Quark Matter 2014 - XXIV International Conference on Ultrarelativistic Nucleus-Nucleus Collisions

19-24 May 2014
Europe/Zurich timezone

Soft photon production from real-time dynamics of jet fragmentation

19 May 2014, 16:50
20m

helium

Contributed Talk Electromagnetic Probes

Speaker

Frasher Loshaj (Stony Brook University)

Description

Soft photons produced in heavy ion collisions are an important tool in probing the properties of the quark-gluon plasma. For this purpose, it is crucial to understand the background - soft photons produced in elementary collisions. Low theorem states that soft photon production in hadron collisions is dominated by Bremsstrahlung off charged initial and final state hadrons. Surprisingly, almost every experiment observed an enhancement (by a factor of $2\div 5$) above Low theorem's prediction. This is the longstanding puzzle of "anomalous soft photon production." The phenomenon is not observed in processes with leptonic final states, which suggests that the mechanism is due to nonperturbative QCD evolution. We study this phenomenon using an exactly soluble, massless, Abelian model in $1+1$ dimensions which shares with QCD many important properties: confinement, chiral symmetry breaking, axial anomaly and $\theta$-vacuum. We then apply this model to the soft photon production in the fragmentation of jets produced in $Z^0$ decays and find a qualitative agreement with the data.

Primary author

Frasher Loshaj (Stony Brook University)

Co-author

Dmitri Kharzeev (Stony Brook U./BNL)

 Slides