Large Hadron Collider

Beautiful Physics at LHCLarge Hadron Colliderbeauty Experiment

Content:MotivationTheoretical Introduction LHCb ExperimentLHCb Measurements and expected performance

Precision measurements of loop-dominated B decays as possible probes for New Physics

Ulrich Uwer

Physikalisches Institut Heidelberg

Motivation

Precision B Meson Physics as Probe for New Physics in Loop-Processes:

PhysicsW

New Physics

Box Diagrams (Oscillation) Penguin Decays

Popular New Physics Scenarios: SUSY, Little Higgs Models Deviations from Standard Model predictions

Complementary to direct New Physics searches by ATLAS and CMS

Examples from the past

910)5.02.7()(

)( −−+

⋅±=→

→allKBR

L µµ

ccM θθ cossin~

cθsin

cθcos

GIM Mechanism

Observed branching ratio K0→µµ

In contradiction with theoretical expectation in the 3-Quark Model

Glashow, Iliopolus, Maiani (1970):

Prediction of a 2nd up-type quark, additional Feynman graph cancels the “u box graph”.

ccM θθ cossin~ −

cθcos

cθsin−

More Examples

ARGUS Experiment, 1987:

Observation of B0-B0 Oscillation

0B 0Bb

tdV ∗tbV

tdV∗tbV

Precision electro-weak Physics at the Z

mH< 144 GeV (95% C.L)

mt > 50 GeV

LEWWG March 2007

Pros and Cons

1. Interpretation of precision measurements (CP asymmetries, charge asymmetries, branching ratios) requires good understanding of the “old physics” (Standard Model).

2. Nobel Prizes are generally not awarded for “dubious” conclusions from precision measurements.

Go to ATLAS and CMS ? But are all questions solvable ?

3. New particles / signatures found with ATLAS and CMS must interact with existing particles: What is the flavor structure of NP ? What are the coupling of NP ?

4. Particles at ~1 TeV scale are difficult to be directly observed

Wait for new collider ? Exploit the B Physics Potential of LHC !

Theoretical Introduction

• Quark Mixing and CKM matrix

• Mixing phenomenon

• C, P and CP Violation

• CP Violation in the Standard Model

• Standard Model and Baryon Asymmetry in the Universe

• Measurement of CP Violation

• CKM Metrology

• Rare (Penguin) decays

Quark Mixing in Standard ModelStandard Model Lagrangian:Yukawa coupling between fermions and the Higgs field

Spontaneous symmetry breaking Massive fermions mf ~Yf ⋅υ / √2

For quarks: mass eigenstates different from weak eigenstates

⎟⎟⎟

⎜⎜⎜

⎛∝

)-(1 )t,c,u( 5 CKMVµγγ

⎟⎟⎟

⎜⎜⎜

⎛⋅

⎟⎟⎟

⎜⎜⎜

⎟⎟⎟

⎜⎜⎜

′′′

VVVVVVVVV

tbtstd

cbcscd

ubusud

⎟⎟⎟

⎜⎜⎜

′′′

)-(1 )t,c,u(J 5 µµ γγ

weak massCKM matrix W

d uudV

Charged currents:

CKM Matrix

⎟⎟⎟

⎜⎜⎜

⎟⎟⎟

⎜⎜⎜

VVVVVVVVV

tbtstd

cbcscd

ubusud

⎟⎟⎟

⎜⎜⎜

4 real Parameter = 3 Euler-angles und 1 Phase

complex, unitary 3x3 matrix:

