Searching for new physics in D^0→μ^＋ μ^-,e^＋e^-,μ^±e at BES and/or the super charm-tau factory

In contrast with B0-ˉB0, Bs-ˉBs mixing where the standard model（SM） contributions overwhelm that of the new physics beyond standard model（BSM）, a measured relatively large D0-ˉD0mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D0→μ＋μ-could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D0. Concretely we discuss the contributions of unparticle or an extra gauge boson Z while imposing the constraints set by fitting the D0-ˉD0mixing data. We find that the long-distance SM effects for D0→lˉl still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D0→μ±e, the new physics contribution would be significant.     

Investigation on dependence of BiFeO3 dielectric property on oxygen content

The influence of oxygen content on the dielectric property of BiFeO3 ceramics is studied by experiment and firstprinciples calculation.The experimental result demonstrates that the dielectric constant of BiFeO3 is strongly dependent on introduced oxygen and oxygen vacancies.By comparison with BiFeO3,the introduced oxygen and oxygen vacancies can lead to a reduction in dielectric constant of BiFeO δ at a lower frequency.The first-principles calculation also shows a similar result when photon energy is in a range of 2.0-4.1 eV.A likely explanation is that this oxygen content dependence may be ascribed to the distortion of Fe-O octahedron structure due to oxygen vacancies or excess oxygen ions in the crystal structure of BiFeO3.     

The formation mechanism and the binding energy the body—centred regular tetrahedral structure of He5^＋

We propose the formation mechanism of the body-centred regular tetrahedral structure of the He5^ cluster,The total energy curve for this structure has been calculated by using a modified arrangement channel quantum mechanics method.The result shows that a minimal energy of -13.9106 a.u.occurs at a separation of 1.14a0 between the nucleus at the centre and nuclei at the apexes.Therefore we obtain the binding energy of 0.5202a .u.for this structure.This means that the He5^ cluster may be stable with a high binding energy in a body-centred regular tetrahedral structure.     

Possible Experimental Evidence of a Moderate Proton Halo in ^29S

The total reaction cross sections (TRCSs) of^29S ^28Si have been measured at intermediate energies. An obvious enhancement in TRCS of ^29S is observed as compared with its neighbouring nuclei. The TRCSs of ^29S ^28Si arecal culated with the modified Glauber theory in the optical limit and few-body approaches. The different factor d as a possible measure of halo appearance is deduced from the experimental and theoretical data. It is well accepted that ^27p is a proton halo nucleus. Although not as anomalous as ^27p, the different factor d of ^29S is obviously larger than that of its neighbouring isotones of N = 13. This result indicates that a moderate proton halo may exist in ~9S nucleus. We calculate the total reaction cross sections for ~9S with the modified Glaubertheory as a function of incident energy and compare the results with those for 2rSi which is a core nucleus 0f29S.The measured TRCSs of 27Si4-2SSi can be described to be satisfactory by the modified Glauber theory of theoptical limit approach. Although a diffused nuclear density distribution is used, the theories still inadequatelypredict the experimental TRCSs of 29S4-2SSi, which further indicates the possibility of proton halo in 29S.     

Formation Mechanism and Binding Energy for Icosahedral Central Structure of He13^＋ Cluster

The formation mechanism for the icosahedral central structure of the He13^ cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the function of separation R between two nuclei at the center and an apex of the icosahedral central structure. The result of the calculation has shown that the curve has a minimal energy -37.5765 (a.u.) at R=2.70ao. The binding energy of He13^ with respect to He^ 12He was calculated to be 1.4046 a.u. This means that the cluster of He13^ may be formed in an icosahedral central structure with strong binding energy.     

