Inclusive jet spectra in 2.76 TeV collisions from ALICE

Measurements of high-pT particle production in heavy-ion collisions at RHIC have shown that medium-induced energy loss affects the partons produced in the early stage of a heavy-ion col- lision. The increased initial production cross section for partons at LHC energies makes fully reconstructed jets available in a wide kinematic range, which allows for a more differential in- vestigation of parton energy loss. Partonic energy loss allows us to access key observables of the hot deconfined nuclear matter produced in heavy-ion collisions. The inclusive cross-section of reconstructed jets using the ALICE tracking detectors and electromagnetic calorimeter is pre- sented from data collected during the 2.76 TeV pp runs. The procedures used to reconstruct jets and extract them from a fluctuating background in Pb-Pb collisions are discussed.Comment: 4 pages, 3 figures, proceedings from Quark Matter 2012 at Washington D

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 respect to pp collisions. The centrality dependence of the suppression of charged particle jets relative to peripheral events is presented. The ratio of jet spectra with $R$=0.2 and $R$=0.3 is found to be similar in pp and Pb-Pb events. The analysis of the semi-inclusive distribution of charged particle jets recoiling from a high-$p_{\rm T}$ trigger hadron allows an unbiased measurement of the jet structure for larger cone radii.Comment: 4 pages, 3 figures, to appear in the proceedings of the 48th Rencontres de Moriond, La Thuile, Italy, March 9-16, 201

Inclusive jet spectra in 2.76 TeV collisions from ALICE

AbstractMeasurements of high-pT particle production in heavy-ion collisions at RHIC have shown that medium-induced energy loss affects the partons produced in the early stage of a heavy-ion collision. The increased initial production cross section for partons at LHC energies makes fully reconstructed jets available in a wide kinematic range, which allows for a more differential investigation of parton energy loss. Partonic energy loss allows us to access key observables of the hot deconfined nuclear matter produced in heavy-ion collisions. The inclusive cross-section of reconstructed jets using the ALICE tracking detectors and electromagnetic calorimeter is presented from data collected during the 2.76 TeV pp runs. The procedures used to reconstruct jets and extract them from a fluctuating background in Pb–Pb collisions are discussed

Measurement of jet spectra in Pb-Pb collisions at sNN\sqrt{s_{NN}}=2.76 TeV with the ALICE detector at the LHC

We report a measurement of transverse momentum spectra of jets detected with the ALICE detector in Pb-Pb collisions at sqrt(sNN)=2.76 TeV. Jets are reconstructed from charged particles using the anti-kt jet algorithm. The background from soft particle production is determined for each event and subtracted. The remaining influence of underlying event fluctuations is quantified by embedding different probes into heavy-ion data. The reconstructed transverse momentum spectrum is corrected for background fluctuations by unfolding. We compare the inclusive jet spectra reconstructed with R=0.2 and R=0.3 for different centrality classes and compare the jet yield in Pb-Pb and pp events.Comment: * Temporary entry *; 4 pages, 7 figures, proceedings from 5th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (Hard Probes 2012) at Cagliari (Italia

Results on Jet Spectra and Structure from ALICE

Full jet reconstruction in ALICE uses the combined information from charged and neutral particles. Essentially all jet constituents can be measured with large efficiency down to very low transverse momenta (pT > 150 MeV/c). This has the advantage to introduce a minimum bias on the jet fragmentation, in particular for low jet momenta and in the presence of quenching. In this article, we present preliminary results from reconstruction of charged jets in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV. The inclusive charged jet spectrum, the jet nuclear modification factors (R_AA, R_CP), the ratio of spectra measured with different resolution parameters and hadron-jet correlations are discussed. For pp data at the same center of mass energy, the inclusive spectrum of fully reconstructed jets and its resolution parameter dependence are reported.Comment: 8 pages, 11 figures; to be published in the Proceedings of Quark Matter 201

