1. Patricia Burchat Stanford University
Physics from B Decays: Lifetimes, Mixing, CP-Violating Asymmetries and Rare Hadronic Decays
Some of the Highlights …
Patricia Burchat
Stanford University

2. Patricia Burchat, Stanford
Outline
The B Factory Experiments
B lifetimes and mixing
Time-dependent CP-violating asymmetries
CP charge asymmetries
B hadronic decay rates
Motivation for measurements.
How well have we measured these properties?
What have we learned?
DPF, May 27, 2002
Patricia Burchat, Stanford

3. The B Factory Experiments
BABAR/PEP-II
peak luminosity:
4.6 x 1033cm-2s-1 (~5 BB/s)
max lumi/24h: 303 pb-1
total recorded lumi to date: ~90 fb-1 recorded (~10% off-peak)
4.5-month shutdown starts July 1, 2002
Belle/KEK-B
peak luminosity:
7.2 x 1033cm-2s-1 (~8 BB/s)
max lumi/24h: 388 pb-1
total recorded lumi to date: ~80 fb-1 recorded (~10% off-peak)
2-month shutdown starts July 1, 2002
c.f. integrated luminosity for
Argus ( ): ~100 pb-1
CLEO ( ): ~16 fb-1
DPF, May 27, 2002
Patricia Burchat, Stanford

4. The Unitarity Trianglesc t
d s b
d•s* = 0
(K system)
s•b* = 0
(Bs system)
d•b* = 0
(Bd system)
These three triangles (and the three triangles corresponding to the rows) all have the same area. A nonzero area is a measure of CP violation and is an invariant of the CKM matrix.
apply unitarity constraint to pairs of columns
DPF, May 27, 2002
Patricia Burchat, Stanford

5. The Unitarity Trianglec t
d s b
Vtb*Vtd
Vub*Vud a g b
Vcb*Vcd
Orientation of triangle has no physical significance. Only relative angle between sides is significant.
apply unitarity constraint to these two columns
DPF, May 27, 2002
Patricia Burchat, Stanford

6. The Unitarity Trianglec t
d s b
(r,h)
Vtb*Vtd
Vcb*Vcd
Vub*Vud
Vcb*Vcd a g b
(0,0)
(1,0)
apply unitarity constraint to these two columns
DPF, May 27, 2002
Patricia Burchat, Stanford

7. Patricia Burchat, Stanford
We are sensitive to CP-violating CKM phases through interference between two decays with known (or unknown) CP-conserving relative phases.
Meson mixing provides a source of error-free non-CKM phase shift by 90o ( i ):
|B0 (t)  cos(Dm t/2) |B0 – i sin(Dm t/2) |B0 exp(2if),
where the CKM angle f is associated with the mixing box diagram.
Interference between two decay diagrams (e.g., tree and penguin amplitudes with different CKM phases) can lead to CP-violating asymmetries but interpretation depends on relative strong phase.
DPF, May 27, 2002
Patricia Burchat, Stanford DK

8. The Asymmetric-Energy B Factoriesp+ p—
(4S)
B0 / B0 Dz
e -
e +
e ±, m ±, K± tag
Dz ~ 255 mm for PEP-II: 9.0 GeV on 3.1 GeV
~ 200 mm for KEKB: 8.0 GeV on 3.5 GeV
DPF, May 27, 2002
Patricia Burchat, Stanford

9. Dt distributions with NO experimental effects
dN exp(–|Dt|/tB) ( 1 ± sin2b sin(DmDt) )
CP violation
CP states sorted by B tag flavor
Btag= B0
Flavor states sorted by mixing status
B0 B0 or B0 B0
B0 B0 or B0 B0
B Mixing
dN exp(–|Dt|/tB) ( 1 ± cos(DmDt) )
DPF, May 27, 2002
Patricia Burchat, Stanford

10. perfect flavor tagging and time resolution
realistic mistag and finite time resolution
~ (1 – 2w)
~ p / Dmd
Unmixed – Mixed
Unmixed + Mixed
Asymmetry  (1 – 2w) cos(Dmd Dt)
DPF, May 27, 2002
Patricia Burchat, Stanford

