2007 Vol. 31, No. 10
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The errors and correlations of BESIII TOF measurements are carefully checked in hit position at z partitions with the electron-pair events. The measured time-of-flight's and their covariance matrices are subjected to a correlation analysis algorithm which is developed for BESIII to combine the independent measurements with common errors. Monte Carlo studies show that the correlated analysis can provide more reliable TOF information on particle identification.
Based on the low-energy effective Hamiltonian with generalized QCD factorization, we calculate the new physics contributions to Bd0→φK*0 polarization anomaly and Bd→φKS CP asymmetry induced by the neutral Higgs bosons H0, h0 and A0 of the two Higgs doublet model Ⅲ. Within reasonable ranges of parameters, simultaneous solutions to the anomalies of the two processes give out 147<|λbsλss|<165. It will be really interesting in searching for the signs of new physics.
The 3-jet events are produced by Monte Carlo simulation Jetset7.4 in e+e－ collisions at s=91.2GeV. After introducing the cone angle of jets, we carefully studied the characters of the angular distributions of quark jets and gluon jets with different flavors. It turns out that the ranges of angular distributions of gluon jets are obviously wider than that of quark jets at the same energies. The average cone angles of gluon jets are much larger than that of quark jets for the same charged particle multiplicity or the same transverse momentum. There are linear relations in the distributions of the average cone angles of jets as functions of the charged multiplicity and the transverse momentum. The angular distribution properties of gluon jets produced by quarks with different flavors are the same, while there are obvious differences among the distributions of cone angles for quark jets of different flavors.
The second order self-energies of hadrons are calculated from S2 matrix, and then an effective method to solve nuclear many-body problems is summarized. In addition, the density-dependent relativistic many body methods are discussed.
By including the scalar isovector meson δ, we extend the relativistic mean field model and the one-boson exchange model of changing K-meson in the framework of Schaffner's relativistic mean field model. We re-consider the coupling constants for the interactions between the meson and the baryon and the interactions of the K meson with different mesons as well in various parameter sets. Using our model, we discuss the effective masses of K mesons in the hyperon-rich nuclear matter. We find that the density modification of the K meson mass in the strange nuclear matter is smaller than that in the pure nuclear matter. The influence of the scalar isovector meson δ on the effective mass of kaon is rather evident. But the extent of the influence is different in different parameter sets.
GEM, which has rapidly been developed in recent years as a new type of gas detector, has advantages of high position resolution and counting rate with a wide potential application in particle physics and X-ray imaging and etc. One of the key techniques of GEM's development is the structure fabrication of the PI film for the detector, which is difficult to be done by the lithography process. In this paper we present the structure fabrication process of GEM's PI film, and the result of our work about it. We chose wet-etching and dry-etching to make the structure holes of PI film, and find that wet-etching is better way to get perfect holes of GEM's PI film for future application with acceptable price. The successful fabrication of GEM's film structures is helpful to develop the domestic research of GEM detector. The performance of the GEM detector with such PI film still need more detail study.
The response of three semiconductor materials, polycrystalline HgI2, amorphous Se and polycrystalline CdTe, used for large area direct conversion detectors, is simulated by Monte Carlo method for X-ray photons in the diagnostic energy range (10—100keV). The simulation involves the transmission spectra, backscatting spectra, absorption efficiency and charge sensitivity. The interaction process between X-ray photons and the conversion materials is simulated by EGSnrc Monte Carlo code system and for the generation of signal charges Gaussian noise and the collection of partial charges are taken into account. The results show that deep traps in materials can affect largely detecting sensitivity when the mean free length (Schubweg) of carriers is less than the materials thickness. The sensitivity of HgI2 is 5 times higher than that of amorphous Se and CdTe is 10 times higher than amorphous Se, it can be seen that a high Z material can improve the detecting sensitivity greatly.
We have investigated the performance of a EXOGAM-Segmented-Clover with 16 segments as a Compton polarimeter to measure the linear polarization of gamma rays. The polarization sensitivity of the Clover detector has been measured at the energy of 1332keV through the coincidence measurements of cascade gamma-rays from 60Co. Experimental values were in good accord with our expectation.
The China Spallation Neutron Source (CSNS) accelerators consist of an 80MeV proton linac, and a 1.6GeV rapid cycling synchrotron. The ring accumulates 1.88×1013 protons via H－ stripping injection in the phase CSNS-Ⅰ. The injected beam is painted into a large transverse phase space to alleviate space-charge effects. The uniformity of the beam emittance after the injection is important in reducing the tune shift/spread due to the space-charge effects. The paper introduces three parameters to evaluate the uniformity of a beam distribution. To control emittance growth and reduce halo generation, different painting schemes have been compared by using the 3D simulation code ORBIT. The detailed studies on painting schemes and the dependence on the lattice tune, the injection peak current, and chopping rate are also presented.
Small-angle multiple intrabeam scattering (IBS) is an important effect for heavy-ion storage rings with electron cooling, because the cooling time is determined by the equilibrium between cooling and IBS process. All usually used numerical algorithms of IBS growth rate calculations are based on the model of the collisions proposed by A.Piwinski, but this result is a multidimensional integral. In this paper, the IBS growth rates are simulated for HIRFL-CSR using symmetric elliptic integral method, and compared with several available IBS code results.
