Bulletin of the American Physical Society
Fall 2009 Meeting of the Four Corners Section of the APS
Volume 54, Number 14
Friday–Saturday, October 23–24, 2009; Golden, Colorado
Session K5: Theoretical Particle Physics |
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Chair: Bruce Barrett, University of Arizona Room: Green Center 265 |
Saturday, October 24, 2009 1:50PM - 2:02PM |
K5.00001: Universal Long-time Relaxation Behavior of a Nuclear Spin Lattice Eric Sorte, Brian Saam We report experimental results indicating that isolated macroscopic systems of interacting nuclear spins possess the fundamental property that spin decays, starting from different initial configurations, quickly evolve towards the same long time behavior. We show that the generic functional form of the long time behavior of the infinite temperature spin correlation function decays with either a simple exponential or exponential multiplied by a cosine, even though the characteristic timescale of the functional form of this decay is considered non-Markovian. The results corroborate predictions made by a theory based on a strong conjecture that, as a result of chaos generated by the correlated spin dynamics, a Brownian-like Markovian description can be applied to the long time properties of ensemble average quantities on a non-Markovian timescale. [Preview Abstract] |
Saturday, October 24, 2009 2:02PM - 2:14PM |
K5.00002: Lattice Computation of Nucleon Strangeness Walter Freeman, Douglas Toussaint The matrix element $\langle N|s \overline{s}|N \rangle$, the ``nucleon strangeness,'' is of interest to the general understanding of hadronic physics, as it gives the amount by which the presence of a nucleon disturbs the vacuum strange quark condensate. Moreover, knowledge of this quantity is also mportant to the interpretation of proposed dark matter detection experiments, since many dark matter scenarios have a large contribution to the scattering cross-section from Higgs exchange with heavy quarks in nuclear matter. Due to the extreme difficulty of measuring it experimentally, it must be calculated from first principles using lattice QCD, but previous calculations have produced inconsistent or imprecise results. Using the Feynman-Hellman theorem, we relate the matrix element in question to the derivative ${\partial M_N}\over{\partial m_s}$. We then evaluate this derivative by analyzing the existing library of MILC gauge configurations and hadron propagators, and thus determine $\langle N|s \overline{s}|N \rangle$ to greater precision than previously possible. We have evaluated this quantity at a variety of light quark masses and lattice spacings and extrapolate to the physical point; at the physical point, ${\partial M_N}\over{\partial m_s}$ = $0.69(7)_{stat}(9)_{sys}$ in the $\overline{MS} (2 GeV)$ regularization. We are currently working on a technique to further reduce these errors by partitioning the lattice and only considering the quark condensate in the relevant fraction, but this requires recalculation of hadron propagators which is ongoing. [Preview Abstract] |
Saturday, October 24, 2009 2:14PM - 2:26PM |
K5.00003: Angular Momentum Decomposition in QED and QCD Hikmat B.C., Matthias Burkardt We calculate the orbital angular momentum of the ``quark'' in the scalar diquark model as well as that of the electron in QED( to order $\alpha)$. We compare the orbital angular momentum obtained from the Jaffe - Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum. [Preview Abstract] |
Saturday, October 24, 2009 2:26PM - 2:38PM |
K5.00004: Mirror Symmetry: FJRW-rings and Landau-Ginzburg Orbifolds Pedro Acosta For any non-degenerate, quasihomogeneous superpotential $W$ and an admissible group of diagonal symmetries G, Fan, Jarvis and Ruan have constructed a quantum cohomological field theory (FJRW-theory) that gives, among other things, a Frobenius algebra $\mathcal{H}_{W,G}$ ((a,c) ring) and correlators associated with the superpotential. This construction is analogous to a theory of the Gromov-Witten type. The FJRW- theory is a candidate for the mathematical structure behind $\mathcal{N}=$ $2$ superconformal Landau-Ginzburg orbifolds. In this presentation I will give an overview of this theory and discuss the Berglund-H\"{u}bsch-Krawitz mirror symmetry conjecture: For a given invertible superpotential $W$ there exists an invertible superpotential $W^{T}$ such that the Frobenius algebra $\mathcal{H}_{W,G}$ is isomorphic to the (c,c) ring of $W^{T}$, and the Frobenius algebra $\mathcal{H}_ {W^{T},G^{T}}$ is isomorphic to the (c,c) ring of $W$. [Preview Abstract] |
Saturday, October 24, 2009 2:38PM - 2:50PM |
K5.00005: Some Pins for Cosmic Ladder - New Correlations on Hubble Diagram Karan Molaverdikhani After Hubble's law detection, scientists tried to measuring and improving the Hubble Constant for finding a better estimation of Universe Age. Development of some new methods and applying new observational technologies help them to find a better view of Universe. They found a Ladder for reaching the End of World. The steps of this Cosmic Distance Ladder are Radar measurement, Parallax, Main Sequence Fitting, Cepheids, Tully Fisher relation, Type Ia supernovae and finally Hubble's law. But we can't use the Near Tools instead Far Tools, because they haven't enough accuracy on that range. Also, using the Near Tools (like luminosity flux or size and type of galaxies) are easier than using the standard candles on cosmic ladder. On the other hand, with applying the Tools at the different ranges, we can allocate a new point of view for using them as new Tools. We find some relations between relative distance-redshift (Near Tools) and velocity-redshift (today cosmic distance ladder result) and expand these relations to using in High Redshift zone. With choosing about one million galaxies (at any type and any redshift) in SDSS and surveying their behavior on these diagrams, we got a bunch of correlations on Hubble Diagram especially on z$>$1 and offer some pins for extension the Ladder. [Preview Abstract] |
Saturday, October 24, 2009 2:50PM - 3:02PM |
K5.00006: Influence of spin on the fragment Anisotropies A.N. Behkami, M. Ghodsi Several selected fission fragment angular distributions when at least one of the spins of the projectile or target is appreciable have been investigated. The known experimental data for example$^{11}$B+$^{209}$Bi was analyzed by means of the Couple Channel spin formulism. This formulism suggests that the projectile spin has sizable effect on the angular anisotropies within the limits of energy near the fusion barrier. The analysis of the fission fragment angular distributions has also made using the statistical secession model (SSM). Variance K$^{2}_{o}$ of the K distribution are compared with their corresponding S$^{2}_{o}$ values. It turns out that the variances from these two models differ by about 20{\%} for most cases studied. However, in the case of $^{12}$C+ $^{237}$Np the value of K$^{2}_{o}$ is comparable with its corresponding S$^{2}_{o}$ value. This suggests that the effect of the projectile spin on angular anisotropies is more noticeable. The effect of the choice of the level density parameter of the compound nucleus on angular anisotropies has also been investigated. It is found that angular anisotropies are very sensitive to level density parameter. It turns out that the experimental anisotropies are well produced with the model calculation using higher values of the level density predicted by Fermi gas model. This effect will be presented and discussed. [Preview Abstract] |
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