Measurement of the Branching Fraction of BhcK with 80 fb1

1
Measurement of the Branching Fraction ofB?hcK
with 80 fb-1

• Stefania Ricciardi
• For the hc group
• N.Barlow, P.Clark,
• F.Jackson, G. Hamel de Monchenault,
• C.Marker, W.Kozanecki

2
Outline
The analysis is extensively documented in BAD579

• This a report on the last analysis issues since
  ELBA
• Data Yields with individual and simultaneous fits
  
• Self-combinatorial and efficiency on MC
• Progresses in the hc? hpp mode
• And final-ly
• RESULTS!

Final results would need final new Ks
efficiency corrections
3
The Essentials

• Analysis based on Run1 and Run2 full data set
• L 79.4/fb processed with release-10
• fully reconstructed B ? hc K with
• 1. hc ? KsKp
• 2. hc ? KK-p0
• 3. hc ? 2(KK-)
• 4. hc ? ff
• Signal and Background Yields extracted with a
• 2D ML to Mes-mX
• Event weights to account for (small)
• efficiency variations across the DALITZ for the
  KKp modes.

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Mes-mX fits on DATA
B ? hc K hc ? Ks0Kp

• Fits have been performed in 2 ways
• individually to each mode
• simultaneously to charged an neutral B with
• common resolution and fraction of J/y (possible
  to float Ghc)

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hc width
Fixed value G(hc)33.8 ? 2.6 MeV BaBar
Measurement (submitted to PRL)
Fitted value G(hc)39.7 ? 6.5 MeV
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Final Yields
Quoting individual fits for central values and
errors
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Fit Systematics
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Signal MC fits
Non-negligible fraction of events described by an
Argus function, aka self-combinatorial, seen in
all modes. Varying from 8.5 in the KKp0 mode to
0.5 in the ff mode
KKp0Ks
KKp0K
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Determination of the Self-Combinatorial
Efficiency studies on full MC require high
statistics. 3 ways of computing this efficiency
1. 2D (mES-mX) fit to signal MC 2. 2D fit to
high statistics signal MC mixed with a fraction
of Toy combinatorial and peaking background in
proportions found in data 3. 500 experiments - 2D
fit to expected number of full signal MC events
(randomly chosen) mixed with Toy background
Methods 2-3 check whether the fraction of events
identified as signal varies in presence of
background and it is used to quote the
systematic uncertainty (larger of the differences
with Method 1)
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Self-combinatorial Efficiency Correction
Fraction of events correctly identified as signal
by the mES-MX fit
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Efficiency

• PID-killed, g-killed SP4 (various HV periods
  reweighed with data lumi)
• Efficiency is further corrected for
• tracking (standard recipe)
• Ks (standard old recipe, 6 /Ks)
• etac width (33.8 MeV gg?hc / 27.0 MeV SP4
  generated)
• lower cutoff in etac MC generation , m(hc) -150
  MeV ( lt 1)
• K PID B only ( 4.7)
• self-combinatorial

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Efficiency relative Systematic Errors ()
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RESULTS

• BF(B ? hc K)x BF(hc?X) ______________

hc
e N(BB) Pi BFisecondaries
Assuming equal admixture of charged and neutral B
in Y(4S) decays
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BF Products

NOW (10-6)
Moriond2002(Run1)

stat syst stat syst BF(B
? hc K) BF(hc? K0Kp) 42.8 3.4 4.3
52.8 7.9 7.3 BF(B0 ? hc K0) BF(hc?
K0Kp) 34.2 5.5 4.1 36.8
11.6 6.0 BF(B ? hc K) BF(hc? KKp)
12.1 1.6 1.5 15.5 3.6 2.5 BF(B0 ?
hc K0) BF(hc? KKp) 9.9 2.5 1.1
11.3 5.1 2.4 BF(B ? hc K) BF(hc? 4K)
1.9 0.6 0.4 lt5.6 (90
CL) BF(B0 ? hc K0) BF(hc? 4K) 0.8
0.8 0.3 lt2.3 (90 CL)

