K0 SK 0 S production in two-photon collisions has been studied using a 397.6 fb −1 data sample collected with the Belle detector at the KEKB e+e− collider. For the first time the cross sections are measured in the two-photon center-of-mass energy range between 2.4 GeV and 4.0 GeV and angular range | cos θ∗| < 0.6. Combining the results with measurements of γγ → K+K− from Belle, we observe that the cross section ratio σ(K0 SK 0 S)/σ(K +K−) decreases from ∼0.13 to ∼0.01 with increasing energy. Signals for the χc0 and χc2 charmonium states are also observed.

A. Sokolov, M. Shapkin, K. Abe, K. Abe, I. Adachi, H. Aihara, D. Anipko, T. Aushev, 12 A. M. Bakich, E. Barberio, M. Barbero, I. Bedny, K. Belous, U. Bitenc, I. Bizjak, A. Bondar, M. Bračko, 13 T. E. Browder, A. Chen, W. T. Chen, B. G. Cheon, R. Chistov, Y. Choi, Y. K. Choi, S. Cole, J. Dalseno, M. Dash, A. Drutskoy, S. Eidelman, D. Epifanov, S. Fratina, T. Gershon, A. Go, G. Gokhroo, B. Golob, 13 H. Ha, J. Haba, T. Hara, Y. Hasegawa, K. Hayasaka, H. Hayashii, M. Hazumi, D. Heffernan, Y. Hoshi, S. Hou, W.-S. Hou, Y. B. Hsiung, T. Iijima, K. Inami, A. Ishikawa, R. Itoh, M. Iwasaki, Y. Iwasaki, J. H. Kang, P. Kapusta, N. Katayama, H. Kawai, T. Kawasaki, H. R. Khan, H. Kichimi, H. J. Kim, Y. J. Kim, S. Korpar, P. Križan, 13 P. Krokovny, R. Kulasiri, R. Kumar, A. Kuzmin, Y.-J. Kwon, T. Lesiak, A. Limosani, S.-W. Lin, D. Liventsev, F. Mandl, T. Matsumoto, S. McOnie, W. Mitaroff, H. Miyake, H. Miyata, Y. Miyazaki, T. Nagamine, Y. Nagasaka, I. Nakamura, E. Nakano, M. Nakao, Z. Natkaniec, S. Nishida, O. Nitoh, T. Nozaki, S. Ogawa, T. Ohshima, S. Okuno, Y. Onuki, H. Ozaki, H. Palka, C. W. Park, H. Park, L. S. Peak, R. Pestotnik, L. E. Piilonen, Y. Sakai, T. Schietinger, O. Schneider, C. Schwanda, A. J. Schwartz, R. Seidl, 33 M. E. Sevior, H. Shibuya, B. Shwartz, A. Somov, N. Soni, S. Stanič, H. Stoeck, T. Sumiyoshi, S. Suzuki, F. Takasaki, K. Tamai, N. Tamura, M. Tanaka, G. N. Taylor, Y. Teramoto, X. C. Tian, T. Tsukamoto, S. Uehara, T. Uglov, S. Uno, P. Urquijo, Y. Usov, G. Varner, S. Villa, C. C. Wang, Y. Watanabe, J. Wiechczynski, E. Won, C.-H. Wu, B. D. Yabsley, A. Yamaguchi, Y. Yamashita, M. Yamauchi, L. M. Zhang, Z. P. Zhang, V. Zhilich, and A. Zupanc

We report on a search for the lepton flavor violating τ−→μ−γ and τ−→e−γ decays based on 535 fb−1 of data accumulated at the Belle experiment. No signal is found and we set 90% confidence level upper limits on the branching ratios B(τ−→μ−γ)<4.5×10−8 and B(τ−→e−γ)<1.2×10−7.

We present results on the X(3872), produced in B^+ → X(3872) K^+ and B^0 → X(3872) K^0_S decays where X(3872) → J/ψπ^+ π^-. We report the first statistically significant observation of B^0 → X(3872) K^0_S and measure the ratio of branching fractions to be B(B^0 → X(3872)K^0)/ B(B^+ → X(3872)K^+) = 0.82 ± 0.22 ± 0.05, consistent with unity. The mass difference between the X(3872) states produced in B^+ and B^0 decay is found to be δ M ≡ M_XK^+ - M_XK^0 = (+0.18 ± 0.89 ± 0.26) MeV/c^2, consistent with zero. In addition, we search for the X(3872) in the decay B^0 → X(3872)K^+π^-, X(3872) → J/ψπ^+ π^-. We measure B(B^0 → X(3872) (K^+ π^-)_NR) × B(X(3872) → J/ψπ^+ π^-) = (8.1 ± 2.0 ^+1.1_-1.4)× 10^-6 and we set the 90 X(3872)K^*(892)^0) ×B(X(3872) →J/ψπ^+ π^-) < 3.4 ×10^-6. The analysis is based on a 605 fb^-1data sample collected at theΥ(4S)with the Belle detector at the KEKB collider.

We report measurements and searches for resonant B±→K±h→K±γγ decays where h is a η, η′, ηc, ηc(2S), χc0, χc2, J/ψ meson or the X(3872) particle. The results are based on a data sample containing 535 million BB¯ pairs collected with the Belle detector at the KEKB e+e− asymmetric-energy collider operating at the ϒ(4S) resonance. Signals are observed in the modes with η and η′, and we obtain evidence for a signal in the mode with ηc. We measure B(B±→K±η→K±γγ)=(0.87−0.15+0.16(stat)−0.07+0.10(syst))×10−6, B(B±→K±η′→K±γγ)=(1.40−0.15+0.16(stat)−0.12+0.15(syst))×10−6 and B(B±→K±ηc→K±γγ)=(0.22−0.07+0.09(stat)−0.02+0.04(syst))×10−6. We set upper limits on the branching fractions of the other modes.

