2006 Vol. 30, No. 07
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We explore the consequences of assuming a simple 3-parameter form, first without T-violation, for the neutrino mass matrix M in the basis νe,νμ,ντ with a new symmetry. This matrix determines the three neutrino masses m1,m2,m3, as well as the mapping matrix U that diagonalizes M. Since U, without T-violation, yields three measurable parameters s12, s23, s13, our form expresses six measurable quantities in terms of three parameters, with results in agreement with the experimental data. More precise measurements can give stringent tests of the model as well as determining the values of its three parameters. An extension incorporating T-violation is also discussed.
Using the branching fractions of J/ψ to baryon-antibaryon decays, listed in PDG2004, we analyze the SU(3) flavor symmetry of the baryon octets and study the interference effects between the electromagnetic and strong interactions. The effects of SU(3) breaking are obtained by fitting the branching fractions of J/ψ→BB.
A new kind of even and odd nonlinear coherent state are defined. Using the numerical method, the statistical phase properties of a new kind of even and odd nonlinear coherent state are studied. It is shown that their phase properties are very different from those of usual even and odd coherent.
This paper studies deeply trigger decision criterion of the PHOS in ALICE experiment by simulation, including three parts: 1) the energy reconstruction performance of PHOS is tested; 2) the selection of trigger threshold is analyzed and the trigger efficiency is calculated; 3) the trigger rate of PHOS is evaluated and its selection is discussed for the different collision mode.
Excitation functions of the reaction products B,C,N,O,F and Ne emitted from the dissipative reaction of 19F+27Al have been measured at incident energies from 110.25MeV to 118.75MeV in steps of 250keV. The moments of inertia of the intermediate dinuclear system formed in the reaction are extracted from the energy autocorrelation functions of the products. Comparing the moment of inertia extracted from the experimental data with the calculated one by using the sticking limit, it indicates that the formed dinuclear system has a large deformation in the reaction process.
In the framework of relativistic mean-field theory, the strength of the pairing force is systematically studied for several isotope chains of rare-earth nuclei. It is shown, for the first time, that the pairing strength of the neutron, Gn, increases dramatically around the magic number N=82, while for the proton it is strongly related to the odd-even difference of the neutron number. The results indicate a strong correlation between the shell structure and the pairing force strength.
We study the properties of nuclear matter and finite nuclei in terms of the quark-meson coupling model with a density-dependent bag constant, which is extracted from the SU(3) Nambu-Jona-Lasinio(NJL) model. It is shown that this model provides a reasonable description for nuclear matter and finite nuclei. The rearrangement potential due to density-dependent bag constant plays an important role in this model.
A Total Routhian Surface(TRS) calculation are performed for studying triaxial superdeformation in the 168Hf nuclei. The equilibrium deformation parameters are given. The shell and pairing correction energies are considered respectively, the formation mechanism of triaxial superdeformation is investigated. The large deformation is due to the neutron shell correction energy and high j intruder orbital πi13/2.
In this paper, by means of the nuclear parton distribution obtained from the DGLAP equation, taking into account the energy loss of the beam proton through the nucleus, we analyze the QCD corrections to the measured Drell-Yan production cross sections for an 800GeV proton beam incident on Be, Fe and W nuclear targets in the Glauber model. For the nuclear parton distribution being extracted from the leading order, the results show that the QCD corrections can't improve the theoretical results fitting to the experimental data, especially in the cross section ratio of p-W to p-Be verse x1. Then we calculate the Drell-Yan cross sections using the shadowing effect, which is extracted from the next-to-leading order by Frankfurt et al., and find that direct photon production should be sensitive to energy loss in Compton scattering and annihilation process.
Non-central Au+Au collisions at sNN=200GeV are studied with the RQMD model. The dependence of elliptic flow on freezeout radius of final particles is analized. We find that elliptic flow increases with freezeout radius firstly,and then decreases, with a maximum value at the original size of the surface. The results show the different evolution of pressure gradient in different direction. The method to analyze the pressure gradient with mean radial velocity is used.
Based on our previous work, leading particle effects in nucleus-nucleus collisions at the Alternating Gradient Synchrotron (AGS) and Relativistic Heavy Ion Collider (RHIC) energies are uniformly analyzed by using the two-cylinder model. The results show that the differences in the (pseudo)rapidity distributions of the charged particles in nucleus-nucleus collisions with different centralities are mainly affected by the contributions of leading particles. If the contribution of leading particles is neglected, the charged particle (pseudo)rapidity distributions in nucleus-nucleus collisions with different centralities would have the same shape.
Based on a transport model IBUU04, the double n/p ratio is studied. It is found that the double n/p ratio has almost the same sensitivity to the density dependence of nuclear symmetry energy as the single n/p ratio does. Because the double n/p ratio of nucleon emissions taken from two reaction systems can reduce systemic errors effectively, it is thus more useful for constraining the density-dependent symmetry energy further.
This paper gives a study of non-binary discontinuity wavelet, put forward the theory and method of constituting basic wavelet functions, and has constituted concretely a wavelet function using λ=3.4 as an example. It also conducts a theoretical inference on the decomposition algorithm and reconstruction algorithm of non-binary wavelet, and gives a concrete study of the change of matrix in connection with λ=3.4. In the end, it shows the future of application of the result to the study of high energy collision.
