ Ds-K+

(ms = 20)

• Since same topology BsDsK, Bs Ds p combine samples to fit ms, s and Wtag together with CP phase gs.

Channel Yield (2 fb-1)

B/S (90% C.L.)

BsDsK 6.2 k [0.08-0.4]

BsDs 140 k [0.08-0.3]

• Use lifetime difference s to resolve some ambiguities (2 remain).

Bs→DsK

s(gs) = 9o–12o

Decay Time →22

B →D and Bs→DsK

Channel Yield (2 fb-1) B/S

BsD*(K ) 206 k <0.3

B->D 210 k 0.3

B D(*) measures g in similar way as BsDsK• More statistics, but smaller asymmetry• No lifetime difference: 8 –fold ambiguity for g solutions

Invoking U-spin symmetry (d↔s) can resolve these ambiguities in a combined analysis of DsK and D(*)pi (Fleisher)

Can make an unambiguousextraction, depending onThe value of strong phases: s(g < 10o (in 2 fb-1)

U-s

pin

brea

king

23

LHCb-2005-036

1.b g from trees: B→DK

GLW method:fD is a CP eigenstate common to D0 and D0: fD= K+K-, +-,…Measure: B→D0K, B → D0K, B→ D1K• Large event rate; small interference • Measurement rB difficult

0

0

( )( )

Bi iB

A B D KA B D K

r e e g

B–

D0K–

D0K–

fDK–

bc favoured

bu suppressed

Decay time independent analysis

Cabibbo supp.

Cabibbo allowed.

• Interfere decays bc with bu to final states common to D0 and D0

colorsuppression

( BiBr e g

DiDr e

ADS method:Use common flavour state fD=(K+ –

Note: decay D0→K+– is double Cabibbo suppressed• Lower event rate; large interference

24

B→D(*)K(*)

GLW: D KK (2 rates) ;

ADS: D K ( 4 rates) ;

Channel Yield (2 fb-1) B/S

B → D(hh) K 7.8 k 1.8

B → D(K) K , Favoured 56 k 0.6

B → D(K) K , Suppressed 0.71k 2

B → D(K3) K, Favoured 62k 0.7

B → D(K3) K, Suppressed 0.8k 2s(g) = 5o to 13o

depending on strong phases.

Also under study:B± → DK± with D → Ks 8012o

B± → DK± with D → KK 18o

B0 → DK*0 with D → KK, K, 6o 12o

B± → D*K± with D → KK, K, (high background)

Normalization is arbitrary:7 observables for 5 unknows:g, rB, B, D

, D3

Overall: expect precision ofs(g) = 5o with 2 fb-1 of data

( ( (

( ( ( ( ( ( ( (

2

22

22 3 33

1 2 cos

2 cos

3 2 cos

B B B

B B B D

D

D DD

B D B BD DD

B K K K

B K K r r

B K K r

r

r r r

r r

r

g

g

g

ADS: D K3 (4 rates) ;

Dalitz analyses

s(g)

See talk of Angelo Carbone

25

2. g from loops: B(s)→hh• Interfere b u tree diagram with penguins:

( cos sin

cosh sinh2 2

CPf

dir mixf

f

fmt mtA

A At

t tA

( ( ( (

1 2

3 4

, ,sin ; , ,sin

', ',sin ; ', ', sinmix dir

KK KKdir mix

d

s

A Af d f d

f d f dA A

gg

• Strong parameters d (d’), (’) are strength and phase of penguins to tree. Weak U-spin assumption : d=d’+-20% , , ’ independent• Assume mixing phases known

Channel Yield (2 fb-1)

B/S

B 36k 0.5

BsKK 36k 0.15

BsK+K-BG

s ( g ~10o

See talk of Angelo Carbone

2 fb-1

ms=20

Time26

ACP(t) N B 0 J /KS( N B0 J /KS( N B 0 J /KS( N B0 J /KS(

s(sin2 ) ~ 0.02

3. The Bd and Bs Mixing Phase

( 0 : ( ) sin sinCP f ddB A t m t ( sin sin: ( )

cosh cos sinh2

f ss CP

s sf

s

s

m tB A t

t ts

Time dependent CP violation in interference between mixing and decay

“Yesterday’s sensation is today’s calibration and tomorrow’s background” – Val Telegdi

BB

fCPdie

“Golden mode”

Bs

Bs

fCPsie

Channel Yield (2 fb-1)

