重味喷注是探究高能核碰撞中部分子在介质内的能量损失机制以及夸克-胶子等离子体（QGP）输运性质的有力工具。本工作首次对质心系能量$\u221as_{\ m NN}$=5.02 TeV的铅核-铅核（Pb+Pb）碰撞中，喷注内重味介子携带的纵向动量份额$z_{||}$开展理论研究。质子-质子（p+p）碰撞的基线结果由POWHEG+PYTHIA8提供，该框架将次领头阶硬过程与部分子簇射相匹配。我们采用一种考虑了碰撞型与辐射型部分子能量损失的蒙特卡洛输运模型，模拟重味喷注在膨胀的QGP介质中的演化过程。在p+p碰撞的相同运动学区间内，我们观测到$\rm{B^0}$介子喷注的$z_{||}$分布比$\rm{D^0}$介子喷注更陡，这可能是真空中b夸克喷注的碎裂函数比c夸克喷注更硬的一个迹象。在核-核（A+A）碰撞中，结果表明喷注淬火效应通常会降低$z_{||}$的数值。我们系统研究了喷注横动量$p_{\ m{T}}$、喷注半径$R$以及碰撞中心度等多个因素对$\rm{D^0}$介子喷注$z_{||}$分布的介质修正效应的影响。此外，我们预测，由于真空中$\rm{B^0}$介子喷注的初始$z_{||}$分布要陡得多，在相同的横动量区间内，$\rm{B^0}$介子喷注$z_{||}$分布的核修正效应明显强于$\rm{D^0}$介子喷注。
英文摘要：
Heavy-flavor jets are powerful tools to gain insight into the in-medium partonic energy-loss mechanisms and the quark-gluon plasma's (QGP) transport properties in high-energy nuclear collisions. In this work we present the first theoretical study of the longitudinal momentum fraction $z_{||}$ carried by heavy-flavor mesons in jets in Pb+Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The p+p baseline is provided by POWHEG+PYTHIA8, which matches the next-to-leading-order hard processes with the parton shower. We employ a Monte Carlo transport model, which considers the collisional and radiative partonic energy loss, to simulate the evolution of heavy-flavor jets in the expanding QGP medium. We observe steeper $z_{||}$ distributions of $\rm{B^0}$ jets compared to those of $\rm{D^0}$ jets at the same kinematics region in p+p collisions, which may be a hint of the harder jet fragmentation function of b jets compared to c jets in vacuum. In A+A collisions, it is shown that the jet quenching effect would generally decrease the values of $z_{||}$. We have made a systematical study on how several factors, including jet $p_{\rm{T}}$, jet radius $R$, and collision centrality, would influence the medium modification of $z_{||}$ distributions of a $\rm{D^0}$ jet. In addition, we predict visibly stronger nuclear modifications of $\rm{B^0}$-jet $z_{||}$ distributions compared to a $\rm{D^0}$ jet within the same $p_{\rm T}$ windows as a result of the much steeper initial $z_{||}$ distribution of the $\rm{B^0}$ jet in vacuum.
