2007 Vol. 31, No. 12
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We show how to obtain the real orthogonal form of [n—1, 1] representation of Sn group by using a trick, representing Sn group in a special representation space. At last, we exemplify one of the applications of the trick.
The neutron-rich nucleus 11Li is separated by the radioactive ion beam line RIBLL at HIRFL from the breakup of 50MeV/u 13C on Be target. The total reaction cross sections for 11Li at energies range from 25 to 45MeV/u on Si target have been measured by using the transmission method. The experimental data at high and low energies can be fitted well by Glauber model using two Gauss density distribution. The matter radius of 11Li was also deduced.
The ground-state properties of superheavy nuclide 294118 and it's α-decay daughters are investigated in the deformed relativistic mean field (RMF) theory with the TMA effective interaction, where the pairing correlations are treated with the usual BCS approximation. Binding energies per nucleon, alpha decay energies and deformations are calculated and compared with the known experimental data. A good agreement between the calculated result and the data is obtained. This shows the validity of RMF theory in studying the ground state properties of super heavy nuclei.
Based on the improved nuclear density model and the condition of the nuclear momentum conservation, we derived the formula of the nuclear effect parameter formula for the nuclear gluon distribution function, in which our established connection between the nuclear density and the mean binding energy in nucleus is used. By using the formula, we can well explain the experimental data of the J/ψ photoproduction in the l-A process.
The dark current, charge collection efficiency and time response properties of CVD diamond film detectors are studied based on experiments and their theoretic analysis. The results shows: No PN or PIN junctions are needed when preparing diamond detectors; charge collection efficiency of the detector will be reduced by defects in film, and it increases and reaches saturation along with the increasing electric field between the two electrodes. The charge collection time of our diamond film detector is about 719ps, and the charge collection efficiency can reach the saturation value of 60.5% under the electric field of 2.5V/μm. Scattering of the lattice may slow the detector response, so it's necessary to improve CVD technology and choose diamond film with big grain size.
Water-cooling serves two functions in an RFQ. One is to take away the power dissipated on the inside surface of the RFQ by the RF field to maintain the thermal stability and to limit the deformation of RFQ. The other is to be used to tune the RFQ basically without effecting the field distribution when the RFQ is out of resonance, since the beam transmission of RFQ is very sensitive to the field profile, the ordinary frequency tuning method by the movable tuners is no more adopted in an RFQ operation. The cooling water channel position and number, as well as the optimum cooling water temperature are determined through thermal analysis. In addition, the tuning method by adjusting the cooling water temperature is determined when the RFQ is out of resonance.
According to the operation and development of radiation therapy in the world, in order to further promote the radiation therapy of tumour in China, a design of a special synchrotron with two super-periodicity for hadron therapy is presented, including lattice, injection system, RF acceleration and slow extraction of the third order resonance. The synchrotron accelerates the proton beam to 250MeV and the carbon beam to 400MeV/u.
A study of Mach shocks generated by fast partonic jets propagating through the quark-gluon plasma (QGP) is reviewed briefly. We predict a significant deformation of Mach shocks in central Au+Au collisions at RHIC and LHC energies compared to those created by a jet propagation through a static medium. Moreover, a new hydrodynamical study of jet energy loss is presented.
Particle type dependences of hadron yield and emission patterns, especially its difference between mesons and baryons, at intermediate pT(2—5GeV/c) is one of the findings in heavy ion collisions at RHIC. A systematic study of identified hadron production was performed in Au+Au/Cu+Cu collisions at sNN=62.4/200GeV, to investigate the possible origins of this difference. In this paper, we show particle ratios, elliptic flow strengths, and their scaling properties.
Recent measurements of event-by-event elliptic flow in Au+Au collisions at sNN=200GeV exhibit large relative fluctuations of about 40%—50%. The data are well described by fluctuations in the shape of the initial collision region, as estimated event-by-event with the participant eccentricity using Glauber Monte Carlo. These results, combined with the demonstrated participant eccentricity scaling of the elliptic flow across nuclear species, constitute evidence of transverse granularity in the initial matter production in these collisions.
R.Bindel7, W.Busza4, Z.Chai2, V.Chetluru6, E.Garcia6 and T.Gburek3. Eccentricities of Flow-Elliptic Flow Fluctuations and Evidence for Transverse Localization in the Initial State of the Matter in Relativistic Heavy Ion Collisions[J]. Chinese Physics C, 2007, 31(12): 1133-1136.
Identified particle elliptic flow results are presented for the Au+Au reaction at sNN=200GeV as a function of transverse momentum and pseudorapidity. Data at pseudorapidities η≈0,1, and 3.4 were obtained using the two BRAHMS spectrometers. Differential v2 (η,pt) values for a given particle type are found to be essentially constant over the covered pseudorapidity range, in contrast to the integral v2 values which have previously been observed to decrease at forward rapidities. A softening of the particle spectra at forward angles is found to account for at least part of the integral v2 falloff. The data are found to be consistent with existing constituent quark scaling systematics.
We explore the NJL model with Polyakov loops for a system of three colors and two flavors within the mean-field approximation, where both chiral symmetry and confinement are taken into account. We focus on the phase structure of the model and study the chiral and Polyakov loop susceptibilities.
