2010 Vol. 34, No. 07
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We study J/ψ inclusive production in the decays of P-wave bottomonium χbJ(1P,2P) for J=0,1,2. Within the framework of the non-relativistic QCD (NRQCD) factorization method we calculate the contributions coming from four relevant processes including one color-singlet process and three color-octet ones, which are bb(3PJ, 1)→cc(3S1,8)+c+c, bb(3S1,8)→cc(3S1,1)+g+g, bb(3S1,8)→cc(3S1,1)+c+c and bb(3S1,8)→cc(3S1,8)+g. Our calculation shows that the color-octet processes, especially the gluon fragmentation one, contribute the most in the decays of χb0 and χb1. However, the J/ψ production in the χb2 decay is dominated by the color-singlet process. Furthermore, the gluon fragmentation process gives a δ function in the energy fraction distribution of J/ψ, which can be considered to be another characteristic for its identification. From our estimation the branching ratio for these processes is about 10－4－10－5, which indicates that J/ψ inclusive production is detectable at B-factories. Studying these processes would help us to gain a deeper understanding of the color-octet mechanism.
In this paper, we calculated the B→(J/ψ,ηc)K decays in the perturbative QCD (pQCD) factorization approach with the inclusion of the partial next-to-leading order (NLO) contributions. With the inclusion of the significant enhancement from the NLO vertex corrections, the NLO pQCD predictions for the branching ratios agree with the data within 2σ errors: Br(B0→J/ψK0)=5.2+3.5－2.8×10－4, Br(B+→J/ψK+)=5.6+3.7－2.9×10－4, Br(B0→ ηcK0)=5.5+2.3－2.0×10－4, Br(B+→ηcK+) = 5.9+2.5－2.1×10－4.
First a description of 2+1 dimensional non-commutative (NC) phase space is presented, and then we find that in this formulation the generalized Bopp's shift has a symmetric representation and one can easily and straightforwardly define the star product on NC phase space. Then we define non-commutative Lorentz transformations both on NC space and NC phase space. We also discuss the Poincare symmetry. Finally we point out that our NC phase space formulation and the NC Lorentz transformations are applicable to any even dimensional NC space and NC phase space.
We construct the transfer matrix for the open chain with the centrally extended SU(2|2) symmetry attached to the so called Z=0 giant graviton brane. Using the reflection quations, unitarity property and crossing property, we show that this model is integrable.
According to some experimental and evaluated data, the total excitation energy partitioning way between both of the fission fragments was given with a semi-empirical method. With the calculated energy partitioning way, the prompt neutron multiplicity as a function of fragment mass, ν(A), for neutron-induced fission of 235U at En=0.0253 eV, 3 MeV, and 5 MeV was calculated. The results are checked with the total average prompt neutron multiplicities ν and compared with the experimental and evaluated data.
Seven experimentally observed bands of 155Tb are analyzed in detail, using the particle-number-conserving method for treating the cranked shell model with monopole and quadrupole pairing interactions. We satisfactorily reproduce the experimental alignments and especially focus on the microscopic mechanism of the second back-bending and the influence of pair interaction on ultrahigh spins. Our calculated results show that the πi13/2 orbitals are too high to give a contribution to the moment of inertia below hω≈0.7 MeV. Instead, the crossing between the π1/2 and other proton orbitals is responsible for the second back-bending. We assign a possible configuration to the decoupled band found in 155Tb and predict eleven bands which are experimentally unobserved.
The transverse momentum distributions of final-state particles produced in collisions at high energies are studied by using a two-component Rayleigh-like distribution. This representation is based on Liu's multisource ideal gas model which describes protons and fragments in high energy nucleus-nucleus collisions. The calculated results are in good agreement with the experimental data of Au-Au, Cu-Cu, d-Au, and pp collisions at the relativistic heavy ion collider energies. The experimental particle momentum distributions of p-Be collisions at 6.4, 12.3, and 17.5 GeV/c, as well as Au-Au collisions at 1.5 AGeV are well described by a model based on a single Rayleigh-like distribution of particle transverse momenta.
