The global geometrical property of jet events in high-energy nuclear collisions

Abstract

We present the first theoretical study of medium modifications of the global geometrical pattern, i.e., transverse sphericity ($$S_{\perp }$$ S ⊥ ) distribution of jet events with parton energy loss in relativistic heavy-ion collisions. In our investigation, POWHEG + PYTHIA is employed to make an accurate description of transverse sphericity in the p + p baseline, which combines the next-to-leading order (NLO) pQCD calculations with the matched parton shower (PS). The Linear Boltzmann Transport (LBT) model of the parton energy loss is implemented to simulate the in-medium evolution of jets. We calculate the event normalized transverse sphericity distribution in central Pb + Pb collisions at the LHC, and give its medium modifications. An enhancement of transverse sphericity distribution at small $$S_{\perp }$$ S ⊥ region but a suppression at large $$S_{\perp }$$ S ⊥ region are observed in A + A collisions as compared to their p + p references, which indicates that in overall the geometry of jet events in Pb + Pb becomes more pencil-like. We demonstrate that for events with 2 jets in the final-state of heavy-ion collisions, the jet quenching makes the geometry more sphere-like with medium-induced gluon radiation. However, for events with $$\ge 3$$ ≥ 3 jets, parton energy loss in the QCD medium leads to the events more pencil-like due to jet number reduction, where less energetic jets may lose their energies and then fall off the jet selection kinematic cut. These two effects offset each other and in the end result in more jetty events in heavy-ion collisions relative to that in p + p.

Diffusion of charm quarks in jets in high-energy heavy-ion collisions

“…High-energy nuclear collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) provide excellent arena to unravel the properties of the quark-gluon plasma (QGP), a new state of nuclear matter with de-confined quarks and gluons, which is predicted to be formed at extreme hot and dense system by the Quantum Chromodynamics (QCD), the fundamental theory of strong interaction. In the past few decades, the "jet quenching" phenomenon, the energy loss of the initial-produced energic jet due to the strong interactions with the the constituents of the QGP, aroused physicists' great interest and has been extensively studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. These studies show that the differences between the finalstate observables at large transverse momentum, such as leading hadron spectra and jet production, in p+p and A+A collisions can help us gain insight into the mechanisms of in-medium parton interactions and precisely extract valuable information on the properties of the QGP created in relativistic heavy-ion collisions.…”

Jet quenching effect in relativistic heavy-ion collisions

“…文献 [70] 比值, 并与理论模型进行比较 [75] R AA p J T R AA ranges for the 0−10% centrality class as well as the comparison with model calculations [74] ; (b) the ratio of charged jet with R = 0.6 to that with R = 0.2 measured by ALICE [75] and the comparison with model calculations. 除了上述观测量, 实验上也测量强子-喷注 关联、喷注质量(jet mass) [78] 、喷注弥散(dispersion) [79] 、喷注尺寸(girth) [80,81] 、子喷注个数(subjettiness) [82] 、喷注电荷(jet charge) [83,84] 、喷注事件的整 体结构(global event shapes) [85] 等, 这些观测量都 子化非常敏感 [91] , 为理论模型带来了巨大的挑战.…”

Radial profile of bottom quarks in jets in high-energy nuclear collisions *

“…High-energy nuclear collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) provide an excellent arena to unravel the properties of quark-gluon plasma (QGP), a new state of nuclear matter with de-confined quarks and gluons, which is predicted to be formed in extreme hot and dense system by quantum chromodynamics (QCD), the fundamental theory of strong interaction. In the past few decades, the "jet quenching" phenomenon, the energy loss of the initially produced energic jet due to strong interactions with the constituents of QGP has garnered great interest from physicists and has been extensively studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. These studies show that the differences between the final-state observables at large transverse momentum, such as leading hadron spectra and jet production, in p+p and A+A collisions can help us gain insight into the mechanisms of in-medium parton interactions and precisely extract valuable information on the properties of QGP created in relativistic heavy-ion collisions.…”