Correlations and flavors in jets in ALICE

We report on the measurement of hadron composition in charged jets in pp at $\sqrt{s}=7$ TeV and show the first data on particle type dependent jet fragmentation at the LHC. Further, we present $(\Lambda+\bar{\Lambda})/2$K$^{0}_{\mathrm{S}}$ ratios measured in charged jets in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 2.76$ TeV and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV. While the ratio of the inclusive $p_{\mathrm{T}}$ spectra of $\Lambda$ and K$^{0}_{\mathrm{S}}$ exhibits centrality dependent enhancement both in Pb-Pb and p-Pb system, the $(\Lambda+\bar{\Lambda})/2$K$^{0}_{\mathrm{S}}$ ratio measured in charged jets reveals that jet fragmentation does not contribute to the observed baryon anomaly. Finally, we discuss the measurement of semi-inclusive $p_{\mathrm{T}}$ spectra of charged jets that recoil from a high-$p_{\mathrm{T}}$ hadron trigger in Pb-Pb and pp collisions at $\sqrt{s_{\mathrm{NN}}} = 2.76$ TeV and $\sqrt{s} = 7$ TeV, respectively. The jet yield uncorrelated with the trigger hadron is removed at the event-ensemble level without introducing a bias on the jet population which is therefore infrared and collinear safe. The recoil jet yield in central Pb-Pb is found to be suppressed w.r.t. that from pp PYTHIA reference. On the other hand, there is no sign of intra-jet broadening even for anti-$k_{\mathrm{T}}$ jets with a resolution parameter as large as $R=0.5$.Comment: Proceedings of Strangeness in Quark Matter conference, 6 July - 11 July 2015, Dubna, Russi

Production of strange particles in charged jets in Pb--Pb and p--Pb collisions measured with ALICE

Measurements of spectra of identified particles produced in jets represent an important tool for understanding the interplay of various hadronisation mechanisms which contribute to particle production in the hot and dense medium created in ultra-relativistic heavy-ion collisions. In this contribution, we present the measurements of the pT spectra of {\Lambda} baryons and K0S mesons produced in charged jets in Pb--Pb collisions at sqrt(sNN) = 2.76 TeV and in p--Pb collisions at sqrt(sNN) = 5.02 TeV. The results are obtained with the ALICE detector at the LHC, exploiting the excellent particle identification capabilities of this experiment. Baryon-to-meson ratios of the spectra of strange particles associated with jets are studied in central collisions and are compared with the inclusive ratios.Comment: 4 pages, 2 figures, proceedings from the Hard Probes 2015 conference, to be published in Nuclear Physics B - Proceedings Supplement

Physics perspectives of heavy-ion collisions at very high energy

Heavy-ion collisions at very high colliding energies are expected to produce a quark-gluon plasma (QGP) at the highest temperature obtainable in a laboratory setting. Experimental studies of these reactions can provide an unprecedented range of information on properties of the QGP at high temperatures. We report theoretical investigations of the physics perspectives of heavy-ion collisions at a future high-energy collider. These include initial parton production, collective expansion of the dense medium, jet quenching, heavy-quark transport, dissociation and regeneration of quarkonia, photon and dilepton production. We illustrate the potential of future experimental studies of the initial particle production and formation of QGP at the highest temperature to provide constraints on properties of strongly interaction matter.Comment: 35 pages in Latex, 29 figure

Shining a Light on the QGP - Electroweak Probes Experimental Summary

Objects which are only subject to the electroweak force are an ideal probe of QCD in high density and temperature environments as they carry information about the conditions during their production out of the QGP without interacting with it. Thus they can be used to characterize the initial state as well as several properties of the QGP and its evolution. Within this article the recent results regarding these electroweak probes presented at the 9$^{th}$ Hard Probes Conference (Aix-les-Bains, France, 2018) will be summarized. In particular the following questions will be addressed: Can we determine the necessary energy and particle density for the QGP creation using electromagnetic probes? Can we use light-by-light scattering in heavy-ion collisions to do precision tests of QED and measure the magnetic field of the QGP? How are quark jets modified by the presence of the QGP? What can we learn about the initial state and scaling properties in pp, p(d)-A and A-A collisions from the production of high \pt\ photons, Z$^0$ and W$^\pm$ bosons? In the version provided on arXiv, additional plots are included in the appendix with respect to the version submitted for publication in the journal.Comment: 16 pages, 8 figures, 9th Hard Probes Conference (Aix-les-Bains, France, 2018), proceedings with additional figure