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

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

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

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

Mitigation Methods Increasing Radiation Hardness of the FPGA-Based Readout of the ALICE Inner Tracking System

Over the years 2019-2020, the ALICE experimental apparatus will undergo a major upgrade. A key element of the modernization is the construction of a new Inner Tracking System (ITS) consisting of 24,120 monolithic active pixel sensors (MAPSs). The sensors' constrained power budgets limit their data line driving capability, forcing the readout electronics to be located as close as possible to the detector in a hostile radiation environment. The readout system serves many various functions. It configures, monitors and reads out data from the detector and interfaces with the trigger and power systems. It also preprocesses and packetizes the received data, and streams the packets out to the data acquisition system. Because of the tasks that it performs, it requires powerful and flexible processing units. Also, as new functionalities are usually implemented over time, it is required that the readout system can be upgraded. Modern FPGA devices meet all of the aforementioned requirements. Unfortunately, dedicated radiation-hard by design FPGAs cannot be utilized, as they are either limited in resources or too expensive. Conversely, commercial-grade SRAM-based FPGAs offer a large amount of logic resources and transceivers, and their price is low enough to be used in large quantities. Although they are susceptible to ionizing and non-ionizing radiation, there exist radiation mitigation methods that can be employed to increase the radiation hardness. Mitigation methods that increase the radiation hardness of non-radiation-hardened SRAM-based FPGAs are the subject of this dissertation. The author verifies the hypothesis that it is possible to design and deploy the readout system employing commercial, non-radiation-hardened SRAM-based FPGAs for the upgraded ALICE Inner Tracking System. The design functional error rate estimation methodology is proposed, which is followed by the explanation of concepts of various radiation mitigation methods based on: spatial redundancy, refreshing of configuration memory of SRAM-based FPGAs, and triplication of inputs and outputs. Basic building blocks of an SRAM-based FPGA design (combinational and sequential circuits, Block RAM, Finite State Machines) were implemented with various mitigation methods employed, and experimentally evaluated via fault injection and irradiation tests. Finally, implementation guidelines based on the obtained experimental results were formulated for the application in the FPGA-based Readout of the upgraded ALICE Inner Tracking System. In the dissertation the author also includes the description of the prototype readout electronics that were utilized as the main platform for radiation testing and various development activities while designing the ITS Readout System

Design of Finite State Machines for SRAM-based FPGAs operated in radiation field

For the CERN LHC Run 3, the ALICE experiment completely redesigned the Inner Tracking System (ITS), which now consists of seven cylindrical layers instrumented with 24 120 Monolithic Active Pixel Sensors, covering an area of 10m$^2$ . The ITS is controlled and read out by 192 custom Readout Units, which employ commercial SRAM-based FPGAs and will operate in a radiation field, requiring specific FPGA design to ensure system reliability. This contribution focuses on the techniques developed for designing radiation tolerant finite state machines, discussing the theoretical background, the actual implementation, and their validation with fault injections and proton irradiation tests

Electrical and functional characterisation with single chips and module prototypes of the 1.2 Gb/s serial data link of the monolithic active pixel sensor for the upgrade of the ALICE Inner Tracking System

The upgrade of the ALICE Inner Tracking System uses a newly developed monolithic active pixel sensor (ALPIDE) which will populate seven tracking layers surrounding the interaction point. Chips communicate with the readout electronics using a 1.2 Gb/s data link and a 40 Mb/s bidirectional control link. Event data are transmitted to the readout electronics over microstrips on a Flexible Printed Circuit and a 6 m long twinaxial cable. This paper outlines the characterisation effort for assessing the Data Transmission Unit performance of single sensors and prototypes of the detector modules. It describes the different prototypes used, the test system and procedures, and results of laboratory and irradiation tests