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Beautiful Physics at LHC Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements and expected performance Precision measurements of loop-dominated B decays as possible probes for New Physics Ulrich Uwer Physikalisches Institut Heidelberg

Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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Page 1: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Beautiful Physics at LHCLarge Hadron Colliderbeauty Experiment

b s

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

Page 2: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Motivation

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

WNew

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

Page 3: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Examples from the past

910)5.02.7()(

)( −−+

⋅±=→

→allKBR

KBRL

L µµ

ccM θθ cossin~

0Kd

−µ

+µW

W

su

cθsin

cθcos

µν

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”.

0Kd

−µ

+µW

W

sc

ccM θθ cossin~ −

cθcos

cθsin−

µν

Page 4: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

More Examples

ARGUS Experiment, 1987:

Observation of B0-B0 Oscillation

0B 0Bb

d

dv

bt

t

uc

uc

tdV ∗tbV

tdV∗tbV

Precision electro-weak Physics at the Z

mH< 144 GeV (95% C.L)

mt > 50 GeV

LEWWG March 2007

Page 5: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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 !

Page 6: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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

Page 7: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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

⎟⎟⎟

⎜⎜⎜

⎛∝

bsd

)-(1 )t,c,u( 5 CKMVµγγ

⎟⎟⎟

⎜⎜⎜

⎛⋅

⎟⎟⎟

⎜⎜⎜

⎛=

⎟⎟⎟

⎜⎜⎜

′′′

bsd

VVVVVVVVV

bsd

tbtstd

cbcscd

ubusud

⎟⎟⎟

⎜⎜⎜

′′′

∝+

bsd

)-(1 )t,c,u(J 5 µµ γγ

weak massCKM matrix W

d uudV

Charged currents:

Page 8: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

CKM Matrix

⎟⎟⎟

⎜⎜⎜

⎟⎟⎟

⎜⎜⎜

⎛=

bsd

VVVVVVVVV

tbtstd

cbcscd

ubusud

⎟⎟⎟

⎜⎜⎜

'''

bsd

d s b

u

C

t

4 real Parameter = 3 Euler-angles und 1 Phase

complex, unitary 3x3 matrix:

( )4

23

22

32

1)1(2

1

)(2

1

λ

ληρλ

λλλ

ηρλλλ

O

AiA

A

iA

+

⎟⎟⎟⎟⎟⎟⎟

⎜⎜⎜⎜⎜⎜⎜

−−−

−−

−−

=CKMV

WolfensteinParametrization

λ, A, ρ, η

λ = sinθc≈ 0.22

Page 9: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Quark Mixing and Flavor Oscillation

0B 0Bb

d

dv

bt

t

uc

uc

tdV ∗tbV

tdV∗tbV

⎟⎟⎠

⎞⎜⎜⎝

⎟⎟⎟⎟

⎜⎜⎜⎜

Γ−Γ−

Γ−Γ−=⎟⎟

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛ −=⎟⎟

⎞⎜⎜⎝

⎛⎟⎟⎠

⎞⎜⎜⎝

⎛=⎟⎟

⎞⎜⎜⎝

⎛=⎟⎟

⎞⎜⎜⎝

⎛0

0

22221212

*12

*121111

0

0

0

0

2212

21110

0

0

0

22

222 B

Bimim

imim

BBi

BB

HHHH

BB

BB

dtdi ΓMH

Diagonal elements:timt eet

Γ−− ⋅⋅= 21

0)( ψψ

Γ=Γ=Γ

==

==

2211

2211

2211

CPT mmmHHH

⇒M and Γ hermitian:

*1221

*1221

Γ=Γ

= mm

Off-diag elements: mixing

Mixing phase φ= arg(m12)

LH

00

B and B seigenstate Mass

B and B states Flavor≠

Mixing phenomenology decribed by

Page 10: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Flavor and Mass Eigenstates

