November 24th, 2008 Flavor physics: The mexican taste 1

Bs mixing and CPV at D0 & ATLAS B physics future

Eduard De La Cruz BureloCINVESTAV

November 24th, 2008 Flavor physics: The mexican taste 2

Outline:

• What are we doing in D0 on B Physics?• What are the plans for B physics in

ATLAS?

http://www-d0.fnal.gov/Run2Physics/WWW/results/b.htm

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The B hadron family

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The useful Bs

• QCD modeling: compare & contrast with Bd– SU(3) Flavor Symmetry, Heavy Quark Effective Theory– Lattice …

• Direct search for beyond de SM effects– Rare (leptonic) decays: many models predict large effects in Bs.

• EW symmetry breaking– In SM: EW sym. breaking ↔ Flavor struct. (CKM, CPV)– 1 SM Higgs doublet strong flavor constraints

• FCNCs suppressed Unitary VCKM • 1 param. for all CPV No CPV in flavor diag. processes

– Other model much less constrained• eg. 43 CPV parameters in MSSM• Different relationships b/w observables from different families

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Mixing and CP violation

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D0/CDF battle

• Bs mixing

• CP violation in BsJ+

Bd sides ≈ Vub/Vtd ≈ 1 Bs sides ≈ Vub/Vts ≈1/20

Real CKM axis

Im C

KM

axis Large CPV phase in Bd→J/

KS

Small CPV phase in Bs→J/

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Bs mixing phenomenology• Mixing or oscillation: Particle ↔

antiparticle transitions via second order weak interaction.

• Mass eigenstates a mixture of flavor states:

• Probability of unmixed and mixed decays:

BpBqB

BpBqB

L

H

)cos1(2

)(

)cos1(2

)(

mteBBp

mteBBp

t

t

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Flavor tagging methods: OST & SSKT

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Data

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Amplitude scan:

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Likelihood scan

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Oscillation frequency ms

ms

|s|/ms

asfs

sSMss mm

s plane

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BsJ+ : CP violation via Bs mixing

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CP violation in BsJ+

• BsJ+ combines many aspects– vector + vector final state so it has both CP-

even and CP-odd components.– Measurable lifetime difference so you can tell

the difference between BsLong and Bs

Short

– CP eigenstate so accessible to both Bs and Bs bar, interference with decay before or after mixing

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CP violation in BsJ+

We can use angular distribution of decay products to separate CP-even and CP-odd components. And flavor tagging algorithms can we used to know the original flavor.

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Lifetime analysisBs decay length J/ + polarization

BsShort component

even component

BsLong component

odd component

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CP violation in BsJ+Strong phases constrained

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CDF+D0 combined results Without constraints in strong phases

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Where do we go now?

s from BsDs(*)Ds

(*) (purely CP even)

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s from BsDs(*)Ds

(*)

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B Physics in ATLAS

100 fb–1

100 pb–1

10 pb–1

Integrated luminosity

Initial detector and trigger synchronisation and commis-sioning, calibration & alignment, material mapping, …Measuring production cross section

B-hadron properties, new decay limitsUnderstand backgrounds for rare decays

Production and decay properties of B-hadrons

TimeLHC startup

Test beams, Cosmic runs, Pre-alignment and calibration, Data distribution dress rehearsals

1 fb–1

10 fb–1

Rare decays

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Semi-rare decays• b → → s(d)l+l- FCNC transitions in

SM – forbidden at the tree level, at

lowest order occur through 1-loop penguin and box diagrams

– branching ratio ~ 10-6 - 10-7

• They provide a good test of the SM and indirect search for signals of physics beyond the SM– measure values of |Vts| and |Vtd|

CKM matrix– differential decay rate sensitive to

new physics• forward-backward

asymmetry• dilepton invariant mass

spectrum– provide information on long-

distance QCD effects

Decay Channels

Bd → K0*+-

Bs → +-

B+ → K++-

B+ → K+*+-

b → 0+-

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b d,s +- @ 30fb-1

B K

SM non-SM

Decay Channel Theory BR Cross-

Section Events AFB in the range(1-6)

Bd → K0*+- 1.3 x 10-6 2.5 pb 2500 4.8%

Bs → +- ~10-6 0.57 pb 900 6%

B+ → K++- 3.4x10-7 2.0 pb 4000 3.%

B+ → K+*+- ~10-6 2.1 pb 2300 5.2%

b → 0+- 2.0 x 10-6 1.2 pb 800 6%

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Rare decays• Very rare decay Bs→:

SM - BR (Bs →) = (3.4 0.4)10-9

• Current limits (2fb-1):– CDF note 8956

BR (Bs →) < 5.8 10-8 95% CL– D0 note 5344-CONF

BR (Bs →) < 7.5 10-8 90% CLBR (Bs →) may be enhanced by severalorder of magnitudes due to new loopdiagrams• Anomalous magnetic moment of the

– Muon g – 2 collab. measurement deviates by 2.7 from SM: a = (25.29.2)10–10

• Implications on Bs +– within constrained MSSM:

– 250 < m1/2(gaugino mass) < 650 GeV BR (Bs ) = 510 –9 – 10–7

Current Tevatron limit

The CMSSM prediction for BR (Bs → μ+μ−)

hep-ph/0411216

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Bs+- @ ATLAS

• With 2 fb-1

BR<(0.7-2)10-8

• With 10 – 30 fb-1 SM prediction region

• 3 years 1033 cm-2s-1

3σ evidence• First year 1034 cm-2s-1

5σ evidence