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Vancouver, 9-12 April 2006

Flavor Physics and CP Violation Flavor Physics and CP Violation at LHCat LHC

Flavor Physics and CP Violation Flavor Physics and CP Violation at LHCat LHC

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LHC dipole

LHC tunnel

Motivation Experimental sensitivity Expected physics performance Conclusion

Andreas Schopper (CERN)


Flavor Physics and CP Violation 2 Andreas Schopper

MotivationMotivationMotivationMotivation

New Physics models introduce new particles, dynamics and/or symmetries at a higher energy scale (expected in the TeV region) with virtual particles that appear e.g. in loop processes

B Physics measurements are complementary to direct searches and will allow to understand the nature and flavour structure of possible New Physics

B-factories (BABAR&BELLE) are extremely successful in constraining the unitary triangle within the SM and Tevatron (D0&CDF) has demonstrated its Bs physics capability!

LHC will act as a b-factory with large b-quark production rate including Bs, allowing to improve the CKM consistency test and to look for deviations from the SM rare processes

CKM fitter without CDF

UT fit with CDF



Precise determinations including processes only at tree-level, in order to disentangle possible NP contributions

Other measurements of CP phases in different channels to over-constrain the Unitarity Triangles

BsDsK, B0D0K*0, BDK, B0BsKK, …B0Ks, BsB0B0…

BsDs, … BsJBsJ(’)

B(s)0X B0K*0l+l-,

bsl+l-, Bs...

Search for effects of NP appearing in suppressed and rare exclusive and inclusive B decays

Precise measurement of B0s-B0

s mixing:

ms, s and phase s.

Completing the program on B Physics…Completing the program on B Physics…Completing the program on B Physics…Completing the program on B Physics…



B-factories B-factories vs.vs. b-factoryb-factoryB-factories B-factories vs.vs. b-factoryb-factory

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



Experimental sensitivityExperimental sensitivityExperimental sensitivityExperimental sensitivity

How to reach high sensitivities:

B production rate and detector acceptance trigger (incl. fully hadronic decays) background reduction

Good mass resolution Particle Identification

Good decay time resolution for Bs

flavour tagging



LHC Experiments LHC Experiments (that will do B-physics)(that will do B-physics)LHC Experiments LHC Experiments (that will do B-physics)(that will do B-physics)

ATLAS

100 b

230 b

Pythia production cross section

ATLAS and CMS: general purpose experiments central detectors, ||<2.5 B physics using high-pT muon triggers,

mostly with modes involving dimuon

LHCb: dedicated to B-physicsdesigned to maximize B acceptance Forward, single arm spectrometer, 1.9 < < 4.9

• more b hadrons produced at low angles • bb pairs produced correlated in space

“lower” pT triggers, including purely hadronic modes



Status of detectorsStatus of detectorsStatus of detectorsStatus of detectors

Oct. 05

Feb. 06 Nov. 05

Feb. 06

SCT

magnet

ECALHCAL

100K cool-down

Expect first collisions in summer 2007!



Luminosity and pileupLuminosity and pileupLuminosity and pileupLuminosity and pileup Pileup

number of inelastic pp interactions in a bunch crossing is Poisson-distributed with mean n = Linel/f

ATLAS/CMS (f = 32 MHz)

want to run at highest luminosity available expect L<21033 cm–2s–1

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

expect only B still possible LHCb (f = 30 MHz)

L tuneable by adjusting the beam focus choose to run at <L>~21032 cm–2s–1

(max. 51032 cm–2s–1)• clean environment (n = 0.5)• less radiation damage

(LHCb 8mm from beam, ATLAS 5 cm, CMS 4 cm)• will be available from 1st physics run

L instantaneous luminosityf non - empty bunch crossing rate inel 80 mb

2 fb–1 / year10 fb–1 in first 5 years

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

(nominal year = 107 s)

pp interactions/crossing

LH

Cb

n=0

n=1

AT

LA

S/C

MS



ATLAS triggerATLAS triggerATLAS triggerATLAS trigger

Full ATLAS trigger: LVL1: hardware, coarse detector granularity, 2 s latency LVL2: full granularity, LVL1 confirmation + partial rec., 10 ms processing EF (event filter): full event access, “offline” algorithms 1 s processing

