Physics on the Recoil: Exclusive Charmless Semileptonic Decays Daniele del Re University of California San Diego.

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

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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

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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…

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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)