Physics on the Recoil:
Exclusive Charmless Semileptonic Decays
Daniele del Re
University of California San Diego
Vub Inclusive Analysis: Potential
Bpln,
Brln,
Bwln,
Ba1ln,
...
• 170 BXuln events on data after all cuts for MX<1.55GeV
• exclusive channels can be studied with ~same technique
• large potential to perform exclusive Vub analyses
04/10/03
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Available Sample
NSL=32000 (NBXln)
events on data
(20.5K B+,11.5K B0)
82fb-1
N B hlv  N SL
17 B+p0ln
25 B+r0ln
25 B+wln
15 B+a1ln
19 B0p+ln
27 B0r+ln
17 B0a1ln
BR( B  hlv)
BR( B  Xlv)
Events in 82fb-1 with
• Nlepton>0
• Pcms>1 GeV
assuming DECAY.dec branching ratios
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Characteristics of the Exclusive Modes
Mass
Width
BR
B+p0ln
135 MeV
-
90*10-6
B+r0ln
770 MeV
150 MeV
130*10-6
B+wln
782 MeV
8 MeV
165*10-6
B+a1ln
1230 MeV
400 MeV?
102*10-6
-
-
616*10-6
B0p+ln
139.6 MeV
-
180*10-6
B0r+ln
771 MeV
150 MeV
260*10-6
B0a1ln
1260 MeV
400 MeV?
130*10-6
B0b1ln
1235 MeV
140 MeV
82*10-6
-
-
616*10-6
B+Xln(nres)
B0Xln(nres)
Since the main background is the one from bcln decays,
high and wide mass resonances will be less pure
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Sample Composition
Applying basic cuts:
Fitted Mx
B+
410fb-1
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•one fully reconstructed B+- / B0
•one and only one lepton with p*>1GeV
•charge conservation (Qreco+Qrecoil=0)
•charge correlation (lepton + Breco charge = 0)
•no kaons in the recoil (nK+ + nKs = 0)
•-1GeV2 < mm2 < 1GeV2
Fitted Mx
B0
470fb-1
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B+  p 0 l + n
F. Gallo
B+p0ln (preliminary) selection:
•
•
•
•
Basic cuts (previous slides)
mm2 < 0.4 GeV2
Nchg in X = 0
0 < Mxhadfit < 0.2 GeV
Fitted Mx
410fb-1
Main issue:
recover merged p0!
Mx(GeV)
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In 120 fb-1 (assuming ~50% recovering):
Nsig = ~10, Nbkg ~0
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B+  r 0 l + n
D. del Re
B+r0ln (preliminary) selection:
•
•
•
•
Basic cuts (previous slides)
mm2 < 0.5 GeV2
Nchg in X = 2
Mxhad – Mxhadneu < 0.1 (w veto)
Fitted Mx
250fb-1
In 120 fb-1:
Nsig = ~13, Nbkg ~4
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B+  w l + n
S. Pisano
B+wln (preliminary) selection:
•
•
•
•
Basic cuts (previous slides)
mm2 < 0.6 GeV2
Nchg in X = 2
Mxhad – Mxhadneu > 0.15 (r veto)
Fitted Mx
410fb-1
In 120 fb-1:
Nsig = ~10, Nbkg ~6
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B0  p - l + n
M. Kocian
Here we are trying to relax the basic
cuts.
For instance we are studying the
possibility to remove the lepton
PID .
Fitted Mx
470fb-1
In 120 fb-1:
Nsig = ~15, Nbkg ~1
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B0 (r,a,b)- l+ n
L. Li Gioi
(preliminary) selection:
• Basic cuts (previous slides)
• mm2 < 0.5 GeV2
• and…
120fb-1
04/10/03
S
Btot
B0r+ln
15
13
B0a1ln
3
10
B0b
2
25
1ln
One chg track in X
Three chg tracks in X
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Which Sensitivity by July?
Recoil expected 120fb-1(*)
Recoil expected 120fb-1 (*)
Recoil expected 120fb-1(*)
B+p0ln (x2)
Recoil expected 120fb-1(*)
PDG
(0.9±0.2±0.2)x2
Recoil expected 120fb-1 (*)
(*) = only statistical error
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q2 Spectrum
q2 spectrum for B0p+l-n
models
reconstructed
120 fb-1
q2(GeV2)
Not enough statistics (120 fb-1) to discriminate among models
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Conclusions
• Exclusive charmless semileptonic B decays can be studied on the
recoil already with 120 fb-1
• Few events expected but very low background and crossfeed
• Exp. systematic uncertainties are ~one order of magnitude lower
than statistical ones
• First results could be ready for summer conferences
• Same technique is very promising also for charm semileptonic
decays (B(D,D*,D**)ln)
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People involved and organization
•
•
•
•
•
B+p0ln: Francesco Gallo
B+wln: Silvia Pisano
B+r0ln: DdR
B0 p+ln : Martin Kocian
B0 r+ln : Luigi Li Gioi
and R. Faccini, V. Luth, U. Langenegger, F. Simonetto
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04/10/03
Meetings are on Thursdays (biweekly based) 8:30 a.m. PST.
Next one is 04/17
If you want to join let me know (also our EXCL-RECOIL mailing list)
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