17627816
Exclusive vs. diffractive vector meson production in DIS at small x or off nuclei
The diffractive production of vector mesons in deep inelastic scattering (DIS) is calculated in the McLerran-Venugopalan model. This is relevant when large parton densities are probed by the virtual photon, as is the case at small Bjorken x or in DIS off nuclei. We investigate differences between the exclusive production (when the target doesn't break up) which dominates at small momentum transfer squared |t|, and the diffractive production (when the target scatters inelastically) which dominates at large |t|.
53531246
Lattice worldline representation of correlators in a background field
A bstractWe use a discrete worldline representation in order to study the continuum limit of the one-loop expectation value of dimension two and four local operators in a background field. We illustrate this technique in the case of a scalar field coupled to a non-Abelian background gauge field. The first two coefficients of the expansion in powers of the lattice spacing can be expressed as sums over random walks on a d-dimensional cubic lattice. Using combinatorial identities for the distribution of the areas of closed random walks on a lattice, these coefficients can be turned into simple integrals. Our results are valid for an anisotropic lattice, with arbitrary lattice spacings in each direction.
119193077
On p⊥-broadening of high energy partons associated with the LPM effect in a finite-volume QCD medium
We study the contributions from radiation to p⊥-broadening of a high energy parton traversing a QCD medium with a finite length L. The interaction between the parton and the medium is described by decorrelated static multiple scattering. Amplitudes of medium-induced gluon emission and parton self-energy diagrams are evaluated in the soft gluon limit in the BDMPS formalism. We find both the double-logarithmic correction from incoherent scattering, which is parametrically the same as that in single scattering, and the logarithmic correction from the LPM effect. Therefore, we expect a parametrically large correction from radiation to the medium-induced p⊥-broadening in perturbative QCD.
118667819
On using cold baryogenesis to constrain the two-Higgs doublet model
A bstractWe consider the creation of the cosmological baryon asymmetry in the Two Higgs Doublet Model. We imagine a situation where the masses of the five Higgs particles and the two Higgs vevs are constrained by collider experiments, and demonstrate how the requirement of successful baryogenesis can be used to further constrain the remaining 4-dimensional parameter space of the model. We numerically compute the asymmetry within the scenario of Cold Electroweak Baryogenesis, which is particularly straightforward to simulate reliably.
119251781
Looking inside neutron stars: Microscopic calculations confront observations
While QCD appears not to be accurately solvable in the regime of interest for neutron star physics, microscopic calculations are feasible at both low and very high densities. In this work, we propose using the most realistic calculations in these two regimes of nuclear physics and perturbative QCD, and construct equations of state by matching the results requiring thermodynamic consistency. We find that the resulting equations of state --- in contrast to several hadronic ones --- are able to reproduce current observational data on neutron stars without any fine tuning, and allow stable hybrid stars with masses up to 2.1M_{sun}. Using recent observations of star radii, we perform a maximum likelihood analysis to further constrain the equation of state, and in addition show that the effects of rotation on radii and masses should not be neglected in future precision studies.
119212232
Quark production, Bose-Einstein condensates and thermalization of the quark-gluon plasma
Abstract In this paper, we study the thermalization of gluons and N f flavors of massless quarks and antiquarks in a spatially homogeneous system. First, two coupled transport equations for gluons and quarks (and antiquarks) are derived within the diffusion approximation of the Boltzmann equation, with only 2 ↔ 2 processes included in the collision term. Then, these transport equations are solved numerically in order to study the thermalization of the quark–gluon plasma. At initial time, we assume that only gluons are present and we choose the gluon distribution of a form inspired by the color glass picture, namely f = f 0 θ ( 1 − p Q s ) with Q s the saturation momentum and f 0 a constant. The subsequent evolution of the system may, or may not, lead to the formation of a (transient) Bose condensate (BEC) of gluons, depending on the value of f 0 . In fact, we observe, depending on the value of f 0 , three different patterns: (a) thermalization without BEC for f 0 ≤ f 0 t , (b) thermalization with transient BEC for f 0 t f 0 ≤ f 0 c , and (c) thermalization with BEC for f 0 c f 0 . The values of f 0 t and f 0 c depend on N f . When f 0 ≳ 1 > f 0 c , the onset of BEC occurs at a finite time t c ∼ 1 ( α s f 0 ) 2 1 Q s . We also find that quark production slows down the thermalization process: the equilibration time for N f = 3 is typically about 5 to 6 times longer than that for N f = 0 at the same Q s and f 0 .
196095135
Simulation of Central and Dimuon Events in the ALICE DAQ System.
59844874
Simulation of the ALICE DAQ System with GALSIM
28663874
Modelling of the ALICE data acquisition system
The Heavy Ion Experiment ALICE is one of the three experiments at the LHC accelerator at CERN. Modeling and simulation of the large scale ALICE Data Acquisition (DAQ) system is necessary in order to study the behavior of the system. The development of a simulator -- ALSIM for the ALICE Data Acquisition System -- is described. ALSIM models front-end data readout, event building, data reduction and data storage. Technology dependent implementations can be linked in various topologies can be defined dynamically by means of description files. The simulation environment will be described as well as details of the model.