2010 Vol. 34, No. 10

Deviations of the lepton mapping matrix from the Harrison-Perkins-Scott form
2010, 34(10): 1547-1555. doi: 10.1088/1674-1137/34/10/001

We propose a simple set of hypotheses governing the deviations of the leptonic mapping matrix from the Harrison-Perkins-Scott (HPS) form. These deviations are supposed to arise entirely from a perturbation of the mass matrix in the charged lepton sector. The perturbing matrix is assumed to be purely imaginary (thus maximally T-violating) and to have a strength in energy scale no greater (but perhaps smaller) than the muon mass. As we shall show, it then follows that the absolute value of the mapping matrix elements pertaining to the tau lepton deviate by no more than O((mμ/mτ)2)≈3.5×10-3 from
their HPS values.

Assuming that (mμ/mτ)2 can be neglected, we derive two simple constraints on the four parameters θ12, θ23, θ31, and δ of the mapping matrix. These constraints are independent of the details of the imaginary T-violating perturbation of the charged lepton mass matrix. We also show that the e and μ parts of the mapping matrix have a definite form governed by two parameters α and β; any deviation of order mμ/mτ can be accommodated by adjusting these two parameters.

Particle and field theory
Drinfeld-Manin instanton and its noncommutative generalization
2010, 34(10): 1556-1564. doi: 10.1088/1674-1137/34/10/002

The Drinfeld-Manin construction of U(N) instanton is reformulated in the ADHM formulism, which gives explicit general solutions of the ADHM constraints for U(N) (N≥2k-1) k-instantons. For the N<2k-1 case, implicit results are given systematically as further constraints. We find that this formulism can easily be generalized to the noncommutative case, where the explicit solutions are also obtained.

LHT model and Higgs boson production in association with a weak gauge boson at the LHC
LIU Wei, YUE Chong-Xing, SU Xue-Song, WANG Yong-Zhi
2010, 34(10): 1565-1569. doi: 10.1088/1674-1137/34/10/003

Considering the process pp→VH+X(V=W or Z) is a significant channel for searching for a light Higgs boson, we calculate the contributions of the littlest Higgs model with T-parity (called LHT model) to its production cross section. We find that, in most of the parameter space, the value of the relative correction parameter R is very small. However, with reasonable values of the free parameters, its value can be significantly larger.

Radiative leptonic decay Bc→τντγ in the standard model and the two-Higgs-doublet model
XIE Zhen-Xing, FENG Guan-Qiu, GUO Xin-Heng
2010, 34(10): 1570-1575. doi: 10.1088/1674-1137/34/10/004

We analyze the radiative leptonic Bc decay Bc→τντγ in the Standard Model and the two-Higgs-doublet model using the non-relativistic constituent quark model. The results confirm that this channel is experimentally promising in view of the large number of Bc mesons which are expected to be produced at future hadron facilities. We also find that this decay is sensitive to the parameters of the two-Higgs-doublet model, and it can be tested in future experiments.

On analytic formulas of Feynman propagators in position space
ZHANG Hong-Hao, FENG Kai-Xi, QIU Si-Wei, ZHAO An, LI Xue-Song
2010, 34(10): 1576-1582. doi: 10.1088/1674-1137/34/10/005

We correct an inaccurate result of previous work on the Feynman propagator in position space of a free Dirac field in (3+1)-dimensional spacetime; we derive the generalized analytic formulas of both the scalar Feynman propagator and the spinor Feynman propagator in position space in arbitrary (D+1)-dimensional spacetime; and we further find a recurrence relation among the spinor Feynman propagator in (D+1)-dimensional spacetime and the scalar Feynman propagators in (D+1)-, (D-1)- and (D+3)-dimensional spacetimes.

Controlling of entanglement sudden death induced by Dzyaloshinskii-Moriya interaction
ZHENG Qiang, SUN Ping, ZHANG Xiao-Ping, REN Zhong-Zhou
2010, 34(10): 1583-1586. doi: 10.1088/1674-1137/34/10/006

We investigate the entanglement dynamics of a system composed of two non-interacting qubits, A and B. A third qubit, C, only has the Dzyaloshinskii-Moriya (DM) spin-orbit interaction with qubit B. We find that the DM interaction can induce the entanglement sudden death (ESD) of the system qubits A and B, and properly mixing the initial state of the system and adjusting the state of qubit C are two effective methods of controlling ESD.

