Search for B decays to final states with the eta_c meson

We report a search for $B$ decays to selected final states with the $eta_c$ meson: $B^{pm}to K^{pm}eta_cpi^+pi^-$, $B^{pm}to K^{pm}eta_comega$, $B^{pm}to K^{pm}eta_ceta$ and $B^{pm}to K^{pm}eta_cpi^0$. The analysis is based on $772times 10^6$ $Bbar{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We set 90% confidence level upper limits on the branching fractions of the studied $B$ decay modes, independent of intermediate resonances, in the range $(0.6-5.3)times 10^{-4}$. We also search for molecular-state candidates in the $D^0bar{D}^{*0}-bar{D}^0D^{*0}$, $D^0bar{D}^0+bar{D}^0D^0$ and $D^{*0}bar{D}^{*0}+bar{D}^{*0}D^{*0}$ combinations, neutral partners of the $Z(3900)^{pm}$ and $Z(4020)^{pm}$, and a poorly understood state $X(3915)$ as possible intermediate states in the decay chain, and set 90% confidence level upper limits on the product of branching fractions to the mentioned intermediate states and decay branching fractions of these states in the range $(0.6-6.9)times 10^{-5}$.

Study of B^{+-} -> K^{+-}(K_S K pi)^0 Decay and Determination of eta_c and eta_c(2S) Parameters

We report the results of a study of $B^{pm}to K^{pm}eta_c$ and $B^{pm}to K^{pm}eta_c(2S)$ decays followed by $eta_c$ and $eta_c(2S)$ decays to $(K_SKpi)^0$. The results are obtained from a data sample containing 535 million $Bbar{B}$-meson pairs collected by the Belle experiment at the KEKB $e^+e^-$ collider. We measure the products of the branching fractions ${mathcal B}(B^{pm}to K^{pm}eta_c){mathcal B}(eta_cto K_S K^{pm}pi^{mp})=(26.7pm 1.4(stat)^{+2.9}_{-2.6}(syst)pm 4.9(model))times 10^{-6}$ and ${mathcal B}(B^{pm}to K^{pm}eta_c(2S)){mathcal B}(eta_c(2S)to K_S K^{pm}pi^{mp})=(3.4^{+2.2}_{-1.5}(stat+model)^{+0.5}_{-0.4} syst))times 10^{-6}$. Interference with the non-resonant component leads to significant model uncertainty in the measurement of these product branching fractions. Our analysis accounts for this interference and allows the model uncertainty to be reduced. We also obtain the following charmonia masses and widths: $M(eta_c)=(2985.4pm 1.5(stat)^{+0.5}_{-2.0}(syst))$ MeV/$c^2$, $Gamma(eta_c)=(35.1pm 3.1(stat)^{+1.0}_{-1.6}(syst))$ MeV/$c^2$, $M(eta_c(2S))=(3636.1^{+3.9}_{-4.2}(stat+model)^{+0.7}_{-2.0}(syst))$ MeV/$c^2$, $Gamma(eta_c(2S))=(6.6^{+8.4}_{-5.1}(stat+model)^{+2.6}_{-0.9}(syst))$ MeV/$c^2$.