The ALICE experiment at CERN will undergo a major upgrade in the second Long LHC Shutdown in the years 2018–2019; this upgrade includes the full replacement of the Inner Tracking System (ITS), ...deploying seven layers of Monolithic Active Pixel Sensors (MAPS). For the development of the new ALICE ITS, the Tower-Jazz 0.18μm CMOS imaging sensor process has been chosen as it is possible to use full CMOS in the pixel and different silicon wafers (including high resistivity epitaxial layers). A large test campaign has been carried out on several small prototype chips, designed to optimize the pixel sensor layout and the front-end electronics. Results match the target requirements both in terms of performance and of radiation hardness. Following this development, the first full scale chips have been designed, submitted and are currently under test, with promising results. A telescope composed of 4 planes of Mimosa-28 and 2 planes of Mimosa-18 chips is under development at the DAFNE Beam Test Facility (BTF) at the INFN Laboratori Nazionali di Frascati (LNF) in Italy with the final goal to perform a comparative test of the full scale prototypes. The telescope has been recently used to test a Mimosa-22THRb chip (a monolithic pixel sensor built in the 0.18μm Tower-Jazz process) and we foresee to perform tests on the full scale chips for the ALICE ITS upgrade at the beginning of 2015. In this contribution we will describe some first measurements of spatial resolution, fake hit rate and detection efficiency of the Mimosa-22THRb chip obtained at the BTF facility in June 2014 with an electron beam of 500MeV.
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Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the ...possibility to link them directly to the advancement in lattice Quantum Chromo-Dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop
Tomography of the Quark-Gluon Plasma with Heavy Quarks
, which was held in October 2016 in Leiden, The Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma.
The features of the 180nm TowerJazz 1 CMOS technology allow for the first time the use of CMOS Monolithic Active Pixel Sensors (MAPS) under the harsh operational conditions of the LHC experiments. ...The stringent requirements of the ALICE Inner Tracking System (ITS) in terms of material budget, radiation hardness, readout speed and a low power consumption have thus lead to the choice of MAPS as baseline technology option for the recently approved upgrade of the ITS and are the key drivers for R&D efforts on basic transistor and Explorer and MIMOSA pixel sensor prototypes produced in TowerJazz technology. Though the radiation loads expected for the ITS are below those of ATLAS and CMS, it is however necessary to assess the radiation hardness for ITS MAPS prototypes. Total Ionizing Dose (TID) radiation hardness has been established for basic transistor structures using a 60keV X-ray machine. The main operational characteristics and detection properties such as noise, charge collection efficiency and signal over noise ratio of Explorer-0 and MIMOSA32 and MIMOSA34 pixel sensor prototypes have been studied using X-rays ( 55 Fe) and test beams at CERN and DESY before and after Non Ionizing Energy Loss (NIEL) and TID irradiation. In this paper the results of these R&D activities will be presented and discussed.
A measurement of beauty hadron production at mid-rapidity in proton-lead collisions at a nucleon–nucleon centre-of-mass energy sNN=5.02 TeV is presented. The semi-inclusive decay channel of beauty ...hadrons into J/ψ is considered, where the J/ψ mesons are reconstructed in the dielectron decay channel at mid-rapidity down to transverse momenta of 1.3 GeV/c. The bb¯ production cross section at mid-rapidity, dσbb¯/dy, and the total cross section extrapolated over full phase space, σbb¯, are obtained. This measurement is combined with results on inclusive J/ψ production to determine the prompt J/ψ cross sections. The results in p–Pb collisions are then scaled to expectations from pp collisions at the same centre-of-mass energy to derive the nuclear modification factor RpPb, and compared to models to study possible nuclear modifications of the production induced by cold nuclear matter effects. RpPb is found to be smaller than unity at low pT for both J/ψ coming from beauty hadron decays and prompt J/ψ.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification ...and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/ in p–Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
Two-particle angular correlations were measured in pp collisions at Formula omitted TeV for pions, kaons, protons, and lambdas, for all particle/anti-particle combinations in the pair. Data for ...mesons exhibit an expected peak dominated by effects associated with mini-jets and are well reproduced by general purpose Monte Carlo generators. However, for baryon-baryon and anti-baryon-anti-baryon pairs, where both particles have the same baryon number, a near-side anti-correlation structure is observed instead of a peak. This effect is interpreted in the context of baryon production mechanisms in the fragmentation process. It currently presents a challenge to Monte Carlo models and its origin remains an open question.
The transverse momentum distributions of the strange and double-strange hyperon resonances (Σ(1385)±, Ξ(1530)0) produced in p–Pb collisions at sNN=5.02 TeV were measured in the rapidity range ...-0.5<yCMS<0 for event classes corresponding to different charged-particle multiplicity densities, ⟨dNch/dηlab⟩. The mean transverse momentum values are presented as a function of ⟨dNch/dηlab⟩, as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of ⟨dNch/dηlab⟩. The equivalent ratios to pions exhibit an increase with ⟨dNch/dηlab⟩, depending on their strangeness content.
The azimuthal correlations of D mesons with charged particles were measured with the ALICE apparatus in pp collisions at s=7TeV and p–Pb collisions at sNN=5.02TeV at the Large Hadron Collider. D0, ...D+, and D∗+ mesons and their charge conjugates with transverse momentum 3<pT<16GeV/c and rapidity in the nucleon-nucleon centre-of-mass system |ycms|<0.5 (pp collisions) and -0.96<ycms<0.04 (p–Pb collisions) were correlated to charged particles with pT>0.3GeV/c. The yield of charged particles in the correlation peak induced by the jet containing the D meson and the peak width are compatible within uncertainties in the two collision systems. The data are described within uncertainties by Monte-Carlo simulations based on PYTHIA, POWHEG, and EPOS 3 event generators.
The transverse momentum distributions of the strange and double-strange hyperon resonances (
,
) produced in p-Pb collisions at
TeV were measured in the rapidity range
for event classes corresponding ...to different charged-particle multiplicity densities,
d
/d
. The mean transverse momentum values are presented as a function of
d
/d
, as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of
d
/d
. The equivalent ratios to pions exhibit an increase with
d
/d
, depending on their strangeness content.
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