11. Increase in precision of B lifetimes and mixing frequency
Ratio of B+ to B0 Lifetime
1.060  0.029
1.083  0.017
10 measurements
+2 B Factory LEP
  Flavor Session V: U. Nierste (theory)
B0 Lifetime ( x ps)
1.548  0.032
1.542  0.016
+3 B Factory LEP
12 measurements
B0 Mixing Frequency ( x 1012 ps-1)
0.472  0.017
0.489  0.009
18 measurements
+3 B Factory LEP
  CKM/CP III and FP VIII
PDG2000
PDG2002
DPF, May 27, 2002
Patricia Burchat, Stanford

12. Prospects for future lifetime and mixing measurements
many preliminary lifetime and mixing results.
systematic uncertainties dominated by Dt resolution function and, for mixing, knowledge of the lifetime.
measure mixing and lifetime simultaneously
expect <1% uncertainty on Bd mixing in a few years.
measure DG.
test assumptions of CP/T/CPT symmetries.
  Flavor Session VIII, T. Meyer
DPF, May 27, 2002
Patricia Burchat, Stanford

13. Patricia Burchat, Stanford
sin2b
Vtb*Vtd b
Vcb*Vcd
DPF, May 27, 2002
Patricia Burchat, Stanford

14. Charmonium modes used for measuring sin2b
, c, c
One dominant decay amplitude  theoretically clean! c B0 s
KS,L d d
Both BABAR and Belle use six charmonium modes:
B  J/ Ks0, Ks0  p+p-, p0p0
B  J/ KL0
B  (2S) Ks0
B  c1 Ks0
B  J/ K*0, K*0  Ks0
B  c Ks0
  CKM/CP Session V, S. Olsen
Belle has observed a 6s signal that is most likely the not-well-established c(2S) charmonium state in B0  c(2S) Ks0 and B+  c(2S) K+
DPF, May 27, 2002
Patricia Burchat, Stanford

15. sin2b data samples in BABAR
c1 Ks
J/Y Ks
(Ks  p+p-)
J/Y Ks
(Ks  p0p0)
Y(2s) Ks
Bflav
Mixing
sample
J/Y K*0
(K*0  Ksp0)
J/Y KL
DPF, May 27, 2002
Patricia Burchat, Stanford

16. Patricia Burchat, Stanford
Belle
42 fb-1 (44 M BB) events (78% purity) evts with Dt meas’t
effective tagging efficiency: e=(27.0  1.2)%
sin2b = 0.82  0.12  || = 1.06  0.09 (stat)
hep-ex/
  CKM/CP Session I, Wang, Vahnsen
DPF, May 27, 2002
Patricia Burchat, Stanford

17. Patricia Burchat, Stanford
BABAR
56 fb-1 (62 M BB) tagged events with Dt (79% purity; 68% tagging e)
effective tagging efficiency: e=(25.1  0.8)%
sin2b = 0.75  0.09  || = 0.92  0.06  0.02
471 events
524 events
hep-ex/
  CKM/CP Session I, Rahatlou, Lange
DPF, May 27, 2002
Patricia Burchat, Stanford

18. Patricia Burchat, Stanford
Constraints on upper vertex of Unitarity Triangle from all measurements EXCEPT sin2b b
Regions of >5% CL
A. Höcker, H. Lacker, S. Laplace, F. Le Diberder, Eur. Phys. Jour. C21 (2001) 225, [hep-ph/ ]
DPF, May 27, 2002
Patricia Burchat, Stanford

19. Patricia Burchat, Stanford
World Average sin2b = 0.78  0.08
The Standard Model (and the CKM paradigm, in particular) wins again … at least at the current level of experimental precision, in this decay mode.
DPF, May 27, 2002
Patricia Burchat, Stanford

