19015103
Beam test results of the irradiated silicon drift detector for ALICE
The Inner Tracking System (ITS) of the ALICE experiment at LHC will use high precision Silicon Drift Detectors (SDD) in two of the six cylindrical layers. In this paper we report on the results of beam test of a SDD irradiated with 1 GeV electrons. The aim of this test was to verify the radiation tolerance of the device under an electron fluence equivalent to twice the particle fluence expected during 10 years of ALICE operation.
111282417
The front-end system of the silicon drift detectors of ALICE
The ALICE experiment at CERN will have an inner tracker made of six barrels of semiconductor detectors. The two intermediate layers of the system will employ Silicon Drift Detectors (SDD) technology. The front-end electronics of the SDDs, which required the development of two full-custom integrated circuits, is reviewed in this paper. The design of the front-end hybrid is discussed and results obtained with full-size prototypes are presented.
24465524
A 32-channel, 0.25 /spl mu/m CMOS ASIC for the readout of the silicon drift detectors of the ALICE experiment
In this paper we present a 32 channel ASIC prototype for the readout of the silicon drift detectors (SDDs) of the ALICE experiment. The ASIC integrates on the same substrate 32 transimpedance amplifiers, a 32 /spl times/ 256 cell analogue memory and 16 successive approximation 10 bit A/D converters. The circuit amplifies and samples at 40 MS/s the input signal in a continuous way. When an external trigger signal validates the acquisition, the sampling is stopped and the data are digitized at lower speed (0.5 MS/s). The chip has been designed and fabricated in a commercial 0.25 /spl mu/m CMOS technology. It has been extensively tested both on a bench and connected with a detector in several beam tests. In this paper both design issues and test results are presented. The radiation tolerance of the design has been increased by special layout techniques. Total dose irradiation tests are also presented.
38739765
The ALICE Silicon Drift Detector system
The project of the two Silicon Drift Detector (SDD) layers of the ALICE Inner Tracking System is reviewed, with details on the barrel construction and on the front-end electronics. The results on the SDD spatial resolution are reported as obtained in the 2000 beam test from a whole drift region of the detector.
13868349
Dilepton production as a measure of QGP thermalization time
We discuss dilepton production from a quark–gluon plasma which has a time-dependent anisotropy in momentum space. A phenomenological model for the hard momentum scale, phard(τ) and the plasma anisotropy parameter, ξ(τ), is presented. The model interpolates between early-time 1 + 1 free streaming behavior (τ τiso) and late-time ideal 1 + 1 hydrodynamical behavior (τ τiso). Using this model, we find that the dilepton rate arising from electromagnetic annihilations of quarks in the kinematic range 3 <pT< 8 GeV is sensitive to the assumed isotropization time of the system, τiso. Therefore high-energy dilepton production can be used to probe the degree of momentum-space isotropy of a quark–gluon plasma produced in relativistic heavy-ion collisions and the time of onset of hydrodynamic expansion of the QGP.
118691614
Coherence effects between the initial and final state radiation in a dense QCD medium
Abstract In these proceedings contribution we review our recent results of medium modifications to the coherence pattern between the initial and final state radiation. We study single gluon production off a highly energetic parton that undergoes a hard scattering and subsequently crosses a dense QCD medium of finite size. Multiple scatterings lead to a partial suppression of the interferences between different emitters that opens the phase space for large angle emissions. We briefly discuss the generalization of this setup to describe gluon production in the case of pA collisions by including finite length and energy corrections. The configuration studied here may have phenomenological consequences in high-energy nuclear collisions.
121540832
A very forward luminosity monitor for the ALEPH detector at LEP
Abstract The design of a very small angle luminosity monitor for the ALEPH detector at LEP is described. The detector consists of four calorimeter modules made of alternating layers of tungsten and scintillators plus one layer of silicon strips for shower localization. Tests of the performance of the calorimeter and initial results obtained in LEP are also described.
115544761
High-energy dileptons from an anisotropic quark-gluon plasma
We calculate leading-order dilepton yields from a quark-gluon plasma which has a time-dependent anisotropy in momentum space. Such anisotropies can arise during the earliest stages of quark-gluon plasma evolution due to the rapid longitudinal expansion of the created matter. A phenomenological model for the proper time dependence of the parton hard momentum scale, p_hard, and the plasma anisotropy parameter, xi, is proposed. The model describes the transition of the plasma from a 0+1 dimensional collisionally-broadened expansion at early times to a 0+1 dimensional ideal hydrodynamic expansion at late times. We find that high-energy dilepton production is enhanced by pre-equilibrium emission up to 50% at LHC energies, if one assumes an isotropization/thermalization time of 2 fm/c. Given sufficiently precise experimental data this enhancement could be used to determine the plasma isotropization time experimentally.
11938821
Search for new phenomena in events with a monojet and large missing transverse momentum at the LHC using the ATLAS detector
We report preliminary results on a search for new phenomena in an event sample with monojets and large missing transverse momentum in the final state. The analysis uses 1.00 fb−1 of data collected in 2011 with the ATLAS detector [1]. Good agreement is observed between the number of events in data and the Standard Model predictions. The results are translated into improved limits on a model with Large Extra Dimensions.