Chiral quark models and their applications

We give an overview of chiral quark models, both for the pure light sector and the heavy-light sector. We describe how such models can be bosonized to obtain welWe give an overview of chiral quark models, both for the pure light sector and the heavy-light sector. We describe how such models can be bosonized to obtain well known chiral Lagrangians which can be inferred from the symmetries of QCD alone. In addition, we can within these models calculate the coefficients of the various pieces of the chiral Lagrangians. We discuss a few applications of the models, in particular, \bbar mixing and processes of the type $B \to D \bar{D}$, where $D$ might be both pseudoscalar and vector. We suggest how the formalism might be extended to include light vectors ($\rho,\omega,K^*$), and heavy to light transitions like $B \to \pi$. l known chiral Lagrangians which can be inferred from the symmetries of QCD alone. In addition, we can within these models calculate the coefficients of the various pieces of the chiral Lagrangians. We discuss a few applications of the models, in particular, \bbar mixing and processes of the type $B \to D \bar{D}$, where $D$ might be both pseudoscalar and vector. We suggest how the formalism might be extended to include light vectors ($\rho,\omega,K^*$), and heavy to light transitions like $B \to \pi$.Comment: 37 pages, 16 figures. Dedicated to the memory of Prof. D. Tadic, Submitted to Fizika B, Zagre

The Isgur-Wise Function within a Modified Heavy-Light Chiral Quark Model

We consider the Isgur-Wise function xi(omega) within a new modified version of a heavy-light chiral quark model. While early versions of such models gave too small absolute value of the slope, namely xi'(1) of about -0.4 to -0.3, we show how extended version(s) may lead to values around -1, in better agreement with recent measurements. This is obtained by introducing a new mass parameter in the heavy quark propagator. We also shortly comment on the consequences for the decay modes B --> D D-bar.Comment: 20 pages, 7 PS figure, LaTe

Electric dipole moment of the neutron in Two Higgs Doublet Models with flavor changing

I consider contributions to the neutron electric dipole moment within Two Higgs Doublet Models which allow for small flavor changing neutral Higgs couplings. In a previous paper, I considered flavor changing interactions for the Standard Model Higgs boson to first order in the flavor changing coupling. In that paper I found that the obtained value of the neutron electric dipole moment were below the present experimental limit, given previous restrictions on such couplings. Because this was an effective theory, the result depended on an ultraviolet cut off $\Lambda$, parametrized as $ln(\Lambda^2)$. In the present paper I demonstrate that, when going to Two Higgs Doublet Models, the result stays the same as in the previous paper, up to $M_{SM}^2/M_H^2$ corrections, where $M_{SM}$ is the mass of the top-quark or the $W$-boson. $M_H$ is the mass of the heavy neutral scalar Higgs-boson $H$ which is much heavier than the light neutral Higgs boson $h$ with mass $M_h$. In the limit $M_H^2 \gg M_h^2$, the $ln(\Lambda^2)$ behaviour in the previous paper is replaced by $ln(\widetilde{M_H}^2)$, where $\widetilde{M_H}$ is of order $M_H$. I also explain how some divergences due to exchange of the pseudoscalar Higgs $A$ are cancelled by similar contributions from the scalar heavy Higgs $H$, and that these contributions, and finite contributions from $A$-exchange, are suppressed.Comment: 23 pages, 4 figures. arXiv admin note: text overlap with arXiv:1611.0777

Building the Standard Model Historical and Qualitative Aspects

Without going to the details, I give a short, qualitative and historical description of the development of the Standard Model, from quantum electrodynamics, further through quantum chromodynamics, then to weak interactions with parity- and CP-violation, ending up with electroweak symmetry breaking and the Higgs boson. The presentation is based on my own experiences from the late 1960's up to the discovery of the Higgs boson. It is mainly meant for students at master level, and at some points it is presented somewhat different from standard textbook presentations.Comment: 44 pages, 21 figure

New Dipole Penguin Contribution to K --> pi pi decays

We point out that the standard chromomagnetic penguin dipole operator has a counterpart corresponding to off-shell momenta for external quarks. By employing the chiral quark model, we show that this new dipole penguin operator has the same bosonisation as the standard Q_6 operator. Accordingly, this new operator enlarges by ~ 5 % the referent Q_6 contribution, which gives the dominant contribution to the CP-violating ratio epsilon'/epsilon and also gives an important contribution to the Delta I = 1/2 amplitude.Comment: 17 pages, 1 PS figure, LaTeX, corresponds to published versio