119353603
Hadronic production of thermal photons
We study the thermal emission of photons from hot and dense strongly interacting hadronic matter at temperatures close to the expected phase transition to the quark-gluon plasma (QGP). Earlier calculations of photon radiation from ensembles of interacting mesons are reexamined with additional constraints, including new production channels as well as an assessment of hadronic form factor effects. Whereas strangeness-induced photon yields turn out to be moderate, the hitherto not considered $t$-channel exchange of $\ensuremath{\omega}$ mesons is found to contribute appreciably for photon energies above $\ensuremath{\sim}1.5\phantom{\rule{0.3em}{0ex}}\text{GeV}$. The role of baryonic effects is assessed using existing many-body calculations of lepton pair production. We argue that our combined results constitute a rather realistic emission rate, appropriate for applications in relativistic heavy-ion collisions. Supplemented with recent evaluations of QGP emission, and an estimate for primordial (hard) production, we compute photon spectra at Super Proton Synchrotron (SPS), Relativistic Heavy Ion Collider (RHIC), and Large Hadron Collider (LHC) energies.
17623252
Radiative and collisional energy loss, and photon-tagged jets at RHIC
The suppression of single jets at high transverse momenta in a quark–gluon plasma is studied at RHIC energies, and the additional information provided by a photon tag is included. The energy loss of hard jets traversing through the medium is evaluated in the AMY formalism, by consistently taking into account the contributions from radiative events and from elastic collisions at leading order in the coupling. The strongly interacting medium in these collisions is modeled with (3+1)-dimensional ideal relativistic hydrodynamics. Putting these ingredients together with a complete set of photon-production processes, we present a calculation of the nuclear modification of single jets and photon-tagged jets at RHIC.
18288865
Intermediate Mass Dileptons in Relativistic Nuclear Collisions
Abstract We consider the production of lepton pairs with intermediate masses, in relativistic nuclear collisions. Thermal sources are briefly discussed, as well as a newer production mechanism which involves jet-plasma interactions. Estimates for high p T lepton pairs are provided.
119423113
Statistical and dynamic models of charge balance functions
Charge balance functions, which identify balancing particle-antiparticle pairs on a statistical basis, have been shown to be sensitive to whether hadronization is delayed by several $\mathrm{fm}∕c$ in relativistic heavy ion collisions. Results from two classes of models are presented here, microscopic hadronic models and thermal models. The microscopic models give results which are contrary to recently published ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ balance functions from the STAR Collaboration, whereas the thermal model roughly reproduces the experimental results. This suggests that charge conservation is local at breakup, which is in line with expectations for a delayed hadronization. Predictions are also presented for balance functions binned as a function of ${Q}_{\mathrm{inv}}$.
119470761
Charged particle fluctuations and microscopic models of nuclear collisions
We study the event-by-event fluctuations of the charged particles and compare the results of different Monte-Carlo Generators (MCG): VNIb, HIJING, HIJING/B${\bar B}$ and RQMD. We find that the $D$-measure can be used to distinguish between the different gluon populations that are present in the MCG models. On the other hand, the value of the $D$-measure shows high sensitivity to the rescattering effects in VNIb model, but lower sensitivity to the rescattering effects in RQMD model. We also find that the $D$-measures from AA are consistent with the $D$-measures from $pp$ for all generators except VNIb. Therefore, any deviation among the values of $D$-measure for different impact parameters and between 
$pp$ and $AA$ collisions may indicate that either the rescattering effects play a key role in the interactions or there is new physics in $AA$ collisions.
121535698
Intermittency analysis of fragmenting nuclei with exact conservation laws
We show that the speculative charge bin size dependence of the scaled factorial moments for fragmenting nuclei in recent nuclear emulsion data may be attributed in part to simple conservation laws. Monte Carlo results from both the Thermodynamic Model and an Evaporation Model suggest that in such studies most or all of the effect is due to the fact that there exist constraints owing to conserved quantities.
7178771
Gamma Rays from Ultra-High-Energy Cosmic Rays in Cygnus A
Ultra-high-energy cosmic rays (UHECRs) accelerated in the jets of active galactic nuclei can accumulate in high magnetic field, ~100 kpc-scale regions surrounding powerful radio galaxies. Photohadronic processes involving UHECRs and photons of the extragalactic background light make ultrarelativistic electrons and positrons that initiate electromagnetic cascades, leading to the production of a γ-ray synchrotron halo. We calculate the halo emission in the case of Cygnus A and show that it should be detectable with the Fermi Gamma-Ray Space Telescope and possibly detectable with ground-based γ-ray telescopes if radio galaxies are the sources of UHECRs.