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.
121671017
Recent test results of the ALICE silicon pixel detector
The ALICE SPD (Silicon Pixel Detector) forms the two innermost layers of the Inner Tracking System (ITS) of the ALICE experiment at LHC. After several years of development the production of the modules is starting. The present article provides an overview of the different elements that will be used in the SPD with special emphasis given to testing of wafers and bump-bonded ladders.
16157843
The Spatial string tension in high temperature lattice gauge theories
Abstract We develop some techniques hich allow an analytic evaluation of space-like observables in high-temperature lattice gauge theories. We show that such variables are described extremely well by dimensional reduction. In particular, by using results obtained in the context of “Induced QCD”, we evaluate the contributions to space-like observables coming from the Higgs sector of the dimensionally reduced action, we find that they are of higher order in the coupling constant compared to those coming from the space-like action and hence neglegible near the continuum limit. In the case of SU(2) gauge theory our results agree with those obtained through Monte Carlo simulations both in (2+1) and (3+1) dimensions and they also indicate a possible way of removing the gap between the two values of g 2 ( T ) recently appeared in the literature.
18539443
EFFECTIVE STRING PICTURE FOR CONFINING GAUGE THEORIES AT FINITE TEMPERATURE
We study the ``effective string picture'' of confinement, deriving theoretical predictions for the interquark potential at finite temperature. At low temperatures, the leading string correction to the linear confining potential between a heavy quark-antiquark pair is the "L\"uscher term''. Assuming a Nambu-Goto effective string action, subleading contributions can be worked out in an analytical way. We also discuss the contribution given by a possible ``boundary term'' in the effective action, and compare these predictions with high precision results from simulations of lattice Z(2) gauge theory in three dimensions, obtained with an algorithm that exploits the duality of the Z(2) gauge model with the Ising spin model.
17454680
Effective string picture for confinement at finite temperature: theoretical predictions and high precision numerical results
Abstract The effective string picture of confinement is used to derive theoretical predictions for the interquark potential at finite temperature. At short distances, the leading string correction to the linear confining potential between a heavy quark-antiquark pair is the “Luscher term”. We assume a Nambu-Goto effective string action, and work out subleading contributions in an analytical way. We discuss the contribution given by a possible “boundary term” in the effective action, comparing these predictions with results from simulations of lattice Z 2 gauge theory in three dimensions, obtained with an algorithm which exploits the duality of the Z 2 gauge model with the Ising spin model.
118101100
New results on the effective string corrections to the inter-quark potential
We propose a new approach to the study of the inter-quark 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 with a reasonable CPU cost. The major advantage of this numerical strategy is that it allows to eliminate the dominant effective string correction to the inter-quark potential (the Luscher term) thus giving an unique opportunity to test higher order corrections. Performing a set of simulations in the 3d gauge Ising model we were thus able to precisely identify and measure both the quartic and the sextic effective string corrections to the inter-quark 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 by Aharony and Karzbrun of the universality of the sextic correction. We discuss a few possible explanations of this disagreement. The numerical approach described above can also be applied to the study of Wilson loops. In this case, the numerical results are precise enough to test the two-loop prediction of the Nambu-Goto action. The two-loop NG result computed time ago by by Dietz and Filk is incompatible with the data; however, after correcting some mistakes in their expression, compatibility is restored. The viability of a first-order, operatorial description of the Wilson loop is also pointed out.