Molecular two-centre integrals between 2 pπ and 3 pπ atomic orbitals

The evaluation of two-centre Coulomb-penetration and exchange-penetration integrals is discussed. All possible penetration integrals between 2pπ and 3pπ atomic orbitals exponent α are reduced analytically and tabulated for α = 1·00 (0·25) 10·00.     

The 8π spectrometer

The 8π spectrometer installed at the TRIUMF-ISAC radioactive beam facility provides a powerful and versatile detection system for radioactive decay, allowing measurements of γ rays and conversion electrons with high resolution, tagging on β particles, and fast-timing measurements. The facility supports a wide program of research in the fields of nuclear structure, nuclear astrophysics and fundamental symmetries with low-energy radioactive beams.     

e/π Separation analysis from L3 Calorimeter Beam Test

The L3 calorimeter beam test data were analyzed.An e/π separation scheme including "key cut" and "Δ cut" is suggested.We show that,using the scheme,in the energy range 4—20GeV,e/π separation is better than 93.7%.     

Low-Energy Kπ Phase Shifts in Chiral SU(3) Quark Model

The low-energy region kaon-pion S- and P-wave phase shifts with isospin I = 1/2 and I = 3/2 are dynamically studied in the chiral SU(3) quark model by solving a resonating group method equation. The model parameters are taken to be the values fitted by the energies of the baryon ground states and the kaon-nucleon elastic scattering phase shifts of different partial waves. As a preliminary study the s-channel q(-q) annihilation interactions are not included since they only act in the very short range and are subsequently assumed to be unimportant in the low-energy domain. The numerical results are in qualitative agreement with the experimental data.     

Cusps in KL→3π decays

The pronounced cusp in K→3π decays which is generated by the pion mass difference is directly related to the ππS-wave scattering lengths. We apply a nonrelativistic effective field theory framework to evaluate the amplitudes for K_L→3π decays in a systematic manner. Electromagnetic effects in the neutral channel K_L→3π⁰ are also discussed.     

Low-Energy Kπ Phase Shifts in Chiral SU（3） Quark Model

The low-energy region kaon-pion S- and P-wave phase shifts with isospin I = 1/2 and I = 3/2 are dynamically studied in the chiral SU（3） quark model by solving a resonating group method equation. The model parameters are taken to be the values fitted by the energies of the baryon ground states and the kaon-nucleon elastic scattering phase shifts of different partial waves. As a preliminary study the s-channel qq^- annihilation interactions are not included since they only act in the very short range and are subsequently assumed to be unimportant in the low-energy domain. The numerical results are in qualitative agreement with the experimental data.     

Electromagnetic effects and scattering lengths extraction from experimental data on K → 3π decays

The final state interactions in K ^± → π^±π⁰π⁰ decays are considered using the methods of nonrelativistic quantum mechanics. It is shown how to take into account the largest electromagnetic effect in the analysis of experimental data using the amplitudes calculated earlier. The relevant expressions for amplitude corrections valid both above and below the two charged pions production threshold , including the average effect for the threshold bin, are proposed. These formulae can be used in the procedure of pion scattering lengths measurement from spectrum. The text was submitted by the authors in English.     

Measuring dynamical K/π and p/π fluctuations in AuAu collisions from the STAR experiment

Results from new measurements of dynamical K/?? and p/?? ratio fluctuations are presented. Dynamical fluctuations in global conserved quantities such as baryon number, strangeness, or charge may be observed near a QCD critical point. The STAR experiment has previously acquired data in AuAu collisions at the energies $\sqrt {s_{NN} }$ = 200, 130, 62.4, and 19.6 GeV and CuCu collisions at $\sqrt {s_{NN} }$ = 200, 62.4, and 22.4 GeV. The commencing of a QCD critical point search at RHIC has extended the reach of possible measurements of dynamical K/?? and p/?? ratio fluctuations from AuAu collisions to lower energies. New results are compared to previous measurements and to theoretical predictions from the UrQMD model.     

SU(3)×SU(3) symmetry breaking, (8, 8) Model and theη→3π decay

It is shown that the (8, 8) model and explicitηπ ⁰ mixing successfully explain theη→3π decay width whereas the decay width calculated from the mass difference is about one order less than the experimental value.     

