ηproduction in proton-nucleus collisions near threshold

The η-meson production in proton-nucleus(pA)collisions near threshold is studied within a relativistic meson-exchange model.The primary production amplitude is presented in the distorted-wave impulse approximation for the nucleus with isospin 0 or [1]by assuming that N*(1535)is excited via a meson exchange and then decays into η and nucleon pair(ηN).Taking 18O and 12C nuclei as examples,we evaluate the production cross sections as a function of the incident proton energy,and analyze the effects of nuclear medium and various meson-exchange contributions.Finally we discuss implications for further experimental studies at the Cooling Storage Ring(CSR)in Lanzhou.     

C(γ,η)X反应与N(1535)在核内的性质

在N^*(1535)共振模型下,研究了γ在原子核上产生η的反应,通过N衰变的实验数据以及γp→ηp反应确定了模型参数,结果表明,M_N*=1550MeV才较好地符合γp→ηp的实验,对¹²C上的η介子光生的总截面计算发现,N^*(1535)在核内的宽度由于多体修正而增大,N^*－核的相互作用具有排斥性质.     

在α(p,p')ηα反应中的N(1535)激发及η介子产生

在相对论介子与核相互作用理论框架下, 对α(p,p')ηα反应进行了理论分析, 讨论了在入射质子和靶核上的N^*(1535)激发机制的特点. 以⁴He靶核为例, 在入射质子动能T_p=2.8GeV的情况下, 计算了反应截面, 末态ηN不变质量谱和出射η介子的角分布, 讨论了在兰州重离子冷却储存环(CSR)上开展实验研究的意义和可能性.     

Energy dependence of non-linear dynamical features in e+e－ collisions

A study of the dynamical fluctuation properties at various c.m. energies in e⁺e^－ collisions is performed using the Monte Carlo method. The results suggest that, after the normalized factorial moments of 3-dimensional phase space are analyzed using an isotropical phase space partition, the NFM describing non-linear dynamical properties show a power-law scaling, i.e., the dynamical fluctuations in higher dimensional phase space are isotropic. For c.m. energies √s≤80 GeV, the scaling exponents φ_q increase rapidly with the c.m. energy and for c.m. energies √s>80GeV, the φ_q gradually saturate.     

Measuring D0-D0 mixing in D→f0(980) K and more

We investigate the D⁰-D⁰ mixing through the doubly Cabibbo suppressed (DCS) channel D0→f₀(980)K^*0 and its charge conjugate channel, in which the K^*0 meson is reconstructed in both K⁺π^－ and K_Sπ⁰ final state. Although the decay D⁰→f₀(980)K^* has a small branching ratio, the final state mesons are relatively easy to identify. The f₀(980) meson can be replaced by the S-wave π⁺π^－ state, or a longitudinally polarized vector meson ρ⁰. All mixing parameters, including the mass difference and decay width difference, can be extracted by studying the time-dependent decay width of these channels. We show that the method is valid in all regions for mixing parameters and it does not depend on the strong phase difference.     

Investigation of neutron induced reactions on ~(23)Na by using Talys 1.4

The neutron induced reactions on23 Na are investigated by using the Talys1.4 program. The calculated results for the23Na(n, 2n)22Na reaction are found to agree with the experimental results. The cross sections of the residues of the(n, n),(n, γ),(n, p), and(n, np) channels in the reactions are presented, and at the same time, the neutron induced reactions on22 Ne are also investigated.     

A note on the mass splitting of K(892)

Belle Collaboration reported a new observed value of K^*－(892) mass by studying τ^－→ K_Sπ－ν_τ decay, which is significantly different from the current world average value given by Particle Data Group 2006. Motivated by this new data, we revisit the issue on the K^*0(892)－K^*±(892) mass splitting. Our theoretical estimation favors the new measurement by Belle Collaboration. Therefore further experimental efforts are urgently needed to improve our understanding of these issues.     

Production of charmonium(like) states in e+e－ interactions

We present a search for new charmonium like states in e⁺e^－ annihilation using the initial-state radiation and the process e⁺e^－J/ψD^(*)D^(*). The analyses are based on a huge data sample recorded near the Υ(4s) resonance with the Belle detector at the KEKB e⁺e^－ asymmetric-energy collider.     

Excess 3H in the volcanic lakes: evidence for natural nuclear fusion

The excess ³H (tritium) have been observed in the volcanic lakes Nemrut (Turkey), Laacher (Germany) and Pavin (France). The ⁴He and ³He concentrations in Lakes Nemrut, Laacher, and Pavin were determined to be 25 and 190, 10 and 50, and 70 and 500 times larger than the atmospheric saturation value respectively. The isotopic ratio of the helium excess, ³He_ex/⁴He_ex, in Lakes Nemrut, Laacher and Pavin was (1.032±0.006)×10^－5, (7.42±0.03)×10^－6 and (9.09±0.01)×10^－6 respectively. The ³He/⁴He ratio of helium isotopes in the lake can help us to identify the origin of gas fluxes from the interior of the Earth. The ³He/⁴He ratios in the Lakes Nemrut, Laacher and Pavin clearly indicate that a large amount of helium isotopes were released to the lakes from mantle source. The excess ³H at the bottom of Lakes Nemrut, Laacher and Pavin have a good correlation with mantle ³He. We consider that the excess ³H might be also released from mantle source and both ³H and ³He might be produced by nuclear fusion (d-d reaction) in an environment rich in H atoms and (U+Th) at high temperature and high pressure condition in deep Earth.     

