arXiv subjects

A. Lengyel

Publications and source records attributed to A. Lengyel.

32 records · Page 2Linked to original sources

arXiv2002

The QCD gluon ladders and HERA structure function

We report on the extension of the data fitting considering the QCD inspired model based on the summation of gluon ladders applied to the $ep$ scattering. In lines of a two Pomeron approach, the structure function $F_2$ has a hard piece given by the model and the remaining soft contribution: a soft Pomeron and non-singlet content. In this contribution, we carefully estimate the relative role of the hard and the soft pieces from a global fit in a large span of $x$ and $Q^2$.

hep-ph↗

arXiv2002

Describing F_2 through a finite sum of gluon ladders

Electroproduction in deep inelastic scattering at HERA is studied in a model considering a finite sum of gluon ladders, associated with a truncation of the BFKL series. The approach contains the bare two gluon exchange and both one and two rungs contributions. The model is fitted to the data on the inclusive structure function F_2(x,Q^2) in the region x<0.025 and 0.045<Q^2<1500 GeV^2, with a good agreement. Such a description for a large span in Q^2 is obtained through a suitable modeling of the remaining non-perturbative background.

hep-ph↗

arXiv2002

From Regge Behavior to DGLAP Evolution

We study the interface between Regge behavior and DGLAP evolution in a non-perturbative model for the nucleon structure function based on a multipole pomeron exchange. This model provides the input for a subsequent DGLAP evolution that we calculate numerically. The soft input and its evolution give a good fit to the experimental data in the whole available range of x and Q^2.

hep-ph↗

arXiv2001

Pomeron effective intercept, logarithmic derivatives of $F_{2}(x,Q^{2})$ in DIS and Regge models

The drastic rise of the proton structure function $F_2(x,Q^2)$ when the Björken variable $x$ decreases, seen at HERA for a large span of $Q^2$, may be damped when $x\to 0$ and $Q^2$ increases beyond $\sim$ several hundreds \g2. This phenomenon observed in the Regge type models is discussed in terms of the effective Pomeron intercept and of the derivative $B_x=\partial{\ell n F_2(x,Q^2)}/\partial{\ell n(1/x)}$. The method of the overlapping bins is used to extract the derivatives $B_x$ and $B_Q=\partial{\ell n F_2(x,Q^2)}/\partial{Q^2}$ from the data on $F_2$ for $6.0\cdot 10^{-5}\le x\le 0.61$ and $1.2 \le Q^2$ (\g2) $\le 5000$. It is shown that the extracted derivatives are well described by recent Regge models with the Pomeron intercept equal one.

hep-ph↗

arXiv2001

Models of realistic Reggeons for t=0 high energy scattering

Several Regge-phenomenological models of forward scattering at high energies are considered. It was found that one of them corresponds to the form of finite series in log s with additional terms that represent the exchanges of non-degenerate Regge-trajectories. These trajectories are unique for both the scattering and resonance regions and satisfy the most realistic ideas on them.

hep-ph↗

arXiv2001

pbarp and pp Elastic Scattering in a Multipole-Pomeron Model

We assume that the Pomeron is a sum of Regge multipoles, each corresponding to a finite gluon ladder. From a fit to the diffraction cone data of pp- and pbarp- scattering we found that the triple pole is significant for the rise of the ratio sigma_el/sigma_tot at high energies.

hep-ph↗

arXiv2000

Damping of the HERA effect in DIS?

The drastic rise of the proton structure function F_2(x,Q^2) when the Björken variable x decreases, seen at HERA for a large span of Q^2, negative values for the 4-momentum transfer, may be damped when Q^2 increases beyond several hundreds GeV^2. A new data analysis and a comparison with recent models for the proton structure function is proposed to discuss this phenomenon in terms of the derivative \partial ln F_2(x,Q^2)/\partial ln(1/x).

hep-ph↗

arXiv2000

Maximum entropy method and oscillations in the diffraction cone

The maximum entropy method has been applied to investigate the oscillating structure in the pbarp- and pp-elastic scattering differential cross-section at high energy and small momentum transfer. Oscillations satisfying quite realistic reliability criteria have been found.

hep-ph↗

arXiv2000

Pomeron models and exchange degeneracy of the Regge trajectories

Two models for the Pomeron, supplemented by exchange degenerate sub-leading Regge trajectories, are fitted to the forward scattering data for a number of reactions. By considering new Pomeron models, we extend the recent results of the COMPAS group, being consistent with our predecessors.

hep-ph↗

arXiv2000

The Pomeron as a Finite Sum of Gluon Ladder

A model for the Pomeron at t=0 is suggested. It is based on the idea of a finite sum of ladder diagrams in QCD. Accordingly, the number of s-channel gluon rungs and correspondingly the powers of logarithms in the forward scattering amplitude depends on the phase space (energy) available, i.e. as energy increases, progressively new prongs with additional gluon rungs in the s-channel open. Explicit expressions for the total cross section involving two and three rungs or, alternatively, three and four prongs (with $\ln^2(s)$ and $\ln^3(s)$ as highest terms) is fitted to the proton-proton and proton-antiproton total cross section data in the accelerator region.

hep-ph↗

arXiv1999

How fast do small x structure function rise ? A comparative analysis

We parametrize the small x, singlet component of the proton structure function F_2 by powers and logarithms of 1/x for discrete values of Q^2 between 0.2 and 2000 GeV^2, and compare these parametrizations by applying the criterion of minimal $χ^2$. The obtained values of the fitted parameters may be used to study the evolution of F_2 in Q^2 and/or in discriminating between dynamical models. A slowing-down in the increase of F_2 towards highest available values of Q^2 is revealed. The effect is quantified in terms of the derivative ${\frac{d\ell n F_2(x,Q^2)}{d\ell n (1/x)}}$.

hep-ph↗

arXiv1998

The proton structure function and a soft Regge Dipole Pomeron: a test with recent data

A recently published soft Regge Dipole Pomeron model intended for all $x$ and $Q^2$ is proved to give a good agreement with (non fitted) recent HERA data from ZEUS (SVX95) on the protonstructure function $F_2^p(x,Q^2)$ at low $Q^2$ and low $x$. The model also reproduces (without fit) the recently estimated experimental derivatives ${\partial F_2^p\over\partial\ell n Q^2}$ and ${\partial \ell n F_2^p\over\partial\ell n (1/x)}$ in a wide $x$ and $Q^2$-region.

hep-ph↗

arXiv1998

New possibilities of old soft pomeron in DIS

A traditional Regge model with a $Q^2$-independent Pomeron intercept closed (or equal) to one is constructed in order to describe the available data on the proton structure function. A Dipole Pomeron model which does not explicitly violate unitarity is developed and investigated. An excellent agreement with the 1209 data is found ($χ^2/{dof}=1.11$) in the whole kinematical domain investigated by experiments. A comparison of the model with already existing ones is made. The $x-$, $Q^2-$slopes and the effective intercept are discussed as $Q^2$ and $x$ functions.

hep-ph↗

arXiv1998

Parametrising the proton structure function

We show that simple parametrisations at small x of the proton structure function work so well in limited regions of the $(x,Q^2)$ plane because they are approximately "self-consistent" solutions of the QCD evolution equation. For a class of them, we predict their $Q^2$ dependence and compare the result with experimental data.

hep-ph↗