particle and nuclear astrophysics and cosmology
On the moment of inertia of a proto neutron star
ZHAO Xian-Feng, ZHANG Hua, JIA Huan-Yu
2010, 34(10): 1587-1592. doi: 10.1088/1674-1137/34/10/007

The influences of σ* and Φ mesons, temperature and coupling constants of nucleons on the moment of inertia of the proto neutron star (PNS) are examined in the framework of relativistic mean field theory for the baryon octet {n, p, Λ, Σ, Σ0, Σ+, Ξ, Ξ0} system. It is found that, compared with that without considering σ* and Φ mesons, the moment of inertia decreases. It is also found that the higher the temperature, the larger the incompressibility and symmetry energy coefficient, and the larger the moment of inertia of a PNS. The influence of temperature and coupling constants of the nucleons on the moment of inertia of a PNS is larger than that of the σ* and Φ mesons.

Nuclear and ion Physics
Centrality of the collision and random matrix theory
Z. Wazir
2010, 34(10): 1593-1597. doi: 10.1088/1674-1137/34/10/008

I discuss the results from a study of the central 12CC collisions at 4.2 A GeV/c. The data have been analyzed using a new method based on the Random Matrix Theory. The simulation data coming from the Ultra Relativistic Quantum Molecular Dynamics code were used in the analyses. I found that the behavior of the nearest neighbor spacing distribution for the protons, neutrons and neutral pions depends critically on the multiplicity of secondary particles for simulated data. I conclude that the obtained results offer the possibility of fixing the centrality using the critical values of the multiplicity.

Structure evolution along the yrast-line in 101Pd
ZHOU Hou-Bing, ZHOU Xiao-Hong, ZHANG Yu-Hu, Oshima M, Toh Y, Koizumi M, Osa A, Hatsukawa Y
2010, 34(10): 1598-1601. doi: 10.1088/1674-1137/34/10/009

High-spin states in 101Pd have been investigated experimentally via the 76Ge(28Si, 3nγ)101Pd reaction. The previously known bands based on the d5/2 and h11/2 neutron orbitals have been extended to higher-spin states, and two new structures have been observed. Spin and parity were assigned to the levels on the basis of the experimental results of the angular distribution of γ rays deexciting the oriented states. For the ground-state band, the E-GOS (E-Gamma Over Spin) curve strongly suggests a structure transition from vibration to rotation while increasing spin.

Effects of the entrance channel mass asymmetry in fusion reactions
BIAN Bao-An, ZHANG Feng-Shou
2010, 34(10): 1602-1608. doi: 10.1088/1674-1137/34/10/010

The symmetric and asymmetric fusion reaction systems forming the same compound nuclei 26Al, 30Si, 38Ar and 170Hf are investigated with the frame of improved isospin dependent quantum molecular dynamics model. The entrance channel mass asymmetry dependence of compound nucleus formation is found by analyzing the shell correction energies, the Coulomb barriers and the fusion cross sections. The calculated fusion cross sections agree quantitatively with the experimental data. The results indicate that compound nucleus formation is favorable for the systems with larger mass asymmetry because of the smaller Coulomb contribution to the fusion barrier.

Production cross sections of the superheavy nucleus 117 based on the dinuclear system model
ZHAO Wei-Juan, ZHANG Yong-Qi, WANG Hua-Lei, SONG Li-Tao, LI Lu-Lu
2010, 34(10): 1609-1614. doi: 10.1088/1674-1137/34/10/011

Within the framework of the dinuclear system model, the capture of two colliding nuclei, and the formation and de-excitation process of a compound nucleus are described by using an empirical coupled channel model, solving the master equation numerically and the statistical evaporation model, respectively. In the process of heavy-ion capture and fusion to synthesize superheavy nuclei, the barrier distribution function is introduced and averaging collision orientations are considered. Based on this model, the production cross sections of the cold fusion system 76—82Se+209Bi and the hot fusion systems 55Mn+238U, 51V+244Pu, 59Co+232Th, 48Ca+247—249Bk and 45Sc+246—248Cm are calculated. The isotopic dependence of the largest production cross sections is analyzed briefly, and the optimal projectile-target combination and excitation energy of the 1n-4n evaporation channels are proposed. It is shown that the hot fusion systems 48Ca+247—249Bk in the 3n evaporation channels and 45Sc+248Cm in the 2n-4n channels are optimal for synthesizing the superheavy element 117.