ληρλ

λλλ

ηρλλλ

⎟⎟⎟⎟⎟⎟⎟

⎜⎜⎜⎜⎜⎜⎜

−−−

−−

WolfensteinParametrization

λ, A, ρ, η

λ = sinθc≈ 0.22

Quark Mixing and Flavor Oscillation

0B 0Bb

tdV ∗tbV

tdV∗tbV

⎟⎟⎠

⎞⎜⎜⎝

⎟⎟⎟⎟

⎜⎜⎜⎜

Γ−Γ−

Γ−Γ−=⎟⎟

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛ −=⎟⎟

⎞⎜⎜⎝

⎛⎟⎟⎠

⎞⎜⎜⎝

⎛=⎟⎟

⎞⎜⎜⎝

⎛=⎟⎟

⎞⎜⎜⎝

22221212

*121111

dtdi ΓMH

Diagonal elements:timt eet

Γ−− ⋅⋅= 21

0)( ψψ

Γ=Γ=Γ

CPT mmmHHH

⇒M and Γ hermitian:

Off-diag elements: mixing

Mixing phase φ= arg(m12)

B and B seigenstate Mass

B and B states Flavor≠

Mixing phenomenology decribed by

Flavor and Mass Eigenstates

mBqBpB

Γ−=

122 =+ qp

−=Γ−Γ=∆Γ

=−=∆

Γ∆Γ

∆≡

2und ymx

Mass eigenstates

complex coefficients

Parameters of the mass states

)(Moriond07 64.009.0/)%90(07.0/

(CDF) ps12.078.17

(PDG) ps007.0502.01

±=Γ∆Γ<Γ∆Γ

±=∆

±=∆−

Neutral B mesons

⇒ Diagonalizing Hamitonian:

Flavor states

Mixing of neutral mesons

( )[ ]mteeeBBPBBP ttt HLHL ∆++=→=→Γ+Γ−Γ−Γ− cos2

41)()( 2/0000

( )[ ]( )[ ]mteee

mteeepqBBP

∆−+=→

Γ+Γ−Γ−Γ−

cos241)(

CP, T- violation in mixing: 1)()( 0000 ≠⇒→≠→pqBBPBBP

LH mmm −=∆

B0-B0 Mixing

0 2 4 6 8 10

)cos1(21)( 00 mteBBP t ∆−Γ=→ Γ−

( )mteBBP t ∆+Γ=→ Γ− cos121)( 00

0 1 2 3 4 5 6 7 8 9 10B

)()()()(

BBPBBPBBPBBP

→+→

→−→

Bt τ/

LH mmm −=∆

) (mit ΓΓΓ LH ≈≈

m∆πOscillation Frequency

Standard Model Prediction

0B 0Bb

tdV ∗tbV

tdV∗tbV

⎟⎟⎠

⎞⎜⎜⎝

⎛=∆ ∗

tBWtbtdBBB

mFmVVBfmGm ηπ e.w. correction

222 )1233235( MeVBf BB ±±=

NLO QCD

01.055.0 ±=Bη

from lattice QCD

tsV ∗tbV

tsV∗tbV

2)(~ tbtss VVm ∗∆

00dd BB −

00ss BB −

B0 Oscillation

-1ps004.0006.0506.0 ±±=∆ dmB

0.774τ

dm∆π

(BABAR mean value March 2006)

-1ps)syst.(07.0)stat.(10.077.17 ±±=∆ smB

(CDF Collaboration, September 2006)

00dd BB −

00ss BB −

Discrete Symmetries

+ −Charge conjugation CParticle ⇔ Anti-particle γγ →

→ +− ee

Parity P

−→−→

Time inversion Ttt −→

Weak Interaction: P, C and CP Symmetry

−π−τ

While the weak interaction violates C and P maximally, CP was thought to be a good symmetry until 1964, when CPV was observed in K decays:

−π−τ

RτνP

+π+τ

Lτν P+π

+τRτν

Small (10-3) effect !

CP Violation in B Meson DecaysSummer 2001

CP Violation in B decays:

CP Asymmetry „70 % effect“

CP violation is observed in many B decays with loop-contributions but also in tree-dominated decays.

