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A. Lengyel

Publications and source records attributed to A. Lengyel.

At least 19 recordsLinked to original sources

Froissaron and Maximal Odderon with spin-flip in $pp$ and $\bar pp$ high energy elastic scattering

We assume that the scattering amplitude is represented by Froissaron, Maximal Odderon as well as by standard Regge poles. From the fit to the data of $pp$ and $\bar pp$ scattering at high energy and not too large momentum transfers we found that this model taking into account the spin is available to describe not only the differential, total cross section and $ρ$, but also the existing experimental data on polarization.

hep-ph

Which Pomeron survives at LHC energies?

An eikonalized elastic proton-proton and proton-antiproton scattering amplitude, based on the suggestion of a finite sum of ladder diagrams, calculated from QCD and the number of $s-$channel gluon rungs and correspondingly the powers of logarithms in total cross section depends on available increasing energy. Explicit expressions for total cross section involving three and four rungs (four and five prongs), as highest terms, respectively) are fitted to the all available proton-proton and proton-antiproton total cross section data. Predictions for pp total cross section at LHC energy are given and compared with prediction of several Regge-models including possible hard Pomeron contribution.

hep-ph

The Pomeron and Odderon in elastic, inelastic and total cross sections at the LHC

A simple model for elastic diffractive hadron scattering, reproducing the dip-bump structure is used to analyze PP and $\bar PP$ scattering. The main emphasis is on the delicate and non-trivial dynamics in the dip-bump region, near t=-1 GeV$^2$. The simplicity of the model and the expected smallness of the absorption corrections enables one the control of various contributions to the scattering amplitude, in particular the interplay between the C-even and C-odd components of the amplitude, as well as their relative contribution, changing with s and t. The role of the non-linearity of the Regge trajectories is scrutinized. The ratio of the real to imaginary parts of the forward amplitude, the ratio of elastic to total cross sections and the inelastic cross section are calculated. Predictions for the LHC energy region, where most of the exiting models will be either confirmed or ruled out, are presented.

hep-ph

Predictions for high-energy pp and \bar pp scattering from a finite sum of gluon ladders

An eikonalized elastic proton-proton and proton-antiproton scattering amplitude F(s,t), calculated from QCD as a finite sum of gluon ladders, is compared with the existing experimental data on the total cross section and the ratio ρ(s,0)=Re F(s,0)/Im F(s,0) of the real part to the imaginary part of the forward amplitude. Predictions for the expected LHC energies are given.

hep-ph

The soft and the hard pomerons in hadron elastic scattering at small t

We consider simple-pole descriptions of soft elastic scattering for pp, pbar p, pi+ p, pi- p, K+ p and K- p. We work at t and s small enough for rescatterings to be neglected, and allow for the presence of a hard pomeron. After building and discussing an exhaustive dataset, we show that simple poles provide an excellent description of the data in the region - 0.5 GeV^2 < t < -0.1 GeV^2, 6 GeV<sqrt(s)< 63 GeV. We show that new form factors have to be used, and get information on the trajectories of the soft and hard pomerons.

hep-ph

Elastic Meson-Nucleon and Nucleon-Nucleon Scattering: Models vs. All Available Data

We consider simple-pole descriptions of soft elastic scattering at small $t$ and $s$, and allow for the presence of a hard pomeron. We have built and analyzed an exhaustive dataset and we show that simple poles provide an excellent description of the data in the region $- 0.5$ GeV$^2 < t <$ $- 0.1$ GeV$^2$, 6 GeV$<\sqrt{s}<$63 GeV. We show that new form factors have to be used, and get information on the trajectories of the soft and hard pomerons.

hep-ph

Hard pomeron contribution to forward elastic scattering

The introduction of a hard singularity in fits to total cross sections and to the ratio of real to imaginary parts enables to reproduce perfectly the data for sqrt(s)< 100 GeV using only simple-pole parametrisations, both for the soft and for the hard pomerons.

hep-ph

Direct extraction of hadronic form factors from elastic-scattering data

Non-forward elastic hadron-scattering data are collected and analysed within the Regge approach. Through an analysis of the data in small bins in $t$, we have directly extracted the pomeron trajectory and the hadronic form factors (or reggeon couplings). We found higher values than usually used for the intercept and for the slope of the soft pomeron trajectory. The presence of zeros in $t$ for the effective hadronic form factors is emphasised.

hep-ph

Revisiting the phenomenology on the QCD color dipole picture

Using the QCD dipole picture of the hard BFKL Pomeron, we perform a 3 parameter fit analysis of the recent inclusive structure function experimental measurements at small-$x$ and intermediate $Q^2$. As a byproduct, the longitudinal structure function and the gluon distribution are predicted without further adjustments. The data description is quite reasonable, being timely a further study using resummed NLO BFKL kernels along the lines of recent theoretical developments.

hep-ph

Soft data and the hard pomeron

We show that the introduction of an additional, hard, singularity in soft forward amplitudes enables one to improve considerably the fits using a simple-pole structure for the soft pomeron.

hep-ph

The hard pomeron in soft data

We show that the data for the total cross section and for the real part of the elastic amplitude indicate the presence of a hard pomeron in pi p and Kp elastic scattering at t=0, compatible with that observed in deep inelastic scattering. We show that such a hard pomeron is also compatible with pp and pbar p data, provided one unitarises it at high energy.

hep-ph

Phenomenology on the QCD dipole picture revisited

We perform an adjust to the most recent structure function data, considering the QCD dipole picture applied to ep scattering. The structure function F2 at small x and intermediate Q2 can be described by the model containing an economical number of free-parameters, which encodes the hard Pomeron physics. The longitudinal structure function and the gluon distribution are predicted without further adjustments. The data description is effective, whereas a resummed next-to-leading level analysis is deserved.

hep-ph

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

On a two Pomeron description of the F_2 structure function

We perform a global fit to the inclusive structure function considering a QCD inspired model describing 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 contributions: the soft Pomeron and non-singlet content. We have investigated several choices for the soft Pomeron and its implication in the data description. In particular, we carefully estimated the relative role of the hard and the soft contributions in a large span of x and Q^2.

hep-ph

Overview of the COMPETE Program

Nowadays, scientific databases have become the bread-and-butter of particle physicists. These databases must be maintained and checked repeatedly to insure the accuracy of their content. The COMPETE collaboration aims at motivating data maintenance via the interfacing of theory and experiment at the database level. The database concept then needs to be supplemented by a "model-base". Such an object enables one not only to decide what the best description may be, but also to discern what potential problems exist in the data. The systematization of such a cross-fertilization between models and data results in the "object of knowledge" that is the point at which all existing information resources on a given problem could converge. There are many advantages to such a global approach. First of all, the maintenance of a data set is not a static task: it needs to be motivated by physics. The second advantage is that one can have a common testing ground for theories and models. Thirdly, an extensive theoretical database can be used to plan new experiments and to predict various quantities. Finally, as new data come in, one can very quickly decide on their theoretical impact, and hence immediately evaluate the need for new physics ideas. As we want to treat a large amount of data and many models, computer technology constitutes an important part of our activity. We have concentrated on the elaboration of artificial intelligence decision-making algorithms, as well as on the delivery of computer tools for the end-user. Further linkage with existing databases, such as PDG, COMPAS, and HEPDATA is being developed or planned.

hep-ph