CP measurements in Bs decays to charm

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CP measurements in Bs decays to charm

• Azizur Rahaman
• (for the CDF collaboration)
• University of Pittsburgh

4th International Workshop on the Unitarity
Triangle Nagoya University, Nagoya,
Japan December 12-16, 2006
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Plan

• Introduction
• B-physics at Tevatron
• CDF-II detector
• Towards the measurement of angle ?(F3)
• CKM Matrix and angle ?
• GLW Method
• Measurement of BR(B-?D0K-)/BR(B-?D0p-)
• Towards the measurement of ?G/G
• Motivation
• Mehodology
• Measurement of BR(Bs?DsDs-)/BR(B0?DsD-)
• Conclusion and summary

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B-physics at Tevatron
World Highest Energy Collider
CDF
D0

• Tevatron is a source of all B-hadron
• species Bd, Bu, Bc, Bs, ?b, Sb ..
• sb 29.4 0.6 6.2 µb (? lt 1) at CDF
• Huge cross-section compared to B-factories
• but proportionally large backgrounds ( 103 )
• Events have to be selected with
• specific triggers

• RUN II started in 2001
• vs1.96 TeV
• Record luminosity
• L 237.0 1030cm-2s-1
• Delivered ?Ldt 2.0 fb-1

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Displaced track trigger
Silicon Vertex Trigger (SVT)
Applied at L2 in a cascade of three level trigger
system

• Hadronic B trigger
• at least two tracks with
• pT gt 2 GeV
• 120 µm lt d0 lt 1 mm

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CDF-II detector

• CDF II Detector
• multi-purpose detector
• excellent momentum
• resolution s(p)/plt0.1
• Vertex resolution
• SVXII, L00
• Particle Identification
• TOF, dE/dx in COT

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CKM Matrix and angle ?
The CKM matrix
Wolfenstein parametrization ? 0.2272 0.0010
B0?pp, ?p s 10-120
The orthogonality condition between 1st and 3rd
column
B0?J/?Ks s 1.60
Expect 5790
Test SM measure all sides and angles and check
the consistency
A very naïve cross check a (F2) ß (F1) ?
(F3) 2p
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Methods to measure ?

• Several ways to measure F3
• depending on D0 decay mode
• GLW Method flav CP
• ADS Method flav DCS
• Dalitz Method Ks0pp-
• Consider B- ? DCPK-
• with DCP 1/v2(D0 D0)
• Example DCP
• CP even KK-, pp-
• CP odd Ksp0, KsF, Ks?, Ks?0

-
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GLW Method
PLB 253 (1991) 483 PLB 265 (1991) 172
where
Construct two triangles from above six
processes which give one of the solutions for
? Note

gt No CP violation
?
gt CP violated
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GLW Method (cont)

• But Interference between

• Use theoretical relations

ADS Method PRD 63 036005 PRL 78 3257 Stat limited
and

• Solution M. Gronau, PRD 58, 037301

• Instead measure

• ACPRCP ACP-RCP- 0
• This talk covers the
• measurement of R

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Event reconstruction

• Analyzed 355 pb-1
• Reconstruct D0 ? K-p
• Add another track with p mass
• hypothesis to make B

Data
MC
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Likelihood fit

• Unbinned multidimentional likelihood
• fit, which combines kinematics and
• dE/dx informationMDp, ptot, PID and a
• where a 1 - ptot/pD ptot lt pD
• -(1 - pD/ptot) ptot
  pD
• Fit mass window 5.17 5.60 GeV

• a separates between
• D0p and D0K modes
• Good K-p separation
• 1.4 s for pT gt 2 GeV

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Fit results
CDF Public Note 8242

• N (D0p) 3265 38
• N (D0K) 224 22
• For same yields, resolutions
• is same as B-factories !

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DCP (KK, pp) Modes

• Analysis with 1 fb-1 is nearly complete
• Resolution expected for RCP and ACP would be
• comparable to the current resolution of
  B-factories

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Bs ? DsK Mode
R. Fleisher Nucl Phys B 659 (2003)

• Final states of both sign are
• accessible by both Bs mesons
• with similar sized amplitude
• Bs oscillation is then cause the
• amplitude to interfere
• This is the cleanest channel to
• measure ? but time dependent
• CP asymmetry measurement is
• needed

Expect 200 events in 1 fb-1
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Motivation

• Final goal is to measure BR(Bs?Ds()Ds()- ) to
  determine
• ?Gs/Gs
• No time dependent analysis or tagging needed
• Bs ? DsDs- is pure CP-even while
  Bs?Ds()Ds()- is
• predominantly CP-even final state and gives the
  largest
• contribution to ?Gs
• 2BR(Bs?Ds()Ds()) ?GCP/G
• where ?GCP ?Gs/cosF
• BR(B0?Ds()D()-) could be used to measure CP
  phase ?
• 
  hep-ph/0410015

• Dunietz, R. Fleischer and
• U Nierste hep-ph/0012219

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Methodology

• Measure BR normalized to a more abundant channel
  with same topology as the signal
• Reconstruct multiple final state
• Normalized channel B0?DsD-
• D- ? Kp-p-
• Ds ? Fp (F ? KK-) , K0K (K0 ? Kp-),
  p-pp
• Signal channel Bs ? DsDs-
• First Ds ? Fp with F ? KK-
• Other Ds- ? Fp- , K0K- (K0 ? Kp-), pp-p-
• Yield determination By fitting invariant mass
• Get templates from MC for physics background
• Float fractions with fixed shapes
• Estimate relative reconstruction efficiency from
  MC and use PDG values to calculate the branching
  fraction ratio

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Normalized modes
Normalized modes

• Measure BRs on other modes with
• similar topology to test the tools

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Signal modes
Observation of Bs ? DsDs For both
Ds?Fp Observed 9.1 3.2 candidates
corresponding to 6.7s
Total of 23.5 candidates all three decay modes
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BR results
CDF Note 7925

1.67 0.41 (stat) 0.12 (syst) 0.24 (fs/fd)
0.39 (Br)
World first measurement !!
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Conclusion and summary

• We have measured
• This is the first step towards ? measurement
• Analysis with 1 fb-1 is near complete and expect
  same resolution on RCP and ACP compared to
  B-factories
• Observation of Bs?DsDs mode and measured
• Analysis with 1 fb-1 coming soon ! Stay tune!

1.67 0.41 (stat) 0.12 (syst) 0.24 (fs/fd)
0.39 (BR)
- World first measurement !!
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BACK UP
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Systematics
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Systematics