The radiative lifetime and the optical absorption cross section measurements of neodymium

Using the technique of laser induced fluorescence, we have obtained the experimental results that the radiative lifetime of the ~7K_3~o state and the optical absorption cross section of the transition ~5I_4~e→~7K_3~o of neodymium are 675±50ns and (1.48±0.74)×10~(-13)cm~2 respectively.     

K − absorption in nuclei by two and three nucleons

It will be shown that the peaks in the (Λp) and (Λd) invariant mass distributions, observed in recent FINUDA experiments and claimed to be signals of deeply bound kaonic states, are naturally explained in terms of K ^? absorption by two or three nucleons leaving the rest of the original nuclei as spectator. For reactions on heavy nuclei, the subsequent interactions of the particles produced in the primary absorption process with the residual nucleus play an important role. Our analyses leads to the conclusion that at present there is no experimental evidence of deeply bound K ^? state in nuclei. Although the FINUDA experiments have been done for reasons which are not supported a posteriori, some new physics can be extracted from the data.     

Photodetachment cross section of S^- in electric and magnetic fields＊

In this paper, the quantum-mechanical photodetachment cross section of S^- in uniform electric and magnetic fields at arbitrary angles is presented. It compares the quantum-mechanical cross section with the quantum source formalism cross section. The results show that at large angle, the two results have good agreements, however, with the decrease of the angles, they deviate obviously from each other. The reasons for this discrepancy are also discussed.     

On theB andJ/ψ cross section measurements at UA1 and CDF

We analyse the implications of the measurement ofB andJ/ψ inclusivep _t distributions performed in \(p\bar p\) collisions by the UA1 and CDF experiments.     

The density-and isospin-dependent ?-formation cross section and its decay width

The energy-, density-, and isospin-dependent ?-formation cross section σ_(Nπ→?)~* and ?-decay width are calculated based on the relativistic BUU approach in which the effective mass splitting of nucleon and ? baryons in isospin-asymmetric matter is considered by the inclusion of the δ meson exchange in the effective Lagrangian density and the density-dependent coupling constants of Hofmann et al. The results show that the σ_(Nπ→?)~* is decreased(increased) moderately with increasing density with(without)the consideration of medium modifications on pion mass. Meanwhile, if the invariant mass of the system is not far from the ?pole mass, the ?-decay width is also weakly dependent on density. The mass splitting effect of differently charged nucleon and ?baryons on σ_(Nπ→?)~* is found to be more obvious than that of pion mesons but much weaker than the mass splitting in the hard ?production channel NN → N?. Further, the largest mass-splitting influence is seen in the π~-p → ?~0 and π~+n → ?~+ channels but not in the production of ?~- and ?~(++) isobars.     

Pion pair production in γ-γ collisions at low energy and the born cross section

It is shown that (i) there is a severe constraint on σ(γγ→π⁺π⁻/σ_Born imposed by phenomenological theory and (ii) the low-mass π⁺π⁻ enhancement observed in the reaction γγ→π⁺π⁻ comes from interference between the Born term and the correction term.     

Regularized Green’s function and group of reflections in a cavity with triangular cross section

For a certain class of triangles (with angles proportional to π/N, N ≥ 3) we formulate the image method by making use of the group G _N generated by reflections with respect to three lines which form the triangle under consideration. A regularized Green’s function (which is employed in Casimir energy calculations) is obtained by classification of subgroups of G _N and corresponding fixed points in the triangle.     

Differential cross section and related integrals for the molière potential

The Molière potential is widely used in radiation damage simulation studies. It is not much used in analytical transport theory calculations because of the awkward expression for the differential cross section corresponding to the potential. We follow a two step process to obtain a useful cross section: adopting the Lindhard, Nielsen and Scharff (LNS) approximations in order to generate a simpler form of the Molière cross section and then creating a simple, easy-to-use, fit to that approximate form. Within the framework of the LNS treatment of atomic cross sections, our fit is accurate to 6%. Simple forms for the total cross section and several related quantities are presented.     