Integrated two particle correlation functions have been extracted from charge particle multiplicity density fluctuations in pseudorapidity space by analyzing Au+Au collision events at sNN=200GeV taken by RHIC-PHENIX. The correlation lengths as a function of the number of participants Np indicate a non monotonic increase at around Np=100 and the corresponding energy density based on the Bjorken picture is εBjτ～2.5GeV.fm－2. This could be a symptom of a critical behavior.
We report the results on anisotropic flows and their scaling for φ mesons and Ω (Ω－+Ω+) baryons in Au+Au collisions at RHIC, obtained from a dynamical quark coalescence model that uses the quark phase-space information from a multi-phase transport (AMPT) model within the string melting scenario and includes the quark structure of hadrons.
We present various predictions for the anisotropic collective flow of particles in heavy-ion collisions, in particular scaling laws of the second and fourthharmonics v2 and v4, derived within ideal fluid dynamics. We also discuss qualitatively the deviation from the ideal behaviour expected in an out-of-equilibrium scenario.
We briefly discuss the phenomenological theory of dissipative fluid. We also present some numerical results for hydrodynamic evolution of QGP fluid with dissipation due to shear viscosity only. Its effect on particle production is also studied.
We investigate coefficients in the Israel-Stewart's causal hydrodynamics and discuss the way to calculate them microscopic theory. Based on the hadro-molecular simulation based on an event generator URASiMA, we evaluate the coefficients for a hot and dense hadronic fluid.
A new method is presented for measuring event-by-event fluctuations of elliptic flow (v2) using first-order event planes. By studying the event-by-event distributions of v2 observables and first-order event-plane observables, average flow 〈v2〉and event-by-event fluctuations with respect to that average can be separately determined, making appropriate allowance for the effects of finite multiplicity. The relation of flow fluctuations to eccentricity fluctuations in the initial-state participant region, as well as detector acceptance effects, are discussed.
Elliptic flow is easy to compute in hydrodynamics. However experimentally it is obtained in an indirect way. The question we address in this paper is how comparable are these two approaches. For both cases, our study is done using the hydrodynamical code NeXSPheRIO and simulating nuclear collisions at RHIC.
Azimuthal anisotropy of direct photon is measured in sNN=200GeV Au+Au collisions at RHIC-PHENIX. Direct photon is one of the most effective probes to study properties of hot dence medium at initial state (also QGP state) of heavy ion collisions because photons almost do not interact strongly with any other particles caused by its long mean free path and they keep their conditions when they are created. Within statistical and systematic errors, the elliptic flow parameter (v2) of direct photon is consistent with zero. Direct photon v2 is estimated by hadron decay photon contamination are subtracted from inclusive photon v2 in intermediate to high transverse momentum (pT) region (0 to 10GeV/c) for 3 centrality selections (20% steps) and minimum bias.
An internal target experiment at HIRFL-CSRm is planned for hadron physics, which focuses on hadron spectroscopy, polarized strangeness production and medium effect. A conceptual design of Hadron Physics Lanzhou Spectrometer (HPLUS) is discussed. Related computing framework involves event generation, simulation, reconstruction and final analysis. The R & D works on internal target facilities and sub-detectors are presented briefly.
There exists a large local relative orbital angular momentum between produced partons along the direction opposite to the reaction plane in the early stage of non-central heavy-ion collisions. This initial local orbital angular momentum can lead to quark polarization along the same direction due to spin-orbital coupling in QCD. We present the quark polarization by using hard thermal loop gluon propagator for quark-quark scattering in quark-gluon plasma and compare it with the result obtained from the static potential model.
We present the Λ-hyperon global polarization in Au+Au collisions at sNN=62GeV and 200GeV measured with the STAR detector at RHIC. The observed Λ-hyperon global polarization is consistent with zero, what is in agreement with recent measurements of Λ global polarization, as well as φ(1020) and K*0(892) vector mesons spin alignment with respect to the reaction plane. The possible dependence of the global polarization on relative azimuthal angle between the orbital momentum of the system and the hyperon 3-momentum is discussed. The corresponding systematic uncertainty due to detector acceptance is found to be less than 20%.
We study the polarization of produced Λ in s=200GeV polarized proton-proton collision at RHIC/PHENIX, and also the polarization as a function of its rapidity which may be sensitivity to the quark helicity distributions of the proton and to the polarized fragmentation functions of the quark into the baryon. For polarized data collected in 2003 a very clean Λ peak in pπ+ invariant mass spectrum in the mid-rapidity(|η|<0.35) is obtained. In this letter, we report the calculation process of PΛ as extracted from the data.
We present the preliminary results on the spin alignment matrix element ρ00 for vector mesons K*0(892) and φ(1020) in mid-central (20%—60%) Au+Au and p+p collisions at sNN=200GeV. The values of ρ00 with respect to reaction plane in Au+Au collisions are 0.36±0.02(stat)±0.13(sys) for K*0(892) and 0.38±0.01 (stat)±0.04 (sys) for φ(1020). No evident global spin alignment with respect to reaction plane is observed in the measured pT region up to 5GeV/c with current sensitivity. ρ00 with respect to the production plane of the vector meson is also measured for K*0(892) and φ(1020) in Au+Au collisions, and for φ(1020) in p+p collisions. No significant difference for the ρ00 between Au+Au and p+p collisions is observed with our data sample.
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