Abstract
Traditionally, low-pT sector is used to infer the features of initial stages before QGP thermalization. On the other hand, recently acquired wealth of high-pT experimental data paves the way to utilize the high-pT particles energy loss in exploring the initial stages. We here study how four different commonly considered initial-stage scenarios which have the same temperature profile after, but differ in the 'temperature' profile before thermalization affect predictions of high-pT RAA and v2 observables. Contrary to common expectations, we obtain that high-pT v2 is insensitive to the initial stages of medium evolution, being unable to discriminate between different conditions. On the other hand, RAA is sensitive to these conditions, however, within the current errorbars, the sensitivity is not sufficient to distinguish between different initial stages. Moreover, we also reconsider the validity of widely-used procedure of fitting the energy loss parameters, individually for different initial-stage cases, to reproduce the experimentally observed RAA. We here find that previously reported sensitivity of v2 to different initial states is mainly a consequence of the RAA fitting procedure, which may lead to incorrect conclusions. On the other hand, if a global property, in particular the same average temperature, is imposed to tested temperature profiles, high sensitivity of high-pT v2 is again obtained. We however show that this sensitivity would not be a consequence of differences in initial, but rather final, stages. Consequently, the simultaneous study of high-pT RAA and v2, with consistent energy loss parametrization and stringently controlled temperature profiles, is necessary to assess sensitivity of different variables to differences in initial and final stages.
Highlights
It is firmly confirmed that a new state of matter— the quark-gluon plasma (QGP) [1,2], in which quarks, antiquarks and gluons are deconfined—is formed at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC)
High-p⊥ particles are used to study the nature of jet-medium interactions, while low-p⊥ particles are used to infer the bulk QGP properties
The main goal of this paper is to assess to what extent and through what observables the initial stages of QGP evolution can be restrained by exploiting the energy loss of high-p⊥ particles in the evolving medium
Summary
It is firmly confirmed that a new state of matter— the quark-gluon plasma (QGP) [1,2], in which quarks, antiquarks and gluons are deconfined—is formed at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Rare high transverse momentum (high-p⊥) particles, which are created immediately upon collision, are sensitive to all stages of QGP evolution, and are considered to be excellent probes [3,4,5,6] of this extreme form of matter. As these probes traverse the QGP, they lose energy, which is commonly assessed through high-p⊥ angular averaged (RAA) [7,8,9,10,11,12,13,14] and high-p⊥ angular differential (v2) [15,16,17,18,19] nuclear modification factors.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