Strategy for B physics trigger: High luminosity (> 21033 cm–2s–1):

LVL1: dimuon, pT > 6 GeV/c each Low luminosity (or end of) fills:

LVL1: add single muon, pT > 6–8 GeV/c

LVL2: look for objects around muon• 2nd muon (with lower threshold)

in muon RoI• Single e/ or e+e– pair in EM RoI

• Hadronic b decay products in Jet RoI (e.g. Bs Ds+ )

Trigger level

Total output rate

Output rate for B

physics

LVL1 75 kHz 10–15 kHz

LVL2 2 kHz 1–1.5 kHz

EF 200 Hz 10–15 Hz



CMS triggerCMS triggerCMS triggerCMS trigger

Trigger to cover widest range of discovery physics (Higgs, SUSY, …) Level 1: (nominal) 3.2s buffer, 100 kHz HLT (High-Level Trigger): 1s buffer, 40 ms processing, 100 Hz

Trigger on B events: Level 1: di- with pT> 3 GeV/c each (or single with pT> 14 GeV/c) HLT: Limited time budget

restrict B reconstruction to RoI around or use reduced number of hits/track (Ds)

Trigger level

Totaloutput rate(at start-up)

Output rate relevant for B physics

Level 1 50 kHz 14 kHz (1) 0.9 kHz (2)

HLT 100 Hz ~ 5 Hz of incl. b,c+jet+ O(1 Hz) for each excl.

B mode



LHCb triggerLHCb triggerLHCb triggerLHCb trigger

Software trigger

Full detector info available, only limit is CPU time 1st stage: ~1 ms 40 kHz (could change)

Tracks with min. impact param. and pT + (di)muon

High-Level trigger: ~ 10 ms Full event reconstruction: excl. and incl. streams

Hardware trigger Fully synchronized (40 MHz), 4 s fixed latency “High pT” , , e, and hadron + pileup info (e.g. pT() > 1.3 GeV/c)

10 MHz (visible bunch crossings)

1 MHz (full detector readout)

≤ 2 kHz (storage)

Custom electronics boards

PC farm of ~2000 CPUs Output rate

Event type Physics

200 Hz

Exclusive B candidates

B (core program)

600 Hz

High mass di-muons

J/, bJ/X (unbiased)

300 Hz

D* candidates

Charm

900 Hz

Inclusive b (e.g. b)

B (data mining)

exact splitting between streams can be optimized according to physics requirements large inclusive streams to be used to control calibration and systematics (trigger, tracking, PID, tagging)



Tracking performanceTracking performanceTracking performanceTracking performance

Proper time resolutionATLAS: t ~ 95 fs

CMS: t ~ 100 fsLHCb: t ~ 40 fs

BsDs proper time resolution

t ~ 40 fs

Mass resolutions in MeV/c2

ATLAS CMS LHCb

Bs 80 46 18

Bs Ds 43 – 14

Bs J/ 36 32 16

Bs J/ 16 13 8

Good proper time resolution essential for time-dependent Bs

measurements !

without J/ mass constraint

with J/ mass constraint

LHCb



Particle ID performance of LHCbParticle ID performance of LHCbParticle ID performance of LHCbParticle ID performance of LHCb

Fully simulated pattern recognition in two LHCb RICHes: Good K- separation achievable in 2–100 GeV/c range Reconstruct rings around tracks found in tracking

Kaon ID: ~88%

Pion mis-ID: 3%

π π hypothesis

No RICH

Requirements: Background suppression => high momentum hadrons in two-body B decays B flavor tagging (identify K from b→c→s) => low momentum hadrons



Flavour taggingFlavour taggingFlavour taggingFlavour tagging

LHCb: Most powerful tag is opposite kaon (from bcs) Combined D2 ~ 6% (Bs) or ~ 4% (B0)

Recent neural network approach leads to ~9% for Bs

Compare with: Tevatron: D0 ~2.5% , CDF ~1.5% OS and ~4% SS B factories achieved ~ 30%

Tagging power D2 = (1–2w)2 in %

Tag LHCb ATLAS CMS(1999)

