B Decays to Measure g

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B Decays to Measure g

• Stephen Bailey
• Harvard University
• for the BaBar Collaboration
• PASCOS 2003
• Mumbai, India

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Background

• CP violation with B0 -gt yKS (sin2b) is well
  established
• Agrees with Standard Model
• Now we need to overconstrain the unitarity
  triangle to check consistency
• g arg(VudVub / Vcd Vcb)
• g -arg(Vub)in standard phase convention
• Results from BaBar at PEP-II ee- -gt U(4S) -gt
  BBbar
• 88 million BBbar pairs

h
g
r
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Many Methods none are easy

• Amplitude relationships with B- -gt D0CP K- and
  friends
• Squashed amplitude triangles BR(B- ? D0bar
  K-) ltlt BR(B- ? D0 K-)
• Interference involving doubly Cabibbo suppressed
  D0 decays
• sin(2bg) with B0 -gt D()- p, r, a1,
• Cabibbo suppressed B0 -gt D() p-
• Use B0 -gt Ds() p and SU(3) to estimate B0 -gt
  D() p-
• Progress on both full and partial reconstruction
  techniques
• B -gt pp, Kp, KK
• Several options with various theoretical
  trade-offs

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B? ? D0CP K? and friends

• D0CP (D0 D0bar) / Ö2 CP even or odd
  decays, e.g. KK-
• Measure sides of amplitude triangles to determine
  g
• Ö2 A(B- -gt D0CPK-) A(B- -gt D0K-) A(B- -gt
  D0barK-)
• Ö2 A(B- -gt D0CPK-) A(B- -gt D0K-) A(B- -gt
  D0barK-) e-igeid
• Sensitivity to g depends on r A(B- -gt
  D0barK-) / A(B- -gt D0K-)

strong phase
weak phase
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B- ? D0 K-
hep-ex/0207087
D0 -gt Kp only

• Use D0 -gt K-p, K-pp-p, K-pp0

B -gt D0p
B -gt D0K
(81M BBbar pairs 75 fb-1)
PDG BF(B- -gt D0p-) (5.30.5)x10-3
D0 -gt Kp only
with kaon ID cut and 3s mES cut
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B? ? D0CP K?
hep-ex/0207087

• B? ? D0KK- K?
• 36.8 8.4 4.0 signal events

• B? ? D0pp- K?
• Upcoming
• backgrounds from B -gt ppK

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B? ? D0CP K? and friends
hep-ex/0207087

• Direct CP asymmetry from D0CP states

• ACP 0.17 0.23 0.09/-0.07

(81M BBbar pairs 75 fb-1)
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B- ? D0bar K-

• Hard BR(B- ? D0bar K-) ltlt BR(B- ? D0 K-)
• Interference from doubly Cabibbo suppressed D0
  decays
• B- -gt D0barK- (small) --gt Kp- (big)
• B- -gt D0 K- (big) --gt Kp- (small)
• Plan
• Measure B- -gt D0(bar) K-w/ D0bar -gt Kp-,
  Kp-pp-, Kp-p0
• Measure Multiple D0CP modes
• See Gronau, hep-ph/0211282

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B? ? D0CP K? Summary
hep-ex/0207087

• B- -gt D0 K- measured
• R(B -gt D0K/D0p) (8.31 0.35 0.20)
• D0CP -gt KK- initial results available
• Direct Asymmetry ACP 0.17 0.23 0.09/-0.07
• More modes (e.g. D0CP -gt pp) in progress
• More data coming too
• Cabibbo suppressed modesin progress

(81M BBbar pairs 75 fb-1)
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sin(2b g) with B0 ? D()p

• Both D()p- and D()-p from B0 and B0bar
• Interference -gt CP violation
• B0 B0bar mixing e-i2b
• b -gt u Vub e-ig
• Large difference in branching fractions
• BFfavored(B0 -gt D()-p) 3x10-3
• BFsuppressed(B0 -gt D()p-) 10-6
• Small CP violating effect expected (2)
• Measure one weak phase (2bg) anda strong phase
  (d) for each mode

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sin(2b g) B0 ? Ds()p
hep-ex/0207053
too small to measure w/ current data

• l() 0.02
• Use B0 -gt Ds()p- to estimateA(B0 -gt D()p-)
  via SU(3) symmetry
• Introduces theoretical uncertainty
• B0 -gt Dsp-
• Use Ds -gt fp, KsK, KbarK
• 21.4 5.1 signal events
• BF(B0 -gt Dsp-) (3.2 0.9 1.0) x 10-5
• 84M BBbar pairs 78 fb-1
• BF(B0 -gt Dsp-) lt 4.1 x 10-5 90 CL

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sin(2b g) Fully reconstructed B0 ? D()p

• Fully reconstruct both Dp and Dp
• Time evolution for each state f

• Four ls include one weak phase (2bg) and two
  strong phases (d())

arg(lDp-) -(2bgd) arg(lD-p) -(2bg-d)
arg(lDp-) -(2bgd) arg(lD-p) -(2bg-d)
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sin(2b g) Fully reconstructed B0 ? D()p

• We have thousands of fully reconstructed B0 -gt Dp
  andB0 -gt Dp
• The sin(2bg) fitter is being studied
• The results arent unblinded yet
• mES from B0 -gt D-p with 5.2 fb-1
• very clean signal
• now we have almost 20x more data

5.2 fb-1 B0 ? D-p
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sin(2b g) Partially reconstructed B0 ? Dp

• Another method Partial D reconstruction
• Reconstruct low momentum p in D -gt Dp, but not
  rest of D
• More signal events,but also more background
• N(tagged) gt 40 000 eventsin full dataset

20.3 fb-1 only a fraction of the current data,
but shows approximate S/B
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sin(2b g) Partially reconstructed B0 ? Dp

• Unreconstructed D daughters could affect tag
  sidevertex position measurement
• Validate partial reco. method with a lifetime
  measurement
• t(B0) (1.510 0.040 0.041) ps (with 20.7
  fb-1)
• cf PDG t(B0) (1.548 0.032) ps
• hep-ex/0212012 submitted to PRD
• Proceeding with sin(2bg) fit, results not
  unblinded yet

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B0 ? pp, Kp, KK

• Amplitude relationships with B -gt pp, Kp, KKmay
  also measure or constrain g
• Theoretical interpretation is complicated
• Penguins
• Rescattering contributions
• SU(3) symmetry breaking
• etc.
• For a recent brief review, see Fleischer,
  hep-ph/0207324
• For now well quote branching fractions (BF) and
  Asymmetries (A) and let you plug the numbers into
  your favorite theory

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B0 ? pp, Kp, KK
hep-ex/0207055 hex-ex/0207065 hex-ex/0207063 hep-e
x/0206053
(81 fb-1 except K0p, KK0bar 54 fb-1)
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Many More Modes

• Exploring many other modes which could measure g
  or 2bg
• B -gt D()K()
• B -gt D()KS
• B -gt D KS p
• B -gt D() K() p
• Dalitz analysis of B -gt ppp
• etc.

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Outlook

• The Good News Were making progress
• B- -gt D0CP K-
• Several sides of amplitude triangles measured
• ACP 0.17 0.23 0.09/-0.07
• sin(2bg) with B0 -gt D()p
• Decay modes reconstructed
• Lifetime measurement checks method
• sin(2bg) fit results in progress
• B0 -gt pp, Kp, 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