A hot and dense state of nuclear matter, known as the quark-gluon plasma, is created in collisions of ultrarelativistic heavy nuclei. Highly energetic quarks and gluons, collectively referred to as partons, lose energy as they travel through this matter, leading to suppressed production of particles with large transverse momenta ($p_\mathrm{T}$). Conversely, high-$p_\mathrm{T}$ particle suppression has not been seen in proton-lead collisions, raising questions regarding the minimum system size required to observe parton energy loss. Oxygen-oxygen (OO) collisions examine a region of effective system size that lies between these two extreme cases. The CMS detector at the CERN LHC has been used to quantify charged-particle production in inclusive OO collisions for the first time via measurements of the nuclear modification factor ($R_\mathrm{AA}$). The $R_\mathrm{AA}$ is derived by comparing particle production to expectations based on proton-proton (pp) data and has a value of unity in the absence of nuclear effects. The data for OO and pp collisions at a nucleon-nucleon center-of-mass energy $\sqrt{s_\mathrm{NN}}$ = 5.36 TeV correspond to integrated luminosities of 6.1 nb$^{-1}$ and 1.02 pb$^{-1}$, respectively. The $R_\mathrm{AA}$ is below unity with a minimum of 0.69 $\pm$ 0.04 around $p_\mathrm{T}$ = 6 GeV. The data exhibit better agreement with theoretical models incorporating parton energy loss as compared to baseline models without energy loss.
Inclusive charged particle spectra for pp collisions at 5.36 TeV for $3 < p_{T} (GeV) <103.6$. The errors represent statistical, systematics and normalization uncertainties.
Inclusive charged particle spectra for OO collisions at 5.36 TeV for $3 < p_{T} (GeV) <103.6$. The errors represent statistical, systematics and normalization uncertainties.
Inclusive charged particle R_{AA} for 5.36 TeV OO collisions for $3 < p_{T} (GeV) <103.6$. The errors represent statistical, systematics and normalization uncertainties.
Parton energy loss in the quark-gluon plasma (QGP) is studied with a measurement of photon-tagged jet production in 1.7 nb$^{-1}$ of Pb+Pb data and 260 pb$^{-1}$ of $pp$ data, both at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV, with the ATLAS detector. The process $pp \to \gamma$+jet+$X$ and its analogue in Pb+Pb collisions is measured in events containing an isolated photon with transverse momentum ($p_\mathrm{T}$) above $50$ GeV and reported as a function of jet $p_\mathrm{T}$. This selection results in a sample of jets with a steeply falling $p_\mathrm{T}$ distribution that are mostly initiated by the showering of quarks. The $pp$ and Pb+Pb measurements are used to report the nuclear modification factor, $R_\mathrm{AA}$, and the fractional energy loss, $S_\mathrm{loss}$, for photon-tagged jets. In addition, the results are compared with the analogous ones for inclusive jets, which have a significantly smaller quark-initiated fraction. The $R_\mathrm{AA}$ and $S_\mathrm{loss}$ values are found to be significantly different between those for photon-tagged jets and inclusive jets, demonstrating that energy loss in the QGP is sensitive to the colour-charge of the initiating parton. The results are also compared with a variety of theoretical models of colour-charge-dependent energy loss.
The differential cross-section of photon-tagged jets as a function of jet $p_{\mathrm{T}}$ in pp collisions.
The yields of photon-tagged jets as a function of jet $p_{\mathrm{T}}$ in Pb+Pb collisions for different centrality intervals.
The nuclear modification factor of photon-tagged jets as a function of jet $p_{\mathrm{T}}$ for different centrality intervals.
