2010 Vol. 34, No. 2
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Based on the assumption of two-quark structure of the scalar meson K0*(1430), we calculate the CP-averaged branching ratios for B→K0*(1430) η(′) decays in the framework of the perturbative QCD (pQCD) approach here. We perform the evaluations in two scenarios for the scalar meson spectrum. We find that: (a) the pQCD predictions for Br(B→K0*(1430) η(′)) which are about 10－5−10－6, basically agree with the data within large theoretical uncertainty; (b) the agreement between the pQCD predictions and the data in Scenario I is better than that in Scenario II, which can be tested by the forthcoming LHC experiments; (c) the annihilation contributions play an important role for these considered decays.
In the framework of T2HDM, we calculated the new physics contributions involving neutral Higgs bosons to the branching ratios of B0s,d→l+l－ (l=e, μ) decays. Comparing the theoretical predictions with the experimental upper-limits, we found that (a) The data of Br(B0d→l+l－) give the upper bound on tanβ: tanβ≤22, while Br(B0s→l+l－) give tanβ≤12 for fixed δ=0°, mH+=350 GeV, mH0=160 GeV, mh0=115 GeV and mA0=120 GeV; (b) A light neutral Higgs boson mass mh0 (mA0) less than 50 GeV (120 GeV) is excluded by the data of branching ratios for B0s,d→l+l－(l=μ) decays with tanβ=10; (c) The bounds on mh0 and tanβ, or mA0 and tanβ are strongly correlated: a smaller (larger) tanβ means a lighter (heavier) neutral Higgs boson.
Based on Weinberg-Salam theory the bremsstrahlung neutrino energy loss for nuclei 24Mg, 28Si, 32S, 40Ca and 56Fe are investigated in strong electron screening. Our results are compared with those of Dicus' and show that the latter are higher by 2 orders of magnitude in the density-temperature region of 108 g/cm3≤ρ/μe≤1011 g/cm3 and 2.5≤T9≤4.5. On the other hand, the factor C shows that the maximum differences are 99.16%, 99.13%, 99.12%, 99.055%, 99.040% corresponding to the nuclei 24Mg, 28Si, 32S, 40Ca and 56Fe.
The neutron total cross-sections of thulium (169Tm) were measured in the neutron energy region from 0.01 eV to 100 eV by using the time-of-flight method at the Pohang Neutron Facility, which consists of an electron linac, a water-cooled tantalum target with a water moderator, and a 12 m time of flight path. Two thulium plates with different thicknesses were used for the neutron transmission measurement. The background level was determined by using a notch-filter of Co, In, and Cd sheets. The present measurement was compared with the previous ones, and a new set of resonance parameters of 169Tm isotope was obtained from the transmission rate by using the SAMMY code, with a comparison with the recommended parameters by Mughabghab.
The unified fission model (UFM) combining with the phenomenological assault frequency has been carried out to investigate the proton-radioactivity half-lives of spherical proton emitters. The results are in good agreement with the experimental data and other theoretical values, and newly observed spherical proton emitters have been analyzed. Finally, the effect of angular momentum transfer on half-life of proton emission has been discussed in detail and a formula can be used to describe this relationship.
We consider the production sources of prompt and thermal photons which include the contribution of gluons in relativistic heavy ion collisions. Considering in our calculation the shadowing and iso-spin effects of the nucleus we can properly estimate the prompt photon production. We develop a new thermal jet-photon conversion mechanism which plays a vital role in the low transverse momentum region. The effect of the non-equilibrium quark-gluon plasma
enhances the contribution of thermal photons.
The rare isotope 236U has a half-life of 2.342(3)×107 years, and is produced principally by thermal neutron capture on 235U. The isotopic atom ratio of 236U/238U depends on the integral thermal neutron flux received by the material of interest. 236U is potentially useful as a ``fingerprint'' for indicating the presence of neutron-irradiated uranium usually originating from nuclear activity. By extracting negative molecular ion UO－ from the uranium oxide target, simulating the 236U16O－ beam transport with 238U16O－ and 208Pb216O－ pilot molecular ion beam, transporting the 236U-containing ion beam with a high resolution injection magnet analyzer and electrostatic analyzer system, and finally identifying and detecting 236U with a time-of-flight detector (TOF), a method for AMS (Accelerator Mass Spectrometry) measurement of 236U was established on the HI-13 Accelerator AMS system at China Institute of Atomic Energy.