))(())(())(())(()( 00

tfBtfBtfBtfBtACP →Γ+→Γ

→Γ−→Γ=

BR ~ 4x10-4

S00 KJ/)B(B ψ→

CP Violation in the Standard Model

⎟⎟⎟

⎜⎜⎜

⎟⎟⎟

⎜⎜⎜

⎟⎟⎟

⎜⎜⎜

VVVVVVVVV

tbtstd

cbcscd

ubusud

Quarks:

Anti-quarks:

⎟⎟⎟

⎜⎜⎜

⎟⎟⎟

⎜⎜⎜

=⎟⎟⎟

⎜⎜⎜

VVVVVVVVV

tbtstd

cbcscd

ubusud

d ttdV

CP Violation ⇔ complex matrix elements

∗tdVd t

Unitarity Triangle

⇒ Vud Vub + Vcd Vcb + Vtd Vtb = 0***

Unitarity triangle „bd“

γ1 11 1 1

⎛ ⎞⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠

CKM Phases

)( 4λO+CP Violation if Triangle has finite area !

Standard Model & Baryon-Asymmetry

Sacharow Conditions:

• Baryon number violation

• C und CP violation

• Deviation from thermal equilibrium

Explains the Standard Model the Baryon-Asymmetry of the Universe ?

• CP Violation in quark sector by faktor ~1010 too small.• For MHiggs> 114 GeV: Symmetry breaking = 2nd order phase transition

Attractive: SUSY extensions of the Standard Model

• Additional CP Violation

• extended Higgs-Sector→ strong phase transition

Alternatives: Lepto-Baryogenesis

Measurement of CP violating Phases

δφ ii eeA CP2

fB →

)cos(2 21

δφ ++

δφ ii eeA CP−2

fB →

)cos(2 21

δφ −+

„Golden“ Decay B0→J/ψKs

sKJB ψ/0 → sKJB ψ/0 →CP

0 KK →

ψ/J0B

s0 KK →

ηCP=-1

0B 0Bb

tdV tbV

tdVtbV

Mixing Phase:

βφ 2ii ee d =

„Golden“ Decay B0→J/ψKs

sKJB ψ/0 →

)sin( β2sin))(/())(/())(/())(/()( 00

mttKJBtKJBtKJBtKJBtA

ssCP ∆=

→Γ+→Γ→Γ−→Γ

=ψψψψ

Aβ2ie

sKJ ψ/0B

))(/( 0 tKJB sψ→Γ ))(/( 0 tKJB sψ→Γ≠

ηCP=-1

sKJB ψ/0 →

CKM Phases from CPV in B Decays

00 / :CPV SKJB ψ→

ρρρπππ ,, :CPV 0 →B

DKDKDKB

,,,:CPV0

→ ∗ ππ

Very rare decays → several 109 B mesons necessary

„Golden channel“

Over-constrain the Unitarity Triangle !

CKM Metrology

oo 0.13.21 ±=β %)4(026.0674.02sin ±±=β

With BABAR/BELLE difficult:o

2460 ±=γ

World Averageoo 1093 ±=α

CKM Metrology

CKM Mechanism is primary source of CP violation in quark sector.Test of New Physics needs high precision measurements of α,β γ.

Further New Physics Searches

gtcu ,,

Pinguin-Graphen

T. Hurth

CPV in Penguin suppressed decays:

sKBB φ→)( 00

φφ→)( 00ss BB

Bs mixing diagrams (non SM phases):

φψ/)( 00 JBB ss →

Rates of rare decays:

ll)(0 ∗→ KB

µµ→0)(sB

910~ −BR

610~ −BR (visible)

5103~ −×BR (visible)

B Physics at the LHC

B Prodcution at LHC:

pp @ 14 TeV → σbb ≈ 500 µb

40% B0/B+, 10% Bs, 10% b-baryons

but 40 MHz IA rate, σinel ≈ 80 mb

B Physics Program

Dedicated B Experiment

B Production at LHC

• pp collisions at √s = 14 TeV

• Forward production of bb, correlated

• for L ~ 2 x 1032 cm-2s-1

(defocused beams at LHCb IP)

~1012 b⎯b events/yr produced

• Single arm forward spectrometer 12 mrad < θ < 300 mrad(1.8<η<4.9)

σinel ~ 80 mbσbb ~ 500 µb

bb production:(forward!)

