2008 Vol. 32, No. 12
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We extend the T violating model of the paper on ``Hidden symmetry of the CKM and neutrino-mapping matrices" by assuming its T-violating phases χ↑ and χ↓ to be large and the same, with χ=χ↑=χ↓. In this case, the model has 9
real parameters: α↑, β↑, ξ↑, η↑ for the ↑-quark sector, α↑, β↑, ξ↑, η↑
for the ↓ sector and a common χ. We examine whether these nine parameters are compatible with ten observables: the six quark masses and the four real parameters that characterize the CKM matrix (i.e., the Jarlskog invariant J and three Eulerian angles). We find that this is possible only if the T violating phase χ is large, between -120° to -135°. In this strong T violating model, the smallness of the Jarlskog invariant J≌3×10-5 is mainly accounted for by the large heavy quark masses, with mcmt
We established a method on measuring the D0-D0 mixing parameter y for BESⅢ experiment at the BEPCⅡ e+e－ collider. In this method, the doubly tagged π(3770) →D0-D0 events, with one D decays to CP-eigenstates and the other D decays semileptonically, are used to reconstruct the signals. Since this analysis requires good e/π separation, a likelihood approach, which combines the dE/dx, time of flight and the electromagnetic shower detectors information, is used for particle identification. We estimate the sensitivity of the measurement of y to be 0.007 based on a 20fb-1 fully simulated MC sample.
An inbuilt compound target composed of carbon and tungsten is designed, and optimized by realistic GEANT4 Monte Carlo simulation. Also, we do a Monte Carlo study for single-pion photoproduction at the target. The results are presented from the simulation of pion yield, angular distribution and spectrum (at θlab, θcm=41°). These efforts are important to the coming measurement of the differential cross section for γ+N→π+N.
The elastic resonance scattering of 12C+p has been studied in inverse
kinematics via a novel thick target method at GIRAFFE facility of HI-13 tandem accelerator laboratory, Beijing. The recoil protons were measured by a ΔE-E counter telescope based on a large area double-sided silicon strip detector at laboratory angles around θ0=15°. The excitation function for 12C(p,p) elastic scattering has been obtained over a wide energy range of Ec.m.=0.31—3.45 MeV, which was explained quite well by the R-matrix calculation with known resonance parameters of the first three levels in 13N nucleus. Thus it is demonstrated that the present setup can be directly applied to the study of elastic resonance scattering with secondary radioactive beams.
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
sections by a factor of about 3—10. The production cross sections are sensitive to the adopted nuclear density.
The neutron-halo nuclei, 11Li, 14Be, and 17B, are studied in the three-body model. The Yukawa interaction is used to describe the interaction of the two-body subsystem. For given parameters of the two-body interaction, the properties of these neutron-halo nuclei are calculated with the Faddeev equations and the results are compared with those in the variational method. It is shown that the method of the Faddeev equations is more accurate. Then the dependencies of the two- and three-body energies on the parameters are studied. We find numerically that two- and three-body correlations differ greatly from each other with the variation of the intrinsic force range.
The centrality dependence of transverse momentum spectra for identified hadrons at midrapidity in Au+Au collisions at √sNN= 200GeV is systematically studied in a quark combination model. The pT spectra of π±, K±, p(p) and Λ(Λ) in different centrality bins and the nuclear modification factors (RCP) 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 pT spectra and the RCP for π0, Ks0 and Λ in Cu+Cu collisions at √sNN= 200GeV are well described. The results show that 〈β(r)〉 is only a function of the number of participants Npart and it is independent of the collision system.
A method for investigating the azimuthal correlations between directed and elliptic flow in heavy ion collisions is described. The transverse anisotropy of particle emission at AGS energies is investigated within the RQMD model. It is found that the azimuthal correlations between directed and elliptic flow are sensitive to the incident energy and impact parameter. The fluctuations in the
initial stage and dynamical evolution of heavy ion collisions are not negligible.
A solution is developed to improve the irradiation reliability of SOI NMOSFET (N-type Metal Oxide Semiconductor Field Effect Transistor). This solution, including SOI (Silicon On Insulator) wafer hardening and transistor structure hardening, protects the SOI circuit from total dose irradiation effect.
After examination of the designed high voltage power supply system of the BESⅢ drift chamber in the beam test of the full length prototype of drift chamber, a full system covering all the channels of high voltage was installed. The system's training and the high voltage value adjustment were carried out in the cosmic ray test of the BESⅢ drift chamber. The cosmic ray test for the full system and its final installation on the BESⅢ drift chamber were reported. The full system of high voltage power supply works stably and reliably.
The proposed beam energy measurement system at BEPCⅡ is composed
of three parts: the laser source and optics system, the laser-electron interaction system and the HPGe detector system. The working principles of each system are expounded together with the calculation for preliminary design. The normalizations of laser and electron beams are put forth and used for the evaluation of intensity of the backscattering photon. The simulation of HPGe detector is also performed for understanding the working properties.
Niobium is widely used in SRF (Superconducting Radio Frequency) cavities due to its excellent superconductivity and workability. With the continuous development of technology, higher demands of material are raised. One of the key issues is that RRR (Residual Resistance Ratio) of the Nb material should be more than 300, which requires that the Nb ingot have even higher RRR. This article introduces the development and the experimental results of high purity niobium in OTIC in Ningxia (Ningxia Orient Tantalum Industry Co. Ltd.), and the test results of the single cell TESLA (Tera Electron volt energy Superconducting Linear Accelerator) shaped cavity manufactured by Peking University using Nb material from OTIC.
Based on the femtosecond accelerator device, we are planning to build a broad band and tunable THz source using the Smith-Purcell radiation mechanism. Coherent Smith-Purcell radiation could be achieved owing to the super-short bunch produced in the device. To shorten the distance between the beam and grating, we use Transport to match the beta function producing a sheet beam on the grating surface. The optimization of grating length, groove depth and groove width are given in the paper. Then the radiation power for the shallow and deep grating using these parameters are presented. The detection devices and methods are also briefly discussed.
Aluminium and copper prototype cavities were designed to study higher order modes (HOM). An automatic field mapping system was developed with LabVIEW to measure the radiofrequency (RF) characteristics, such as resonant frequency, Q-value, shunt impedance and electromagnetic field distribution of the higher-order modes in a model RF cavity. Two kinds of the bell-shaped cavities were measured using the field mapping system, their frequencies are 1.5GHz and 800~MHz respectively. The fields' distributions of the monopole modes and dipole modes, as well the R/Q values, were measured.
In the last decade, X-ray fluorescence holography has been developed for the study of 3D atomic arrangements in solids. However, it encounters the twin image problem which may disturb the reconstructed atomic images. In this paper, the formation of twin image is discussed and we propose a modified two-energy algorithm to remove the twin image. The simulation shows that the method is valid and more efficient than the multiple-energy algorithm proposed by Barton.
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