S. Fratina

Measurement of the time-dependent CP-violating asymmetry in BO→KSOπOγ decays

We present a new measurement of CP-violation parameters in B(0)-->K(0)(S)pi(0)gamma decay based on a sample of 275 x 10(6) BB pairs collected at the Gamma(4S) resonance with the Belle detector at the KEKB energy-asymmetric e(+)e(-) collider. One of the B mesons is fully reconstructed in the B(0)-->K(0)(S)pi(0)gamma decay. The flavor of the accompanying B meson is identified from its decay products. CP-violation parameters are obtained from the asymmetry in the distribution of the proper time intervals between the two B decays. We obtain SK(0)(S)(pi(0)gamma) = -0.58(+0.46)(-0.38)(stat) +/- 0.11(syst) and AK(0)(S)(pi(0)gamma) = +0.03 +/- 0.34(stat) +/- 0.11(syst), for the K(0)(S)pi(0) invariant mass covering the full range up to 1.8 GeV/c2. We also measure the CP-violation parameters for the case B(0)-->K(*0)(-->K(0)(S)pi(0))gamma and obtain S(K(*0)gamma) = -0.79(+0.63)(-0.50)(stat) +/- 0.10(syst) for A(K(*0)gamma) fixed at 0.

Studies of proximity focusing RICH with an aerogel radiator using flat-panel multi-anode PMTs (Hamamatsu H8500)

Abstract A proximity focusing ring imaging Cherenkov detector using aerogel as the radiator has been studied for upgrading the Belle detector at the KEK-B-factory. We constructed a prototype Cherenkov counter using a 4×4 array of 64-channel flat-panel multi-anode PMTs (Hamamatsu H8500) with a large effective area. The aerogel samples were made with a new technique to obtain a higher transmission length at a high refractive index ( n =1.05). Multi-channel PMTs are read-out with analog memory chips. The detector was tested at the KEK-PS π 2 beam line in November, 2002. To evaluate systematically the performance of the detector, tests were carried out with various aerogel samples using pion beams with momenta between 0.5 and 4 GeV /c . The typical angular resolution was around 14 mrad , and the average number of detected photoelectrons was around 6. We expect that pions and kaons can be separated at a 4 σ level at 4 GeV /c .

Observation of B^+ ¿ ¿K^+

We report the first observation of the charmless hyperonic B decay, B+-->LambdaLambdaK+, using a 140 fb(-1) data sample recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB (e+)(e-) collider. The measured branching fraction is B(B+-->LambdaLambdaK+) = (2.91(+0.90)(-0.70) +/- 0.38) x 10(-6). We also perform a search for the related decay mode B+-->LambdaLambdapi+, but do not find a significant signal. We set a 90% confidence-level upper limit of B(B+-->LambdaLambdapi+) < 2.8 x 10(-6).

Measurement of polarization and triple-product correlations in B→K* decays

We present a measurement of the decay amplitudes and triple-product correlations in B ->phi K^* decays based on 140 fb^-1 of data recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB e^+ e^- storage ring. The decay amplitudes for the different phi K^* helicity states are measured from the angular distributions of final state particles in the transversity basis. The longitudinal and transverse complex amplitude moduli and angles are |A_0|^2 = 0.51 +- 0.06 +- 0.04, |A_perp|^2 = 0.24 +- 0.06 +- 0.03, arg(A_parallel) = -2.21 +- 0.22 +- 0.05 rad, and arg(A_perp) = 0.72 +- 0.21 +- 0.06 rad. The T-violating asymmetries through triple-product correlations are measured to be consistent with zero.

Observation of the D1(2420)→Dπ+π- decays

We report on the first observation of D{sub 1}{sup 0}(2420){yields}D{sup 0}{pi}{sup -}{pi}{sup +} and D{sub 1}{sup +}(2420){yields}D{sup +}{pi}{sup -}{pi}{sup +} decays (where the contribution from the dominant known D{sub 1}{yields}D*{pi} decay mode is excluded) in the B{sup -}{yields}D{sub 1}{sup 0}{pi}{sup -} and B{sup 0}{yields}D{sub 1}{sup +}{pi}{sup -} decays, respectively. The observation is based on 15.2x10{sup 7} BB events collected with the Belle detector at the KEKB collider. We also set 90% confidence level upper limits for the branching fractions of the four following decays: B{sup -}{yields}D{sub 1}{sup 0}{pi}{sup -}, D{sub 1}{sup 0}{yields}D*{sup 0}{pi}{sup -}{pi}{sup +}, B{sup 0}{yields}D{sub 1}{sup +}{pi}{sup -}, D{sub 1}{sup +}{yields}D{sup *+}{pi}{sup -}{pi}{sup +}, B{sup -}{yields}D{sub 2}*{sup 0}(2460){pi}{sup -}, D{sub 2}*{sup 0}{yields}D*{sup 0}{pi}{sup -}{pi}{sup +}, B{sup 0}{yields}D{sub 2}*{sup +}(2460){pi}{sup -}, D{sub 2}*{sup +}{yields}D{sup *+}{pi}{sup -}{pi}{sup +}.We report on the first observation of

Determination of /Vub/ from measurements of the inclusive charmless semileptonic partial rates of B mesons using full reconstruction tags.

D_1\to D\pi^+\pi^-

Measurement of γγ → pp̄ production at Belle

decays (where the contribution from the dominant known

Observation of B0→π0π0

D_1 \to D^* \pi

Study of B-+/--> DCPK +/- and (DCPK +/-)-K-* decays

decay mode is excluded) in the

Study of decay mechanisms in B-->Lambda(+)(c)p pi(-) decays and observation of low-mass structure in the Lambda(+)(c)p system

B\to D_1\pi