A prototype of the ME readout electronics onboard the Hard X-ray Modulate Telescope (HXMT) satellite is developed. Application Specific Integrated Chip (ASIC) is used to construct the front end electronics due to a large number of detectors. Field Programmable Gate Array (FPGA) is connected to the ASIC as a state machine controller and data FIFO in the DAQ system. A USB board is designed to communicate between the DAQ system and the computer. The design goals and features, the operation of the system and the preliminary performance of the prototype are described. The testing results show that the design goals of the prototype system have been achieved.
In this paper, the kinematic fitting with the Lagrange multiplier method has been studied for BESⅢ experiment. First we introduce the Lagrange multiplier method and implement kinematic constraints. Then we present the performance of the kinematic fitting algorithm. With the kinematic fitting, we can improve the resolution of track parameters and reduce the background.
In the proposal of the Beijing Advanced Light Source, a compact combination of XERL and XFEL using a common SC linac is being considered. In the meantime, an ERL-FEL test facility is being proposed and will be used for THz radiation. In this test facility, a L-band photocathode RF injector is needed. In this paper, we give the physical design of the L-band photocathode RF injector for the test facility.
Magnetic bunch compressor is one of the key technologies on the path to next generation accelerator driven facilities. In this paper we report the design principles and the first experimental research of the bunch compressor developed at Chinese Academy of Engineering Physics (CAEP). The length of the bunch after compressor is found to be about 0.7 ps (rms) and the peak current exceeds 500 A when operated in the optimized condition. The sensitivity of the bunch length on the phase of the acceleration field and magnetic field of the bunch compressor was also measured and analyzed.
This paper summarizes the painting injection optimization for the Chinese Spallation Neutron Source (CSNS) ring. This optimization focuses on two main design goals: the lower beam loss and a space-charge tune shift low enough to avoid strong resonances. Finally, the 3-D particle tracking is performed and we get some important results about the beam properties and beam loss.
Coherent X-ray microscopy has advanced towards higher-energy, more brilliant sources over the past decade since its demonstrations, and many advancements have been made towards optimizing this imaging technique. Here we present both the experimental instrument for obtaining diffraction patterns and the primary reconstruction of yeast cell 2D projection. In addition, the characteristics of the existing optics at BL29XUL of SPring-8 Facility and the method of image reconstruction are discussed.
The Electro-optical sampling delay scanning technique can be used for electron beam bunch length measurement. A novel non-ynchronous delay scanning technique based on the electro-optical sampling measurements is presented. Based on Beijing Free Electron Laser (BFEL), the electron beam bunch length was measured with the electro-optical sampling technique for the first time in China. The result shows that the electron beam bunch length at BFEL is about 5.6±1.2 ps.
A fully 3D OSEM reconstruction method for positron emission tomography (PET) based on symmetries and sparse matrix technique is described. Great savings in both storage space and computation time were achieved by exploiting the symmetries of scanner and sparseness of the system matrix. More reduction of storage requirement was obtained by introducing the approximation of system matrix. Iteration-filter was performed to restrict image noise in reconstruction. Performances of simulation data and phantom data got from Micro-PET (Type: Epuls-166) demonstrated that similar image quality was achieved using the approximation of the system matrix.
Diffraction enhanced imaging (DEI) with edge enhancement is suitable for the observation of weakly absorbing objects. The potential ability of the DEI was explored for displaying the microanatomy and pathology of human eyeball in this work. The images of surgical specimens from malignant intraocular tumor of hospitalized patients were taken using the hard X-rays from the topography station of Beamline 4W1A at Beijing Synchrotron Radiation Facility (BSRF). The obtained radiographic images were analyzed in correlation with those of pathology. The results show that the anatomic and pathologic details of intraocular tumors in human beings can be observed clearly by DEI for the first time, with good visualization of the microscopic details of eyeball ring such as sclera, choroids and other details of intraocular organelles. And the best resolution of DEI images reaches up to the magnitude of several tens of μm. The results suggest that it is capable of exhibiting clearly the details of intraocular tumor using DEI method.
The helicity amplitude Ap1/2 for the electromagnetic transition γ* N→N*(1535) is investigated. It is found that a new mechanism γ*→qq plays an important role in order to improve the description of this transition. On one hand, the Ap1/2 is decreased to fall in the data range at the photon point Q2=0, while on the other hand, the new mechanism makes the function Ap1/2(Q2) to decrease more slowly vs increasing Q2, as required by the data.
Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray sources. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100~GeV. In order to target those goals, a large air shower particle detector array of 1 km2 (the LHAASO project) at 4300 m a.s.l. is proposed. By adding two MagicII-type telescopes in the array as proposed, LHAASO will be enhanced in source morphologic investigation power. The proposed array will be utilized also for energy spectrum measurement for individual cosmic ray species above 30 TeV. By re-configuring the wide field of view telescopes into fluorescence light detector array, the aperture of the detector array can be enlarged to cover an energy region above 100 PeV where the second knee is located. Cosmic ray spectrum and composition will be measured in order to transfer an energy scale to ultra high energy cosmic ray experiments.
In the framework of the constituent quark model, the possible S-wave heavy dibaryon states with the c flavor are investigated. The factors which are responsible for the binding behavior of the dibaryon system are analyzed. It is shown that both the symmetry character of the system and the energy of interactions between interacting quarks are important for the binding behavior of the two-baryon system with the heavy flavor. As a result, seven possible candidates of heavy dibaryons with c flavor are predicted.
In this paper, we first discuss the detection of supernova neutrinos on earth. Then we propose a possible method to acquire information about θ13 smaller than 1.5° by detecting the ratio of the event numbers of different flavor supernova neutrinos. Such an sensitivity cannot yet be achieved by the Daya Bay reactor neutrino experiment.
We study the branching ratios of D+→D0e+ν, D+S→D0e+ν, B0S→B+e－ν, D+S→D+ e－e+ and B0S→B0e－e+ rare semileptonic decay processes, which are induced by decays of light quarks, the heavy quarks remain unchanged. The branching ratios of these decay processes are estimated in the heavy quark limit and with SU(3) flavor symmetry. We find that the decay rates are very tiny in the framework of the Standard Model. We also estimate the sensitivities of the measurements of these rare decays at the future experiments, such as BES-Ⅲ, super-B and LHC-b. Observations of these decays may shed some light on new physics beyond the standard model.
The experimental observation indicates that the branching ratio of ψ´→ρπ is very small while the ρ-π channel is a main one in J/ψ decays. To understand the puzzle, various interpretations have been proposed. Meanwhile according to the hadronic helicity selection rule, this decay mode should be suppressed. Numerical calculations are needed to determine how it is suppressed. We calculate the branching ratios of J/ψ→ρπ and ππ in the framework of QCD. The results show that the branching ratios are proportional to (mu+md/MJ/ψ)2 for the ρπ mode and (mu+md/MJ/ψ)2 for the ππ mode which is isospin violated. The theoretical prediction of the ratio of J/ψ→ρπ is smaller than data, but not too small to invoke a completely new mechanism. Thus the puzzle is still standing even though we learn much knowledge towards the puzzle and this will help to finally interpret the puzzle and then gain a deeper insight to the heavy quarkonia.
The collective properties in the even-even 78－84Kr isotopes have been studied within the framework of the $SD$-pair shell model. It is found that the collectivity of low-lying states in the even-even Kr isotopes can be described very well.
Relativistic corrections are important in hadronic physics since even for the heavy hadrons there are sizable relativistic corrections. Therefore one should use a relativistic model to describe the higher excited states. This note summarizes our predictions for the decay constants of the S wave and P wave heavy mesons by means of the instantaneous relativistic Bethe Salpeter equation (Salpeter equation).
In this work we investigate the minimal and next to minimal new gauge forces beyond standard model by constructing the corresponding electroweak chiral Lagrangians. Some phenomenological constraints from the mass differences in the K0－K0, Bd0－Bd0, Bs0－Bs0 systems and the corresponding CP violation parameter are discussed.
A summary of the current status of neutrino oscillations is given. We also include a brief description of the earlier development of neutrino physics and illustrate the roles that neutrinos play in several areas other than particle physics.
Based on a systematic investigation of J/ψ(ψ´)→VP, where V and P stand for light vector and pseudoscalar mesons, we identify the role played by the electromagnetic (EM) transitions and intermediate meson loop transitions, which are essential ingredients for understanding the J/ψ and ψ´ couplings to VP. We show that on the one hand, the EM transitions have relatively larger interferences in ψ´→ρπ and K*K+c.c. as explicitly shown by vector meson dominance (VMD). On the other hand, the strong decay of ψ´ receives relatively larger destructive interferences from the intermediate meson loop transitions. By identifying these mechanisms in an overall study of J/ψ(ψ´)→VP, we provide a coherent understanding of the so-called ``ρπ puzzle".
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