111028273
BEAM DYNAMICS SIMULATION OF W-BAND PHOTOINJECTOR
We present a beam dynamics simulation study on 1.6 cell,high gradient W-Band photocathode RF gun which is capable of generating and accelerating 300pC electron bunch. The design system is made up of 91.392GHz photocathode RF gun and 91.392GHz travelling wave linac cells. Based on the numerical simulation using SUPERFISH and PARMELA and the conventional RF linac scaling law,the design will produce 300pC at 1.74MeV with bunch length 0.72ps and normalized tranverse emittance 0.55mm mrad. We study the beam dynamics in high frequency and high gradient;due to the high gradient,the ponderomotive effect plays an important role in beam dynamics; we found the ponderomotive effect still exist with only the fundamental space harmonics (synchrotron mode) due to the coupling of the transverse and longitudinal motion.
118521516
LWFA as a Preinjector for XFEL Driver Linac
In this paper, we propose to use the LWFA as the preinjector for XFEL driver linac. We can use LWFA to produce the femtosecond electron beam. The peak current of the produced beam can reach tens of $kA$ and is high enough to drive XFEL so that the present bunch compressing technique can be deserted. The output optical pusle length can be as short as $ 1 fs $.
123188749
Layout of bunch compressor for Beijing XFEL test facility
In this paper, we describe the layout of the bunch compressor for the Beijing XFEL test facility (BTF). Our bunch compressor setup is different from the usual one due to the space limit. The compensation X-BAND cavity and the first bunch compressor are separate in distance. The electron bunch is decelerated first and then accelerated to enter the first bunch compressor. The simulation result shows that our setup works well, and the nonlinear term is well compensated. Also, we present the result about the CSR emittance dilution study. Finally, we develop a program to study microbunch instability in the second BTF bunch compressor.
118882297
1D Longitudinal Beam Dynamics of Laser Plasma Wakefield Accelerator
In this paper, we get the 1D approximate analytical solution of the plasma electrostatic wake driven by the laser, and get the oscillating frequency of the wake modified by the nonlinear high order terms, and find that the frequency depends on the oscillating amplitudes of the wake and the laser which is the general nonlinear phenomenon. Finally we analyze the longitudinal beam dynamics in this electrostatic wake, and find that the high order terms don't change the topology of the longitudinal phase space.
119109800
Study on the production of the subpicosecond electron bunch
The production of the high brightness femtosecond electron bunch is now one of the hot research topics. This paper describes one electron linac facility used to produce the subpicosecond electron bunch. We analyze the main structure parameters, and study the beam dynamics of the facility. Finally, we discuss the application of this facility in Compton scattering.
120786763
Is constituent quark scaling a unique sign of parton recombination?
We study the transverse momentum dependence of the anisotropic flow v2 for π, K, nucleon, Λ, Ξ and Ω for Au+Au collisions at $\sqrt{s_{NN}} = 200\,\mathrm{GeV}$ within two independent string-hadron transport approaches (RQMD and UrQMD). Although both models reach only 60% of the absolute magnitude of the measured v2, they both predict the particle-type dependence of v2 as observed by the RHIC experiments: v2 exhibits a hadron-mass hierarchy in the low pT region and a number-of-constituent-quark (NCQ) dependence in the intermediate pT region. The failure of the hadronic models to reproduce the absolute magnitude of the observed v2 indicates that transport calculations of heavy-ion collisions at RHIC must incorporate interactions among quarks and gluons in the early, hot and dense phase. The presence of an NCQ scaling in the string-hadron model results suggests that the particle-type dependences observed in heavy-ion collisions at intermediate pT might be related to the hadronic cross sections in vacuum rather than to the hadronization process itself.
119304211
Hybrid model approach for strange and multistrange hadrons in 2.76A TeV Pb+Pb collisions
Using the VISHNU hybrid model, we calculate the multiplicity, spectra, and elliptic flow of $\Lambda$, $\Xi$ and $\Omega$ in 2.76 A TeV Pb+Pb collisions. Comparisons between our calculations and the ALICE measurements show that the model generally describes the soft hadron data of these strange and multi-strange hadrons at several centrality bins. Mass ordering of elliptic flow among $\pi$, K, p, $\Lambda$, $\Xi$ and $\Omega$ has also been studied and discussed. With a nice description of the particle yields, we explore chemical and thermal freeze-out of various hadrons species at the LHC within the framework of the VISHNU hybrid model.
119431648
Recent results on strangeness production at STAR
We report on the measurements of strange hadrons (K±, K0S, Λ, Ξ, Ω and ) production at mid-rapidity in Au+Au collisions at = 7.7 - 39 GeV from the STAR beam energy scan (BES) program. The collision energy dependence of strange hadron yields are presented. The strange hadron related particle ratios are compared with calculations from statistical and hadronic cascade models. The nuclear modification factors and baryon to meson ratios (/K0S and Ω/) are presented. The physics implications for collision dynamics are discussed.
56119429
Centrality dependence of particle production in p-Pb collisions at $\sqrt{s_{\rm NN} }$= 5.02 TeV
We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at sNN=5.02TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (Npart) or the number of nucleon-nucleon binary collisions (Ncoll) are described. We show that, in contrast to Pb-Pb collisions, in p-Pb collisions large multiplicity fluctuations together with the small range of participants available generate a dynamical bias in centrality classes based on particle multiplicity. We propose to use the zero-degree energy, which we expect not to introduce a dynamical bias, as an alternative event-centrality estimator. Based on zero-degree energy-centrality classes, the Npart dependence of particle production is studied. Under the assumption that the multiplicity measured in the Pb-going rapidity region scales with the number of Pb participants, an approximate independence of the multiplicity per participating nucleon measured at mid-rapidity of the number of participating nucleons is observed. Furthermore, at high-pT the p-Pb spectra are found to be consistent with the pp spectra scaled by Ncoll for all centrality classes. Our results represent valuable input for the study of the event-activity dependence of hard probes in p-Pb collisions and, hence, help to establish baselines for the interpretation of the Pb-Pb data.
209834012
Two-particle correlations in pp and Pb-Pb collisions with ALICE
The measurement of azimuthal correlations between two particles is a powerful tool to investigate the properties of strongly-interacting nuclear matter created in ultra-relativistic heavy-ion collisions. We present measurements of di-hadron correlations in azimuth angle and pseudorapidity in Pb-Pb collisions at and photon-hadron correlations in pp collisions at with the ALICE detector, respectively. In di-hadron correlations, the near-side jet shape in the short-range correlation region is quantitatively analyzed at pT, trig < 8 GeV/c, and the modification of jet-particle yield, IAA and ICP, is measured at 8 < pT, trig < 15 GeV/c. In photon-hadron correlations, isolated leading photon and associated hadrons in its opposite azimuthal direction correlations are used to estimate the jet fragmentation function via the imbalance parameter, .