Centrality dependence of pT spectra for identified hadrons in Au+Au and Cu+Cu collisions at √sNN= 200GeV

The centrality dependence of transverse momentum spectra for identified hadrons at midrapidity in Au+Au collisions at √s_NN= 200GeV is systematically studied in a quark combination model. The p_T spectra of π^±, K^±, p(p) and Λ(Λ) in different centrality bins and the nuclear modification factors (R_CP) for these hadrons are calculated. The centrality dependence of the average collective transverse velocity 〈β(r)〉 for the hot and dense quark matter is obtained in Au+Au collisions, and it is applied to a relative smaller Cu+Cu collision system. The centrality dependence of p_T spectra and the R_CP for π⁰, K_s⁰ and Λ in Cu+Cu collisions at √s_NN= 200GeV are well described. The results show that 〈β(r)〉 is only a function of the number of participants N_part and it is independent of the collision system.     

Study of the total reaction cross section via QMD

This paper presents a new empirical formula to calculate the average nucleon-nucleon (N-N) collision number for the total reaction cross sections (σ_R). Based on the initial average N-N collision number calculated by quantum molecular dynamics (QMD), quantum correction and Coulomb correction are taken into account within it. The average N-N collision number is calculated by this empirical formula. The total reaction cross sections are obtained within the framework of the Glauber theory. σ_R of ²³Al+¹²C, ²⁴Al+¹²C, ²⁵Al+¹²C, ²⁶Al+¹²C and ²⁷Al+¹²C are calculated in the range of low energy. We also calculate the σ_R of ²⁷Al+¹²C with different incident energies. The calculated σ_R are compared with the experimental data and the results of Glauber theory including the σ_R of both spherical nuclear and deformed nuclear. It is seen that the calculated σ_R are larger than σ_R of spherical nuclear and smaller than σ_R of deformed nuclear, whereas the results agree well with the experimental data in low-energy range.     

Dependence of the cross sections for Ir isotopes on the values of Qgg in the heavy ion collision

¹⁹⁷Au were irradiated with 47 MeV/u ¹²C ions. Iridium was produced via the multinucleon transfer reactions in bombardments of ¹⁹⁷Au with ¹²C. and was separated radiochemically from Au and the mixture of the reaction products. The γ radioactivities of Ir isotopes were measured by using a HPGe detector. The production cross sections of Ir isotopes were determined from activities of Ir isotopes at the end of bombardment and the other relative data. It has been found that the cross sections for neutron-rich isotopes of iridium show an exponential dependence on the values of Q_gg. Our experimental results also demonstrate lack of correlation between the cross sections and Q_gg in the case of neutron-deficient isotopes of iridium. The fact can be explained from that neutron-rich isotopes of iridium were produced in the deep inelastic transfer reactions.     

Temperature-dependent cross sections for πφ and ρφ nonresonant reactions in hadronic matter

With a potential of which the large-distance part reflects lattice gauge results and of which the short-distance part is given by one gluon exchange plus perturbative one- and two-loop corrections, the Schrödinger equation brings about temperature dependence of meson masses and mesonic quark-antiquark relative-motion wave functions. The ground-state meson masses drop with increasing temperature. The transition amplitude calculated from the potential, the meson masses and the wave functions gives temperature-dependent cross sections for the five nonresonant reactions πφ→KK^* (or K^*K), πφ→K^*K^*,ρφ→KK,ρφ→KK^*(orK^*K) and ρφ→K^*K^*. The numerical temperature-dependent cross sections are parametrized. The peak cross section of either πφ→KK^* or πφ→K^*K^* increases from T=0 to T=0.75T_c and decreases with further increasing temperature. The cross section for ρφ→KK,ρφ→KK^* and ρφ→K^*K^* has a decreasing trend while the temperature increases from 0.75T_c.     

