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The LHCb Experiment

• The search for New Physics • The LHCb experiment• LHCb start-up and the physics

programme

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Current StatusFirst generation B factories (BaBar@PEPII and Belle@KEKB), together with CDF/D0@Tevatron, have a spectacular physics record

PDG 2000

PDG 2006

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Tests of CKM picture• Unitarity triangle from tree-level processes only

• Observe CP violation in CKM matrix is at work !

• Tree processes not affected by New Physics

• Constraint must be satisfied by any New Physics• Requires a precision measurement of

cbub V,Vb c,u

W

cbub VV

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Current tests indicate that the SM description of CP is successful and any New Physics will appear as a small correction

Tests of CKM picture• Allowed region from CP conserving

quantities

• Compared to region from CP violating quantities

• CKM phase is dominant

• New Physics is not excluded

s,dcbub mm,VV

,,,K

031.0387.0

041.0171.0

026.0675.02sin039.0764.02sin

UT sides

Measurement (bccs)2.3

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New Physics• SM cannot be ultimate theory

– low-energy effective theory of a more fundamental theory at a higher energy scale (TeV range)

– Hierarchy problem: New Physics required to cancel radiative corrections to the Higgs mass but leave the SM EW predictions unaffected

• How can New Physics be discovered and studied ? – NP models introduce new particles which could

be produced and discovered as real particles at the LHCappear as virtual particles in loop processes observable deviations from the SM expectations in flavour physics and CP

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• NP needs to have a flavour structure to provide the suppression mechanism for FCNC processes already observed.

• Once NP is discovered it is important to measure this flavour structure (including new phases) and to distinguish between the NP models.

• Direct and Indirect approaches are very complementary

t,c,u

t,c,u

W W

s,d

b s,d

b

0B 0B

Box diagram

New Physics

0B,K0

s

b

s,ds

s,d

ss

Penguin diagram

2Varg,2Varg

Vm2ts

SMs

2td

SMd

2ts,td

SM

??New Physics

d

m

s

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New Physics in B0 Mixing• Use a model independent parameterization of

New Physics in B0 (and K0) mixing

– includes only SM box diagrams– includes NP contributions as well

• Four independent observables

• One additional parameter for K0 mixing

0q

SMeff

0q

0q

fulleff

0qi2

BBHB

BHBeC qB

q

s,dq

SMeffHfulleffH

0SMeff

00fulleff

0 KHKImKHKImCK

,With NPallowed

NP in D0 mixing is neglected

5 NP parameters

ssdd BBBB ,C,,C 0,1C

qq BB (SM)

Reiterates need for precisionmeasurement of

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New Physics in B0 Mixing

Non-zero central value of d from difference in SM fit between angles (sin2) and sides (Vub)

CBs constrained more than CBd from CDF measurement of ms

Need to measure Bs mixing phase s

0dB

SM

0sB

SM

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Search for New Physics • Measure processes very suppressed in SM

– CP in Bs mixing ( in SM)• BsJ/

– Radiative and very rare B decays • BdK*, Bs, Bd K*, Bd,s

– Rare D decays and D0 mixing– Lepton flavour violating decays

• Precision measurements of CKM elements– Bs oscillations– Compare pure tree level processes with processes sensitive to NP

• Sin2BdJ/Ks vs BdKs • BDK vs B/KK

– Measure all angles and sides in many different ways. Any inconsistency will be evidence for NP

– Requires clean and improved theory predictions

2s 2

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The LHCb Experiment• LHCb is dedicated to the Search for New Physics in

CP violation and Rare B decays

• LHCb Collaboration: 14 countries, 47 institutions, ~600 people

Interactionpoint

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LHCInteraction point 8 Final focus

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Muon Calorimeters RICH2Trackers

Magnet

RICH1VELO

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b production at the LHCIn the forward region (4.9 > >1.9):• bb cross-section large (~230 b)

• Luminosity ℒ=2x1032 cm-2s-1

1012 B hadrons in 107 sec• All species of B hadrons produced

(B, Bd, Bs, Bc, b-baryons)

• B’s have large momentum <pB>acc ~ 80 GeV/c Mean flight path of B’s ~7mm.