The basic process of re-ionization loss was studied. In the drift duct there are three processes leading to re-ionization loss: the collision of neutral beam particles with the molecules of background gas, similar collisions with released molecules from the inner wall of the drift duct and the ferret-collisions among particles with different energy of the neutral beam. Mathematical models have been developed and taking EAST-NBI parameters as an
example, the re-ionization loss was obtained within these models. The result indicated that in the early stage of the neutral beam injector operation the released gas was quite abundant. The amount of re-ionization loss owing to the released gas can be as high as 60%. In the case of a long-time operation of the neutral beam injector, the total re-ionization loss decreases from 13.7% to 5.7%. Then the re-ionization loss originating mainly from the collisions between particles of the neutral beam and the background molecules is dominant, covering about 92% of the total re-ionization loss. The drift duct pressure was the decisive factor for neutral beam re-ionization loss.
A Penning trap system called Lanzhou Penning Trap (LPT) is now being developed for precise mass measurements at the Institute of Modern Physics (IMP). One of the key components is a 7 T actively shielded superconducting magnet with a clear warm bore of 156 mm. The required field homogeneity is 3×10－7 over two 1 cubic centimeter volumes lying 220 mm apart along the magnet axis. We introduce a two-step method which combines linear programming and a nonlinear optimization algorithm for designing the multi-section superconducting magnet. This method is fast and flexible for handling arbitrary shaped homogeneous volumes and coils. With the help of this method an optimal design for the LPT superconducting magnet has been obtained.
The BESⅢ drift chamber and its subsystems need a cosmic-ray test after the chamber construction to check the chamber construction quality, testing the joint operation of the whole system and the performance of the chamber. The noise performance, drift time and
charge measurements, and the scanning of channels were examined specifically. The preliminary results of the test indicate that the whole system works well.
The light output functions for protons of ST-401 and BC-408 plastic scintillators were measured using white neutron source produced by the 9Be(d, n) 10B reaction at the HI-13 Tandem Accelerator at China Institute of Atomic Energy (CIAE). The LOFs of plastic
scintillators for protons in the energy range of 0.5—16.5 MeV were obtained by the time-of-flight (TOF) technique and an iterative procedure. Two parameters (kB and C) were deduced by fitting the experimental data.
An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described. The energy resolution and the position of the Compton edge have been precisely determined using a γ-γ coincidence technique and fitting the coincidence spectrum with a Gaussian function superimposed on a quadratic polynomial for the
background. The position of the Compton edge relative to the position of the maximum and the half height of the distribution in dependence on the relevant energy resolution is discussed in detail. The results indicate that the maximum energy of the recoil Compton electron does not occur at the half height distribution but at 0.90±0.05 of the maximum height in the energy range considered. The energy resolution varies from 15.6% to 8.02% for electrons in the energy region from 0.5 MeV to 3 MeV.
The 400 MeV/u 12C6+ ion beam was successfully cooled by the intensive electron beam near 1 A in CSRe. The momentum cooling time was estimated near 15 s. The cooling force was measured in the cases of different electron beam profiles, and the different angles between the ion beam and electron beam. The lifetime of the ion beam in CSRe was over 80 h. The dispersion in the cooling section was confirmed as positive close to zero. The beam sizes before cooling and after cooling were measured by the moving screen. The beam diameter after cooling was about 1 mm. The bunch length was measured with the help of the signals from the beam position monitor. The diffusion was studied in the absence of the electron beam.
To develop the high power proton linear accelerator for the Accelerator Driven System (ADS) program, the preliminary design of the Pi mode accelerating structure (PIMS) has been carried out. It is estimated that PIMS would heat up to 80 ℃ for low duty cycle (0.1%) without water-cooling, which is not acceptable, thus water-cooling is demanded. The structure stability for the high duty cycle or even for CW operation is crucially important for the ADS application. Therefore, thermal analysis with water-cooling for a high duty accelerator in our ADS research is performed to control the frequency shift caused by a temperature rise.