20. D(*)- D(*)- B0 B0 D(*)+ D(*)+ D*D*
Measurement of “sin2b” in bccd decays: D*D*+ and D*D+ c b t d
D(*)-
D(*)- c d B0 b c c B0
D(*)+
D(*)+ d d d d
Weak phase for tree decay is same as for bccs but watch out for penguins!
D*D* is vector-vector decay (L=0,1,2) so mix of CP=+1 and –1.
Fit for Sf and Cf (no penguin assumptions).
D*D*
Ntag = 76
Purity = 80%
D*D*
S =  0.45  0.05
C =  0.30  0.05
CP asymmetries in D* D+ have also been studied in BABAR.
  CKM/CP Session I, J. Albert
DPF, May 27, 2002
Patricia Burchat, Stanford

21. Future sin2b studies: B0  Ks
Pure penguin!
time-dependent asymmetries in B0  Ks measures sin2b.
direct charge asymmetries in B+  K+ sensitive to new physics.
DPF, May 27, 2002
Patricia Burchat, Stanford

22. B  K Branching Fractions (10-6) CLEO, Belle, BABAR
(stat. and syst. errors added in quadrature and symmetrized)
CLEO, Belle, BABAR
~60M BB pairs
BABAR K ±12 evts
 K+ 5.5±2.0, 11.2±2.4, 9.2±1.3
 K0 <12, 8.9±3.2, 8.7±1.8
 K*+ <23, <36, 9.7±4.2
K* ±4.4, 13.0±6.1, 9.2±1.3
 p+ < 5, 0.56
BABAR K ±8 evts
B( K) slightly favors pQCD over QCDf.
CP asymmetries also measured: consistent with 0.
  Flavor Session VI: A. Telnov
DPF, May 27, 2002
Patricia Burchat, Stanford

23. Patricia Burchat, Stanford
“sin2a”
Vtb*Vtd
Vub*Vud a
DPF, May 27, 2002
Patricia Burchat, Stanford

24. Patricia Burchat, Stanford
CP Violation in B0  p+p- u b t d p- p- u d B0 b u u B0 p+ d d p+ d d
|P/T| and relative phase d are unknown but can, in principle, be determined from an isospin analysis that requires measuring BF for B0p+p-, B0p+p-, B±p±p0, B0p0p0, and B0p0p0
 CKM/CP Session II, N. Sinha (theory)
DPF, May 27, 2002
Patricia Burchat, Stanford

25. Expectations/Prejudices…
Measure coefficients for both sinDmDt and cosDmDt terms (Spp and Cpp ).
Spp and Cpp are determined by a, b, |P/T|, and d. Assume
cf. Gronau and Rosner, Phys. Rev. D65, (2002)
  CKM/CP Session I, Wang, Vahnsen
DPF, May 27, 2002
Patricia Burchat, Stanford

26. Patricia Burchat, Stanford
Belle
Sππ= Cππ= -Aππ= ± 0.07
B0 tags
bkgd subtracted
~44M BB pairs
~60M BB pairs
BABAR
B0 tags
B0 tags
qq and Kp background
  CKM/CP Session II: Olsen, Sumisawa
Sππ= ± 0.37 ± 0.07 Cππ= ± 0.29 ± 0.07
DPF, May 27, 2002
Patricia Burchat, Stanford

27. Patricia Burchat, Stanford
Interpretation
BABAR
Belle
DPF, May 27, 2002
Patricia Burchat, Stanford

28. Other studies of “sin2a”
Belle B0  ’ KS
Penguin mediated.
Sensitive to new physics.
sin2a = 0.29 ± 0.54 ± 0.07
Many other studies of B (’)K (*) are being aggressively pursued.
Challenge to theoretical models to explain relative rates.
DPF, May 27, 2002
Patricia Burchat, Stanford

29. Patricia Burchat, Stanford
sin2
Vub*Vud g
Vcb*Vcd
DPF, May 27, 2002
Patricia Burchat, Stanford

30. Charmless Two-Body Decays
In decays such as B  K p, interference between the Tree and Penguin amplitudes can lead to CP asymmetries that depend on g AND the strong phase difference. Also, ratios of BF for various p p and K p decay modes are sensitive to the angle g.
Goal: Measure CP asymmetries AND branching fractions for all charmless two-body final states.
DPF, May 27, 2002
Patricia Burchat, Stanford