EC/β+ decay of six medium-heavy nuclei

Previous experimental results of (EC+β⁺) decay for the medium-heavy nuclei reported by our group since 1996, including ¹⁵³Er, ¹⁵⁷Yb, ²⁰⁹Fr, ¹²⁸Ce, ¹³⁰Ce, and ¹²⁸Pr have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion.     

O(α_sv~2) correction to J/ψ plus η_c production in e~+e~- annihilation at √s=10.6 GeV

Based on the nonrelativistic QCD factorization approach, O(α_sv2) corrections to J/ψ plus η_c production in m e⁺e^- annihilation at √s=10.6 ≥v are calculated in this work. The numerical results show that the correction at α_sv2 order is only about a few percent of the total theoretical result. This indicates that the perturbative expansions become convergent and that a higher order correction will be smaller. The uncertainties from the long-distance matrix elements, renormalization scale and the measurement in the experiment are also discussed. Our result is in agreement with the previous result by Jia.     

Measurement and analysis of the 238U(n, 2n) reactionrate in depleted uranium/polyethylene shells

In order to check the conceptual design of the subcritical blanket in a fusion-fission hybrid reactor, a depleted uranium/polyethylene simulation device with alternate shells has been established. The measurement of the ²³⁸U(n, 2n) reaction rate was carried out using an activation technique, by measuring the 208 keVγ rays emitted from ²³⁷U. The self-absorption of depleted uranium foils with different thicknesses was experimentally corrected. The distribution of the ²³⁸U(n, 2n) reaction rate at 90° to the incident D⁺ beam was obtained, with uncertainty between 5.3% and 6.0%. The experiment was analyzed using MCNP5 code with the ENDF/BVI library, and the calculated results are all about 5% higher than the measured results.     

Study of magnetic-rotation in ~(82)Rb by g-factor measurements

Magnetic rotation in ⁸²Rb has been investigated for the first time by g-factor measurement of intra-band states of the magnetic-rotational band built on the 11- state. The g-factors were measured by a TMF-IMPAD method and calculated by a semi-classical model of independent particle angular momentum coupling assumption. The g-factors and deduced shears angles decrease with the increasing of spin along the band, illustrating a step-by-step alignment of the valence protons and neutrons. The rapid alignment of the valence neutrons leads to a decrease of g-factors. The present results vividly reveal the shears mechanism of magnetic rotation.     

Developments in accelerator mass spectrometry (AMS) method for 182Hf

The present detection limit for ¹⁸²Hf at CIAE HI-13 AMS systems could not satisfy various applications (e. g. detection of a nearby supernovae signal). Therefore, techniques were developed in this work to improve the AMS measurement of ¹⁸²Hf mainly on building a new injector and using a method that based on solid-phase reaction for the preparation of HfF₄ samples from HfO₂. The experimental results show that mass resolution of the injector can reached 630, and the F^－/O－ and beam current of ¹⁸⁰HfF₅^－ for HfF₄ samples produced by dry method is about 2—3 times and 1.5 times of that by previously method, respectively.     

Structure change of 156Yb at high-spin states

High-spin states of ¹⁵⁶Yb have been studied via the ¹⁴⁴Sm(¹⁶O,4n)¹⁵⁶Yb fusion-evaporation reaction at beam energy 102~MeV. The positive-parity yrast band and negative-parity cascade have been extended up to higher-spin states, respectively. The characteristics of the negative-parity sequence above the 25^－ state may related to the excitation from the nucleon in the Z=64, N=82 core. The E-GOS curve for the positive-parity yrast sequence in ¹⁵⁶Yb indicate that this nucleus may undergo an evolution from quasivibrational to quasirotational structure with increasing angular momentum. The Cranked Woods-Saxon-Strutinsky calculations by means of Total-Routhian-Surface (TRS) methods has been made to understand this structure change.     

Search for exotic state 1－+ π1(1400) at BESⅢ

The J/ψ hadronic decays provide good laboratory to search for the hybrid states with exotic quantum numbers. A full Partial Wave Analysis (PWA) is performed to the generated Monte Carlo J/ψ→ρηπ data, based on the design of BESⅢ detector, to study the sensitivity of searching for a possible exotic state at BESⅢ.     

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.     

Prompt fission neutron spectra of n+235U above the (n,nf) fission threshold

Calculations of prompt fission neutron spectra (PFNS) from the ²³⁵U(n, f) reaction were performed with a semi-empirical method for E_n=7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of (n,xnf) pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of (n,xnf) fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the (n,nf) or (n,2nf) reactions influences the PFNS shape, and the neutron spectra of the (n,xnf) fission-channel are soft compared with the neutron spectra of the (n,f) fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case.     

AMS measurement of In-situ produced cosmogenic 10Be in Loess Quartz in Luochuan

Loess is the most important and the most typical continental classic sediments of Quaternary. So the measurement of In-situ produced cosmogenic ¹⁰Be is expected to be used for the Loess stratigraphic age. But the production rate of In-situ produced cosmogenic ¹⁰Be in Loess quartz is very low. It requires very high sensitivity and accuracy of measurement. This work has measured the concentrations of ¹⁰Be of two layers in Loess section of Luochuan including L8, L9 and the concentrations of ¹⁰Be in (of) blank sample with the HI-13 AMS system at China Insitute of Atomic Energy(CIAE), then calculated the content of ¹⁰Be in loess quartz for each layer. The ratio of ¹⁰Be/⁹Be was found in the range of 10^－13. The background of ¹⁰Be/⁹Be was about 3×10^－14.