Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe

Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in Pb-Pb collisions at root s(NN)=2.76TeV

The elliptic flow, v(2), of muons from heavy-flavour hadron decays at forward rapidity (2.5 <y <4) is measured in Pb-Pb collisions at root s(NN)= 2.76TeVwith the ALICE detector at the LHC. The scalar product, two- and four-particle Q cumulants and Lee-Yang zeros methods are used. The dependence of the v(2) of muons from heavy-flavour hadron decays on the collision centrality, in the range 0-40%, and on transverse momentum, p(T), is studied in the interval 3 <p(T)<10 GeV/c. A positive v(2) is observed with the scalar product and two-particle Q cumulants in semi-central collisions (10-20% and 20-40% centrality classes) for the p(T) interval from 3 to about 5GeV/c with a significance larger than 3 sigma, based on the combination of statistical and systematic uncertainties. The v(2) magnitude tends to decrease towards more central collisions and with increasing pT. It becomes compatible with zero in the interval 6 <p(T)<10 GeV/c. The results are compared to models describing the interaction of heavy quarks and open heavy-flavour hadrons with the high-density medium formed in high-energy heavy-ion collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe

Pseudorapidity and transverse-momentum distributions of charged particles in proton-proton collisions at root s=13 TeV

The pseudorapidity (eta) and transverse-momentum (p(T)) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy root s = 13 TeV. The pseudorapidity distribution in vertical bar eta vertical bar <1.8 is reported for inelastic events and for events with at least one charged particle in vertical bar eta vertical bar <1. The pseudorapidity density of charged particles produced in the pseudorapidity region vertical bar eta vertical bar <0.5 is 5.31 +/- 0.18 and 6.46 +/- 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 <p(T) <20 GeV/c and vertical bar eta vertical bar <0.8 for events with at least one charged particle in vertical bar eta vertical bar <1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Probing space-time evolution at the femtometer scale in pp and Pb-Pb collisions with ALICE

Quantum-mechanical effects and interactions cause correlations between particles with small momentum difference that carry information about the space-time evolution of the collision system on the femtometer scale. Measurements of these effects are usually done soon after new data arrive and provide an unique input to theoretical models. Nowadays, after almost a decade of the LHC operation and a significant amount of collected data, more differential and complex analyses are carried out. In this talk I will highlight the most recent ones, showing the direction in which the femtoscopic studies are currently advancing. Detailed studies of the azimuthal event shape have been performed with pion correlations. In Pb-Pb collisions, azimuthally-sensitive femtoscpy, measured with respect to the 2nd and 3rd order reaction plane, provides new insight into collective behaviour of the source. In&nbsp; elementary pp collisions, a sphericity-differential analysis allows to differentiate between jetty and spherical events, shedding new light on the dependence of the apparent radii on pair transverse momentum kT. In addition, femtoscopic correlations with unlike particles, such as pion-kaon pairs, probe the emission time difference between particle species. Finally, the analysis of femtoscopic correlations is also being used to probe interactions at low relative momenta for a variety of particles and anti-particles that are not available as beams for scattering experiments.</p

New developments for ALICE MasterClasses and the new Particle Therapy MasterClass

Heavy-ion physics is present within the "International MasterClasses" for almost ten years. New developments aiming at expanding their scope and reach are presented in this talk. First, in line with the physics research of typical heavy-ion experiments, three measurements were developed based on actual data analysis in the ALICE experiment at CERN/LHC. They correspond to the most important observables studied to characterise the properties of matter produced in energetic collisions of ions or protons. Then, with the aim to highlight applications from fundamental research for society a new MasterClass was developed on Particle Therapy for cancer treatment highlighting the benefits of therapy with carbon ions. A good example is the fact that for this therapy the heavy-ion research centre GSI, Germany, played a pioneering role in Europe, in 90s, leading to the construction of the HIT therapy centre in Heidelberg. Both masterclasses had challenging requirements on software developments as they had to be realistic but also easy to use. In particular, recent developments resulted in a single modular framework integrating all three ALICE measurements supporting coherent further expansions. This framework can be built as a standalone application which can run on Linux by a simple double click, without the need of separate ROOT installation while necessary ROOT libraries are built in the executable using the AppImage format. The work of migrating the framework to a web environment has started and a proof of concept is presented. For the Particle Therapy Masterclass (PTMC) the software used, matRad based on Matlab, is a professional open source toolkit developed by the cancer therapy research centre DKFZ in Heidelberg for research and training. It allows optimising the dose to be delivered to the patient (treatment planning) using photons, protons or ions. For the masterclass, first a phantom is used to explain the concepts and it is followed by treatments of head and liver tumours. PTMC demonstrates applications of fundamental physics research for cancer treatment, namely, the use of accelerators, detectors, and understanding interactions of different particles with matter