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Register a new userStudy of orbitally excited $B$ mesons and evidence for a new $Bpi$ resonance
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Using the full CDF Run II data sample, we report evidence for a new resonance, which we refer to as $B(5970)$, found simultaneously in the $B^0pi^+$ and $B^+pi^-$ mass distributions with a significance of 4.4 standard deviations. We further report the first study of resonances consistent with orbitally excited $B^{+}$ mesons and an updated measurement of the properties of orbitally excited $B^0$ and $B_s^0$ mesons. We measure the masses and widths of all states, as well as the relative production rates of $B_1$, $B_2^*$, and $B(5970)$ states and the branching fraction of the $B_{s2}^{*0}$ state to either $B^{*+} K^-$ and $B^{+} K^-$. Furthermore, we measure the production rates of the orbitally excited $B^{0,+}$ states relative to the $B^{0,+}$ ground state. The masses of the new $B(5970)$ resonances are $5978pm5(textrm{stat})pm12(textrm{syst}) textrm{ MeV/c}^{2}$ for the neutral state and $5961pm5(textrm{stat})pm12(textrm{syst}) textrm{ MeV/c}^{2}$ for the charged state, assuming that the resonance decays into $Bpi$ final states. The properties of the orbitally excited and the new $B(5970)^{0,+}$ states are compatible with isospin symmetry.
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The BaBar Collaboration has recently reported branching fractions for semileptonic decays of the $B$ meson into final states with charged and neutral $D_{1}(2420)$ and $D_{2}^{ast}(2460)$, two narrow orbitally excited charmed mesons. We evaluate these branching fractions within the framework of a constituent quark model in two steps, one which involves a semileptonic decay and the other one mediated by a strong process. Our results are in agreement with the experimental data.
Using 980 $fb^-1$ of data collected with the Belle detector operating at the KEKB asymmetric-energy e^+e^- collider, we report a study of the electromagnetic decays of excited {charmed baryons} $Xi_c(2790)$ and $Xi_c(2815)$. A clear signal (8.6 standard deviations) is observed for $Xi_c(2815)^0 to Xi_c^0gamma$, and we measure: $B[Xi_c(2815)^0 to Xi_c^0gamma]/B[Xi_c(2815)^0 to Xi_c(2645)^+pi^- to Xi_c^0pi^+pi^-] = 0.41 pm 0.05 pm 0.03$. We also present evidence (3.8 standard deviations) for the similar decay of the $Xi_c(2790)^0$ and measure: $B[Xi_c(2790)^{0}toXi_c^{0}gamma]/B[Xi_c(2790)^0toXi_c^{prime +}pi^{-}toXi_c^{+}gamma pi^-] = 0.13 pm 0.03 pm 0.02$. The first quoted uncertainties are statistical and the second systematic. We find no hint of the analogous decays of the $Xi_c(2815)^+$ and $Xi_c(2790)^+$ baryons and set upper limits at the 90% confidence level of: $B[Xi_c(2815)^{+}toXi_c^{+}gamma]/B[Xi_c(2815)^+toXi_c(2645)^0pi^+toXi_c^+pi^-pi^+] < 0.09,$ and $B[Xi_c(2790)^{+}toXi_c^{+}gamma]/B[Xi_c(2790)^+toXi_c^{prime 0}pi^{+}toXi_c^{0}gamma pi^+] < 0.06.$ Approximate values of the partial widths of the decays are extracted, which can be used to discriminate between models of the underlying quark structure of these excited states.
We calculate the two-body strong decays of the orbitally excited scalar mesons $D_0^*(2400)$ and $D_J^*(3000)$ by using the relativistic Bethe-Salpeter (BS) method. $D_J^*(3000)$ was observed recently by the LHCb Collaboration, the quantum number of which has not been determined yet. In this paper, we assume that it is the $0^+(2P)$ state and obtain the transition amplitude by using the PCAC relation, low-energy theorem and effective Lagrangian method. For the $1P$ state, the total widths of $D_0^*(2400)^{0}$ and $ D_0^*(2400)^+$ are 226 MeV and 246 MeV, respectively. With the assumption of $0^+(2P)$ state, the widths of $D_J^*(3000)^0$ and $D_J^*(3000)^+$ are both about 131 MeV, which is close to the present experimental data. Therefore, $D_J^*(3000)$ is a strong candidate for the $2^3P_0$ state.
Decays of the Y(5S) resonance to channels with B^+ and B^0 mesons are studied using a 23.6 fb^-1 data sample collected on the Y(5S) resonance with the Belle detector at the KEKB asymmetric energy e^+ e^- collider. The fully reconstructed B^+ -> J/psi K^+, B^0 -> J/psi K^{*0}, B^+ -> bar_D^0 pi^+ and B^0 -> D^- pi^+ decays are used to obtain the B^+ and B^0 production rates per bb_bar event, f(B^+) = (67.5 pm 3.6 pm 4.8)% and f(B^0)=(70.4^{+5.2}_{-5.1} pm 6.2)%$. Assuming equal rates to B^+ and B^0 mesons in all channels produced at the Y(5S) energy, we measure the fractions for bb_bar event transitions to the two-body and multi-body channels with B^{+/0} meson pairs, f(Bbar{B}) = (5.1 pm 0.9 pm 0.4)%, f(Bbar{B}^*+B^*bar{B}) = (12.6^{+1.2}_{-1.1} pm 1.0)%, f(B^*bar{B}^*) = (34.5^{+1.9}_{-1.8} pm 2.7)%, f(B^{(*)}bar{B}^{(*)}pi(pi)) = (16.4^{+1.6}_{-1.5} pm 1.2)%, f(Bbar{B} pi) = (0.0 pm 1.1 pm 0.2)%, f(Bbar{B}^*pi+B^*bar{B}pi) = (6.8^{+2.1}_{-2.0} pm 0.7)%, and f(B^*bar{B}^*pi) = (1.0^{+1.3}_{-1.2} pm 0.3)%.
We compute the B^*Bpi coupling hat{g}_{infty} for static heavy-light meson using all-to-all propagators. It is shown that low-mode averaging with 100 low-lying eigenmodes indeed improves the signal for the 2-point and 3-point functions for heavy-light meson significantly. Our study suggests that the all-to-all propagator will be a very efficient method for high precision computation of the B^*Bpi coupling especially in unquenched QCD where the number of configurations is limited.
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