LHCb - The Future of Heavy Flavour Experiments Franz Muheim University of Edinburgh Beauty and Charm...

LHCb - The Future of LHCb - The Future of Heavy Flavour ExperimentsHeavy Flavour Experiments

LHCb - The Future of LHCb - The Future of Heavy Flavour ExperimentsHeavy Flavour Experiments

Franz MuheimUniversity of Edinburgh

Beauty and Charm Decays: A Window on New Physics

In honor of Sheldon Stone's 60th birthday

May 20-21, 2006, Syracuse, NY

Syracuse, 20 May 2006 F. Muheim 2

OutlineOutline Physics Motivation

– UT triangles– NP sensitivity

LHCb experiment at LHC– B physics at Hadron Colliders– LHCb detector– Vertexing– RICH– Trigger– Status

Physics Programme– Bs oscillations and CP violation– CKM angle gamma– Rare decays– Sensitivities

LHCb Upgrade– Luminosity, Detector– Physics motivation

Conclusions


Standard Model rho-eta fitsStandard Model rho-eta fits

New Status including CDF Bs oscillation measurement - ms

Standard Model is very successful 1.7 discrepancy between Sin2 and Vub inclusive


b

B0

t

s

s

W

ss

s

s

Motivation for Flavour PhysicsMotivation for Flavour Physics

Standard Model

W

W

b

Bs0

s

b

s

B s

0

t

t

–Bs-Bs oscillations

Supersymmetry New Physics

?

Bs penguin decay

Standard Model (SM) is a low-energy effective theory– Based on more fundamental theory manifest at a higher energy scale– Expect new particles and/or symmetries likely in the TeV region

How to probe New Physics (NP) ? – Discovery of new particles at energy frontier (LHC)– NP appears as virtual particles in loop processes leading to observable

deviations from SM expectations in flavour physics and CP violation ( )

?


P. Ball, Flavour in the LHC eraworkshop


B-Physics at the LHC vs B-B-Physics at the LHC vs B-Factories Factories

ee (4S) BBPEPII, KEKB

ppbbX (√s = 14 TeV, tbunch=25

ns)LHC - LHCb, ATLAS/CMS

Production bb 1 nb ~500 b Typical bb rate 10 Hz 100–1000 kHz

bb purity ~1/4 bb/inel = 0.6%Trigger is a major issue !

Pileup 0 0.5–5

b-hadron types B+B– (50%)B0B0 (50%)

B+ (40%), B0 (40%), Bs (10%)Bc (< 0.1%), b-baryons (10%)

b-hadron boost Small Large (decay vertexes well separated)

Production vertex Not reconstructed Reconstructed (many tracks)

Neutral B mixing

Coherent B0B0 pair mixing

Incoherent B0 and Bs mixing(extra flavour-tagging dilution) Event

structure BB pair alone Many particles not associated with the two b hadrons


Large Hadron Collider --- LHCLarge Hadron Collider --- LHC

with a B-physics programme LHCb

dedicated for precision measurements of CP violation and rare decays in B hadrons

ATLAS/CMS optimized for high-pT discovery physics competitive for channels with leptons

Mont Blanc

Lake GenevaChâteau Farges

ATLAS


LHC interaction points– 40 MHz pp interaction rate, bunch crossing every 25 ns

– cross section inel = 80 mb Luminosity

– Starting luminosity L = to cms

– Design luminosity L = cms

ATLAS/CMS – run at highest available luminosity– expect L<21033 cm–2s–1

n < 5 for first 3 years– n = 25 at L=1034 cm–2s–1

LHCb– Luminosity tuneable by adjusting beam focus– run at L ~ 21032 cm–2s–1

(max. 51032 cm–2s–1)– little pile-up (n = 0.5)– less radiation damage – Luminosity will be available for 1st physics run