Influence of octupole deformation and orientation on the potential energy surface in the di-nuclear system model
WANG Nan, ZHOU Shan-Gui, ZHAO En-Guang
2010, 34(10): 1615-1621. doi: 10.1088/1674-1137/34/10/012

The nuclear and Coulomb potentials between deformed nuclei with octupole deformations and arbitrary orientations are evaluated numerically. The effects of the octupole deformation on the potential between nuclei and the potential energy surface (PES) used in the description of the production of super-heavy nuclei (SHN) by heavy-ion fusion reactions are investigated in the di-nuclear system model. It is found that the nuclear octupole deformation significantly changes the shape of the PES, which may influence the fusion probability of the SHN. Also, PESs in the tip-belly and belly-belly cases are investigated. Finally, the quasi-fission barriers in the tip-tip and belly-belly cases are evaluated. It is found that the quasi-fission barriers of the belly-belly case are generally larger than those of the tip-tip case.

Radius studies of 8Li and 8B using the optical-limit Glauber model in conjunction with relativistic mean-field theory
FAN Guang-Wei, XU Wang, PAN Qiang-Yan, CAI Xiao-Lu, FAN Gong-Tao, LI Yong-Jiang, LUO Wen, XU Ben-Ji, YAN Zhe, YANG Li-Feng
2010, 34(10): 1622-1627. doi: 10.1088/1674-1137/34/10/013

We study the reaction cross sections (σR) and root-mean-square (RMS) radii of 8Li and 8B, the halo-like nuclei, with stable target 12C, 27Al and 9Be within the standard optical-limit Glauber model, using densities obtained from relativistic mean-field (RMF) formalisms and other types of distributions. It is found that the experimental σR can be reproduced well at high energy. The RMS radius and Δr extracted by RMF-theory and harmonic oscillator distribution are compared. We find that the RMS radius and Δr of 8B are larger than those of 8Li. In addition, we analyze in detail the relationship between σR and density distribution.

Detection Technology and Methods
An electrostatic deflector for a fusion reaction
ZHANG Huan-Qiao, LIN Cheng-Jian, YANG Feng, JIA Hui-Ming, ZHOU Ping, AN Guang-Peng, ZHANG Chun-Lei, XU Xin-Xing
2010, 34(10): 1628-1631. doi: 10.1088/1674-1137/34/10/014

An electrostatic deflector for separating the fusion evaporation residues from the beam-like products in heavy ion reactions was installed. The evaporation residue separation and identification with the electrostatic deflector setup was tested with the reaction 32S+96Zr at several energies. The fusion evaporation residues and the beam-like particles were well separated after the electrical separation and the experimental fusion cross section obtained from the angular distribution is in good agreement with the calculated value well above the Coulomb barrier. This confirms the reliability of the setup.

Photon discrimination simulation with the PCA method
ZHOU Jing, LIU Zhi-Yi, MENG Qiu-Ying, ZHOU Shu-Hua
2010, 34(10): 1632-1635. doi: 10.1088/1674-1137/34/10/015
The shower shape of n, n, p, p, K+, π+ and photons, generated by JPCIAE code for 5.5 TeV/A 208Pb+208Pb collisions, incident on the ALICE photon spectrometer (PHOS), is analyzed with the principal component analysis (PCA) method. The efficiency dependence of purity for the photon discrimination is simulated for the deposited energy ranges 0.5—2 GeV, 2—10 GeV, 10—50 GeV and 50—100 GeV. The result shows that in the energy range of 0.5 to 100 GeV, the efficiency of the photon identification can reach 90% with purity of 90%.
Study of bulk micromegas detector
FAN Rui-Rui, HOU Feng-Jie, OUYANG Qun, CHEN Yuan-Bo, YI Fu-Ting, XIE Yi-Gang, DONG Jing
2010, 34(10): 1636-1638. doi: 10.1088/1674-1137/34/10/016

In this paper, we present a study of a micromegas detector prototype built with bulk technology. Following a short discussion of the micromegas detector's structure and working mechanism, the bulk fabrication process is described, and some testing results of the prototype are presented.

Design optimization of the APF DTL in the SSC-linac
WANG Zhi-Jun, HE Yuan, WU Wei, YANG Ya-Qing, XIAO Chen
2010, 34(10): 1639-1642. doi: 10.1088/1674-1137/34/10/017

A linear accelerator as a new injector for the SSC (Separated Sector Cyclotron) of the HIRFL (Heavy Ion Research Facility Lanzhou) is being designed. The DTL (Drift-Tube-Linac) has been designed to accelerate 238U34+ from 0.140 MeV/u to 0.97 MeV/u. To the first accelerating tank which accelerates 238U34+ to 0.54 MeV/u, the approach of Alternating-Phase-Focusing (APF) is applied. The phase array is obtained by coupling optimization software Dakota and beam optics code LINREV. With the hybrid of Multi-objective Genetic Algorithm (MOGA) and a pattern search method, an optimum array of asynchronous phases is determined. The final growth, both transversely and longitudinally, can meet the design requirements. In this paper, the deign optimization of the APF DTL is presented.

