2007 Vol. 31, No. 09
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In this paper, we discuss radiation fields in a compact space of finite size instead of that in a cavity for investigating the coupled atom-radiation field system. Representations of T(1)×SO(4) group are used to give a formulation for kinematics of the radiation fields. The explicit geometrical parameter dependence of statistical properties of radiation fields is obtained. Our results show remarkable differences from those of the black-body radiation system in free space.
Hadronic event selection and hadronic detection efficiency are two main sources of systematic error for the R measurement at BES/BEPC. If only the hadronic events with 2-prong and higher prong are selected as done in the previous measurements, the lost events with 0-prong and 1-prong will cause the systematic error for both of the number of hadronic events and the detection efficiency. This paper aims to present a new method to select the 1-prong hadronic events. It will be helpful to tune the parameters in hadronic events generator LUARLW more reasonably, and decrease the systematic errors of hadronic efficiency in R measurement.
By analyzing different hyperon decay processes, we derive the general formula for the decay contributions of heavier hyperons to hyperon production rates and final-state hyperon polarizations. Using a Monte-Carlo event generator , we study the decay contributions of hadrons to the final state hyperon polarizations in high energy reactions. The calculated results show that the decay contributions to the Λ polarization from other hyperons are very large and this result is universal and model independent. The polarization difference of Λ with high p⊥ in the singly polarized pp collision among different models may mainly come from the decay contributions of hadrons. Considering the uncertainties of such calculations, the polarizations of Σ±,Ξ0,Ξ－ would be better quantities for testing models.
Based on the isospin- and momentum-dependent transport model IBUU04, the transverse momentum distributions of the free neutron-proton ratio in the 132Sn+124Sn reaction system at mid-central collisions with beam energies of 400/AMeV, 600/AMeV and 800/AMeV are studied by using two different symmetry energies. It is found that the free neutron-proton ratio as a function of the transverse momentum at the mid-rapidity is very sensitive to the density dependency of the symmetry energy especially at incident energies around 400/AMeV.
Experiments show that total dose radiation effect in buried oxide of SOI (Silicon on Insulator) MOS is obviously dependent on bias condition. Trapped charge buildup during irradiation in buried oxide, which dominantly induces back channel leakage, is investigated. A numerical model, including process of carrier recombination and trapping, is developed to simulate the trapped charge buildup in buried oxide under different bias conditions. The simulation results, agreed with the experiment results, show the mechanism of bias dependence of total dose radiation effect.
THz radiation lying in the region between the microwaves and the infrared, with the property of high spatial resolution and low quantum energy, has wide applications. However, lacking of proper THz source has greatly delaying the related THz science and technology development. Peking University plans to construct a facility of THz source using the DC-SC superconducting accelerator. It is based on coherent undulator radiation. The source has the property of high peak power, high average power, high coherence, high repetition rate and tunable wavelength between 660—1200μm. The facility will provider a powerful tool for the research of biology, medicine, material, telecommunication and so on. This paper gives a brief description about the design considerations and an estimation on the property of the THz source.
In this talk I divide dark energy models (precisely speaking, models to explain origin of current cosmic acceleration) existing in literatures in to three classes. The first one is to ascribe the cosmic acceleration to modifications of general relativity at cosmological scales. The second one is due to the backreaction of perturbations, or say, the effect of inhomogeneity of the universe. The third one is some exotic component in the universe, which appears in the right hand side of Einstein's equations. For each class I demonstrate some examples.
CP asymmetries for neutral charmed meson decays into CP eigenstates are calculated by using amplitude ratios. The formulas and numerical results are presented. The impact on experiments is briefly discussed.
Motivated by the recent BES observation of the pp enhancement near threshold in radiative J/ψ decays, X(1860) and X(1835), we choose the 0－+ trigluonium state as a possible candidate and calculate its mass with QCD sum rules, which is found to be approximately in the region between 1.9GeV and 2.7GeV with some theoretical uncertainties. With the fact that the new BES resonance exhibits the behavior of this trigluon state, our analyses favor the baryonium-gluonium mixing picture for the BES observation.