The PKU-SCAF comprises three RF units: the 1.5cell injector which is developed all by ourselves, the upgraded 3.5cell injector, and the 1.3GHz 2×9cell Telsa style main accelerator. To take full advantage of the high quality electron beam of PKU-SCAF, we decide to compress the electron bunch out of 1.5cell injector for coherent THz and the bunch from main accelerator for FEL. For compressing the bunch, we design a chicane compressor with changeable parameter for PKU-SCAF which can serve for the two kinds of compression.
Resistive wall instability is a serious problem in many light sources. An active transverse feedback system (TFS) is required to operate the machine in a good condition when beam current is high. In order to investigate beam dynamics with TFS turned on, we developed a TFS simulation program. The feedback effectiveness for the Shanghai Synchrotron Radiation Facility (SSRF) storage ring is simulated under various conditions such as closed orbit distortion included, beam position monitor reading errors added, and finite-duration impulse-response filter strategy changed.
The design of LLRF control system for the 100MeV cyclotron has been presented together with the desktop experiment and its result. In the experiment, the feasibility of the digital control is validated for amplitude and phase close loop operation in driven mode. The preliminary test result and development procedure show that the digital version of LLRF control is suitable for the RF system of the 100MeV cyclotron.
A monolithic capillary half focusing X-ray lens (MCHFXRL) is used to focus the synchrotron radiation. The magnitudes of the focal spot size and gain of the synchrotron radiation microbeam focused by the MCHFXRL are in the orders of 10μm and 103, respectively. In the energy range from 5.5 to 11.5keV, the focal spot size varies from 38 to 29μm; the transmission efficiency varies from 26.1% to 20.5%; the translation of the vertical position of the focal spot is 3μm; the change of the output focal distance is 155μm. On the basis of the investigation of the performances of the MCHFXRL, the application of the synchrotron radiation microbeam in micro-extended-X-ray-absorption-fine-structure (micro-EXAFS) analysis is studied.
The content of Bacillus substilis var. niger (ATCC 9372) DNA double-strand breaks induced by neutron radiation at different doses and different dose rates respectively, was measured and quantified by pulsed-field gel electrophoresis. By the analyses of DNA release percentage (PR), DNA breakage level (L), average molecular weight of breakage DNA and DNA fragment distribution, the results showed that DNA fragments were obviously distributed into two regions in the different irradiation condition. This suggestes that there are some sensitive points to neutron radiation in the Bacillus substilis var. niger molecule. The DNA release percentage, DNA breakage level and the content of DNA fragments in different region varied regularly in some extent with change of the neutron radiation dose or dose rate.
The preparation and accelerator mass spectrometry (AMS) measurements of a series of 182Hf AMS calibration standards are described in this paper. The preparation consists of five processes, the synthesis of the initial 182Hf/180Hf standard sample by double neutron capture reaction of 180Hf, the accurate measurement of this standard for isotopic ratio with thermal ionization mass spectrometry (TIMS), the chemical separation of isobaric interference 182W, the sequential dilution of the initial standard, and the preparation of HfF4. The value of 182Hf/180Hf in the initial 182Hf/180Hf standard was obtained with TIMS to be (1.63±0.01)×10－6. Chemical separation and purification procedures were developed and applied in the preparation of all 182Hf/180Hf standards for the removal of major isobaric interference nuclide 182W. As a result, three 182Hf AMS standards with 182Hf/180Hf ratios of (1.63±0.01)×10－6, (3.22±0.26)×10－8, (3.45±0.32)×10－10 were obtained. AMS measurements of these standard samples were performed and good linearity was obtained in a plot of AMS results vs nominal values for 182Hf/180Hf ranging from 1.63×10－6 to 3.45×10－10.
Diffraction-enhanced X-ray imaging could extract accurately the refraction angles of the sample, which is very important to increase the image contrast of low Z samples. In this paper, the DEI experiments with X-rays of different energies were performed both on wedge-shaped and rounded model samples. Refraction angles of the two samples were all obtained accurately, and the results agreed well with the calculations. Quantitative analyses based on Edge Visibility were performed for the wedge-shaped model sample. The results revealed that the calculated positions for the Best Edge Visibility of the slope with fixed refraction angle were calculable in good agreement with the experimental results. A quantitative research on the Edge Visibility of real tissues sample was carried out and the optimal condition for best contrast of DEI images were discussed.
We study the global bipartite entanglement of the three-qubit Heisenberg XXX spin chain with impurity. Through calculating the negativities N1-23 and N12-3, we show that the critical temperature Tc above which the entanglement vanishes increases with the increase of the impurity parameter J1. For a given T, the corresponding critical impurity parameter J1c below which the entanglement vanishes increases with the increase of the magnetic field B, and by adjusting J1 and B one can control the values of N1-23 and N12-3. The maximum value of N12-3 decreases from 0.5 to 0.3727 as the temperature rises, but the one of N1-23 keeps the constant value of about 0.4714.
The recent theoretical and experimental progresses in hypernuclear physics are reviewed. According to the specifications of CSR in Lanzhou, the possible study of hypernuclear physics is suggested.
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