Hadronic Moments in Semileptonic B Decays Ramon Miquel Lawrence Berkeley National Laboratory (for the CDF II Collaboration)

7/2/04Ramon Miquel BEACH 042 F theory evaluated using OPE in HQET: expansion in  s and 1/m B powers: O(1/m B )  1 parameter:  (Bauer et al., PRD 67 (2003) ) O(1/m B 2 )  2 more parameters: 1, 2 O(1/m B 3 )  6 more parameters:  1,  2, T 1-4 Motivation (I)  (4S), LEP/SLD, CDF measurements. Experimental  |V cb |~1% Theory with pert. and non-pert. corrections.  |V cb |~2.5% Most precise determination of V cb comes from  sl (“inclusive” determination):

7/2/04Ramon Miquel BEACH 043 Motivation (II) Hadronic moments: B  X c l, recoil mass M(X c ) Leptonic moments: B  X c l, lepton E in B rest frame Photonic moments: Photon energy in b  s  (CLEO, DELPHI, BABAR) (CLEO) (CLEO, DELPHI, BABAR, CDFII) Many inclusive observables can be written using the same expansion (same non-perturbative parameters): the spectral moments: Constrain the unknown non-pert. parameters and reduce |V cb | uncertainty. With enough measurements: test of underlying assumptions (duality…).

7/2/04Ramon Miquel BEACH 044 What is X c ?  ~25% of semi-leptonic width is poorly known Higher mass states: D**Semi-leptonic widths (PDG 03): Br (%) B +  X c l  0.26 B +  D* l 6.00  0.24 B +  D l 2.23  0.15 (b/B + /B 0 combination, b  u subtracted) Possible D’  D ( * )  contributions neglected: No experimental evidence so far DELPHI limit: We assume no D’ contribution in our sample

7/2/04Ramon Miquel BEACH 045 Analysis Strategy Typical mass spectrum M(X 0 c ) (Monte Carlo): D 0 and D* 0 well-known  measure only f**  only shape needed 1) Measure f**(s H ) 2) Correct for background, acceptances, bias  moments of D** 3) Add D and D*  M 1,M 2 4) Extract , 1

7/2/04Ramon Miquel BEACH 046 Channels −D **0  D +   OK –D **0  D 0  0 Not reconstructed. Half the rate of D +   –D **0  D *+   D *+  D 0  + OK D *+  D +  0 Not reconstructed. Feed-down to D +   –D **0  D *0  0 Not reconstructed. Half the rate of D *+   Must reconstruct all channels to get all the D ** states.  However CDF has limited capability for neutrals B 0  D **  l + always leads to neutral particles  ignore it B -  D **0 l  better, use isospin for missing channels:

7/2/04Ramon Miquel BEACH 047 D **0 D *+  **- D 0  *+ (Br=67.7%) K -  + (Br=3.8%) K -  +  -  + (Br=7.5%) K -  +  0 (Br=13.1%) Event Topology Exclusive reconstruction of D ** : D **0 D +  **- K -  +  + (Br=9.1%) “D + ”“D* + ”

7/2/04Ramon Miquel BEACH 048 Backgrounds Combinatorial background under the D ( * ) peaks:  sideband subtraction Physics background: B  D ( * )+ D s , D (s)  Xl  MC, subtracted Prompt pions faking  **: fragmentation underlying event  separate B and primary vertices (kills also prompt charm)  use impact parameters to discriminate  model: wrong-sign  ** +  combinations Feed-down in signal: D** 0  D* + (  D +  0 )   irreducible background to D** 0  D +  .  subtracted using data:  shape from D 0   in D** 0  D* + (  D 0  + )    rate: ½ (isospin) x eff. x BR

7/2/04Ramon Miquel BEACH 049 Lepton + D ( * )+ Reconstruction Lepton + D ( * )+ : D vertex: 3D l+D(+  * ) vertex (“B”): 3D L xy (B) > 500  m M(B) < 5.3 GeV Data Sample: e/  + displaced track ~ 180 pb -1 (  Sept 2003) Track Selection: e/  : p T > 4 GeV other: p T > 0.4 GeV Total: ~ events

7/2/04Ramon Miquel BEACH 0410  ** Selection Based on topology: impact parameter significances w.r.t. primary, B and D vertices  ** 3D IP signif. wrt BV  ** 2D IP signif. wrt PV p T > 0.4 GeV  R < 1.0 |d 0 PV /  | > 3.0 |d 0 BV /  | < 2.5 |d 0 DV /  | > 0.8 L xy B  D > 500  m Cuts are optimized using MC and background data: Additional cuts only for D + :

7/2/04Ramon Miquel BEACH 0411 Raw m** Distribution Measured in  m**, shifted by M(D ( * )+ ), side-band subtracted. D 1,D 1 *,D 2 * D 2 *,D 0 * Feed-down

7/2/04Ramon Miquel BEACH 0412 Efficiency Corrections 1) Correct the raw mass for any dependence of  reco on M(D**): Possible dependence on the D** species (spin). Monte-Carlo for all D** (Goity-Roberts for non-resonant), cross-checked with pure phase space decays. 2) Cut on lepton energy in B rest frame: Theoretical predictions need well-defined p l * cut. We can’t measure p l *, but we can correct our measurement to a given cut:  p l * > 700 MeV/c.

7/2/04Ramon Miquel BEACH 0413 Corrected Mass and D** Moments Procedure: Unbinned procedure using weighted events. Assign negative weights to background samples. Propagate efficiency corrections to weights. Take care of the D + / D* + relative normalization. Compute mean and sigma of distribution. Results: No Fit !

