cp measurements in bs decays to charm
DESCRIPTION
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. Plan. Introduction B-physics at Tevatron CDF-II detector - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/1.jpg)
CP measurements in Bs decays to charm
Azizur Rahaman(for the CDF collaboration)
University of Pittsburgh
4th International Workshop on the Unitarity TriangleNagoya University, Nagoya, Japan
December 12-16, 2006
![Page 2: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/2.jpg)
Plan
• Introduction– B-physics at Tevatron– CDF-II detector
• Towards the measurement of angle γ(Φ3)
– CKM Matrix and angle γ– GLW Method– Measurement of BR(B-→D0K-)/BR(B-→D0π-)
• Towards the measurement of ΔΓ/Γ– Motivation– Mehodology
– Measurement of BR(Bs→Ds+Ds
-)/BR(B0→Ds+D-)
• Conclusion and summaryCKM 2006 2/21Azizur Rahaman
![Page 3: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/3.jpg)
B-physics at Tevatron
RUN II started in 2001:• √s=1.96 TeV• Record luminosity: L = 237.0 ×1030cm-2s-1
• Delivered: ∫Ldt ≈ 2.0 fb-1
• Tevatron is a source of all B-hadron species: Bd, Bu, Bc, Bs, Λb, Σb …..• σb = 29.4 ± 0.6 ± 6.2 µb (|η| < 1) at CDF• Huge cross-section compared to B-factories but proportionally large backgrounds (≈ 103 )• Events have to be selected with specific triggers
CKM 2006 3/21Azizur Rahaman
CDF D0
World Highest Energy Collider
![Page 4: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/4.jpg)
Displaced track trigger
CKM 2006 4/21Azizur Rahaman
Silicon Vertex Trigger (SVT) :
Hadronic B trigger:at least two tracks with• pT > 2 GeV• 120 µm < |d0| < 1 mm •
Applied at L2 in acascade of three level trigger system
![Page 5: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/5.jpg)
CDF-II detector
CDF II Detector: multi-purpose detector
• excellent momentum resolution σ(p)/p<0.1%
• Vertex resolution:• SVXII, L00
• Particle Identification:• TOF, dE/dx in COT
CKM 2006 5/21Azizur Rahaman
![Page 6: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/6.jpg)
CKM Matrix and angle γ
The CKM matrix:
A very naïve cross check:α (Φ2) + β (Φ1) + γ (Φ3) = 2π
Wolfenstein parametrization: λ = 0.2272 ± 0.0010
The orthogonality condition between 1st and 3rd column:
Test SM: measure all sides and angles and check the consistency
CKM 2006 6/21Azizur Rahaman
B0→J/ΨKs
σ ~ 1.60
B0→ππ, ρπ σ ~ 10-120
Expect ~ 57±90
![Page 7: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/7.jpg)
Methods to measure γ
Several ways to measure Φ3
depending on D0 decay mode– GLW Method : flav + CP– ADS Method : flav + DCS
– Dalitz Method : Ks0π+π-
Consider: B- → DCPK-
with DCP =1/√2(D0 ± D0)Example DCP :
CP even: K+K-, π+π-
CP odd : Ksπ0, KsΦ, Ksω, Ksρ0
-
CKM 2006 7/21Azizur Rahaman
![Page 8: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/8.jpg)
GLW Method
PLB 253 (1991) 483PLB 265 (1991) 172where
Construct two trianglesfrom above six processeswhich give one of the solutions for γ
Note:
CKM 2006 8/21Azizur Rahaman
=> No CP violation
≠
> CP violated
![Page 9: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/9.jpg)
GLW Method (cont…)
• But Interference between
and
• Solution: M. Gronau, PRD 58, 037301
• Instead measure:
• Use theoretical relations
• ACP+RCP+ + ACP-RCP- = 0
• This talk covers the measurement of R
ADS MethodPRD 63 036005PRL 78 3257Stat limited
CKM 2006 9/21Azizur Rahaman
![Page 10: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/10.jpg)
Event reconstruction• Analyzed 355 pb-1
• Reconstruct D0 → K-π+ • Add another track with π –mass hypothesis to make B
CKM 2006 10/21Azizur Rahaman
MC
Data
![Page 11: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/11.jpg)
Likelihood fit• Unbinned multidimentional likelihood fit, which combines kinematics and dE/dx information:MDπ, ptot, PID and α where α = 1 - ptot/pD ; ptot < pD
-(1 - pD/ptot); ptot ≥ pD
• Fit mass window [5.17 – 5.60] GeV
• α separates between D0π and D0K modes
• Good K-π separation 1.4 σ for pT > 2 GeV
CKM 2006 11/21Azizur Rahaman
![Page 12: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/12.jpg)
Fit results
• N (D0π) = 3265 ± 38
• N (D0K) = 224 ± 22
• For same yields, resolutions is same as B-factories !
