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Register a new userSpectroscopy and lifetime of bottom and charm hadrons
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Fumihiko Ukegawa
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We review recent experimental results on spectroscopy and lifetime of bottom and charm hadrons.
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We report on recent results in spectroscopy from BaBar. This includes the discovery of a new $Lambda_c$ baryon, detailed studies of the $D^*_{sJ}(2317)^+$, $D_{sJ}(2460)^+$, X(3872) and Y(4260) particles and the first measurement of hadronic non-$Bbar{B}$ decays of the $Upsilon(4S)$ meson.
We report on mass and lifetime measurements of several ground state charmed and bottom baryons, using a data sample corresponding to 9.6 $textrm{fb}^{-1}$ from $pbar p$ collisions at $sqrt{s}=1.96$ TeV, and recorded with the Collider Detector at Ferm
ilab. Baryon candidates are reconstructed from data collected with an online event selection designed for the collection of long-lifetime heavy-flavor decay products and a second event selection designed to collect $J/psi rightarrow mu^+ , mu^-$ candidates. First evidence for the process $Omega_b^- rightarrow Omega_c^0 , pi^-$ is presented with a significance of $3.3sigma$. We measure the following baryon masses: begin{eqnarray} M(Xi_c^{0}) = 2470.85pm0.24(stat)pm0.55(syst) , MeV/c^2, onumber M(Xi_c^{+}) = 2468.00pm0.18(stat)pm0.51(syst) , MeV/c^2, onumber M(Lambda_b) = 5620.15pm0.31(stat)pm0.47(syst) , MeV/c^2, onumber M(Xi_b^-) = 5793.4pm1.8(stat)pm0.7(syst) , MeV/c^2, onumber M(Xi_b^0) = 5788.7pm4.3(stat)pm1.4(syst) , MeV/c^2, , and onumber M(Omega_b^-) = 6047.5pm3.8(stat)pm0.6(syst) , MeV/c^2. onumber end{eqnarray} The isospin splitting of the $Xi_b^{-,0}$ states is found to be $M(Xi_b^-)-M(Xi_b^0)=4.7pm4.7(stat)pm0.7(syst)$ MeV/$c^2$. The isospin splitting of the $Xi_c^{0,+}$ states is found to be $M(Xi_c^0)-M(Xi_c^+)$ = $2.85pm0.30(stat)pm0.04(syst)$ MeV/$c^2$. The following lifetime measurements are made: begin{eqnarray} tau(Lambda_b) = 1.565pm0.035(stat)pm0.020(syst) , ps, onumber tau(Xi_b^-) = 1.32pm0.14(stat)pm0.02(syst) , ps, onumber tau(Omega_b^-) = 1.66^{+0.53}_{-0.40}(stat)pm0.02(syst) , ps. onumber end{eqnarray}
LHCb continues to expand its world-leading sample of charmed hadrons collected during LHCs Run 1 (2010-2012) and Run 2 (2015-present). This sample is yielding some of the most stringent tests of the Standard Model understanding of charm physics. This includes precise measurements of the neutral D-meson mixing parameters and some of the most sensitive searches for direct and indirect CP violation in charm interactions.
We search for new charmless decays of neutral $b$--hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using a data sample corresponding to 1 fb$^{-1}$ of integrated luminosity, we report the first observation of the BsKpi decay, with a significance of $8.2sigma$, and measure $BR(BsKpi) = (5.0 pm 0.7stat pm 0.8syst)times 10^{-6}$. We also report the first observation of charmless $b$--baryon decays in the channels Lbppi and LbpK with significances of $6.0sigma$ and $11.5sigma$ respectively, and we measure $BR(Lbppi) = (3.5 pm 0.6stat pm 0.9syst)times 10^{-6}$ and $BR(LbpK) = (5.6 pm 0.8stat pm 1.5syst)times 10^{-6}$. No evidence is found for the decays BdKK and Bspipi, and we set an improved upper limit $BR(Bspipi) < 1.2times 10^{-6}$ at the 90% confidence level. All quoted branching fractions are measured using $BR(BdKpi)$ as a reference.
We investigate heavy quark symmetries for heavy light meson-antimeson systems in a contact-range effective field theory. In the SU(3) light flavor limit, the leading order Lagrangian respecting heavy quark spin symmetry contains four independent counter-terms. Neglecting $1/m_Q$ corrections, three of these low energy constants can be determ1ined by theorizing a molecular description of the $X(3872)$ and $Z_b(10610)$ states. Thus, we can predict new hadronic molecules, in particular the isovector charmonium partners of the $Z_b(10610)$ and the $Z_b(10650)$ states. We also discuss hadron molecules composed of a heavy meson and a doubly-heavy baryon, which would be related to the heavy meson-antimeson molecules thanks to the heavy antiquark-diquark symmetry. Finally, we also study the $X(3872) to D^0bar D^0pi^0$ decay, which is not only sensitive to the short distance part of the $X(3872)$ molecular wave function, as the $J/psipipi$ and $J/psi3pi$ $X(3872)$ decay modes are, but it is also affected by the long-distance structure of the resonance. Furthermore, this decay might provide some information on the interaction between the $Dbar D$ charm mesons.
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