This paper presents measurements of charged-hadron spectra obtained in $pp$, $p$+Pb, and Pb+Pb collisions at $\sqrt{s}$ or $\sqrt{s_{_\text{NN}}}=5.02$ TeV, and in Xe+Xe collisions at $\sqrt{s_{_\text{NN}}}=5.44$ TeV. The data recorded by the ATLAS detector at the LHC have total integrated luminosities of 25 pb${}^{-1}$, 28 nb${}^{-1}$, 0.50 nb${}^{-1}$, and 3 $\mu$b${}^{-1}$, respectively. The nuclear modification factors $R_{p\text{Pb}}$ and $R_\text{AA}$ are obtained by comparing the spectra in heavy-ion and $pp$ collisions in a wide range of charged-particle transverse momenta and pseudorapidity. The nuclear modification factor $R_{p\text{Pb}}$ shows a moderate enhancement above unity with a maximum at $p_{\mathrm{T}} \approx 3$ GeV; the enhancement is stronger in the Pb-going direction. The nuclear modification factors in both Pb+Pb and Xe+Xe collisions feature a significant, centrality-dependent suppression. They show a similar distinct $p_{\mathrm{T}}$-dependence with a local maximum at $p_{\mathrm{T}} \approx 2$ GeV and a local minimum at $p_{\mathrm{T}} \approx 7$ GeV. This dependence is more distinguishable in more central collisions. No significant $|\eta|$-dependence is found. A comprehensive comparison with several theoretical predictions is also provided. They typically describe $R_\text{AA}$ better in central collisions and in the $p_{\mathrm{T}}$ range from about 10 to 100 GeV.
- - - - - - - - - - - - - - - - - - - - <br><b>charged-hadron spectra:</b> <br><i>pp reference:</i> <a href="?version=1&table=Table1">for p+Pb</a> <a href="?version=1&table=Table10">for Pb+Pb</a> <a href="?version=1&table=Table19">for Xe+Xe</a> <br><i>p+Pb:</i> <a href="?version=1&table=Table2">0-5%</a> <a href="?version=1&table=Table3">5-10%</a> <a href="?version=1&table=Table4">10-20%</a> <a href="?version=1&table=Table5">20-30%</a> <a href="?version=1&table=Table6">30-40%</a> <a href="?version=1&table=Table7">40-60%</a> <a href="?version=1&table=Table8">60-90%</a> <a href="?version=1&table=Table9">0-90%</a> <br><i>Pb+Pb:</i> <a href="?version=1&table=Table11">0-5%</a> <a href="?version=1&table=Table12">5-10%</a> <a href="?version=1&table=Table13">10-20%</a> <a href="?version=1&table=Table14">20-30%</a> <a href="?version=1&table=Table15">30-40%</a> <a href="?version=1&table=Table16">40-50%</a> <a href="?version=1&table=Table17">50-60%</a> <a href="?version=1&table=Table18">60-80%</a> <br><i>Xe+Xe:</i> <a href="?version=1&table=Table20">0-5%</a> <a href="?version=1&table=Table21">5-10%</a> <a href="?version=1&table=Table22">10-20%</a> <a href="?version=1&table=Table23">20-30%</a> <a href="?version=1&table=Table24">30-40%</a> <a href="?version=1&table=Table25">40-50%</a> <a href="?version=1&table=Table26">50-60%</a> <a href="?version=1&table=Table27">60-80%</a> </br>- - - - - - - - - - - - - - - - - - - - <br><b>nuclear modification factors (p<sub>T</sub>):</b> <br><i>R<sub>pPb</sub>:</i> <a href="?version=1&table=Table28">0-5%</a> <a href="?version=1&table=Table29">5-10%</a> <a href="?version=1&table=Table30">10-20%</a> <a href="?version=1&table=Table31">20-30%</a> <a href="?version=1&table=Table32">30-40%</a> <a href="?version=1&table=Table33">40-60%</a> <a