109085314
The silicon pixel detector (SPD) for the ALICE experiment
The ALICE silicon pixel detector (SPD) constitutes the two innermost layers of the inner tracking system (ITS). The basic building block of the SPD is the half-stave carrying two detector ladders. The half-stave is equipped with a multi-chip module (MCM) and an optical fibre link for control and readout. A 5-layer aluminium/polyimide bus ensures the distribution of power and signals on each half-stave. The half-staves are mounted on a light-weight carbon-fibre structure with an integrated evaporative cooling system. An overview of the SPD development and the current status of the construction are presented.
109039717
Test beam performance of the ALICE silicon pixel detector
Abstract The ALICE Silicon Pixel Detector (SPD) will include 1200 bump-bonded readout chips produced in a commercial 0.25 μ CMOS process. Each chip has 8192 pixels of size 50 × 425 μ m 2 , which leads to about 10 million readout channels in the whole detector system. Test beam measurements were recently carried out at the CERN SPS using a positive proton/pion beam as well as a 158 A GeV/c heavy ion beam (In) with a fixed Pb target. Analysis show good performance of the ALICE chip and assemblies in the positive beam as well as in the high multiplicity In beam. Preliminary results from data analysis show good performance of the SPD and fulfill the ALICE requirements.
6726038
The ALICE Pixel Detector Readout Chip Test System
The ALICE experiment will require some 1200 Readout Chips for the construction of the Silicon Pixel Detector [1] and it has been estimated that approximately 3000 units will require testing. This paper describes the system that was developed for this task.
122908768
The Alice silicon pixel detector
CERN European Organization for Nuclear Research, CH-1211 Geneva 23, Switzerland Universita degli Studi di Padova, I-35131, Padova, Italy Dipartimento IA di Fisica e Sez. INFN di Bari, I-70126,Bari,Italy Comenius University, SK-84215 Bratislava, Slovakia NIKHEF, National Institute for Nuclear Physics and High Energy Physics, 1098 SJ Amsterdam, The Netherlands Slovak Academy of Sciences, SK-04353, Kosice, Slovakia Universita di Roma I, La Sapienza, I-00185, Roma, Italy
111275354
Assembly procedure of the module (half-stave) of the ALICE Silicon Pixel Detector
The Silicon Pixel Detector (SPD) forms the two innermost layers of the ALICE Inner Tracking System (ITS). The detector includes 1200 readout ASICs, each containing 8192 pixel cells, bump-bonded to Si sensor elements. The thickness of the readout chip and the sensor element is 150 μm and 200 μm, respectively. Low-mass solutions are implemented for the bus and the mechanical support. In this contribution, we describe the basic module (half-stave) of the two SPD layers and we give an overview of its assembly procedure.
141117760
Assembly procedure of the ALICE silicon pixel detector module
14680346
Bound states and glueballs in three-dimensional Ising systems
We study the spectrum of massive excitations in three-dimensional models belonging to the Ising universality class. By solving the Bethe–Salpeter equation for 3D φ4 theory in the broken symmetry phase we show that recently found non-perturbative states can be interpreted as bound states of the fundamental excitation. We show that duality predicts an exact correspondence between the spectra of the Ising model in the broken symmetry phase and of the gauge theory in the confining phase. The interpretation of the glueball states of the gauge theory as bound states of the dual spin system allows us to explain the qualitative features of the glueball spectrum, in particular, its peculiar angular momentum dependence.
119225332
A new approach to the study of effective string corrections in LGTs
We propose a new approach to the study of the interquark potential in Lattice Gauge Theories. Instead of looking at the expectation value of Polyakov loop correlators we study the modifications induced in the chromoelectric flux by the presence of the Polyakov loops. In abelian LGTs, thanks to duality, this study can be performed in a very efficient way, allowing to reach high precision at a reasonable CPU cost. The major advantage of this strategy is that it allows us to eliminate the dominant effective string correction to the interquark potential (the Lüscher term) thus giving an unique opportunity to test higher order corrections. Performing a set of simulations in the 3d spin Ising model and then translating the result in the 3d gauge Ising model using duality, we were thus able to precisely identify and measure both the quartic and the sextic effective string corrections to the interquark potential. While the quartic term perfectly agrees with the Nambu–Goto one the sextic term is definitely different. Our result seems to disagree with the recent proof of the universality of the sextic correction. We discuss a few possible explanations of this disagreement.
119496069
String effects in Polyakov loop correlators
Abstract We compare the predictions of the effective string description of confinement in finite temperature gauge theories to high precision Monte Carlo data for the three-dimensional Z 2 gauge theory. We show that string interaction effects become more relevant as the temperature is increased towards the deconfinement one, and are well modeled by a Nambu-Goto string action.
121373220
The phase structure of the SU(2) × SU(2) spin system in two dimensions
Abstract Strong coupling expansions up to g −16 of the correlation length for a mixed SU(2) × SU(2), SO(3) × SO(3) system in a rectangular lattice are considered. In addition to the asymptotic freedom fixed point, an unexpected line of second-order transitions is discovered. The common critical exponent of these transitions is ν = 1, like in the Ising model.
15775859
Recent progress in the effective string theory description of LGTs
In presence of a static pair of sources, the spectrum of low-lying states of any confining gauge theory in D space-time dimensions is described, at large source separations, by an effective string theory. Recently two important advances improved our understanding of this effective theory. First, it was realized that the form of the effective action is strongly constrained by the requirement of the Lorentz invariance of the gauge theory, which is spontaneously broken by the formation of a long confining flux tube in the vacuum. This constraint is strong enough to fix uniquely the first few subleading terms of the action. Second, it has been realized that the first of these allowed terms - a quartic polynomial in the field derivatives - is exactly the composite field $T\bar{T}$, built with the chiral components, $T$ and $\bar{T}$, of the energy-momentum tensor of the 2d QFT describing the infrared limit of the effective string. This irrelevant perturbation is quantum integrable and yields, through the thermodynamic Bethe Ansatz (TBA), the energy levels of the string which exactly coincide with the Nambu-Goto spectrum. In this talk we first review the general implications of these two results and then, as a test of the power of these methods, use them to construct the first few boundary corrections to the effective string action.