38030105
Ultrashort high quality electron beam from laser wakefield accelerator using two-step plasma density profile.
In this paper, we first use the rf linac injector mechanism to generate ultrashort high quality electron beam from laser wakefield accelerator (LWFA) with two-step plasma density profile successfully. We incorporate the physics principle in the conventional rf linac injector into the LWFA by using two-step plasma density to decrease the wavelength of the wakefield in plasma. Using this mechanism, we observe a ultrashort high quality electron beam (the rms energy spread is 1.9%, and the rms bunch length is 2 fs) in the simulation. The ultrashort intense terahertz coherent radiation (200 MW, 2 fs) can be generated with the proposed laser wakefield accelerator.
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.
211628052
PLASMA-FILLED WAVEGUIDE FOCUSING LENS
Large transverse wakefields can be generated via the interaction between a relativistic electron or positron bunch and a plasma, and the bunch will therefore be self-pinched. Based on this effect, Chen suggested a plasma lens theory for future linear colliders; there are also many experimental studies on plasma focus devices.2In this paper, we study this problem further. Instead ofunbound plasma, we suppose that the plasma is bounded by cylindrical waveguide with ideally conducting wall. We find that the boundary can strengthen the focusing effect on the charged particle beam. Finally, a numerical example is given.
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.
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.
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.
35833011
Effect of partonic "wind" on charm quark correlations in high-energy nuclear collisions.
In high-energy collisions, massive heavy quarks are produced back to back initially and they are sensitive to early dynamical conditions. The strong collective partonic wind from the fast expanding quark-gluon plasma created in high-energy nuclear collisions modifies the correlation pattern significantly. While the hot and dense medium in collisions at the BNL Relativistic Heavy Ion Collider (sqrt[_s{NN}]=200 GeV) can only smear the initial back-to-back D_D correlation, a clear and strong near side D_D correlation is expected at the CERN Large Hadron Collider (sqrt[_s{NN}]=5500 GeV). This is considered as a signature for the strongly coupled quark-gluon plasma.
122820296
Influence of the non-flow effects and fluctuations on the v 2 measurements at RHIC
The cumulant method is applied to study elliptic flow (v2) in Au+Au collisions at √s = 200 AGeV, with the UrQMD model. We find that the four and six-particle cumulants are good measures of the real elliptic flow over a wide range of centralities except for the most central and very peripheral events. There the cumulant method is affected by the v2 fluctuations. In mid-central collisions, the four and six-particle cumulants are shown to give a good estimation of the true differential v2, especially at large transverse momentum, where the two-particle cumulant method is heavily affected by the non-flow effects.
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.
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.