Takeo Higuchi Institute of Particle and Nuclear Studies, KEK for the Belle collaboration Oct 14, 2003; Pittsburgh, PA Takeo Higuchi, KEK BEAUTY2003 Hot Topics from the Belle Experiment

Introduction to the Belle experiment CP violation in B 0   K S Evidence of B 0    0   0 New resonance X(3872) Summary Contents

Introduction to the Belle Experiment Introduction to the Belle Experiment

e+e+ ee 3km circumference L = (1.06  )/cm 2 /sec  L dt = 158 fb  1 On-resonance 140 fb  1 L = (1.06  )/cm 2 /sec  L dt = 158 fb  1 On-resonance 140 fb  1 World Records History 1999 Jun2003 Jul 3.5 GeV e +  8.0 GeV e  – e + e    (4S) with  = – Crossing angle = ±11 mrad. KEKB Accelerator

Belle Detector K L  detector 14/15 layer RPC+Fe Electromagnetic Calorimeter CsI(Tl) 16X 0 Aerogel Cherenkov Counter n = 1.015~1.030 Si Vertex Detector 3 layer DSSD TOF counter 8.0 GeV e  3.5 GeV e + Central Drift Chamber Tracking + dE/dx 50-layers + He/C 2 H 5

People 274 authors, 45 institutions many nations many nations 274 authors, 45 institutions many nations many nations

CP Violation in B 0   K S

CP Violation by Kobayashi-Maskawa KM ansatz:CP violation is due to complex phase in quark mixing matrix KM ansatz:CP violation is due to complex phase in quark mixing matrix unitarity triangle CP violation parameters (  1,  2,  3 ) = ( , ,  ) CP violation parameters (  1,  2,  3 ) = ( , ,  ) O  

Time-Dependent CP Asymmetry Inputs:  f =  1,S = 0.6 A = 0.0 A = 0 or | | = 1  No direct CPV S =  f sin2  1 : SM prediction

New Physics Hunting in b  sqq  + New process w/ different CP phase New process w/ different CP phase SM penguin Deviation from b  ccsHint of new physics SM predicts same CPV in b  ccs and sqq. SM predicts same CPV in b  ccs and sqq. e.g.) squark penguin New physics may deviate CPV in b  ccs from sqq

b  ccs Reconstruction 5417 events are used in the fit. 140 fb  1, 152M BB pairs J/  K L signal B 0  J/  K L b  ccs w/o J/  K L p B * (cms) Beam-energy constrained mass (GeV/c 2 ) Detail by K.Miyabayashi

CP Violation in b  ccs M BB consistent with no direct CPV poor flavor tag fine flavor tag Small systematic uncertainty  Well controlled analysis technique Small systematic uncertainty  Well controlled analysis technique Detail by K.Miyabayashi K. Abe et al. [Belle collaboration], BELLE-CONF-0353.

b  sqq Reconstructions B 0   K S :   K + K , K S      – Minimal kaon-identification requirements. – Belle standard K S selection. – | M(KK)  M(  | < 10MeV/c 2 (mass resolution = 3.6 MeV/c 2 ). – | p  | in CMS > 2.0 GeV/c. – Belle standard continuum suppression (given later.) – |  E | < 60MeV, 5.27 < M bc < 5.29 GeV/c 2. M(KK) [GeV/c 2 ] Background is dominated by continuum CP in the background: –K  K  K S : (7.2±1.7)% –f 0 (980)K S : –These effects are included in the systematic error. Background is dominated by continuum CP in the background: –K  K  K S : (7.2±1.7)% –f 0 (980)K S : –These effects are included in the systematic error.

b  sqq Reconstructions  Cont’d B 0      K S – More stringent kaon-identification requirements. – Particle veto for ,  D 0,  c0, and J/   K  K  and D +  K  K S. – Belle standard continuum suppression. – |  E | < 40 MeV, 5.27 < M bc < 5.29 GeV/c 2. B 0   ´K S :1)  ´  ,    +   2)  ´   +  ,    – Belle standard continuum suppression. – |  E| < 60MeV (  ´   ;  100 <  E < +80 MeV (  ´      ) 5.27 < M bc < 5.29 GeV/c 2

