arXiv subjects

R. Fiore

Publications and source records attributed to R. Fiore.

At least 55 records · Page 3Linked to original sources

arXiv2007

Universality and massive excitations in 3d 3-state Potts model

The mass spectrum of the 3d 3-state Potts model is considered in the broken phase (a) near the second order Ising critical point in the temperature-magnetic field plane and (b) near the weakly first order transition point at zero magnetic field. In the case (a), the mass spectrum is compared with the prediction from universality of mass ratios in the 3d Ising class; in the case (b) a mass ratio is determined to be compared with the corresponding one in the spectrum of screening masses of the (3+1)d SU(3) pure gauge theory at finite temperature in the deconfined phase near the transition.

hep-lat↗

arXiv2007

The dipole form of the gluon part of the BFKL kernel

The dipole form of the gluon part of the colour singlet BFKL kernel in the next-to-leading order (NLO) is obtained in the coordinate representation by direct transfer from the momentum representation, where the kernel was calculated before. With this paper the transformation of the NLO BFKL kernel to the dipole form, started a few months ago with the quark part of the kernel, is completed.

hep-ph↗

arXiv2007

Color dipoles, PCAC and Adler's theorem

Being reformulated in the color dipole basis of small-x QCD Adler's theorem establishes a connection between perturbative and non-perturbative descriptions of DIS and quantifies the effect of non-perturbative dynamics on would-be-perturbative observables. In particular, it provides a quantitative measure of the non-perturbative influence on the longitudinal structure function in charged current DIS and imposes stringent constraints on non-perturbative parameters of color dipole models. Our analysis calls for new experimental tests of Adler's theorem in diffractive neutrino scattering.

hep-ph↗

arXiv2007

J/Psi Photoproduction in a Dual Model

J/Psi photoproduction is studied in the framework of the analytic S-matrix theory. The differential and integrated elastic cross sections for J/Psi photoproduction are calculated from a Dual Amplitude with Mandelstam Analyticity. It is argued that at low energies, the background, which is the low-energy equivalent of the high-energy diffraction replaces the Pomeron exchange. The onset of the high energy Pomeron dominance is estimated from the fits to the data.

hep-ph↗

arXiv2006

A Deeply Virtual Compton Scattering Amplitude

A factorized Regge-pole model for deeply virtual Compton scattering is suggested. The use of an effective logarithmic Regge-Pomeron trajectory provides for the description of both ``soft'' (small $|t|$) and ``hard'' (large $|t|$) dynamics. The model contains explicitly the photoproduction and the DIS limits and fits the existing HERA data on deeply virtual Compton scattering.

hep-ph↗

arXiv2006

Proof of the multi-Regge form of QCD amplitudes with gluon exchanges in the NLA

The multi--Regge form of QCD amplitudes with gluon exchanges is proved in the next-to-leading approximation. The proof is based on the bootstrap relations, which are required for the compatibility of this form with the s-channel unitarity. We show that the fulfillment of all these relations ensures the Reggeized form of energy dependent radiative corrections order by order in perturbation theory. Then we prove that all these relations are fulfilled if several bootstrap conditions on the Reggeon vertices and trajectory hold true. Now all these conditions are checked and proved to be satisfied.

hep-ph↗

arXiv2005

Asymptotic neutrino-nucleon cross section and saturation effects

In this paper we present a simple analytic expression for the (spin-averaged) neutrino-nucleon cross section for ultra-high energies at twist-2, obtained as the asymptotic limit of our previous findings. This expression gives values for the cross section in remarkable numerical agreement with the previous numerical evaluation in the energy region relevant for forthcoming neutrino experiments. Moreover, we discuss the role and the relevance of saturation and recombination effects in our approach, in comparison with other recent suggestions.

hep-ph↗

arXiv2005

QED$_3$ on a space-time lattice: compact versus noncompact formulation

We study quantum electrodynamics in a (2+1)-dimensional space-time with two flavors of dynamical fermions by numerical simulations on the lattice. We discretize the theory using both the compact and the noncompact formulations and analyze the behavior of the chiral condensate and of the monopole density in the finite lattice regime as well as in the continuum limit. By comparing the results obtained with the two approaches, we draw some conclusions about the possible equivalence of the two lattice formulations in the continuum limit.

