120050590
Numerical Approach to One-Loop Integrals
Two numerical methods are proposed for the calculation of one-loop scalar integrals. In the first method, the singularity is cancelled by the symmetrization of the integrand and the integration is done by a Monte-Carlo method. In the second one, after the transform of the integrand into a standard form, the integral is reduced into a regular numerical integral. These methods provide us practical tools to evaluate one-loop Feynman diagrams with desired numerical accuracy. They are extended to the integral with numerator and the treatment of the one-loop virtual correction to the cross section is also presented
54183358
Calculation of Single Top Quark Production in Electron-Positron Scattering
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.
15312798
Monte Carlo Approach to Radiative Corrections in Bhabha Scattering
§ 1. lntroduction It has become a common understanding that detailed theoretical predictions for e+ e- experiments should include the radiative corrections with multi-photon contribu­ tion. A well-known example is the significant modification of the apparent cross section around the Z-boson pole at LEP.ll The study of inclusive processes with multi-photon emission has led some authors to propose several kinds of Monte Carlo generators. 2 l In a pre~ious paper 3 l we have reported a new method for the Monte Carlo generator of multi-photon and have shown some results obtained via a computer progam written for muon pair production in e+ e- annihilation. This is a QED version of the parton shower model which has been studied extensively in QCD. In this paper we generalize this method to the Bhabha scattering by employing essen­ tially the same algorithm as that for muon pair production. It will be convenient to summarize the main features of the algorithm to generate photons. We rely on the technique to sum up all the collinear singularities, which plays an essential role in the parton shower model. 4 J The present model is limited to the leading logarithmic approximation, though there is no difficulty in principle to include the next-to-leading corrections. 5 l This approximation is reasonable as the QED coupling a is very small compared with that in QCD. Another remarkable feature is that the transverse momentum distribution of produced photons is derived correctly once one imposes the four-momentum conservation at each of branching vertices. 4 l This is a consequence of the branching, e±--> e±y, being aprocess of 1--> 2 bodies.
123615884
Automation of loop amplitudes in numerical approach
Abstract An automatic calculating system GRACE-L1 of one-loop Feynman amplitude is reviewed. This system can be applied to 2 to 2-body one-loop processes. A sample calculation of 2 to 3-body one-loop amplitudes is also presented.
121009792
QCD and Radiative Correction in Deep Inelastic Scattering
119213142
Pairing fluctuations and gauge symmetry restoration in rotating superfluid nuclei
Rapidly rotating nuclei provide us good testing grounds to study the pairing correlations; in fact, the transition from the superfluid to the normal phase is realized at high-spin states. The role played by the pairing correlations is quite different in these two phases: The static (BCS like mean-field) contribution is dominant in the superfluid phase, while the dynamic fluctuations beyond the mean-field approximation are important in the normal phase. The influence of the pairing fluctuations on the high-spin rotational spectra and moments of inertia is discussed.
199673909
Nuclear moments of inertia and wobbling motions in triaxial superdeformed nuclei
The wobbling motion excited on triaxial superdeformed nuclei is studied in terms of the cranked shell model plus random phase approximation. Firstly, by calculating at a low rotational frequency the \gamma-dependence of the three moments of inertia associated with the wobbling motion, the mechanism of the appearance of the wobbling motion in positive-\gamma nuclei is clarified theoretically -- the rotational alignment of the \pi i_{13/2} quasiparticle(s) is the essential condition. This indicates that the wobbling motion is a collective motion that is sensitive to the single-particle alignment. Secondly, we prove that the observed unexpected rotational-frequency dependence of the wobbling frequency is an outcome of the rotational-frequency dependent dynamical moments of inertia.
119162632
Non-Abelian Discrete Symmetries in Particle Physics
We review pedagogically non-Abelian discrete groups, which play an important role in the particle physics. We show group-theoretical aspects for many concrete groups, such as representations, their tensor products. We explain how to derive, conjugacy classes, characters, representations, and tensor products for these groups (with a finite number). We discussed them explicitly for $S_N$, $A_N$, $T'$, $D_N$, $Q_N$, $\Sigma(2N^2)$, $\Delta(3N^2)$, $T_7$, $\Sigma(3N^3)$ and $\Delta(6N^2)$, which have been applied for model building in the particle physics. We also present typical flavor models by using $A_4$, $S_4$, and $\Delta (54)$ groups. Breaking patterns of discrete groups and decompositions of multiplets are important for applications of the non-Abelian discrete symmetry. We discuss these breaking patterns of the non-Abelian discrete group, which are a powerful tool for model buildings. We also review briefly about anomalies of non-Abelian discrete symmetries by using the path integral approach.
14072723
A new microscopic approach to the rotational intensity relations: Application of the high-spin cranking formalism
Abstract The intensity relations for electromagnetic transition rates in the rotational coupling scheme have been a basic tool to understand the properties of nuclear collective rotations. In particular the correction terms to the leading-order relation give the response of the intrinsic motion to the Coriolis and centrifugal forces. We propose a simple and systematic method to calculate the matrix elements of intrinsic operators entering the generalized intensity relations that uses the microscopic cranking formalism. Examples are given to show the usefulness of the method.
122292360
SAMURAI spectrometer for RI beam experiments
Abstract A large-acceptance multiparticle spectrometer SAMURAI has been constructed at the RIKEN RI Beam Factory (RIBF) for RI beam experiments. It was designed primarily for kinematically complete experiments such as the invariant-mass spectroscopy of particle-unbound states in exotic nuclei, by detecting heavy fragments and projectile-rapidity nucleons in coincidence. The system consists of a superconducting dipole magnet, beam line detectors, heavy fragment detectors, neutron detectors, and proton detectors. The SAMURAI spectrometer was commissioned in March 2012, and a rigidity resolution of about 1/1500 was obtained for RI beams up to 2.4 GeV/c.