Studies of dual-harmonic acceleration at CSNS-Ⅱ
CHEN Jin-Fang, TANG Jing-Yu
2010, 34(10): 1643-1648. doi: 10.1088/1674-1137/34/10/018

The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) complex is designed to provide 1.56×1013 protons per pulse (ppp) during the initial stage, and it is upgradeable to 3.12×1013 ppp during the second stage and 6.24×1013 ppp during the ultimate stage. The high beam intensity in the RCS requires alleviation of space charge effects to reduce beam losses, which is key in such high beam power accelerators. With higher intensities in the upgrading phases, a dual-harmonic RF system is planned to produce flat-topped bunches that are useful to reduce the space charge effects. We have studied different schemes to apply the dual-harmonic acceleration in CSNS-Ⅱ, and have calculated the main parameters of the RF systems, which are presented in this paper.

A proposed method to characterize high harmonic microbunching in EEHG operation of SDUV-FEL

DENG Hai-Xiao

2010, 34(10): 1649-1654. doi: 10.1088/1674-1137/34/10/019

The echo-enabled harmonic generation (EEHG) scheme offers remarkable efficiency for generating high harmonic microbunching with a relatively small energy modulation. A proof of principle experiment of the EEHG scheme has been proposed at the Shanghai deep ultraviolet (SDUV) free electron laser (FEL) facility, where the 4th harmonic of the seed laser is amplified in the 9~m long radiator. To explore the advantages of the EEHG scheme, in this paper, a method of measuring the coherent high harmonic radiation of the radiator is proposed to investigate the electron beam microbunching corresponding to the 10th—20th harmonics of the seed laser. The principle of the proposed method, comparisons with existing methods and the simulation results are presented and discussed.

Design and simulation of a wire scanner for the CSNS linac
RUAN Yu-Fang, HAN Lu-Xiang, LIU Hua-Chang, ZHANG Hua-Shun, XU Tao-Guang, FU Shi-Nian
2010, 34(10): 1655-1660. doi: 10.1088/1674-1137/34/10/020

In this paper, we report the design and simulation of a wire scanner for the linac of the CSNS (China Spallation Neutron Source). The wire scanner is used to measure the transverse beam profile and the emittance. The effect of beam energy change upon the mechanical design of the wire scanner must be considered. The simulation results of heat on the two specified wires, tungsten and carbon, by using the finite element method software, ANSYS, are presented. In addition, the effect of wire deformation on the beam profile measurement is qualitatively analyzed, and the signal level of the wire scanner is discussed.

BEPCⅡ wire scanner system
SUI Yan-Feng, WANG Lin, ZHAO Ying, YUE Jun-Hui, LI Xiao-Ping, CAO Jian-She, MA Li
2010, 34(10): 1661-1664. doi: 10.1088/1674-1137/34/10/021

To monitor the beam profile at the end of the linac non-destructively, a wire scanner as a new diagnostic instrument was designed, manufactured and installed in 2007. Since then, several measurements have been carried out using this device. This paper describes the whole system of the wire scanner and the testing results.

Synchrotron radiation,applications of nuclear techniquees,etc
A new method to determine the projected coordinate origin of a cone-beam CT system using elliptical projection
YANG Min, JIN Xu-Ling, LI Bao-Lei
2010, 34(10): 1665-1670. doi: 10.1088/1674-1137/34/10/022

In order to determine the projected coordinate origin in the cone-beam CT scanning system with respect to the Feldkamp-Davis-Kress (FDK) algorithm, we propose a simple yet feasible method to accurately measure the projected coordinate origin. This method was established on the basis of the theory that the projection of a spherical object in the cone-beam field is an ellipse. We first utilized image processing and the least square estimation method to get each major axis of the elliptical Digital Radiography (DR) projections of a group of spherical objects. Then we determined the intersection point of the group of major axis by solving an over-determined equation set that was composed by the major axis equations of all the elliptical projections. Based on the experimental results, this new method was proved to be easy to implement in practical scanning systems with high accuracy and anti-noise capability.