Muon 1.0 0.7 (0.6)

Electron 0.4 0.4 (0.5)

Kaon 2.4

Jet/vertex 1.0 1.8–2.1 (2.3)

Same side 2.1 2.1–2.4 (2.2)

Qvtx

BsB0

D

l-K–

K+PV

SV



Expected Physics PerformanceExpected Physics PerformanceExpected Physics PerformanceExpected Physics Performance

B-mixing: “control channel” B0J/ KS

ms with Bs0 Ds

s and s with Bs J/ ()

Suppressed and rare decays: Exclusive b s +-

Bs0 +-

Measurement of from Bs DsK from B DK*

from B± DK±

from B and BsKK



sin(2sin(2) from B) from B00J/J/ K KSSsin(2sin(2) from B) from B00J/J/ K KSS

“gold-plated” decay channel at B-factories for measuring the Bd- Bd mixing phase

needed for extracting γ from B π π and Bs K K, or from B D*π

in SM ~0, non-vanishing value O(0.01) could be a signal of Physics Beyond SM

dirCPA

ACP(t) (background subtracted)

LHCbOne of the first CP measurements at LHC: demonstrate CP analysis performance study tagging systematics

Expected sensitivity:

LHCb: 240k signal events/year

stat(sin(2)) ~ 0.02 (1year, 2fb-1) (0.6°)

ATLAS: similar sensitivity for (first 3years, 30fb-1)

Search for direct CP violating term…



S/B ~ 3 (derived from 107 fully simulated inclusive bb ev.)

BBss oscillations oscillationsBBss oscillations oscillations Measurement of ms is one of the first LHCb physics goals

Expect 80k Bs Ds+ events per (1year, 2fb–1), average t ~ 40 fs

LHCb

LHCb: 5 observation for ms<68ps–1 in (1year,2fb–1), for ms<40ps–1 in (~1month,0.25fb–1)

ATLAS/CMS: 5observation for ms 22 ps-1 in (3years, 30fb-1)

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

LHCb



J/ is not a pure CP eigenstate: 2 CP even, 1 CP odd amplitudes contributing need to fit angular distributions of decay final states as function of proper time (needs external ms) requires very good proper time resolution

Expected sensitivity: (at ms = 20 ps–1)

LHCb: 125k BsJ/ signal events/year

stat(sin s)~0.031, stat(s/s)~ 0.011 /(1year, 2fb–1) stat(sin s)~0.013 after first 5 years, adding pure CP modes like J/η, J/η’ (small improvement) ATLAS: similar event rate as LHCb but less sensitive stat(sin s)~0.08 (1year, 10fb–1) CMS: > 50k events/year, sensitivity study ongoing

ss and and ss from B from BssJ/J/ ( (ηη,,ηη’…)’…)ss and and ss from B from BssJ/J/ ( (ηη,,ηη’…)’…)

στ= 38 fs LHCb

SU(3) analogue of B→JKs measuring the Bs- Bs mixing phase in SM s = –arg(Vts

2) = –22 ~ –0.04 increased sensitivity to New Physics large CP asymmetry would signal Physics Beyond SM

also needed for extracting from Bs Ds K or from B π π and Bs K K



Exclusive b Exclusive b s s Exclusive b Exclusive b s s

s = (m)2 [GeV2]

AFB(s) for B0K*0

s = (m/mb)2^

AFB(s) for b+– ^

MSSM C7eff>0

ATLAS expectation for (3yrs, 30 fb–1)

SM

Expected sensitivity:LHCb:

4400 B0K*0 events/(yr,2fb–1), S/B>0.4

determine C7eff/C9

eff with 13% error (SM)ATLAS:

1000 B0 K*0 events/(yr,10fb–1), S/B>1

Other exclusive b s feasible (Bs, b)

Suppressed decays B=1 FCNC) SM BR ~ 10–6

Forward-backward asymmetry AFB(s) in the rest-frame is a sensitive probe of New Physics [A.Ali et al., Phys. Lett. B273,505 (1991)]

Zero point can be predicted at LO with no hadronic uncertainties, known at 5% level in SM, sensitive to NP via non-standard values of Wilson coefficients



