Exclusive Semileptonic bu Decays at CLEO

1
Exclusive Semileptonic b?u?? Decays at CLEO

• Sheldon Stone
• Syracuse University

2
Introduction

• Improved measurements of Bo? p-?? r-??
  branching ratios and q2 dependences
• Measurement of B? ??? evidence for B?
  ???
• Analysis Uses Neutrino Reconstruction
• Extension of CLEO II/II.5 Analysis (PRD 68,
  072003) by adding CLEO III data, 60 more data,
  total of 14 fb-1

3
Formalism in Pseudoscalar Decay

• q2(pBm-pPm)2, kP is the P momentum in the B rest
  frame

4
Formalism in Vector Decay

• qWL is the ? between the ? direction in the W
  rest frame the W direction in the B rest frame
• q2(pBm-pVm)2, kV is the V momentum in the B rest
  frame

5
Neutrino Reconstruction
pn Resolution

• Estimate n 4-vector using pmiss
  ? pCM-pvisible Emiss ?
  ECM-Evisible
• Require in general net charge
  of 0, (in 0- modes also use 1)
• Require MM2 0
  (MM2/2Emiss lt0.5 GeV)
• Require Spherical events
• Identify e or m with plgt1 GeV/c (reject events
  with gt1 lepton)
• Form DEEhadEl-En-Ebeam
• Mhln2Ebeam2-(phadplpn)2

s0.1 GeV/c
p? GeV/c
6
Measurement Technique
B????

• Vector state sensitive to
  cosqWL
• Binning
• B???? in q2 cos?WL
  bins drastically reduces
• model dependence of
  branching ratio determination
• B???? in q2 bins
• B???? in all phase space
• B?? ?? in all phase space

Ratio Coslt0 / Cosgt0
Ball04, Mel, UKQCD, ISGW2
q2 GeV2
7
Expectations from Simulation
Backgrounds peak here
Signal peaks here

• Use binned log likelihood method simultaneously
  in all modes and bins
• Use isospin constraints efficiency matrix

8
Fit Components
Signals
Backgrounds
Data
Events/7.5MeV/c2
Mhlv GeV/c2
9
Results from Fit (Summed)

• Mhln Distribution -0.15lt ??lt0.25 GeV
• ?? Distribution 5.265lt Mhln lt 5.28 GeV

p, po
r, ro, wo
h
h?
Events/7.5MeV/c2
Mhlv GeV/c2
Mhlv GeV/c2
Mhlv GeV/c2
Mhlv GeV/c2
Events/100MeV/c2
?? GeV
?? GeV
?? GeV
?? GeV
10
Systematic Errors
Largest Source Of Systematic Uncertainty
11
Results

• B(B????)
• (1.37?0.15?0.12?0.01)?10-4

B(B?r??) (2.93?0.37?0.39?0.04)?10-4
cos?wlgt0
cos?wllt0
B?10-4/GeV2
B?10-4/GeV2
HPQCD 04 Prediction
Ball 04 Prediction
q2 GeV2
q2 GeV2
B(B????) (0.44?0.23?0.11?0.00)x10-4,
lt1.01?10-4 _at_90 cl B(B?????)
(2.66?0.80?0.57?0.04)x10-4, 3s effect ?G(B?????)
/G(B????)gt2.5 _at_90 cl Theory without color
singlet has B(B????) 0.4x10-4, B(B?????)
0.2x10-4, inconsistent with data
12
B(B????)

• B????
• Comparisons
• Competitive with B
• factories due to
• higher efficiencies at
• symmetric machine

13
B???? Comparisons
B(B????)
14
Measurement of Vub

• We use our measurement for B???? for q2 gt 16
  GeV2
• And recent results from unquenched lattice
  calculation HPQCD collaboration
  (Gulez, et al, PRD 73, 074502, 2006).

CLEO (2006)
BABAR (2006)
BELLE (2006)
Note that the theoretical error dominates
15
Conclusions
Preliminary

• Using n reconstruction CLEO measured Branching
  ratios for B?(?, ?, ?)?n an upper limit for
  B???n
• B(B????) (1.37 ? 0.15?0.12 ?0.01)?10-4
• B(B????) (2.93 ? 0.37 ? 0.39? 0.04) ? 10-4
• B(B? ???) (2.66 ? 0.80 ? 0.57 ? 0.04) ? 10-4
  3 s evidence for
• B(B????) lt 1.01?10-4 _at_ 90 C.L.
• Extracted Vub using ? q2gt16 GeV2 and HPQCD
  prediction

16
A Tribute to Bernie Gittelman

• 1932-Nov. 25, 2006
• A hero of
• flavor
• physics
• Pioneered e- storage rings at SLAC
• First to measure B semileptonic decays
• Led CLEO II project