2003 Vol. 27, No. 10
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We show that the recent WMAP data can impose a generous upper bound on the effective masses of electron, muon and tau neutrinos defined in the kinematic measurements:
The BES II backgrounds experiment and simulation are described. In the experiment, we have studied the characteristics of the beam-related backgrounds. In the simulation, we simulate carefully the beam-gas backgrounds with the mature tools-TURTLE and Geant3. Finally, we compare the results of the experiment and those of the simulation, they agree with each other within a factor of 4, which is acceptable in background simulation. This comparison proves the simulation tools are reliable, which makes it possible for us to simulate the beam-related backgrounds of the future BES-BESIII.
We study the process that the light initial quarks produced in e+ e- annihilation combine with the c from glu-on splitting to form D's (D-+D6-+D0) or D 's(D-*+ Ds*-+D*0). The 'light + heavy' bound state is described by light-cone wavefunction. The contribution of this process to D (D ) production at Z0 pole is much larger compared with that in lower energies (e.g. 10.6GeV) . For this special process, the invariant mass of D(D) and the charm had-ron fragmented from the c quark has a unique spectrum which peaks near 2 MB if we constrain the D(D*) from all processes with energy larger than 20GeV. It is also noticeable that the produced D* in this process is dominantly longitudinally polarized, which is consistent with the OPAL data.
We study the gluonic content of the pomeron through relating the pomeron trajectory to the observed IGJPC=0+2++ isoscalar tensor mesons. Four of these mesons satisfy the spin-mass relation of the pomeron. These pomeronian candidates may be hybrid states. One of them, the f2(2220) meson, can have a predominant glueball component. We address the unsettled experimental situation about the width of this meson and give a theoretical lower bound for it. We also show why this meson may not be seen in pp experiments.
The Faddeev-Jackiw quantization method is applied to the complex scalar field coupled to the Abel Chern-Si-mons term, the results agree with the results obtained by using Dirac method. It is shown that this method is quite straightforward and elegant for this system.
In the case of existing of the magnetic charge, we give out the relationship between the field strengths and the doublet potentials. Then we obtain the d' Alembert equation for these doublet potentials. Using the retarded solutions of the d' Alembert equations, we find the expressions of radiation field strengths of dyons. Finally we discuss the electromagnetic (EM) radiation of the high speed moving dyons.
Quintessence is a possible candidate for dark energy. In this paper we study the possibility of Quintessence interacting with the ordinary matter and its implications in baryogenesis. With a specific coupling of the Quintessence to the baryon fields, we will show that the baryon number asymmetry of the universe can be explained naturally. We will also in this paper study the isocur-vature perturbation of the baryon number in our model.
The Noether charge formalism on the covariant phase space is used and developed. For a stationary axisym-metric black hole in vacuum general relativity, the mass formula is the vanishing Noether charge with respect to the Killing vector field an entire Cauchy surface. Its differential form gives the first law of black hole mechanics . For a large class of vector fields, the central term of the reduced algebra near the horizon is proved to be zero by use of the null tetrad formalism. It implies that the microscopic interpretation of the black hole entropy based on the symmetry analysis proposed by Carlip is debatable.
The level structure of high-spin states of doubly odd nucleus l46Tb has been studied via the 118Sn (32S, 1p3n) Tb reaction using techniques of in-beam y-ray spectroscopy. Measurements of r-ray excitation functions, y-ray anisotropies, X-r and r-r-t coincidences were performed with 12 BGO(AC)HPGe detectors. Based on the gated spectra, r-r coincidence relationships, intensity balances and cross-over transitions, the level scheme in 146Tb has been extended up to an excitation energy of 8390 keV, and 41 new 7-rays are added into the level scheme. The spins for the new established levels have been assigned according to the results of the measured 7-ray anisotropies. The levels in 146Tb are interpreted qualitatively by coupling a h11/2 proton to a h11/2 neutron hole and h11/2 υ h11/2－1 to the excited states in 146Gd core.
Within the isospin dependent extended Brueckner-Hartree-Fock framework, the proton and neutron mean free paths in isospin asymmetric nuclear matter and their isospin denpendence have been investigated. It is shown that as increasing the isospin asymmetry, the proton mean free path decreases while the neutron one increases. This implies that the surface of a neutron-rich nuclei near drip-line will be much more transparent for neutrons than for protons. The density dependence of the mean free paths and the effect of the ground-state correlations on the mean free paths have also been discussed.
Study of the relation between a meson' s mass ma and nuclear binding energy in chiral a model is given. The main purpose of this paper is to study the so-called "tachyon pole" problem at one-loop level in chiral a model. That is, the square of the pion or a meson effective mass become negative and this will lead to imaginary energy density. We regard mσ as a free parameter and adjust it (especially use smaller mσ) to fit the saturation properties. On-mass-shell renormalization, vacuum fluctuation and one-loop approximation are applied to numerical calculations. Results are indicated for mσ=307.5MeV in which the "tachyon pole" doesn't appear at nuclear density lower than 4.43ρ0(ρ0is the saturation nuclear density) , so that the binding energy curve and the value for the compressibility K(≌=175.7MeV) are obtain at the first time.