It is shown that the difference in the distributions of positive (μ+) and negative charged leptons (μ−1) in reactions γγ → μ+μ−1 + νν and γγ → W±μ∓ + ν(ν) at √s > 200 GeV leads to observable charge asymmetry of muons which is sensitive to New Physics effects.

The neutral B-meson pair produced at the Upsilon(4S) should exhibit a non-local correlation of the type discussed by Einstein, Podolski, and Rosen (EPR). We measure this correlation using the time-dependent flavour asymmetry of semileptonic B0 decays, which we compare with predictions from quantum mechanics and two local realistic models. The data are consistent with quantum mechanics, and inconsistent with the other models. Assuming that some B pairs disentangle to produce B0 and B0bar with definite flavour, we find a decoherent fraction of 0.029+-057, consistent with no decoherence.

We present a measurement of the hadronic invariant mass squared (M-X(2)) spectrum in charmed semileptonic B meson decays B -> X(c)lv based on 140 fb(-1) of Belle data collected near the Y(4S) resonance. We determine the first, the second central, and the second noncentral moments of this spectrum for lepton energy thresholds ranging between 0.7 and 1.9 GeV. Full correlations between these measurements are evaluated.

Using 449x10(6) BB[over ] pairs collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider, we observe clear signals for B(+)-->K[over ](0)K(+) and B(0)-->K[over ](0)K(0) decays with 5.3sigma and 6.0sigma significance, respectively. We measure the branching fractions B(B(+)-->K[over ](0)K(+))=(1.22(-0.28-0.16)(+0.32+0.13))x10(-6) and B(B(0)-->K[over ](0)K(0))=(0.87(-0.20)(+0.25)+/-0.09)x10(-6), and partial-rate asymmetries A(CP)(B(+)-->K[over ](0)K(+))=0.13(-0.24)(+0.23)+/-0.02 and A(CP)(B(0)-->K[over ](0)K(0))=-0.58(-0.66)(+0.73)+/-0.04. From a simultaneous fit, we also obtain B(B(+)-->K(0)pi(+))=(22.8(-0.7)(+0.8)+/-1.3)x10(-6) and A(CP)(B(+)-->K(0)pi(+))=0.03+/-0.03+/-0.01. The first and second error in the branching fractions and the partial-rate asymmetries are statistical and systematic, respectively. No signal is observed for B(0)-->K(+)K(-) decays, and for this branching fraction, we set an upper limit of 4.1x10(-7) at the 90% confidence level.

We report a new measurement of the time-dependent CP-violating parameters in B(0)-->pi(+)pi(-) decays with 535 x 10(6) BB pairs collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider operating at the Upsilon(4S) resonance. We find 1464+/-65 B(0)-->pi(+)pi(-) events and measure the CP-violating parameters S(pipi)=-0.61+/-0.10(stat)+/-0.04(syst) and A(pipi)=+0.55+/-0.08(stat)+/-0.05(syst). We observe large direct CP violation with a significance greater than 5 standard deviations for any S(pipi) value. Using isospin relations, we measure the Cabibbo-Kobayashi-Maskawa quark-mixing matrix angle phi(2)=(97+/-11) degrees for the solution consistent with the standard model and exclude the range 11 degrees <phi(2)<79 degrees at the 95% confidence level.

We report the first observation of the decay B0→Ds+Λ p with a statistical significance of 6.6σ. We measure B(B0→Ds+Λp)=(2.9±0.7±0.5±0.4) ×10-5, where the first error is statistical, the second is systematic, and the third error comes from the uncertainty in B(Ds+→π+). The data used for this analysis was accumulated at the Υ(4S) resonance, using the Belle detector at the KEKB asymmetric-energy e+e- collider. The integrated luminosity of the data sample is 414fb-1, corresponding to 449×106 BB pairs. © 2007 The American Physical Society.

We reconstruct (B) over bar (0)-> Ds-D+ decays using a sample of 449x10(6) B (B) over bar pairs recorded by the Belle experiment, and measure the branching fraction to be B((B) over bar (0)-> Ds-D+)=[7.5 +/- 0.2(stat)+/- 0.8(syst)+/- 0.8(B(')s)]x10(-3). A search for the related decay (B) over bar (0)-> Ds+Ds- is also performed. Since we observe no statistically significant signal, an upper limit on the branching fraction is set at 3.6x10(-5) (90% C.L.).

We report the results of several studies of the Lambda(c)(+)pi(+)pi(-)X final state in continuum e(+)e(-) annihilation data collected by the Belle detector. An analysis of angular distributions in Lambda(c)(2880)(+)-->Sigma(c)(2455)(0,++)pi(+,-) decays strongly favors a Lambda(c)(2880)(+) spin assignment of 5/2 over 3/2 or 1/2. We find evidence for Lambda(c)(2880)(+)-->Sigma(c)(2520)(0,++)pi(+,-) decay and measure the ratio of Lambda(c)(2880)(+) partial widths Gamma(Sigma(c)(2520)pi)/Gamma(Sigma(c)(2455)pi)=0.225+/-0.062+/-0.025. This value favors the Lambda(c)(2880)(+) spin-parity assignment of 5/2(+) over 5/2(-). We also report the first observation of Lambda(c)(2940)(+)-->Sigma(c)(2455)(0,++)pi(+,-) decay and measure Lambda(c)(2880)(+) and Lambda(c)(2940)(+) mass and width parameters. These studies are based on a 553 fb(-1) data sample collected at or near the Upsilon(4S) resonance at the KEKB collider.