In this talk we report our work on testing Noncommutative Space-Time Scale Using γγ→Z at ILC. In ordinary space-time theory, decay of a spin-1 particle into two photons is strictly forbidden due to the Yang's Theorem. With noncommutative space-time this process can occur. This process thus provides an important probe for noncommutative space-time. The γγ collision mode at the ILC provides an ideal place to carry out such a study. Assuming an integrated luminosity of 500fb－1, we show that the constraint which can be achieved on Γ(Z→γγ) is three to four orders of magnitude better than the current bound of 5.2×10－5GeV. The noncommutative scale can be probed up to a few TeVs.
In this paper we calculate the weak form factors of the decays B(Bc)→Dlν by using the chiral current correlator within the framework of the QCD light-cone sum rules (LCSR). The expressions of the form factors only depend on the leading twist distribution amplitude (DA) of the D meson. Three models of the D-meson distribution amplitude are employed and the calculated form factors,FB→D(0) and FBc→D(0) are given. In the velocity transfer region 1.14
We argue a factorization formula for semi-inclusive deep-inelastic scattering with hadrons in the current fragmentation region detected at low transverse momentum. To facilitate the factorization, we introduce the transverse-momentum dependent parton distributions and fragmentation functions with gauge links slightly off the light-cone, and with soft-gluon radiations subtracted. We verify the factorization to one-loop order in perturbative quantum chromodynamics and argue that it is valid to all orders in perturbation theory.
I introduce first the basic ideas of quantum field theory defined on non-commutative space-time. Some phenomenological investigations at linear colliders are very briefly reviewed. Then, I give some details on detecting non-commutative signals by pair production of neutral Higgs bosons in e+e－ collisions, and discuss how to use Lorentz symmetry violation to isolate signals from standard model backgrounds. Finally， very recent developments on realistic model building are also briefly mentioned.
Theoretical study of nuclear physics with strangeness from the nuclear physics group at Nankai university is briefly introduced. Theoretical calculations on hyperon mean free paths in nuclear medium have been done. The other 4 topics in the area of strangeness nuclear physics are the effect of different baryon impurities in nucleus, the heavy flavored baryon hypernuclei, the eta-mesons in nuclear matter and the properties of kaonic nuclei.
D0(2308) and B0 resonances are discussed with the molecular state assumption in the heavy chiral unitary approach. By studying the heavy baryon-pseudoscalar meson interaction, some molecular states are found. It is shown that there exists a bound DK state with a mass of about 2.312±0.041GeV in the strange sector, which can be identified as Ds0(2317). While in the non-strange sector, one wide-width state at about 2.1GeV and one narrow-width state at about 2.44GeV are found. These states should be associated with the D0 state. Therefore, D0(2308) cannot be explained by the assumption of the molecular structure only. Moreover, Bs0 and B0 states are also predicted. A BK bound state with the mass of 5.725±0.039GeV which can be assigned to the Bs0(5725) state and B0(5536) and B0(5819) should be considered as the corresponding states in the non-strange sector.
We have studied the interaction between dark energy and dark matter from the thermodynamical consideration. Assuming the interaction as stable fluctuations around equilibrium and using the logarithmic correction to entropy caused by the fluctuation, we have derived the physical expression of the interaction. We have tested the viability of our scenario on the inteaction by confronting with cosmological observations.
Triple-gluon elastic scatterings ggg→ggg and triple-quark elastic scatterings qqq→qqq are studied. The H-theorem extended to the transport equations with the 3→3 elastic scatterings is proved. A short thermalization time for gluon matter and a long thermalization time for quark matter are results of the transport equations.
The energies of the low-lying isoscalar and isovector udss configurations with spin-parity JP=0+, 1+, and 2+ are calculated in the chiral SU(3) quark model and the extended chiral SU(3) quark model by using the variational method. The model parameters are determined by the same method as in our previous work, and they still can satisfactorily describes the nucleon-nucleon scattering phase shifts and the hyperon-nucleon cross sections. The s-channel annihilation interaction is fixed by the masses of K and K* mesons, and the configuration mixing is considered. The results show that the udss configuration with I=0 and JP=1+ lies lower than the K*K* threshold, and furthermore, this state has a very small KK* component, thus it can be treated as a possible tetraquark candidate.
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