2 fb–1 / year10 fb–1 in 5 years1 year = 107 s

10 fb–1 / year at low L30 fb–1 total at low L

Luminosities at LHCLuminosities at LHC

n = # of pp interactions/crossingn = # of pp interactions/crossing

LH

Cb

n=0

n=1

AT

LA

S/C

MS


VELO

collision point

~1 cm

B

Dipolemagnet

Crucial for B physics:• optimised geometry and choice of luminosity• Trigger efficient in hadronic & leptonic modes • excellent tracking and Vertexing (m, )• excellent particle ID - RICH

LHCb ExperimentLHCb Experiment


LHCb TriggerLHCb Trigger

Level-0 (Hardware)High pT - , , e, , hadron + pileup synchronized (40 MHz), 4 s latency

10 MHz (visible bunch crossings)

1 MHz (full detector readout)

≤ 2 kHz (storage media)

Output rate

Event type Physics

200 Hz Exclusive B candidates

Specific B final states

600 Hz High mass di-muons

J/, bJ/X (unbiased)

300 Hz D* candidates CharmCalibrations

900 Hz Inclusive b (e.g. b)

B (data mining)

HLT (PC farm ~2000 CPUs)Confirm Level-0Associate tracks with minimum impact parameter and pT , e, h, alleysInclusive/exclusive selections

L0 efficiency


VELO – Vertex Locator – laid out as a series of R and Φ silicon detector stations– 0.8 cm to the beam line, situated inside beam vacuum

vessel

Detached Vertex Trigger– Allows to select B-meson vertices

High efficiency for all decay modes– Gives excellent proper time resolution

Vital for resolving Bs oscillations

VELO – Silicon Vertex DetectorVELO – Silicon Vertex Detector

BsDs proper time resolution

t ~ 40 fs

VELO – Silicon Vertex DetectorVELO – Silicon Vertex Detector


Charged particle Identification– LHCb has 2 RICH detectors with 3 radiators– Allows clean separation of different Bh+h modes– Not possible elsewhere at hadron colliders.

CDF data

Bd signalBd

signal

BsKK signal

Tevatron

Ring Imaging Cherenkov Ring Imaging Cherenkov DetectorsDetectors


Installation StatusInstallation Status

RICH2Muon system

CalorimeterECAL, HCAL

DipoleMagnet

RICH1


RICH DetectorsRICH Detectors

RICH 2 RICH 1

RICH 2

RICH 1

HPDs


LHC StatusLHC Status

LHC start– July 2007 – 1st beam in late 2007– Physics operation in 2008

Cryogenic services

line

LHC dipole

LHC tunnel


LHCb Physics ProgrammeLHCb Physics Programme

~Vub* ~Vtd

~Vcb

~Vub* ~Vtd

~Vts

S0s

s

DB

m

)('0s ΨJ,ΦΨJB

0S

0d KΨJB

πππB 00d

KDB s0s

000d

0d

KDBKDB

KKBandB 0s

0d

and

B production , Bc , b-baryon physics Charm decays Tau Lepton flavour violation

Rare decays - very sensitive to NP– Radiative penguin e.g. Bd K* , Bs Φ

– Electroweak penguin e.g. Bd K*0

– Gluonic penguin e.g. Bs ΦΦ, Bd ΦKs

– Rare box diagram e.g. Bs


BBss Oscillations Oscillations Precision measurement of ms

– is one of the first goals of LHCb physics programme– Expect 80k Bs Ds

+ events per year (2 fb–1) with t ~ 40 fs– S/B ~ 3 derived from 107 fully simulated inclusive bb events

5 observation for ms < 68 ps–1 with 1 year/ 2 fb–1 ms < 40 ps–1 in ~1 month /0.25fb–1Distribution of unmixed

sample after 1 year (2 fb–1) assuming ms = 20 ps-1

CDF measurement


CP Violation in Bs mesons– Interference between Bs mixing and decay– Bs J/ is the Bs counterpart of B0J/ KS

