Status and Physics reach of LHCb

Status and Physics reachof LHCb

Marta CalviUniversità Milano-Bicocca and INFN

On behalf of the LHCb collaboration

Heavy Quarks & Leptons 08Melbourne 5-9 June 2008

M. Calvi HQ&L08 (2/24

The Large Hadron Collider

LHC start up is approaching:

- Cooling down proceeding well, aiming for machine cold in the first half of July.

- Beam injected end July - early August. First collision 1-2 months later.

- Luminosity 1031 cm–2s–1


LHCb @ LHC

Huge bb production in pp collisions at s=14TeV, in the forward region bb = 500 b N 1012 bb events in Lint =2 fb-1

inel = 80 mb

bb angular correlation in

pp collisions at s = 14 TeV

(Pythia)

A possible running scenario:2008 Expect 50 days of data taking with limited efficiency, L1031 cm–2s–1

Calibration and Trigger commissioning / First results for non-CP physics

2009 Expect 140 days of data taking, L2x1032 cm–2s–1

First results on rare decays and CP physics ~ 0.5 fb–1

2010- Stable running. Expect ~ 2 fb–1/ year

pp interactions/crossing

LH

Cb

n=0

n=1LHCb planes to collect an integrated luminosity of 10 fb–1 for year 2013


LHCb Detector in place

Muon detector

Calorimeters

RICH-2Magnet OT+IT

VELO

RICH-1

Detector installed, going to close and be ready for data-taking. Commissioning with cosmics on-going.


LHCb expected performance (I)B vertex and mass measurement

All results obtained from full Detector

(GEANT4) MC simulation

VErtex LOcator (Silicon strip)

5 m hit resolution 30 m IP resolution

B mass resolution

15-20 MeV/c2

Bs μμ

Bs KK

B proper time resolution 40 fs

From full tracking system (TT+ IT + OT):

Momentum resolution p)/p 0.3%-

0.5% increasing with p

Bs

K

K

Ds

Primary vertex

47m

144m

440m1

cm


LHCb expected performance (II)Particle IDentification

Flavour Tagging performance

from combination of several methods

(electron, muon, kaon, pion, inclusive vertex):

D2 =45% for Bd

D2 =79 % for Bs depending on channel

Qvtx

Bs

B–

D

e

K–

K+PV

KK : 97.29 ± 0.06%K : 5.15 ± 0.02%

RICH1: 5cm aerogel n=1.034m3 C4F10 n=1.0014

RICH2: 100m3 CF4 n=1.0005


VELO

ECAL+ HCAL

MUON

Pile up e, , h high pT

high pT

LHCb Trigger

1 MHz

40 MHz

All DATA

2 kHz Storage

L0, HLT and L0×HLT efficiency

HLT rate Event type Physics

200 Hz Exclusive B selec. B (core program)

600 Hz High mass J/, bJ/X

300 Hz D* candidates Charm

900 Hz Inclusive b (b) B (data mining)

Level-0

High Level Trigger

event size ~50 kB


LHCb: motivation and Physics Program

● b d transitions: broadly studied, in general good agreement with SM.

● b s transitions: still limited knowledge, space for NP effects.

● Strong constraints to SM available from precision measurements of CKM

parameters, but angle still poorly known.

● High statistics production of all kind of b- (and c-) hadrons at LHC allows extensive

studies in wide set of channels.

LHCb is a 2nd generation precision experiment coming after B-Factories and Tevatron:

Improve precision on and other CKM parameters, search for NP

from comparison between tree and box / penguin contributions.

Examples: s from BsJ/ from B(s)D(s)K, penguins in Bs

Search for NP in rare decays, with high precision measurements of BRs

and time dependent CP asymmetries.

Examples: BsBd K0*Bs


Bs Mixing phases with bccs (I)• The sin 2d analogous in the Bs sector.

• The phase arising from interference between B decays with and without mixing is a sensitive probe to new physics.

2sinh2cos

2cosh

)sin(2sin)(

tt

tmtA

SSf

S

SSf

CP

• Time-dependent asymmetry in decay rates:

• Could be much larger if New Physics contributes to Bs-Bs transitions.