B/S

BdJ/Ks 216 k 0.8

27

Bs mixing phase

Decay Yield (2 fb-1)

s (s)

J/ gg8.5 k 0.109

J/3 k 0.142

J/ ’ 2.2 k 0.154

J/ ’rg 4.2 k 0.08

c 3 k 0.108

Ds+ Ds

- 4k 0.133All CP eig - 0.046

J/ 130 k 0.023

All - 0.021

( sin sin( )

cosh cos sinh2

sCP

s

f

sf

s

s

m tA t

t ts

1. Pure CP eigenstates Low yield, high background2. Admixture of CP eigenstates: Bs→J/ “Golden mode”: Large yield, nice signature However PS->VV requires angular analysis to disentagle =+1 (CP-even) ,-1 (CP-odd)

28

Full 3D Angular analysiscos cos

cos

Study possible systematics of LHCb acceptance and reconstruction on distributions.29

Bs→ J/

time

mass

signalbackgsum

cos tr

cos

tr

s(M)= 14 MeV

s(t)= 35 fs

• Simultaneous likelihood analysis in time, mass, full 3d-angular distribution

• Include mass sidebands to model the time spectrum and angular distribution of the background

• Model the t resolution

s (s)=0.02

See talk of Olivier Leroy

30

4. & s from Penguins• Compare observed phases in tree decays with those in penguins

Channel Yield (2 fb-1) B/S Weak phase precision

B Ks920 0.3 < B/S < 1.1 s (sin(d

eff) 0.23

Bs 3.1 k < 0.8 s (seff ) = 0.11

• Bs requires time dependent CP asymmetry (PSVV angular analysis a la J/ )

: 2 2effs

mix decays s sB 0 2: 2eff mix dec

say

d sB K

31

See talk of Olivier Leroy

Physics Programme

LHCb is a heavy flavour precision Experiment searching for new physics

in CP-Violation and Rare Decays

• CP Violation• Rare Decays

32

Rare Decays – LHCb Program

( 2F

eff CK ii

iM CGH V Om i=1,2: treesi=3-6,8: g penguini=7: g penguini=9,10: EW penguin

Study processes that are suppressed at tree level to look for NP affecting observables: Branching Ratio’s, decay time asymmetries, angular asymmetries, polarizations, …

Weak B-decays described by effective Hamiltonian:

New physics shows up via new operators Oi or modification of Wilson coefficients Ci compared to SM.

LHCb Program: Look for deviations of the SM picture in the decays:1. b sl+l- ; Afb(BK*mm) , B+→K+ll (RK), Bs→ mm 2. b s g ; Acp(t) Bs g , B→K*g, Lb→Lγ, Lb→ L*γ,B →r0g,

B→wγ3. Bq l+l- ; BR (Bs mm) 4. LFV Bq l l‘ (not reported here) 33

1. B0→K*0µ+µ-

• Contributions from electroweak penguins• Angular distribution is sensitive to NP

( 2 F BFB

F B

N NA s mN Nm m

m2mm

[GeV2]

AFB(m2μμ) theory illustration

0.38 20 0.35SM: s 4.39 GeV

Observable: Forward-Backward Asymmetry in l

Zero crossing point (so) well predicted:

3 angles:l, ,K

A FB

34hep-ph:0106067v2

B0→K*0µ+µ-

Channel Yield (2 fb-1) BG (2 fb-1)

Bs→K*m+ m– 7200+-2200 (BR) 1770+-310

Event Selection:

Systematic study: • Selection should not distort m2

mm • s0 point to first order not affected

• AFB(s), fast MC, 2 fb–1

s = (mmm)2 [GeV2]

2 fb-1

A fb(s

)

Removeresonances

s0

See talk Mitesh Patel

s(s0) = 0.5 GeV2

35

2. Bs→g

• Probes the exclusive b →s radiative penguin Measure time dependent CP asymmetry:

( ( ( ( (

cos sin

cosh sinh2 2

ds s

Cir m

Px

s

i

s

B B mt mtA tB

AB A t

At

g g

g g

Channel Yield (2 fb-1)

B/S

Bs→g 11k <0.55

Statistical precision after 2 fb-1 (1 year)s(Adir ) = 0.11 , s (Amix ) = 0.11 (requires tagging) s (A) = 0.22 (no tagging required)