The Formation Mechanism and Binding Energy for the Octahedral Central Structure of the He7^＋ Cluster

The formation mechanism for the octahedral central structure of the He7^ cluster is proposed and its total energy curve is calculated by the method of a modified arrangement channel quantum mechanics (MACQM). The energy is a function of separation R between two nuclei at the center and an apex of the octahedral central structure. The result of the calculation shows that the curve has a minimM energy -19.7296 a.u. at R = 2.40α0. The binding energy of He7^ with respect to He^ 6He was calculated to be 0.6437 a.u. This means that the duster of He7^ may be formed in the stable octahedral central structure with R=2.40 α0.     

Re-evaluation of the ^23Mg（p,γ） ^24Al reaction rate

Based on a new screening Coulomb model, this paper discusses the effect of electron screening on proton capture reaction of 23Mg. The derived result shows that, in some considerable range of stellar temperatures, the effect of electron screening on resonant reaction is prominent; on the non-resonant reaction the effect is obvious only in the low stellar temperatures. The reaction rates of ^23Mg（p,γ） ^24Al would increase 15%-25% due to the fact that the electron screening are considered in typical temperature range of massive mass white dwarfs, and the results undoubtedly affect the nucleosynthesis of some heavier nuclei in massive mass white dwarfs.     

Generations of dark hollow beams and their applications in laser cooling of atoms and all optical-type Bose－Einstein condensation

We report on a new experimental result to generate dark hollow beams by using a geometric optical method. We propose two new methods to produce focused and localized hollow laser beams by using π-phase plates. Using Monte-Carlo simulations, we have studied the Sisyphus cooling of alkali atoms in pyramidal hollow beam gravito-optical traps. We discuss some potential applications of the dark hollow beams in atom optics and the preparation of an all optically-cooled and optically-trapped atomic Bose－Einstein condensation (BEC). Our research shows that an ultracold atomic sample with a temperature of ～ 2μK can be obtained in the pyramidal hollow beam dipole trap and an all optical-type BEC may be realized in a far blue-detuned, hollow beam trap.     

Semiclassical calculation of Rydberg He2^＋ molecular of recurrence spectra ion in a magnetic field

Making use of the molecular closed-orbit theory and a new model potential for the Rydberg molecule, we have calculated the recurrence spectra of He^2＋ molecular ion in a magnetic field for different quantum defects. The Fourier transform spectra of He^2＋ molecular ion may be used to perform a direct comparison between peaks in the spectra and the scaled action values of closed orbits of the excited electron in external fields. We find that the spectral modulations can be analysed in terms of the scattering of the excited electron on the molecular core. Unlike the case of the Rydberg atom where the elastic scattering is predominant, modulations produced by inelastic scattering are also vital to the photoabsorption spectrum of the Rydberg molecule. Our results are in good agreement with the quantum results, which suggests that our method is correct.     

NLO Corrections of HTC∏^0 and ∏＋∏- Pair Production at ILC in TC2 Model

As well known, if the Higgs boson were not observed at LHC, the technicolor model would be the most favorable candidate responsible for the symmetry breaking. To overcome some defects in the previous model, some extended versions have been proposed. In the TC2 model typical signature is existence of heavy HTC and technipion ∏. A direct proof of validity of the model is to produce them at accelerator. Thus we study the production rates of e＋e^- → HTC∏^0 and e＋e^- → ∏＋∏- at ILC in the topcolor-assisted technicolor （TC2） model. In fact, there is a flood of models belonging to new physics, which can result in products with characteristics similar to HTC ＋ ∏ of the TC2 model. Therefore to distinguish this model from others one may need to investigate some details by calculating the cross section to NLO. We indeed find that the NLO corrections are significant, namely the ratio δ ≡（ σNLO - σLO）/σLO in e＋e- →HTC∏^0 exceeds 100% within a plausible parameter space.     

