2011 Vol. 35, No. 4

Particle and field theory
Evidence for further charmonium vector resonances
Eef van, George Rupp
2011, 35(4): 319-324. doi: 10.1088/1674-1137/35/4/001
We discuss the shape of threshold signals in production cross sections of the reaction e+e-→ D*D*, at the opening of the Ds*Ds* and Λc+Λc- channels. Furthermore, evidence for the ψ(3D), ψ(5S), ψ(4D), ψ(6S), ψ(5D), ψ(7S), ψ(6D), and ψ(8S) new charmonium vector resonances is presented, on the basis of data recently published by the BABAR Collaboration. Central masses and resonance widths are estimated. Confirmation of these resonances would be a huge step in lifting the precision level of hadron spectroscopy towards that of atomic spectroscopy, with far-reaching consequences for theory.
Earthquake forecast via neutrino tomography
WANG Bin, CHEN Ya-Zheng, LI Xue-Qian
2011, 35(4): 325-332. doi: 10.1088/1674-1137/35/4/002
We discuss the possibility of forecasting earthquakes by means of (anti)neutrino tomography. Antineutrinos emitted from reactors are used as a probe. As the antineutrinos traverse through a region prone to earthquakes, observable variations in the matter effect on the antineutrino oscillation would provide a tomography of the vicinity of the region. In this preliminary work, we adopt a simplified model for the geometrical profile and matter density in a fault zone. We calculate the survival probability of electron antineutrinos for cases without and with an anomalous accumulation of electrons which can be considered as a clear signal of the coming earthquake, at the geological region with a fault zone, and find that the variation may reach as much as 3% for νe emitted from a reactor. The case for a νe beam from a neutrino factory is also investigated, and it is noted that, because of the typically high energy associated with such neutrinos, the oscillation length is too large and the resultant variation is not practically observable. Our conclusion is that with the present reactor facilities and detection techniques, it is still a difficult task to make an earthquake forecast using such a scheme, though it seems to be possible from a theoretical point of view while ignoring some uncertainties. However, with the development of the geology, especially the knowledge about the fault zone, and with the improvement of the detection techniques, etc., there is hope that a medium-term earthquake forecast would be feasible.
Pair production of neutral Higgs bosons from the left-right twin Higgs model via γγ collisions
MA Wei, YUE Chong-Xing, ZHANG Ting-Ting
2011, 35(4): 333-338. doi: 10.1088/1674-1137/35/4/003
The left-right twin Higgs (LRTH) model predicts the existence of the neutral Higgs bosons (h, Φ0), which can be produced in pairs (Φ0Φ0, hh, Φ0h) via γγ collisions at the next generation e+e- International Linear Collider (ILC). Our numerical results show that the production cross section of the neutral Higgs boson pair Φ0Φ0 can reach 8.8 fb. The subprocess γγ→Φ0Φ0 might be used to test the LRTH model in future ILC experiments.
particle and nuclear astrophysics and cosmology
Radiation spectrum of rotating Gödel black hole and correction entropy
ZHANG Li-Chun, LIN Hai, LI Huai-Fan, ZHAO Ren
2011, 35(4): 339-343. doi: 10.1088/1674-1137/35/4/004
We study the Hawking radiation of the scalar field in the rotating Gödel black hole in minimal five-dimensional supergravity. We not only derive radiation spectra that satisfy the unitary principle but also obtain the correction term of Bekenstein-Hawking entropy. The conclusion will help us learn more about the rotating Gödel black hole in minimal five-dimensional supergravity. This provides a greater understanding of the thermal radiation of black holes.
Nuclear and ion Physics
Prompt neutron multiplicity distribution for 235U(n,f) at incident energies up to 20 MeV
CHEN Yong-Jing, LIU Ting-Jin
2011, 35(4): 344-348. doi: 10.1088/1674-1137/35/4/005
For the n+235U fission reaction, the total excitation energy partition of the fission fragments, the average neutron kinetic energy <ε>(A) and the total average energies Eγ(A) removed by γ rays as a function of fission fragment mass are given at incident energies up to 20 MeV. The prompt neutron multiplicity as a function of the fragment mass, ν(A), for neutron-induced fission of 235U at different incident neutron energies is calculated. The calculated results are checked with the total average prompt neutron multiplicities ν and compared with the experimental and evaluated data. Some prompt neutron and γ emission mechanisms are discussed.
