Karim Ghorbani

eta to 3 pi at Two Loops In Chiral Perturbation Theoryeta to 3 pi at Two Loops In Chiral Perturbation Theory

We calculate the decay eta to3 pi at next-to-next-to-leading order or order p 6 in Chiral Perturbation Theory. The corrections are somewhat larger than was indicated by dispersive estimates. We present numerical results for the Dalitz plot parameters, the ratio r of the neutral to charged decay and the total decay rate. In addition we derive an inequality between the slope parameters of the charged and neutral decay. The experimental charged decay rate leads to central values for the isospin breaking quantities R=42.2 and Q=23.2.We calculate the decay η→3π at next-to-next-to-leading order or order p6 in Chiral Perturbation Theory. The corrections are somewhat larger than was indicated by dispersive estimates. We present numerical results for the Dalitz plot parameters, the ratio r of the neutral to charged decay and the total decay rate. In addition we derive an inequality between the slope parameters of the charged and neutral decay. The experimental charged decay rate leads to central values for the isospin breaking quantities R = 42.2 and Q = 23.2.

The LHC upper bounds for pp → diboson, tt̄ cross-section on fermionic dark matter

The ATLAS report in August 2016 provided an upper limit for the pp →diboson and tt cross-sections. We consider a pseudoscalar-mediated fermionic dark matter together with gluon and photon effective operators interacting with the pseudoscalar. Choosing the resonance mass being mρ = 200, 750 GeV and 2 TeV, beside the relic density and the invisible Higgs decay constraints we constrain more the space of parameters with the diboson and tt cross-section upper bounds. We finally provide some benchmarks consistent with all the constraints. Having exploited a pseudoscalar mediator, the DM-nucleon cross-section is velocity suppressed so that the model evades easily the bounds put by the future direct detection experiments such as XENON1T.

Scalar Dark Matter in Scale Invariant Standard Model

A bstractWe investigate single and two-component scalar dark matter scenarios in classically scale invariant standard model which is free of the hierarchy problem in the Higgs sector. We show that despite the very restricted space of parameters imposed by the scale invariance symmetry, both single and two-component scalar dark matter models overcome the direct and indirect constraints provided by the Planck/WMAP observational data and the LUX/Xenon100 experiment. We comment also on the radiative mass corrections of the classically massless scalon that plays a crucial role in our study.

Low Q2 proton structure function, using gluon and pseudoscalar meson clouds in the constituent quark framework

The idea of the meson cloud approach in the chiral quark model has been extended to include gluon cloud in order to achieve the parton densities in the nucleon, based on the constitute quark framework. The splitting function of the quark to the quark-meson and quark-gluon at low Q value are used to obtain parton densities in the constituent quark. The phenomenological constituent model is employed to extract the parton distributions in the proton at low Q value. Since we have access to the parton densities at low Q, we are able to obtain F2(x,Q ) structure function at low Q value. The result is in good agreement with available experimental data and some theoretical models. To confirm the validity of our calculations, the fraction of total momentum of proton which is carried by gluon at high Q and also the Gottfried sum rule are computed. The results are in good agreement with what are expected.The idea of the meson cloud approach in the chiral quark model has been extended to include a gluon cloud in order to model the parton densities in the nucleon, based on the constituent quark framework. The splitting functions of a quark to quark–meson and quark–gluon at low Q 2 values are used to obtain parton densities in the constituent quark approach. The phenomenological constituent model is employed to extract the parton distributions in the proton. Since we have access to the parton densities at low Q 2 , we are able to obtain the F2(x, Q 2 ) structure function at low Q 2 values. The result is in good agreement with the available experimental data and some theoretical models. To confirm the validity of our calculations, the fraction of the total momentum of the proton which is carried by gluons at high Q 2 and the Gottfried sum rule are computed. The results are in good agreement with those expected.

Chiral and volume extrapolation of pion and kaon electromagnetic form factor within SU(3) ChPT

We calculate the pion and kaon electromagnetic form factors in finite volume for a generic momentum transfer in space-like region, using SU(3) chiral perturbation theory. To this end, we first find the hadronic matrix element in a new form which is suitable for our calculation in finite volume. We present our numerical findings for the chiral behavior and finite volume corrections and compare these for pion and kaon form factors. As a result, for the pion electromagnetic form factor we find the finite volume correction

Two loop partially quenched and finite volume chiral perturbation theory results

\Delta F^{\pi}_{em} = 0.0041

DAMPE electron-positron excess in leptophilic Z′ model

at momentum transfer

Kaon semi-leptonic form factor at zero momentum transfer in finite volume

q^2 = -0.1358

Scalar split WIMPs in future direct detection experiments

and for the kaon form factor

Two-portal Dark Matter

\Delta F^{K}_{em} = 0.0029