href="?version=1&table=Table34">60-90%</a> <a href="?version=1&table=Table35">0-90%</a> <br><i>R<sub>AA</sub> (Pb+Pb):</i> <a href="?version=1&table=Table36">0-5%</a> <a href="?version=1&table=Table37">5-10%</a> <a href="?version=1&table=Table38">10-20%</a> <a href="?version=1&table=Table39">20-30%</a> <a href="?version=1&table=Table40">30-40%</a> <a href="?version=1&table=Table41">40-50%</a> <a href="?version=1&table=Table42">50-60%</a> <a href="?version=1&table=Table43">60-80%</a> <br><i>R<sub>AA</sub> (Xe+Xe):</i> <a href="?version=1&table=Table44">0-5%</a> <a href="?version=1&table=Table45">5-10%</a> <a href="?version=1&table=Table46">10-20%</a> <a href="?version=1&table=Table47">20-30%</a> <a href="?version=1&table=Table48">30-40%</a> <a href="?version=1&table=Table49">40-50%</a> <a href="?version=1&table=Table50">50-60%</a> <a href="?version=1&table=Table51">60-80%</a> </br>- - - - - - - - - - - - - - - - - - - - <br><b>nuclear modification factors (y*/eta):</b> <br><i>R<sub>pPb</sub>:</i> <br> 0-5%: <a href="?version=1&table=Table52">0.66-0.755GeV</a> <a href="?version=1&table=Table53">2.95-3.35GeV</a> <a href="?version=1&table=Table54">7.65-8.8GeV</a> <a href="?version=1&table=Table55">15.1-17.3GeV</a> <br> 5-10%: <a href="?version=1&table=Table56">0.66-0.755GeV</a> <a href="?version=1&table=Table57">2.95-3.35GeV</a> <a href="?version=1&table=Table58">7.65-8.8GeV</a> <a href="?version=1&table=Table59">15.1-17.3GeV</a> <br> 10-20%: <a href="?version=1&table=Table60">0.66-0.755GeV</a> <a href="?version=1&table=Table61">2.95-3.35GeV</a> <a href="?version=1&table=Table62">7.65-8.8GeV</a> <a href="?version=1&table=Table63">15.1-17.3GeV</a> <br> 20-30%: <a href="?version=1&table=Table64">0.66-0.755GeV</a> <a href="?version=1&table=Table65">2.95-3.35GeV</a> <a href="?version=1&table=Table66">7.65-8.8GeV</a> <a href="?version=1&table=Table67">15.1-17.3GeV</a> <br> 30-40%: <a href="?version=1&table=Table68">0.66-0.755GeV</a> <a href="?version=1&table=Table69">2.95-3.35GeV</a> <a href="?version=1&table=Table70">7.65-8.8GeV</a> <a href="?version=1&table=Table71">15.1-17.3GeV</a> <br> 40-60%: <a href="?version=1&table=Table72">0.66-0.755GeV</a> <a href="?version=1&table=Table73">2.95-3.35GeV</a> <a href="?version=1&table=Table74">7.65-8.8GeV</a> <a href="?version=1&table=Table75">15.1-17.3GeV</a> <br> 60-90%: <a href="?version=1&table=Table76">0.66-0.755GeV</a> <a href="?version=1&table=Table77">2.95-3.35GeV</a> <a href="?version=1&table=Table78">7.65-8.8GeV</a> <a href="?version=1&table=Table79">15.1-17.3GeV</a> <br> 0-90%: <a href="?version=1&table=Table80">0.66-0.755GeV</a> <a href="?version=1&table=Table81">2.95-3.35GeV</a> <a href="?version=1&table=Table82">7.65-8.8GeV</a> <a href="?version=1&table=Table83">15.1-17.3GeV</a> <br><i>R<sub>AA</sub> (Pb+Pb):</i> <br> 0-5%: <a href="?version=1&table=Table84">1.7-1.95GeV</a> <a href="?version=1&table=Table85">6.7-7.65GeV</a> <a href="?version=1&table=Table86">20-23GeV</a> <a href="?version=1&table=Table87">60-95GeV</a> <br> 5-10%: <a href="?version=1&table=Table88">1.7-1.95GeV</a> <a href="?version=1&table=Table89">6.7-7.65GeV</a> <a href="?version=1&table=Table90">20-23GeV</a> <a href="?version=1&table=Table91">60-95GeV</a> <br> 