Study of compound particle production in 84Kr-emulsion interactions at 1.7 A GeV
BAI Cai-Yan, ZHANG Dong-Hai
2011, 35(4): 349-354. doi: 10.1088/1674-1137/35/4/006
The characteristics of compound particle multiplicity distribution and multiplicity correlations between the compound particle and the grey particle, black particle, shower particle and heavily ionized track particle are investigated in this paper. It is found that the average multiplicities of the grey particle, black particle, shower particle and heavily ionized track particle increase with an increase in the number of compound particles, which can be explained by the impact geometrical model. The compound multiplicity distribution is observed to obey a Koba-Nielson-Olesen (KNO) type of scaling law.
Transverse mass distributions in central heavy-ion collisions at high energies
XIE Wen-Jie, YANG De, WANG Cui-Ping, WANG Zhi-Gang
2011, 35(4): 355-362. doi: 10.1088/1674-1137/35/4/007
The transverse mass spectra of protons, pions, kaons, Lambda and Antilambda produced in central nucleus-nucleus collisions at high energies are described by using one-temperature and two-temperature emission pictures. The calculated results are compared and found to be in good agreement with the experimental data of the E895, E866 and E917 Collaborations measured in central Au-Au collisions at the Alternating Gradient Synchrotron (AGS) energies and the NA49 Collaboration measured in central Pb-Pb collisions at the Super Proton Synchrotron (SPS) energies. It is demonstrated that the transverse mass distributions of protons, kaons, Lambda and Antilambda, except for Lambda hyperons produced in central Pb-Pb collisions at 158 A GeV, can be described by using the one-temperature emission picture, and for pions, we need to use the two-temperature emission picture.
Detection Technology and Methods
Study of the THGEM detector with a reflective CsI photocathode
LIU Hong-Bang, ZHENG Yang-Heng, XIE Yi-Gang, LV Jun-Guang, ZHOU Li, YU Bo-Xiang, ZHANG Ai-Wu, AN Zheng-Hua, XIE Yu-Guang, ZHANG Dong, ZHENG Zhi-Peng
2011, 35(4): 363-367. doi: 10.1088/1674-1137/35/4/008
The THGEM detector without and with a CsI has been tested successfully. The optimal parameters of THGEM have been determined from eight samples. The UV photoelectric effect of the CsI photocathode is observed. The changing tendency related to the extraction efficiency (εextr) versus the extraction electric field is measured, and several electric fields influencing the anode current are adjusted to adapt to the THGEM detector with a reflective CsI photocathode.
Two-dimensional photon counting imaging detector based on a Vernier position sensitive anode readout
YAN Qiu-Rong, ZHAO Bao-Sheng, LIU Yong-An, YANG Hao, SHENG Li-Zhi, WEI Yong-Lin
2011, 35(4): 368-373. doi: 10.1088/1674-1137/35/4/009
A two-dimensional photon counting imaging detector based on a Vernier position sensitive anode is reported. The decode principle and design of a two-dimensional Vernier anode are introduced in detail. A photon counting imaging system was built based on a Vernier anode. The image of very weak optical radiation can be reconstructed by image processing in a period of integration time. The resolution is superior to 100 μm according to the resolution test. The detector may realize the imaging of very weak particle flow of high-energy photons, electrons and ions, so it can be used for high-energy physics, deep space exploration, spectral measurement and bio-luminescence detection.
Design and performance analysis of a compact magnetic proton recoil spectrometer for DT neutrons
QI Jian-Min, ZHOU Lin, JIANG Shi-Lun
2011, 35(4): 374-380. doi: 10.1088/1674-1137/35/4/010
A magnetic proton recoil (MPR) spectrometer is a novel instrument with superior performance, including high energy resolution, high count rate and good signal-to-noise ratio (SNR) for measurements of neutron spectra from inertial confinement fusion (ICF) experiments and high power Tokomaks. In this work, the design of a compact MPR spectrometer (cMPR) was evaluated for deuteron-tritium (DT) neutron spectroscopy. The characteristics of the spectrometer were analyzed using 2-D beam transport simulations, 3-D particle transport calculations and Monte-Carlo simulations. Based on the theoretical results, an instrument design that satisfies special experimental requirements is proposed. The energy resolution and efficiency of the spectrometer are also evaluated. The results indicate that the proposed cMPR spectrometer would achieve a detection efficiency and energy resolution of approximately 10-8 and 4%, respectively, for DT neutrons.