The phenomenon of jet quenching provides essential information about the properties of hot and dense matter created in ultra-relativistic heavy-ion collisions. Recent results from experiments at the Large Hadron Collider (LHC) show evidence for an unexpectedly similar suppression of both light and heavy flavor jets. Furthermore, the role of radiative energy loss of heavy quarks is still under active discussion within the theoretical community. By employing the parton cascade Boltzmann Approach to Multi-Parton Scatterings (BAMPS), which numerically solves the 3+1D Boltzmann equation both for li…
We study nonperturbative flavor correlations between pairs of leading and next-to-leading charged hadrons within jets at the Electron-Ion Collider (EIC). We introduce a charge correlation ratio observable $r_c$ that distinguishes same- and opposite-sign charged pairs. Using Monte Carlo simulations with different event generators, $r_c$ is examined as a function of various kinematic variables for different combinations of hadron species, and the feasibility of such measurements at the EIC is demonstrated. The precision hadronization study we propose will provide new tests of hadronization model…
Jets of collimated particles serve a multitude of purposes in high energy collisions. Recently, studies of jet interaction with the quark-gluon plasma (QGP) created in high energy heavy ion collisions are of growing interest, particularly towards understanding partonic energy loss in the QGP medium and its related modifications of the jet shower and fragmentation. Since the QGP is a colored medium, the extent of jet quenching and consequently, the transport properties of the medium are expected to be sensitive to fundamental properties of the jets such as the flavor of the parton that initiate…
Heavy quarks created in ultra-relativistic heavy-ion collisions are mostly produced in hard QCD processes during the early stages of the reaction. They interact with the hot and cold nuclear matter throughout the evolution of the medium via semi-hard and soft processes such as energy loss via gluon radiations and collisions. Nuclear modification of heavy flavors in p-A systems provides insight into cold nuclear matter effects such as (anti)shadowing and $k_{T}$-broadening, and serves as a baseline for A-A studies. In addition to that the fully reconstructed heavy-flavor jets provide additional…
Heavy flavor probes are sensitive to the properties of the quark gluon plasma (QGP) produced in relativistic heavy-ion collisions. A huge amount of effort has been devoted to studying different aspects of the heavy-ion collisions using heavy flavor particles. In this work, we study the dynamics of heavy quark transport in the QGP medium using the rapidity dependence of heavy flavor observables. We calculate the nuclear modification of $\text{B}$ and $\text{D}$ meson spectra as well as spectra of leptons from heavy flavor decays in the rapidity range $[-4.0,4.0]$. We use an implementation of th…
Jet substructure of light and heavy flavor jets at RHIC
Stony Brook University（石溪大学）；Georgia State University（佐治亚州立大学）；Center for Frontiers in Nuclear Science, Stony Brook University（石溪大学核科学前沿中心）；Jefferson Lab（杰斐逊实验室）
n these proceedings I discuss several recent developments in the physics of heavy flavor jets in heavy ion collisions. i) The dijet mass modification in nucleus-nucleus reactions has been proposed as a new observable with enhanced sensitivity to parton energy loss in nuclear matter. It also enables more precise studies of heavy quark mass effects on parton shower formation. ii) Computational techniques from soft-collinear effective theory have allowed us to bridge the gap between high energy and heavy ion QCD phenomenology. I show the first application of the semi-inclusive jet function formal…
The cross section of associated production of a Z boson with heavy flavor jets in $pp$ collisions is calculated using the SHERPA Monte Carlo generator and the analytical combined QCD approach based on kt-factorization at small x and conventional collinear QCD at large x. A satisfactory description of the ATLAS and CMS data on the $p_T$ spectra of Z bosons and c-jets in the whole rapidity, y, region is shown. Searching for the intrinsic charm (IC) contribution in these processes, which could be visible at large y > 1.5, we study observables very sensitive to non-zero IC contributions and less a…
We present a new method to expose the dead cone effect at colliders using iterative declustering techniques. Iterative declustering allows to unwind the jet clustering and to access the subjets or branches at different depths of the jet tree. Our method consists on declustering the heavy flavour-tagged jet using Cambridge-Achen algorithm following the branch containing the heavy flavour at each step and registering the kinematics of the complementary untagged prong. The kinematics of the complementary untagged prong fill a Lund map representing the gluon radiation off the heavy flavour quark a…
