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.
196069470
Reference Manual and User's Manual for ALICE DAQ Modelling and Simulation
59844874
Simulation of the ALICE DAQ System with GALSIM
196095135
Simulation of Central and Dimuon Events in the ALICE DAQ System.
119303364
Cold electroweak baryogenesis in the two Higgs-doublet model
A bstractWe perform the first investigation of cold electroweak baryogenesis in the two Higgs-doublet model (2HDM). The electroweak symmetry breaking transition is assumed to occur through a spinodal instability from a super-cooled initial state. We consider the creation of net Chern-Simons number, which through the axial anomaly is equivalent to a baryon asymmetry. CP violation is explicit in the scalar potential, but only in combination with P-violation is it possible for an asymmetry to be generated. This is introduced through the leading C-and P-breaking, but CP invariant, term expected to arise upon integrating out the fermions in the theory. We perform real-time lattice simulations of the transition, and find the coefficient of this term required for successful baryogenesis.
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 .
119193432
On holographic thermalization and gravitational collapse of massless scalar fields
A bstractIn this paper we study thermalization in a strongly coupled system via AdS/CFT. Initially, the energy is injected into the system by turning on a spatially homogenous scalar source coupled to a marginal composite operator. The thermalization process is studied by numerically solving Einstein’s equations coupled to a massless scalar field in the Poincare patch of AdS5. We define a thermalization time tT on the AdS side, which has an interpretation in terms of a spacelike Wilson loop $ \left\langle {W\left( {l\tilde{-}\frac{1}{T}} \right)} \right\rangle $ in CFT. Here T is the thermal equilibrium temperature. We study both cases with the source turned on in short $ \left( {\varDelta t\lesssim \frac{1}{T}} \right) $ and long $ \left( {\varDelta t\gtrsim \frac{1}{T}} \right) $ durations. In the former case, the thermalization time $ {t_T}=\frac{gt }{T}\lesssim \frac{1}{T} $ and the coefficient $ {g_t}\tilde{-}0.73 $ in the limit $ \varDelta t\lesssim \frac{0.02 }{T} $. In the latter case, we find double- and multiple-collapse solutions, which may be interpreted as the gravity duals of two- or multi-stage thermalization in CFT. In all the cases our results indicate that such a strongly coupled system thermalizes in a typical time scale $ {t_T}\tilde{-}\frac{O(1) }{T} $.
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.
118447664
Nonrenormalizability of the classical statistical approximation
In this paper, we discuss questions related to the renormalizability of the classical statistical approximation, an approximation scheme that has been used recently in several studies of out-of-equilibrium problems in Quantum Field Theory. Although the ultraviolet power counting in this approximation scheme is identical to that of the unapproximated quantum field theory, this approximation is not renormalizable. The leading cause of this non-renormalizability is the breakdown of Weinberg's theorem in this approximation. We also discuss some practical implications of this negative result for simulations that employ this approximation scheme, and we speculate about a possible modification of the classical statistical approximation in order to systematically subtract the leading residual divergences.