hep-lat↗

arXiv2005

Left-right asymmetry of nuclear shadowing in charged current DIS

We study the shadowing effect in highly asymmetric diffractive interactions of left-handed and right-handed W-bosons with atomic nuclei. The target nucleus is found to be quite transparent for the charmed-strange Fock component of the light-cone W^+ in the helicity state λ=+1 and rather opaque for the c\bar s dipole with λ=-1. The shadowing correction to the structure function ΔxF_3 = xF_3^{νN}-xF_3^{\barνN} extracted from νFe and \barνFe data is shown to make up about 20% in the kinematical range of CCFR/NuTeV.

hep-ph↗

arXiv2005

Charged currents, color dipoles and xF_3 at small x

We develop the light-cone color dipole description of highly asymmetric diffractive interactions of left-handed and right-handed electroweak bosons. We identify the origin and estimate the strength of the left-right asymmetry effect in terms of the light-cone wave functions. We report an evaluation of the small-x neutrino-nucleon DIS structure functions xF_3 and 2xF_1 and present comparison with experimental data.

hep-ph↗

arXiv2005

Non-forward NLO BFKL Kernel

Details of the calculation of the non-forward BFKL kernel at next-to-leading order (NLO) are offered. Specifically we show the calculation of the two-gluon production contribution. This contribution was the last missing part of the kernel. Together with the NLO gluon Regge trajectory, the NLO contribution of one-gluon production and the contribution of quark-antiquark production which were found before it defines the kernel completely for any colour state in the $t$-channel, in particular the Pomeron kernel presented recently.

hep-ph↗

arXiv2004

Non-forward BFKL Pomeron at next-to-leading order

The kernel of the BFKL equation for non-zero momentum transfer is found at next-to-leading order. It is presented in various forms depending on the regularization of the infrared singularities in "virtual" and "real" parts of the kernel. The infrared safety of the total kernel is demonstrated and a form free from the singularities is suggested.

hep-ph↗

arXiv2004

Analytical evolution of nucleon structure functions with power corrections at twist-4 and predictions for ultra-high energy neutrino-nucleon cross section

In this paper we present an analytic result for the evolution in $Q^2$ of the structure functions for the neutrino-nucleon interaction, valid at twist-2 in the region of small values of the Bjorken $x$ variable and for soft non-perturbative input. In the special case of flat initial conditions, we include in the calculation also the contribution of the twist-4 gluon recombination corrections, whose effect in the evolution is explicitly determined. Finally, we estimate the resulting charged-current neutrino-nucleon total cross section and discuss its behavior at ultra-high energies.

hep-ph↗

arXiv2004

Baryonic Regge trajectories with analyticity constraints

A model for baryonic Regge trajectories compatible with the threshold behavior required by unitarity and asymptotic behavior in agreement with analyticity constraints is given in explicit form. Widths and masses of the baryonic resonances on the N and $Δ$ trajectories are reproduced. The MacDowell symmetry is exploited and an application is given.

hep-ph↗

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

Ultra-high energy neutrino-nucleon interactions

Ultra-high energy ($E_ν>10^8 $ GeV) neutrino-nucleon total cross sections $σ^{νN}$ are estimated from a soft non-perturbative model complemented by an approximate QCD evolution, explicitly calculated. The resulting asymptotic energy behavior of the neutrino-nucleon charged-current total cross section is derived analytically and predictions concerning the observation of ultra-high energy neutrinos in future experiments are presented.

hep-ph↗

arXiv2003

The Bootstrap Conditions for the Gluon Reggeization

Compatibility of gluon Reggeization with s-channel unitarity requires the vertices of the Reggeon interactions to satisfy a series of bootstrap conditions. In order to derive, in the next-to-leading order (NLO), conditions related to the gluon production amplitudes, we calculate the s-channel discontinuities of these amplitudes and compare them with those required by the Reggeization. It turns out that these conditions include the so called strong bootstrap conditions for the kernel and for the impact factors of scattering particles, which were proposed earlier without derivation, and recently were proved to be satisfied. Besides this, there is a new bootstrap condition, which relates a number of Reggeon vertices and the gluon trajectory.

hep-ph↗