122156675
Relativistic Hadron Model with Intrinsic Mass Splittings
A simple mechanism for the $\mathrm{SU}(3)$-symmetry breaking in strong interactions is introduced by using the formalism of the multispinor field equations, which avoids the use of physical quarks but has resemblance to the quark model. The resulting treatment leads to the Gell-Mann-Okubo mass formula for baryons, but not for mesons. It yields approximate values of -19.5\ifmmode^\circ\else\textdegree\fi{} and 33\ifmmode^\circ\else\textdegree\fi{} for the $\ensuremath{\eta}\ensuremath{-}{\ensuremath{\eta}}^{\ensuremath{'}}$ and $\ensuremath{\varphi}\ensuremath{-}\ensuremath{\omega}$ mixing angles, respectively, and also provides a reasonable explanation for the intermultiplet meson mass formula $m_{K}^{}{}_{}{}^{2}\ensuremath{-}m_{\ensuremath{\pi}}^{}{}_{}{}^{2}=m_{{K}^{*}}^{}{}_{}{}^{2}\ensuremath{-}m_{\ensuremath{\rho}}^{}{}_{}{}^{2}$.
17051703
Quantum-chromodynamic potential model for light-heavy quarkonia and the heavy quark effective theory.
We have investigated the spectra of light-heavy quarkonia with the use of a quantum-chromodynamic potential model, which is similar to that used earlier for heavy quarkonia. An essential feature of our treatment is the inclusion of the one-loop radiative corrections to the quark-antiquark potential, which contribute significantly to the spin splitting among the quarkonium energy levels. Unlike [ital c[bar c]] and [ital b[bar b]], the potential for a light-heavy system has a complicated dependence on the light and heavy quark masses [ital m] and [ital M], and it contains a spin-orbit mixing term. We have obtained excellent results for the observed energy levels of [ital D][sup 0], [ital D][sub [ital s]], [ital B][sup 0], and [ital B][sub [ital s]], and we are able to provide predicted results for many unobserved energy levels. Our potential parameters for different quarkonia satisfy the constraints of quantum chromodynamics. We have also used our investigation to test the accuracy of the heavy quark effective theory. We find that the heavy quark expansion yields generally good results for the [ital B][sup 0] and [ital B][sub [ital s]] energy levels provided that [ital M][sup [minus]1] and [ital M][sup [minus]1] ln [ital M] corrections are taken into account more » in the quark-antiquark interactions. It does not, however, provide equally good results for the energy levels of [ital D][sup 0] and [ital D][sub [ital s]], which indicates that the effective theory cannot be applied accurately to the [ital c] quark. « less
6552264
Nonsingular potential model for heavy quarkonia.
A nonsingular potential model for heavy quarkonia is described which does not require recourse to an illegitimate perturbative treatment for the investigation of quarkonium spectra. Our overall results for the energy levels, the leptonic widths, and the E1 transition widths are in very good agreement with the experimental data for bb-bar and they are reasonably good for cc-bar. We also find that the confining part of the quarkonium potential is scalar-vector exchange rather than the currently favored scalar exchange.
121297767
High-energy graviton bremsstrahlung
122167852
MULTIPLE PHOTON PRODUCTION IN QUANTUM ELECTRODYNAMICS
Multiple production of photons in high-energy processes in quantum electrodynamics is investigated, and the electron-positron annihilation is specially discussed in detail. It is found that at very high energies in cosmic rays, multiple production of up to four or five observable photons can easily take place. But, the probability, according to quantum electrodynamics, for the multiple production of a larger number of observable photons is quite small.
121663425
Quantum-chromodynamic potential model for light and heavy quarkonia
Our earlier treatment for the investigation of the cc-bar, bb-bar, and tt-bar spectra is extended to other p quarkonia with u, d, s, c, and b quarks. We find that it is possible to account fully for the observed ground-state hyperfine splittings of light as well as heavy quarkonia provided that the perturbative quantum-chromodynamic potential is supplemented not only by the nonperturbative confining potential but also by a nonperturbative annihilation potential which rapidly decreases with increase in the quark mass. We also give our predictions for the experimentally interesting bu-bar, bs-bar, and bc-bar systems with unknown mass splittings.
123705690
Stringy restrictions on the Scherk-Schwarz mechanism
The authors consider the sigma model describing the propagation of a bosonic string in a manifold of the type M4(X)K obtained by compactification of D=26 spacetime using the Scherk-Schwarz mechanism. The requirement of 2D conformal invariance (at the 1-loop level) of this sigma model is shown to impose rather stringent restrictions on the mass parameters used in the Scherk-Schwarz mechanism. Implications for the background field mass spectrum in the model considered by Scherk and Schwarz (1979) are examined.
14927510
A Transport Model for Nuclear Reactions Induced by Radioactive Beams
Major ingredients of an isospin and momentum dependent transport model for nuclear reactions induced by radioactive beams are outlined. Within the IBUU04 version of this model we study several experimental probes of the equation of state of neutron‐rich matter, especially the density dependence of the nuclear symmetry energy. Comparing with the recent experimental data from NSCL/MSU on isospin diffusion, we found a nuclear symmetry energy of Esym(ρ) ≈ 31.6(ρ/ρ0)1.05 at subnormal densities. Predictions on several observables sensitive to the density dependence of the symmetry energy at supranormal densities accessible at GSI and the planned Rare Isotope Accelerator (RIA) are also made.
16059029
Coalescence, percolation and nuclear multifragmentation
Abstract We show that the coalescence model for fragment formation leads to an approximate site percolation model. Features characteristic of a percolation model also appear in microscopic models of disassembly.
116940731
Dissipation, hydrodynamics and the fireball
We investigate the hydrodynamics of the QCD plasma using dimensionless numbers built from the thermodynamics and transport theory of the plasma and characteristic dimensions of the fireball produced in heavy-ion collisions. We find that by the usual measures, dissipation is strong, and the fireball is on the borderline of equilibrium. As a result, the system is richer in phenomena than ideal hydrodynamics would predict. One general implication is that it may be possible to get a direct view of the QCD plasma phase rather than having to infer its existence indirectly from signals that come from the freezeout isotherm after the fireball has cooled into the hadronic phase.
118503704
Two-Zero mass matrices and sterile neutrinos
A bstractRecent experimental data is indicative of the existence of sterile neutrinos. The minimal scheme that can account for the data and is consistent with cosmological observations is the 3+1 picture which consists of three predominantly active and one predominantly sterile neutrino with the fourth neutrino being heavier than the other three. Within this scheme there are two possibilities depending on whether the three light states obey normal or inverted hierarchy. In this paper we consider the two-zero textures of the low energy neutrino mass matrix in presence of one additional sterile neutrino. We find that among 45 possible two-zero textures for this case, 15 are consistent with all current observations. Remarkably, these correspond to the two-zero textures of a three active neutrino mass matrix. We discuss the mass spectrum and the parameter correlations that we find in the various textures. We also present the effective mass governing neutrinoless double beta decay as a function of the lowest mass.