Post on 14-Dec-2015
Physics on the Recoil: Exclusive Charmless Semileptonic Decays
Physics on the Recoil: Exclusive Charmless Semileptonic Decays
Daniele del ReUniversity of California San Diego
04/10/03 Daniele del Re Excl B DecaysDaniele del Re Excl B Decays 2
Vub Inclusive Analysis: PotentialVub Inclusive Analysis: Potential
BlBlBlBal
• 170 BXul 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 Daniele del Re Excl B DecaysDaniele del Re Excl B Decays 3
assuming DECAY.dec branching ratios
NSL=32000 (NBXl events on data(20.5K B+,11.5K B0)
17 B+l25 B+l25 B+l15 B+a1l
19 B0l27 B0l17 B0a1l
Events in 82fb-1 with• Nlepton>0• Pcms>1 GeV
82fb-1
Available Sample Available Sample
( )
( )B hlv SL
BR B hlvN N
BR B Xlv
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Characteristics of the Exclusive ModesCharacteristics of the Exclusive Modes
Mass Width BRB+l 135 MeV - 90*10-6
B+l 770 MeV 150 MeV 130*10-6
B+l 782 MeV 8 MeV 165*10-6
B+a1l 1230 MeV 400 MeV? 102*10-6
B+Xl(nres) - - 616*10-6
B0l 139.6 MeV - 180*10-6
B0l 771 MeV 150 MeV 260*10-6
B0a1l 1260 MeV 400 MeV? 130*10-6
B0b1l 1235 MeV 140 MeV 82*10-6
B0Xl(nres) - - 616*10-6
Since the main background is the one from bcldecays,high and wide mass resonances will be less pure
04/10/03 Daniele del Re Excl B DecaysDaniele del Re Excl B Decays 5
Sample CompositionSample Composition
Applying basic cuts:
410fb-1
Fitted Mx
470fb-1
Fitted Mx
•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
BB++ BB00
04/10/03 Daniele del Re Excl B DecaysDaniele del Re Excl B Decays 6
B+ 0 l+ B+ 0 l+
F. Gallo
410fb-1
Fitted Mx
B+l (preliminary) selection:• Basic cuts (previous slides)
• mm2 < 0.4 GeV2
• Nchg in X = 0
• 0 < Mxhadfit < 0.2 GeV
Main issue: recover merged
In 120 fb-1 (assuming ~50% recovering):Nsig = ~10, Nbkg ~0Mx(GeV)
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B+ 0 l+ B+ 0 l+
D. del Re
B+l (preliminary) selection:• Basic cuts (previous slides)
• mm2 < 0.5 GeV2
• Nchg in X = 2
• Mxhad – Mxhadneu < 0.1 ( veto)
In 120 fb-1:Nsig = ~13, Nbkg ~4
250fb-1
Fitted Mx
04/10/03 Daniele del Re Excl B DecaysDaniele del Re Excl B Decays 8
B+ l+ B+ l+
S. Pisano
B+l (preliminary) selection:• Basic cuts (previous slides)
• mm2 < 0.6 GeV2
• Nchg in X = 2
• Mxhad – Mxhadneu > 0.15 ( veto)
In 120 fb-1:Nsig = ~10, Nbkg ~6
410fb-1
Fitted Mx
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B0 - l+ B0 - l+
M. Kocian
470fb-1
Fitted Mx
Here we are trying to relax the basic cuts.
For instance we are studying the possibility to remove the lepton PID .
In 120 fb-1:Nsig = ~15, Nbkg ~1
04/10/03 Daniele del Re Excl B DecaysDaniele del Re Excl B Decays 10
B0 (a,b)- l+ B0 (a,b)- l+
L. Li Gioi
120fb-1 S Btot
B0l 15 13
B0a1l 3 10
B0b1l 2 25
One chg track in X
Three chg tracks in X
(preliminary) selection:• Basic cuts (previous slides)
• mm2 < 0.5 GeV2
• and…
04/10/03 Daniele del Re Excl B DecaysDaniele del Re Excl B Decays 11
Which Sensitivity by July?Which Sensitivity by July?
Recoil expected 120fb-1 (*)
Recoil expected 120fb-1(*)
Recoil expected 120fb-1(*)
Recoil expected 120fb-1(*)
(0.9±0.2±0.2)x2PDG
Recoil expected 120fb-1 (*)
(*) = only statistical error
B+0lx
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q2 Spectrumq2 Spectrum
q2 spectrum for B0l-
modelsreconstructed
120 fb-1
q2(GeV2)
Not enough statistics (120 fb-1) to discriminate among models
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ConclusionsConclusions
• 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**)l)
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People involved and organizationPeople involved and organization
• B+lFrancesco Gallo
• B+lSilvia Pisano
• B+lDdR
• B0 l : Martin Kocian
• B0 l : Luigi Li Gioi
and R. Faccini, V. Luth, U. Langenegger, F. Simonetto
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)