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5 Jan 0 3 S. Bailey / BaBar : B decays to Measure gamma 1 B Decays to Measure Stephen Bailey Harvard University for the BaBar Collaboration PASCOS 2003 Mumbai, India

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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-offs

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Page 1: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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

Page 2: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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

Page 3: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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

Page 4: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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

Page 5: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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)

Page 6: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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

Page 7: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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)

Page 8: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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+)

Page 9: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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)

Page 10: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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

Page 11: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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

Page 12: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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+-*

Page 13: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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-+

Page 14: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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

Page 15: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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…

Page 16: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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…

Page 17: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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)

Page 18: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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.

Page 19: 5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard…

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