118643861
Glasma evolution and Bose-Einstein condensation with elastic and inelastic collisions
In this paper we investigate the role of inelastic collisions in the kinetic evolution of a highly overpopulated gluon system starting from Glasma-type initial condition. Using the Gunion-Bertsch formula we derive the inelastic collision kernel under the collinear and small angle approximations. With both numerics and analytic analysis, we show that the inelastic process has two effects: globally changing (mostly reducing) the total particle number, while locally at small momentum regime always filling up the infrared modes extremely quickly. This latter effect is found to significantly speed up the emergence of a local thermal distribution in the infrared regime with vanishing local "chemical potential" and thus catalyze the onset of dynamical Bose-Einstein Condensation to occur faster (as compared with the purely elastic case) in the overpopulated Glasma.
118638548
Phase diagram of dilute nuclear matter: Unconventional pairing and the BCS-BEC crossover
We report on a comprehensive study of the phase structure of cold, dilute nuclear matter featuring a ${}^{3}\phantom{\rule{-0.16em}{0ex}}{S}_{1}$-${}^{3}\phantom{\rule{-0.16em}{0ex}}{D}_{1}$ condensate at nonzero isospin asymmetry, within wide ranges of temperatures and densities. We find a rich phase diagram comprising three superfluid phases, namely, a Larkin-Ovchinnikov-Fulde-Ferrell phase, the ordinary BCS phase, and a heterogeneous, phase-separated BCS phase, with associated crossovers from the latter two phases to a homogeneous or phase-separated Bose-Einstein condensate of deuterons. The phase diagram contains two tricritical points (one a Lifshitz point), which may degenerate into a single tetracritical point for some degree of isospin asymmetry.
119238061
Inhomogeneous condensates in dilute nuclear matter and BCS-BEC crossovers
We report on recent progress in understanding pairing phenomena in low-density nuclear matter at small and moderate isospin asymmetry. A rich phase diagram has been found comprising various superfluid phases that include a homogeneous and phase-separated BEC phase of deuterons at low density and a homogeneous BCS phase, an inhomogeneous LOFF phase, and a phase-separated BCS phase at higher densities. The transition from the BEC phases to the BCS phases is characterized in terms of the evolution, from strong to weak coupling, of the condensate wavefunction and the second moment of its density distribution in r-space. We briefly discuss approaches to higher-order clustering in low-density nuclear matter.
119581702
Neutrino emission from direct Urca processes in pion condensed quark matter
We study neutrino emission from direct Urca processes in pion condensed quark matter. In compact stars with high baryon density, the emission is dominated by the gapless modes of the pion condensation which leads to an enhanced emissivity. While for massless quarks the enhancement is not remarkable, the emissivity is significantly larger and the cooling of the condensed matter is considerably faster than that in normal quark matter when the mass difference between u and d quarks is sizable.
35650226
Chiral phase structure at finite temperature and density in Einstein universe
Abstract The gravitational effect on the chiral phase structure at finite temperature and density is investigated in the framework of Nambu–Jona-Lasinio model in D -dimensional ultrastatic Einstein universe. In mean field approximation, the thermodynamic potential and the gap equation determining the curvature, temperature and density dependence of the chiral condensate are analytically derived. In the sense of chiral symmetry restoration and the order of the phase transition, the scalar curvature of the space–time plays similar role as the temperature.
35328229
BCS-BEC crossover in 2D Fermi gases with Rashba spin-orbit coupling.
We present a systematic theoretical study of the BCS-BEC crossover in two-dimensional Fermi gases with Rashba spin-orbit coupling (SOC). By solving the exact two-body problem in the presence of an attractive short-range interaction we show that the SOC enhances the formation of the bound state: the binding energy E(B) and effective mass m(B) of the bound state grows along with the increase of the SOC. For the many-body problem, even at weak attraction, a dilute Fermi gas can evolve from a BCS superfluid state to a Bose condensation of molecules when the SOC becomes comparable to the Fermi momentum. The ground-state properties and the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature are studied, and analytical results are obtained in various limits. For large SOC, the BKT transition temperature recovers that for a Bose gas with an effective mass m(B). We find that the condensate and superfluid densities have distinct behaviors in the presence of SOC: the condensate density is generally enhanced by the SOC due to the increase of the molecule binding; the superfluid density is suppressed because of the nontrivial molecule effective mass m(B).