– Bs weak mixing phase s is very small in SM

s = –arg(Vts2) = -2 ≈ –22 ≈ –0.04

sensitive probe for New Physics– J/ final state contains two vectors

Angular analysis needed to separate CP-even and CP-odd amplitudesFit for sin s, s and CP-odd fraction (using external ms value)

s Sensitivity – at ms = 20 ps–1

– Expect 125k Bs J/ signal events per 2 fb–1 (1 year) with S/Bbb > 3– Expected precision (sin s) ~ 0.031

– Small improvement s by adding pure CP modes, e.g. J/, J/’, c (sin s) ~ 0.013 for 10 fb-1 (first 5 years)

~3 evidence for s ≈ –0.04 (SM) Bs Lifetime difference s/s

– Expected sensitivity (s/s) ~ 0.011 using Bs J/ events

– Similar sensitivity in untagged semileptonic Bs Ds-l+ eventsExpect 700k events per 2 fb–1

ss and and ss from B from BssJ/J/


from Bfrom Bss D DssKK

Two tree decays (bc and bu) of O(3)– Interference via Bs mixing

– Weak phase of Vub = e-i for bu diagram

– Theoretically clean

– Insensitive to New Physics Large background ~20

– from Cabibbo allowed decay

– need RICH, residual background ~10% Expect 5.4 k events in 1 year

– S/Bbb > 1 at 90% CL

ss DB0

With RICH

Vub

Vcb


Fit the 4 tagged time-dependent rates:– Extract + s, strong phase

difference , amplitude ratio

– Bs Ds events used in fit

to constrain other parameters (mistag rate, ms, s …)

Sensitivity for – () ~ 14 in 2 fb-1 or 1 year

for ms = 20 ps–1

– Precision statistically limited– 8-fold ambiguity can

be resolved ( 2-fold) if s large enough, or using B0 D together with U-spin symmetry (Fleischer)

Both DsK asymmetries (after 5 years, ms = 20 ps–1)

Ds–K+: info on + ( + s)

Ds+K–: info on – ( + s)

from Bfrom Bss D DssKK


()

dBs KK (95% CL)

B

(95% CL)

from Bfrom B and B and BssKKKK

Measure time-dependent CP asymmetry

– Adir and Amix depend onCKM angle , mixing phases d and s, and ratio of penguin-to-tree amplitudes (d ei)

U-spin symmetry (d s)– Assume d=dKK and =KK

– 4 measurements and 3 unknowns (, d and )using d from Bd-> J/KS and s from Bs-> J/

– Extract angle LHCb sensitivities

– Event yields - 1 year data set, 2fb-1

26k B and 37k BsKK

– Precision - () ~ 5

)sin()cos()( tmAtmAtA mixdirCP

R. Fleischer, PLB 459 (1999) 306 Bd/s

Bd/s

/K

/K

/K

/K

– Sensitive to New Physics in penguins– Uncertainty from U-spin assumption


Dunietz variant of Gronau-London-Wyler method (GLW)– Two colour-suppressed diagrams with

|A2|/|A1| ~ 0.4 interfering via D0 mixing

Measure 6 decay rates (self-tagged + time-integrated):– LHCb expectations for 2 fb–1 (=65, =0)

from Bfrom B00 D D00KK**00

Mode (+ cc) Yield S/Bbb (90%CL)

B0 D0 (K) K*0 3.4k > 2

B0 D0 (K) K*0 0.5k > 0.3

B0 D0CP (KK) K*0 0.6k > 0.3

Sensitivity () ~ 8 in 2 fb-1

A1 = A(B0 D0K*0): bc transition, phase 0

A2 = A(B0 D0K*0): bu transition, phase +

A3 = 2 A(B0 DCPK*0) = A1+A2, because DCP=(D0+D0)/2

d

b

d

s

u

c

B0

D 0

K*0

D0

d

b

d

s

c

u

B0

K*0


Two interfering tree processes in charged B decay

Decays common to D0 and D0

– Interference effects depend on 3 parameters – b→u , b→c interferencerB – the amplitude ratio betweend two diagrams (0.1 – 0.2)δB – a CP conserving strong phase difference

