122376328
Automatic generation of Feynman graphs and amplitudes in QED
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.
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.
118595829
Full $\mathcal{O}(\alpha)$ electroweak radiative corrections to $e^+e^- \rightarrow e^+e^- \gamma$ at the ILC with GRACE-Loop
By using the GRACE-Loop system, we calculate the full $\mathcal{O}(\alpha)$ electroweak radiative corrections to the process $e^+e^- \rightarrow e^+e^- \gamma$, which is important for future investigations at the International Linear Collider (ILC). With the GRACE-Loop system, the calculations are checked numerically by three consistency tests: ultraviolet finiteness, infrared finiteness, and gauge-parameter independence. The results show good numerical stability when quadruple precision is used. In the phenomenological results, we find that the electroweak corrections to the total cross section range from $\sim -4\%$ to $\sim -21\%$ when $\sqrt{s}$ varies from $250$ GeV to $1$ TeV. The corrections also significantly affect the differential cross sections, which are a function of the invariant masses and angles and the final-particle energies. Such corrections will play an important role for the high-precision program at the ILC.
54183358
Calculation of Single Top Quark Production in Electron-Positron Scattering
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.
55415432
Forward physics with the LHCf experiment: a LHC contribution to cosmic-ray physics
LHCf is a small detector installed at LHC accelerator to measure neutral par- ticle flow in the forward direction of proton - proton (p - p) and proton - nucleus (p - A) interactions. Thanks to the optimal performance that has characterized the last years' running of the LHC collider, several measurements have been taken since 2009 in differ- ent running conditions. After data taking for p - p interactions at √ s = 900 GeV, 2.76 TeV and 7 TeV and proton - Lead nucleus (p - Pb) at √ sNN = 5.02 TeV (energy of a couple of projectile and target nucleons in their center of mass reference frame), LHCf is now going to complete its physics program with the 13 TeV p - p run foreseen in 2015. The com- plete set of results will become a reference data set of forward physics for the calibration and tuning of the hadronic interaction models currently used for the simulation of the atmospheric showers induced by very high energy cosmic rays. For this reason we think that LHCf is giving an important contribution for the study of cosmic rays at the highest energies. In this paper the experiment, the published results and the current status are reviewed.
119253051
Improved microscopic-macroscopic approach incorporating the effects of continuum states
The Woods-Saxon-Strutinsky method (the microscopic-macroscopic method) combined with the Kruppa prescription for positive-energy levels, which is necessary to treat neutron-rich nuclei, is studied to clarify the reason for its success and to propose improvements for its shortcomings. The reason why the plateau condition is met for the Nilsson model but not for the Woods-Saxon model is understood in a new interpretation of the Strutinsky smoothing procedure as a low-pass filter. Essential features of the Kruppa level density is extracted in terms of the Thomas-Fermi approximation modified to describe spectra obtained from diagonalization in truncated oscillator bases. A method is proposed, which weakens the dependence on the smoothing width by applying the Strutinsky smoothing only to the deviations from a reference level density. The BCS equations are modified for the Kruppa spectrum, which is necessary to treat the pairing correlation properly in the presence of a continuum. The potential depth is adjusted for the consistency between the microscopic and macroscopic Fermi energies. It is shown, with these improvements, that the microscopic-macroscopic method is now capable to reliably calculate binding energies of nuclei far from stability.
453979
S4 Flavor Model of Quarks and Leptons
We present an S4 flavor model to unify quarks and leptons in the framework of the SU(5) GUT. Three generations of 5-plets in SU(5) are assigned to be 31 of S4 while the first and the second generations of 10-plets in SU(5) are assigned to be 2 of S4 ,a nd the third generation of 10-plet is to be 11 of S4. Right-handed neutrinos are also assigned to be 2 for the first and second generations and 11 for the third generation, respectively. Taking vacuum alignments of relevant gauge singlet scalars, we predict the quark mixing as well as the tri-bimaximal mixing of neutrino flavors. Especially, the Cabbibo angle is predicted to be 15 ◦ in the limit of the vacuum alignment. We can improve the model to predict observed CKM mixing angles.
16491530
Diabatic Mean-Field Description of Rotational Bands in Terms of the Selfconsistent Collective Coordinate Method
Diabatic description of rotational bands provides a clear-cut picture for understanding the back-bending phenomena, where the internal structure of the yrast band changes dramatically as a function of angular momentum. A microscopic framework to obtain the diabatic bands within the mean-field approximation is presented by making use of the selfconsistent collective coordinate method. Applying the framework, both the ground state rotational bands and the Stockholm bands are studied systematically for the rare-earth deformed nuclei. An overall agreement has been achieved between the calculated and observed rotational spectra. It is also shown that the inclusion of the double-stretched quadrupole-pairing interaction is crucial to obtain an overall agreement for the even-odd mass differences and the rotational spectra simultaneously.
28690711
Deviations from tri-bimaximality and quark-lepton complementarity
We study deviations from tri-bimaximality (TBM) and quark-lepton complementarity (QLC) in a model-independent way. The current neutrino experimental data is well approximated by tri-bimaximal generation mixing but the QLC relations are not satisfied with each data of 1σ level. This means that there exist deviations from the complementarity. The same fact for the TBM might be checked in the future neutrino experiments. We discuss such deviations from the TBM and QLC, simultaneously. A new ratio between the deviations is introduced, and some interesting points are presented. We also show predicted correlations among leptonic mixing angles at the points.