• bb production correlated and sharply peaked forward-backward. bb

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Trigger• Trigger crucial to the successful operation of LHCb

– B fraction is only ~1% of inelastic cross-section.– Br’s of interesting B decays <10-4

– Properties of minimum bias similar to B’s

• First Level Trigger (L0) – Hardware (custom boards, 4s latency)– Largest ET hadron, e() and (di-)– Pile-up system (not for trigger)– Reduces 10 MHz inelastic rate to 1MHz

L0 e

ffici

ency

(%)

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Trigger• High Level Triggers

– Software trigger run on CPU farm (1800 nodes)– Access to all detector data – Use more tracking information to re-confirm L0 decision – Full event reconstruction; inclusive and exclusive

selections tuned to specific final states– Output rate 2 kHz, 35 kB per event

Output rate Trigger Type Physics Use200 Hz Exclusive B candidates Specific final

states600 Hz High Mass di-muons J/, bJ/X300 Hz D* Candidates Charm,

calibrations900 Hz Inclusive b (e.g. b) B data miningTotal 2000 Hz

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Flavour Tagging

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VELO• 21 VELO stations (r and silicon

sensors)• Placed in a secondary vacuum vessel• 3cm separation, 8mm from beam • Separated by a 300 m of Al RF foil • Detector halves retractable for

injection

pile-up veto

RF foil

interaction point

Silicon sensors

~1 m

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VELO

RF foil

Vacuum vessel

Beam’s eye view

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VELO• 42 VELO modules

– r and layer – n+n type– 2048 strips/sensor– Strip pitch 40 m to 100 m

VELO module production

• Status– 70% modules produced – One half VELO complete

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Tracking

Trigger TrackerSilicon stripspT information for trigger

Outer TrackerStraw tubes

Inner TrackerSilicon strips2% of area20% of tracks

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Tracking

Trigger Tracker

Outer Tracker

Inner Tracker

Status: – Module production ~finished (IT end Feb)– Installation: OT finish Mar 07 IT/TT Mar-Jul 07

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Magnet

B/B = 0.03%B/B = 0.03%

Peak field on axis: 1.1 TField integral: 4 Tm (over 10 m)

By /T

z /cm

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Tracking performance• Track fit: bi-directional Kalman fit• Tracking efficiency >95% • Ghost rate <7% p > 12 GeV

p distribution for B tracks

Momentum Resolution

1/pt distribution for B tracks

Impact Parameter Resolution

VELOMagnet

T StationsTT

Event display

• Vertex resolution– ~10 m in x,y; 50 m in z

• Proper time resolution ~ 40 fs• B Mass resolution ~ 15 MeV

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RICH Detectors• Particle ID: p~1-100 GeV provided by 2 RICH

detectors

RICH1

RICH2

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• Status: RICH2 installed RICH1 finish installation Aug 2007

RICH Detectors• 3 radiators: RICH1 Aerogel (2-10 GeV), C4F10 (10-

60 GeV) RICH2 CF4 (16-100 GeV)

Aerogel22 tiles

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RICH Photodetectors• 484 Hybrid Photo Detectors (HPD’s)

80mm

120m

m

<QE> @ 270 nm (per batch)

25

26

27

28

29

30

31

32

33

34

35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16batch no.

aver

age

QE [%

] .

<QE> per batch

running <QE> (batch 1-16)

Quantum Efficiency

contract spec.typical 23.3 %

HPD production expected to be completed March 2007

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RICH Performance Full MC simulation using “global” fit to Cherenkov rings

High Level Trigger D* stream D*→D0(K) RICH independent E

ffici

ency

D* MC Truth

/K selected from D* sample(no MC truth)

RICH1 RICH2

Effi

cien

cy(%

)

p (GeV)

K or p

K K or p

Averages:K→ K,p eff: 83.1± 0.1%→misID

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CalorimetersSPD/PS: Pb/Scint., 2.5 X0

ECAL: Pb-Scint. Shashlik, 25 X0

HCAL: Fe/Scint. tiles, 5.6 0

%1E%10

EE

%10E%80

EE

ECAL

HCAL

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reconstructionExample: Time dependent Dalitz plot analysis of B0

14k signal events in 2 fb-1

Resolved π0

2 isolated photons

~15 MeV~10 MeV

Merged π0

Single ECAL cluster

MergedResolved

Transverse energy (GeV)

Efficiency = 53% for B0

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Muons• 1368 MWPCs (M2-M5, outer M1

region)• 24 3-GEMs (inner M1 region)

3-GEM

MWPC

M5

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Muons• Status: production finished;

installation and commissioning in progress

• ODE electronics under commissioning

Fixing chambers on the inner edge of wall requires expert climbers

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Muon ID• Muons at L0

trigger (pt > 1 GeV): AND of hits in the 5 stations

Bsμμ

μ

Tracking system

Muon system

Distance of closest hit (pad unit)

