5 jan 03s. bailey / babar : b decays to measure gamma1 b decays to measure stephen bailey...
DESCRIPTION
5 Jan 03S. Bailey / BaBar : B decays to Measure gamma3 Many Methods – none are easy Amplitude relationships with B - -> D 0 CP K - and friends “Squashed” amplitude triangles: BR(B - D 0 bar K - ) D ( * ) - +, +, a 1 +, … Cabibbo suppressed B 0 -> D ( * )+ - Use B 0 -> D s ( * ) and SU(3) to estimate B 0 -> D ( * )+ - Progress on both full and partial reconstruction techniques B -> , K , KK Several options with various theoretical trade-offsTRANSCRIPT
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 1
B Decays to Measure
Stephen BaileyHarvard University
for the BaBar Collaboration
PASCOS 2003Mumbai, India
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 2
Background
CP violation with B0 -> KS (sin2) is well established
Agrees with Standard Model Now we need to
overconstrain the unitarity triangle to check consistency
= arg(VudVub* / Vcd Vcb*) = -arg(Vub)
in standard phase convention
Results from BaBar at PEP-II: e+e- -> (4S) -> BBbar
~88 million BBbar pairs
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 3
Many Methods – none are easy
Amplitude relationships with B- -> D0CP K- and friends
“Squashed” amplitude triangles: BR(B- D0
bar K-) << BR(B- D0 K-) Interference involving doubly Cabibbo suppressed D0 decays
sin(2+) with B0 -> D(*)- +, +, a1+, …
Cabibbo suppressed B0 -> D(*)+ - Use B0 -> Ds
(*) and SU(3) to estimate B0 -> D(*)+ -
Progress on both full and partial reconstruction techniques
B -> , K, KK Several options with various theoretical trade-offs
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 4
B D0CP K and friends
D0CP = (D0 D0
bar) / 2 : CP even or odd decays, e.g. K+K-
Measure sides of amplitude triangles to determine 2 A(B- -> D0
CPK-) = A(B- -> D0K-) A(B- -> D0barK-)
2 A(B- -> D0CPK-) = A(B- -> D0K-) |A(B- -> D0
barK-)| e-iei
Sensitivity to depends on r = |A(B- -> D0barK-)| / |A(B- -> D0K-)|
A(B+ -> D0 K+) 2 A(B- -> D0CP K-)
A(B- -> D0bar K-)
A(B+ -> D0bar K+) = A(B- -> D0 K-)
2 A(B+ -> D0CP K+)
2
D0bar
b u
s u
u c
K- B-
Vub ~ e-i
strong phase
weak phase
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 5
B- D0 K-
Use D0 -> K-+, K-+-+, K-+0
2
A(B+ -> D0 K+) 2 A(B- -> D0CP K-)
A(B- -> D0bar K-)
A(B+ -> D0bar K+) = A(B- -> D0 K-)
2 A(B+ -> D0CP K+)
hep-ex/0207087
B -> D0
with kaon ID cutand 3 mES cut
B -> D0K
D0 -> K only
D0 -> K onlyPDG: BF(B- -> D0-) = (5.30.5)x10-3
(81M BBbar pairs; 75 fb-1)
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 6
B D0CP K
B D0[K+K] K 36.8 8.4 4.0 signal events
B D0[] K Upcoming backgrounds from B -> K
2
A(B+ -> D0 K+) 2 A(B- -> D0CP K-)
A(B- -> D0bar K-)
A(B+ -> D0bar K+) = A(B- -> D0 K-)
2 A(B+ -> D0CP K+)
hep-ex/0207087
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 7
Direct CP asymmetry from D0CP states:
2.0~ |)(||)(|
0
0
KDBAKDBAr
2
A(B+ -> D0 K+) 2 A(B- -> D0CP K-)
A(B- -> D0bar K-)
A(B+ -> D0bar K+) = A(B- -> D0 K-)
2 A(B+ -> D0CP K+)
200
00
coscos21sinsin2
)()()()(
rrr
KDBBFKDBBFKDBBFKDBBFA
CPCP
CPCPCP
strong phaseweak phase
B D0CP K and friends
ACP = 0.17 0.23 +0.09/-0.07
hep-ex/0207087
(81M BBbar pairs; 75 fb-1)
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 8
B- D0bar K-
Hard: BR(B- D0bar K-) << BR(B- D0 K-)
Interference from doubly Cabibbo suppressed D0 decays: B- -> D0
barK- (small) --> K+- (big)
B- -> D0 K- (big) --> K+- (small)
Plan: Measure B- -> D0
(bar) K-
w/ D0bar -> K+-, K+-+-, K+-0
Measure Multiple D0CP modes
See Gronau, hep-ph/02112822
A(B+ -> D0 K+) 2 A(B- -> D0CP K-)
A(B- -> D0bar K-)
A(B+ -> D0bar K+) = A(B- -> D0 K-)
2 A(B+ -> D0CP K+)
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 9
B D0CP K Summary
B- -> D0 K- measured R(B -> D0K/D0) = (8.31 0.35 0.20)%
D0CP -> K+K- : initial results available
Direct Asymmetry: ACP = 0.17 0.23 +0.09/-0.07 More modes (e.g. D0
CP -> ) in progress More data coming too…
Cabibbo suppressed modesin progress…
2
A(B+ -> D0 K+) 2 A(B- -> D0CP K-)
A(B- -> D0bar K-)
A(B+ -> D0bar K+) = A(B- -> D0 K-)
2 A(B+ -> D0CP K+)
hep-ex/0207087
(81M BBbar pairs; 75 fb-1)
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 10
