EXPERIMENTAL UPDATE ON |Vcb| (EXCLUSIVE) Arantza Oyanguren ( DELPHI - Valencia ) CKM WORKSHOP ‘03

|Vcb| FROM B D *l -  l Vcb From the s.l. decay width: q2 nl c b 1 |Vcb| FROM B D *l -  Vcb q2 l nl c b From the s.l. decay width: Known function (Phase space) Form factor of the B D* transition   Normalized by HQET (mQ  ) at q2max (w = 1)   1/ mQ and QCD corrections  FD*(1)=1 FD*(1)= 0.91  0.04 * * PDG ‘02 CKM ‘03 A. Oyanguren

SIGNAL RECONSTRUCTION 2 SIGNAL RECONSTRUCTION BABAR (4S) BB pB ~ 30 GeV BELLE pB ~ 1 GeV ALEPH DELPHI OPAL CLEO Z  bb pB ~ 0.3 GeV CKM ‘03 A. Oyanguren

SIGNAL RECONSTRUCTION m= m(D0) -m(D0) ~ m(soft) 3 SIGNAL RECONSTRUCTION B  D* l -  @ LEP p  1.0 GeV @ (4S) p  0.1 GeV D *- lepton candidates : D0 soft m= m(D0) -m(D0) ~ m(soft) K- + K- + + - K- +0 Ks0 + - Inclusive D0 Exclusive D0 OPAL BABAR CKM ‘03 A. Oyanguren

E, p conservation, vertex info... 4 w RECONSTRUCTION Efficiency: E, p conservation, vertex info... From decay products From missing energy Measured  @ LEP: ~ 0.07- 0.13 w Resolution:  @ (4S): ~ 0.03 ALEPH w CKM ‘03 A. Oyanguren

BACKGROUND Disentangling D * ’s coming from D ** states... @ (4S) 5 BACKGROUND Disentangling D * ’s coming from D ** states... b  D*+ X l_ l @ (4S) @ LEP ~ 66% charged particles D*l  (73.5%) D**l  (7.5%) Fake lep (0.3%) Uncorr (6.2%) Correlated (1.5%) Contin. (3.2%) Fake D* (7.75%) ElectronsK BABAR cosB,D*l topology info events/0.27  data D*l  D**l  Comb. Bg. DELPHI events/01 OPAL CKM ‘03 A. Oyanguren

6 FITS TO|Vcb|  Parametrization of the form factor F(w) from I. Caprini, L. Lellouch, M. Neubert [NPB 530, 153 ‘98]* as a function of the slope form factor 2 and the form factor ratios R1 and R2 (measured by CLEO [PRL 76, 3898 ‘96] ).  Fit d/dw to extract F(1)|Vcb| and 2 w w BELLE CLEO Entries/0.05 FD*(1)|Vcb| * See also C.G. Boyd, B. Grinstein, R.F. Lebed [PRD 56, 6895 ‘97] CKM ‘03 A. Oyanguren

STATISTICS Analyzed events : OPAL D* l candidates DELPHI CLEO ALEPH 7 STATISTICS Analyzed events : OPAL D* l candidates DELPHI CLEO ALEPH BELLE Statistical error BABAR ALEPH DELPHI OPAL CLEO BELLE (partial stat.) BABAR (expected) Vcb/Vcb (%) CKM ‘03 A. Oyanguren

SYSTEMATICS 8a @ LEP @ (4S) CKM ‘03 A. Oyanguren BABAR (BR) BELLE Moriond EW ‘03 BELLE PLB 526, 247 ‘02 hep-ex/0112028 CLEO @ (4S) CKM ‘03 A. Oyanguren

8b SYSTEMATICS @ LEP hep-ex/0112028 CKM ‘03 A. Oyanguren

8c SYSTEMATICS @ (4S) CLEO CKM ‘03 A. Oyanguren

SYSTEMATICS BABAR (BR) BELLE @ (4S) 8d Moriond EW ‘03 PLB 526, 247 ‘02 CKM ‘03 A. Oyanguren

UPDATED WORLD AVERAGE Winter ‘03 PDG ‘03 Using F(1)=0.91  0.04 F(1)|Vcb| = (38.1  1.0) 10-3 r2 =1.57  0.14 PDG ‘03 F(1)|Vcb| = (38.8  0.5(stat).  0.9(sys.)) 10-3 r2 =1.49  0.05(stat.)  0.14(sys.) 2/d.o.f.=1.7 CL=6.9%  Analyses rescaled to common parameters: http://www.slac.stanford.edu/xorg/hfag/semi/pdg03/common.param Using F(1)=0.91  0.04 |Vcb|= (42.6  0.6(stat)  1.0(sys)  2.1(th.)) 10-3 (Thanks to E. Barberio and U. Langenegger (HFAG) for the averages) CKM ‘03 A. Oyanguren

|Vcb|= (42.4  3.7(exp.)  3.0(th.))10-3 |Vcb| FROM B D l -  CLEO BELLE D0, D+ D+ ALEPH D+ BELLE Winter ‘03 G(1)|Vcb| = (41.9  3.7) 10-3 rD2 =1.15  0.16 Using G(1)=1.00  0.07 PDG ‘03 G(1)|Vcb| = (42.4  3.7) 10-3 rD2 =1.14  0.16 2/d.o.f.=0.06 CL=99% |Vcb|= (42.4  3.7(exp.)  3.0(th.))10-3 CKM ‘03 A. Oyanguren

11 CONCLUSIONS  |Vcb| from exclusive measurements limited by systematics from several sources and theory  large systematics are correlated between experiments: B(b B0), B((4S) B0 B0), D BR’s, D ** contribution, R1 and R2 form factors... CKM ‘03 A. Oyanguren

12 PERSPECTIVES  Waiting for BABAR results, and BELLE with larger analyzed statistics,  waiting for more accurate lattice computations of FD*(1) and GD(1),  the control of the main systematics by additio-nal measurements  and CLEO-c results on D BR’s CKM ‘03 A. Oyanguren