1. Bs Physics and Prospects at the Tevatron
Donatella Lucchesi
for the CDF and D0 Collaborations
CKM Workshop Durham April
The status of Bs physics at the Tevatron
Lifetimes
Mixing
Other related talks :
J. Rademacker talk for lifetimes and lifetime differences
R. Oldeman presentation about detector performances
I. Villa talk about SVT trigger
Donatella Lucchesi

2. How do we collect Bs Old style:
Di-muon trigger: low Pt respect to Run I  much more J/
BsJ/ “BsJ/”
New era:
Hadronic trigger (SVT): displaced tracks
all hadronic decays
A combination of Old and New
Lepton + displaced track trigger
BslDsX
Donatella Lucchesi

3. Exploiting the J/: Mass Measurement
m(Bs)=5360.3±3.8(stat) (sys) MeV/c2 ichep result
+2.1
-2.9
ichep
Donatella Lucchesi

4. BsJ/: Lifetime Measurement
tB0=1.42±0.09(stat)±0.02(sys)
tBs=1.26±0.20(stat)±0.02(sys)
tBs/tB0 = 0.89±0.15(tot.)
Donatella Lucchesi

5. Lifetime measurement: semi-leptonic decays
Muons
Electrons
Signal to noise ratio better
than expected !
Observed yield: RunI5
Donatella Lucchesi

6. Lifetime and DG Perspectives
CDF lifetime expectation in 2 fb-1 are:
BsJ/ and BslDsX combined  s(DG/G)few %
for both CDF and D0 (see Jonas talk for details)
CP asymmetry in BsJ/ expected small in S. M.
If bigger  new physics
If Dms larger:
difficult to measure also with high statistics sample
DG/G sizeable  easy to measure
Dms = DG·C where C can be calculated inside the S. M.
Semi-leptonic decays
Fully reconstr. decays
s(ct)/ct 2%
0.5%
Donatella Lucchesi

7. Xs=DmsBs measurement: semi-leptonic decays
Decays included:
Bs  Dsl, Ds*l
(Ds, K*0K, +)
~40K events in 2 fb-1
Proper time resolution:
t = 60 fs  t  K/K
K/K ~ 14%
Tagging:
D2 = 11.3 % (all taggers)
CDF
Current limit Xs> 20.6
Sensitive up to xs  30
Donatella Lucchesi

8. Bs mixing in fully hadronic decays
Fully reconstructed decays
Decays included:
Bs Ds, Ds
(Ds, K*0K, K*K0)
BsJ/K*0
Proper time resolution:
0.40 ps
Tagging:
D2 = 3.1 % Jet Charge
D2 = 4.7 % Lepton
S/B: 1:2
Donatella Lucchesi

9. Optimize tracking and flavor tagging
Current status of D0
Total Luminosity: ~40 pb-1
Many B reconstructed see Jonas talk.
Optimize tracking and flavor tagging
B+J/K+
Pt>2 GeV all tracks
2.8 < mμμ < 3.3 GeV
B decay length >0.3 mm
Donatella Lucchesi

10. Bs mixing at D0: Flavor tagging
DØ Run-II Preliminary
Muon
Jet Charge
(%)
8.2±2.2
55.1±4.1
D(%)
63.9±30.1
21.1±10.6
D2 (%)
3.3±1.8
(3.1 pred.)
2.4±1.7
(4.7 pred.)
Donatella Lucchesi

11. Current status of CDF: Yield Study
Hadronic trigger
First observation !
Can we measure the yield?
fs/fd: discrepancy LEP - CDF
Branching Fraction: unknown
Cross section: big uncertainty
Donatella Lucchesi

12. Current status of CDF: Yield Study
N(Bs)
N(Bd) fs fd es ed
Br(BsDs-p+) Br(Ds--) Br(k+k-) =
Br(BdD-+) Br(D-k+--)
PDG
Monte Carlo
Big effort in a full detector
and trigger simulation
optimization “a la LEP”
to measure the efficiencies
Donatella Lucchesi

13. Current status of CDF: Yield Study
BdD-+ , D-k+--)
reconstructed
New ! fs fd
Br(BsDs-p+)
Br(BdD-+)
= 0.42 ± 0.11(stat.) ± 0.11(Br.) ± 0.07(syst.)
Donatella Lucchesi

14. Conclusions CDF starts doing measurements with: Bs semileptonic decays
BsJ/ and fully reconstructed hadronic decays
D0 has less integrated luminosity  tools optimization
Several improvements underway:
removing trigger rate limit
SVT increase efficiency
flavor tagging optimization Bd mixing measurements for
the summer
add all the other Ds decay channels
( see Rolf presentation for details)
Donatella Lucchesi

15. Backup slides
Donatella Lucchesi

16. CP violation in Standard Model: g at CDF
1) R. Fleischer proposal:
Fit the asymmetries in the B0/BsKK
ACP=ACP(dir)cos(mt) + ACP(mix)sin(mt)
How do we separate /K/KK/K:
Inv. mass ~ 20 MeV/c2
Kinematical variables
dE/dX
Md << Ms
—sum
BdK
BsKK
Bd 
BsK 
RunIIa: ACP(dir, mix)~0.2 (Bd)
~0.1 (BsKK)
() = ±10(stat) ±3(theory)
Donatella Lucchesi

17. Bs mixing in fully hadronic decays
Trigger on displaced tracks
Many Ds reconstructed
CDF
+ Ds
+ DsKs
+ Ds  K*0K
…and the Bs?
Donatella Lucchesi

18. Bs mixing at CDF: Flavor tagging
Lepton (muon and electron) tagging: under optimization in
a huge sample of B from the lepton+displaced track trigger
Same Side Tagging
Donatella Lucchesi

19. Xs = Dms Bs measurement: CDF expectations
80K
40K
20K
10K
70K
60K
50K
30K
Number of events for 5 sigma observation
Fully reconstructed decays
Decays included
B0s Ds, Ds
(Ds, K*0K, +)
Proper time resolution:
t = 45 fs  t  Pt/Pt (L00+SVX)
Tagging:
D2 = 11.3 % (all taggers)
S/B:
2:1, 1:1, 1:2
Donatella Lucchesi

20. CP violation in Standard Model: g at CDF
2) R. Aleksan et al. Z Phys. C (1992) proposal:
BsDsK time dependent decay rate depends on:
sin(dg) and cos(dg)
Theoretically clean
Reasonable Branching ratio
Background BsDsp
Need tagging
Need time dependent analysis
Ds
Ds*K
Ds*
DsK
S/B = 1/6
S/B = 1
~ events in RunIIa
~ 3500 events in RunIIb
Donatella Lucchesi

21.  via B0 / BsKK R. Fleischer:
B0 measure sin2(+) ( ~30% penguins contamination)
P/T ratio measurement with a simultaneous fit of BsKK asymmetry
Dominant
Sub-dominant u - b W d
u,c,t s
B0
BsKK
Measurement of 4 asymmetries time dependent
Fit of d=P/T ~ 0.3, =strong phase of P/T, ,  constrained from sin(2)
Donatella Lucchesi