– i) Cabbibo favoured self-conjugate D decays e.g. D0 Ks, KsKK, KKππ Dalitz

analysisSensitivity () ~ 5 in 2 fb-1

– ii) Cabbibo favoured/doubly Cabbibo suppressed D decayse.g. D0 K, K ADS method

u

bB 0D

u

c

K

u

s

u

b

B

K

u

s

0Dc

u

from Bfrom B± ± DK DK±±

Colour allowed Colour suppressed


from Bfrom B±± DK DK±± ADS method ADS method based on Atwood-Dunietz-Soni [Phys. Rev. Lett. 78, 3257

(1997)] Measure relative rates of B– DK– and B+ DK

– Two interfering tree B-diagrams, one colour-suppressed (rB ~0.15)

– Two interfering tree D-diagrams, one Doubly Cabibbo-suppressed (rD

K ~0.06)

– Self-tagging – advantageous for LHCb– No proper time measurement required

– 3 observables, 4 rates, but only 3 ratios 5 parameters (D

KrB, rDKrD

K known Sensitivity

() ~ 5 in 2 fb-1

30k

1k

30k

1k

Events per 2 fb-1


BBs,ds,d→μ→μ++μμ- - at LHCat LHC

Very rare FCNC decay – in SM low uncertainty

– BR(Bs→μ+μ-) = (3.5 ± 0.9) 10–9

– BR(Bd→μ+μ-) = (1.0 ± 0.5) 10–10

Very sensitive to New Physics:

– Large enhancement in Higgs mediated SUSY processes

– Decay is one of the most sensitive SUSY probes– Complementary to direct SUSY searches at LHC

s, s,


BBs,ds,d→μ→μ++μμ- - at LHCat LHC

< 1

< 20

< 100

b, bbackground

48 MeV/c2

75 MeV/c2

18 MeV/c2

Mass resolution

10 fb–1

10 fb–1

2 fb–1

1 year

< 750017LHCb

7

7

Bs + – signal (SM)

Inclusive bb background

CMS (1999)

ATLAS

New Physics Sensitivity– For BR at SM value

M0, M½ > 1500 GeV– Competitive with direct searches

Current Results – dominated by Tevatron– New limit from CDF&D0 at FPCP 2006

BR(Bs→μ+μ-) < 8 10-8 @ 90% CL

LHC expectations– Will observe decay

down to SM level– LHCb will face competition from ATLAS/CMS

Excluded!

M0 [

GeV

]


Rare FCNC decay– Inclusive branching fraction

well known in SM– BR(B→Xsμ+μ-) = (1.59 ± 0.11) 10–6

– Exclusive decays better at LHCb

– Di-lepton invariant mass s– BR - well controlled in region

outside resonances -J/ and ’