The ω(782)→5π decay

The partial widths of the decays ω→2π⁺2π^?π⁰ and π⁺π^?3π⁰ are evaluated and their excitation curves in e ⁺ e ^? annihilation are obtained.     

Polarization phenomena in NN ↔ Dπ reactions

On the basis of a relativistic approach, NN ? Dπ reactions are analyzed in detail. The coherent sum of one-nucleon-exchange and pion-rescattering diagrams is calculated. It is shown that polarization observables are highly sensitive to off-mass-shell effects within the deuteron and that some of these observables can change sign upon taking these effects into account. The effect of the deuteron P wave is also investigated. The results obtained by calculating a full set of observables are compared with experimental data on the reaction pp → Dπ ⁺.     

Rhoprimes in 6π states from materialisation of photons

Data on 6π states produced ine ⁺ e ^? annihilation and diffractive photoproduction are analysed together. The simplest interpretation is in terms of two major contributions from resonances. One, in the isotopic spin symmetry state (321), peaks at 2.1 GeV and the other, in the isotopic spin symmetry state (411), peaks at 1.8 GeV. The former is a candidate for a new ρ^′-meson. The latter could be an additional ρ^′-meson, but the possibility that it is a manifestation of the known ρ ₂ ^′ -meson, distorted by threshold effects, cannot be ruled out.     

Theoretical investigation of the backbone···π and π···π stacking interactions in substituted-benzene||3-methyl-2′-deoxyadenosine: a perspective to the DNA repair

The π-stacking effects of substituted benzenes on the N-glycosidic bond strength of 3-methyl-2'-deoxyadenosine (3-MDA) were studied by quantum mechanical calculations. Although all substituents enhance the stacking interactions, enhancement is higher for the electron-donating (ED) substituents. When the overall binding energy is separated into the π···π (ΔE_π···π) and backbone···π (ΔE_bb···π) contributions, the ED and electron-withdrawing (EW) substituents increase those contributions, respectively. Both the ED and EW substituents decrease the distance between the centres of stacked rings, while the EW ones increase the N-glycosidic bond length. The electron charge density calculated at the C--N bond critical point (ρ_C–N) is in linear correlation with the backbone···π interaction, not with the π···π interaction. This study also shows that the charge transfer from X-Ben to 3-MDA is in linear correlation with the ΔE_π···π and the change in the charge on the sugar ring is in better accordance with the backbone···π interaction. The N7 proton affinity (PA_N7), with a key role in the depurination process, is highly affected by the π···π interactions. Thus, both interactions must be considered because of the balance between the backbone···π and π···π contributions in these biomolecular systems.     

K→π form factors with reduced model dependence

Using partially twisted boundary conditions we compute the K→π semi-leptonic form factors in the range of momentum transfers $0\lesssim q^{2}\leq q^{2}_{\max}=(m_{K}-m_{\pi})^{2}$ in lattice QCD with N _f =2+1 dynamical flavours. In this way we are able to determine $f_{+}^{K\pi}(0)$ without any interpolation in the momentum transfer, thus eliminating one source of systematic error. This study confirms our earlier phenomenological ansatz for the strange quark mass dependence of the scalar form factor. We identify and estimate potentially significant NNLO effects in the chiral expansion that guides the extrapolation of the data to the physical point. Our main result is $f_{+}^{K\pi}(0)=0.9599(34)(^{+31}_{-47})(14)$ , where the first error is statistical, the second error is due to the uncertainties in the chiral extrapolation of the lattice data and the last error is an estimate of potential discretisation effects.     

Oscillating gap 2π pulse in resonantly absorbing lattice

The interaction of a laser pulse with resonant Bragg lattice is studied theoretically for arbitrary initial conditions on the field, inverse population, and polarization of a medium. It is shown that the oscillating 2π self-induced transparency Bragg pulse can form if the Bragg conditions are exactly met. Various regimes are described for the oscillation dynamics of the gap 2π pulse.     

软π Skyrme模型和核子的静态性质

本文在Skyrme模型的基础上引进软π效应, 推出了新的N、Δ质量分裂公式, 计算结果表明, 软π场的扰动, 对核子等一些强子的基态能量是不可忽视的, 得到的结果比文献[1]有较明显的改进.