θb θb

parton 1

parton 2

~ 35 %

B Physics & LHC Detectors

LHCb:• designed to maximize B acceptance• Forward, single arm spectrometer, 1.9 < η < 4.9

(bb pairs correlated, mainly forward)• Excellent vertexing and particle ID (K/π separation)• “lower” pT triggers, including purely hadronic

modes, very flexible• Luminosity tuneable by adjusting beam focus:

run at L ~ 2×1032 cm–2s–1 → n≈0.5

ATLAS/CMS:• optimized for high-pT discovery physics• central detectors, |η|<2.5• B physics using high-pT muon triggers,

Purely hadronic modes triggered by “opposite” tagging muon

• aim for highest possible luminosities: expect L<2×1033 cm–2s–1 for first 3 yr → n=5(afterwards L~ 1033 cm–2s–1 → n=25) 1

-2 0 2 4 6

eta of B-hadron

ATLAS/CMS

LHCb100 µb230 µb

Pythia production cross section

Luminosity [cm−2 s−1]1031 1032 1033

n = # of pp interactions/crossing

Typical Event

b-hadron

pp interaction(primary vertex)

• Decay length L typical ~ 7 mm • Decay products with p ~ 1–100 GeV• Trigger on “low pt” particles (similar to backgr)

Typical Event

b-hadron

pp interaction(primary vertex)

all 25 ns

Simulated Event

LHCb DetectorAcceptance: 15-300 mrad (bending)

15-250 mrad (non-bending)

RICH1RICH2

Calorimeters

Muon System

Magnet

Tracking stations(inner and outer)

LHCb detector

~ 300 mrad

10 mrad

Forward spectrometer (running in pp collider mode)Inner acceptance 10 mrad from conical beryllium beam pipe

LHCb detector

Vertex locator around the interaction regionSilicon strip detector with ~ 30 µm impact-parameter resolution

Vertex detector

• 21 stations w/ double sided silicon sensors •micro-strip sensors with rφ geometry, • approach to 8 mm from beam (inside complex secondary vacuum system)

Vertex Reconstruction

Bs → Ds(K K π ) π

47µm144 µm

440 µmBs0( )

mm7=L Proper time resolution

+−→ πss DB0

σ ~ 42 fstcL βγ=

Life time information is used in the trigger !

LHCb detector

Tracking system and dipole magnet to measure angles and momenta∆p/p ~ 0.4 %, mass resolution ~ 14 MeV (for Bs → DsK)

Warm Magnet, 4.2 MW, 4 Tm,

T1 T2 T3

OuterTracker

264 Module

Main Tracking Stations

Inner Tracker: Silicon sensors

Cross to optimize occupancy for OT

6.3 %side6.6 %corner5.4 %top4.3 %average

OT occupancy

1.3% area 20% tracks

Outer Tracker

pitch 5.25 mm

5mm cellsTrack

Straw tube drift chamber modules

Straw tube winding:

Lamina Dielectrics Ltd.2.5 m

Cathode

Outer Tracker

LHCb detector

Two RICH detectors for charged hadron identification

RICH = Ring Imaging CHerenkov Detector

Cherenkov Radiation

>β if

Ring Imaging

)(1cos c nβθ =

Ring radius → θc → β

RICH detectors are the specialized detectors to allow charged hadron(π, K, p) identification.

Important for B physics, as there are many hadronic decay modes e.g.: Bs → Ds

- K+ → (K+ K-π-) K+

Since ~7× more π than K are produced in pp events, making the mass combinations would give rise to large combinatorial background unless K and π tracks can be separated

θ C (

01 10 100

Momentum (GeV/c)

Aerogel

C4F10 gas

CF4 gas

242 mrad

53 mrad

32 mrad

θC max

3 radiators to coverfull momentum range

Particle Identification

RICH 1 RICH 2

Radiator: AerogelC4F10

Radiator: CF4

-60 -40 -20 0 20 40 60x (cm)

n=1.0005 n=1.03 n=1.0014

θ C (

01 10 100

Momentum (GeV/c)