B 0  KSB 0  KS B 0  KKKSB 0  KKKS B 0  KSB 0  KS Beam-Energy Constrained Mass 68  11 signals 106 candidates for S and A fit purity = 0.64  0.10 efficiency = 27.3% 244  21 signals 421 candidates for S and A fit purity = 0.58  0.05 efficiency = 17.7% (  ´      ) 15.7% (  ´   ) 199  18 signals 361 candidates for S and A fit purity = 0.55  0.05 efficiency = 15.7%

Unbinned Maximum Likelihood Fit 1. f sig :Event by event signal probability 2. P sig : 3. R:  t resolution function 4. P bkg :Background  t distribution signalbackground

CP Violation in b  sqq B0  KSB0  KS B0  KKKSB0  KKKS B 0   ’K S  f S A B  f CP (sqq) decay vertices are reconstructed using K- or  -track pair. Fit sin2  152M BB

Consistency Checks CP violation parameters with A = 0 – B 0   K S :  f S =  0.99 ± 0.50 – B 0  K  K  K S :  f S =  0.54 ± 0.24 – B 0   K S :  f S =  0.43 ± 0.27 Null asymmetry tests for S term – B    K  :  f S =  0.09 ± 0.26 – B    K  :  f S =  0.10 ± 0.14 Less correlation btw S and A Less correlation btw S and A Consistent with S = 0

Statistical Significance sin2  1 Hint of new physics? Need more data to establish conclusion. Hint of new physics? Need more data to establish conclusion. B 0  K  K  K S,  ´K S – Consistent with sin2  1. B 0   K S – 3.5  deviation (Feldman-Cousins). – S(  K S ) = sin2  1 : 0.05% probability. K. Abe et al. [Belle collaboration], hep-ex/ , submitted to Phys. Rev. Lett.

Evidence of B 0   0  0

Two possible diagrams require measured  2 disentangled Disentangling  2 bu d u W W d u u b t B 0      is one of promising decays to measure  2 T T P P Penguin-polluted CP violation Br(B 0   0  0 ) measurement gives constraint on .

B 0   0  0 Reconstruction B 0 reconstruction – 2   0 ’s with 115 < M(  ) < 152 MeV/c 2. – Efficiency = 9.90 ± 0.03%. – Those MC-determined distributions are used in extraction of signal yield with calibration using B   D 0   decays in data. Signal MC  E [GeV] M bc [GeV/c 2 ]

Continuum Suppression Fisher |cos  B | |r||r| Multi-dimensional likelihood ratio Continuum Signal MC e + e   BBe  e   qq 1  cos 2  for BB flat for qq Construct likelihood r = high  well tagged  originated from B decay r = low  poorly tagged  originated from qq Flavor tag quality B flight direction Fisher

B      0 Contamination  E-M bc shape: MC-determined 2-dimensional distribution. Yield: Recent Br measurement with MC-determined efficiency. According to MC study, other charmless decays than B      0 are negligible. Br(B      0 ) measurement: B. Aubert et al. [BaBar collaboration], hep-ex/ , submitted to PRL. B  0B  0 00 B  0B  0  E [GeV] M bc [GeV/c 2 ] charmless background incl.    0

Signal Extraction M bc [GeV/c 2 ]  E 152 M BB B      0 (modeled by MC) Signal Continuum Signal yield: Unbinned maximum likelihood fit Branching fraction Signal shape is modeled by MC, and is calibrated using B   D 0   decays in data. Significance incl. systematic error = 3.4  S.H.Lee, K.Suzuki et al. [Belle collaboration], hep-ex/ , submitted to Phys. Rev. Lett.

New Resonance X(3872)

New Narrow Resonance: X      J/  Mass distribution: DataMC  (2S) X New resonance X is found. [GeV/c 2 ] Events / GeV/c 2  conversion elimination

B+  K+XB+  K+X B+  K+XB+  K+X B +  K + X reconstruction – Add loosely identified kaon to X [GeV/c 2 ] [GeV] M bc M  J/  EE 3-dim. unbinned likelihood fit. 3-dim. unbinned likelihood 152M BB

What is X? Hypothesis I: 1 3 D 2 – M(X) = 3872 MeV/c 2 differs from prediction: M(1 3 D 2 ) = 3810 MeV/c 2. –  (1 3 D 2   c1 )/  (1 3 D 2   J  ) ~ 5, while  (X   c1 )/  (X   J  ) < 1 M bc M(  c1 ) No clear signal E.Eichten et al., Phys. Rev. D21, 203 (1980); W.Buchmüller and S.-H.H.Tye, Phys. Rev. D24, 132 (1981).