10-20%: <a href="?version=1&table=Table92">1.7-1.95GeV</a> <a href="?version=1&table=Table93">6.7-7.65GeV</a> <a href="?version=1&table=Table94">20-23GeV</a> <a href="?version=1&table=Table95">60-95GeV</a> <br> 20-30%: <a href="?version=1&table=Table96">1.7-1.95GeV</a> <a href="?version=1&table=Table97">6.7-7.65GeV</a> <a href="?version=1&table=Table98">20-23GeV</a> <a href="?version=1&table=Table99">60-95GeV</a> <br> 30-40%: <a href="?version=1&table=Table100">1.7-1.95GeV</a> <a href="?version=1&table=Table101">6.7-7.65GeV</a> <a href="?version=1&table=Table102">20-23GeV</a> <a href="?version=1&table=Table103">60-95GeV</a> <br> 40-50%: <a href="?version=1&table=Table104">1.7-1.95GeV</a> <a href="?version=1&table=Table105">6.7-7.65GeV</a> <a href="?version=1&table=Table106">20-23GeV</a> <a href="?version=1&table=Table107">60-95GeV</a> <br> 50-60%: <a href="?version=1&table=Table108">1.7-1.95GeV</a> <a href="?version=1&table=Table109">6.7-7.65GeV</a> <a href="?version=1&table=Table110">20-23GeV</a> <a href="?version=1&table=Table111">60-95GeV</a> <br> 60-80%: <a href="?version=1&table=Table112">1.7-1.95GeV</a> <a href="?version=1&table=Table113">6.7-7.65GeV</a> <a href="?version=1&table=Table114">20-23GeV</a> <a href="?version=1&table=Table115">60-95GeV</a> <br><i>R<sub>AA</sub> (Xe+Xe):</i> <br> 0-5%: <a href="?version=1&table=Table116">1.7-1.95GeV</a> <a href="?version=1&table=Table117">6.7-7.65GeV</a> <a href="?version=1&table=Table118">20-23GeV</a> <br> 5-10%: <a href="?version=1&table=Table119">1.7-1.95GeV</a> <a href="?version=1&table=Table120">6.7-7.65GeV</a> <a href="?version=1&table=Table121">20-23GeV</a> <br> 10-20%: <a href="?version=1&table=Table122">1.7-1.95GeV</a> <a href="?version=1&table=Table123">6.7-7.65GeV</a> <a href="?version=1&table=Table124">20-23GeV</a> <br> 20-30%: <a href="?version=1&table=Table125">1.7-1.95GeV</a> <a href="?version=1&table=Table126">6.7-7.65GeV</a> <a href="?version=1&table=Table127">20-23GeV</a> <br> 30-40%: <a href="?version=1&table=Table128">1.7-1.95GeV</a> <a href="?version=1&table=Table129">6.7-7.65GeV</a> <a href="?version=1&table=Table130">20-23GeV</a> <br> 40-50%: <a href="?version=1&table=Table131">1.7-1.95GeV</a> <a href="?version=1&table=Table132">6.7-7.65GeV</a> <a href="?version=1&table=Table133">20-23GeV</a> <br> 50-60%: <a href="?version=1&table=Table134">1.7-1.95GeV</a> <a href="?version=1&table=Table135">6.7-7.65GeV</a> <a href="?version=1&table=Table136">20-23GeV</a> <br> 60-80%: <a href="?version=1&table=Table137">1.7-1.95GeV</a> <a href="?version=1&table=Table138">6.7-7.65GeV</a> <a href="?version=1&table=Table139">20-23GeV</a> <br>- - - - - - - - - - - - - - - - - - - -
Charged-hadron cross-section in pp collisions. The systematic uncertainties are described in the section 7 of the paper. The total systematic uncertainties are determined by adding the contributions from all relevant sources in quadrature.
Charged-hadron spectrum in the centrality interval 0-5% for p+Pb, divided by 〈TPPB〉. The systematic uncertainties are described in the section 7 of the paper. The total systematic uncertainties are determined by adding the contributions from all relevant sources in quadrature.
