arXiv subjects

Sanghoon Lim

Publications and source records attributed to Sanghoon Lim.

23 records · Page 2Linked to original sources

arXiv2022

Model study on $Υ(nS)$ modification in small collision systems

Quarkonium production has been studied extensively in relativistic heavy-ion collision experiments to understand the properties of the quark gluon plasma. The experimental results on the yield modification in heavy-ion collisions relative to that in $p$+$p$ collisions can be described by several models considering dissociation and regeneration effects. A yield modification beyond initial-state effects has also been observed in small collision systems such as $p$+Au and $p$+Pb collisions, but it is still premature to claim any hot medium effect. A model study in various small collision systems such as $p$+$p$, $p$+Pb, $p$+O, and O+O collisions will help quantitatively understanding nuclear effects on the $Υ(nS)$ production. A theoretical calculation considering the gluo-dissociation and inelastic parton scattering and their inverse reaction reasonably describes the suppression of $Υ(1S)$ in Pb+Pb collisions. Based on this calculation, a Monte-Carlo simulation is developed to more realistically incorporate the medium produced in heavy-ion collisions with event-by-event initial collision geometry and hydrodynamic evolution. We extend this framework to small systems to study the medium effects. In this work, we quantify the nuclear modification factor of $Υ(nS)$ as a function of charged particle multiplicity ($dN_{ch}/dη$) and transverse momentum. We also calculate the elliptic flow of $Υ(nS)$ in small collision systems.

nucl-th↗

arXiv2021

$K_1/K^*$ enhancement as a signature of chiral symmetry restoration in heavy ion collisions

Based on the fact that the mass difference between the chiral partners is an order parameter of chiral phase transition and that the chiral order parameter reduces substantially at the chemical freeze-out point in ultra-relativistic heavy ion collisions, we argue that the production ratio of $K_1$ over $K^*$ in such collisions should be substantially larger than that predicted in the statistical hadronization model. We further show that while the enhancement effect might be contaminated by the relatively larger decrease of $K_1$ meson than $K^*$ meson during the hadronic phase, the signal will be visible through a systematic study on centrality as the kinetic freeze-out temperature is higher and the hadronic life time shorter in peripheral collisions than in central collisions.

nucl-th↗

arXiv2014

Measurement of electrons from heavy-flavor decays from $p$+$p$, $d$+Au, and Cu+Cu collisions in the PHENIX experiment

Charm and bottom quarks are formed predominantly by gluon fusion in the initial hard scatterings at RHIC, making them good probes of the full medium evolution. Previous measurements at RHIC have shown large suppression and azimuthal anisotropy of open heavy-flavor hadrons in Au+Au collisions at $\sqrt{s_{NN}}=200~{\rm GeV}$. Explaining the simultaneously large suppression and flow of heavy quarks has been challenging. To further understand the heavy-flavor transport in the hot and dense medium, it is imperative to also measure cold nuclear matter effects which affect the initial distribution of heavy quarks as well as the system size dependence of the final state suppression. In this talk, new measurements by the PHENIX collaboration of electrons from heavy-flavor decays in $p$+$p$, $d$+Au, and Cu+Cu collisions at $\sqrt{s_{NN}}=200~{\rm GeV}$ are presented. In particular, a surprising enhancement of intermediate transverse momentum heavy-flavor decay leptons in $d$+Au at mid and backward rapidity are also seen in mid-central Cu+Cu collisions. This enhancement is much larger than the expectation from anti-shadowing of the parton distributions and is theoretically unexplained.

nucl-ex↗

arXiv2014

PHENIX recent heavy flavor results

Cold nuclear matter (CNM) effects provide an important baseline for the interpretation of data in heavy ion collisions. Such effects include nuclear shadowing, Cronin effect, and initial patron energy loss, and it is interesting to study the dependence on impact parameter and kinematic region. Heavy quark production is a good measurement to probe the CNM effects particularly on gluons, since heavy quarks are mainly produced via gluon fusions at RHIC energy. The PHENIX experiment has experiment has ability to study the CNM effects by measuring heavy quark production in $d$$+$Au collisions at variety of kinematic ranges. Comparisons of heavy quark production at different rapidities allow us to study modification of gluon density function in the Au nucleus depending on momentum fraction. Furthermore, comparisons to the results from heavy ion collisions (Au$+$Au and Cu$+$Cu) measured by PHENIX provide insight into the role of CNM effects in such collisions. Recent PHENIX results on heavy quark production are discussed.

nucl-ex↗

arXiv2014

Open heavy flavor measurements in $d$$+$Au collisions at PHENIX experiment

The heavy quarks produced in the early stage of heavy-ion collisions are very effective probes of the dense partonic medium produced at RHIC. PHENIX has the ability to measure heavy quark production through single electrons in the central arm spectrometers ($|η|<0.35$) and single muons in the forward (backward) muon spectrometers ($1.2<|η|<2.2$). As these single leptons are from open heavy-flavor meson semi-leptonic decays, initial state cold nuclear matter effects on heavy quark production can be probed by measuring the single leptons in $d$$+$Au collisions. PHENIX have observed a large enhancement of heavy-flavor electrons in $d$$+$Au collisions at mid-rapidity, which indicates strong CNM effects on heavy quark production, in contrast to the suppression observed in Au$+$Au collisions. Measurement of single muons from open heavy flavor in $d$$+$Au collisions at forward (backward) rapidity provide detailed look into rapidity dependent CNM effects as well as the low (high) $x$ parton distribution function within Au nucleus. We discuss recent PHENIX heavy flavor measurements and how they expand our understanding of CNM effects and contribute to the interpretation of other results in heavy-ion collisions.

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