Aerogel

C4F10 gas

CF4 gas

242 mrad

53 mrad

32 mrad

θC max

3 radiators to coverfull momentum range

Particle Identification

RICH 1 RICH 2

Radiator: AerogelC4F10

Radiator: CF4

ε (K K) = 88%

ε (π K) = 3%

n=1.0005 n=1.03 n=1.0014

Background suppression with PID

purity 13%

purity 7%

purity 84% efficiency 79%

purity 67% efficiency 89%

Bs→ Ds K

Bs→ K K

No RICH With RICH

LHCb detector

Calorimeter system to identify electrons, hadrons and neutralsImportant for the first level (Level 0) of the trigger.

LHCb detector

Muon system to identify muons, also used in first level (L0) of the trigger

LHCb Detector

Trigger Level-0

CalorimeterMuon system

Pile-up system

LevelLevel--0 Hardware0 Hardware: (4: (4µµs)s)High High ppTT µµ, , ee, , hh, , γγ signatures signatures

1.11.1, , 2.82.8, , 3.63.6, , 2.62.6 GeVGeV40 MHz 1 MHz

PC Farm:

Higher Level Trigger (full event info)

Higher Level Trigger

B (data mining)Trigger Inclusive b (e.g. b→µ)900 HzCharm (mixing & CPV)PIDD* candidates300 Hz

J/ψ, b→J/ψX (unbiased)TrackingHigh mass di-muons600 Hz

B (core program)TaggingExclusive B candidates200 HzPhysicsCalibrationEvent typeHLT rate

Storage (event size ~ 50 kB)

L0, HLT and L0×HLT efficiency

Higher Level Trigger (Software)

Stepwise event reconstruction:• Confirmation of trigger signature

using tracking chambers• Secondary vertex reconstruction• Full event reconstruction

Necessary Tool: B Flavor Tagging

~6~4Combined B0 (decay dependent:

Combined Bs trigger + select.)

2.13318Frag. kaon (Bs)1.04024Vertex Charge2.43117Kaon0.4365Electron1.03511Muon

εeff (%)w (%)εTag (%)Tag

Signal B (same side tagging)

Tagging B (opposite tagging)• lepton • kaon• Vertex charge

• Fragmentation kaon near Bs

Dilution form oscillation if B0+l

Mistag rate

Dilution D=(1-2w)Effective Tagging Power

εeff=εTagD2

LHCb - Expected Physics Performance

sin(2β) - the reference measurement

Bs – mixing

∆ms with Bs0 → Dsπ

φs and ∆Γs with B0s→ J/ψφ (η)

Measurement of γ

Rare decays

• Bs0 → µ+µ-

• Exclusive b → s µ+µ-

sin(2β) in B0→J/ψKs

• sin(2β) will be measured very precisely at e+e- B factories. Expect. for 2008: σ(sin2β)~0.02

• Not a primary goal for LHCb. Measurement will serve as reference:

0 1 2 3 4 5 6 7 8 9 10-0.8

Proper time (ps)

(background subtracted)

2 fb-1 (1 yr)

245k events

⇒ σstat(sin2β) ~ 0.02

(for 2 fb-1, 1 yr))sin( β2sin

)sin( )(sin

))(/())(/())(/())(/(

tKJBNtKJBNtKJBNtKJBN

→+→→−→

ψφφ

ψψψψ

sin(2β) in Penguin Decays

000 K)B(B φ→

)sin( β2sin)( mttACP ∆=

Standard Model SUSY contributions

)sin(β2sin)( eff mttACP ∆=

)Kβ(J/2sin sψ= ≠ effβ2sin

LHCb Measurement of Penguin Decays

Experimental status (2006)• sin(2β) in penguin decays always

lower than sin(2β) in B0→J/ψKs

• Statistics ? Need more data !

