119851484
Energy loss of high energy quarks and gluons in the quark-gluon plasma
Abstract A complete leading order expression for the collisional energy loss of a heavy quark in a quark-gluon plasma at high temperatures is presented. Including screening effects by using an effective perturbation theory proposed by Braaten and Pisarski, a gauge independent and infrared finite result is obtained. Estimates for the collisional and radiative energy loss of light quarks and gluons are given. Implications for jet quenching as a signal for a quark-gluon plasma formation in ultrarelativistic heavy ion collisions at RHIC and LHC are discussed.
15847080
Convergence Properties of the Equal-Time Connected Green Function Approach for Temporal Gauge SU(2)2+1Yang–Mills Theory
Abstract The hierarchy of equations of motion for equal-time Green functions in temporal gauge SU( N ) Yang–Mills theory is truncated using an expansion in terms of connected Green functions. A second hierarchy of constraint equations arises from Gauss law and can be truncated in a similar way. Within this approximation scheme we investigate SU(2) Yang–Mills theory on a torus in 2+1 spacetime dimensions in a finite basis of plane wave states and focus on infrared and ultraviolet properties of the approach. In all truncation schemes considered up to the 4-point level the connected Green function approach is found to be UV divergent and to violate gauge invariance. The problems associated with adiabatically generating a nonperturbative ground state are discussed as well.
15289089
Constraint Correlation Dynamics of SU(N) Gauge Theories
Abstract A constraint correlation dynamics up to 4-point Green functions is proposed for SU(N) gauge theories which reduces the N-body quantum field problem to the two-body level. The resulting set of nonlinear coupled equations fulfills all conservation laws including fermion number, linear and angular momenta, as well as the total energy. Apart from the conservation laws in the space-time degrees of freedom the Gauss law is conserved as a quantum expectation value identically for all times. The same holds for the Ward identities as generated by commutators of Gauss operators. The constraint dynamical equations are highly non-perturbative and thus applicable also in the strong coupling regime, as, e.g., low-energy QCD problems.
14707324
QUARK PROPAGATION IN A QUARK-GLUON PLASMA WITH GLUON CONDENSATE
Abstract We present a calculation of the thermal quark propagator taking the gluon condensate above the critical temperature into account. The quark dispersion relation following from this propagator, describing two massive modes, is discussed.
15503324
Ultrarelativistic electron-positron plasma
AbstractUltrarelativistic electron-positron plasmas can be produced in 
high-intensity laser fields and play a role in various astrophysical 
situations. Their properties can be calculated using QED at finite 
temperature. Here we will use perturbative QED at finite temperature 
for calculating various important properties, such as the equation of 
state, dispersion relations of collective plasma modes of photons and 
electrons, Debye screening, damping rates, mean free paths, collision 
times, transport coefficients, and particle production rates, of 
ultrarelativistic electron-positron plasmas. In particular, we will 
focus on electron-positron plasmas produced with ultra-strong lasers.
14704789
Hard Thermal Photon Production in Relativistic Heavy Ion Collisions
The recent status of hard thermal photon production in relativistic heavy ion collisions is reviewed and the current rates are presented with emphasis on corrected bremsstrahlung processes in the quark-gluon plasma (QGP) and quark-hadron duality. Employing Bjorken hydrodynamics with an EOS supporting the phase transition from QGP to hot hadron gas (HHG), thermal photon spectra are computed. For SPS 158 GeV Pb+Pb collisions, comparison with other theoretical results and the WA98 direct photon data indicates significant contributions due to prompt photons. Extrapolating the presented approach to RHIC and LHC experiments, predictions of the thermal photon spectrum show a QGP outshining the HHG in the high-pT -region.
4979096
Multiple Higgs and vector boson production beyond the Standard Model
A bstractIf the electroweak symmetry breaking is originated from a strongly coupled sector, as for instance in composite Higgs models, the Higgs boson couplings can deviate from their Standard Model values. In such cases, at sufficiently high energies there could occur an onset of multiple Higgs boson and longitudinally polarised electroweak gauge boson (VL) production. We study the sensitivity to anomalous Higgs couplings in inelastic processes with 3 and 4 particles (either Higgs bosons or VL’s) in the final state. We show that, due to the more severe cancellations in the corresponding amplitudes as compared to the usual 2 → 2 processes, large enhancements with respect to the Standard Model can arise even for small modifications of the Higgs couplings. In particular, we find that triple Higgs production provides the best multiparticle channel to look for these deviations. We briefly explore the consequences of multiparticle production at the LHC.