2012 Vol. 36, No. 8
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A chiral quark model is applied to calculate the spectra of pseudoscalar mesons η and η'. By analyzing the obtained spectra, we find that the mesons η'(21S0), η(41S0), η'(31S0) and η'(41S0) are the possible candidates of η(1760), X(1835), X(2120) and X(2370). The strong decay widths of these pseudoscalars to all the possible two-body decay channels are calculated within the framework of the 3P0 model. Although the total width of η'(21S0) is compatible with the BES Collaboration's experimental value for η(1760), the partial decay width to ωω is too small, which is not consistent with the BES result. If X(1835) is interpreted as η(41S0), the total decay width is compatible with the experimental data, and the main decay modes will be mπ a0(980) and m π a0(1450), which needs to be checked experimentally. The assignment of X(2120) and X(2370) to η'(31S0) and η'(41S0) is disfavored in the present calculation because of the incompatibility of the decay widths.
By means of the UGD function extracted from an AdS/CFT inspired saturation model, the charm and bottom structure functions are studied in fixed-order perturbation theory. It is shown that the theoretical results are in good agreement with the recent HERA data. Then, this UGD function is also used to investigate net-kaon rapidity distribution in Au+Au collisions at RHIC energies and the theoretical results fit well to the BRAHMS data. In the end of this paper, we give the predicted results for nuclear charm structure function at very small x where the popular shadowing parameterizations are invalid.
Based on the generalized QCD vector meson dominance model, we study the electroproduction of a vector meson off a proton in the QCD inspired eikonalized model. Numerical calculations for the total cross section σtot and differential cross section dσ/dt are performed for ρ, ω and φ meson electroproduction in this paper. Since gluons interact among themselves (self-interaction), two gluons can form a glueball with quantum numbers IG,JPC=0+,2++, decay width Γt≈100 MeV, and mass of mG=2.23 GeV. The three gluons can form a three-gluon colorless bound state with charge conjugation quantum number C=-1, called the Odderon. The mediators of interactions between projectiles (the quark and antiquark pair fluctuated from the virtual photon) and the proton target (a three-quark system) are the tensor glueball and the Odderon. Our calculated results in the tensor glueball and Odderon exchange model fit to the existing data successfully, which evidently shows that our present QCD mechanism is a good description of meson electroproduction off a proton. It should be emphasized that our mechanism is different from the theoretical framework of Block et al. We also believe that the present study and its success are important for the investigation of other vector meson electro- and photoproduction at high energies, as well as for searching for new particles such as tensor glueballs and Odderons, which have been predicted by QCD and the color glass condensate model (CGC). Therefore, in return, it can test the validity of QCD and the CGC model.
Recently an f-deformed Fock space which is spanned by |n〉λ was introduced. These bases are the eigenstates of a deformed non-Hermitian Hamiltonian. In this contribution, we will use rather new non-orthogonal basis vectors for the construction of coherent and squeezed states, which in special case lead to the earlier known states. For this purpose, we first generalize the previously introduced Fock space spanned by |n〉λ bases, to a new one, spanned by extended two-parameters bases |n〉λ1,λ2. These bases are now the eigenstates of a non-Hermitian Hamiltonian Hλ1,λ2=aλ1,λ2+a+(1/2), where aλ1,λ2+=a++ λ1a + λ2 and a are, respectively, the deformed creation and ordinary bosonic annihilation operators. The bases |n〉λ1,λ2 are non-orthogonal (squeezed states), but normalizable. Then, we deduce the new representations of coherent and squeezed states in our two-parameter Fock space. Finally, we discuss the quantum statistical properties, as well as the non-classical properties of the obtained states numerically.
Gravitational field equations in Randers-Finsler space of approximate Berwald type are investigated. A modified Friedmann equation and a new luminosity distance-redshift relation is proposed. A best-fit to the Type Ia supernovae (SNe) observations yields that the ΩΛ in the Λ-CDM model is suppressed to almost zero. This fact indicates that the astronomical observations on the Type Ia SNe can be described well without invoking any form of dark energy. The best-fit age of the universe is given. It is in agreement with the age of our galaxy.
The angular distribution of 1H(6He,p)6He elastic scattering has been measured at Ec.m.=4.3 MeV by using a thick-target inverse kinematic method. The experimental differential cross sections are reproduced by the distorted-wave Born approximation calculation utilizing the CH89 global optical potential parameter set. The real part of CH89 is reduced comparing with other potentials, which may be attributed to the couplings necessary for the weakly bound nuclei.
We calculate the production of large transverse momentum dileptons and photons by using direct and resolved photoproduction processes in relativistic heavy ion collisions. Considering the central collisions of heavy nuclei at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies, we find that the photoproduction processes modify the dilepton and photon production in the large transverse momentum region.
QCD deconfinement phase transition is supposed to be the same universality class as the 3D-Ising model. According to the universality of critical behavior, the Binder-like ratios and ratios of higher cumulants of order parameter near the critical temperature in the 3D-Ising model are studied. The Binder-like ratio is shown to be a step function of temperature. The critical point is the intersection of the ratios of different system sizes between two platforms. The normalized cumulant ratios, like the Skewness and Kurtosis, do not diverge with correlation length, contrary to the corresponding cumulants. Possible applications of these characters in locating critical point in relativistic heavy ion collisions are discussed.