31. World average two-body results from CLEO, Belle, BABAR
Branching Fraction (10-6)
CP Asymmetry
p+p ± Cpp, Spp
p+p0 4.9±1.1 (Belle 3.5s/BABAR 5.2s)  
p0p0 < 5.2, 5.6, 3.4
K+p ±  
K+p ±  
K 0p ±1.7
K0p ±2.3
K+ K- < 1.9, 0.5, 1.1
K 0 K0 < 13, 13, 7.3
incompatible at 3.3s level
± 0.15 ± ± 0.10 ± 0.02
  CKM/CP Sessions I, M. Bona, II: B. Casey
DPF, May 27, 2002
Patricia Burchat, Stanford

32. Charmless Three-Body B Decays: why are they interesting?
Sensitive to same weak phases as charmless 2-body decays.
Dalitz plot analyses of 3-body decays can (eventually) be used to help disentangle relative strong phases.
Already being done in charm decays.
A long way to go in B physics, but we’re starting…
  Charm Session I, D. Asner
DPF, May 27, 2002
Patricia Burchat, Stanford

33. All B+K+h+h-, B0Ksh+h- and BKsKsh modes being studied by Belle
>4s signals in six of eleven 3-body modes being studied.
Studying resonance substructure.
Belle B+K+p+p-
237±23 events
K*(892)0 p+ and f0(980) K+ observed.
  Flavor Session I, N. Gabyshev
DPF, May 27, 2002
Patricia Burchat, Stanford

34. 3-body branching fractions
Belle BABAR
p+ p+ p <15
K+p+ p ± 5.8 ± ± 4.7 ± 4.9
K+ K+ K ± 3.7 ± ± 2.0 ± 1.7
K+ K ± p ± no signal no signal
DPF, May 27, 2002
Patricia Burchat, Stanford

35. B  D(CP)K decays: why are they interesting?
Potential for measuring CKM angle g: b u c s B- D0 K- b u c s B- D0 K-
Determine g through amplitude relationships (up to discrete ambiguities): Gronau & Wiler; Dunietz (1991).
DPF, May 27, 2002
Patricia Burchat, Stanford

36. Patricia Burchat, Stanford
CP charge asymmetries in B  D(CP)K from Belle and BABAR:
B-D p
B-D K
Afl = ± 0.096
Dfl
Afl = ± (stat)
ACP+ = ± 0.26
DCP+
ACP+ = ± 0.27
ACP- = ± 0.24
DCP-
  Flavor Session V, G. Mancinelli
DE (GeV)
DPF, May 27, 2002
Patricia Burchat, Stanford

37. Many highlights in hadronic B decays not covered here . . .
B  D(*)+ p-: potential for measuring sin(2b+g); See CLEO analysis of strong phase between DI = 1/2 and 3/2.
Analysis of partially-reconstructed hadronic decays.
B  Ds(*)+ p- (Vub suppressed); help in interpretation of B  D(*)+ p
Color-suppressed B decays (e.g., B  D(*)0X0)
B  D(*)D(*) (BF, ang analysis)
B  baryons
  Flavor Session V, T. Pedlar
  Flavor Session V, M. Krishnamurthy, VI: C.S.Kim; CKM/CP Sesion III: Y. Zheng
  Flavor Session V, T. Orimoto
  FP Session I: Fang Fang (Belle); Cheng (theory)
DPF, May 27, 2002
Patricia Burchat, Stanford

38. Patricia Burchat, Stanford
Summary
With the rapidly increasing data samples from the B Factories, many new decay modes are becoming available for
time-dependent CP asymmetry measurements (sensitive to b and a);
direct CP asymmetry measurements (sensitive to a and g);
branching fraction and resonant substructure measurements that are crucial for the interpretation of many of the CP asymmetries.
b is in agreement with SM predictions; too early to interpret results on a.
The summer conferences and the Fall papers will continue to bring many interesting new results to interpret as the B Factory experiments “catch up” on their analyses.
DPF, May 27, 2002
Patricia Burchat, Stanford