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Register a new userThe spectrum of radial, orbital and gluonic excitations of charmonium
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Authors
K. J. Juge
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We present results for the charmonium spectrum from $N_f=2$ dynamical QCD simulations on $12^3times 80$ anisotropic lattices. Using all-to-all propagators we determine the ground and excited states of S, P and D waves and hybrids. We also evaluate the disconnected (OZI suppressed) contribution to the $eta_c$ and $J/Psi$
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The charmonium system has several excited states below the energy threshold for decay into $D$ and $bar{D}$ mesons, which can in principle be studied accurately in lattice QCD. Studies that include many states in the spectrum have typically only been done at one value of the lattice spacing and with relatively heavy light quarks in the sea. Here we give preliminary results for radial and orbital excitation energies for charmonium from a calculation on 2+1+1 MILC configurations at multiple lattice spacings and including physical values for $u/d$ quark masses. We use the HISQ formulation for $c$ to obtain small discretisation errors and smeared operators to improve excited state overlap.
We measure glueball masses and the string tension in twelve-flavour QCD, aiming at comparing the emerging gluonic spectrum to the mesonic one. When approaching the critical surface at zero quark mass, the hierarchy of masses in the different sectors of the spectrum gives a new handle to determine the existence of an infrared fixed point. We describe the details of our gluonic measurements and the results obtained on a large number of gauge configurations generated with the HISQ action. In particular, we focus on the scalar glueball and its mixing with a flavour-singlet fermionic state, which is lighter than the pseudoscalar (would-be pion) state. The results are interesting in view of a light composite Higgs boson in walking technicolor theories.
This report discusses some recent investigations of the heavy hadron spectra using lattice QCD. The first half addresses multiple precision determinations of the masses of charm (and bottom) baryons. Recent lattice results in the tetraquark and the dibaryon sectors are also presented. The second half focuses on new exploratory studies of the excited charmonium spectra in the vector and scalar channels. Along the way, lattice results are compared with the experimental results, wherever they are available.
We present our final results for the excited charmonium spectrum from a quenched calculation using a fully relativistic anisotropic lattice QCD action. A detailed excited charmonium spectrum is obtained, including both the exotic hybrids (with $J^{PC} = 1^{-+}, 0^{+-}, 2^{+-}$) and orbitally excited mesons (with orbital angular momentum up to 3). Using three different lattice spacings (0.197, 0.131, and 0.092 fm), we perform a continuum extrapolation of the spectrum. We convert our results in lattice units to physical values using lattice scales set by the $^1P_1-1S$ splitting. The lowest lying exotic hybrid $1^{-+}$ lies at 4.428(41) GeV, slightly above the $D^{**}D$ (S+P wave) threshold of 4.287 GeV. Another two exotic hybrids $0^{+-}$ and $2^{+-}$ are determined to be 4.70(17) GeV and 4.895(88) GeV, respectively. Our finite volume analysis confirms that our lattices are large enough to accommodate all the excited states reported here.
We present a first study of the charmonium spectrum on N_f=2 dynamical, anisotropic lattices. We take advantage of all-to-all quark propagators to build spatially extended interpolating operators to increase the overlap with states not easily accessible with point propagators such as radially excited states of eta_c, psi, and chi_c, D-waves and hybrid states.
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