Proton-proton collisions at s=22GeV and 200GeV have been simulated by PYTHIA model. The fixed-to-arbitrary and neighboring bin correlation patterns at these two colliding energies are investigated. It has been found that the neighboring bin correlations are the strongest at the central rapidity region and become weaker and weaker toward the two side rapidity regions; while the fixed-to-arbitrary bin correlations vary from one fixed bin to another.
From the test results of 33 Multi-gap Resistive Plate Chamber (MRPC) modules, we studied the correlation between the average signal amplitude and the time resolution. The average amplitude depends on the gas multiplication operation mode which determines the time resolution. The fluctuation of time resolution measurements with the number of events collected by the chambers is also discussed. This analysis will help to set the control limits to select the chambers with required time resolution in mass production.
A position-sensitive MRPC prototype with high time resolution was developed. This MRPC has 10×220μm gaps with the active area of 20cm×20cm. A front-end electronics based on NINO ASIC was used. The NINO ASIC can transform the input charge to the width of output signal for the Time-Over-Threshold (TOT) measurement by using High Performance TDC (HPTDC). With the difference of transmit time and distribution of plus amplitude, we can get the two-dimension position information. The beam test result shows a spatial resolution of 4.5mm along the readout pads and 1.6mm perpendicular to the readout pads, espectively. The time resolution is about 63ps and the detection efficiency is over 95%.
There exists strong left-right asymmetry of the X-T relation in the boundary cell of the BESⅢ drift chamber. The simulation indicates that this kind of asymmetry can be reduced by applying compensation voltage on the boundary field layer, which is confirmed in a beam test for a prototype chamber. The impact of the compensation voltage of the boundary cell on the spacial resolution and the dE/dx measurement is reported in this paper.
An improved kinematic fit method is developed for analyzing all-photon events, where the interaction point is unknown. The fitting algorithm is checked with Monte Carlo samples to ensure that the fitting program works properly. This is applied to the Monte Carlo simulated ψ(2S) decays. A higher efficiency is achieved. This method can be generally applied to analyzing all-photon events at electron-positron collider.
An approach for the production of intense (～108ions/s) radioactive ion beams, which differs from the standard ISOL (Isotope Separation On-Line) technique, has been demonstrated successfully using 11C at the TRIUMF laboratory of Canada. By using this approach, the low energy (13MeV) protons can be utilized to produce a range of radioisotopes of interest to the nuclear astrophysics research programs.
The relation between the input impedance and the characteristic parameters of a cavity, such as the resonance frequency, shunt impedance and the quality factor, has been obtained based on the equivalent circuit of the cavity and the coupling system. Using the matching condition, the ratio of coupling capacitance to the equivalent capacitance of the cavity can be acquired as a function of the characteristic parameters of the cavity, the value of the coupling capacitance can be obtained with a help of a numerical simulation and the perturbation theory, and then the perfect matching between the cavity and the transmission line can be procured. The application of these results on a model cavity is presented too.
The admittance equivalence is structured to analyze the beam-cavity interaction. Compared to the traditional process based on impedance plane, the admittance method is concise, and the expressions are obtained with intuitive physical quantity. By use of these expressions, the injecting transient effect under heavy beam loading, such as the case of HLS is discussed.
The high power RF transmitter and the circulator with 500MHz/250kW which will be operated in Beijing Electron-Positron Collider Upgrade (BEPCⅡ) project have been installed on site, and adjustments and acceptance test have been finished, which is the first transmitter system of 500MHz/250kW in China. In this paper, the test principle and all measurements as well as commissioning result in the acceptance test are introduced in details, and the actual machine technical parameters and performance are presented. An acceptance test conclusion by comparing with the design requirements is given.
Shanghai Synchrotron Radiation Facility (SSRF) is a 3rd generation synchrotron light source which is now under construction. The design emittance of the beam is 3.9nm•rad at the energy of 3.5GeV. Touschek lifetime is the dominant beam lifetime in SSRF for such a small beam emittance. The Touschek lifetime is the function of the energy acceptance of the storage ring. The energy acceptance is not only dependent on the RF voltage, but also restricted by the small physical or dynamic apertures, which makes the calculation complicated. In this paper the energy acceptances along the storage ring are calculated by the 6D tracking method based on the program Accelerator Toolbox (AT). Using those energy acceptance data, we can give a more close evaluation of the Touschek lifetime for different kind of conditions which we are interested in.
Equivalent circuit model is used to calculate field distribution of a coupled cavity chain. An RF cavity can be represented as a resonant LC circuit and the coupler as an idealized transformer. By solving the equations of the circuit model and simulating each cavity shape, the field distribution of the entire cavity chain is calculated. This method is very useful in particle dynamics simulation and accelerator geometry design. Calculation result and experimental measurement of a 16MeV BTW(backward traveling wave) linac is presented.
A (CF2)n-PIN sandwiched detecting array with statistics enhancement in low pulsed γ flux measurements has been constructed. The array uses 2mm thick (CF2)n overlaid with Si-PIN detector of φ60mm×1000μm, then coupled to PA101 amplifier with gain 100. The array exhibits four distinct properties: (1) very high detecting efficiency: The γ detecting sensitivity of the array can reach 10－11C.cm2, which is 4 orders of magnitude higher than that of a signal PIN detector of φ20mm×250μm; (2) remarkable statistics enhancement: The statistics enhancement of the array has been studied with M-C simulation,which displays highly enhanced statistics in very low pulsed γ flux measurement; (3) huge dynamic range: A single array can cover seven orders of magnitude's measurement range of γ flux; and (4) flat response in given γ energy range. The array has found its applications in experimental measurements.
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