39191409
Charmonium spectroscopy from an anisotropic lattice study
We present a progress report on our study of the charmonium spectrum in full QCD on anisotropic lattices generated by the Hadron Spectrum Collaboration. We adopt a large basis of interpolating operators to extract the excited charmonium states using the variational method. A detailed spectrum of excited charmonium mesons in many J PC channels is obtained. Hybrid states with exotic and non-exotic quantum numbers are determined and preliminary results from a study of disconnected contributions to the hc are presented.
11641258
Charmed Hadron Interactions
We compute the scattering lengths of charmed mesons and charmonia scattering with light hadrons in full QCD. We use Fermilab formulation for the charm quark and domain-wall fermions for the light quarks and staggered sea quarks. Four different light-quark masses are used to extrapolate to the physical point. The charmed baryon spectrum is also presented.
119269752
Singly and Doubly Charmed $J=1/2$ Baryon Spectrum from Lattice QCD
We compute the masses of the singly and doubly charmed baryons in full QCD using the relativistic Fermilab action for the charm quark. For the light quarks we use domain-wall fermions in the valence sector and improved Kogut-Susskind sea quarks. We use the low-lying charmonium spectrum to tune our heavy-quark action and as a guide to understanding the discretization errors associated with the heavy quark. Our results are in good agreement with experiment within our systematics. For the {Xi}{sub cc}, we find the isospin-averaged mass to be M{sub {Xi}{sub c{sub c}}}=3665{+-}17{+-}14{sub -78}{sup +0} MeV; the three given uncertainties are statistical, systematic, and an estimate of lattice discretization errors, respectively. In addition, we predict the mass splitting of the (isospin-averaged) spin-1/2 {Omega}{sub cc} with the {Xi}{sub cc} to be M{sub {Omega}{sub c{sub c}}}-M{sub {Xi}{sub c{sub c}}}=98{+-}9{+-}22{+-}13 MeV (in this mass splitting, the leading discretization errors are also suppressed by SU(3) symmetry). Combining this splitting with our determination of M{sub {Xi}{sub c{sub c}}} leads to our prediction of the spin-1/2 {Omega}{sub cc} mass, M{sub {Omega}{sub c{sub c}}}=3763{+-}19{+-}26{sub -79}{sup +13} MeV.
204005840
Quenched charmed meson spectra using tadpole improved quark action on anisotropic lattices
Charmed meson charmonium spectra are studied with improved quark actions on anisotropic lattices. We measured the pseudo-scalar and vector meson dispersion relations for four lowest lattice momentum modes with quark mass values ranging from the strange quark to charm quark with three different values of gauge coupling β and four different values of bare speed of light ν. With the bare speed of light parameter ν tuned in a mass-dependent way, we study the mass spectra of D, Ds, ηc, D*, Ds* and J/ψ mesons. The results extrapolated to the continuum limit are compared with the experiment, and a qualitative agreement is found.
27115647
Tetraquarks, hadronic molecules, meson-meson scattering and disconnected contributions in lattice QCD
There are generally two types of Wick contractions in lattice QCD calculations of a correlation function: connected and disconnected ones. The disconnected contribution is difficult to calculate and noisy, thus it is often neglected. In the context of studying tetraquarks, hadronic molecules, and mesonmeson scattering, we show that whenever there are both connected and singly disconnected contractions, the singly disconnected part gives the leading order contribution, and thus should never be neglected. As an explicit example, we show that information about the scalar mesons sigma, f(0)(980), a(0)(980), and kappa will be lost when neglecting the disconnected contributions.
