Semi-inclusive jets recoiling from $γ_{dir}$ and $π^{0}$ triggers in central Au+Au collisions at $\sqrt {s_{\rm NN}}$ = 200 GeV in STAR

Charged jet reconstruction in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV at RHIC

Jets represent an important tool to explore the properties of the hot and dense nuclear matter created in heavy-ion collisions. However, full jet reconstruction in such events is a challenging task due to extremely large and fluctuating background, which generates a large population of combinatorial jets that overwhelm the true hard jet population. In order to carry out accurate, data-driven jet measurements over a broad kinematic range in such conditions of small signal to background, we use several novel approaches in order to measure inclusive charged jet distributions and semi-inclusive ch…

Measurement of medium-induced modification of jet yield and acoplanarity using semi-inclusive $γ_{\text{dir}}$+jet and $π^{0}$+jet distributions in $p$+$p$ and central Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV by STAR

The STAR collaboration presents measurements of semi-inclusive distributions of charged jets recoiling from high transverse energy ($E_{\text{T}}$) direct photon and $π^{0}$ triggers in $p$+$p$ and central Au+Au collisions at $\sqrt{s_{\text{NN}}} = 200$ GeV. Jets are reconstructed from charged particles using the anti-$k_{\text{T}}$ algorithm with jet resolution parameters $R = 0.2$ and 0.5. The large uncorrelated background in central Au+Au collisions is corrected using a mixed-event technique. This enables a jet measurement extending to low transverse momentum and large $R$ with well-contro…

Search for jet quenching effects in high multiplicity pp collisions at $\sqrt{\mathrm{s}}$=13 TeV

The ALICE Collaboration reports a search for jet quenching effects in pp collisions at $\sqrt{\mathrm{s}}$=13 TeV, in events selected on high multiplicity compared to the minimum bias population. The measurement is based on the semi-inclusive acoplanarity distribution of jets recoiling from a high-$p_\mathrm{T}$ trigger hadron. Significant broadening of the recoil jet acoplanarity distribution is observed in high multiplicity pp collisions, in both data and in simulations based on the PYTHIA model. Analysis is ongoing to elucidate the origin of this effect.

利用直接光子+喷注和π⁰+喷注相关性测量中央Au-Au和pp碰撞中等离子体诱导的非共面性

Measurement of medium-induced acoplanarity in central Au-Au and pp collisions at $\sqrt{s_{\rm NN}}=200$ GeV using direct-photon+jet and $π^{0}$+jet correlations

STAR实验利用直接光子和π⁰触发测量Au-Au和pp碰撞中等离子体诱导的非共面性，发现喷注产量增强与理论模型不符。

Constraints on jet quenching in p-Pb collisions at $\mathbf{\sqrt{s_{NN}}}$ = 5.02 TeV measured by the event-activity dependence of semi-inclusive hadron-jet distributions

The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high-transverse momentum trigger hadron in p-Pb collisions at $\sqrt{s_{\rm NN}} =5.02$ TeV. Jets are reconstructed from charged-particle tracks using the anti-$k_{\rm T}$ algorithm with resolution parameter $R=0.2$ and $0.4$. A data-driven statistical approach is used to correct the uncorrelated background jet yield. Recoil jet distributions are reported for jet transverse momentum $15<p_{\rm T,jet}^{\rm ch} <50$ GeV/$c$ and are compared in various intervals of p-Pb event …

破解重离子碰撞中强子触发半包容反冲喷注的产额修正

Deciphering yield modification of hadron-triggered semi-inclusive recoil jets in heavy-ion collisions

本研究利用LBT模型模拟喷注输运，发现高横动量触发强子的淬火效应单独导致了重离子碰撞中$I_{\mathrm{AA}}$随喷注$p_{\mathrm{T}}$上升并可能超过1的实验现象。

在 $\sqrt{s_\mathrm{NN}} = 200$ GeV 的 $p+p$ 和中心 Au+Au 碰撞中测量的半单举直接光子+喷注与 $π^{0}$+喷注关联

Semi-inclusive direct photon+jet and $π^{0}$+jet correlations measured in $p+p$ and central Au+Au collisions at $\sqrt{s_\mathrm{NN}} = 200$ GeV

STAR 实验通过直接光子和中性 pion 触发的半单举喷注测量，在 200 GeV 金核-金核碰撞中研究了喷注淬灭对重建半径的依赖，发现小半径喷注压低更强，为介质能量输运机制提供了新约束。

Jet structure in 2.76 TeV Pb Pb collisions at ALICE

We present the analysis of the semi-inclusive distribution of reconstructed charged particle jets recoiling from a high pT hadron trigger in central Pb Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. We measure, subtract and unfold the large underlying event background in such collisions, utilizing a novel technique that does not impose fragmentation bias on the measured jet population. The Pb Pb measurements are compared to a pp PYTHIA reference distribution generated at the same $\sqrt{s}$. Modification of jet structure due to quenching is explored by varying the cone radius $R$ (0.2, 0.4) and th…

