Opportunities with ultra-soft photons: Bremsstrahlung from stopping

We compute the spectra of bremsstrahlung photons for different stopping scenarios which give rise to different initial charge-rapidity distributions. In the light of novel experimental opportunities that may arise with a new heavy-ion detector ALICE-3 at the CERN LHC, we discuss how to discriminate between these stopping scenarios and how to disentangle bremsstrahlung photons from other photon sources.Comment: 6 pages, 3 figures, contribution to the proceedings of Quark Matter 202

Medium-modifications of g→ccˉg\to c \bar{c} splitting

We study medium-modifications of the gluon splitting into a quark and anti-quark pair. Applying the Baier-Dokshitzer-Mueller-Peign\'e-Schiff and Zakharov (BDMPS-Z) formalism, we derive a path-integral formula for the in-medium $g\to q \bar{q}$ splitting function in the close-to-eikonal limit. Our analysis shows that there are two qualitatively different medium effects: transverse momentum broadening of $q \bar{q}$ pairs and enhanced production of such pairs. We note that both effects are numerically sizeable if the average momentum transfer from the medium to the parton is at the quark mass scale. In ultra-relativistic heavy-ion collisions, this condition is realized by charm quarks, therefore we focus our numerical analysis on the medium-modifications of $g\to c \bar{c}$ splitting.Comment: 4 pages, 1 figure, contribution to the proceedings of the 20th International Conference on Strangeness in Quark Matter (SQM 2022

Quantum Scalar Corrections to the Gravitational Potentials on de Sitter Background

We employ the graviton self-energy induced by a massless, minimally coupled (MMC) scalar on de Sitter background to compute the quantum corrections to the gravitational potentials of a static point particle with a mass $M$. The Schwinger-Keldysh formalism is used to derive real and causal effective field equations. When evaluated at the one-loop order, the gravitational potentials exhibit a secular decrease in the observed gravitational coupling $G$. This can also be interpreted as a (time dependent) anti-screening of the mass $M$.Comment: 21 pages, uses LaTeX 2