From BsJ/ we measure meas = SM + NP

• Tevatron results: D0 s= 0.57 + 0.24-0.30 with 2.8 fb-1

could be a hint of NP? CDFs= [0.32,2.82] @ 68%CL with 1.35 fb-1

In the SM

SM = 2s =0.0368±0.0017


Bs Mixing phases with bccs (II)

• BsJ/()(KK) is the golden channel, requires angular analysis to disentangle the mixture of CP-even (f= -1 ) and CP odd (f=+1)

• Use flavour tagged and untagged events.

• Need very good proper time resolution to resolve Bs oscillations.

total

CP even

CP oddflat background

• Can add pure CP modes: J/, J/’, c, Ds+Ds

-

but much lower statistics.

Decay Channel Yield (2fb-1 ) s

BsJ/() (KK) 130k 0.023

Pure CP modes 25k total 0.048

All modes 0.021

With 0.5 fb–1 (2s)0.046

With 10 fb-1 stat(2s) 0.009

> 3 evidence of non-zero s even if only SMSensitivity to other fit parameters (with 2 fb-1):

(Γs/Γs )=0.0092, (RT)=0.0040


New Physics in Bs mixing

2006 including ms measurement

With s from

Bs J/LHCb 2fb-1

Ligeti, Paucci,Perez, hep-ph/0604112

M12 1 hs exp(2is) M12SM

New Physics in Bs mixing amplitude M12 parameterized with hs and s:

Additional constraints can come from semileptonic Asymmetry. In SM: ASL

s 10-5.

hs

s

Preliminary results on the LHCb measurement of time dependent charge asymmetry in BsDs

Expect 109 events/ 2fb-1 (ASLs )2x10-3 in 2fb-1

ASLs

hs


bsss hadronic penguin decays

Bs

● In SM CP violation < 1% due to cancellation of the

mixing and penguin phase:

Bs SM 2 arg(Vts

*Vtb) – arg(VtsVtb*) = 0

● In presence of NP expect different

contributions in boxes and in penguins:

Bs NP = M

NP - DNP

+ NP?

●From the time dependent angular distribution of flavour tagged events, in 2 fb–1

stat(NP) = 0.11

● Less statistics on Bd KS , expected precision: (sin(2eff)) ≈0.23

Channel Yield (2 fb-1) B/S (90%CL)

Bs 3100 < 0.8

Bd KS 920 < 1.1


Different ways to at LHCb

B mode D mode Method Parameter

Bs→DsK KK tagged, ACP(t) -2s

B+→D K+ K,KK/ counting, ADS+GLW B+→D K+ Ks Dalitz, GGSZ B+→D K+ KK 4 body Dalitz B0→D K*0 KKK, counting, ADS+GLW B→,KK Tagged, ACP(t) d s

tree decays only

And several additional modes under study: B+→D*K+ (DK,KK,), B+→DK+ (DK) …


from Bs DsK

● Two tree decays which interfere via Bs mixing determine in a very clean way

● Fit time-dependent rates of Bs→DsK and Bs→Ds

- Including Bs Dsto constrain ms and mistag

- Use tagged and untagged Bs→DsK samples

2s +

9-12

ms 0.007 ps-1

DsK

tagged as Bs

s

s

b

c

u

s

Bs0

Ds

K

K–

s

s

b

u

c

s

Bs0

Ds

Sensitivity with 2fb–1:


Bs DsK 6200 < 0.2

Bs Ds 140 k 0.4


Different ways to at LHCb

B mode D mode Method Parameter

Bs→DsK KK tagged, ACP(t) -2s

B+→D K+ K,KK/ counting, ADS+GLW B+→D K+ Ks Dalitz, GGSZ B+→D K+ KK 4 body Dalitz B0→D K*0 KKK, counting, ADS+GLW B→,KK tagged, ACP(t) d s

() 2fb-1

9º-12º

11º-14º

7º-12º

18º

9º

10º

● Global fit combining χ2 from the different ADS/GLW rates and Dalitz:

B° (°) 0 45 90 135 180

Combined B+/B0 (ADS+GLW) 4.6° 7.6° 6.3° 7.1° 4.6°

+ model independent Dalitz 4.2° 5.7° 5.3° 5.7° 4.2°

() 2fb-1

● Combining with time dependent measurements ( DsK and D) gives a global

LHCb sensitivity to with tree decays only: ~ 4º with 2 fb–1


Bs

- Highly suppressed in SM: BR(Bs→) =(3.35±0.32) x10-9

- Could be strongly enhanced by SUSY: BR(Bs→ ) tan6/MH2

- Current limits from Tevatron ~2 fb-1: CDF BR < 4.7 x 10-8 90% CL D0 BR < 7.5 x 10-8 90% CL

W

W

b

s

t

SM

LHCb: high stat. & high trigger efficiency for signal, main issue is background rejection.

Largest background is b , b .

Specific background dominated by Bc± →J/

Exploit good mass resolution and vertexing, and good particle ID.


Bs Analysis in a Phase Space with 3 axis:

• Geometrical Likelihood (GL) (impact parameters, distance of closest approach between , Bs lifetime, vertex isolation)

• Particle-ID Likelihood • Invariant mass window around Bs peak

- Sensitive Region: GL > 0.5

- Divide in N bins

- Evaluate expected number of events for signal/background in each bin.

Assuming SM BR, in 2fb-1 30 signal events

83 background events

signalbb inc.b μ, b μBc

+ J/Ψμν

(arbitrary normalization)

- Normalization from BJ/K events. Dominant uncertainty on BR from relative

Bs,Bhadronization fractions 14%.


Integrated luminosity (fb–1)

BR

(x1

0–9)

Uncertainty in background prediction

Expected final CDF+D0 limit

SM prediction

90% CL limit on BR (only bkg is observed)

Integrated luminosity (fb–1)

5 observation

3 evidence

SM predictionBR

(x1

0–9)

Sensitivity to signal(signal+bkg is observed)

10-7 2x10-8 (~0.05 fb-1)

5x10-9 (~ 0.4 fb-1)

J.Ellis et al. arXiv:0709.0098v1 [hep-ph] (2007)

Within SM BR:2 fb–1 3 evidence 6 fb–1 5 observation

Exclusion:0.5 fb–1 < SM

Bs NUHM


Bd K*

Fast MC, LHCb 2 fb–1

AF

B(s

)

s = m2 [GeV2]

● Zero crossing point of forward-backward asymmetry

AFB in angle, as a function of m, precisely

computed in SM: s0SM(C7,C9)=4.39+0.38

-0.35 GeV2

● BR measured at B-factories, in agreement with SM: BR(BdK*)=(1.22+0.38-0.32)x10-6

● Decay described by three angles (, , K*).

Ignoring non-resonant Kevents

0.5 fb-1 2 fb-1 10 fb-1

σ(s0) 0.8 GeV2 0.5 GeV2 0.3 GeV2● Simple linear fit suggests precision:

hep-ph/0412400

Channel Yield (2 fb-1) B/S

Bs→K*+ – 7200 0.5


● Fitting projections of , , K* angular distributions can measure the fraction of longitudinal polarization FL and the transverse asymmetry AT

(2):

BdK*transverse asymmetries

2 fb–1 10 fb–1

AT(2) 0.42 0.16

FL 0.016 0.007

AFB 0.020 0.008

Stat. precisions in the region s = m2

[1, 6] (GeV/c2)2

where theory calculations are most reliable

Points LHCb 2 fb-1

Sensitivity with

AT(2)

FL

Kruger & Matias, Phys. Rev. D71: 094009,

2500

Under investigation also full angular fit in terms of transversity amplitudes AL,R, A//

L,R, A0

L,R. Will improve precision on AFB.

m2 [GeV2] m2

[GeV2]


Radiative decaysEquivalent of 13mins of simulated bb events – already see a peak!

