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.
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.
119217468
Non-boost-invariant anisotropic dynamics
Abstract We study the non-boost-invariant evolution of a quark–gluon plasma subject to large early-time momentum–space anisotropies. Rather than using the canonical hydrodynamical expansion of the distribution function around an isotropic equilibrium state, we expand around a state which is anisotropic in momentum space and parameterize this state in terms of three proper-time and spatial-rapidity dependent parameters. Deviations from the Bjorken scaling solutions are naturally taken into account by the time evolution of the spatial-rapidity dependence of the anisotropic ansatz. As a result, we obtain three coupled partial differential equations for the momentum–space anisotropy, the typical momentum of the degrees of freedom, and the longitudinal flow. Within this framework ( 0 + 1 ) -dimensional Bjorken expansion is obtained as an asymptotic limit. Finally, we make quantitative comparisons of the temporal and spatial-rapidity evolution of the dynamical parameters and resulting pressure anisotropy in both the strong and weak coupling limits.
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.
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.
123410491
Z plus jets production at the tevatron
We present preliminary results on inclusive Z(→ee) boson plus jets production in pp collisions at s√ = 1.96 TeV, based on 1.7 fb-1 of data collected by the CDF experiment. Inclusive jet measurements are performed as function of pTjet and jet multiplicity for jets in the region of pTjet > 30 GeV/c and |yjet | < 2.1. Results are compared to NLO pQCD predictions and are found to be in good agreement.
119286570
Pre-equilibrium dilepton production from an anisotropic quark-gluon plasma
We calculate leading-order dilepton yields from a quark-gluon plasma that 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. Two phenomenological models for the proper-time dependence of the parton hard momentum scale, ${p}_{\mathrm{hard}}$, and the plasma anisotropy parameter, \ensuremath{\xi}, are constructed that describe the transition of the plasma from its initial nonequilibrium state to an isotropic thermalized state. The first model constructed interpolates between 1+1 dimensional free streaming at early times and 1+1 dimensional ideal hydrodynamical expansion at late times. In the second model we include the effect of collisional broadening of the parton distribution functions in the early-time pre-equilibrium stage of plasma evolution. We find for both cases that for fixed initial conditions high-energy dilepton production is enhanced by pre-equilibrium emission. When the models are constrained to fixed final pion multiplicity the dependence of the resulting spectra on the assumed plasma isotropization time is reduced. Using our most realistic collisionally broadened model we find that high-transverse-momentum dilepton production would be enhanced by at most 40% at the Relativistic Heavy Ion Collider and 50% at the CERN Large Hadron Collider 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.