The ATLAS detector at the Large Hadron Collider has been used to measure jet substructure modification and suppression in Pb+Pb collisions at a nucleon-nucleon center-of-mass energy $\sqrt{s_{_\mathrm{NN}}}=5.02~\mathrm{TeV}$ in comparison with $pp$ collisions at $\sqrt{s}=5.02~\mathrm{TeV}$. The Pb+Pb data, collected in 2018, have an integrated luminosity of $1.72~\mathrm{nb^{-1}}$, while the $pp$ data, collected in 2017, have an integrated luminosity of $260~\mathrm{pb}^{-1}$. Jets used in this analysis are clustered using the anti-$k_{t}$ algorithm with a radius parameter $R=0.4$. The jet constituents, defined by both tracking and calorimeter information, are used to determine the angular scale $r_\mathrm{g}$ of the first hard splitting inside the jet by reclustering them using the Cambridge-Aachen algorithm and employing the soft-drop grooming technique. The nuclear modification factor, $R_\mathrm{AA}$, used to characterize jet suppression in Pb+Pb collisions, is presented differentially in $r_\mathrm{g}$, jet transverse momentum, and in intervals of collision centrality. The $R_\mathrm{AA}$ value is observed to depend significantly on jet $r_\mathrm{g}$. Jets produced with the largest measured $r_\mathrm{g}$ are found to be twice as suppressed as those with the smallest $r_\mathrm{g}$ in central Pb+Pb collisions. The $R_\mathrm{AA}$ values do not exhibit a strong variation with jet $p_\mathrm{T}$ in any of the $r_\mathrm{g}$ intervals. The $r_\mathrm{g}$ and $p_\mathrm{T}$ dependence of jet $R_\mathrm{AA}$ is qualitatively consistent with a picture of jet quenching arising from coherence and provides the most direct evidence in support of this approach.
Summary of jet double differential cross section in pp collisions at 5.02 TeV as a function of pT in bins of rg. Uncertainties are statistical and systematic, respectively.
Summary of jet double differential cross section in pp collisions at 5.02 TeV as a function of rg in bins of pT. Uncertainties are statistical and systematic, respectively.
Summary of per-event jet yields in Pb+Pb collisions at 5.02 TeV as a function of pT in bins of rg for 50-80% centrality interval, normalized by the respective centrality interval's <TAA>. Uncertainties are statistical and systematic, respectively.
Heavy-flavour hadron production provides information about the transport properties and microscopic structure of the quark-gluon plasma created in ultra-relativistic heavy-ion collisions. A measurement of the muons from semileptonic decays of charm and bottom hadrons produced in Pb+Pb and $pp$ collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV with the ATLAS detector at the Large Hadron Collider is presented. The Pb+Pb data were collected in 2015 and 2018 with sampled integrated luminosities of $208~\mathrm{\mu b}^{-1}$ and $38~\mathrm{\mu b^{-1}}$, respectively, and $pp$ data with a sampled integrated luminosity of $1.17~\mathrm{pb}^{-1}$ were collected in 2017. Muons from heavy-flavour semileptonic decays are separated from the light-flavour hadronic background using the momentum imbalance between the inner detector and muon spectrometer measurements, and muons originating from charm and bottom decays are further separated via the muon track's transverse impact parameter. Differential yields in Pb+Pb collisions and differential cross sections in $pp$ collisions for such muons are measured as a function of muon transverse momentum from 4 GeV to 30 GeV in the absolute pseudorapidity interval $|\eta| < 2$. Nuclear modification factors for charm and bottom muons are presented as a function of muon transverse momentum in intervals of Pb+Pb collision centrality. The measured nuclear modification factors quantify a significant suppression of the yields of muons from decays of charm and bottom hadrons, with stronger effects for muons from charm hadron decays.
Summary of charm muon double differential cross section in pp collisions at 5.02 TeV as a function of pT. Uncertainties are statistical and systematic, respectively.
Summary of charm muon per-event invariant yields in Pb+Pb collisions at 5.02 TeV as a function of pT for five different centrality intervals. Uncertainties are statistical and systematic, respectively.
Summary of bottom muon per-event invariant yields in Pb+Pb collisions at 5.02 TeV as a function of pT for five different centrality intervals. Uncertainties are statistical and systematic, respectively.