True K* signal events

Combinatorial background

In SM: Adir=0 (direct CPV) Amix=sin 2 sin AΔ = sin 2 cos with tan=|b→sR| / |b→sL|

With 2fb-1(A) = 0.22 (Adir, Amix )= 0.11

2/cosh2/sinh

)sin()cos()(

ttA

tmAtmAtA

qq

qmix

qdir

CP

As s≠0 Bs probes A, as well as Adir and Amix

For cos≈ 1 A sin 2 determines the fraction of “wrongly” polarized photon.

Bs Time dependent CP asymmetry allows

to test the helicity structure of the emitted photon.

In SM bspredominantly left-handed.

Bd K* AdirCP < 1% in SM, up to 40% in SUSY.

Channel Yield (2 fb-1) B/S

Bd K* 68000 0.6

Bs 11500 <0.5

M(K*)


Charm physics• LHCb will collect a large tagged D*D0

sample (also used for PID calibration). A dedicated D* trigger is foreseen for this purpose.

– Tag D0 or anti-D0 flavour with pion from D*± D0 ±

• Performance studies not as detailed as for B physics.

• Interesting (sensitive to NP) & promising searches/measurements:– Time-dependent D0 mixing with wrong-sign D0K+– decays

stat(x’2) ~0.14 x10–3, stat(y’) ~2 x10–3 with 2 fb–1

– Direct CP violation in D0K+K– • ACP 10–3 in SM, up to 1% with New Physics• Expect stat(ACP) ~ 0.001 with 2 fb–1

– D0+–

• BR 10–12 in SM, up to 10–6 with New Physics• Expect to reach down to ~510–8 with 2 fb–1

D*-tagged signal yield in 2 fb–1 (from b hadrons only)

D0K right sign 12.4 M

D0K+– wrong sign 46.5 k

D0K+K– 1.6 M


LHCb beyond 10 fb–1

- CPV in Bs mixing (tree and penguins)

- angle with 1° precision

- Chiral structure of bs from B and BK*–

● Several measurements limited by stat. precision after 10 fb-1: investigating upgrade of detector to handle luminosity 2x1033 cm–2s–1 and integrate up to 100 fb-1

– Not directly coupled to SLHC machine upgrade since luminosity already available,

but may overlap in time with upgrades of ATLAS and CMS.

● Technical solutions under study (increase trigger efficiency for hadronic modes, fast vertex detection, electronics, radiation dose, pile-up, higher occupancy etc.) Expression of Interest for an LHCb

upgrade submitted to LHCC.

● Physics case:

Expected sensitivity for 100 fb-1 assuming a factor 2 in hadronic trigger efficiency and same reconstruction efficiency


Conclusions

• LHCb is ready for data taking at LHC start-up.

• Very interesting results will come already with first 0.5 fb-1 of data:

Bs J/s measurement with 0.05 precision

Bs BR limit down to SM value

Bd K0*1800events,overtaking B-Factories statistics

• LHCb results will provide in the coming years a strong improvement to flavour physics, in particular to the knowledge of all Bs sector.

• Actively preparing for analysis of several channels with high potential for indirect NP discovery.

Looking forward next HQ&L Conference to show all that!


BACK-UP


from B±→ D0K ± (ADS+GLW) (I)

colour suppressedus

cub

u

B

0D

Ku

su

cbu

B

K

0Dcolour favoured

• Charged B decay

u

du

scu

0D K

Cabibbo favoureddoubly Cabibbo suppressedu

us

dcu

0D

K

Atwood, Dunietz and Soni, Phys. Rev. Lett. 78, 3257 (1997)

• D0 and D0 can both decay into K-π+ (or K+π- )

Weak phase difference –Strong phase difference B Amplitude ratio rB ~ 0.08

Strong phase difference DK

Amplitude ratio rD K=0.060±0.003

))cos(21())((

))cos(21())((

))cos(2())((

))cos(21())((

))cos(2())((

))cos(21())((

2

2

22

22

BBB

hh

D

BBB

hh

D

K

DBDBDB

K

D

K

DBDBDB

K

D

K

DBDBDB

K

D

K

DBDBDB

K

D

rrNKhhB

rrNKhhB

rrrrNKKB

rrrrNKKB

rrrrNKKB

rrrrNKKB

wrong sign, high sensitivity to

right sign, lower sensitivity to

Gronau, London, Wyler, PLB. 253, 483 (1991)