Evidence for e+e-→γχc1,2 at center-of-mass energies from 4.009 to 4.360 GeV

Using data samples collected at center-of-mass energies of √s=4.009, 4.230, 4.260, and 4.360 GeV with the BES0 detector operating at the BEPC/ collider, we perform a search for the process e⁺e^-→γχ_c,j (J =0, 1, 2) and find evidence for e⁺e^-→γχ_c1 and e⁺e^-→γχ_c2 with statistical significances of 3.0σ and 3.4σ, respectively. The Born cross sections σ^B(e⁺e^-→γχ_c,j), as well as their upper limits at the 90% con dence level (C.L.) are determined at each center-of-mass energy.     

Drell-Yan dilepton production in relativistic heavy-ion collisions at RHIC

We investigate the lepton pair production with the Drell-Yan process in relativistic heavy ion collisions by computing the double differential cross section dσ/dM²dy and dσ/dM²dx_F at the next-to-leading order in p+Au and Au+Au collisions with √s_NN =200 GeV at RHIC. The resulting nuclear modification factors R^pAu and R^AuAu show strong sensitivity to the cold nuclear matter (CNM) effects and could probe the CNM effects at a very wide region of the longitudinal momentum fraction x. The variation of R with the invariant mass M, the rapidity y and the Feynman variable x_F is shown and we find that the nuclear modification factor for the double differential cross section could be smaller than 0.4 in some kinematic regions of high-energy nucleus-nucleus reactions at RHIC.     

Studies on the exotic structure of 23Al

The longitudinal momentum distribution (P_//) of fragments after one-proton removal from ²³Al and reaction cross sections (σ_R) for ^23,24Al on carbon target at 74A MeV have been measured simultaneously. An enhancement in σ_R is observed for ²³Al compared with ²⁴Al. The full width at half maximum of the P_// distribution for ²²Mg fragments has been determined to be 232±28 MeV/c. Analysis of P_// using the Few-Body Glauber Model indicates a dominant d-wave configuration for the valence proton in the ground state of ²³Al. The exotic structure in ²³Al is discussed.     

Study of ππ production in two-photon collisions at Belle

We have measured the cross section for π⁺π^－ production in two-photon collisions using a data sample with an integrated luminosity of 85.9fb^－1 collected with the Belle detector. The f₀(980) resonance is observed as a peak in the energy spectrum of the cross section. We also report preliminary results for γγ→π⁰π⁰ with two-photon center-of-mass energies ranging from 0.6 to 4.0GeV, based on a 95fb^－1 data sample. We find at least four resonant structures including a peak from f₀(980). In addition, there is evidence for χ_c0 production. We also make a preliminary discussion of the angular dependence and cross section ratio of γγ→π⁺π^－ and γγ→π⁰π⁰.     

Production cross-section of 230Ra in the reaction of 60 MeV/u 18O ions with 238U

A thick natural uranium target was bombarded with a 60 MeV/u ¹⁸O beam. The neutron-rich isotope ²³⁰Ra as the target residue was produced through the multinucleon transfer reaction(²³⁸U-4p-4n). The barium and radium fraction as BaCl₂ precipitate were radiochemically separated first from the mixture of uranium and reaction products. Then, the radium fraction was separated from BaCl₂ precipitate by using cation exchange technique. The γ-ray spectra of the Ra fraction were measured using an HPGe detector. The production cross sections of ²³⁰Ra were obtained by a combination of the radiochemical separation technique and off-line γ-ray spectroscopy. The cross section of ²³⁰Ra has been determined to be 66±20 μb.     

