Bulletin of the American Physical Society
2007 Joint Fall Meeting of the Texas Sections of the APS and AAPT; Zone 13 of SPS
Volume 52, Number 16
Thursday–Saturday, October 18–20, 2007; College Station, Texas
Session J4: HEN4: High Energy/Nuclear |
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Chair: Dave Toback, Texas A&M University Room: Rudder Tower 701 |
Saturday, October 20, 2007 10:40AM - 10:52AM |
J4.00001: Cosmic gamma-ray background anisotropies due to supersymmetric dark matter annihilation Sheldon Campbell One favored candidate for the dark matter in the universe is the lightest supersymmetric particle (LSP) in R-parity conserving supersymmetric extensions of the standard model of particle physics. Although stable against decay, the LSPs annihilate with one another and produce gamma-rays. Because of the large scale distribution of dark matter, anistropies in the gamma-ray background would trace the universe's large scale structure. This talk will summarize the halo model of large scale structure, present the predicted anisotropies due to dark matter annihilation in some supersymmetry models, and discuss the prospects for these anisotropies to be detected by future telescopes such as GLAST. [Preview Abstract] |
Saturday, October 20, 2007 10:52AM - 11:04AM |
J4.00002: Impacts of Supercritical String Cosmology at LHC Abram Krislock, Bhaskar Dutta, Teruki Kamon, Dimitri Nanopoulos, Alfredo Gurrola Supersymmetry (SUSY) is a leading particle physics theory to provide a solution to the amount (23\%) of the mysterious dark matter of the Universe. However, recently proposed Supercritical String Cosmology (SSC) alters the determination of the amount of the dark matter in SUSY models. As such, the allowed SUSY parameter space is staggeringly different. Thus, the SSC signals at the LHC are different from conventional SUSY signals. We characterize the SSC signals and study the discovery prospects at the LHC. [Preview Abstract] |
Saturday, October 20, 2007 11:04AM - 11:16AM |
J4.00003: Dark Matter Content in Q-Cosmology and Its Detectability in Anisotropy of Cosmic Gamma-Ray Spectra Phuongmai Truong, Bhaskar Dutta, Sheldon Campbell, Abram Krislock Dissipative Liouville cosmology (Q-Cosmology) introduces the effect of the dilaton field and central charge deficit on relic density of cold dark matter (CDM). The result is a reduction factor of 10 of the relic density, as compared to the value obtained in ordinary cosmology (Lahanas et al, 2007). Since dark matter particles are weakly interacting, annihilation can only occur in regions with high density, such as dark matter halos. Previous works on the anisotropy of the cosmic gamma-ray background (CGB) have shown that dark matter annihilation can be separated from the known background in the anisotropy data (Endo, Komatsu, 2007). In this talk, we first explain the dark matter content of the universe in Q-Cosmology and then study the detectability of this new model in the anisotropy of the cosmic gammy-ray spectra. [Preview Abstract] |
Saturday, October 20, 2007 11:16AM - 11:28AM |
J4.00004: Constraining properties of rotating neutron stars with nuclear data from terrestrial laboratories Plamen Krastev, Bao-An Li, Aaron Worley Abstract: Nuclear reactions with radioactive beams provide unique means to constrain the equation of state (EOS) of neutron-rich matter, in particular its density dependence through the nuclear symmetry energy. The EOS is important for our understanding of numerous phenomena in both nuclear physics and astrophysics. In this talk we will present our most recent results on the properties of rotating neutron stars with a particular emphasis on rapid rotations. The available constraints on the nuclear symmetry energy around saturation density restrict the possible rotating neutron-star configurations. [Preview Abstract] |
Saturday, October 20, 2007 11:28AM - 11:40AM |
