119961291
Octupole Vibrations with K =1 and 2 in Superconducting, Superdeformed Nuclei
We calculate the response functions for octupole vibrations in superdeformed nuclei by means of the RPA using a large configuration space composed of 9 major shells. The strongly collective octupole vibrations with K = 1 and 2 are predicted to appear very low in excitation energy, as well as those with K =0, if an appreciable amount of pairing correlation is present in superdeformed nuclei. Numerical examples are presented for 192Hg and 144Gd .
118593886
Method to circumvent the neutron gas problem in the BCS treatment for nuclei far from stability
Extending the Kruppa's prescription for the continuum level density, we have recently improved the BCS method with seniority-type pairing force in such a way that the effects of discretized unbound states are properly taken into account for finite depth single-particle potentials. In this paper, it is further shown, by employing the Woods-Saxon potential, that the calculation of spatial observables, such as nuclear radius, converges as increasing the basis size in the harmonic oscillator expansion. Namely the disastrous problem of a ''particle gas'' surrounding nucleus in the BCS treatment can be circumvented. In spite of its simplicity, the new treatment gives similar results to those by more elaborate Hartree-Fock-Bogoliubov calculations, e.g., it even mimics the pairing antihalo effect. The obtained results as well as the reason of convergence in the new method are investigated by a variant of the Thomas-Fermi approximation within the limited phase space which corresponds to the harmonic oscillator basis truncation.
119360363
Microscopic structure of high-spin vibrational states in superdeformed A=190 nuclei
Microscopic RPA calculations based on the cranked shell model are performed to investigate the quadrupole and octupole correlations for excited superdeformed (SD) bands in even-even A=190 nuclei. The K = 2 octupole vibrations are predicted to be the lowest excitation modes at zero rotational frequency. The Coriolis coupling at finite frequency produces different effects depending on the neutron and proton number of nucleus. The calculations also indicate that some collective excitations may produce moments of inertia almost identical to those of the yrast SD band. An interpretation of the observed excited bands invoking the octupole vibrations is proposed, which suggests those octupole vibrations may be prevalent in even-even SD A=190 nuclei.
9137480
Wobbling motion in triaxial superdeformed nuclei
We discuss some characteristic features of the wobbling motion excited on the triaxial superdeformed Lu nucleus. We show how these features are connected to the moments of inertia microscopically calculated by means of the quasiparticle RPA in the rotating frame.
118875141
Dynamical moments of inertia associated with wobbling motion in the triaxial superdeformed nucleus
Abstract.The three moments of inertia associated with the wobbling mode built on the triaxial superdeformed states in the Lu-Hf region are investigated by means of the cranked shell model plus random-phase approximation to the configurations with aligned quasiparticle(s). The result indicates that it is crucial to take into account the direct contribution to the moments of inertia from the aligned quasiparticle(s) so as to realize $\mathcal{J}_x > \mathcal{J}_y$ in positive-$\gamma$ shapes.
119098407
Microscopic Calculation of the Wobbling Excitations Employing the Woods-Saxon Potential as a Nuclear Mean-Field
The wobbling excitations of the triaxial superdeformed (TSD) bands in the Lu and Hf region are studied by the microscopic framework of the cranked mean-field and the randomphase approximation (RPA). In contrast to the previous works, where the Nilsson potential was used, the more realistic Woods-Saxon potential is employed as a nuclear mean-field. It is pointed out that the original formulation should be slightly modified for general meanfield like the Woods-Saxon potential. The wobbling-like RPA solutions have been found systematically in the nuclei studied and their characteristic properties are investigated in detail. This confirms the wobbling phonon excitations in TSD nuclei from the microscopic calculations. The result of B(E2) values indicates that the triaxial deformation is increasing as a function of spin in the observed TSD bands in 163 Lu. Subject Index: 210, 211, 212
15252744
Precise Numerical Evaluation of the Scalar One-Loop Integrals with the Infrared Divergence
We present a new approach for obtaining very precise integration results for infrared vertex and box diagrams, where the integration is carried out directly without performing any analytic integration of Feynman parameters. Using an appropriate numerical integration routine with an extrapolation method, together with a multi-precision lib rary, we have obtained integration results which agree with the analytic results to 10 digits even for such a very small photon mass as 10 150 GeV in the infrared vertex diagram.
28368514
Numerical computation of two-loop box diagrams with masses
Abstract A new approach is presented to evaluate multi-loop integrals, which appear in the calculation of cross-sections in high-energy physics. It relies on a fully numerical method and is applicable to a wide class of integrals with various mass configurations. As an example, the computation of two-loop planar and non-planar box diagrams is shown. The results are confirmed by comparisons with other techniques, including the reduction method, and by a consistency check using the dispersion relation.
118882824
Squark flavor mixing and CP asymmetry of neutral B mesons at LHCb
Abstract The CP violation of the neutral B meson is the important phenomenon to search for the new physics. The like-sign dimuon charge asymmetry observed by the D O Collaboration indicates the CP-violating new physics in the B s – B ¯ s mixing. On the other hand, LHCb observed the CP-violating asymmetry in B s 0 → J / ψ ϕ and B s 0 → J / ψ f 0 ( 980 ) , which is consistent with the SM prediction. However, there is still room for new physics of the CP violation. The CKMfitter has presented the allowed region of the new physics parameters taking account of the LHCb data. Based on these results, we discuss the effect of the squark flavor mixing on the CP violation in the B d and B s mesons. We predict asymmetries in the non-leptonic decays B d 0 → ϕ K S , B d 0 → η ′ K 0 , B s 0 → ϕ ϕ and B s 0 → ϕ η ′ .
73642094
LHCf plan for p-Pb forward particle measurement
LHCf is planning to measure very forward particle emission in the LHC p-Pb collisions foreseen at the end of 2012. The measurement is expected to constrain the nuclear effect in the forward particle emission relevant to the CR-Air interaction. Model discrimination power of this measurement is presented together with some detail in technical feasibility.
120353160
Forward photon energy spectrum at LHC 7 TeV p-p collisions measured by LHCf
Abstract The LHCf experiment is one of the LHC forward experiments. The aim is to measure the energy and the transverse momentum spectra of photons, neutrons and π 0 's at the very forward region (the pseudo-rapidity range of η > 8.4 ), which should be critical data to calibrate hadron interaction models used in the air shower simulations. LHCf successfully operated at s = 900 GeV and s = 7 TeV proton–proton collisions in 2009 and 2010. We present the first physics result, single photon energy spectra at s = 7 TeV proton–proton collisions and the pseudo-rapidity ranges of η > 10.94 and 8.81 η 8.9 . The obtained spectra were compared with the predictions by several hadron interaction models and the models do not reproduce the experimental results perfectly.