7/2/04Ramon Miquel BEACH 0414 Final Results Pole mass scheme 1S mass scheme

7/2/04Ramon Miquel BEACH 0415 Systematic Errors  m 1 (GeV 2 )  m 2 (GeV 4 )  M 1 (GeV 2 )  M 2 (GeV 4 )  (GeV)  1 (GeV 2 ) Stat Syst Mass resolution Eff. Corr. (data) Eff. Corr. (MC) Bkgd. (scale) Physics bkgd D + / D *+ BR D + / D *+ Eff Semileptonic BRs 1 TiTi ss m b, m c Choice of p l * cut

7/2/04Ramon Miquel BEACH 0416 Comparison with Previous Measurements Pole mass scheme

7/2/04Ramon Miquel BEACH 0417 Summary First measurement of hadronic moments in semileptonic B decays performed at a hadron collider. Good agreement with HQET and previous determinations. Competitive with other experiments. Little model dependency. No assumptions on shape or rate of D** components. Increased statistics and improved tracking will lead to substantially more precise results in the near future.

BACK-UP SLIDES

7/2/04Ramon Miquel BEACH 0419 CKM and V cb | V cb | = A 2 (defines the scale of UT)

7/2/04Ramon Miquel BEACH 0420 |V cb | from inclusive B decays Experiment: large statistics on BR(B  X c - ) and  B and small systematics V cb measurements |V cb | from exclusive B decays Large statistics on B d 0  D (*) - available and new measurements are coming Present precision (5%) is systematics limited : Experiments: D** states, D’s BR Theory: form factor extrapolation, corrections to F (1)=1 can be reduced in the future |V cb | excl =(42.1  1.1 exp  1.9 theo )  (PDG 2002, V cb review) |V cb | incl = (40.4 ± 0.5 exp ± 0.5 , ± 0.8 theo )  (PDG 2002, V cb review)

7/2/04Ramon Miquel BEACH 0421 Lepton + D Reconstruction Lepton + D ( * )+ : D vertex: 3D l+D(+  * ) vertex (“B”): 3D L xy (B) > 500  m L xy (D /B ) > -200  m m(B) < 5.3 GeV Data Sample: e/  + displaced track ~ 180 pb -1 (  Sept 2003) Track Selection: e/  : p T > 4 GeV other: p T > 0.4 GeV

7/2/04Ramon Miquel BEACH 0422 D* + Reconstruction and Yields D* + channels:  m*  M(D 0  * ) – M(D 0 ) D ( * )+ l  (+cc)   yields: ~ events

7/2/04Ramon Miquel BEACH 0423 Monte-Carlo Validation (I) K , e K , e K ,  K  0, e K ,  K , e MC vs. semileptonic sample: Matching  2 probability for those plots: 67%74%23% 43%69%87%

7/2/04Ramon Miquel BEACH 0424 Monte-Carlo Validation (II) Relative yield prediction K3  /K  : (cross-check) R data = 0.77±0.02 R pred = 0.80±0.04 R pred /R data = 1.04±0.06  efficiency for adding tracks understood Relative yield prediction K2  /K  : (needed for D + /D* normalization) Two methods (a,b) to derive this BR a)Based on inclusive b  D (*)+ l b)Based on exclusive B  D (*)+ l, D ** l + PDG BR + MC efficiency ratios  uncertainties in Br (incl.) and D** spectroscopy (excl.) compromise prediction  1. – 0.87 = 13% used as systematics R data R pred R pred /R data 3.71± ± ± ± ± ±0.08

7/2/04Ramon Miquel BEACH 0425 Impact Parameters in MC Comparison data/MC for IP: (worst case) KK  ** 2D IP signif. wrt PV KK  ** 3D IP signif. wrt BV Residual corrections: derived from data:  * non-SVT D daughters (p T > 1.5 GeV) corrections from double ratios in p T in m**

7/2/04Ramon Miquel BEACH 0426 Background Subtraction Use mass side-bands to subtract combinatorial background. Use D* + [  D 0  + ]   to subtract feed-down from D* + [  D +  0 ]   to D +  . Use wrong-sign  ** + l  combinations to subtract prompt background to  **. –Possible charge asymmetry of prompt background studied with fully reconstructed B’s: 4% contribution at most. Possible D’  D ( * )  contributions neglected: –No experimental evidence so far. –DELPHI limit: We assume no D’ contribution in our sample

7/2/04Ramon Miquel BEACH 0427 Combination with D 0, D* 0 Take M(D 0 ), M(D* 0 ),  sl,  0,  * from PDG 2003 : −  sl  0,  * are obtained combining BR’s for B , B 0 and admixture, assuming the widths are identical (not the BR’s themselves), and using f  / f 0 = 1.04 ± 0.08  (B  ) /  (B 0 ) = ± –Results: BR(B +  X 0 c l + l ) = ± BR(B +  D 0 l + l ) = ± BR(B +  D* 0 l + l ) = ±

7/2/04Ramon Miquel BEACH 0428 Main Systematics Semileptonic branching ratios when combining D** with D and D* Efficiency corrections from data − Use data-corrected efficiency. vs. pure MC efficiency Efficiency corrections from D** Monte-Carlo − D** states + NR Goity-Roberts vs. pure phase-space Mass resolution: − Dominated by satellite: ± 60 MeV Prompt background scale − Charge correlations WS / RS: ± 4% Other: D + /D* normalization, physics, p l * cut, theory…