53386989
Interactions of Charmed Mesons with Light Pseudoscalar Mesons from Lattice QCD and Implications on the Nature of the $D_{s0}^*(2317)$
We study the scattering of charmed mesons (D, D{sub s}) with light pseudoscalar mesons ({pi}, K) in full lattice QCD. The S-wave scattering lengths are calculated using L{umlt u}schers finite volume technique. We use the relativistic Fermilab formulation for the charm quark. For the light quark, we use domain-wall fermions in the valence sector and improved Kogut-Susskind sea quarks. We calculate the scattering lengths of isospin-3/2 D{pi}, D{sub s}{pi}, D{sub s}K, isospin-0 D{anti K} and isospin-1 D{anti K} channels on the lattice. For the chiral extrapolation, we use the chiral unitary approach to next-to-leading order, which at the same time allows us to give predictions for other channels. Furthermore, the hadronic molecular interpretation of the D{sub s0}*(2317) is consistent with our results. The isospin breaking decay width {Gamma}(D{sub s0}*(2317){yields}D{sub s}{pi}) in the hadronic molecular picture is updated to be (89{+-}22)keV.
18543466
Neutral top pion and lepton flavor violating processes
In the context of topcolor-assisted techicolor(TC2) models, we study the contributions of the neutral top-pion $\pi^{0}_{t}$ to the lepton flavor violating(LFV) processes $l_{i}\to l_{j}\gamma$ and $l_{i}\to l_{j}l_{k}l_{l}$. We find that the present experimental bound on $\mu\to e\gamma$ gives severe constraints on the free parameters of $TC2$ models. Taking into account these constraints, we consider the processes $l_{i}\to l_{j}l_{k}l_{l}$ generated by top-pion exchange at the tree-level and the one loop level, and obtain $Br(\mu\to 3e)\simeq 2.87\times 10^{-14}$, $1.1\times 10^{-15}\leq Br(\tau\to 3e)\simeq Br(\tau\to 2e\mu)\leq 4.4 \times 10^{-15} $, $3.1\times 10^{-15} \leq Br(\tau\to 2\mu e)\simeq Br(\tau\to 3\mu)\leq 1.5 \times 10^{-14}$ in most of the parameter space.
122741264
Quantum cosmology at finite temperature in superstring theory
We study cosmology induced by an ideal superstring gas at finite temperature. The thermal/quantum effects of the string gas generate a nontrivial effective potential at one-loop level. At certain points in the moduli space where generically massive states become massless, the effective potential develops local minima. The latter serve as moduli attractors, which induce time-dependent scalar masses decreasing in cosmological time. As a result, the coherent scalar oscillations dilute before nucleosynthesis, and the cosmological moduli problem is avoided. In particular, we study moduli stabilization in the cases of cosmology induced by i) a maximally supersymmetric heterotic string gas; ii) a gas of type II string compactified on Calabi-Yau three-folds. In case i), the local minima of the potential arise at enhanced gauge symmetry points, which can stabilize all moduli but the dilaton. In case ii), local minima of the effective potential are reached at the loci where 2-spheres or 3-spheres in the Calabi-Yau space shrink to zero size, giving rise to either conifold transitions or non Abelian gauge symmetries. Extra massless states are induced by D-brane wrapping the shrinking spheres, and the stabilized moduli are those controlling the volume of those spheres. In addition, in the two cases we also study respectively the type I dual theory which is maximally supersymmetric and the heterotic dual theory compactified on K3xT2. We show that dual moduli can be stabilized by novel non-perturbative effects implied by duality maps.
6471774
GRAVITATIONAL THERMODYNAMICS OF SPACETIME FOAM IN ONE-LOOP APPROXIMATION
We show from one-loop quantum gravity and statistical thermodynamics that the thermodynamics of quantum foam in flat spacetime and Schwarzschild spacetime is exactly the same as that of Hawking–Unruh radiation in thermal equilibrium. This means we show unambiguously that Hawking–Unruh thermal radiation should contain thermal gravitons or the contribution of quantum spacetime foam. As a by-product, we give also the quantum gravity correction in one-loop approximation to the classical black hole thermodynamics.
121633455
The quantized Schwarzschild Black Hole and the possible origin of Dark Matter
119013315
PHENOMENOLOGY OF GOLDSTINO COUPLINGS
A general coupling of the Goldstino to the matter field and the weak gravitational field is constructed based on the standard and nonlinear Volkov–Akulov realization of SUSY. The resulting Lagrangian, which is invariant under SUSY transformations, can give rise to explicit interactions which couple the helicity ±1/2 states of the gravitino with the gravitational field as well as the matter field.