Hydrogen burning of 24, 25, 26Mg in explosive carbon burning

The absolute resonance strengths of the ^24–26Mg(p, γ)^25–27Al reactions have been studied. The absolute values S_c.m.=1.03 ± 0.11, 2.3 ± 0.2 and 2.2 ± 0.2 eV for the frequently used standard resonances at E_p=823, 434 and 454 keV in the reactions ^24–26Mg(p, γ)^25–27Al, respectively, have been determined. In addition, absolute values for use as standards were determined for the 684 keV ²⁵Mg(p, γ)²⁶Al and 840 and 1966 keV ²⁶Mg(p, γ)²⁷Al resonances. New relative values were determined for the strengths of the if²⁵Mg(p, γ)²⁶Al resonances at ifE_{p = 0.3–1.7 MeV} and the ²⁶Mg(p, γ)²⁷Al resonances at E_p = 0.3–2.1 MeV. The resonance energies and total widths obtained in the present work are also given. The branching ratios and angular distributions of the γ-rays used in the absolute strength determinations were obtained in the same set-up as the absolute strength measurement. Using the revised resonance strengths, the astrophysical reaction rates of hydrogen burning of ^24–26Mg in explosive carbon burning in the stellar temperature region of T = (0.1–5.0) × 10⁹ K are compared with Hauser-Feshbach calculations. The present reaction rates are also discussed in the frame of the MgAl cycle.     

Proton threshold states in 26Al

The energy levels of ²⁶Al between E_x = 6.3 and 6.5 MeV, corresponding to proton threshold energies in the ²⁵Mg + p reaction from $\text{E}{}_{\mathrm{<mtext>p</mtext>}}\text{= 0}\text{to}\text{200}\text{keV}\text{, have been investigated using the reactions}{}^{27}\text{Al(su3}$He, α)²⁶Al and ²⁴Mg(³He, p)²⁶Al. Despite early work reporting a doublet at E_x = 6346 keV and E_x = 6362 keV, most subsequent work reported a single state with conflicting spin and parity assignments. Our work clearly establishes the presence of the doublet and resolves the conflicts. We find that there are six states in this excitation energy region, including a new state at E_x = 6410 ± 5 keV. The l-values leading to possible spin and parity assignments for all these states have been made using DWBA. We conclude however that only three of these six states may contribute to the production of ²⁶Al by the ²⁵Mg(p, γ) reaction in the MgAl cycle and the new structure of ²⁶Al reported here can substantially increase the production rate of ²⁶Al in stellar reactions.     

A study of the 26Mg(12C, 12B)26Al charge-exchange reaction

The reaction ²⁶Mg(¹²C, ¹²B)²⁶A1(5⁺, 3⁺) has been studied using a beam of 102 MeV of ¹²C. Shell-model, microscopic direct model and finite-range coupled reaction channel (CRC) calculations including recoil effects, have been performed, for comparison with the experimental data. DWBA calculations were performed for the intermediate states of interest in the ¹¹B + ²⁷Al and in the ¹³C + ²⁵Mg channels and these results were also compared with the experimental ones. The dominant reaction mechanism for ²⁶Mg(¹²C, ¹²B)²⁶Al(5⁺, 3⁺) appears to be the sequential mode.     

Recoil distance lifetime measurements in 26Mg and 26Al

Levels in ²⁶Mg and ²⁶Al were excited with the ²³Na + α reaction, and the recoil-distance method was used to determine the mean lives of the following levels: ²⁶Mg, 3.59 MeV (9.6 ± 1.2ps) and 3.94 MeV (1.38 ± 0.11 ps); ²⁶Al, 1.76 MeV (6.4 ± 0.4 ps) and 2.072 MeV (1.00 ± 0.10ps). The deduced values are compared to previous measurements by the Doppler-shift attenuation method.     

The decay of 174Tm and mixing of the Kπ = 5− two-quasiparticle states in 174Yb

The decay of 5.4 min ¹⁷⁴Tm has been investigated using Ge(Li) spectrometers in singles and coincidence measurements. A total of 43 γ-ray transitions, 26 of them not reported before, have been observed following the decay of ¹⁷⁴Tm. All transitions could be placed in a level scheme comprising 19 excited states of ¹⁷⁴Yb. The Nilsson model has been used to interpret the level structure. The mixing of two-quasineutron and two-quasiproton states is studied and the experimental mixing matrix element is compared with the results of theoretical calculations.     

