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.
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.
120902364
A NUMERICAL STUDY OF IMPROVED WILSON QUARK ACTIONS ON ANISOTROPIC LATTICES
Tadpole improved Wilson quark actions with clover terms on anisotropic lattices are studied numerically. Using asymmetric lattice volumes, the pseudo-scalar meson dispersion relations are measured for 8 lowest lattice momentum modes with quark mass values ranging from the strange to the charm quark with various values of the gauge coupling β and 3 different values of the bare speed of light parameter ν. These results can be utilized to extrapolate or interpolate to obtain the optimal value for the bare speed of light parameter νopt(m) at a given gauge coupling for all bare quark mass values m. In particular, the optimal values of ν at the physical strange and charm quark mass are given for various gauge couplings. The lattice action with these optimized parameters can then be used to study physical properties of hadrons involving either light or heavy quarks.
209955454
Charmed hadron interactions
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.
118644408
Topological limit of gravity admitting an SU(2) connection formulation
We study the Hamiltonian formulation of the generally covariant theory defined by the Lagrangian 4-form L=e{sub I} and e{sub J} and F{sup IJ}({omega}), where e{sup I} is a tetrad field and F{sup IJ} is the curvature of a Lorentz connection {omega}{sup IJ}. This theory can be thought of as the limit of the Holst action for gravity for the Newton constant G{yields}{infinity} and Immirzi parameter {gamma}{yields}0, while keeping the product G{gamma} fixed. This theory has for a long time been conjectured to be topological. We prove this statement both in the covariant phase space formulation as well as in the standard Dirac formulation. In the time gauge, the unconstrained phase space of theory admits an SU(2) connection formulation which makes it isomorphic to the unconstrained phase space of gravity in terms of Ashtekar-Barbero variables. Among possible physical applications, we argue that the quantization of this topological theory might shed new light on the nature of the degrees of freedom that are responsible for black entropy in loop quantum gravity.
13085576
Alignment of the ALICE inner tracking system with cosmic-ray tracks
ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 mu m in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10(5) charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.
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.
117495741
Quantum de Sitter Space-Time and the Dark Energy
Three years ago, we introduced a new way to quantize the static Schwarzschild black hole(SSBH), there the SSBH was first treated as a single periodic Euclidean system and then the Bohr-Sommerfeld quantum condition of action was used to obtain a quantum theory of Schwarzschild black hole.[1] Now in this short report, we try to extend the above method to quantize the static de Sitter(SDS) space-time and establish a quantum theory of both SDS space and dark energy.