arXiv subjects

K. H. Phan

Publications and source records attributed to K. H. Phan.

3 recordsLinked to original sources

arXiv2018

Scalar one-loop Feynman integrals with complex internal masses revisited

In this paper, we study systematically scalar one-loop two-, three-, and four-point Feynman integrals with complex internal masses. Our analytic results presented in this report are valid for both real and complex internal masses. The calculations are then implemented into a {\tt Mathematica} (version $9$) package and {\tt FORTRAN} program. Our program is cross-checked numerically with {\tt LoopTools} (version $2.14$) in real as well as complex internal masses. We find a perfect agreement between our results and {\tt LoopTools} for all cases. Additionally, this work is applied for evaluating scalar one-loop Feynman integrals developed leading Landau singularities which may appear in real scattering processes at colliders. Last but not least, the method used in this report can also extend to evaluate tensor one-loop integrals. Therefore, this may open a new approach which can solve the inverse Gram determinant problem analytically.

hep-ph↗

arXiv2017

Scalar one-loop four-point Feynman integrals with complex internal masses

Based on the method in Refs.~{\tt [D.~Kreimer, Z.\ Phys.\ C {\bf 54} (1992) 667} and {\tt Int.\ J.\ Mod.\ Phys.\ A {\bf 8} (1993) 1797]}, we present analytic results for scalar one-loop four-point Feynman integrals with complex internal masses. The results are not only valid for complex internal masses, but also for real internal mass cases. Different from the traditional approach proposed by G. 't Hooft and M. Veltman in the paper {\tt[Nucl.\ Phys.\ B {\bf 153} (1979) 365]}, this method can be extended to evaluate tensor integrals directly. Therefore, it may open a new approach to cure the inverse Gram determinant problem analytically. We then implement the results into a computer package which is {\tt ONELOOP4PT.CPP}. In numerical checks, one compares the program to {\tt LoopTools version} $2.12$ in both real and complex mass cases. We find a perfect agreement between the results generated from this work and {\tt LoopTools}.

hep-ph↗

arXiv2016

One loop contributions to neutral Higgs decay h-->mu tau

In calculating one-loop contributions to amplitudes of the lepton-flavor violating decays of the neutral Higgses (LFVHD) to different flavor charged leptons, the analytic expressions can be written in term of Passarino-Veltman functions. Then, they can be computed numerically by Looptools [1]. Another approach is using suitable analytic expressions established for just this particular case. We compare numerical results obtained from Looptools and those computed by different expressions that have been applied recently. Then we derive the preferable ones that are applicable for the large ranges of free parameters introduced in the models beyond the Standard Model (SM). For illustration, the LFVHD in a simple model, which has been discussed recently, will be investigated more precisely.

hep-ph↗