Add CP eigenstate decays D0→K+K–, +–


from B± DK± (ADS+GLW) (II)

Can solve for unknowns, including the weak phase . Add constraint on the relative D0 two body BR and selection efficiencies(know to better than 3%)

Channel Yield 2 fb–1 B/S

B D(K) K favoured 56k 0.6

B D(K) K suppressed 400 2

B D(hh) K 7.8k 1.8

() = 11–14 with 2 fb–1

depending on D strong phases

( Inputs: =60, rB =0.1, B =130, δKπ from Cleo-c)

6 decay rates and 7 parameters (rB, rD, δB, δD, γ , Nhh, NK) . rD well-measured and δD constrained by CLEO-c ( from final statistics expect cosδD~20%)


• Treat with same ADS+GLW method as charged case:

– So far used only D decays to K–+, K+–, K+K– and +– final states

• Envisage also GGSZ analysis

Weak phase difference = Magnitude ratio = rB ~ 0.4

D0

d

b

d

s

c

u

B0

K*0

colour-suppressed

d

b

d

s

u

c

B0

D 0

K*0

colour-suppressed

Decay mode (+cc) 2 fb–1 yield B/S

B0 (K+–)D K*0 3400 0.4–2.0

B0 (K–+)D K*0 540 2.2–13

B0 (K+K–)D K*0 470 < 4.1

B0 (–+)D K*0 130 < 14

() = 9 with 2 fb–1

from B0 D0K*0 (ADS+GLW)

( Inputs: =60, rB =0.4, B =10)


(770)

K*(892)

D0

m2(KS+)

m2 (

KS–

)

from B±D0(Ks)K± (GGSZ)

Amplitude analysis of the D - Dalitz plots for B+ and B– decays allows the extraction

of and rB, δB. Assume no CP violation in D0 decays

B decay amplitudes:

A(BDK) AD(mK2,mK

2)+ rBei(B) AD(mK

2,mK2)

A(BDK) AD(mK2,mK

2)+ rBei(B) AD(mK

2,mK2)

Giri, Grossman, Soffer, Zupan, PRD 68, 050418 (2003).

Mode 2 fb–1 Systematic error

BD(Ks+-)K model-dependent 7°-12° 5-10° (model dependence)

BD(Ks+-)K model-indep. 9°-13° 3°-4° (Cleo-c statistics)

Sensitivity spread due to different background scenarios


BD(Ks+-)K 5000 < 0.7


from B and BsKK

Sensitive to NP in penguins. Measure:

ACP

(t ) Adir cos(m t )Amix sin(m t )

cosh t / 2 A sinh t / 2

2 fb–1

10 fb–1

stat() = 10+ fake solution

stat() = 5+ decreased fake

Adir and Amix depend on d, s, , dei(P/T ratio)

Exploit U-spin symmetry (Fleischer):

Assume: d=dKK and =KK: 4 meas. and 3 unknowns can solve for (taking d, s from other modes) Can relax U-spin requirements:

0.8<dKK/d<1.2 , ,KK free

2 fb–1

Channel Yield 2 fb–1 B/S

B0 36k 0.5

Bs KK 36k 0.15

Competitive with final Tevatron luminosity already for L=0.5fb-1

Advantage of strong PID system to separate Bh+h modes.


RK in B+ K+ℓℓ

001.012max

2

2max

2

4

)(

4

)(

ds

dsR

q

m dseKeBd

q

m dsKBd

K

- Large corrections O(10%) possible in models that distinguish between lepton flavours (eg.MSSM at large tan). Constraints to NP also from RK andBR(Bs→µµ) combined.

in SM (Hiller,Krüger PRD69 (2004) 074020)

LHCb 10 fb-1

Bu eeK 9.2 k events

Bu K 19 k events

stat(RK )= 0.043

• Trigger eff 70% on ee channel

under study - not included.

• Similar sensitivity expected for RK* =Bd K*/ Bd eeK*. 4m

2< mll2< 6 (GeV/c2)2

Documents

Status and Physics reach of LHCb