Unified approach to theJ/Ψ suppression and strangeness enhancement in high-energy nucleus-nucleus collisions

A picture of nuclear interactions at high energies (p _Lab100 GeV/c) is proposed, where the only essential difference between nucleon-neucleon and central nucleus-nucleus collisions is the size of the interaction zone. In both cases intermediate multi-parton systems are created, which achieve thermodynamical equilibrium with respect to characteristics of light quarks and gluons. The characteristics of heavier quarks are far from equilibrium ones in nucleon-nucleon collisions, but the degree of equilibration is substantially increased in central heavy-ion collisions. Therefore, the multi-parton systems produced in central nucleus-nucleus interactions can manifest themseleves as the quark-gluon plasma. A simple model based on this picture is formulated and confronted with the experimental data concerningJ/ suppression and strangeness yield enhancement, both revealed recently in central nucleus-nucleus collisions.This work was supported in part by the Deutsche Forschungsgemeinschaft under grant He 1283/3-1     

Color screening,absorption, and σ tot pp at LHC

We show that a growth of the proton-proton total cross section with energy can be entirely attributed to the purely perturbative mechanism. The infrared regularization at rather short distances R _c ? 0.3 fm allows extending the BFKL technique from deep inelastic to hadron-hadron scattering. With the inclusion of the absorption corrections our results are in agreement with the LHC data on σ _tot ^pp .     

Ψ′ and J/Ψ production in p-W,p-U and S-U interactions at 200 GeV/nucleon

Ψ′ and J/Ψ yields are compared in p-W, p-U and S-U interactions at 200 GeV/nucleon. Their ratio decreases from proton-t to sulphur-induced reactions. It also decreases in sulphur-induced reactions from peripheral to central collisions. This result could indicate that the Ψ′ and J/Ψ suppression mechanisms have different origins in p- and S-induced reactions.     

On the structure in the AN cross section at the ΣN threshold

The complexity of threshold phenomena is exemplified on a prominent and long-known case-the struc-ture in the ∧p cross section (invariant mass spectrum) at the ...     

Transverse-momentum dependence of J/Ψ production in nuclear collisions

The suppression of J/Ψ production at transverse moment p_⊥ < 2 GeV/c in central ¹⁶O+²³⁸U→Ψ+X at 200 A GeV has been interpreted as a possible signature of quark-gluon plasma formation. We show, however, that the observed p_⊥ dependence is consistent with extrapolations from p+A→Ψ+X data, and that quasielastic initial-state parton scattering together with final-state inelastic hadronic reactions may explain the preliminary data.     

40Ti β decay and the neutrino capture cross section of 40Ar

⁴⁰Ti β decay was studied at GANIL using the LISE3 spectrometer. A decay scheme was deduced from twenty-one observed β-delayed proton transitions feeding the ground and first excited states of ³⁹Ca. The ⁴⁰Ti half-life was found to be 51.7(6) ms. These results imply that the ICARUS ⁴⁰Ar detector has an effective absorption cross section for ⁸B solar neutrinos of 14.5(4) × 10⁻⁴³ cm²; 73% of the total cross section arises from Gamow-Teller transitions that were neglected in early estimates of the ICARUS efficiency.     

J/ψ production and absorption in high energy proton-nucleus collisions

Measured J/ψ production cross sections for 200 and 450 GeV/c protons incident on a variety of nuclear targets are analyzed within a Glauber framework which takes into account energy loss of the beam proton, the time delay of particle production due to quantum coherence, and absorption of the J/ψ on nucleons. The best representation is obtained for a coherence time of 0.5 fm/c, previously determined by Drell–Yan production in proton-nucleus collisions, and an absorption cross section of 3.6 mb, which is consistent with the value deduced from photoproduction of the J/ψ on nuclear targets.     

In-medium NN→NΔ cross section and its dependence on effective Lagrange parameters in isospin-asymmetric nuclear matter

The in-medium NN→N△ cross sections and its differential cross sections in isospin asymmetric nuclear medium are investigated in the framework of the one-boson exchange model by including isovector mesons, i.e., δand p mesons. Our results show that the in-medium NN→N△ cross sections are suppressed when the density increases, and the differential cross sections become isotropic with an increase in the density around the △ threshold energy. The isospin splitting on the medium correction factor, R =σ_(NN→N△)~*/σ_(NN→N△)~(free) is observed for different channels of NN→N△, especially around the threshold energy for all the effective Lagrangian parameters. By analyzing the selected effective Lagrangian parameters, our results show that the larger effective mass is, the weaker medium correction R is.     

Spherical and Deformed Shell Closures in Superheavy nuclei

The structure of superheavy nuclei has been studied using the macroscopic-microscopic model. The macroscopic energy was calculated with the continuous medium model in which the energy is expressed as a function of nucleon densities. The deformations and structures of superheavy nuclei were systematically investigated. Calculations reproduce well the available data of experimental α-decay energies and half-lives. The investigation of single-particle levels shows that the shell structure is deformation and isospin dependent. Potential-energy-surface calculations display that superheavy nuclei have in general harder shapes than the nuclei of other mass regions.