Mach Cone Induced By γ-Triggered Jets In High-Energy Heavy-Ion Collisions And Non-perturbative QCD Effects Of Jets In Pp Collision

Strong jet quenching has been observed in experimental data at the Relativistic Heavy-ion Collider (RHIC) in terms of suppression of large transverse momentum hadrons, back-to-back (b2b) dihadron andγ-hadron correlation in the central heavy-ion collisions. Such phenomena are consequences of jet-medium interaction and the induced parton energy loss during the prop-agation of energetic partons through the hot quark-gluon plasma in the early stage of heavy-ion collisions. The energy and momentum lost by a propagating parton will be carried by radiated gluons and recoiled medium partons which in turn will go through further interaction and even-tually lead to collective medium excitation such as supersonic waves or Mach cones. Indeed, Mach cones have been found in the solutions of both hydrodynamic response and linearized Einstein equations in string theory excited by a propagating jet. Such collective excitation by a propagating jet is expected to be responsible for the observed conic b2b azimuthal dihadron and trihadron correlations with a maximum opening angle ofΦ≈1 (rad) relative to the back-side of a triggered high-pT hadron. However, hadron spectra from the freeze-out of the Mach cone in both hydrodynamics with realistic energy-momentum deposition by jets and string calculations in the hydrodynamic regime fail to reproduce the observed conic azimuthal correlations. Such correlations on the other hand are observed in the AMPT Monte Carlo simulations which could come from jet induced wakes that are deflected by a radially expanding medium.In this paper, we will study the medium excitation by a propagating jet shower inside a quark-gluon plasma using a linear Boltzmann transport model and AMPT model. We will illus-trate that the azimuthal distribution of recoiled thermal partons from the primary jet-medium interaction inside a static QGP has a typical double-hump feature with respect to the initial jet direction. Further scattering of the recoiled partons inside the medium lead to a mach-cone-like propagation of the energy and momentum density.However, the double-hump feature in the angu-lar distribution of medium recoiled partons is significantly diminished and eventually disappears due to diffusion via secondary scatterings. The deflection of the jet shower and the Mach-cone-like excitation in an expanding medium will result in a double-peaked azimuthal distribution as observed in dihadron measurements. Because of the different geometric distributions and propagation direction of the initial produced jets, we will illustrate thatγ-hadron and dihadron azimuthal correlation will be quantitatively different, depending on the value of jet-medium cross section. We therefore propose to use comparative study ofγ-hadron and dihadron azimuthal cor- relations to shed light on the dynamics of jet-induced Mach-cone-like excitation in high-energy heavy-ion collisions.With the progress of experimental facilities, the RHIC has the ability to use full structures of a jet studying parton energy loss and recalculate RAA(pT) in heavy-ion collision. As the baseline, the full jet for pp collision is considered by perturbative QCD with reasonable approximation, while some results show non-perturbative QCD contributions to full jet's pt should be included. The non-perturbative effects'properties of pp collision should be precisely understood before studying heavy-ion collision. As the second part of this paper, we will study the non-perturbative QCD contributions to jet observables, calculating their dependence on the radius R, and on the colour and transverse momentum of the parton initiating the jet with collider energy in the RHIC, Tevatron, Large Hadron Collider (LHC) by using parton-shower Monte Carlo generators Pythia8.142. We will show that the hadronisation corrections decrease with values of R, behaving as 1/R, while underlying event contributions grow with the jet area as R2.We will illustrate that the hadronisation effect is dependent on partonic jet's transverse momentum and it should not be neglected in RHIC. We also will provide the approximate value of the radius"RNP=0" where the hadronisation and underlying-event corrections are cancelled. Exactly, these conclusions should be helpful to understand jet's non-perturbative effects,calculate RAA(pT) precisely and take advantage of the much flexibility offered by full jet.