53308940
The ALICE silicon pixel detector readout electronics
Abstract The ALICE silicon pixel detector (SPD) constitutes the two innermost layers of the ALICE inner tracking system (ALICE Collaboration, 1999) [1] . The SPD is built with 120 detector modules (half-staves) and contains about 10 million pixels in total. The half-staves are connected to the off-detector electronics, housed in a control room 100 m away, via bidirectional optical links. The stream of data from the front-end electronics is processed in 20 VME readout modules, called routers, based on FPGAs. Three 2-channel link-receiver daughter cards, also based on FPGAs, are plugged in each router. Each link-receiver card receives data via the optical link from two half-staves, applies the zero suppression and passes them to the router to be processed and sent to the ALICE–DAQ system through the detector data link (DDL). The SPD control, configuration and data monitoring are performed using the VME interface embedded in the router.
110392152
LEPIX: MONOLITHIC DETECTORS FOR PARTICLE TRACKING IN STANDARD VERY DEEP SUBMICRON CMOS TECHNOLOGIES
A few silicon foundries offer the possibility of porting standard deep-submicron CMOS processes on wafers with resistivity well above 100 Ω·cm. In this paper we propose to use this option to implement monolithic sensors for particle tracking that combine the low power consumption and material budget offered by monolithic active pixel sensors (MAPS) with the speed and radiation hardness characterizing hybrid pixel detectors. Our simulations suggest that a uniform depletion layer with a thickness of at least 40 μm should be obtained by applying a reverse bias voltage of 100 V. The charge collection is fully dominated by drift, which is a key factor to guarantee adequate resistance against radiation-induced bulk damage. The paper describes the sensor concept and the key issues involved in the design of the associated read-out electronics.
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.
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.
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.
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
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.
120339978
MODULAR INVARIANCE AND FUSION RULE ALGEBRAS: CLASSIFICATION OF THE THREE-OPERATOR CASE
We show how to handle together constraints coming from associativity, modular invariance and analyticity in RCFT's. In particular, looking at the theories with three operators we classify fusion rule algebras, central charges and conformal weights fulfilling such constraints. We also show that all allowed theories with three operators are algebraic.
14414063
Non-analyticity of the Callan-Symanzik β-function of two-dimensional O(N) models
We discuss the analytic properties of the Callan-Symanzik β-function β(g) associated with the zero-momentum four-point coupling g in the two-dimensional 4 model with O(N) symmetry. Using renormalization-group arguments, we derive the asymptotic behaviour of β(g) at the fixed point g*. We argue that β'(g) = β'(g*) + O(|g-g*|1/7) for N = 1 and β'(g) = β'(g*) + O(1/log |g-g*|) for N≥3. Our claim is supported by an explicit calculation in the Ising lattice model and by a 1/N calculation for the two-dimensional 4 theory. We discuss how these non-analytic corrections may give rise to a slow convergence of the perturbative expansion in powers of g.
18604142
A new class of solutions of the DMPK equation.
We introduce and discuss a new class of solutions of the DMPK equation in which some of the eigenvalues are grouped into clusters which are conserved in the asymptotic large distance limit (i.e. as the length of the wire increases). We give an explicit expression for the asymptotic expansion of these solutions and suggest some possible applications. In particular these new solution could be useful to avoid the quasi one dimensional constraint in the DMPK equation and to study the crossover between the metallic and insulating phases.