73648727
Polarization control proposal for Shanghai deep ultraviolet free electron laser
In this paper, a fully coherent radiation option with controllable polarization is proposed for the Shanghai deep ultraviolet free electron laser (FEL) test facility. Intensive start-to-end simulation suggests that the two crossed planar undulators which generate the horizontal and vertical linear polarized FEL, should be placed as close as possible for avoiding the polarization performance degradation of the final combined FEL radiation. With the existence of the phase-shifter between the two crossed radiators. Fourier-Transform-Limited output radiation with 100 nJ order pulse energy, 5 Ps full pulse length and circular polarization degree above 90% could be achieved. (C) 2012 Elsevier B.V. All rights reserved.
124860564
Short-pulse length effects of the seed laser in high-gain harmonic generation free-electron laser
In order to generate coherent hard x-ray free-electron laser ( FEL), cascading stages of high-gain harmonic generation ( HGHG) scheme usually employ seed pulse with longitudinal length down to tens of femtoseconds. Such a short pulse length ( SPL) seed laser, with broad bandwidth in the spectral domain, can no longer be characterized by monochromatic light in FEL equations. In this paper, a set of self-consistent, multifrequency FEL equations is derived to describe the interaction between the seed laser and the electrons in the modulator of HGHG. Moreover, the SPL effects of the seed laser on the electron beam's energy modulation, the output pulse length, the output peak power, and the output wavelength tuning in HGHG are theoretically and numerically investigated. Study demonstrates that the SPL seed laser seriously and significantly influences the HGHG performances, and these influences have to be taken into account in the design and optimization of the seeded FEL scheme.
3066888
Global quark polarization in non-central A+A collisions
Partons produced in the early stage of non-central heavy-ion collisionscan develop a longitudinal fluid shear because of unequal local number densities of participant target and projectile nucleons. Under such fluid shear, local parton pairs with non-vanishing impact parameter have finite local relative orbital angular momentum along the direction opposite to the reaction plane. Such finite relative orbitalangular momentum among locally interacting quark pairs can lead to global quark polarization along the same direction due to spin-orbital coupling. Local longitudinal fluid shear is estimated within both Landau fireball and Bjorken scaling model of initial parton production. Quark polarization through quark-quark scatterings with the exchange of a thermal gluon is calculated beyond small-angle scattering approximation in a quark-gluon plasma. The polarization is shown to have a non-monotonic dependence on the local relative orbital angular momentum dictated by the interplay between electric and magnetic interaction. It peaks at a value of relative orbital angular momentum which scales with the magnetic mass of the exchanged gluons. With the estimated small longitudinal fluid shear in semi-peripheral Au+Au collisions at the RHIC energy, the final quark polarization is found to be small left hbar P_q right hbar <0.04 in the weak coupling limit. Possible behavior of the quark polarization in the strong coupling limit and implications on the experimental detection of such global quark polarization at RHIC and LHC are also discussed.
15877154
Tomography of high-energy nuclear collisions with photon-hadron correlations.
Within the next-to-leading order (NLO) perturbative QCD (PQCD) parton model, suppression of away-side hadron spectra associated with a high pT photon due to parton energy loss is studied in high-energy heavy-ion collisions. Because of the sharp falloff of the gamma-jet spectrum in momentum imbalance pTjet-pTgamma>0 in NLO PQCD, hadron spectra at large zT=pTh/pTgamma greater than approximately 1 are more susceptible to parton energy loss and therefore are dominated by surface emission of gamma-associated jets with almost no energy loss, whereas small zT hadrons mainly come from the volume emission of jets with reduced energy. These lead to different centrality dependence of the gamma-hadron suppression for different values of zT. Therefore, a complete measurement of the suppression of gamma-triggered hadron spectra allows a true tomographic study of the quark-gluon plasma in high-energy heavy-ion collisions.
123423629
Implications of the top quark mass measurement for the SM Higgs boson mass MH
Motivated by the recent determination of the top quark mass by the CDF Collaboration Mt=174+or-10-12+13 GeV, we study,the implications of the top quark mass measurement for the standard model Higgs boson mass MH based on the phenomenological analysis of the radiative correction Delta r at two-loop order. We find that: (a) the central value of MH is very sensitive to the variation of Mt; (b) the present data are in favour of the heavy Higgs boson, MH=340-270+770 GeV for Mt=174 GeV, but no reliable constraints on MH could be derived until the measurement of Mt reaches high precision.
119224614
Bulk matter evolution and extraction of jet transport parameter in heavy-ion collisions at RHIC
Xiao-Fang Chen, 2 Carsten Greiner, Enke Wang, Xin-Nian Wang, 2 and Zhe Xu 2 Institute of Particle Physics and Key Laboratory of Quark & Lepton Physics, Huazhong Normal University, Wuhan 430079, China Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main, Germany Nuclear Science Division, MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, D-60438 Frankfurt am Main, Germany (Dated: February 5, 2010)
122096987
ASSOCIATED PRODUCTION OF SINGLE HEAVY T-QUARK IN THE LEFT–RIGHT TWIN HIGGS MODEL AT THE LHC
The heavy T-quark is one of the most crucial ingredients in the left–right twin Higgs model, which is introduced to cancel the largest contribution of the Standard Model top quark to the Higgs boson mass at one-loop level. In this paper, we study the relevant single heavy T-quark production processes, the 2 → 2 partonic processes of qb → q'T and , the 2 → 3 partonic processes of and at the CERN LHC. Our numerical results show that the 2 → 3 process can be quite important, as its cross-section is about 60% of that for the 2 → 2 process at the LHC. We also show the pT distribution and the rapidity distributions for out-going particles. For the 2 → 3 process, the production rate of the final state can be larger than 100 fb with reasonable values of the free parameters. The possible signatures of the heavy T-quark might be detected via the process at the LHC.