J4.00005: Equation of state of isospin-asymmetric nuclear matter in relativistic quantum hadrodynamics with chiral limits Wei-Zhou Jiang, Bao-An Li, Lie-Wen Chen The Equation of State (EOS) of isospin asymmetric nuclear matter plays a crucial role in many important issues in astrophysics, the structure of exotic nuclei and the reaction dynamics of heavy-ion collisions. Using in-medium hadronic properties according to the Brown-Rho scaling due to the chiral symmetry restoration at high densities and considering naturalness of the coupling constants, we have constructed several relativistic mean-field (RMF) Lagrangians with chiral limits. The scalings and associated parameters that describe the in-medium hadronic properties are consistent with those from microscopic calculations or those extracted from recent experimental data. The resulting equations of state are used to produce a heavier maximum neutron star mass around twice solar mass consistent with recent observations. A satisfactory description for ground-state properties of finite nuclei is also achieved with these RMF models. Meanwhile, the asymmetric matter densities produced by these models are applied to calculate the in-medium NN cross sections at high energies in the relativistic impulse approximation. Furthermore, due to the importance of the Fock terms, an extension to the relativistic Hartree-Fock framework is expected for the current RMF models. [Preview Abstract] |
Saturday, October 20, 2007 11:40AM - 11:52AM |
J4.00006: Towards a Nuclear Parameter Calculation for Astrophysical Applications A. Samana, C. Barbero, S. Duarte, A. Dimarco, F. Krmpoti We evaluate the electronic neutrino-nucleus cross section within the context of a nuclear gross theory. We adopt an improved version of the gross theory of $\beta$-decay with a new trend for the theoretical parameter representing the energy spread of Gamow-Teller resonance by the spin-dependence part of the nuclear force within this model is obtained. A first application of this calculation is made in the region of nuclei involved in pre-supernova collapse where a comparison with available experimental results can be done ($A<70$). The obtained results agree with previous evaluations within other microscopic models. Present formalism can be extended to the region $A>70$ and offers an useful tool to perform nuclear calculations of neutrino capture cross section and $\beta$-decay rates for $r$-process nucleosynthesis within supernova neutrino wind environment. [Preview Abstract] |
Saturday, October 20, 2007 11:52AM - 12:04PM |
J4.00007: Comprehensive investigation of statistics of gauge groups of weakly coupled free fermionic heterotic strings Matthew Robinson, Gerald Cleaver We systematically and comprehensively study the statistics of the spectrum of gauge groups of the weakly coupled free fermionic heterotic region of the string landscape. Specifically, we are seeking to generate all possible gauge group sectors for consistent models containing free fermions of any order boundary conditions (beginning with order-2) and study the statistics of the gauge groups contained therein. For example, the initial order-2 investigation will yield the entire gamut of possible stringy ways of breaking SO(44) to SO(2n) $\otimes $ {\ldots} $\otimes $ SO(2m) tensor groups. Gauge group sectors with higher order fermions will produce generic breakings of SO(44) to tensor products containing SO(2n), SU(m), and E$_{6,7,8}$ factors. [Preview Abstract] |
Saturday, October 20, 2007 12:04PM - 12:16PM |
J4.00008: Heterotic models with vanishing one-loop cosmological constant and possibly perturbatively broken supersymmetry Gerald Cleaver, A. Faraggi, Elisa Manno, Cristina Timirgaziu It has been assumed that in a given string model there should exist all-order supersymmetric solutions to the F and D flatness constraints. This arises from analysis of point quantum field theories, for which if supersymmetry is preserved at the classical level (tree-level in perturbation theory), an index theorem forbids supersymmetry breaking at the perturbative quantum level. Therefore, in point quantum field theories supersymmetry breaking may only be induced by non-perturbative effects. We present a weak coupled free fermionic heterotic model that utilizes boundary conditions that are both symmetric and asymmetric in the basis vectors that break SO(10) to SO(6)$\otimes $SO(4), with respect to two of the twisted sectors of the Z$_{2}\otimes $Z$_{2}$ orbifold. The consequence is that two of the untwisted Higgs multiplets, associated with two of the twisted sectors, are projected from the massless spectrum. As a result, the string model contains a single pair of untwisted Higgs doublets. In the process of seeking such a model with a phenomenologically viable supersymmetric flat direction we arrive at the unexpected conclusion that the model may not contain perturbative all-order supersymmetric flat directions. In the least, this model appears to have no D-flat directions that can be proven to be F-flat to all order, other than through order-by-order analysis. [Preview Abstract] |
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