Measurements of the yield and nuclear modification factor, $R_\mathrm{ AA}$, for inclusive jet production are performed using 0.49 nb$^{-1}$ of Pb+Pb data at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV and 25 pb$^{-1}$ of $pp$ data at $\sqrt{s}=5.02$ TeV with the ATLAS detector at the LHC. Jets are reconstructed with the anti-$k_t$ algorithm with radius parameter $R=0.4$ and are measured over the transverse momentum range of 40-1000 GeV in six rapidity intervals covering $|y|<2.8$. The magnitude of $R_\mathrm{ AA}$ increases with increasing jet transverse momentum, reaching a value of approximately 0.6 at 1 TeV in the most central collisions. The magnitude of $R_\mathrm{ AA}$ also increases towards peripheral collisions. The value of $R_\mathrm{ AA}$ is independent of rapidity at low jet transverse momenta, but it is observed to decrease with increasing rapidity at high transverse momenta.
The ⟨TAA⟩ and ⟨Npart⟩ values and their uncertainties in each centrality bin.
No description provided.
No description provided.
Inclusive $\Upsilon$(1S) and $\Upsilon$(2S) production have been measured in Pb-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{_{\rm NN}}}=5.02$ TeV, using the ALICE detector at the CERN LHC. The $\Upsilon$ mesons are reconstructed in the centre-of-mass rapidity interval $2.5<y<4$ and in the transverse-momentum range $p_{\rm T}<15$ GeV/$c$, via their decays to muon pairs. In this Letter, we present results on the inclusive $\Upsilon$(1S) nuclear modification factor $R_{\rm AA}$ as a function of collision centrality, transverse momentum and rapidity. The $\Upsilon$(1S) and $\Upsilon$(2S) $R_{\rm AA}$, integrated over the centrality range 0-90%, are $0.37 \pm 0.02 {\rm{(stat)}}\pm 0.03 {\rm{(syst)}}$ and $0.10 \pm 0.04 {\rm{(stat)}}\pm 0.02 {\rm{(syst)}}$, respectively, leading to a ratio $R_{\rm{AA}}^{\Upsilon(\rm2S)}/R_{\rm{AA}}^{\Upsilon(\rm1S)}$ of $0.28\pm0.12\text{(stat)}\pm0.06\text{(syst)}$. The observed $\Upsilon$(1S) suppression increases with the centrality of the collision and no significant variation is observed as a function of transverse momentum and rapidity.
Inclusive $\Upsilon$(1S) $R_{\rm AA}$ and Pb-Pb yields for the centrality, transverse-momentum and rapidity ranges 0-90%, $0<p_{\rm T}<15$ GeV/$c$ and $2.5<y<4$, respectively. Statistical and systematic uncertainties are reported. (The yield is not normalized to the kinematic intervals).
Inclusive $\Upsilon$(1S) $R_{\rm AA}$ and Pb-Pb yields as a function of collision centrality. The transverse-momentum and rapidity ranges are $0<p_{\rm T}<15$ GeV/$c$ and $2.5<y<4$, respectively. Statistical and systematic uncertainties are reported. A global systematic uncertainty of 7.7% (4.9%) affects all the $R_{\rm AA}$ (yield) values. (The yields are not normalized to the kinematic intervals).
Inclusive $\Upsilon$(1S) $R_{\rm AA}$ and Pb-Pb yields as a function of transverse momentum. The centrality and rapidity ranges are 0-90% and $2.5<y<4$, respectively. Statistical and systematic uncertainties are reported. A global systematic uncertainty of 2.7% (2.3%) affects all the $R_{\rm AA}$ (yield) values.
Inclusive J/$\psi$ production is studied in Xe-Xe interactions at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\rm NN}}= 5.44$ TeV, using the ALICE detector at the CERN LHC. The J/$\psi$ meson is reconstructed via its decay into a muon pair, in the centre-of-mass rapidity interval $2.5<y<4$ and down to zero transverse momentum. In this Letter, the nuclear modification factors $R_{\rm AA}$ for inclusive J/$\psi$, measured in the centrality range 0-90% as well as in the centrality intervals 0-20% and 20-90% are presented. The $R_{\rm AA}$ values are compared to previously published results for Pb-Pb collisions at $\sqrt{s_{\rm NN}}= 5.02$ TeV and to the calculation of a transport model. A good agreement is found between Xe-Xe and Pb-Pb results as well as between data and the model.
