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Register a new userObservation of a new charged charmoniumlike state in B -> J/psi K pi decays
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We present the results of an amplitude analysis of anti-B0 -> J/psi K- pi+ decays. A new charged charmoniumlike state Zc(4200)+ decaying to J/psi pi+ is observed with a significance of 6.2 sigma. The mass and width of the Zc(4200)+ are 4196 +31-29 +17-13 MeV/c^2 and 370 +70-70 +70-132 MeV, respectively; the preferred assignment of the quantum numbers is J^P = 1^+. In addition, we find evidence for Zc(4430)+ -> J/psi pi+. The analysis is based on a 711 fb^-1 data sample collected by the Belle detector at the asymmetric-energy e+ e- collider KEKB.
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The decays $B^+rightarrow J/psi 3pi^+ 2pi^-$ and $B^+rightarrow psi(2S) pi^+pi^+pi^-$ are observed for the first time using a data sample corresponding to an integrated luminosity of $3.0fb^{-1}$, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV. The branching fractions relative to that of $B^+ rightarrow psi(2S)K^+$ are measured to be begin{eqnarray*} frac {mathcal{B}left(B^+rightarrow J/psi 3pi^+ 2pi^- right)} {mathcal{B}left(B^+ rightarrow psi(2S)K^+ right)} & = & left(1.88pm0.17pm0.09right)times10^{-2}, frac {mathcal{B}left(B^+rightarrow psi(2S) pi^+pi^+pi^- right)} {mathcal{B}left(B^+ rightarrow psi(2S)K^+ right)} & = & left(3.04pm0.50pm0.26right)times10^{-2}, end{eqnarray*} where the first uncertainties are statistical and the second are systematic.
An angular analysis of $B^0to J/psi K^+pi^-$ decays is performed, using proton-proton collision data corresponding to an integrated luminosity of 3~${rm fb}^{-1}$ collected with the LHCb detector. The $m(K^+pi^-)$ spectrum is divided into fine bins. In each $m(K^+pi^-)$ bin, the hypothesis that the three-dimensional angular distribution can be described by structures induced only by $K^ast$ resonances is examined, making minimal assumptions about the $K^+pi^-$ system. The data reject the $K^ast$-only hypothesis with a large significance, implying the observation of exotic contributions in a model-independent fashion. Inspection of the $m(J/psipi^-)$ versus $m(K^+pi^-)$ plane suggests structures near $m(J/psipi^-)=4200$~MeV and 4600~MeV.
We study the process e+e- to pi+pi-J/psi at a center-of-mass energy of 4.260 GeV using a 525 pb^{-1} data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross section is measured to be (62.9pm 1.9pm 3.7) pb, consistent with the production of the Y(4260). We observe a structure at around 3.9 GeV/c^2 in the pi^pm J/psi mass spectrum, which we refer to as the Z_c(3900). If interpreted as a new particle, it is unusual in that it carries an electric charge and couples to charmonium. A fit to the pi^pm J/psi invariant mass spectrum, neglecting interference, results in a mass of (3899.0pm 3.6pm 4.9) MeV/c^2 and a width of (46pm 10pm 20) MeV. Its production ratio is measured to be R=frac{sigma(e+e- to pi^pm Z_c(3900)^mp to pi+pi-J/psi))} {sigma(e+e- to pi+pi-J/psi)}=(21.5pm 3.3pm 7.5)%. In all measurements the first errors are statistical and the second are systematic.
The decay $B_crightarrow J/psi K^+ K^- pi^+$ is observed for the first time, using proton-proton collisions collected with the LHCb detector corresponding to an integrated luminosity of 3fb$^{-1}$. A signal yield of $78pm14$ decays is reported with a significance of 6.2 standard deviations. The ratio of the branching fraction of $B_c rightarrow J/psi K^+ K^- pi^+$ decays to that of $B_c rightarrow J/psi pi^+$ decays is measured to be $0.53pm 0.10pm0.05$, where the first uncertainty is statistical and the second is systematic.
We report the results of a search for the $B to Y(4260) K, ~Y(4260)to J/psipi^+pi^-$ decays. This study is based on a data sample corresponding to an integrated luminosity of 711~fb$^{-1}$, collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We investigate the $J/psipi^+pi^-$ invariant mass distribution in the range 4.0 to 4.6 GeV/$c^2$ using both $B^+ to J/psi pi^+pi^- K^+$ and $B^0 to J/psi pi^+pi^- K^0_S$ decays. We find excesses of events above the background levels, with a significances of 2.1 and 0.9 standard deviations for charged and neutral $B to Y(4260) K$ decays, respectively, taking into account the systematic uncertainties. These correspond to upper limits on the product of branching fractions, ${cal B}(B^+ to Y(4260) K^+) times {cal B}(Y(4260) to J/psi pi^+ pi^-) <1.4 times 10^{-5}$ and ${cal B}(B^0 to Y(4260) K^0) times {cal B}(Y(4260) to J/psi pi^+ pi^-) <1.7 times 10^{-5}$ at the 90% confidence level.
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