Study of a compact external magnetic field radial split-cavity oscillator
ZHANG Yun-Jian, MA Qiao-Sheng, LUO Xiong
2011, 35(4): 381-386. doi: 10.1088/1674-1137/35/4/011
With the experiment result analyses of a coaxial virtual cathode oscillator (CVCO), a new kind of compact radial split cavity oscillator (RSCO) is presented in this paper. On the oscillator, a low resistance tube is formed by using the diode structure of a CVCO, and a radial split-cavity structure is formed by several meshes that cause the electronic beam to transmit. Calculating all kinds of parameter, at the input parameter 350 kV, 27 kA, the numerical simulation results show that the average output microwave power is about 4.0 GW, the microwave frequency is 1.37 GHz, and the electronic efficiency is 42.3%.
Heat load of a GaAs photocathode in an SRF electron gun
WANG Er-Dong, rg Kewisch, Ilan Ben-Zvi, Andrew Burrill, Trivini Rao, WU Qiong, Animesh Jain, Ramesh Gupta, Doug Holmes, ZHAO Kui
2011, 35(4): 387-391. doi: 10.1088/1674-1137/35/4/012
A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved by using a superconducting radio frequency (SRF) electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide (GaAs) photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder (plug) to decrease the heat load from GaAs.
Sm2Co17 magnet blocks for the in-vacuum undulators (IVU20) at the SSRF
HE Yong-Zhou, ZHOU Qiao-Gen, ZHANG Ji-Dong
2011, 35(4): 392-396. doi: 10.1088/1674-1137/35/4/013
The design and development status of Sm2Co17 magnet blocks for two in-vacuum undulators (IVU20) at the SSRF with the same hybrid design has been described. By the technological improvement of some processes and comparison with the experimental Sm2Co17 magnet blocks for the IVU25A, magnetic properties such as the intrinsic coercive force Hci and the average magnetic moment M are increased, the bend point magnetic field Hk value and pass rate are significantly increased, and the magnetic field uniformity of the magnet blocks are significantly improved. The basic developmental method of high uniformity Sm2Co17 magnet blocks for IVU20 is presented. The magnetic field qualities of the magnet blocks, including the magnetic property, the magnetic moment distribution, the magnetization deviation angle and the magnetic field uniformity, basically satisfy the specifications of the two IVU20 in-vacuum undulators.
Simulation of beam size multiknobs correction at the Accelerator Test Facility 2 at KEK
BAI Sha, GAO Jie
2011, 35(4): 397-401. doi: 10.1088/1674-1137/35/4/014
The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with a purpose of reaching a 37 nm vertical beam size at the interaction point (IP). During the initial commissioning, we started with larger-than-nominal β-functions at the IP in order to reduce the effects from higher-order optical aberrations and thereby simplifying the optical corrections needed. We report on the simulation studies at two different IP locations developed based on waist scan, dispersion, coupling and β function multiknobs correction in the large β optics of ATF2, in the presence of two kinds of magnet inaccuracies (quadrupole gradient and roll errors) to generate all possible linear optic distortions at the IP. A vertical beam size which is very close to the nominal beam size is obtained based on the simulation study.
Synchrotron radiation,applications of nuclear techniquees,etc
First X-ray fluorescence CT experimental results at the SSRF X-ray imaging beamline
DENG Biao, YANG Qun, XIE Hong-Lan, DU Guo-Hao, XIAO Ti-Qiao
2011, 35(4): 402-404. doi: 10.1088/1674-1137/35/4/015
X-ray fluorescence CT is a non-destructive technique for detecting elemental composition and distribution inside a specimen. In this paper, the first experimental results of X-ray fluorescence CT obtained at the SSRF X-ray imaging beamline (BL13W1) are described. The test samples were investigated and the 2D elemental image was reconstructed using a filtered back-projection algorithm. In the sample the element Cd was observed. Up to now, the X-ray fluorescence CT could be carried out at the SSRF X-ray imaging beamline.
Laser Compton scattering for a linearly polarized laser
LI Dong-Guo
2011, 35(4): 405-410. doi: 10.1088/1674-1137/35/4/016
Laser Compton light sources are potential candidates for the next generation of high-brightness X or γ-ray sources. When increasing the laser power to obtain intense X-ray laser, nonlinear Compton scattering happens. Nonlinear Compton scattering of linearly polarized laser beam is discussed in this paper. A complete transition probability formula is introduced and the polarization properties of final photons are discussed for different conditions.