BBss ++––BBss ++––

Very rare decay, sensitive to new physics BR ~ 3.5 10–9 in SM, can be strongly enhanced in SUSY Current limit from Tevatron:

D0: 2.310–7 at 95% CL CDF: 1.010–7 at 95% CL

LHC has prospect for significant measurement

but difficult to get reliable estimate of expected background:LHCb: Full simulation: 10M incl. bb events + 10M b, b events (all

rejected)ATLAS: 80k bb events with generator cuts, efficiency assuming cut

factorizationCMS: 10k b, b events with generator cuts, trigger simulated at generator

level, efficiency assuming cut factorization

New assessment of ATLAS/CMS reach at 1034 cm–2s–1 in progress

1 year Bs + – signal (SM)

b, bbackground

Inclusive bb background

Other backgrounds

LHCb 2 fb–1 30 < 100 < 7500

ATLAS 10 fb–1 7 < 20

CMS (1999) 10 fb–1 7 < 1



BsDsK

BsDs

2 time dependent asymmetries from 4 decay rates: Bs (Bs) Ds K , D

s K

2 tree decays (b→c and b→u) of same magnitude (~λ3) interfere via Bs mixing insensitive to new physics large interference effects expected CP asymmetry measures (+ s), with s being determined using Bs → J/ needs suppression of Bs Dsπ background (BR~12 higher)

from Bfrom Bss D DssKK from Bfrom Bss D DssKK

Expected LHCb signal rates and background: 5400 signal events in (1year, 2fb-1) residual contamination from Bs Dsπ ~ 10% S/Bbb > 1 at 90% CL (from one MC bb event)

Important for selection: hadron trigger mass resolution proper-time resolution K/separation

s

s

b

c

u

s

Bs0

Ds

K

K–

s

s

b

u

c

s

Bs0

Ds



Expected LHCb sensitivity:

(at ms = 20ps-1 , -°°) ° in (1year, 2fb-1)

(expected to be statistically limited) Discrete ambiguities in can be resolved

• if s large enough, or

• using B0→D and U-spin symmetry

from Bfrom Bss D DssKK from Bfrom Bss D DssKK

Fit the 4 tagged, time-dependent rates:

phase of Ds K = s)

phase of Ds K = s)

extract both and s

DsK asymmetries (5 years, ms=20 ps–1)

Ds–K+

Ds+K–



Dunietz variant of Gronau-Wyler method [Phys. Lett. B270, 75 (1991)]

Two colour-suppressed diagrams with |A2|/|A1| ~ 0.4 interfering via D0 mixing

6 decay rates, self-tagged and time-integrated

from Bfrom B00 D D00K*K*00 from Bfrom B00 D D00K*K*00

Mode (+ CP conjugates) Yield S/Bbb (90%CL)

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

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

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

d

b

d

s

u

c

B0

D 0

K*0

D0

d

b

d

s

c

u

B0

K*0

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

Expected signal rates and background: (1year, 2fb-1), °,

Expected LHCb sensitivity: ° in (1year, 2fb-1) for 55°<°-°°



from Bfrom B± ± DK DK±± from Bfrom B± ± DK DK±±

u

b

u

s

c

u

B–

D 0

K–

colour-suppressed

u

u

b

c

u

s

B–

D0

K–

colour-allowed

based on Atwood-Dunietz-Soni method [Phys. Rev. Lett. 78, 3257 (1997)] measure relative rates of B → D(K) Kand B → D(K) K

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

K)

Measure relative B-decay rates:

Magnitude ratio: rDK

Strong phase diff.: DK

3 observables, 5 parameters (DKrB, rD

K , but rDKknown

add more D-decays to constrain further…

Weak phase diff.: Magnitude ratio: rB

Strong phase diff.: B

}K

}

Cabibbo-favoured

D0{cu

udsu

}K

}

Double Cabibbo-suppressed

D0{cu

usdu



from Bfrom B± ± DK DK±± from Bfrom B± ± DK DK±±

Add further D-decays: D → K (Cabibbo favoured + DCS decay)

4 new rates with 2 new parameters, one known: DK3rD

K3 D → KK (CP eigenstate)

