Conical Emission from Shock Waves in Ne(1-20 AGeV)+U Collisions

Abstract

The formation and propagation of high-density compression waves, e.g. Mach shock waves, in cold nuclear matter is studied by simulating high-energy nucleus-nucleus collisions of Ne with U in the energy range from E lab = 0.5 AGeV to 20 AGeV. In an ideal hydrodynamic approach, the high-density shock wave created by the small Ne nucleus passing through the heavy U nucleus is followed by a slower and more dilute Mach shock wave which causes conical emission of particles at the Mach cone angle. The conical emission originates from low-density regions with a small flow velocity comparable to the speed of sound. Moreover, it is shown that the angular distributions of emitted baryons clearly distinguish between a hydrodynamic approach and binary cascade processes used in the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) transport model.

Directed, Elliptic and Triangular Flows in Asymmetric Heavy Ion Collisions

“…energies of about 2 − 10 AGeV a systematic study of v 1 , v 2 and v 3 Fourier-coefficients of the azimuthal particle distributions measured in noncentral ANC with a special choice of impact parameter may help to essentially improve our understanding of the hadronic matter equation of state at high densities. In addition, under certain conditions, highest baryonic charge densities can be reached in these experiments [14], what could help clarifying the question, whether the mixed quark-hadron phase [7,8,15,16] or the predicted chiral quarkyonic phase [17,18,19,16] can be formed in this energy range.…”

“…First theoretical predictions in this energy region were made very recently [14] and they indicate a very rich picture of the physical phenomena in ANC to be investigated, e.g. the formation of high density Mach shock waves and their impact on the spatial distribution of the produced particles and heavier clusters.…”

“…, then there is sufficient room to vary the impact parameter in the experiment and to select values which are close to b AN C using an event-by-event analysis. In this case ANC allow us to scan the interior of the target nucleus, as well as to study in detail the variety of surface phenomena such as the surface formation of light nuclear fragments like deuterons, tritons, and heliums nuclei, the emission of high p T pions [30], the isospin dependence of hadron surface emission, conical emission due to Mach shock wave formation in the target [14], and so on.…”

“…Therefore, the semi-peripheral ANC would allow one to essentially reduce the effect of shadowing on one side of the formed fireball what could help to finally clarify the source of the strong antiflow of pions [30,33] with p T < 500 MeV observed at SIS energies [34] and predicted earlier [35,36]. Moreover, one can hope to study a rich structure of shock waves in hadronic matter (from conical emission to viscosity) occurring during semi-peripheral ANC [14].…”

Mach-like emission from nucleon scattering in proton-nucleus reactions

“…The picture is very similar to Mach Cone phenomenon. Recently, Rau et al [12] adopted the hydrodynamic model [13] and UrQMD [14] to simulate the Mach-like wave in the asymmetric system 20 Ne + 238 U at 1-20A GeV. They got clear Mach cone structure as the picture emerged in hydrodynamic dynamics.…”