HHH

LLL

mBqBpB

mBqBpB

Γ−=

Γ+=

,00

,00

with

with

122 =+ qp

2112

2112

2112,

2112,

Im4

Re2

Im2

Re

HH

HHmmm

HH

HHmm

LH

LH

LH

LH

−=Γ−Γ=∆Γ

=−=∆

Γ=Γ

±=

m

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

1

±=Γ∆Γ<Γ∆Γ

±=∆

±=∆−

ss

s

d

CLm

m

Neutral B mesons

)(21

)(21

0

0

HL

HL

BBq

B

BBp

B

−=

+=

⇒ Diagonalizing Hamitonian:

Flavor states

Page 11: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Mixing of neutral mesons

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

41)()( 2/0000

( )[ ]( )[ ]mteee

qpBBP

mteeepqBBP

ttt

ttt

HLHL

HLHL

∆−+=→

∆−+=→

Γ+Γ−Γ−Γ−

Γ+Γ−Γ−Γ−

cos241)(

cos241)(

2/2

00

2/2

00

CPT

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

LH mmm −=∆

Page 12: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

B0-B0 Mixing

0

0,2

0,4

0,6

0,8

1

1,2

0 2 4 6 8 10

)cos1(21)( 00 mteBBP t ∆−Γ=→ Γ−

( )mteBBP t ∆+Γ=→ Γ− cos121)( 00

-1,5

-1

-0,5

0

0,5

1

1,5

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

)()()()(

0000

0000

BBPBBPBBPBBP

→+→

→−→

Bt τ/

LH mmm −=∆

) (mit ΓΓΓ LH ≈≈

m∆πOscillation Frequency

Page 13: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Standard Model Prediction

0B 0Bb

d

dv

bt

t

uc

uc

tdV ∗tbV

tdV∗tbV

⎟⎟⎠

⎞⎜⎜⎝

⎛=∆ ∗

2

2222

2

2

)(6 W

tBWtbtdBBB

Fd m

mFmVVBfmGm ηπ e.w. correction

222 )1233235( MeVBf BB ±±=

NLO QCD

01.055.0 ±=Bη

from lattice QCD

0sB 0

sBb

s

s

bt

t

tsV ∗tbV

tsV∗tbV

2)(~ tbtss VVm ∗∆

00dd BB −

00ss BB −

Page 14: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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

26τ

(CDF Collaboration, September 2006)

00dd BB −

00ss BB −

Page 15: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Discrete Symmetries

+ −Charge conjugation CParticle ⇔ Anti-particle γγ →

→ +− ee

Parity P

LL

pprr

rr

rr

rr

−→−→

Time inversion Ttt −→

Page 16: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Weak Interaction: P, C and CP Symmetry

−π−τ

Lτν

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

C

+π+τ

Lτν P+π

+τRτν

C

Small (10-3) effect !

Page 17: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

CP Violation in B Meson DecaysSummer 2001

CP Violation in B decays:

CP Asymmetry „70 % effect“

BABAR

Ere

igni

sse

Rel

at. A

ntei

l

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

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

00

tfBtfBtfBtfBtACP →Γ+→Γ

→Γ−→Γ=

BR ~ 4x10-4

S00 KJ/)B(B ψ→

Page 18: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

CP Violation in the Standard Model

⎟⎟⎟

⎜⎜⎜

⎟⎟⎟

⎜⎜⎜

⎛=

⎟⎟⎟

⎜⎜⎜

bsd

VVVVVVVVV

bsd

tbtstd

cbcscd

ubusud

'''

Quarks:

Anti-quarks:

⎟⎟⎟

⎜⎜⎜

⎟⎟⎟

⎜⎜⎜

=⎟⎟⎟

⎜⎜⎜

bsd

VVVVVVVVV

bsd

tbtstd

cbcscd

ubusud

***

***

***

'''

W

d ttdV

CP Violation ⇔ complex matrix elements

W

∗tdVd t

CP

Page 19: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Unitarity Triangle

Vud

Vcd

Vtd

Vus

Vcs

Vts

Vub

Vcb

Vtb

=100

010

001

Vud

Vus

Vub

Vcd

Vcs

Vcb

Vtd

Vts

Vtb

*

*

*

*

*

*

*

*

*

⇒ Vud Vub + Vcd Vcb + Vtd Vtb = 0***

Vud

Vus

Vub

Vcd

Vcs

Vcb

Vtd

Vts

Vtb

*

*

*

*

*

*

*

*

*

Vud

Vcd

Vtd

Vus

Vcs

Vts

Vub

Vcb

Vtb

=100

010

001

Unitarity triangle „bd“

β

-i

-i

γ1 11 1 1

1 1

e

e

⎛ ⎞⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠

b u

t d

CKM Phases

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

Page 20: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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 ?