Forward-backward asymmetry AFB(s)– Asymmetry angle - B flight direction

wrt + direction in +- rest-frame

Sensitive probe of New Physics– Deviations from SM by SUSY,

graviton exchanges, extra dimensions

– AFB(s0) = 0 - predicted at LO without hadronic uncertainties

– Zero point s0 and integral at high s sensitive to Wilson coefficients

BBdd→→K*K*00μμ++μμ--

BR(s) for B0AFB(s) for B0


AAFBFB in B in Bdd→→K*K*00μμ++μμ--

Expected Signal Yield– 4400 events in 1 year/2fb-1

Background/Signal– Full simulation, 11 M b-bbar

MC– B/S ~ 0.2 – 2.6

AFB zero point sensitivity

– s0 = 4.0±1.2 GeV2 in 1 year

– s0 = 4.0±0.5 GeV2 in 5 years

– 13% error on C7eff/C9

eff

AFB after 1 year AFB after 5 years


Sensitivity SummarySensitivity Summary Based on 10 fb-1

Bs mesons– Precision measurements– Oscillations

(ms,) < 0.01 ps-1 – CP violation

(s) ~ 0.013– Lifetime difference stat(s/s) < 0.01

CKM angle – Reduce error on by factor 5

( ) ~ 30 in best mode– Bs→Ds

+K-

– B0→D0K*0

– B+→D0K+ ADS, Dalitz Rare Decays

– AFB in Bd→K*μ+μ-

– Bs→μ+μ-

– B→K*, Bs→ Charm Physics

– CP violation– D0 oscillations – Under study

Lepton Flavour Violation– B and D, e.g. B,D→μe, μ – Tau decays, e.g. + →μ+μ-μ+

Sensitivity Comparison ~2013LHCb 10 fb-1 vs Super-B factory 5 ab-1

LHCb and B-factories are complementary

Bs

No IP

Neutrals,

Com

mon


LHCb Upgrade LHCb Upgrade LHCb Operation

– Increase luminosity adjabatically to ℒ ~ 5 x1032 cm-2s-1

– LHCb detector can cope, could/should be done anyway Upgrade LHCb to run at 10 times nominal Luminosity

– ℒ ~ 2 x1033 cm-2s-1

– Multiple interactions per beam crossing increases to n ~ 4– Does not require LHC luminosity upgrade (SLHC)

Detector Considerations – to operate LHCb above 5 x1032 cm-2s-1

– Vertex detector (VELO) requires replacing after 6 to 8 fb-1

– Existing Front-End electronics limits L0 Trigger output to 1.1 MHz – Muon (Hadron) L0 trigger does (does not) scale with luminosity

LHCb Upgrade Ideas – Replace VELO with a radiation tolerant vertex detector

Strips and/or pixels, remove RF foil (closer to beam 5mm)– Improve trigger by adding first level displaced trigger

Implementation in FPGAs– Replace inner most region of RICH photo detectors– Increase/decrease size of Inner/Outer Tracker – Replace inner most region of ECAL with crystal calorimeter– Replace all Front-End electronics with 40 MHz read-out– Initial studies to operate LHCb at 2 x1033 cm-2s-1 after 2011 have started


Physics Case for LHCb UpgradePhysics Case for LHCb UpgradeSensitivity Comparison ~2020

LHCb 100 fb-1 vs Super-B factory 50 ab-1

LHCb and Super-B factory are complementary

Bs

No IP

Neutrals,

Com

mon

100 fb-1 data sample– run 5 yrs at ℒ ~ 2 x1033 cm-2s-1

– Estimates scaled with luminosity– trigger improvements not included

CP Violation in Bs Mesons – SM prediction s = -0.040 s precision statistically limited – to 3 evidence with 10 fb-1

– ~10 measuement with 100 fb-1

b->s transitions– Very sensitive to New Physics– 2.6 discrepancy in average of

S(b->s) = sind -sin2 Best b->s penguin mode for LHCb

– Bs→ – Expected yield 1.2 k events per 2

fb-1– If you measure S() ≠ s (SM)

clear signal for New Physics S() precision statistically limited– With 100 fb-1 estimate

S() = 0.040– Similar precision for Bd→ KS


ConclusionsConclusions Heavy Flavour Physics in 2006

– The CKM mechanism is very successful in describing the data – New Physics will manifest itself as corrections to the SM– Require precision measurements to over-constrain UT

triangles LHCb experiment

– Will exploit the large rates of B-mesons at the LHC– Construction of LHCb detector and accelerator well underway – Will be ready for physics in 2007

LHCb physics programme– Exploit the Bs system

Precision measurements of Bs mass and lifetime difference Measure CP violation in Bs mesons

– Reduce error on CKM angle by a factor 5 – Probe New Physics in rare B meson decays

with electroweak, radiative and hadronic penguin modes– Hopefully find the unexpected


Backup SlidesBackup Slides


Table from

G. Isidori

Heavy Quark Flavour Structure Heavy Quark Flavour Structure


LHC ExperimentsLHC ExperimentsLHCb

ATLASCMS

with a B-physics programme LHCb

dedicated for precision measurements of CP violation and rare decays in B hadronsmay be the only B-physics experiment running after the B factories unless new projects (Super-B, LHCb upgrade) are approved