What is X?  Cont’d Hypothesis II: “molecular” charmonium – M(X) = 3872 ± 0.6 ± 0.5 MeV. – M(D 0 ) + M(D 0* ) = ± 1.0 MeV. – Do above facts suggest loosely bound D 0 -D 0 * state? – Need more data to conclude. QQ qq D 0 -D 0 * “molecule” S.-K.Choi, S.L.Olsen et al. [Belle collaboration], hep-ex/ , submitted to Phys. Rev. Lett.

Summary

3.5  deviation is observed with Feldman-Cousins in CP violation in B 0   K S from the SM.  Hint of new physics? Br(B 0   0  0 ) = (1.7±0.6±0.2)×10 6 is measured, which gives constraint on penguin uncertainty in  2. New resonance of X      J/  is observed at M(X) = ±0.6±0.5 MeV/c 2 that does not look like cc state.

Backup Slides

Mixing-Induced CP Violation B0B0 B0B0 B0B0 V tb V*V* V*V*  KSKS  td Sanda, Bigi & Carter b d b d t t WW b d  KSKS W W t t g g d s s s d s s s V tb V ts V tb V ts

How to Measure CP Violation? Find B  f CP decay Identify (= “tag”) flavor of B  f CP Measure decay-time difference:  t Determine asymmetry in  t distributions ee e+e+ e  :8.0 GeV e  :3.5 GeV B CP zz B tag  (4S)  ~ f CP  z  c  B ~ 200  m flavor tag Detail by K.Miyabayashi

Systematic Error of CPV in b  ccs SourcesError Flavor tag0.014 Vertex reconstruction0.013 Signal fraction (J/  K L ) Signal fraction (other)0.007  t resolution function Fit bias0.008 B tag decay interference0.008  t background distribution <  m B,  B < Total0.028 Small uncertainty in analysis procedure Small uncertainty in analysis procedure stat err. = 0.057

B 0  K  K  K S : CP =  1 Mixture K-K- KSKS B0B0 J=0 CP = (  1) decay CP = +1 K+K+ CP =  1 fraction is equal to that of =even/odd Since B 0  K  K  K S is 3-body decay, the final state is a mixture of CP =  1. How can we determine the mixing fraction?

-even fraction in |K 0 K 0 > can be determined by |K S K S > system CP = +1 l = odd l = even Using isospin symmetry, CP even B 0  K  K  K S : CP =  1 Mixture  Cont’d

 t Distributions  t [ps] B0  KSB0  KS B0  KSB0  KS B0  KKKSB0  KKKS B0  KKKSB0  KKKS B 0   ’K S q  f =  1 q  f =  1 q  f =  1 q  f =  1 q  f =  1 q  f =  1

Systematic Errors of CPV in b  sqq SA SASA Wtag fractions±0.018±0.007±0.005±0.006±0.005±0.007 Physics parameters±0.033±0.002±0.006±0.002±0.003±0.003 Vertexing±0.022±0.046±0.016±0.027±0.044±0.024 Background fraction±0.053±0.035±0.045±0.026±0.029 ±0.036 Background  t ±0.015±0.008±0.003±0.003±0.010±0.006 Resolution function±0.013±0.005±0.004±0.003±0.007±0.004 KKKs + f 0 Ks bkg ± Sum+0.09±0.07±0.05±0.04±0.05± KSKS 'KS'KS KKK S Systematics are small and well understood from b  ccs studies.

Systematic Uncertainty Sources  N S  N S  E peak position  0.03  0.04  E width  0.62  0.45 M bc peak position  0.04  0.04 M bc width  0.69  0.67 Rare B (  +  0 )  0.99  1.33 Total  3.34  3.43 Sources  Eff  Eff Fitting  5.3%  6.1%  0 efficiency  7.0%  7.0% MDLR selection  2.0%  2.0% Luminosity  0.5%  0.5% Total  %  9.5%

M(     ) Distribution M(     ) [GeV/c 2 ] Fit to  -mass is pretty good – M(     ) can be fitted by  -mass distribution well. – 1 3 D 2   J/  is forbidden by isospin conservation rule.

Constraint on  Amp(B       ) Amp(B       ) Amp(B       ) Amp(B       ) B  0 /B  = 1.04 B 00 /B  = 0.39 A  = 0.57 Using Our Results Belle Preliminary M.Gronau et al., Phys. Lett. B 514, 315 (2001).