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

2. 04/10/03 Daniele del Re Excl B Decays 2 V ub Inclusive Analysis: Potential B  l  B  l  B  l  B  a  l   170 B  X u l events on data after all cuts for M X <1.55GeV exclusive channels can be studied with ~same technique large potential to perform exclusive V ub analyses

3. 04/10/03 Daniele del Re Excl B Decays 3 assuming DECAY.dec branching ratios N SL =32000 (N B  Xl  events on data (20.5K B +,11.5K B 0 ) 17 B +   l 25 B +   l 25 B +  l 15 B +  a 1 l 19 B 0   l 27 B 0   l 17 B 0  a 1 l Events in 82fb -1 with Nlepton>0 Pcms>1 GeV 82fb -1 Available Sample

4. 04/10/03 Daniele del Re Excl B Decays 4 Characteristics of the Exclusive Modes MassWidthBR B +   l 135 MeV-90*10 -6 B +   l 770 MeV150 MeV130*10 -6 B +  l 782 MeV8 MeV165*10 -6 B +  a 1 l 1230 MeV400 MeV?102*10 -6 B +  Xl (nres) --616*10 -6 B 0   l 139.6 MeV-180*10 -6 B 0   l 771 MeV150 MeV260*10 -6 B 0  a 1 l 1260 MeV400 MeV?130*10 -6 B 0  b 1 l 1235 MeV140 MeV82*10 -6 B 0  Xl (nres) --616*10 -6 Since the main background is the one from b  cl  decays, high and wide mass resonances will be less pure

5. 04/10/03 Daniele del Re Excl B Decays 5 Sample Composition Applying basic cuts: 410fb -1 Fitted Mx 470fb -1 Fitted Mx one fully reconstructed B +- / B 0 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) -1GeV 2 < mm2 < 1GeV 2 B+B+B+B+ B0B0B0B0

6. 04/10/03 Daniele del Re Excl B Decays 6 B +   0 l + F. Gallo 410fb -1 Fitted Mx B +   l (preliminary) selection: Basic cuts (previous slides) mm 2 < 0.4 GeV 2 Nchg in X = 0 0 < Mxhadfit < 0.2 GeV Main issue: recover merged    In 120 fb -1 (assuming ~50% recovering): Nsig = ~10, Nbkg ~0 Mx(GeV)

7. 04/10/03 Daniele del Re Excl B Decays 7 B +   0 l + D. del Re B +   l (preliminary) selection: Basic cuts (previous slides) mm 2 < 0.5 GeV 2 Nchg in X = 2 Mxhad – Mxhadneu < 0.1 (  veto) In 120 fb -1 : Nsig = ~13, Nbkg ~4 250fb -1 Fitted Mx

8. 04/10/03 Daniele del Re Excl B Decays 8 B +   l + S. Pisano B +  l (preliminary) selection: Basic cuts (previous slides) mm 2 < 0.6 GeV 2 Nchg in X = 2 Mxhad – Mxhadneu > 0.15 (  veto) In 120 fb -1 : Nsig = ~10, Nbkg ~6 410fb -1 Fitted Mx

9. 04/10/03 Daniele del Re Excl B Decays 9 B 0   - 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

10. 04/10/03 Daniele del Re Excl B Decays 10 B 0  (  a,b) - l + L. Li Gioi 120fb -1 SBtot B 0   l 1513 B 0  a 1 l 310 B 0  b 1 l 225 One chg track in X Three chg tracks in X (preliminary) selection: Basic cuts (previous slides) mm 2 < 0.5 GeV 2 and…

11. 04/10/03 Daniele del Re Excl B Decays 11 Which Sensitivity by July? Recoil expected 120fb -1 (*) (0.9±0.2±0.2)x2 PDG Recoil expected 120fb -1 (*) (*) = only statistical error B +  0 l  x 

12. 04/10/03 Daniele del Re Excl B Decays 12 q 2 Spectrum q 2 spectrum for B 0   l - models reconstructed 120 fb -1 q 2 (GeV 2 ) Not enough statistics (120 fb -1 ) to discriminate among models

13. 04/10/03 Daniele del Re Excl B Decays 13 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 ** )l )

14. 04/10/03 Daniele del Re Excl B Decays 14 People involved and organization B +   l  Francesco Gallo B +  l  Silvia Pisano B +   l  DdR B 0   l : Martin Kocian B 0   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)