ATLAS/CMS optimized for high-pT discovery physics competitive for channels with leptons


b Production at the LHCb Production at the LHC

Momentum pB and decay length L – larger in forward region– <pB> ~ 100 GeV/c – Mean B meson flight path <L> ~10 mm

230b

100bB

b-b angular correlation

PT vs pseudo-rapidity


Flavour TaggingFlavour Tagging

LHCb– Most powerful tags - opposite kaon, bcs, (Bd) and same side kaon (Bs)

– Combined D2 ~ 7.5% (Bs) or ~ 4.5% (B0)

– Neural network approach leads to ~9% and 5% Comparison

– CDF/D0 achieved ~1.5%/2.5% (Bd) and ~4% (Bs )

– B factories achieved ~ 30%

D2 = (1–2w)2 in %

Tag Bd Bs

Muon 1.2 1.4

Electron 0.6 0.6

Kaon 2.1 2.4

Jet/vertex 0.7 0.8

Same side 0.7() 3.1 (K)

Total 4.4 7.5


sin(2sin(2) with B) with B00J/J/ K KSS

CPV in interference of mixing and decay– Measure time dependent CP asymmetry

1st Analysis for LHCb– Test proper time reconstruction– Test tagging performance

• Using control channelse.g B+ J/K+ and B0 J/K*0

• Dependent on how event is triggered - on signal or on rest of the event

Sensitivity – Expect ~240k signal events/year

stat(sin(2)) ~ 0.02– Can also push further the search for

direct CP violation in term cos(mdt)


AngleAngle from B from Bdd 00––++ decays decays–Dalitz plot analysis (Quinn Snyder method)

•Bd0–+ selection based on multivariate analysis•Use resolved and merged 0

•Expect 14k events per year, B(bb)/S < 1

– Toy MC study:• 11-parameter likelihood fits

performed in time-dependent Dalitz space

• B/S = 0.8 (flat and resonant bkg)

00

–+

+–

m2(0+)

m2 (0–

)

Combined discriminant variable1 year () ~10°

gen=106°


Additional ObservablesAdditional Observables

Angular correlations– 3 angles l, K* and

– 4-dim decay amplitude

Transversity amplitudes – A┴,A║,A0 for full description

– Sensitive to left and right-handed currents

– Expect large effects for New Physics

Kruger&Matias hep-ph/0502060


from Bfrom B±± DK DK±± ADS method ADS method based on Atwood-Dunietz-Soni [Phys. Rev. Lett. 78, 3257

(1997)] Measure relative rates of B– DK– and B+ DK

– Two interfering tree B-diagrams, one colour-suppressed (rB ~0.15)– Two interfering tree D-diagrams, one Doubly Cabibbo-suppressed

(rDK ~0.06)

– Self-tagging, i.e. good for LHCb– No proper time measurement required

– Event yields 30k, 1k, 30k, 1k in 2 fb-1

– 3 observables, 4 rates, but only 3 ratios 5 parameters (D

KrB, rDKrD

K known Sensitivity

() ~ 5 in 2 fb-1


B → XB → Xss μ μ++μμ--

FCNC diagrams– Well known SM BR

BR(B→Xsμ+μ-) = (1.59 ± 0.11) 10–6

Observables – Branching fraction BR– Forward-backward asymmetry AFB

Sensitive to New Physics – Deviations from SM by SUSY,

graviton exchanges, extra dimensions ... At hadron colliders

– Inclusive decays are difficult to access preferred by theory– Exclusive decays affected

by hadronic uncertainties– Channels under study

• Bd→K*0μ+μ-

• B+→K+μ+μ-

• Λb→Λμ+μ-

• Bs→μ+μ-


LHCb Sensitivities with 2 fbLHCb Sensitivities with 2 fb-1-1

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