2 new rates, no new unknown: rDKK ; D

KK = 0

Further B-channel considered… B± D*K± with

• D*→ D0 D* and D0have same CP

• D*→ D0 D* and D0 have opposite CP

7 relative rates and 5 unknowns: rB, B, DK, D

K3

Candidate for LHCb’s statistically most precise determination of Estimated sensitivity: ° in (1year, 2fb-1) Studies ongoing…



from Bfrom B and B and BssKKKK from Bfrom B and B and BssKKKK

large penguin contributions in both decays sensitive to New Physics measure time-dependent CP asymmetry for B and BsKK

ACP(t) = Adir cos(mt) + Amix sin(mt) Adir and Amix depend on mixing phases, and ratio of penguin to tree = d ei

exploit “U-spin” symmetry (ds) [R.Fleischer, Phys.Lett. B459, 306 (1999)]

ddKK and KK

4 measurements and 3 unknowns,

if mixing phases from B0J/KS and BsJ/

Important for selection: hadron trigger K/ separation mass resolution proper-time resolution

Expected sensitivity: 26k B , 37k BsKK, 135k BK

° in (1year, 2fb-1)

()

dBs KK (95% CL)

B

(95% CL)

Bd/s

Bd/s

/K

/K

/K

/K



ConclusionConclusionConclusionConclusion Experiments at LHC will pursue an extensive program on B-physics

with high statistics access to Bs decays

LHCb can fully exploit the large B-meson yields at LHC from the start-up with excellent mass and decay-time resolution, and particle ID with a flexible and robust trigger dedicated to B-physics measure e.g. ms with 5 in ~1month (for ms <40 ps-1)

ATLAS and CMS will also contribute significantly competitive for modes with muons and small BR

Flavor Physics at LHC will contribute significantly to the search for NP via precise and complementary measurements of CKM angles and the study of loop decays

After 5 years: SM expectation

s(Bs→ ccss) ~Br(Bs→ ) ~0.7 ~DsK, DK) ~1 ~60 (tree only) ) ~2 ~60 (tree + penguin)



Backup slidesBackup slidesBackup slidesBackup slides



W

b u,c,t s

BB00 →→ K K0* 0* and B and Bs s →→ BB00

→→ K K0* 0* and B and Bs s →→

In SM: loop-suppressed b → s transitions BR( B0 K*0 ) = (4.30.4) 10-5

expected direct CP violation <1% for B0→ K*0 expected CP violation in mixing ~0 for Bs→ sensitive to New Physics

m~ 64 MeV/c2

In 1 year LHCb expects triggered and reconstructed:35k events B K(K ; S/B>1.49.4k events Bs (K+K+) ; S/B>0.4

B→ K Bs→ KK

~ 60 fs Preliminary study: for B→K 0* (ACP ) < 0.01 for one year LHCb for Bs → sensitivity study ongoing

ATLAS expected signal events/year: Bd K*0 : ~3.3k ev. ; S/√BG > 5Bs : ~1.1k ev. ;S/√BG > 7



M20M 2 0

Time-dependent Dalitz plot analysis of B0 permits extraction of along with amplitudes + strong phases[Snyder & Quinn]

Neutral reconstruction with clusters unassociated to charged tracks Annual yield ~ 14k events, S/B ~ 1.3 (LHCb)

Complicated 11-parameter fit, studied with toy MC Statistical precision of () ~ 10 achievable in one yearStudy of B0 has started, few 102 /year (for BR =

from Bfrom B00 from Bfrom B00

Resolved

Merged

Efficiency for reconstruction

L.R. Evans – EDMS Document No. 712870 31

LHC underground

L.R. Evans – EDMS Document No. 712870 32

LHC status (March 2006)

• All key objectives have been reached for the end of 2005.

• End of repair of QRL, reinstallation of sector 7-8 and

cold test of sub-sectors A and B.

• Cool-down of full sector 8-1.

• Pressure test of sector 4-5.

• Endurance test of two full octants of power converters.

• Magnet installation rate is now at 20 per week with more

than 450 installed (25%). In the next month, we will ramp

up to 25/week. Installation will finish end February 2007.

vancouver, 9-12 april 2006 flavor physics and cp violation at lhc cryogenic services line lhc dipole...

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