NoNo

• 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

Page 21: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Measurement of CP violating Phases

1AfB

δφ ii eeA CP2

fB →

)cos(2 21

22

21

2

δφ ++

+=

CPAA

AAA

CP

1AfB

δφ ii eeA CP−2

fB →

)cos(2 21

22

21

2

δφ −+

+=

CPAA

AAA

Page 22: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

„Golden“ Decay B0→J/ψKs

sKJB ψ/0 → sKJB ψ/0 →CP

0B

b

d

c

cs

cbV

csVs

0 KK →

ψ/J0B

b

d

c

cs

cbV

csV

s0 KK →

ψ/J

ηCP=-1

0B 0Bb

d

dv

bt

t

uc

uc

tdV tbV

tdVtbV

Mixing Phase:

βφ 2ii ee d =

Page 23: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

„Golden“ Decay B0→J/ψKs

sKJB ψ/0 →

)sin( β2sin))(/())(/())(/())(/()( 00

00

mttKJBtKJBtKJBtKJBtA

ss

ssCP ∆=

→Γ+→Γ→Γ−→Γ

=ψψψψ

A

Aβ2ie

sKJ ψ/0B

0B

CP

))(/( 0 tKJB sψ→Γ ))(/( 0 tKJB sψ→Γ≠

ηCP=-1

sKJB ψ/0 →

Page 24: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

CKM Phases from CPV in B Decays

β

α

γ

00 / :CPV SKJB ψ→

ρρρπππ ,, :CPV 0 →B

KKKDB

DKDKDKB

ss

s

,

,,,:CPV0

*0)(0

→ ∗ ππ

0 1

Im

Very rare decays → several 109 B mesons necessary

„Golden channel“

Over-constrain the Unitarity Triangle !

Page 25: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

CKM Metrology

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

With BABAR/BELLE difficult:o

oo 38

2460 ±=γ

β

α

γ

World Averageoo 1093 ±=α

Page 26: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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.

Page 27: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Further New Physics Searches

W

b

dd

u

u

d

gtcu ,,

B0

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

s

ss

φ

0K

910~ −BR

610~ −BR (visible)

5103~ −×BR (visible)

Page 28: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

B Physics at the LHC

ATLAS

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

B Physics Program

Dedicated B Experiment

Page 29: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

B Production at LHC

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

LHCb

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

σinel ~ 80 mbσbb ~ 500 µb

bb production:(forward!)

θb θb

p

parton 1

b

b

Boost

p

parton 2

~ 35 %

Page 30: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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

10

10 2

-2 0 2 4 6

eta of B-hadron

pT

of

B-h

adro

n

ATLAS/CMS

LHCb100 µb230 µb

Pythia production cross section

1

23

4

0

Luminosity [cm−2 s−1]1031 1032 1033

0.2

0.4

0.6

0.8

1.0

Prob

abili

ty

n = # of pp interactions/crossing

LHC

b

n=0

n=1

ATL

AS

/CM

S

Page 31: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Typical Event

b-hadron

π+

l −

Κ−

π+

π+

π−

B0

pp interaction(primary vertex)

L

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

Page 32: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Typical Event

b-hadron

π+

l −

Κ−

π+

π+

π−

B0

pp interaction(primary vertex)

L

all 25 ns

Simulated Event

Page 33: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

LHCb DetectorAcceptance: 15-300 mrad (bending)

15-250 mrad (non-bending)

RICH1RICH2

Calorimeters

Muon System

VELO

Magnet

Tracking stations(inner and outer)

20 m

Page 34: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

LHCb detector

p p

~ 300 mrad

10 mrad

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

Page 35: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

LHCb detector

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

Page 36: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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)

Beam

Page 37: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Vertex Reconstruction

Bs → Ds(K K π ) π

K-Ds

±

π+

K+

π±

47µm144 µm

440 µmBs0( )

mm7=L Proper time resolution

+−→ πss DB0

σ ~ 42 fstcL βγ=

Life time information is used in the trigger !