σstat(sin2β) =0.12…0.18 (10 fb-1, 5 yr) ~4000 evts

Similar:

04.0:)(

stat ±≈

σφφsCP BA

Second triangle accessible at LHCb

⎟⎟⎟

⎜⎜⎜

tbtstd

cbcscd

ubusud

VVVVVVVVV

„bd“

0)1()( 333 =−−+−+ ηρλληρλ iAAiA

0=++ ∗∗∗tbtdcbcdubud VVVVVV

„tu“

0)()1( 333 =++−−− ηρλληρλ iAAiA

0=++ ∗∗∗tbubtsustdud VVVVVV

)( 3λO

Same triangle !

Different in O(λ5)

„bd“

0)1()( 333 =−−+−+ ηρλληρλ iAAiA0=++ ∗∗∗

tbtdcbcdubud VVVVVV

)(21)(

21 55 ηρληρλ iAiA +++−

)( 7λO+

VVVVη

„tu“

0)()1( 333 =++−−− ηρλληρλ iAAiA

0=++ ∗∗∗tbubtsustdud VVVVVV

))(21())(

21( 55 ηρληρλ iAiA +−++−−

21 ρλλ

2ηλ∆γ

02.0≈−′=′−=∆ ββγγγ 3λAVV tsus

1(2λρρ −⋅=)

2ληη −⋅=

)( 7λO+

Very small in SM

Bs Mixing

pq φ−== or 1

LH mmmΓ−Γ=∆Γ

−=∆

⎟⎟⎠

⎞⎜⎜⎝

⎟⎟⎟⎟

⎜⎜⎜⎜

Γ−Γ−

Γ−Γ−=⎟⎟

⎞⎜⎜⎝

⎛=⎟⎟

⎞⎜⎜⎝

22221212

*121111

dtdi H

⎟⎟⎟⎟

⎜⎜⎜⎜

Γ−∆Γ−∆

∆Γ−∆−Γ−

2imime

O(0.1)·ΓsO(0.01)·Γd∆Γ=ΓH-ΓL

17.8 ps-10.5 ps-1∆m=mH-mL

β2)arg( =∗tdtbVV γ∆=∗ 2)arg( tstbVV

tsV ∗tbV

tsV∗tbV

(if CPV in mixing is ignored)

In SM small: 0.04

Measurement of Bs Mixing

LHCb expects 80k Bs→Dsπ events in 1 yr

5σ measurement w/ less than 1 month of good data possible !

Proper time (ps)E

0 1 2 3 4 5

Perfect reconstruction

Proper time (ps)E

0 1 2 3 4 5

Perfect reconstruction+ flavour tagging

Proper time (ps)E

0 1 2 3 4 5

Perfect reconstruction+ flavour tagging+ proper time resolution

Proper time (ps)

0 1 2 3 4 5

Perfect reconstruction+ flavour tagging+ proper time resolution+ background

Proper time (ps)E

0 1 2 3 4 5

Perfect reconstruction+ flavour tagging+ proper time resolution+ background+ acceptance

Bs→Dsπ

2 fb-1 (1 yr) of data ∆ms=20 ps-1

Bs oscillates about 26 times until it decays: need excellent proper time resolution to resolve the mixing. LHCb: 44 fs

Bs mixing has been observed at Tevatro

Observation of Bs mixing is basis for time dependent CP asymmetry measurements.

∆Γs and Bs→J/ψφ

As φs is small in the SM (0.04):

Mass eigenstates are CP eigenstates

)even CP(B)B(CP

)odd CP(B)B(CP

ψφ/)B(B ss J→

−−= 1PCJ

LJJ )1)((CP)/(CP)/(CP −= φψψφL=0,2 → CP even L=1 → CP odd

Final state is mixture of CP even/odd.

Interference between Mixing and Decay

φθφθ

θφθ

φθφθ

θφθ

θφθψφ

sin)sin(),,(f

)sin(),,(f

sin)(),,(f

),,(f)/B/B(

∆⋅⋅±

⋅−⋅+

⋅=→Γ

Γ−Γ−

Simultaneous determination of ∆Γ and φs

Measurement possible as tagged and untagged analysis!