The isospin fractionation in intermediate energy heavy ion collisions is studied by using isospin dependence quantum molecular dynamics model. At first, the reaction productions in isospin fractionation process is separated into a gas phase and a liquid phase. The gas phase includes free neutrons and protons. But there are many choices for the liquid phase, we select the fragments from the region of 1
LUCIAE3 .0 model was used to simulate the relativistic heavy-ion collisions, namely C+C,Si+Si and Pb+Pb, which were already performed experimentally by NA49 collaboration. The simulated results of rapidity and transverse momentum distributions of all kinds of hadrons were compared with the NA49 data and found that they can fit the experimental data mostly. The kinetic temperature was deduced by the thermal fits to the transverse mass distributions of hadrons . It is found that the temperatures of light systems or hadrons fit the experimental data well, however, those of heavy systems or hadrons deviate much from the data, which probably because that LUCIAE3 .0 doesn' t include the information of QGP phase transition.
A transverse field gas ionization chamber for particle identification at the Radioactive Ion Beam Line in Lanzhou (RIBLL) is described. It consists of cathode, Frisch grid and 4 anodes (20,40,80,136mm). The MAIC was measured at 104Pa of operating gas P10(10% CH4+90 % Ar) . By setting the voltage of anode at 100V, the plateau of the MAIC is 700V varing from - 300V to - 1000V. With voltage of anode at + 225V and the voltage of cathode at -700V, the energy resolution of MAIC is 41.1keV for 1 .30 MeV 244Cm a and relative energy resolution (ΔE/E) is 3.16% at the fourth anode.
Monte Carlo method is used to simulate the random noise in the BES II drift chamber and its effect on the performance. Noises from both t and q channels are considered on hit and non-hit sense wires respectively. Track efficiency and momentum resolution under different noise levels and different noise distributions are presented.
A new Electron Cyclotron Resonance (ECR) ion source, which was named LECR3 (Lanzhou Electron Cyclotron Resonance ion source no. 3) and expected to provide highly charged ion beams for atomic physics research, has been constructed and under commissioning. The design of this ion source is based on the IMP 14.5GHz ECR ion source, which was named LECR2 (Lanzhou Electron Cyclotron Resonance ion source no. 2) . In the new source it was desired with double RF heating by inserting waveguide directly and aluminum chamber. Furthermore, the volume of the plasma chamber is larger than that of LECR2 so as to increase the RF power and increase beam intensity for highly charged ions. But the hexapole field on the chamber wall is kept the same value in order to compare with the performance of LECR2 ion source. The results of this ion source are obviously better than LECR2. We obtained 780 euA of 06+, 235euA of O7+ and 240euA of Ar11+ at 1100 watts of 14.5GHz RF power singly. Furthermore, in order to transmit the ion beams efficiently a new beam focusing and analyzing system was designed and constructed at the same time.
With reference to the KERB 509 MHz superconducting (SC) cavity, a 500MHz SC cavity for the Beijing Electron Positron Collider upgrade project (BEPC II) has been designed. Some simulations on the cavity have been made and some of cavity performances have been checked by the BEPC II model cavity.
The paper presents the nonlinear transport of the intense pulsed charged particle beams analyzed with the Lie algebraic method. The particles are supposed to be distributed in 3D dimensional ellipsoid in Gaussian manner. The analysis is performed for magnetic quadrupoles, and is similar for dipoles, sextupoles and other optical elements.
Heavy ion beams used for tumor therapy have some important advantages. Especially, the optimization of the depth-dose distribution of the heavy ion beam in a given focus of a tumor by using a Spread-Out Bragg Peak (SOBP) technique will greatly enhance the therapeutic effects for the tumor therapy. We adopted the simulated annealing algorithm to complete the optimization process for the high energy(-C 120MeV/u) heavy ion beam, which can be supplied by HIRFL, in a 30cm range of water and with 4 different step lengths to give a set of SOBP parameters such as the average dose, the input dose, the ratio of peak to plateau, the standard deviation, etc. The result shows that the selecting of 0.5-1mm as a step length is suitable.
This paper introduces the particle transport process in brain, which is simulated by general Monte Carlo code MCNP. The absorbed dose rates from 10B(n,a)7Li,14N(n,p)14C,1H(n,r)2D and fast neutron elastic scattering reaction are considered. The major contribution to the tumor zone is from the neutron capture reaction of boron. The comparison of the absorbed dose rates from thermal and epithermal neutron indicates that the epithermal neutron beam is more effective than thermal neutron beam in destroying deep-seated tumors,on the contrary,the latter is valid for shallow tumor,e.g.skin cancer.In comparison with deterministic method DOSE program, MCNP code is convenient in simulation of Boron Neutron Capture Therapy.
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