The Time-Of-Flight (TOF) detector of the ALICE experiment at the CERN LHC is based on Multi-gap Resistive Plate Chambers (MRPCs) capable to achieve a time resolution better than 50
ps. The TOF ...detector consists of about 153
000 readout channels covering a total area of about
150
m
2
. In this paper the results of the commissioning of the full TOF are reported, including the first calibration results obtained with cosmic rays.
The Time-Of-Flight detector (TOF) of the ALICE experiment at the CERN LHC is based on Multi-gap Resistive Plate Chambers (MRPCs). The TOF detector consists of 152928 readout channels covering a total ...area of 141 m
2
. In this paper the results of the calibration with cosmic-ray data collected during 2009 are presented.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The W and Z boson production was measured via the muonic decay channel in proton-lead collisions at ... TeV at the Large ...Hadron Collider with the ALICE detector. The measurement covers backward (-4.46 < y sub(cms) < -2.96) and forward (2.03 < y sub(cms) < 3.53) rapidity regions, corresponding to Pb-going and p-going directions, respectively. The Z-boson production cross section, with dimuon invariant mass of 60 < m sub( ) mu mu < 120 GeV/c super(2) and muon transverse momentum (p sub(T) super( ) mu larger than 20 GeV/c, is measured. The production cross section and charge asymmetry of muons from W-boson decays with p sub(T) super( ) mu > 10 GeV/c are determined. The results are compared to theoretical calculations both with and without including the nuclear modification of the parton distribution functions. The W-boson production is also studied as a function of the collision centrality: the cross section of muons from W-boson decays is found to scale with the average number of binary nucleon-nucleon collisions within uncertainties. Figure not available: see fulltext.
Pre-installation tests and calibration of the ALICE TOF modules Akindinov, A.; Alici, A.; Antonioli, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2012, 2012-1-00, Letnik:
661
Journal Article
Recenzirano
Before installation into the ALICE experiment, all 87 modules of the TOF system had to undergo a series of tests. Initial check-ups included control of the gas tightness, readout connections quality, ...and high-voltage tests. Further tests were performed on a specially constructed Cosmic Ray Test Facility, where main characteristics of the modules were scanned under the working high voltage by means of cosmic muons. All TOF channels proved to provide the detection efficiency of more than 97% and time resolution of 80–110
ps, which complies with the ALICE requirements.
The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ...ranges |y|<0.9 and 2.5
Results of the beam tests of the prototype photon spectrometer PHOS for the ALICE experiment at the Large Hadron Collider (CERN) are presented. The spectrometer is based on detector elements composed ...of lead tungstate (PbWO
4
) crystals with dimensions of 22 × 22 × 180 mm and Hamamatsu S8664-55 (S8148) avalanche photodiodes. The beam tests have been performed on the secondary T10 beamline of the PS proton synchrotron. The main emphasis has been placed on the possibility of improving the PHOS timing resolution. Introduction of an additional timing channel with a silicon photomultiplier (SiPM) used as a photodetector is shown to improve the timing resolution for 1-GeV deposited energy from current value σ
t
= 3 to 0.3 ns. Silicon photomultipliers of the Hamamatsu MPPC S10362-33 family with an active area of 3 × 3 mm
2
are used in these measurements. Using fast photomultiplier tubes with an 8-mm-diameter photocathode, the timing resolution attainable in electromagnetic shower development in a lead tungstate crystal has been measured for a large-area photodetector. The timing resolution for a deposited energy of 1 GeV is 150 ps. The effect of the detector channel temperature on the timing resolution is investigated. Cooling the crystal results in an increase both in the scintillation intensity and in the decay time of the scintillator and fails to substantially improve the timing resolution.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The elliptic, triangular, quadrangular and pentagonal anisotropic flow coefficients for pi super( plus or minus ), K super( ...plus or minus ) and ... in Pb-Pb collisions at ... TeV were measured with the ALICE detector at the Large Hadron Collider. The results were obtained with the Scalar Product method, correlating the identified hadrons with reference particles from a different pseudorapidity region. Effects not related to the common event symmetry planes (non-flow) were estimated using correlations in pp collisions and were subtracted from the measurement. The obtained flow coefficients exhibit a clear mass ordering for transverse momentum (p sub(T)) values below approximately 3 GeV/c. In the intermediate p sub(T) region (3 < p sub(T) < 6 GeV/c), particles group at an approximate level according to the number of constituent quarks, suggesting that coalescence might be the relevant particle production mechanism in this region. The results for p sub(T) < 3 GeV/c are described fairly well by a hydrodynamical model (iEBE-VISHNU) that uses initial conditions generated by A Multi-Phase Transport model (AMPT) and describes the expansion of the fireball using a value of 0.08 for the ratio of shear viscosity to entropy density ( eta /s), coupled to a hadronic cascade model (UrQMD). Finally, expectations from AMPT alone fail to quantitatively describe the measurements for all harmonics throughout the measured transverse momentum region. However, the comparison to the AMPT model highlights the importance of the late hadronic rescattering stage to the development of the observed mass ordering at low values of p sub(T) and of coalescence as a particle production mechanism for the particle type grouping at intermediate values of p sub(T) for all harmonics. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity (|y| < 0.7) is measured in Pb-Pb collisions ...at ... TeV with ALICE at the LHC. The particle azimuthal distribution with respect to the reaction plane can be parametrized with a Fourier expansion, where the second coefficient (v sub(2)) represents the elliptic flow. The v sub(2) coefficient of inclusive electrons is measured in three centrality classes (0-10%, 10-20% and 20-40%) with the event plane and the scalar product methods in the transverse momentum (p sub(T)) intervals 0.5-13 GeV/c and 0.5-8 GeV/c, respectively. After subtracting the background, mainly from photon conversions and Dalitz decays of neutral mesons, a positive v sub(2) of electrons from heavy-flavour hadron decays is observed in all centrality classes, with a maximum significance of 5.9 sigma in the interval 2 < p sub(T) < 2.5 GeV/c in semi-central collisions (20-40%). The value of v sub(2) decreases towards more central collisions at low and intermediate p sub(T) (0.5 < p sub(T) < 3 GeV/c). The v sub(2) of electrons from heavy-flavour hadron decays at mid-rapidity is found to be similar to the one of muons from heavy-flavour hadron decays at forward rapidity (2.5 < y < 4). The results are described within uncertainties by model calculations including substantial elastic interactions of heavy quarks with an expanding strongly-interacting medium. Figure not available: see fulltext.
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