In SM b→s g is predominatly (O(ms/mb)) left handedObserved CP violation depends on the g polarization

See talk Mitesh Patel

Event selection:

b g (L) + (ms/mb) g(R)

Adir 0, Amix sin2 sin2 , A cos 2 cos tan = |b→s g R| / | b→s g L| , cos 1

SM:

Measures fraction “wrong” g polarization36

3. Bs →mm • Bs mm is helicity suppressed SM Branching Ratio: (3.35 ± 0.32) x 10 -9

• Sensitive to NP with S or P coupling

Channel SM Yield (2 fb-1)

Background

Bs mm 30 83

Event Selection:Main Backgrounds: Suppressed by:bm, bm Mass & Vertex resol.B hh Particle Identification

With 2 fb-1 (1 “year”):• Observe BR: 6 x 10-9 with 5 s• Assuming SM BR: 3s observation

37

See talk Mitesh Patel

hep-ph/0604057v5

Physics Programme

LHCb is a heavy flavour precision Experiment searching for new physics

in CP-Violation and Rare Decays

• CP Violation• Rare Decays+ “Other” Physics

38

“Other” Physics

See the following talks for an overview:

Raluca Muresan:• Charm Physics: Mixing and CP Violation

Michael Schmelling:• Non CP Violation Physics:

– B production, multiparticle production, deep inelastic scattering, …

39

ConclusionsLHCb is a heavy flavour precision experiment searching

for New Physics in CP Violation and Rare Decays

A program to do this has been developed and the methods, including calibrations and systematic studies, are being worked out..

CP Violation: 2 fb-1 (1 year)*• g from trees: 5o - 10o

• g from penguins: 10o

• Bs mixing phase: 0.023

• seff from penguins: 0.11

Rare Decays: 2 fb-1 (1 year)* • BsK*mm s0 : 0.5 GeV2

• Bs g Adir , Amix : 0.11 A : 0.22• Bsmm BR.: 6 x 10-9 at 5s

We appreciate the collaboration with the theory community to continue developing new strategies.

We are excitingly looking forward to the data from the LHC.

* Expect uncertainty to scale statistically to 10 fb-1. Beyond: see Jim Libby’s talk on Upgrade 40

Backup

LHCb Detector

MUON

RICH-2 PID

RICH-1 PID

Tracking (momentum)

vertexing

HCAL

ECAL

4331-3-2008

Display of LHCb simulated event

Flavour Tagging

Performance of flavour tagging: Efficiency e Wrong tag w Tagging power

Bd ~50%

Bs ~50% 33% ~6%Tagging power:

( 22 1 2D we e

Full table of selectionsDet.eff.(%)

Rec.eff.(%)

Sel.eff.(%)

Trig. eff.(%)

Tot.eff.(%)

Vis.BR

(10 6)

Annualsignalyield

B/Sfrom

bb bkg.B0 12.2 91.6 18.3 33.6 0.69 4.8 26k < 0.7Bs K K 12.0 92.5 28.6 36.7 0.99 18.5 37k 0.3Bs Ds

5.4 80.6 25.0 31.1 0.34 120. 80k 0.3

Bs Ds +

K 5.4 82.0 20.6 29.5 0.27 10. 5.4k < 1.0B0 D~0

(K)K*0 5.3 81.8 22.9 35.4 0.35 1.2 3.4k < 0.5B0 J/(mm) K0

S 6.5 66.5 53.5 60.5 1.39 20. 216k 0.8B0 J/(ee) K0

S 5.8 60.8 17.7 26.5 0.16 20. 26k 1.0Bs J/(mm) 7.6 82.5 41.6 64.0 1.67 31. 100k < 0.3Bs J/(ee) 6.7 76.5 22.0 28.0 0.32 31. 20k 0.7B0 r 6.0 65.5 2.0 36.0 0.03 20. 4.4k < 7.1B0 K*0 g 9.5 86.8 5.0 37.8 0.16 29. 35k < 0.7Bs g 9.7 86.3 7.6 34.3 0.22 21. 9.3k < 2.4

+ few more channels in TDR

Nominal year = 1012 bb pairs produced (107 s at L=21032 cm2s1 with sbb=500 mb)Yields include factor 2 from CP-conjugated decaysBranching ratios from PDG or SM predictions

BsDsK 5 years data

BsDs-K+ BsDs+K-

BsbDs-K+ BsbDs+K-

Angle g in Summary