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Person# Lei Li

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Tagir Aushev, Yixing Chen, Sun Hee Kim, Donghyun Kim, Lei Li, Yiming Li, Olivier Schneider, Mingkui Wang

We present the results of the first Dalitz plot analysis of the decay D-0 -> K-pi(+)eta. The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb(-1) collected by the Belle detector at the asymmetric-energy e(+)e(-) KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels (K) over bar*(892)(0)eta, K(-)a(0)(980)(+), K(-)a(2)(1320)+, K(-)a(2)(1410)(0)eta, K*(1680)(-)pi(+) and K-2*(1980)(-)pi(+), together with K pi and eta K eta S-wave components. The decays K* (1680)(-)-> K-eta and K-2* (1980)--> K-eta are observed for the first time. We measure ratio of the branching fractions, B(D-0 -> K-pi(+)eta)/B(D-0 -> K-pi(+)) = 0.500 +/- 0.002(stat) +/- 0.020(syst) +/- 0.003(B-PDG). Using the Dalitz fit result, the ratio B(K*(1680)-> K eta)/B(K*(1680)-> K pi) is measured to be 0.11 +/- 0.002(stat)(-0.04)(+0.06)(syst) +/- 0.04(B-PDG); this is much lower than the theoretical expectations (approximate to 1) made under the assumption that K*(1680) is a pure 1(3)D(1) state. The product branching fraction B(D-0 -> [K-2*(1980)- -> K-eta]pi(+)) = (2.2-1.9+1.7) x 10(-4) is determined. In addition, the pi eta' contribution to the a(0)(980)(+/-) resonance shape is confirmed with 10.1 sigma statistical significance using the three-channel Flatte model. We also measure B(D-0 -> (K) over bar*(892)(0)eta) = (1.41(-0.12)(+0.13))%. This is consistant with, and more precise than, the current world average (1.02 +/- 0.30)%, deviates with a significance of more than 3 sigma from the theoretical predictions of (0.51-0.92)%.

Donghyun Kim, Lei Li, Yiming Li, Olivier Schneider, Mingkui Wang, Xiao Wang

The first dedicated search for the eta(c2)(1D) is carried out using the decays B+-> eta(c2)(1D)K+, B-0 -> eta(c2)(1D)KS0 with eta(c2)(1D) -> h(c)gamma. No significant signal is found. For the eta(c2)(1D) mass range between 3795 and 3845 MeV/c(2), the branching-fraction upper limits are determined to be & x212c;(B+-> eta(c2)(1D)K+) x & x212c;(eta(c2)(1D) -> h(c)gamma) < 3.7 x 10(-5), & x212c;(B-0 -> eta(c2)(1D)K-0) x & x212c;(eta(c2)(1D) -> h(c)gamma) < 3.5 x 10(-5), & x212c;(B-0 -> eta(c2)(1D)pi K--(+)) x & x212c;(eta(c2)(1D) -> h(c)gamma) < 1.0 x 10(-4), and & x212c;(B+-> eta(c2)(1D)pi(+)KS0) x & x212c;(eta(c2)(1D) -> h(c)gamma) < 1.1 x 10(-4) at 90% C.L. The analysis is based on the 711 fb(-1) data sample collected on the & x3d2;(4S) resonance by the Belle detector, which operated at the KEKB asymmetric-energy e(+)e(-) collider.

2020, , , , , ,

We present measurements of the branching fractions for the decays B -> K mu(+)mu(-) and B -> Ke(+)e(-), and their ratio (R-K), using a data sample of 711 fb(-1) that contains 772 x 10(6) B (B) over bar events. The data were collected at the Gamma(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The ratio RK is measured in five bins of dilepton invariant-mass-squared (q(2)): q(2) is an element of (0.1, 4.0), (4.00, 8.12), (1.0, 6.0), (10.2, 12.8) and (> 14.18) GeV2/c(4), along with the whole q(2) region. The R-K value for q(2) is an element of (1.0, 6.0) GeV2/c(4) is 1.03(-0.24)(+0.28) +/- 0.01. The first and second uncertainties listed are statistical and systematic, respectively. All results for R-K are consistent with Standard Model predictions. We also measure CP-averaged isospin asymmetries in the same q(2) bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q(2) is an element of (1.0, 6.0) GeV2/c(4) bin in the mode with muon final states. The measured differential branching fractions, dB/dq(2), are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B -> K mu(+/-)e(-/+) decays and set 90% confidence-level upper limits on the branching fraction in the range of 10(-8) for B+ -> K+ mu(+/-)e(-/+), and B-0 -> K-0 mu(+/-) e(-/+) modes.