118565086
Stringy origin of Tevatron Wjj anomaly
Abstract The invariant mass distribution of dijets produced in association with W bosons, recently observed by the CDF Collaboration at Tevatron, reveals an excess in the dijet mass range 120 – 160 GeV / c 2 , 3σ beyond Standard Model expectations. We show that such an excess is a generic feature of low mass string theory, due to the production and decay of a leptophobic Z ′ , a singlet partner of SU ( 3 ) gluons coupled primarily to the U ( 1 ) baryon number. In this framework, U ( 1 ) and SU ( 3 ) appear as subgroups of U ( 3 ) associated with open strings ending on a stack of 3 D-branes. In addition, a minimal model contains two other stacks to accommodate the electro-weak SU ( 2 ) ⊂ U ( 2 ) and the hypercharge U ( 1 ) . Of the three U ( 1 ) gauge bosons, the two heavy Z ′ and Z ″ receive masses through the Green–Schwarz mechanism. For a given Z ′ mass, the model is quite constrained. Fine tuning three of its free parameters is just sufficient to simultaneously ensure: a small Z – Z ′ mixing in accord with the stringent LEP data on the Z mass; very small (less than 1%) branching ratio into leptons; and a large hierarchy between Z ″ and Z ′ masses. The heavier neutral gauge boson Z ″ is within the reach of LHC.
119298365
Anomaly Puzzle, Curved-Spacetime Spinor Hamiltonian, and String Phenomenology
In the first part of this dissertation, we study two different aspects of string phenomenology. First we discuss the complementary signals of low mass superstrings at the proposed electron-positron facilities (ILC and CLIC), in e+e- and {\gamma} {\gamma} collisions. We examine all relevant four-particle amplitudes evaluated at the center of mass energies near the mass of lightest Regge excitations and extract the corresponding pole terms. Secondly, we consider string realizations of the Randall-Sundrum effective theory and explore the search for the lowest massive Regge excitation of the gluon and of the extra (color singlet) gauge boson inherent of D-brane constructions. We also study the ratio of dijet mass spectra at small and large scattering angles. We show that with the first fb-1 such a ratio can probe lowest-lying Regge states for masses ~3.0 TeV. Finally, we propose that the 3.2$\sigma$ excess at about $140 {\rm GeV}$ in the dijet mass spectrum of $W$ + jets reproted by the CDF Collaboration originates in the decay of a leptophobic $Z'$ that can be related to the U(1) symmetries inherent of D-brane models. In the remaining parts of this dissertation, we discuss several points that may help to clarify some questions that remain about the anomaly puzzle in N=1 supersymmetric Yang-Mills theory and we investigate the issue that the Dirac Hamiltonian of a spin-1/2 particle in a curved background appears to be non-hermitian.
8584939
A new code for orbit response matrix analysis
Orbit response matrix(ORM) method has been widely used for lattice modeling, and beam diagnostics, however the difficulty on convergence arises as the model becomes larger, more complicated or with nonlinear parameters brought in. A new code named YAOC(Yet Another Orbit Code) was developed based on a robust numerical method called scaled Levenberg-Marquardt algorithm, and its applications on various lattices are discussed here.
18932536
Bunch length measurements in SPEAR3
A series of bunch length measurements were made in SPEAR3 for two different machine optics. In the achromatic optics the bunch length increases from the low-current value of 16.6 ps rms to about 30 ps at 25 ma/bunch yielding an inductive impedance of -0.17 Omega. Reducing the momentum compaction factor by a factor of ~60 [1] yields a low-current bunch length of ~4 ps rms. In this paper we review the experimental setup and results.
117158642
Space charge stopband correction
It is speculated that the space charge effect cause beam emittance growth through the resonant envelope oscillation. Based on this theory, we propose an approach, called space charge stopband correction, to reduce such emittance growth by compensation of the half-integer stopband width of the resonant oscillation. It is illustrated with the Fermilab Booster model.