Expected Constraints for φs

Expect 130k recon. Bs→J/ψφ events/yrεtot=1.6%, B/S<0.1, σct=37 fs, εD2=5.5%

Expectation:%2)/(

06.002.0)(sin

=Γ∆Γ

σφσ s

Constraints on new physics

W New Physics

SMssss mihm ∆+=∆ ))2exp(1( σ

Measurement of γ with B→DK decays

γiubub eVV −= ||

CKM +Color suppressed

Interference ⇒ direct CPV (i.e. in decay) ⇒ γ

In lowest order, there is no loop diagram !!

Gronau and Wyler

ADS Method (Atwood,Dunietz,Soni)B±→D0K± w/ D0→[K+π-] & D0→[K-π+]

Dalitz Method (Giri,Grossman,Soffer,Zupan)B±→D0K± w/ D0→[K0

sπ+π-]

Dunietz+GW Method (Gronau,Wyler,Dunietz)B0→D0

CP K*0 w/ D0CP →K+K- σ(γ)≈8o

σ(γ)≈5o

LHCb (2fb-1)

Studies ongoing: 2007

σ(γ)≈20oσ(γ)≈8o ?

σ(γ)≈5o

Measurements of γ with Bs decays

Measure γ + φs from 4 time-dependent rates: Bs→Ds

− K+ and Bs→Ds+K−

(+ CP-conjugates) → strong phase difference δUse φs from Bs→J/ψφ

Time dependent CP asymmetries in Bs→DsK

5 yrs of data, ∆ms=20 ps-1

t [ps]

K− )

−0.5

−0.25

0 0.5 1 1.5 2 2.5 3 3.5 4

Bs→Ds+K−

σ(γ) ~ 13o (2fb-1 1yr)

Feynman tree diagrams

γδ−iesie φ−

γδ+ie

−+KDs

+−KDs)(0 tBs

)(0 tBs

)0(0sB

+K−sD

0sB −K

Interference between direct decayand decay after oscillation

LHCb Measurement of CKM Angle γ

γ from B→DK at LHCb (10 fb–1)

Two possible scenarios

γloops (2006)

CKM Metrology and LHCb

%7.4/)(%17/)(

ηησρρσ

Summer 2006

ρ-1 -0.5 0 0.5 1

sm∆dm∆ dm∆

KεcbVubV

ρ-1 -0.5 0 0.5 1

%7.1/)(%5.3/)(

=ηησ=ρρσ

LHCb at L=10fb-1

Rare B Decays Bs,d→µµ

2 fb–1 ⇒ 3σ evidence of SM signal10 fb–1 ⇒ >5σ observation of SM signal

s µ +

tµ−

SM Branching ratio: BR(Bs→µ+µ-) = (3.5 ± 0.9) ×10–9

BR(Bd→µ+µ-) = (1.0 ± 0.5) ×10–10

Large contribution from SUSY

Limits from CDF+D0: BR ~ 1×10–7 LHCb Sensitivity(signal+bkg is observed)

Integrated Luminosity (fb-1)

SM prediction

0 1 2 3 4 5 6 7 8 9 10

LHCb Mass resolution ∆mµµ≈18 MeV

0B 0∗KW

Z/γµ

Rare B0 → K*0µ+µ− decays

s = (mµµ)2 [GeV2]

AFB(s), theory AFB(s), fast MC, 2 fb–1

s = (mµµ)2 [GeV2]

µ– Κ∗

Β0 θ

In Standard Model: Suppressed by loop decay: BR ~1.2×10–6

Forward-backward asymmetry AFB(s) In the µµ rest-frame is sensitive probe of New Physics

0B 0∗KW

Z/γµ

New Physics

LHCb - Conclusion

LHCb is a dedicated experiment to exploit the enormous B production rate at LHC: excellent vertexing and PID, good tracking, flexible trigger.

Precision measurement of loop-suppressed B decays at LHC opens a window to look for New Physics.

This approach is complementary to the direct searches of New Physics at ATLAS and CMS.

Numbers

Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty...

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