DC06 performance: ε(muons) = 90.5 0.1 %Total misID = 1.78 0.1 %misID for hadrons = 0.52 0.01 %Fraction of decays in flight = 72%misID for decays in flight = 43.1 0.2 %

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LHCb Status• LHCb is confident that the experiment will be

ready for data-taking in March 2008

• All major and heavy structures are installed• OT, RICH2, ECAL and HCAL are very close to be

ready for a “global” commissioning • RICH1, VELO, IT and TT needs still some (but

short) installation work.• Installation of Muon system and PS/SPD cabling

will still continue for a few months

• LHCb will take physics data in 2008 with a complete detector

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LHCb startup programme

• 2008: early phase– Complete commissioning of detector and trigger at s=14 TeV– Calibrate momentum, energy and particle ID– Start first physics data taking, assume ~ 0.5 fb–1

– Establish physics analyses, understand performance– Look asap for New Physics with measurements competitive at low

lumi

• 2009–20xx: stable running– Stable running, assume ~ 2 fb–1/year– Develop full physics program– Exploit statistics, work on systematics

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Very Rare B Decays: Bs +–

• Very rare loop decay, sensitive to New Physics:

– BR ~3.510–9 in SM, can be strongly enhanced in SUSY

– Current 90% CL limit from CDF+D0 with 1 fb–1 is ~20 times SM

W

W

b

s

t

?

?

MSSM • Main issue is background

rejection– With limited MC statistics,

indication that main background is b, b

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Very Rare B Decays: Bs +–

0.05 fb–1 overtake CDF+D00.5 fb–1 exclude BR values down to SM

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

Integrated luminosity (fb–1)Limit at 90% C.L. (only bkg is observed)

Integrated Luminosity (fb-1)

Uncertainty in bkg prediction

Expected final CDF+D0 Limit

BR

(x10

–9)

SM prediction

LHCb Sensitivity(signal+bkg is observed)

Integrated Luminosity (fb-1)

5

3

SM prediction

BR

(x10

–9)

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Rare B Decays: B0 K*0

• Suppressed by loop decay, BR ~1.210–6

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

• Sensitivity

– 7.7k signal events/2fb–1, Bbb/S = 0.4 ± 0.1

– After 2 fb–1, zero of AFB(s) to ±0.52 GeV2

determine ratio of Wilson coefficients

C7eff/C9

eff with 13% stat error (SM)

s = (m)2 [GeV2]

AFB(s), theory

+

–

AFB(s), fast MC, 2 fb–1

s = (m)2 [GeV2]

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• Bs mixing phase, s is very small in SM sSM = –

0.037 ± 0.002 (UT fits) – Could be much larger if New Physics in the box

•Golden bccs mode is Bs J/:– Angular analysis needed to separate CP-even

and CP-odd contributions– Expect ~130k Bs J/() signal events/2fb–1

(before tagging), S/Bbb= 8

•Add pure CP modes (J/(’), c, DsDs) – No angular analysis, smaller statistics

•Sensitivity:

Bs Mixing Phase s with bccs

[LHCb-2006-047]

stat(s) = 0.044 with 0.5 fb–1

? t,c,u

t,c,u

W W

s,d

b s,d

b

0B 0B

Channels s [rad]0.1420.1330.1090.108

Combined (pure CP eigenstates)

0.060

0.023Combined (all CP eigenstates)

0.022

0s /JB

sss DDB /JBs

csB

/JBs

Statistical sensitivities on s for 2 fb–1

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Constraints on New Physics in Bs mixing from s measurement

• New Physics in Bs mixing amplitude parametrized with and

• Can exclude already significant region of allowed phase space with the very first data (2008)

? t,c,u

t,c,u

W W

s,d

b s,d

b

0B 0B

NPsi2

SMs

NPs

0s

SMeff

0s

0s

fulleff

0s

eAA1

BHB

BHB

SMs

NPs AA NP

S

In April 2006, including CDF’s first measurementof ms

>90% CL

>32% CL>5% CL

After LHCb measurement of s with (s)= ±0.1 (~ 0.2 fb–1)

courtesy Z.Ligeti

NPS

SMs

NPs AA

from hep-ph/0604112

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bsss hadronic penguin decaysCurrently explored at B factories with time-

dependent analyses oftagged decays to CP eigenstates such as B0 KS,

etc.– Expect same result (i.e. sin2) as

b ccs tree decays like B0 J/KS if only SM Decay phase = 0

Decay phase ~ 0 in SMDecay phase ≠ 0 if NP

total phase = (mixing phase 2) + (decay phase)

b

c

s

c

W –VcbVcs

*

b

t

s

s

s

W –Vtb Vts*

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bsss hadronic penguin decays• Also accessible at LHCb

