Assembly and validation of the ALICE silicon microstrip detector Bregant, M.; Borysov, O.; Bosisio, L. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
2007, Volume:
570, Issue:
2
Journal Article, Conference Proceeding
Peer reviewed
The two outermost layers of the ALICE Inner Tracking System consist of 1698 double-sided silicon microstrip modules, which form the Silicon Strip Detector (SSD). The SSD modules offer several ...novelties, which include the use of TAB-bonding technique for the connection of the front-end electronic via thin aluminium-polyimide cables. The module as well as its parts will be described and the assembling procedure illustrated.
Delivery of more than 2000 AC-coupled double-sided silicon microstrip sensors, designed to equip the two outermost layers of the ALICE Inner Tracking System, has been recently completed by three ...manufactures. This represents the largest production of this type of sensors undertaken so far. Sensor testing and quality control has been performed at INFN Trieste. A careful optimization of the testing procedures has allowed performing a thorough qualification of the large number of sensors without making use of automated device-handling equipment. The paper presents an overview of the test procedures and results.
An experimental indication of negative heat capacity in excited nuclear systems is inferred from the event by event study of energy fluctuations in Au quasi-projectile sources formed in Au+Au ...collisions at 35 A.MeV. Equilibrated events are selected and the excited source configuration is reconstructed through a calorimetric analysis of its de-excitation products. Fragment partitions show signs of a critical behavior at about 4.5 A.MeV excitation energy. Around this value the heat capacity shows a negative branch providing a direct evidence of a first order liquid gas phase transition.
The ALICE vertex detector: Focus on the micro-strip layers Bregant, M.; Borysov, O.; Bosisio, L. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
12/2006, Volume:
569, Issue:
1
Journal Article, Conference Proceeding
Peer reviewed
The ALICE experiment, which is being installed at the Large Hadron Collider at CERN, is designed to operate in a high-track density environment which is typical of relativistic heavy ions physics. ...This paper reports the main characteristics of the Inner Tracking System (ITS) of ALICE and describes the Silicon Strip Detector, which forms the two outermost layers of the ITS.
The first evidence of spin alignment of vector mesons ( K*0 and ϕ ) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element ρ 00 is measured at ...midrapidity ( | y | < 0.5 ) in Pb-Pb collisions at a center-of-mass energy ( √sNN ) of 2.76 TeV with the ALICE detector. ρ 00 values are found to be less than 1/3 (1/3 implies no spin alignment) at low transverse momentum ( p T < 2 GeV / c ) for K*0 and ϕ at a level of 3 σ and 2 σ , respectively. No significant spin alignment is observed for the K0S meson ( spin = 0 ) in Pb-Pb collisions and for the vector mesons in p p collisions. The measured spin alignment is unexpectedly large but qualitatively consistent with the expectation from models which attribute it to a polarization of quarks in the presence of angular momentum in heavy-ion collisions and a subsequent hadronization by the process of recombination.
Midrapidity production of π±, K±, and (¯p)p measured by the ALICE experiment at the CERN Large Hadron Collider, in Pb-Pb and inelastic pp collisions at √sNN=5.02 TeV, is presented. The invariant ...yields are measured over a wide transverse momentum (pT) range from hundreds of MeV/c up to 20 GeV/c. The results in Pb-Pb collisions are presented as a function of the collision centrality, in the range 0–90%. The comparison of the pT-integrated particle ratios, i.e., proton-to-pion (p/π) and kaon-to-pion (K/π) ratios, with similar measurements in Pb-Pb collisions at √sNN=2.76 TeV show no significant energy dependence. Blast-wave fits of the pT spectra indicate that in the most central collisions radial flow is slightly larger at 5.02 TeV with respect to 2.76 TeV. Particle ratios (p/π, K/π) as a function of pT show pronounced maxima at pT≈3GeV/c in central Pb-Pb collisions. At high pT, particle ratios at 5.02 TeV are similar to those measured in pp collisions at the same energy and in Pb-Pb collisions at √sNN=2.76 TeV. Using the pp reference spectra measured at the same collision energy of 5.02 TeV, the nuclear modification factors for the different particle species are derived. Within uncertainties, the nuclear modification factor is particle species independent for high pT and compatible with measurements at √sNN=2.76 TeV. The results are compared to state-of-the-art model calculations, which are found to describe the observed trends satisfactorily.
Assembly and validation of the SSD silicon microstrip detector of ALICE Bregant, M.; Borysov, O.; Bosisio, L. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
10/2006, Volume:
566, Issue:
1
Journal Article, Conference Proceeding
Peer reviewed
Open access
The Silicon Strip Detector (SSD) forms the two outermost layers of the Inner Tracking System (ITS) of ALICE. The SSD detector consists of 1698 double-sided silicon microstrip modules. The electrical ...connection between silicon sensor and front-end electronics is made via TAB-bonded aluminium–polyimide cables (chip-cables). The module assembly is challenging because of the module geometry and the use of chip-cables. This article describes the assembly procedure and the test protocol used.
The pseudorapidity density of charged particles, dNch / d η , at midrapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of √ s N N = 5.02 TeV . For the 5% ...most central collisions, we measure a value of 1943 ± 54 . The rise in dNch / d η as a function of √ s N N is steeper than that observed in proton-proton collisions and follows the trend established by measurements at lower energy. The increase of dNch / d η as a function of the average number of participant nucleons, ⟨ N part ⟩ , calculated in a Glauber model, is compared with the previous measurement at √ s N N = 2.76 TeV . A constant factor of about 1.2 describes the increase in dNch / d η from √ s N N = 2.76 to 5.02 TeV for all centrality classes, within the measured range of 0%–80% centrality. The results are also compared to models based on different mechanisms for particle production in nuclear collisions.
Comprehensive results on the production of unidentified charged particles, π±, K±, K$_S^0$, K*(892)0, $p, \bar{p}, ϕ$(1020), Λ, Λ, Ξ-, Ξ+, Ω-, and $\bar{Ω}^+$ hadrons in proton-proton ...(pp) collisions at $ \sqrt{s}$=7 TeV at midrapidity (|y|<0.5) as a function of charged-particle multiplicity density are presented. In order to avoid autocorrelation biases, the actual transverse momentum (pT) spectra of the particles under study and the event activity are measured in different rapidity windows. In the highest multiplicity class, the charged-particle density reaches about 3.5 times the value measured in inelastic collisions. While the yield of protons normalized to pions remains approximately constant as a function of multiplicity, the corresponding ratios of strange hadrons to pions show a significant enhancement that increases with increasing strangeness content. Furthermore, all identified particle-to-pion ratios are shown to depend solely on charged-particle multiplicity density, regardless of system type and collision energy. The evolution of the spectral shapes with multiplicity and hadron mass shows patterns that are similar to those observed in p-Pb and Pb-Pb collisions at Large Hadron Collider energies. The obtained pT distributions and yields are compared to expectations from QCD-based pp event generators as well as to predictions from thermal and hydrodynamic models. These comparisons indicate that traces of a collective, equilibrated system are already present in high-multiplicity pp collisions.
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