sin(2 + ) with B0 D(*)
Both D(*)+- and D(*)-+ from B0 and B0
bar Interference -> CP violation B0 B0
bar mixing : e-i2
b -> u : Vub ~ e-i
Large difference in branching fractions: BFfavored(B0 -> D(*)-+) ~ 3x10-3
BFsuppressed(B0 -> D(*)+-) ~ 10-6
Small CP violating effect expected (2%)
Measure one weak phase (2+) anda strong phase () for each mode
D(*)- b d
c d
d u
+
B0
Cabibbo Favored
D(*)+ b d
u d
d c
- B0
Cabibbo Suppressed
in standard phase convention
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 11
sin(2 + ) : B0 Ds(*)
|(*)| = ~ 0.02
Use B0 -> Ds(*)+- to estimate
|A(B0 -> D(*)+-)| via SU(3) symmetry Introduces theoretical uncertainty
B0 -> Ds+-
Use Ds+ -> +, KsK+, K*barK+
21.4 5.1 signal events BF(B0 -> Ds
+-) = (3.2 0.9 1.0) x 10-5
84M BBbar pairs; 78 fb-1
BF(B0 -> Ds*+-) < 4.1 x 10-5 [90% CL]
b d
u d
d(s) c
- B0
D(s)(*)+
hep-ex/0207053
|A(B0bar -> D(*)-+)|
|A(B0 -> D(*)-+)|
too small to measure w/ current data
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 12
sin(2 + ) : Fully reconstructed B0 D(*)
Fully reconstruct both D and D* Time evolution for each state f
)](sin)(cos1[4
)(/
tmStmCetf dfdf
t
2
2
||1||1
f
ffC
2||1Im2
f
ffS
f
ff A
Apq
arg(D+-) = -(2++
arg(D-+) = -(2+-
Four ’s include one weak phase (2+) and two strong phases ((*))
arg(D*+-) = -(2++*
arg(D*-+) = -(2+-*
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 13
sin(2 + ) : Fully reconstructed B0 D(*)
We have thousands of fully reconstructed B0 -> D andB0 -> D*
The sin(2+) fitter is being studied
The results aren’t unblinded yet
mES from B0 -> D-+ with 5.2 fb-1
very clean signal now we have almost 20x more
data
5.2 fb-1
B0 D-+
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 14
sin(2 + ) : Partially reconstructed B0 D*
Another method: Partial D* reconstruction Reconstruct low momentum
in D* -> D, but not rest of D More signal events,
but also more background N(tagged) > 40 000 events
in full dataset
20.3 fb-1 : only a fraction of the current data, but shows approximate S/B
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 15
sin(2 + ) : Partially reconstructed B0 D*
Unreconstructed D daughters could affect tag sidevertex position measurement
Validate partial reco. method with a lifetime measurement (B0) = (1.510 0.040 0.041) ps (with 20.7 fb-1) cf PDG (B0) = (1.548 + 0.032) ps hep-ex/0212012 submitted to PRD
Proceeding with sin(2+) fit, results not unblinded yet…
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 16
B0 , K, KK
Amplitude relationships with B -> , K, KKmay also measure or constrain
Theoretical interpretation is complicated: Penguins Rescattering contributions SU(3) symmetry breaking etc. For a recent brief review, see Fleischer, hep-ph/0207324
For now we’ll quote branching fractions (BF) and Asymmetries (A) and let you plug the numbers into your favorite theory…
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 17
B0 , K, KK
Mode BF x 10-6 AB0 -> 00 < 3.6 [90% CL]
B0 -> +- 4.7 0.6 0.2 S= 0.02 0.34 ; C= -0.30 0.25
B0 -> K00 10.4 1.5 0.8 0.03 0.36 0.09B0 -> K+- 17.9 0.9 0.7 -0.102 0.050 0.016B0 -> K+K- < 0.6 [90% CL]
B+ -> +0 5.5 +1.0-0.9 0.6 -0.03 +0.18
-0.17 0.02B+ -> K+0 12.8 +1.2
-1.1 1.0 -0.09 0.09 0.01B+ -> K0+ 17.5 +1.8
-1.7 1.3 -0.17 0.10 0.02B+ -> K+K0
bar < 1.3 [90% CL]
hep-ex/0207055hex-ex/0207065hex-ex/0207063hep-ex/0206053
(81 fb-1 except K0+, K+K0bar: 54 fb-1)
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 18
Many More Modes
Exploring many other modes which could measure or 2+: B -> D(*)K(*)
B -> D(*)KS B -> D KS B -> D(*) K(*) Dalitz analysis of B -> etc.
5 Jan 03 S. Bailey / BaBar : B decays to Measure gamma 19
Outlook
The Good News: We’re making progress B- -> D0
CP K- Several sides of amplitude triangles measured ACP = 0.17 0.23 +0.09/-0.07
sin(2+) with B0 -> D(*) Decay modes reconstructed Lifetime measurement checks method sin(2+) fit results in progress
B0 -> , K, KK Many branching fractions measured Need theoretical input for interpretation
Final story will likely involve: B factory measurements of many decay modes Hadronic accelerator results with Bs decays Theoretical input