Production of Λ-hypernuclei in A(p,K+)ΛB reactions

The production of Λ-hypernuclei in the A(p, K⁺)_ΛB reaction is investigated in the framework of the distorted wave impulse approximation(DWIA). The total cross sections and differential cross sections for various nuclear targets are calculated with an elementary process pN→NKΛ where the additional contributions from the N^*(1535) resonance and the final state interaction between p and Λ are included. The dependence of the production cross sections of Λ-hypernuclei on the phenomenological nuclear density and the nucleon number in the target, as well as the distortion effect of the incident proton and outgoing kaon, are also explored. It is shown that the distortion effect tends to decrease the cross     

Shanghai laser electron gamma source and its applications

Shanghai Laser Electron Gamma Source, a high intensity beam line of γ-ray, is expected to generate γ-rays up to the maximum energy of 22 MeV by Compton backscattering between a CO₂ laser and electrons in the 3.5 GeV storage ring of the Shanghai Synchrotron Radiation Facility. The luminosity of SLEGS γ-ray beam is estimated to be 7×10⁷ A^－1W^－1s^－1 in a optimized setup. Indirect measurement of cross section of the key nuclear-astrophysics reaction ¹²C(α,γ)¹⁶O and γ-ray-triggered transmutation of long-lived radioactive wastes are discussed based on the estimated SLEGS γ-ray beam properties.     

Simulation of energy scan of pion interferometry in central Au+Au collisions at relativistic energies

We present a systematic analysis of two-pion interferometry for the central Au+Au collisions at √s_NN=3, 5, 7, 11, 17, 27, 39, 62, 130 and 200 GeV/c with the help of a multiphase transport (AMPT) model. Emission source-size radius parameters R_long, R_out, R_side and the chaotic parameter λ are extracted and compared with the experimental data. Transverse momentum and azimuthal angle dependencies of the HBT radii are also discussed for central Au+Au collisions at 200 GeV/c. The results show that the HBT radii in central collisions do not change much above 7 GeV/c. For central collisions at 200 GeV/c, the radii decrease with the increasing of transverse momentum p_T but are not sensitive to the azimuthal angle. These results provide a theoretical reference for the energy scan program of the RHIC-STAR experiment.     

Configuration of the valence neutrons of 17B

The reaction cross section of ¹⁷B on ¹²C target at (43.7±2.4)MeV/u has been measured at the Radioactive Ion Beam Line in Lanzhou (RIBLL). The root-mean-square matter radius (R_rms) was deduced to be (2.92±0.10)fm, while the R_rms of the core and the valence neutron distribution are 2.28fm and 5.98fm respectively. Assuming a ``core plus 2n' structure in ¹⁷B, the mixed configuration of (2s_1/2) and (1d_5/2) of the valence neutrons is studied and the     

Testing lepton flavor universality in terms of BESⅢ and charm-tau factory data

The recent measurements on R_K and R_π imply that there exists a possible violation of the leptonic flavor universality which is one of the cornerstones of the Standard Model. It is suggested that a mixing between sterile and active neutrinos might induce such a violation. In this work we consider the scenarios with one or two sterile neutrinos to explicitly realize the data while the constraints from the available experiments have been taken into account. Moreover, as indicated in literature, the deviation of the real PMNS matrix from the symmetric patterns may be due to a μ-τ asymmetry, therefore the measurements on R_D(Ds)eμ=Γ(D(D_s)→ e⁺ν_e)/Γ(D(D_s)→ μ⁺ν_μ) and R_D(Ds)μτ=Γ(D(D_s)→ μ⁺ν_μ)/Γ(D(D_s)→ τ⁺ν_τ) (and for some other heavy mesons B^± and B_c etc.) may shed more light on the physics responsible for the violation of the leptonic flavor universality. The data of BESⅢ are available to test the universality and that of future charm-tau factories will provide more accurate information. In this work, we will discuss R_D(Ds)eμ and R_D(Ds)μτ in detail and also briefly consider the cases for B^± and B_c.     