Page 38: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

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,

Page 39: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

T1 T2 T3

OuterTracker

264 Module

6 m

5 m

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

Page 40: Large Hadron Collider - Physikalisches Institutuwer/lectures/... · Large Hadron Collider beauty Experiment b s Content: Motivation Theoretical Introduction LHCb Experiment LHCb Measurements

Outer Tracker

pitch 5.25 mm

5mm cellsTrack

e- e

-e-

Straw tube drift chamber modules

Straw tube winding:

Lamina Dielectrics Ltd.2.5 m

Cathode

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Outer Tracker

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LHCb detector

Two RICH detectors for charged hadron identification

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RICH = Ring Imaging CHerenkov Detector

Cherenkov Radiation

nc

>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

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θ C (

mra

d)

250

200

150

100

50

01 10 100

Momentum (GeV/c)

Aerogel

C4F10 gas

CF4 gas

p

K

π

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

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

y (

cm)

n=1.0005 n=1.03 n=1.0014

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θ C (

mra

d)

250

200

150

100

50

01 10 100

Momentum (GeV/c)

Aerogel

C4F10 gas

CF4 gas

p

K

π

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

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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

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LHCb detector

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

e

h

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LHCb detector

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

µ

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LHCb Detector

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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)

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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

1 MHz

2 KHz

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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

B0

B0 D

π+

π−

K-

b

b

s

u

s

u

Bs

Κ+

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

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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-

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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

-0.6

-0.4

-0.2

0

0.2

ACP

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

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

)(

KJ/d

00

00

mt

mt

tKJBNtKJBNtKJBNtKJBN

tA

ss

ss

CP

∆=

∆+=

→+→→−→

=

ψφφ

ψψψψ

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sin(2β) in Penguin Decays

000 K)B(B φ→

b

dg

t

d

s

s

s0B

φ

0K

)sin( β2sin)( mttACP ∆=

g~

q~

d g

s0B

φ

0K

Standard Model SUSY contributions

)sin(β2sin)( eff mttACP ∆=

)Kβ(J/2sin sψ= ≠ effβ2sin

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LHCb Measurement of Penguin Decays

LHCb:

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

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Second triangle accessible at LHCb

⎟⎟⎟

⎜⎜⎜

⎛=

tbtstd

cbcscd

ubusud

VVVVVVVVV

V

„bd“

0)1()( 333 =−−+−+ ηρλληρλ iAAiA

0=++ ∗∗∗tbtdcbcdubud VVVVVV

„tu“

0)()1( 333 =++−−− ηρλληρλ iAAiA

0=++ ∗∗∗tbubtsustdud VVVVVV

)( 3λO

Same triangle !

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Different in O(λ5)

„bd“

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

tbtdcbcdubud VVVVVV

)(21)(

21 55 ηρληρλ iAiA +++−

)( 7λO+

β

α

γ

*

*

cbcd

ubud

VVVV

*

*

cbcd

tbtd

VVVVη

0 1

Im

ρ Re

„tu“

0)()1( 333 =++−−− ηρλληρλ iAAiA

0=++ ∗∗∗tbubtsustdud VVVVVV

))(21())(

21( 55 ηρληρλ iAiA +−++−−

β′

α

γ′

η

0 1

Im

ρ Re

22

21 ρλλ

+−

2ηλ∆γ

02.0≈−′=′−=∆ ββγγγ 3λAVV tsus

)2

1(2λρρ −⋅=)

