Summary of  2 measurements at Super KEKB Hirokazu Ishino Tokyo Institute of Technology 19 Dec., 2006

current status  2 constraint with a 50ab -1 data sample –  time-dependent Dalitz plot analysis –  time-dependent CP violation (tCPV) parameter isospin analysis including  0  0 –  tCPV parameter measurements and isospin analysis S 00 measurement Summary Contents

Notes Almost all the measurement errors are systematic dominant with 50ab -1 data. – except for  0  0, A 00 and S 00 For the  2 constraints, we use the R-fit. –J. Charles et al., Eur. Phys. J. C 41, 1 (2005) Theoretical uncertainties are not taken into account. –will be summarized later.

Current Status Dalitz+isospin   ~10 degrees

B 0 →(   time-dependent Dalitz plot analysis involves cos(2  2 ) 27 parameter fit: one of the most complicate analyses!

B→  systematic errors by A. Kusaka in BNM

B→  errors by A. Kusaka in BNM

 2 constraints with B→  at Super B factory by A. Kusaka in BNM

Isospin relation M. Gronau and D. London, PRL 65, 3381 (1990) The cleanest method to extract  2 The measurements we need are branching fractions, CP asymmetry parameters and longitudinal polarization fraction in B→ .

B→  measurements HFAG2006 Super B 2020(?)

B→  systematic errors Branching fraction –PDF shapes, B.G. fractions, track ,  0  –assume PDF and B.G. errors reduce to 1/10 –assume track and  0  reduce to half: still dominant assign track  = 1%,  0  = 2% CP asymmetries –assign 1% error to both A and S f L –the current error: PDF shape and B.G. fractions –assume those are reduced to 1/10

 2 constraint with B→  at Super B factory without asymmetries in B→  0  0 We definitely need the asymmetries in B→  0  0 for more constraints. 22 11

B 0 →      asymmetries With 50ab -1 data, we assume –number of signal events: 5000 –number of background events assume the CP asymmetries of the main backgrounds such as continuum and a 1  are well known. Toy MC using  E and M bc in the PDF –  (S)=0.10,  (A)=0.08 Note: if we use LR (fisher discriminant), the error would be improved. assume systematic error is much smaller than the statistics.

 2 constraint with B→  at Super B factory 22 11 dashed line: w/o  0  0 asymmetries red solid line: w/  0  0 

B→  at Super B factory Super B 2020(?) The ambiguity can be reduced if we measure the mixing- induced CP violation parameter S 00 in B 0 →  0  0 decays

B 0 →      vertexing We need B 0 →  0  0 decay vertex position Use  0 Dalitz decay –  0 →  e + e − – but small B.R. of ~1.2% photon conversion –reconstruct a photon from a e + e − pair –B vertex reconstruction with the same technique as K S –Conversion probability ~3% per photon in the current Belle silicon detector reconstruct photon track from an electron-positron pair the photon track is extracted to the IP position.

generate 1M Geant MC events with Belle detector –2.2%  0 Dalitz decay –11.3% photon conversion –0.2%  0 Dalitz + photon conversion reconstruction –one  0 from 2 , the other  0 from  + e + e − pair e + e − pair either from IP or V0finder –B candidates within |  E| 5.26GeV/c 2 –require at least two hits in Silicon Vertex Detector (SVD) –reconstruction efficiency 1.4% –estimated signal events with vertex info. : 920 w/ 50ab -1 data Backgrounds estimated from Geant MC samples –  +  0 : 300 – continuum events: B 0 →      event selection

continuum suppression variable signal +0+0 continuum  E, M bc and LR are used for the fit to the time-dependent CP parameters. signal +0+0 continuum Toy MC projection plots

~120  m ~150  m B 0 →      vertex resolution z(CP,rec) - z(CP,gen) dz(CP-tag, rec) - dz(CP-tag, gen)

Toy MC –# of signal =920 –resolution function obtained from Geant MC previous page –tagging efficiency 30% – B + →  +  events – e + e - →qq (q=u,d,s,c) continuum background: events. RMS of fitted S 00 –  S00 = 0.23 B 0 →      Toy MC

 2 constraint with B→  at Super B factory w/ S 00 w/o S 00

Theoretical  uncertainties on 

Summary  2 constraints at Super B factory – B→  systematic error dominant: the size of total error is 1/5 of the current Belle measurement.  2 ~ 2 ◯ – B→  systematic error dominant other than B 0 →  0  0  2 < 1 ◯ – B→  systematic error dominant other than S 00  2 ~ 3 ◯ Theoretical uncertainty ~3 ◯, comparable with the experimental uncertainties

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B→a   first tCPV measurements additional constraints on  (  2 ) in near future!