The excitation function of the 13C(α, n)16O reaction and its astrophysical application

Neutron-liberating reactions as well as neutron absorbing processes play important parts in the synthesis of elements in a star and in the different phases of its life sequence. Thus the ¹³C(α, n)¹⁶O reaction is of interest for instance in connection with processes such as hydrostatic and explosive burning, as well as in the synthesis of oxygen and other light elements. A good knowledge of the energy dependence of the cross section of the alpha-carbon reaction is evidently of importance. In the present work the neutron yield from a thick ¹³C target was measured for α-particles in the energy range 0.60 to 1.15 MeV with a sensitive 4π neutron detector. Stellar temperatures between 3.5 and 9.2 × 10⁸ K are involved in this energy region. The observed neutron yield curve was used to determine astrophysical cross section factors S(E) as well as parameters for the 1.056 MeV resonance. Starting from these quantities, an expression for the mean lifetime of ¹³C nuclei interacting with helium was derived.     

Statistical model analysis of the 12C(14N, α) reaction and coherence widths in 26Al

The ¹²C(¹⁴N, α)²²Na reaction was studied at bombarding energies between 22 and 39.2 MeV (lab) and a lab angle of 7°. Average coherence widths of states in the compound nucleus ²⁶Al populated in the reaction were obtained from excitation functions of twenty states or unresolved multiplets measured for states in ²²Na. From these data and Hauser-Feshbach predictions, values were determined for the level density parameters and for the effective moment of inertia of ²⁶Al. The critical angular momentum for the reaction was determined by comparing ratios of cross sections for excited states of ²²Na with Hauser-Feshbach predictions.     

Beta decays of 25Na, 25Al and 29Al

The radioactivities ²⁵Na, ²⁵Al, and ²⁹Al were produced in the ²³Na(t, p)²⁵Na, ²⁴Mg(d, n)²⁵Al, and ²⁷Al(t, p)²⁹Al reactions using a 3.5 MV Van de Graaff. γ-radiations were measured by means of a target-transfer system and a Ge(Li) detector with or without Compton suppression. Decay schemes derived for ²⁵Na and ²⁹Al are in general agreement with earlier results, but with improved accuracy of branching ratios and much sharper limits on the intensities of certain unobserved β- and γ-ray transitions. Precision measurements of the energies of principal γ-rays gave results in keV for the listed decaying bodies as follows: ²⁵Na ? 1611.716(11); ²⁵Al ? 1611.708(11); and ²⁹Al ? 1273.361(9). The energy determinations of the ²⁵Mg 1612 keV γ-transition measured in the decays of ²⁵Na and ²⁵Al differ by 8 ± 9 eV.     

Lifetime measurements in 29 Al

The lifetimes of the first six excited states of ²⁹Al have been measured by the DSA method with two different reactions,²⁶Mg(α, p)²⁹Al and²⁷Al(t, p)²⁹Al. The recoil distance method was also used to remeasure the mean lifetime of the first excited state, leading to a value τ_m = 6.5 ± 0.5 ps. Experimental results are compared with shell model calculations.     

Short lifetimes in 26Al

Mean lifetimes of levels in ²⁶Al have been measured using the Doppler-shift attenuation (DSA) method and the reaction ²⁵Mg(p, γ)²⁶Al. The lifetime values or limits were determined for 34 bound levels below the excitation energy of 6 MeV; the lifetimes of 13 levels and upper limits of 3 levels are reported for the first time. For the effective stopping of recoils, the targets were prepared by implanting ²⁵Mg into Ta backings. The Monte Carlo method and the experimental stopping power were used in the DSA analysis.