This paper introduces and applies a method for propagating changes in jet energy corrections into a D0 top quark mass measurement. It will serve as a source for the PRL presenting it's final results, and will be later published in a journal, or as a part of the author's PhD thesis. Motivation for the present measurement arises from the recalibration of the D0 flavor-dependent jet energy corrections. The recalibration was driven by the observation that the corrections for D0 Run IIb differ notably from those of Run IIa. The recalibration analysis was able to show that the Run IIb corrections sh…
In these proceedings, we discuss the role of heavy quark mass on the formation of parton showers. Mass effects are not well understood when parton branching occurs in nuclear matter, such as the quark-gluon plasma. Recently, a theoretically consistent picture of open heavy flavor production in ultra relativistic nuclear collisions has begun to emerge based on effective theories of QCD, such as soft collinear effective theory with Glauber gluons. We show that implementation of in-medium splitting processes containing heavy quarks into next-to-leading order calculations of heavy flavor productio…
Simplex Demixing: Disentangling Multiple Light-Flavor Jets at Colliders
Massachusetts Institute of Technology（麻省理工学院）；Center for Theoretical Physics -- a Leinweber Institute（理论物理中心——莱因韦伯研究所）；The NSF AI Institute for Artificial Intelligence and Fundamental Interactions（美国国家科学基金会人工智能与基本相互作用人工智能研究所）
We present results for mass effects coming from secondary radiation of heavy quark pairs related to gluon splitting in the thrust distribution for e+e- collisions. The results are given in the dijet limit where the hard interaction scale and the scales related to collinear and soft radiation are widely separated. We account for the corresponding fixed-order corrections at O(alpha_s^2) and the summation of all logarithmic terms related to the hard, collinear and soft scales as well as the quark mass at N3LL order. We also remove the O(Lambda_QCD) renormalon in the partonic soft function leading…
Recently the LHCb collaboration has measured both longitudinal and transverse momentum distribution of hadrons produced inside $Z$-tagged jets in proton-proton collisions at the Large Hadron Collider. These distributions are commonly referred to as jet fragmentation functions and are characterized by the longitudinal momentum fraction $z_h$ of the jet carried by the hadron and the transverse momentum $j_\perp$ with respect to the jet direction. We derive a QCD formalism within Soft-Collinear Effective Theory to describe these distributions and find that the $z_h$-dependence provides informatio…
Heavy quarks are valuable probes of the electromagnetic field and the initial condition of the quark-gluon plasma (QGP) matter produced in high-energy nuclear collisions. Within an improved Langevin model that is coupled to a (3+1)-dimensional viscous hydrodynamic model, we explore the origin of the directed flow coefficient ($v_1$) of heavy mesons and their decay leptons, and its splitting ($Δv_{1}$) between opposite charges. We find that while the rapidity dependence of the heavy flavor $v_1$ is mainly driven by the titled energy density profile of the QGP with respect to the longitudinal di…
We discuss massive quark effects in the endpoint region $x \to 1$ of inclusive deep inelastic scattering, where the hadronic final state is collimated and thus represents a jet. In this regime heavy quark pairs are generated via secondary radiation, i.e. due to a gluon splitting in light quark initiated contributions starting at $\mathcal{O}(α_s^2)$ in the fixed-order expansion. Based on the factorization framework for massless quarks in Soft Collinear Effective Theory (SCET), we construct a variable flavor number scheme that deals with arbitrary hierarchies between the mass scale and the kine…
While "quark" and "gluon" jets are often treated as separate, well-defined objects in both theoretical and experimental contexts, no precise, practical, and hadron-level definition of jet flavor presently exists. To remedy this issue, we develop and advocate for a data-driven, operational definition of quark and gluon jets that is readily applicable at colliders. Rather than specifying a per-jet flavor label, we aggregately define quark and gluon jets at the distribution level in terms of measured hadronic cross sections. Intuitively, quark and gluon jets emerge as the two maximally separable …
The two-prong structure related to the leading subjets inside a reconstructed jet opens new avenues toward precision constraints on the in-medium modification of parton showers. In this talk, we present the first resummed calculation of the soft-dropped groomed momentum sharing distribution, or the jet splitting function, in heavy-ion collisions for both light jets and heavy flavor tagged jets. Existing light jet splitting function data from the STAR experiment at RHIC and the CMS experiment at LHC can be understood in the unified framework of soft-collinear effective theory with Glauber gluon…
