Two-particle correlation via Bremsstrahlung

Soyeon Cho,Kayoung Park ,J H Yoon

doi:10.1051/epjconf/201714108005

Abstract

Ridge is the well-known structure in two-particle angular correlations at highenergy heavy-ion collisions. This structure is physically understood through elliptic and higher-order flows at nucleus-nucleus collisions. This behavior is also found in small systems, such as proton-proton collisions, recently. However, Ridge structure in small system is hard to be understood using hydrodynamics, since small systems are not dense enough to produce the Quark-Gluon plasma. Thus, we try to describe this phenomena through kinematic interaction between jets and medium partons. In high-energy heavy-ion collision, the energetic particles called jets go out in specific direction and lose their energy while passing through the medium. During such process, photons/gluons are emitted from interaction between jets and medium partons. We concentrate on energy loss via photon radiations, known as Bremsstrahlung. Recently, two symmetric double scattering processes between jet particle and medium parton are reported to be able to produce certain constructive interference, which gives collective motion and medium partons are aligned along incoming jet particles. We conjecture that similar behavior might happen in Bremsstrahlung processes, and therefore we consider the two symmetric diagrams of photon emission and medium parton scattering. We expect these two amplitudes to give constructive interference leading to the collective motion of medium. We check the correlation between emitted photon and final jet, and those between medium parton and final jet for high-energy jet. To describe parton momentum distribution in medium, we use the Maxwell-Boltzmann distribution. We discover collective motion in both angular correlations. We also check the tendency of the angular correlation for two particles according to the incident angle of jet particle, energy of emitted photon and temperature of systems, respectively. We can conclude that collective motion is able to be understood through kinematic description.

Highlights

Ridge structure which is pseudo-rapidity independent shape is found in two-particle angular correlation for high-energy heavy-ion collisions
We consider two symmetric diagrams of γ emission and medium parton scattering as shown as Figure 1. We expect these two amplitudes give constructive interference leading to collective motion for medium, since the cross section is the absolute-square of the sum of amplitudes, as in equation (1)
We calculate the angular correlation for final jet particle and emitted photon and that for final jet particle and final medium parton

Summary

Introduction

Ridge structure which is pseudo-rapidity independent shape is found in two-particle angular correlation for high-energy heavy-ion collisions. This structure can be explained by hydrodynamics, especially elliptic and higer-order flows. Ridge structure is discovered in small systems such as proton-proton collisions with high energies Such case is understood through hydrodynamics but many physicist do not expect that hot and dense medium (Quark-Gluon plasma state) is produced at small systems, it should be understood carefully. The main interaction is gluon or photon radiation process, which gluons or photons are emitted by scattering between jet particles and medium partons. We attempt to produce Ridge structure from energy-loss mechanism of jets by emitting gluons or phtons. We consider only phton radiation process, known as Bremsstrahlung

Formalism

Results

Conclusion & Outlooks