arXiv subjects

A. Flachi

Publications and source records attributed to A. Flachi.

10 recordsLinked to original sources

arXiv2003

A Kinematically Complete Analysis of the CLAS data on the Proton Structure Function $F_2$ in a Regge-Dual model

The recently measured inclusive electron-proton cross section in the nucleon resonance region, performed with the CLAS detector at the Thomas Jefferson Laboratory, has provided new data for the nucleon structure function $F_2$ with previously unavailable precision. In this paper we propose a description of these experimental data based on a Regge-dual model for $F_2$. The basic inputs in the model are nonlinear complex Regge trajectories producing both isobar resonances and a smooth background. The model is tested against the experimental data, and the $Q^2-$ dependence of the moments is calculated. The fitted model for the structure function (inclusive cross section) is a limiting case of the more general scattering amplitude equally applicable to deeply virtual Compton scattering (DVCS). The connection between the two is discussed.

hep-ph↗

arXiv2003

Generalized distribution amplitudes: new tools to study hadrons' structure and interactions

A non-perturbative approach to Generalized Parton Distributions, and to Deeply Virtual Compton Scattering in particular, based on off mass shell extension of dual amplitudes with Mandelstam analyticity (DAMA) is developed with the spin and helicity structure as well as the threshold behavior accounted for. The model is tested against the data on deep inelastic electron-proton scattering from JLab.

hep-ph↗

arXiv2003

Quantum self-consistency of $AdS \times Σ$ brane models

Continuing on our previous work, we consider a class of higher dimensional brane models with the topology of $AdS_{D_1+1} \times Σ$, where $Σ$ is a one-parameter compact manifold and two branes of codimension 1 are located at the orbifold fixed points. We consider a set-up where such a solution arises from Einstein-Yang-Mills theory and evaluate the one-loop effective potential induced by gauge fields and by a generic bulk scalar field. We show that this type of brane models resolves the gauge hierarchy between the Planck and electroweak scales through redshift effects due to the warp factor $a=e^{-πkr}$. The value of $a$ is then fixed by minimizing the effective potential. We find that, as in the Randall Sundrum case, the gauge field contribution to the effective potential stabilises the hierarchy without fine-tuning as long as the laplacian $Δ_Σ$ on $Σ$ has a zero eigenvalue. Scalar fields can stabilise the hierarchy depending on the mass and the non-minimal coupling. We also address the quantum self-consistency of the solution, showing that the classical brane solution is not spoiled by quantum effects.

hep-th↗

arXiv2002

Explicit model realizing parton-hadron duality

An explicit model realizing parton-hadron duality and fitting the data is suggested. Complex nonlinear Regge trajectories are important ingredients of the model. The inclusion of $Δ$ and $N^*$ trajectories should account for all resonances in the direct channel. The exotic trajectory is responsible for the smooth background.

hep-ph↗

arXiv2001

Quantized bulk scalar fields in the Randall-Sundrum brane-model

We examine the lowest order quantum corrections to the effective action arising from a quantized real scalar field in the Randall-Sundrum background spacetime. The leading term is the familiar vacuum, or Casimir, energy density. The next term represents an induced gravity term that can renormalize the 4-dimensional Newtonian gravitational constant. The calculations are performed for an arbitrary spacetime dimension. Two inequivalent boundary conditions, corresponding to twisted and untwisted field configurations, are considered. A careful discussion of the regularization and renormalization of the effective action is given, with the relevant counterterms found. It is shown that the requirement of self-consistency of the Randall-Sundrum solution is not simply a matter of minimizing the Casimir energy density. The massless, conformally coupled scalar field results are obtained as a special limiting case of our results. We clarify a number of differences with previous work.

hep-th↗

arXiv2000

Higgs mechanism in the Randall-Sundrum model

We consider the dimensional reduction of a bulk scalar field in the Randall-Sundrum model. By allowing the scalar field to be non-minimally coupled to the spacetime curvature we show that it is possible to generate spontaneous symmetry breaking on the brane.

hep-th↗

arXiv2000

Measurability of the non-minimal coupling

The "measurability" of the non-minimal coupling is discussed in the context of the effective field theory of gravity. Although there is no obvious motive for excluding a non-minimal scalar coupling from the theory, we conclude that for reasonable values of the coupling constant it makes only a very small correction.

hep-th↗

arXiv1999

Triple Pomeron and Proton Diffraction Dissociation

We consider proton diffraction dissociation in the dipole Pomeron model, where the Pomeron is represented by a double pole in the $J-$plane, and show that unitarity can be satisfied without decoupling of the triple Pomeron vertex. Differential and total diffractive cross sections for the reaction $\bar{p}+p \to \bar{p}+X$ are analyzed and reproduced in this model.

hep-ph↗

arXiv1998

Pomeron Non Factorization in Diffractive Scattering at HERA

Pomeron non factorization for the diffractive scattering is considered and an analysis of experimental data is performed with different cuts in the momentum fraction $ξ$. The results of the analysis are compared with the breaking predicted in the Genovese-Nikolaev-Zakharov model.

hep-ph↗

arXiv1997

Quark-antiquark contribution to the BFKL kernel

The quark-antiquark contribution to the BFKL kernel is calculated. Using the effective vertex for the $q\bar q$ pair production in the Reggeon-Reggeon collision we find this contribution by integrating the square of this vertex over relative transverse momenta and fractions of longitudinal momenta of produced particles.

hep-ph↗