lt2.0 (90 CL) BF(B ? hc K) BF(hc? ff)
4.7 1.2 0.5 - BF(B0 ? hc
K0) BF(hc? ff) 2.2 1.3 1.5
-
lt3.7 (90CL)
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BF Ratios
KKp modes related by isospin simmetry expected
ratio 0.25 BF(hc? KKp0)/ BF(hc? K0Kp) 0.28?
0.04 ?0.03 (charged B) BF(hc? KKp0)/ BF(hc?
K0Kp) 0.29? 0.09 ?0.03 (neutral B) We
therefore combine these two modes to quote
averages taking into Account correlation in the
systematic error components Most of the
systematics cancel in the ratio neutral over
charged Except those affecting the fast kaons,
self-combinatorial and uncorrelated components in
the fit systematics KKp0 BF(B0 ? hc K0)/ BF(B
? hc K) 0.82 ? 0.23 ? 0.08 K0Kp BF(B0 ?
hc K0)/ BF(B ? hc K) 0.80 ? 0.14 ? 0.07 KKp
BF(B0 ? hc K0)/ BF(B ? hc K) 0.81? 0.12 ?
0.06 Our Run1 result BF(B0 ? hc K0)/ BF(B ?
hc K) 0.71 ? 0.20 ? 0.08
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BF(hc?4K)
Since the PDG results for the individual hc
branching fractions have large errors, we express
our 4K and ff results in the charged Modes in
terms of ratios to the best measured BF(hc? KKp)
BF(hc? 4K) /BF(hc? KKp) (2.9 ? 0.9 ? 0.6)
10-2 BF(hc? ff) /BF(hc? KKp) (7.1 ? 1.8 ? 0.7)
10-2
Using the PDG value for BF(hc? KKp) 0.055
?0.017 BF(hc? 4K) (1.6 ? 0.5 ? 0.3 ? 0.5)
10-3 BF(hc? ff) (3.9 ? 1.0 ? 0.4 ? 1.2) 10-3
BF (hc ?4K) (2.1 1.2) 10-2 PDG (ARGUS
measurement with a ff veto)
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Non-resonant 4K/ff Separation
The J/psi component is only among non-resonant
4K candidates (no J/y decay into identical spin1
bosons)
Inside ff signal box M(KK-)-M(f) lt 14MeV
Outside ff signal box M(KK-)-M(f) gt
14MeV non-resonant region
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4K not from ff decays
J/y compatible with PDG BF(J/y?4K)1.43?0.7
10-3 Assuming same efficiency as hc We measure
BF(J/y?4K) (0.7?0.3) 10-3
hc events inside ff box 15.4 4.8 hc
events outside ff box 13.6 7.1 Almost half
of the candidates are in the ff region BF (hc
?4K) (2.1 1.2) 10-3 PDG (ARGUS measurement
with a ff veto) Our measurement excludes PDG at
very high CL
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BF(B?hcK)
Using the PDG value for BF(hc? KKp) 0.055
?0.017 From the average BF products in the KKp
modes we obtain BF(B?hcK) (1.19 ? 0.08 ? 0.10
? 0.37) 10-3 BF(B0?hcK0) (0.97 ? 0.13 ? 0.10 ?
0.30) 10-3 BaBar Run-1(20/fb) same
modes BF(B?hcK) (1.50 ? 0.19 ? 0.15 ? 0.46)
10-3 BF(B0?hcK0) (1.06 ? 0.28 ? 0.11 ? 0.33)
10-3 CLEO (9.13/fb) KsKp ff BF(B?hcK) (0.69
? 0.26 ? 0.08 ? 0.20) 10-3 BF(B0?hcK0) (1.09 ?
0.55 ? 0.12 ? 0.31) 10-3 Belle (29.1/fb) same
modes BF(B?hcK) (1.25 ? 0.14 0.11/-0.12 ?
0.38) 10-3 BF(B0?hcK0) (1.23 ? 0.23
0.12/-0.16 ? 0.38) 10-3
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Preliminary B??c(???-) K results

• ?c ????-
• Has been unblinded
• Large combinatorial bkg and also peaking
  background
• Next steps
• Combinatorial bkg
• Looking at ? mass side bands
• Peaking bkg
• Study generic MC
• Other bkg
• Looking Dalitz plot (???-)

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Plans

• This result is NOT going to summer conferences
• We wish to submit a journal publication ASAP.
• For hc?hpp. nice progresses have been made
  towards a finalization of
• selection criteria. It can be included in the
  publication
• IF it is ready by the time when the
  ReviewCommittee will approve
• the analysis on the mature modes.
• What is missing?
• Documentation BAD579 is under internal
  (etac-group) review
• Aiming to upload first version for AWG reading
  before the end of next week.
• A few missing pieces to final numbers
• - new Ks corrections
• correct a small mistake in the production of
  KKpi0 ascii-files
• (lower cut value for g 20 MeV higher than
  optimal, 1 effect)