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

Characterization of ALPIDE silicon sensors with inclined tracks

The upgrade of the ALICE Inner Tracking System (ITS) aims at improving the capabilities of ALICE in terms of read-out rate as well as track pointing resolution and track finding efficiency, especially for particleswith low transverse momenta. The new ITS will be a low material budget detector with high granularity and read-out speed. It comprises seven concentric layers of Monolithic Active Pixel Sensors (MAPS) with a total active surface of about 10 m$^2$. The developed MAPS are based on the TowerJazz 180 nm CMOS technology. The sensor is called ALPIDE. In this paper, we present the setup used for measurements with inclined tracks and we discuss the sensor efficiency obtained using $\pi$ beams with a momentum of 6 GeV/c at the Proton Synchrotron (PS) at CERN. Some sensors were irradiated before the beamtest using the cyclotron facility of the Nuclear Physics Institute of the Czech Academy of Sciences (NPI CAS) to induce radiation damage to the sensor. Measurements at different operating points (thresholds, bias voltages) provide important information about cluster-shape frequencies, needed to tune the ALICE Monte-Carlo generators. A very good agreement between test-beam data and simulations is obtained

Performance of the Charge Injectors of the ALICE Silicon Drift Detectors

The Inner Tracking System (ITS) of the ALICE experiment at the LHC uses high precision Silicon Drift Detectors (SDD) in two out of the six cylindrical layers. In these detectors, the drift speed is significantly influenced by temperature variations. The drift velocity is determined by measuring the drift time of electrons injected at fixed known locations in the sensor volume by means of dedicated MOS devices (injectors). We report the results of a study aimed at characterizing the time needed to stabilize the detector temperature and to have the injectors working with full effciency. The study was carried out in 2010 and is based on the analysis of a series of dedicated calibration runs, which were taken every few minutes for a period of two days after powering on the detector

Upgrade of the ALICE Inner Tracking System

ALICE detector was constructed to study the properties of hot and dense hadronic matter formed in relativistic nuclear collisions. During the second long LHC shutdown in 2019-2020, the collaboration plans to upgrade the current vertex detector, the Inner Tracking System (ITS), in order to increase the reconstruction accuracy of secondary vertices and to lower the threshold of particle transverse momentum measurement. The upgrade strategy of ITS is based on the application of new Monolithic Active Pixel Sensors (MAPS) designed in 0.18 μm CMOS technology. The 50 μm thick chip consists of a single silicon die incorporating a 0.18 μm high-resistivity silicon epitaxial layer (sensor active volume) and matrix of charge collection diodes (pixels) with readout electronics. Radiation hardness of the upgraded ITS is one of the crucial moments in the overall performance of the system. A wide set of MAPS structures with different read-out circuits was produced and is being studied by the ALICE collaboration to optimize the pixel sensor functionality. An overview of the ALICE ITS upgrade and the expected performance improvement will be presented together with selected results from a campaign that includes several irradiation and beam tests

Commissioning of the upgraded ALICE Inner Tracking System

The ALICE Inner Tracking System (ITS) detector is undergoing a major upgrade in order to cope with the increased data rates and to meet the requirements as set out by the physics goals of the experiment after the LHC Long Shutdown 2 (LS2). The new ITS will be completely made up of monolithic active pixel sensors (MAPS), called ALPIDE, based on the CMOS 180 nm process. A single sensor measures 30 mm × 15 mm and contains half a million pixels, with a pitch of 27 μm×29 μ m, distributed over 512 rows and 1024 columns. The ALPIDE sensors, thinned to 50 μ m and 100 μ m for the Inner and Outer Barrels, respectively, are mounted on ultra-lightweight carbon composite support structures with an embedded cooling system. This results in a considerable reduction of the material budget and a significant improvement of the impact parameter resolution and tracking efficiency for low-transverse momentum particles. The construction of the ITS detector has been completed and the commissioning on surface is ongoing. The detector will be installed in ALICE in 2020. This paper will give a brief overview of the motivation for the upgrade and will present the first results of the detector performance obtained during the commissioning