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Register a new userObservation of candidate exotic mesons containing heavy quarks with Belle
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S.-K.Choi
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We report the observation of two resonance-like structures in the $pi^+ chi_{c1}$ invariant mass distribution near 4.1 GeV in exclusive $Bto Kpi^+chi_{c1}$ decays. A detailed Dalitz-plot analysis demonstrates that these structures cannot be produced by reflections from any known and possibly unknown resonances in the $Kpi$ channel. If these two peaks are produced by resonances in the $pi^+chi_{c1}$ channel, their minimal quark structure would have to be a $cbar{c}ubar{d}$ tetraquark arrangement, similar to that proposed for the $Z^+(4430)$ structure reported by Belle last year in the $pi^+psi^{}$ mass distribution produced in $Bto Kpi^+psi^{}$ decays. In addition, we report some new measurements on the properties of the X(3872) meson and the $1^{--}$ $Y$ states that are produced with initial state radiation. %and also other latest XYZ results. The analyses are based on a large data sample recorded at the $Upsilon(4S)$ resonances and nearby continuum with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider.
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The primary motivation of the GlueX experiment is to search for and ultimately study the pattern of gluonic excitations in the meson spectrum produced in $gamma p$ collisions. Recent lattice QCD calculations predict a rich spectrum of hybrid mesons that have both exotic and non-exotic $J^{PC}$, corresponding to $qbar{q}$ states ($q=u,$ $d,$ or $s$) coupled with a gluonic field. A thorough study of the hybrid spectrum, including the identification of the isovector triplet, with charges 0 and $pm1$, and both isoscalar members, $|sbar{s} >$ and $|ubar{u} > + |dbar{d} >$, for each predicted hybrid combination of $J^{PC}$, may only be achieved by conducting a systematic amplitude analysis of many different hadronic final states. Detailed studies of the performance of the gx detector have indicated that identification of particular final states with kaons is possible using the baseline detector configuration. The efficiency of kaon detection coupled with the relatively lower production cross section for particles containing hidden strangeness will require a high intensity run in order for analyses of such states to be feasible. We propose to collect a total of 200 days of physics analysis data at an average intensity of $5times 10^7$ tagged photons on target per second. This data sample will provide an order of magnitude statistical improvement over the initial GlueX running, which will allow us to begin a program of studying mesons and baryons containing strange quarks. In addition, the increased intensity will permit us to study reactions that may have been statistically limited in the initial phases of GlueX. Overall, this will lead to a significant increase in the potential for gx to make key experimental advances in our knowledge of hybrid mesons and excited $Xi$ baryons.
We study the spectra of heavy-light and heavy-heavy mesons containing charm quarks, including higher spin states. We use two sets of $N_f = 2 + 1$ gauge configurations, one set from QCDSF using the SLiNC action, and the other configurations from the Budapest-Marseille-Wuppertal collaboration, using the HEX smeared clover action. To extract information about the excited states, we choose a suitable basis of operators to implement the variational method.
Some of the currently most popular conjectures for the structure of the recently discovered heavy mesons that do not find a place in the quark model quarkonium spectrum are sketched. Furthermore, some observables are identified that should allow one to identify the most prominent components of individual states.
In this work, we evaluate the energy spectra of baryons which consist of two heavy and one light quarks in the MIT bag model. The two heavy quarks constitute a heavy scalar or axial vector diquark. Concretely, we calculate the spectra of $|q(QQ)>_{1/2}$ and $|q(QQ)>_{3/2}$ where $Q$ and $Q$ stand for $b$ and/or $c$ quarks. Especially, for $|q(bc)>_{1/2}$ there can be a mixing between $|q(bc)_0>_{1/2}$ and $|q(bc)_1>_{1/2}$ where the subscripts 0 and 1 refer to the spin state of the diquark (bc), the mixing is not calculable in the framework of quantum mechanics (QM) as the potential model is employed, but can be evaluated by the quantum field theory (QFT). Our numerical results indicate that the mixing is sizeable
We report on a search for heavy neutrinos in B-meson decays. The results are obtained using a data sample that contains 772x10^6 BB-bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. No signal is observed and upper limits are set on mixing of heavy neutrinos with left-handed neutrinos of the Standard Model in the mass range 0.5 - 5.0 GeV/c^2.
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