Detailed measurements of Hamamatsu R5912 photomultiplier signals are presented, including the single photoelectron charge response, waveform shape, nonlinearity, saturation, overshoot, oscillation, prepulsing, and afterpulsing. The results were used to build a detailed model of the PMT signal characteristics over a wide range of light intensities. Including the PMT model in simulated Daya Bay particle interactions shows no significant systematic effects that are detrimental to the experimental sensitivity.
A photon conversion finder (PCF) based on track information from the main drift chamber (MDC) of the Beijing Spectrometer (BES0) at the Beijing Electron Positron Collider (BEPC/) is developed. The validation of the PCF is done by reconstructing π0 and measuring the branching fraction of J/ψ →γη'. Using the developed PCF tool, we mapped the materials from the interaction point through the BEPCII beam pipe up to the inner wall of the MDC.
Backward wave oscillators (BWOs) driven by intense relativistic electron beams are very efficient means of producing high-power microwaves. However, the efficiency of conventional BWO is lower than 30%. An X-band oversized BWO with non-uniform slow wave structure is designed to improve RF output characteristics. In particle-in-cell simulation, a high power microwave with a power of 8.0 GW and efficiency of 40% is obtained, compared with that of 30% obtained in a conventional relativistic BWO.
Firstly, an X-band relativistic backward wave oscillator with a low guiding magnetic field is simulated, whose output microwave power is 520 MW. Then, an experiment is carried out on an accelerator to investigate a relativistic backward wave oscillator with a permanent magnetic field whose strength is 0.46 T. When the energy of the electron is 630 keV and the current of the electron beam is 6.7 kA, a 15 ns width pulsed microwave with 510 MW output power at 8.0 GHz microwave frequency is achieved.
The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with the purpose of reaching a 37nm vertical beam size at the interaction point. In the nanometer beam size regime, higher order multipoles in magnets become a crucial point for consideration. The strength and rotation angle of the ATF2 QEA magnets were reconstructed from the IHEP measurements and compared with the KEK ones to be identical. Based on the study of the skew multipoles sensitivity, we report on the analysis of the possible mitigation of the measured multipoles. A suggestion is given which will benefit the ATF2 present commissioning to reach the goal beam size, and also the reduced β optics in future.
Very low Beta superconducting spoke cavity is one of the key challenges for the China-ADS project. In this paper, a new structure of 3βλ/2 spoke cavity is first studied in detail. Its RF and mechanical properties are simulated using CST-MWS and ANSYS, and compared with the traditional βλ/2 spoke structure.
The RF coupler is a key component for an accelerating structure which is the most important component for a linac. In order to feed microwave power into the accelerating cavities effectively, the coupler has to be well matched with the feeding waveguide. In this paper, an electron linac coupler was designed, constructed and tested. A numerical simulation method based on the Kyhl's method was employed to search for the optimal dimensions of the coupler. The frequency and the coupling coefficient as a function of the coupler dimensions were also calculated. The results fitted the Kyhl's method simulation results well and gave tolerances of the coupler. The coupler was brazed to the accelerating cavities and it was cold-tested and hot-tested. The experimental results were consistent with the numerical simulation results.
We propose a slanting collision scheme for Compton scattering of a laser light against a relativistic electron beam. This scheme is suitable to generate an energy-tunable X/γ-ray source. In this paper, we present theoretical study and simulation of the spectral, spatial and temporal characteristics of such a source. We also describe two terms laser-Compton scattering (LCS) experiments at the 100 MeV Linac of Shanghai Institute of Applied Physics, where quasi-monochromatic LCS X-ray energy spectra with peak energies of ～30 keV are observed successfully. These preliminary investigations are carried out to understand the feasibility of developing an energy-tunable quasi-monochromatic X/γ-ray source, the future Shanghai Laser Electron Gamma Source.
Computed laminography (CL) is an alternative to computed tomography if large objects are to be inspected with high resolution. This is especially true for planar objects. In this paper, we set up a new scanning geometry for CL, and study the algebraic reconstruction technique (ART) for CL imaging. We compare the results of ART with variant weighted functions by computer simulation with a digital phantom. It proves that ART algorithm is a good choice for the CL system.
An active spot beam delivery system for heavy ion therapy has been developed based on the Cooling Storage Ring at HIRFL-CSR, where the pencil carbon-ion beams were scanned within a target volume transversely by a pair of orthogonal (horizontal and vertical) dipole magnets to paint the slices of the target volume and longitudinally by active energy variation of the synchrotron slice by slice. The unique techniques such as dose shaping via active energy variation and magnetic deflection constitute a promising three-dimensional conformal even intensity-modulated radiotherapy with heavy ions at HIRFL-CSR. In this paper, the verification of active energy variation and the calibration of steerable beam deflection are shown, as the basic functionality components of the active spot-scanning system. Additionally, based on the capability of creating homogeneous irradiation fields with steerable pencil beams, a radiobiological experiment like cell survival measurement has been performed aiming at comparison of the radiobiological effects under active and passive beam deliveries.
Proton radiography is a new tool for advanced hydrotesting. This article will discuss the basic concept of proton radiography first, especially the magnetic lens system. Then a scenario of 50 GeV imaging beamline will be described in every particular, including the matching section, Zumbro lens system and imaging system. The simulation result shows that the scenario of imaging beamline performs well, and the influence of secondary particles can be neglected.
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