CP violation at Belle

Kenkichi Miyabayashifor Belle collaboration

(Nara Women’s University)

2003/Oct./14th

BEAUTY2003

KM unitarity triangle andCPV parameter convention

Topics to be covered…

• sin2 (sin2) related (140/fb) ;– CPV golden mode; B0 J/ KS

– CPV in B0 J/ 0

• 2 () related (78/fb);– CPV in B0 +-

Time dependent CP asymmetry

CP eigenstate reconstruction

Mbc(GeV)

E(GeV)

Two key variables;Mbc = { (ECM/2)2 - ( Pi)2}1/2

B mass(5.28GeV)E = Ei - ECM/2

0

Note;These are for full-reconstructable case.For the mode having missing or KL, different variables are used.

Example; B0 J/ KS

Vertex recon. to measure t

BB system is boosted=0.425 ; t obtained by z

Require consistent with run-dep. IP profile (r=21m).

CP side vertex· reconstructed by dilepton from J/, +- pair, etc.

Tag side vertex · Impact parameter w.r.t CP side vertex < 500m· KS veto· If reduced 2 > 20 … remove the track having largest2

Resolution function· including charmed meson lifetime, motion of B meson,· Validation by lifetime measurement.

Inclusive Leptons:high-p l b c l intermed-p l+ s l

Inclusive Hadrons:high-p + B0D(*) +, D(*) +, etc.intermed-p K+ K+ X,

low-p D0

Flavor tagging by other B decay products

Based on the calculated likelihood, q =+1 for B0, -1 for B0 (Tag side)r = from 0(no flav. info.) up to 1(perfectly confident tag).

Validation of flavor tagging

B0 D*-l+ decay is self tagging;reconstructed with high purity

Good tag

Poor tag

OF-SF asymmetry ~ (1-2w)cos(mt)w is also investigated.

1-2w

CP fit : unbinned max. likelihood fit

Signal probability density function(PDF) is;Psig(t, q, wl, wl)= exp(-|t|/B)/4B{1-qwl+q(1-2wl)[SfCPsin(mt)+AfCPcos(mt)]}

here, l is flavor tagging class(1,2,…6).

For i-th event, likelihood value is;Pi(ti, SfCP, AfCP)=(1-fol)[fsig Psig(t, q, wl, wl) X Rsig(ti) + fbg Pbg X Rbg (ti)]

+ fol Pol(ti)

Free parameters : SfCP and AfCP Proper resolution func. : R**

B life and mixing : PDG values Fraction of each component : f**

sin21 (-CPSccs)measurement B0 charmonium + K recon.

Mode CPNevents Purity

J/ KS(+-) -1 1997 0.98

J/ KS(00) -1 288 0.82

’(l+l-) KS -1 145 0.93

’(J/) KS -1 163 0.88

c1 KS -1 101 0.96

c (KSK)KS -1 123 0.72

c (KK)KS -1 74 0.70

c (pp) KS -1 20 0.91

J/ K*0(KS0) +1* 174 0.93

J/ KL +1 2332 0.60* 81%.

B0 J/ KL

(for sin21 measurement)

Only KL direction known.In Upsilon(4S) rest frame,B has ~340MeV/c.Reconstruct it with two-bodykinematics assumption.

CPV in B0 charmonium+K0:sin21

sin21 = 0.733±0.057(stat)±0.028(syst)

If is free in the fit,||=1.007±0.041(stat)consistent with 1

Now precision measurement!

CPV in B0 J/ 0

Decay caused by b ccd transition CP = +1

Tree has no complex phase if it dominates SJ/ = -sin21 and AJ/ = 0

Reconstruction of B0 J/ 0

103events reconstructed.Relatively clean; purity=86±10%

Backgrounds are separately est. for B J/ X and combinatorial.

Results for SJ/ and AJ/

After ftag and vtx, 91 events are used.SJ/ = -0.72±0.42(stat)±0.08(syst)AJ/= -0.01±0.29(stat)±0.07(syst)

B0

B0

CPV in B0 + -

If only tree contributes, Vub interferes Vtd(in mixing)extract 2!

However, penguin looks significantly large(B0 00, listen T.Higuchi’s talk)

so that effect on CP asymmetry is there.

Event selection of + -

LR>0.825

enhanced

LR<0.825=

Kenhanced

To suppress cont. bg,Likelihood Ratio(LR) is calculated by event shape and B’s flight direction.Correlation with flav. tag is taken intoaccount in the CP fit.

760 candidates;(163+24/-23 signals)are obtained by 78/fb.

Results for S and A

S = -1.23±0.41(stat)+0.08/-0.07(syst)A = +0.77±0.27(stat)±0.08(syst)

Results for S and A(cont.)

Our result is 3.4 away from CP conservation(i.e. S=A=0).

Conclusions and future• sin2=0.733±0.057(stat)±0.028(syst)

– Moving into the precision measurement regime.

– Relevant modes(b ccd) making progress.• B0 +- is away from CP conserv.(3.4)

– Analysis using 140/fb is in progress.

Now going to resume physics run with newSVD and smaller radius beampipe.

Backup slide

sin21:charmonium + KS

and J/ KL

Opposite asymmetryby diff. CP eigenvalueis clearly seen!

B± DCP K±

D1K- D1K+

D2K-D2K+

B DK decay can be caused via Vcb and Vub, if D decays into CP eigenstate(D1(K+K-, +-), D2(KS0, KS, KS, KS, KS’)),

possibility to access 3

A1=0.06±0,19(stat)±0.04(sys) A2=-0.19±0.17(stat)±0.05(syst)