21(

2ληη −⋅=

)( 7λO+

Very small in SM

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Bs Mixing

siepq

pq φ−== or 1

LH

LH mmmΓ−Γ=∆Γ

−=∆

⎟⎟⎠

⎞⎜⎜⎝

⎟⎟⎟⎟

⎜⎜⎜⎜

Γ−Γ−

Γ−Γ−=⎟⎟

⎞⎜⎜⎝

⎛=⎟⎟

⎞⎜⎜⎝

⎛0

0

22221212

*12

*121111

0

0

0

0

22

22s

s

s

s

s

s

BB

imim

imim

BB

BB

dtdi H

⎟⎟⎟⎟

⎜⎜⎜⎜

Γ−∆Γ−∆

∆Γ−∆−Γ−

=−

+

222/

22/

2imime

imeim

s

s

i

i

φ

φ

H

φs,d

O(0.1)·ΓsO(0.01)·Γd∆Γ=ΓH-ΓL

17.8 ps-10.5 ps-1∆m=mH-mL

BsBd

β2)arg( =∗tdtbVV γ∆=∗ 2)arg( tstbVV

0sB 0

sBb

s

s

bt

t

tsV ∗tbV

tsV∗tbV

(if CPV in mixing is ignored)

In SM small: 0.04

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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

vent

s

1000

800

600

400

200

0 1 2 3 4 5

Perfect reconstruction

0

Proper time (ps)E

vent

s

1000

800

600

400

200

0 1 2 3 4 5

Perfect reconstruction+ flavour tagging

0

Proper time (ps)E

vent

s

1000

800

600

400

200

0 1 2 3 4 5

Perfect reconstruction+ flavour tagging+ proper time resolution

0

Proper time (ps)

Eve

nts

1000

800

600

400

200

0 1 2 3 4 5

Perfect reconstruction+ flavour tagging+ proper time resolution+ background

0

Proper time (ps)E

vent

s

1000

800

600

400

200

0 1 2 3 4 5

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

0

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.

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∆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

LL

HH

+=

−=

evenL

oddH

Γ=Γ

Γ=Γ

ψφ/)B(B ss J→

−−= 1PCJ

−−= 1PCJ

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

Final state is mixture of CP even/odd.

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Interference between Mixing and Decay

sst

trtr

st

trtr

stt

trtr

ttrtr

ttrtr

tme

tme

ee

e

eJ

L

L

LH

H

L

φθφθ

θφθ

φθφθ

θφθ

θφθψφ

φ

φ

φ

φ

φ

sin)sin(),,(f

)sin(),,(f

sin)(),,(f

),,(f

),,(f)/B/B(

5

4

3

2

1ss

∆⋅⋅±

∆⋅⋅±

⋅−⋅+

⋅+

⋅=→Γ

Γ−

Γ−

Γ−Γ−

Γ−

Γ−

Simultaneous determination of ∆Γ and φs

Measurement possible as tagged and untagged analysis!

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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

stat

stat

=Γ∆Γ

−=

σφσ s

Constraints on new physics

W New Physics

SMssss mihm ∆+=∆ ))2exp(1( σ

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Measurement of γ with B→DK decays

γiubub eVV −= ||

cbV

comf

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

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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]

Asy

m (

Ds +

K− )

−0.5

−0.25

0

0.25

0.5

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

s

su

cbs

0sB

+K−sD

s

sc

ubs

0sB −K

+sD

Interference between direct decayand decay after oscillation

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LHCb Measurement of CKM Angle γ

γ from B→DK at LHCb (10 fb–1)

Two possible scenarios

γloops (2006)

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CKM Metrology and LHCb

%7.4/)(%17/)(

==

ηησρρσ

Summer 2006

ρ-1 -0.5 0 0.5 1

η

-1

-0.5

0

0.5

β

α

sm∆dm∆ dm∆

KεcbVubV

ρ-1 -0.5 0 0.5 1

η

-1

-0.5

0

0.5

1

%7.1/)(%5.3/)(

=ηησ=ρρσ

LHCb at L=10fb-1

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Rare B Decays Bs,d→µµ

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

W

Wb

s µ +

tµ−

ν

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

BR

(x10

–9)

1

2

3

4

5

6

7

89

10

0 1 2 3 4 5 6 7 8 9 10

LHCb Mass resolution ∆mµµ≈18 MeV

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b s

d

0B 0∗KW

Z/γµ

µ

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+

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

b s

d

0B 0∗KW

Z/γµ

µ

New Physics

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LHCb - Conclusion

b s

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.

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Numbers