36601565
Next-to-eikonal corrections in the CGC: gluon production and spin asymmetries in pA collisions
A bstractWe present a new method to systematically include corrections to the eikonal approximation in the background field formalism. Specifically, we calculate the subleading, power-suppressed corrections due to the finite width of the target or the finite energy of the projectile. Such power-suppressed corrections involve Wilson lines decorated by gradients of the background field — thus related to the density - of the target. The method is of generic applicability. As a first example, we study single inclusive gluon production in pA collisions, and various related spin asymmetries, beyond the eikonal accuracy.
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.
117317073
Anisotropic hydrodynamics - basic concepts
Due to the rapid longitudinal expansion of the quark-gluon plasma created in relativistic heavy ion collisions, potentially large local rest frame momentum-space anisotropies are generated. The magnitude of these momentum-space anisotropies can be so large as to violate the central assumption of canonical viscous hydrodynamical treatments which linearize around an isotropic background. In order to better describe the early-time dynamics of the quark gluon plasma, one can consider instead expanding around a locally anisotropic background which results in a dynamical framework called anisotropic hydrodynamics. In this proceedings contribution we review the basic concepts of the anisotropic hydrodynamics framework presenting viewpoints from both the phenomenological and microscopic points of view.
118662616
Constraining relativistic viscous hydrodynamical evolution
We show that by requiring positivity of the longitudinal pressure it is possible to constrain the initial conditions one can use in second-order viscous hydrodynamical simulations of ultrarelativistic heavy-ion collisions. We demonstrate this explicitly for (0+1)-dimensional viscous hydrodynamics and discuss how the constraint extends to higher dimensions. Additionally, we present an analytic approximation to the solution of (0+1)-dimensional second-order viscous hydrodynamical evolution equations appropriate to describe the evolution of matter in an ultrarelativistic heavy-ion collision.
118399487
Generalization of Gunion-Bertsch formula for soft gluon emission
We generalize the most extensively used Gunion-Bertsch formula for the soft gluon emission in a perturbative QCD. We show that the corrections arising due to this generalization could be very important for the phenomenology of the hot and dense matter produced in the heavy-ion collisions.
119256392
Constraining the onset of viscous hydrodynamics
Abstract We derive two general criteria that can be used to constrain the initial time of the onset of 2nd-order conformal viscous hydrodynamics in relativistic heavy-ion collisions. We show this explicitly for 0+1 dimensional viscous hydrodynamics and discuss how to extend the constraint to higher dimensions.
122254977
Inclusive Search for Squark and Gluino Production at CDF
We present preliminary results on the search for squark and gluino production in proton-antiproton collisions at s = 1.96 TeV using 1.1 fb −1 of CDF Run II data. Events with multiple jets of hadrons and large missing transverse energy in the final state are studied within mSUGRA framework and assuming R-parity conservation. No excess with respect to Standard Model predictions is observed. In a mSUGRA scenario with A 0 = 0 , μ 0 and tan β = 5 , we exclude masses up to about 380 GeV / c 2 at 95% C.L. in the region where gluino and squark masses are similar.
122001499
Experimental review of jet physics in hadronic collisions
In this contribution, a comprehensive review of the main aspects of high pT jet physics in Run II at the Tevatron is presented. Recent measurements on inclusive jet production are discussed using different jet algorithms and covering a wide region of jet transverse momentum and jet rapidity. Several measurements, sensitive to a proper description of soft gluon radiation and the underlying event in hadron collisions, are shown. Finally, high pT prompt photon measurements, and studies on the production of electroweak bosons in association with jets in the final state are discussed.
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.
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.