Calculation of astrophysical reaction rate of 82Ge(n,γ)83Ge

The neutron capture reaction on a neutron-rich near closed-shell nucleus ⁸²Ge may play an important role in the r-process following the fallout from nuclear statistical equilibrium in core-collapse supernovae. By carrying out a DWBA analysis for the experimental angular distribution of ⁸²Ge(d, p)⁸³Ge reaction we obtain the single particle spectroscopic factors, S_2,5/2 and S_0,1/2 for the ground and first excited states of ⁸³Ge=⁸²Ge⊙n, respectively. And then these spectroscopic factors are used to calculate the direct capture cross sections for the ⁸²Ge(n, γ)⁸³Ge reaction at energies of astrophysical interest. The optical potential for neutron scattering on unstable nucleus ⁸²Ge is not known experimentally. We employed a real folding potential which was calculated by using the proper ⁸²Ge density distribution and an effective nucleon-nucleon force DDM3Y. The neutron capture reactions on neutron-rich closed-shell nuclei are expected to be dominated by the direct capture to bound states. We will show that the direct capture rates on these nuclei are sensitive to the structure of the low-lying states.     

Measurement of intrinsic radioactive backgrounds from the 137Cs and U/Th chains in CsI(Tl) crystals

The inorganic CsI(Tl) crystal scintillator is a candidate anti-compton detector for the China Dark matter Experiment. Studying the intrinsic radiopurity of the CsI(Tl) crystal is an issue of major importance. The timing, energy and spatial correlations, as well as the capability of pulse shape discrimination provide powerful methods for the measurement of intrinsic radiopurities. The experimental design, detector performance and event-selection algorithms are described. A total of 359×3 kg-days data from three prototypes of CsI(Tl) crystals were taken at China Jinping Underground Laboratory (CJPL), which offers a good shielding environment. The contamination levels of internal isotopes from ¹³⁷Cs, ²³²Th and ²³⁸U series, as well as the upper bounds of ²³⁵U series are reported. Identification of the whole α peaks from U/Th decay chains and derivation of those corresponding quenching factors are achieved.     

Effects due to a Pu-C source on a HPGe detector and the corresponding neutron shielding

A gamma spectrum of a Pu-C source is measured using a p-type HPGe detector, whose three peaks (full energy, single-escape and double-escape peak) can be used as a calibration source for the beam energy measurement system of BEPCII. The effect of fast neutron damage on the energy resolution of the HPGe detector is studied, which indicates that the energy resolution begins to deteriorate when the detector is subject to 2×10⁷ n/cm² fastneutrons. The neutron damage mechanism and detector repair methods are reviewed. The Monte Carlo simulation technique is utilized to study the shielding of the HPGe detector from the fast neutron radiation damage, which is of great significance for the future commissioning of the beam energy measurement system.     

Searching for a neutral top-Higgs in association with top-quark pairs at an e~+e~- collider in the TC2 model

We investigate the associated production of the neutral top-Higgs h_t⁰ with a pair of top-quarks in the context of the topcolor-assisted technicolor (TC2) model at the future e⁺e^- Linear Colliders (LC) i.e. e⁺e^- → tt h_t⁰. We calculate the production rate and present the distributions of the transverse momenta of top-Higgs and top-quarks. The results show that the total cross section is typically of the order of 1.0-7.5 fb in the energy range between 1000 GeV and 2000 GeV of the LC for the whole top-Higgs mass region of interest. It should be distinctly possible that hundreds or even thousands of h_t⁰ signals can be produced per year at the LC given the luminosity L=500 fb^-1.     

Recent progress in AMS measurement of 182Hf at the CIAE

In order to improve the accuracy of accelerator mass spectrometry (AMS) measurement for ¹⁸²Hf/¹⁸⁰Hf, a series of measurements have been taken in the AMS laboratory at the China Institute of Atomic Energy (CIAE). The major ones include the instantaneous monitoring of ¹⁸⁰HfF₅^- current, testing the stability of transmission, the alternate measurements of an unknown sample and standard, and the origin identification and minimization of background ¹⁸²W. The experimental details and the improvement in the measurement accuracy, as well as some useful suggestions for better satisfying the requirements of certain practical applications, are presented in this paper.