Transverse momentum ($p_{\rm T}$) spectra of charged particles at mid-pseudorapidity in Xe-Xe collisions at $\sqrt{s_{\rm NN}}$ = 5.44 TeV measured with the ALICE apparatus at the Large Hadron Collider are reported. The kinematic range $0.15 < p_{\rm T} < 50$ GeV/$c$ and $|\eta| < 0.8$ is covered. Results are presented in nine classes of collision centrality in the 0-80% range. For comparison, a pp reference at the collision energy of $\sqrt{s}$ = 5.44 TeV is obtained by interpolating between existing \pp measurements at $\sqrt{s}$ = 5.02 and 7 TeV. The nuclear modification factors in central Xe-Xe collisions and Pb-Pb collisions at a similar center-of-mass energy of $\sqrt{s_{\rm NN}}$ = 5.02 TeV, and in addition at 2.76 TeV, at analogous ranges of charged particle multiplicity density $\left\langle\rm{d}N_{\rm ch}/\rm{d}\eta\right\rangle$ show a remarkable similarity at $p_{\rm T}> 10$ GeV/$c$. The comparison of the measured $R_{\rm AA}$ values in the two colliding systems could provide insight on the path length dependence of medium-induced parton energy loss. The centrality dependence of the ratio of the average transverse momentum $\left\langle p_{\rm{T}}\right\rangle$ in Xe-Xe collisions over Pb-Pb collision at $\sqrt{s}$ = 5.02 TeV is compared to hydrodynamical model calculations.
Transverse momentum spectra of charged particles in XeXe collisions in nine centrality classes.
Interpolated pp reference spectrum and invariant cross section.
Nuclear modification factor for XeXe. Additional systematic error: 0-5 pct data: +6.1 pct -6.1 pct 5-10 pct data: +6.6 pct -6.6 pct 10-20 pct data: +7.4 pct -7.4 pct 20-30 pct data: +9.8 pct -9.8 pct 30-40 pct data: +11.5 pct -11.5 pct 40-50 pct data: +12.9 pct -12.9 pct 50-60 pct data: +13.8 pct -13.8 pct 60-70 pct data: +14.0 pct -14.0 pct 70-80 pct data: +12.9 pct -12.9 pct
A measurement of $J/\psi$ and $\psi(2\mathrm{S})$ production is presented. It is based on a data sample from Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV and $pp$ collisions at $\sqrt{s}$ = 5.02 TeV recorded by the ATLAS detector at the LHC in 2015, corresponding to an integrated luminosity of $0.42\mathrm{nb}^{-1}$ and $25\mathrm{pb}^{-1}$ in Pb+Pb and $pp$, respectively. The measurements of per-event yields, nuclear modification factors, and non-prompt fractions are performed in the dimuon decay channel for $9 < p_{T}^{\mu\mu} < 40$ GeV in dimuon transverse momentum, and $-2.0 < y_{\mu\mu} < 2.0$ in rapidity. Strong suppression is found in Pb+Pb collisions for both prompt and non-prompt $J/\psi$, as well as for prompt and non-prompt $\psi(2\mathrm{S})$, increasing with event centrality. The suppression of prompt $\psi(2\mathrm{S})$ is observed to be stronger than that of $J/\psi$, while the suppression of non-prompt $\psi(2\mathrm{S})$ is equal to that of the non-prompt $J/\psi$ within uncertainties, consistent with the expectation that both arise from \textit{b}-quarks propagating through the medium. Despite prompt and non-prompt $J/\psi$ arising from different mechanisms, the dependence of their nuclear modification factors on centrality is found to be quite similar.
Per-event-yield of prompt jpsi production in 5.02 TeV PbPb collision data as a function of pT for three different centrality slices in the rapidity range |y| < 2.
Per-event-yield of non-prompt jpsi production in 5.02 TeV PbPb collision data as a function of pT for three different centrality slices in the rapidity range |y| < 2.
Non-prompt fraction of jpsi production in 5.02 TeV PbPb collision data as a function of pT for three different centrality slices in the rapidity range |y| < 2.
Forum