• Best channel is Bs

– CP violation < 1% in SM (Vts enters both in mixing and decay amplitudes)

– significant CP-violating phase can only be due to New Physics– Angular analysis required– 4k signal events per 2 fb–1 (if BR=1.410–5), 0.4 < B/S < 2.1

@90%CL

• After 10 fb–1

– ± 0.042 from Bs

– ± 0.14 from B0 KS (4k signal events, B/S < 2.4 @ 90% CL)

0sB

b

s ssss? NP

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CKM angleMany ways to measure at LHCb using various methods:•Tree-level processes

– Bs DsK ~14o per 2fb-1

– Bd D(*)

– B, Bd D(*)K(*), with D0 decaying to:2 bodies: K, KK, best modes offer 5-10o 3 bodies: KS KS KK, KS Keach per 2 fb-1

4 bodies: KKK

•Penguin processes– Bd

+–Bs K+K–

– U-spin approach ~ 4o per 2 fb-1

(7-10o with 20% U-spin violation) invariant mass

With PID With PID

KK invariant mass

Expect with 10 fb-1

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CKM angle

from BDK at LHCb (10 fb–1)

Two possible scenarios

loops (2006)

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Effect of LHCb on UT

%7.4/)(%17/)(

Summer 2006

%7.1/)(%5.3/)(

LHCb at L=10fb-1

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B mode (tree)

D mode Method (), 2 fb–1

B+ DK+ K + KK/ + K3

ADS+GLW 5º–15º

B+ D*K+ K ADS+GLW Under study

B+ DK+ KS Dalitz 8ºB+ DK+ KK 4-body

“Dalitz”15º

B+ DK+ K 4-body “Dalitz”

Under study

B0 DK*0 K + KK + ADS+GLW 7º–10ºB0 DK*0 KS Dalitz Under

studyBs DsK KK tagged, A(t) 13º

B modes (penguin) Method Assumption (), 2 fb–1

B0 +–Bs K+K–

tagged, A(t)Fleischer

Perfect U-spin symmetryUp to ~20% violation

4º7º–10º

Sensitivities to CKM angle

Signal only

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from B± DK±

• “ADS+GLW” strategy:– Measure the relative rates of B– DK– and B+ DK+ decays with neutral

D’s observed in final states such as: K–+ and K+–, K–+–+ and K+–+–, K+K–

– These depend on:• Relative magnitude, weak phase and strong phase between B– D0K– and B–

D0K– • Relative magnitudes (known) and strong phases between D0 K–+ and D0

K–+,and between D0 K–+–+ and D0 K–+–+

– Can solve for all unknowns, including the weak phase :

u

b

u

s

c

u

B–

D 0

K–

colour-suppressed

u

u

b

c

u

s

B–

D0

K–

colour-allowedWeak phase difference = Magnitude ratio = rB ~ 0.08

Decay 2 fb–1 yield

Bbb/S

B– (K–+)D K– 28k ~0.6

B+ (K+–)D K+ 28k ~0.6

B– (K+–)D K– 180 4.3B+ (K–+)D K+ 530 1.5

() = 5–15 with 2 fb–1

(depending on the strong phases)

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CKM 2008 (pre-LHCb)Improvements due to• Bd, B sector: B-factories (Babar/Belle)

– Assume ℒ = 2 ab-1 at the (4S) () 6.5°, () 6.5°, (sin2) 0.017

• Bs sector: Tevatron (CDF/D0)– Assume (2x) 6 fb-1 (s) 0.2, (s/s) 0.04, (ms) 0.5%

• Lattice QCD prospects%3.3/)(%4.7/)(

Now Pre-LHCb

6 TFlop year

201040 TFlop

year

20141 PFlop

year11% 5% 4% 2%13% 5% 4% 2%5% 3% 2.5% 1.5%

Vub-excl.* 11% 6% 5% 3%Vcb-excl.* 4% 2% 1.5% 1%

KB̂

BsBs B̂f Courtesy V.Vagnoni

CKM 2006, Nagoya

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LHCb Sensitivities with 2fb-1