CDF Public Note: 8242
CKM 2006 12/21Azizur Rahaman
![Page 13: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/13.jpg)
DCP (KK, ππ) 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
CKM 2006 13/21Azizur Rahaman
![Page 14: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/14.jpg)
Bs → DsK Mode
• 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 γ but time dependent CP asymmetry measurement is needed
Expect ~ 200 events in 1 fb-1
CKM 2006 14/21Azizur Rahaman
R. Fleisher Nucl Phys B 659 (2003)
![Page 15: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/15.jpg)
CKM 2006 15/21Azizur Rahaman
![Page 16: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/16.jpg)
Motivation• Final goal is to measure BR(Bs→Ds
(*)+Ds(*)- ) to
determine ΔΓs/Γs
• No time dependent analysis or tagging needed
• Bs → Ds+Ds
- is pure CP-even while Bs→Ds(*)+Ds
(*)- is predominantly CP-even final state and gives the largest contribution to ΔΓs :
2BR(Bs→Ds(*)Ds
(*)) ≈ ΔΓCP/Γ where ΔΓCP = ΔΓs/cosΦ
• BR(B0→Ds(*)+D(*)-) could be used to measure CP
phase γ hep-ph/0410015
I.Dunietz, R. Fleischer andU Nierste hep-ph/0012219
CKM 2006 16/21Azizur Rahaman
![Page 17: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/17.jpg)
Methodology• Measure BR normalized to a more abundant channel
with same topology as the signal• Reconstruct multiple final state:
– Normalized channel: B0→Ds+D-
• D- → K+π-π-
• Ds+ → Φπ+ (Φ → K+K-) , K*0K+ (K*0 → K+π-), π-π+π+
– Signal channel: Bs → Ds+Ds
-
• First Ds+ → Φπ+ with Φ → K+K-
• Other Ds- → Φπ- , K*0K- (K*0 → K+π-), π+π-π-
• 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
CKM 2006 17/21Azizur Rahaman
![Page 18: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/18.jpg)
Normalized modesNormalized modes• Measure BRs on other modes with
similar topology to test the tools
CKM 2006 18/21Azizur Rahaman
![Page 19: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/19.jpg)
Signal modes
Observation of Bs → DsDs
For both Ds→Φπ:Observed 9.1 ± 3.2 candidates corresponding to 6.7σ
CKM 2006 19/21Azizur Rahaman
Total of 23.5 candidates all three decay modes
![Page 20: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/20.jpg)
BR results
1.67 ± 0.41 (stat) ± 0.12 (syst) ± 0.24 (fs/fd) ± 0.39 (Br)
=
CDF Note 7925
CKM 2006 20/21Azizur Rahaman
World first measurement !!
![Page 21: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/21.jpg)
Conclusion and summary
• We have measured
– This is the first step towards γ 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)
CKM 2006 21/21Azizur Rahaman
- World first measurement !!
![Page 22: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/22.jpg)
BACK UP
CKM 2006 B0Azizur Rahaman
![Page 23: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/23.jpg)
Systematics
CKM 2006 B1Azizur Rahaman
![Page 24: CP measurements in Bs decays to charm](https://reader034.vdocuments.net/reader034/viewer/2022051115/5681481f550346895db54949/html5/thumbnails/24.jpg)
Systematics
CKM 2006 B2Azizur Rahaman