A design strategy is discussed in this paper, and it provides much convenience for effectively exploring achievable linear optics and globally investigating the flexibility of a complex lattice with super-periodicity. A matching method of fractional steps, which means separately finding the standard cell setting and the matching cell setting, is adopted to simplify the complexity of the linear beam optics design in the complex lattice. The multi-objective genetic algorithm is used to find most of all the stable linear optics, and reach a target solution after multi-generational propagation, both in the standard cell and the matching cell. A fitting algorithm with gradient information is used to restore the periodicity and symmetry of the lattice, and finely adjust the linear optics for further optimization. This design strategy is applied in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring, and the results are presented.
For practicability of the high power microwave source, a C-band backward wave oscillator (BWO) which has high conversion efficiency is designed. When the axial guiding magnetic
field is 0.83 T, the electron energy and the beam current of the diode are respectively 80 keV and 2.1 kA, a microwave output power of 100 MW at 7.4 GHz microwave frequency with 65% conversion efficiency is achieved in simulation.
In order to take away much more heat on the BESⅢ beam pipe to guarantee the normal particle detection, EDM-1 (oil No.1 for electric discharge machining), with good thermal and flow properties was selected as the candidate coolant for the central beryllium pipe of the BESⅢ beam pipe. Its cooling character was studied and dynamic corrosion experiment was undertaken to examine its corrosion on beryllium. The experiment results show that EDM-1 would corrode the beryllium 19.9 μm in the depth in 10 years, which is weak and can be neglected. Finite element simulation and experiment research were taken to check the cooling capacity of EDM-1. The results show that EDM-1 can meet the cooling requirement of the central beryllium pipe. Now EDM-1 is being used to cool the central beryllium pipe of the BESⅢ beam pipe.
Using a diamond anvil cell device and synchrotron radiation, the in-situ high-pressure structure of CaMnO3 has been investigated. In the pressure up to 36.5 GPa, no pressure-induced phase transition is observed. The pressure dependence on the lattice parameters of CaMnO3 is reported, and the relationship of the axial compression coefficients is βa>βc>βb. The isothermal bulk modulus K298=224 (25) GPa is also obtained by fitting the pressure-volume data using the Murnaghan equation of state.
The China Spallation Neutron Source (CSNS) is going to be located in Dalang Town, Dongguan City in the Guangdong Province. In this paper we report the results of the parameters related with environment safety based on experiential calculations and Monte Carlo simulations. The main project of the accelerator is an under ground construction. On top there is a 0.5 m concrete and 5.0 m soil covering for shielding, which can reduce the dose out of the tunnel's top down to 0.2 μSv/h. For the residents on the boundary of the CSNS, the dose produced by skyshine, which is caused by the penetrated radiation leaking from the top of the accelerator, is no more than 0.68 μSv/a. When CSNS is operating normally, the maximal annual effective dose due to the emission of gas from the tunnel is 2.40×10－3 mSv/a to the public adult, and 2.29×10－3 mSv/a to a child, both values are two orders of magnitude less than the limiting value for control and management. CSNS may give rise to an activation of the soil and groundwater in the nearest tunnels, where the main productions are 3H, 7Be, 22Na, 54Mn, etc. But the specific activity is less than the exempt specific activity in the national standard GB13376-92. So it is safe to say that the environmental impact caused by the activation of soil and groundwater is insignificant. To sum up, for CSNS, as a powerful neutron source device, driven by a high-energy high-current proton accelerator, a lot of potential factors affecting the environment exist. However, as long as effective shieldings for protection are adopted and strict rules are drafted, the environmental impact can be kept under control within the limits of the national standard.
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