Measurement of jet quenching with semi-inclusive hadron-jet distributions in central Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV

We report the measurement of a new observable of jet quenching in central Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV, based on the semi-inclusive rate of charged jets recoiling from a high transverse momentum (high-$p_{\rm T}$) charged hadron trigger. Jets are measured using collinear-safe jet reconstruction with infrared cutoff for jet constituents of 0.15 GeV/$c$, for jet resolution parameters $R = 0.2$, 0.4 and 0.5. Underlying event background is corrected at the event-ensemble level, without imposing bias on the jet population. Recoil jet spectra are reported in the range $20<p_\ma…

Proton/Pion ratios in Δϕwith respect to a jet in sqrt{s_{NN}} =200 GeV Au+Au collisions at STAR

Inclusive Proton/pion ratios show an enhancement at intermediate transverse momentum (P_{T} ~ 1.5 - 4.0 GeV/c) in central sqrt{s_{NN}} = 200 GeV Au+Au collisions compared to peripheral Au+Au and p+p collisions. This effect suggests a production mechanism, different from fragmentation, which is consistent with coalescence and recombination models. A high E_{T} trigger particle selects a surface-biased jet, which is measured to have a similar p_{T} distribution as a p+p jet. This jet is used to enhance the quenching effects of the recoiling, medium traversing one. We reconstruct the trigger jet …

在 $\sqrt{s_{\rm NN}} = 200$ GeV 的 $p+p$ 和中心 Au+Au 碰撞中，利用直接光子+喷注和 $π^{0}$+喷注关联测量介质内喷注修正

Measurement of in-medium jet modification using direct photon+jet and $π^{0}$+jet correlations in $p+p$ and central Au+Au collisions at $\sqrt{s_{\rm NN}} = 200$ GeV

STAR Collaboration 测量了 200 GeV 下 p+p 和中心 Au+Au 碰撞中光子与中性介子触发的反冲喷注分布，发现介质诱导的喷注产额抑制在 R=0.2 时强于 0.5，揭示了喷注淬火的能量重分布角范围，且现有模型预测与观测不完全一致。

在 $\sqrt{s_{\rm NN}}=5.02$ TeV 的 pp 和中心 Pb$-$Pb 碰撞中使用半包含强子+喷注分布测量喷注淬火

Measurements of jet quenching using semi-inclusive hadron+jet distributions in pp and central Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV

ALICE 合作组在 $\sqrt{s_{\rm NN}}=5.02$ TeV 的 pp 和中心 Pb$-$Pb 碰撞中，利用数据驱动方法修正背景，测量了半包含反冲喷注分布，以探究喷注淬火效应并与理论计算进行比较。

STAR实验中的喷注产生

Production of Jets at STAR

STAR实验在200 GeV能量下测量不同碰撞系统的带电粒子喷注，探究事件活动关联、喷注淬火证据及介质中喷注修正，拓展了QCD研究的运动学范围。

Measurement of identified pi^0 and inclusive photon v_2 and implication to the direct photon production in sqrt(s_NN) = 200 GeV Au+Au collisions

The azimuthal distribution of identified pi^0 and inclusive photons has been measured in sqrt{s_{NN}} = 200 GeV Au+Au collisions with the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). The second harmonic parameter (v_2) was measured to describe the observed anisotropy of the azimuthal distribution. The measured inclusive photon v_2 is consistent with the value expected for the photons from hadron decay and is also consistent with the lack of direct photon signal over the measured p_T range 1-6 GeV/c. An attempt is made to extract v_2 of direct photons.

Jet Results in pp and Pb-Pb Collisions at ALICE

We report results on jet production in pp and Pb-Pb collisions at the LHC from the ALICE collaboration. The jet cross section in pp collisions at $\sqrt{s}$=2.76 TeV is presented, as well as the charged particle jet production cross section and measurements of the jet fragmentation and jet shape in pp collisions at $\sqrt{s}$=7 TeV. NLO pQCD calculations and simulations from MC event generators agree well with the data. Measurements of jets with a resolution parameter $R$=0.2 in Pb-Pb collisions at $\sqrt{s}_{NN}$=2.76 TeV show a strong, momentum dependent suppression in central events with re…

Centrality and Transverse Momentum Dependence of Collective Flow in 158 A GeV Pb+Pb Collisions Measured via Inclusive Photons

Directed and elliptic flow of inclusive photons near mid-rapidity in $158 $A GeV Pb+Pb collisions has been studied. The data have been obtained with the photon spectrometer LEDA of the WA98 experiment at the CERN SPS. The flow strength has been measured for various centralities as a function of $p_T$ and rapidity over $0.18 < p_T < 1.5 \mathrm{GeV}/c$ and $2.3 < y < 2.9$. The angular anisotropy has been studied relative to an event plane obtained in the target fragmentation region that shows the elliptic flow to be in-plane. The elliptic flow has also been studied using two-particle correlatio…