Session D14: Heavy Flavor and Exotic Hadrons

Live

The $X(3872)$ can be produced in $e^+e^-$ annihilation by the creation of $D^{*0}\bar D{}^{*0}$ from a virtual photon, followed by the rescattering of the charm mesons into $X(3872)$ and a photon. The cross section for $e^+e^-\to X(3872)\gamma$ has a narrow peak 2.2 MeV above the $D^{*0}\bar D {}^{*0}$ threshold. This peak is the result of a triangle singularity. We calculate the normalized cross section near the $D^{*0}\bar D{}^{*0}$ threshold. The calculated peak is large enough to be measured by the BESIII collaboration. The observation of this peak would provide strong evidence for the identification of the $X(3872)$ as a charm-meson molecule.   

Live

The cross section for $e^+ e^-$ annihilation into $D^{*0} \bar D{}^0 + \gamma$ at center-of-mass energies near the $D^{*0} \bar D{}^{*0}$ threshold has a threshold enhancement in $D^{*0} \bar D{}^0$ from the $X(3872)$ resonance. The Dalitz plot has a $\bar D{}^{*0}$ resonance band in the $\bar D{}^0 \gamma$ invariant mass and a narrow band in the $D^{*0} \bar D{}^0$ invariant mass from a charm-meson triangle singularity. In the projection of the Dalitz plot onto the $D^{*0} \bar D{}^0$ invariant mass, the peak from the triangle singularity is suppressed by the Schmid cancellation. The measurement of the cross section for $D^{*0} \bar D{}^0 +\gamma$ would allow an accurate prediction of the height of the peak from the triangle singularity in the cross section for $X(3872)+\gamma$.   

On Demand

The nature of the $Y(2175)$ (also known as the $\phi(2170)$) has remained elusive since it was observed at BaBar in 2006 and later confirmed independently by BES and Belle. Proposed interpretations of the state have included an excited $3\, ^{3}S_1$ and $2\, ^{3}D_1$ strangeonium state, molecular $\bar{\Lambda}\Lambda$ state, and $ss\bar{s}\bar{s}$ four-quark state. Additionally, the $Y(2175)$ has also been considered as an $\bar{s}Gs$ hybrid meson state; lattice results point to an expected vector strangeonium-like hybrid between $2.4-2.5\,\mathrm{GeV}$ at a reported $m_\pi = 396\,\mathrm{MeV}$. We consider whether a hybrid meson interpretation of the $Y(2175)$ is consistent within the framework of QCD sum rules. Using Gaussian sum rules, we use phenomenological inputs from measurements of the $Y(2175)$ to analyse correlation functions of composite operators corresponding to the $J^{PC} = 1^{--}$ strangeonium-like hybrid meson state, extending the calculation from previous sum rule results. We find that the optimized sum rule predicts no significant hybrid content in the $Y(2175)$ state.   

On Demand

In order to search for the existence of exotic hybrid mesons, the GlueX experiment, at Jefferson Lab, utilizes a linearly polarized photon beam at $E_\gamma =$ 8-9 GeV to map the spectrum of light mesons. A particular interest has been placed on the $\pi^0 \eta$ and $\pi^0 \eta'$ systems, as an observation of odd angular momentum L waves in this final state may indicate the presence of exotic quantum numbers. By comparing both systems, the role of flavor symmetry should be illuminated as to allow for a better understanding of meson production mechanisms. We will present preliminary results from initial studies of these channels from more than four petabytes of data recorded by the GlueX experiment, and compare the results to previous experimental observations of the same channels.   

On Demand

In the $m_Q\rightarrow\infty$ limit, the hyperfine splittings in the ground state doubly heavy baryons $\left(QQq\right)$ and single heavy antimesons $(\bar{Q}q)$ are related by heavy quark-diquark symmetry (HQDQ) as the light degrees of freedom in both the hadrons are expected to have identical configurations. In this talk, I will point out the existence of perturbative and nonperturbative corrections to the HQDQ symmetry hyperfine splitting relation that scale as ${\cal O}\left(\alpha_s^2\right)$ and $\Lambda_{\rm QCD}^2/m_Q^2$ respectively. In the extreme heavy quark limit, the perturbative corrections to hyperfine splitting of doubly charm or bottom baryons are a few percent or smaller. The nonperturbative corrections to hyperfine splitting are of order $10\%$ in the case of doubly charm baryons and $1\%$ or smaller in doubly bottom baryons.   

On Demand

We study the scattering of J/$\Psi $ - J/$\Psi $ mesons using quadratic and Cornell potentials in our tetraquark ($c\bar{{c}}c\bar{{c}}$ ) system. The state vector of the system in the restricted gluonic basis is written by using adiabatic approximation and Hamiltonian is written via quark potential model. Resonating group technique is used to get the integral equations which are solved to get the unknown inter-cluster dependence of the total wavefunction of our tetraquark system. From the solutions, T-Matrix elements are calculated and eventually the scattering cross sections are obtained using the two potentials respectively. We compare these cross sections and find that the magnitude of scattering cross sections of quadratic potential is higher than Cornell potential.   

Not Participating

Relativistic heavy ion collisions provide an excellent venue to produce some of the recently observed and theoretically proposed exotic states because they contain heavy quarks, which are profusely produced in these experiments. After a short introduction on the general features in the production of resonance, light nuclei and exotic hadrons from a heavy ion collision, I will discuss why the production rate of an exotic state could discriminate its structure between a compact multiquark state and a molecular configuration. The work on the production rate is done in collaboration with the ExHIC collaboration.   

Not Participating

Heavy flavor baryon spectroscopy provides insights into production and binding mechanisms of hadrons and the properties of QCD that are not very well understood. For doubly-charmed baryons, SELEX originally reported observations of $\Xi_{cc}^{+}$ and $\Xi_{cc}^{++}$, at masses of 3519 MeV/$c^2$ and 3620 MeV/$c^2$ respectively. LHCb reported the observation of $\Xi_{cc}^{++}$ with a mass of 3621 MeV/$c^2$. We report on the status of a search for doubly charmed baryons using 1.96 TeV $p\bar{p}$ data using the CDF detector at the Fermilab Tevatron. Using the displaced-track trigger, we perform this search using 5- and 6-charged track final states. Complementary modes are used for calibration and normalization.   

Not Participating

We present an analysis of the inclusive semielectronic decay of the $D_s$ meson using data collected with the BESIII detector at the BEPCII storage ring in Beijing, China. Our data sample consists of an integrated luminosity of $3.19 \text{ fb}^{-1}$ of $e^+e^-$ annihilations collected at $E_{CM}=4.178 \text{ GeV}$, at which energy $D_s$ production is maximal, with a $\sim 1$ nb cross section for $e^+e^- \rightarrow D_sD_s^*$. We employ a tagged analysis with the use of particle identification and tracking matrix unfolding procedures to obtain our result. An input/output check with a Monte Carlo sample 5 times larger than data demonstrates the validity of our analysis procedure. Our principal results are the world’s most precise measurement of the $D_s$ meson semielectronic branching fraction, improved constraints on the rates for hitherto unobserved exclusive semielectronic modes and the ratio of $D_s$ and $D^0$ semielectronic widths. Prospects for additional studies of inclusive semileptonic $D_s$ decays with BESIII will also be described.