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

Performance of the ALICE experiment at the CERN LHC

ALICE is the heavy-ion experiment at the CERN Large Hadron Collider. The experiment continuously took data during the first physics campaign of the machine from fall 2009 until early 2013, using proton and lead-ion beams. In this paper we describe the running environment and the data handling procedures, and discuss the performance of the ALICE detectors and analysis methods for various physics observables

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

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

Multiplicity dependence of jet-like two-particle correlation structures in p-Pb collisions at 1asNN=5.02 TeV

Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in p\u2013Pb collisions at a nucleon\u2013nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum range 0.7 < pT,assoc < pT,trig < 5.0 GeV/c is examined, to include correlations induced by jets originating from low momentum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range |\u3b7| < 0.9. The near-side long-range pseudorapidity correlations observed in high-multiplicity p\u2013Pb collisions are subtracted from both near-side short-range and away-side correlations in order to remove the non-jet-like components. The yields in the jet-like peaks are found to be invariant with event multiplicity with the exception of events with low multiplicity. This invariance is consistent with the particles being produced via the incoherent fragmentation of multiple parton\u2013parton scatterings, while the yield related to the previously observed ridge structures is not jet-related. The number of uncorrelated sources of particle production is found to increase linearly with multiplicity, suggesting no saturation of the number of multi-parton interactions even in the highest multiplicity p\u2013Pb collisions. Further, the number scales only in the intermediate multiplicity region with the number of binary nucleon\u2013nucleon collisions estimated with a Glauber Monte-Carlo simulation

Development of Integreted Electronics for Monolithic pixel detectors for the ALICE-ITS upgrade

This thesis is part of the ongoing studies for the upgrade of the Inner Tracking System (ITS) which is the innermost detector of ALICE (A Large Ion Collider Experiment) at CERN LHC. ALICE is a dedicated heavy-ion detector aiming to study and the characterize the Quark-Gluon Plasma (QGP). It will be undergone to an upgrade program to enable it to reach its physics objectives concerning the dynamics of the QGP after the Long Shutdown 2, foreseen 2018-2019. Indeed, an increase of the LHC instantaneous luminosity up to L = 6×1027cm−2s−1 for the Pb-Pb collisions will bring ALICE to accumulate 10 nb−1 for Pb-Pb collisions and to deal with an interaction rate of 50 kHz. In this way, a gain of 100 in statics will be possible in order to have access to rare probes at low and intermediate range of pT . The crucial limitations of current ALICE detector concern the overall material budget and a limited read-out rate capability. In particular, to overcome those limitations the ITS will be replaced with a new one with an higer spatial resolution together with an enhanced read-out rate capability. Actually, the ITS is the nearest detector to the interaction points and it deals with a large track densities, thus is essential to have a good impact parameter resolution. The new ITS will be made up of seven layers of Monolithic Active Pixel Sensors (MAPS). Indeed, the monolithic technology allows to reduce the overall material budget since one of the key feature of MAPS is the inte- gratation in the same silicon die of the sensor and the read-out electronics. The baseline for the pixel chip devolped for upgraded ITS is the ALPIDE pixel chip. It is implemented with the TowerJazz 0.18 um CMOS Imaging Sensor process since it offers a non standard MAPS with the quadruple well option which is essential to implement a full CMOS in-pixel circuitry an have a good resistance at the radiation damages of the ALICE environment. The sensor chip will measure 3 cm by 1.5 cm and contain about 500 000 pixels of about 28 by 28 microns. It consists of a pixel matrix and a chip periphery. The development of some key circuits located in the chip periphery will be treated in detail in this thesis. The chip periphery hosts those circuits which are necessary to link the ITS with an external Read-out Unit (RU) placed on a patch panel. These circuits are a Multipoint Low Voltage Differential Signaling (M-LVDS) transceiver and a pseudo-LVDS driver with pre-emphasis. They are respectively a slow speed and a high speed transmission circuit based on the LVDS standard transmission protocol. This standard allows for multipoint or point-to-point communications by ensuring a reduced power consumption and a good signal quality even at high data rate. The M-LVDS transceiver allows a bidirectional communication between the chips and/or the patch panel. It consists of a pseudo-LVDS driver and a LVDS receiver and it is in charge to broadcast the slow signals as the LHC 40 MHz clock, triggers and configuration settings. Thes driver is a three state buffer which allows a half-duplex bus topology in which only one driver at a time can transmit while every receiver in the line is receiving. Even if the driver works at 40 MHz (80 Mb/s), it has to drive a 6.5 m differential line at which multiple transceivers are connected. For this reason the driver strength of the MLVDS driver has to be high enough to overcome the bandwidth limitations due to the presence of the transmission line and the loads. The pseudo-LVDS driver is the high speed output circuit which sends out data from the chip periphery. The target speeds which will not limit the read-out of the full pixel chip are 1.2 Gb/s for the IB and 400 Mb/s for the OB. Therefore, these are the speed rates at which the driver has to transmit. Furthermore, it has to drive a full 5m/6.5m transmission line linking the detector with the patch panel. For this reason this high speed output is made up of a main driver and an ancillary pre-emphasis driver. Indeed, in the case in which data have to be broadcast at high speed and for long distances the pre-emphasis technique becomes essential to have a good transmission quality at the end of the lines. The last circuit that will be analized is a monitoring Analog to Digital Converter (ADC). This device controls some voltage levels inside the chip itself to guarantee the correct chip operation. The resolution foreseen for this device is 11-bit and the architecture takes advantage of the 2 conversion steps principle. All the circuits listed before are designed in the same 0.18 μm CMOS technology and operate from the same 1.8 V supply. All of them, with the exception of the ADC, will be integrated on the pixel chip prototypes. This thesis illustrates the design of the data transmission circuits and the development and characterization from simmulations and test results. Furthermore, the prelimary studies on this novel architecture are shown to demonstrate that the operating principle works