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Register a new user$B_c to J/psi$ helicity form factors and the $B_c^+ to J/psi+(P, V, ell^+ u_ell)$ decays
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In this paper, we calculate the $B_cto J/psi$ helicity form factors (HFFs) up to twist-4 accuracy by using the light-cone sum rules approach. After extrapolating those HFFs to the physically allowable $q^2$ region, we investigate the $B^+_c$-meson two-body decays and semi-leptonic decays $B_c^+ to J/psi+(P, V, ell^+ u_ell)$, where $P$ and $V$ stand for a light pseudo-scalar meson and a vector meson, respectively. The branching fractions can be derived by using the CKM matrix element and the $B_c$ lifetime from the Particle Data Group, and we obtain ${cal B}(B_c^+ to J/psi pi^+)=(0.132^{+0.002}_{-0.002})%$, ${cal B}(B_c^+ to J/psi K^+)=(0.010^{+0.000}_{-0.000})%$, ${cal B}(B_c^+ to J/psi rho^+) =(0.755^{+0.030}_{-0.034})%$, ${cal B}(B_c^+ to J/psi K^{ast +})=(0.043^{+0.001}_{-0.001})%$, ${cal B}(B_c^+ to J/psi mu^+ u_mu)=(2.808^{+0.547}_{-0.704})%$ and ${cal B}(B_c^+ to J/psi tau^+ u_tau)=(0.563^{+0.137}_{-0.178})%$. We then obtain ${cal R}_{pi^+/mu^+ u_mu} = 0.047^{+ 0.009}_{-0.012}$ and ${cal R}_{K^+ / pi^+} = 0.075^{+0.005}_{-0.005}$, which agree with the LHCb measured value within $1sigma$-error. We also obtain ${cal R}_{J/psi}=0.200^{+ 0.062}_{-0.081}$, which like other theoretical predictions, are consistent with the LHCb measured value within $2sigma$-error.
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Measurements of $B_c^+$ production and mass are performed with the decay mode $B_c^+ to J/psi pi^+$ using 0.37 fb$^{-1}$ of data collected in $pp$ collisions at $sqrt{s}=7$ TeV by the LHCb experiment. The ratio of the production cross-section times branching fraction between the $B_c^+ to J/psi pi^+$ and the $B^+ to J/psi K^+$ decays is measured to be $(0.68 pm 0.10,({rm stat.}) pm 0.03,({rm syst.}) pm 0.05,({rm lifetime}))$% for $B_c^+$ and $B^+$ mesons with transverse momenta $p_{rm T}>4 $GeV/$c$ and pseudorapidities $2.5<eta<4.5$. The $B_c^+$ mass is directly measured to be $6273.7 pm 1.3,({rm stat.}) pm 1.6 ,({rm syst.})$ MeV/$c^2$, and the measured mass difference with respect to the $B^+$ meson is $M(B_c^+)-M(B^+) = 994.6 pm 1.3,({rm stat.}) pm 0.6,({rm syst.})$ MeV/$c^2$.
We study the semileptonic decay of the $B_c (0^-)$ to charmonia through the bottom-to-charm-quark electroweak current in the framework of basis light-front quantization. Explicitly, we calculate the weak transition form factors for processes of $B_c$ decaying into $eta_c$ or $J/psi$ based on the corresponding initial and final valence light-front wave functions both obtained from the basis light-front quantization. We also present the corresponding differential decay width and branching ratios, as well as the branching ratios for decays into the $eta_c$ and the $psi$. We observe unphysical frame dependence of the calculated form factors, which is attributed to only including the valence light-front wave functions. Based on the analysis of current component, we propose a preferred set of frames to calculate these form factors.
An amplitude analysis of flavour-untagged $B_s^0 to J/psi p bar{p}$ decays is performed using a sample of $797pm31$ decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9 $text{fb}^{-1}$. Evidence for a new structure in the $J/psi p$ and $J/psi bar{p}$ systems with a mass of $4337 ^{+7}_{-4} ^{+2}_{-2}~text{MeV}$ and a width of $29 ^{+26}_{-12} ^{+14}_{-14}~text{MeV}$ is found, where the first uncertainty is statistical and the second systematic, with a significance in the range of 3.1 to 3.7 $sigma$, depending on the assigned $J^P$ hypothesis.
The data sample of $Lambda_b^0to J/psi p K^-$ decays acquired with the LHCb detector from 7 and 8~TeV $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$, is inspected for the presence of $J/psi p$ or $J/psi K^-$ contributions with minimal assumptions about $K^- p$ contributions. It is demonstrated at more than 9 standard deviations that $Lambda_b^0to J/psi p K^-$ decays cannot be described with $K^- p$ contributions alone, and that $J/psi p$ contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for $P_c^+to J/psi p$ charmonium-pentaquark states in the same data sample.
Evidence is presented for the decay $B_c+rightarrow J/psi 3pi^+2pi^-$ using proton-proton collision data, corresponding to an integrated luminosity of 3fb$^{-1}$, collected with the LHCb detector. A signal yield of $32pm8$ decays is found with a significance of 4.5 standard deviations. The ratio of the branching fraction of the $B_c^+rightarrow J/psi 3pi^+ 2pi^-$ decay to that of the $B_c^+ rightarrow J/psi pi^+$ decay is measured to be $$ frac{Br (B_c^+ rightarrow J/psi 3pi^+2pi^)}{Br (B_c^+ rightarrow J/psi pi^+)} = 1.74pm0.44pm0.24, $$ where the first uncertainty is statistical and the second is systematic.
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