arXiv subjects

D. A. Fagundes

Publications and source records attributed to D. A. Fagundes.

31 records · Page 2Linked to original sources

arXiv2014

An empirical model for $pp$ scattering and geometrical scaling

We present the result of an empirical model for elastic $pp$ scattering at LHC which indicates that the asymptotic black disk limit ${\cal R}=\sigel/\sigtot\rightarrow1/2$ is not yet reached and discuss the implications on classical geometrical scaling behavior. We propose a geometrical scaling law for the position of the dip in elastic $pp$ scattering which allows to make predictions valid both for intermediate and asymptotic energies.

hep-ph↗

arXiv2013

Modeling the elastic differential cross-section at LHC

An empirical model for the $pp$ elastic differential cross section is proposed. Inspired by early work by Barger and Phillips, we parametrize the scattering amplitude in building blocks, comprising of two exponentials with a relative phase, supplementing the dominant term at small $-t$ with the proton form factor. This model suitably applies to LHC7 and ISR data, enabling to make simple predictions for higher LHC energies and to check whether asymptotia might be achieved.

hep-ph↗

arXiv2013

On the rise of proton-proton cross-sections at high energies

The rise of the total, elastic and inelastic hadronic cross sections at high energies is investigated by means of an analytical parametrization, with the exponent of the leading logarithm contribution as a free fit parameter. Using derivative dispersion relations with one subtraction, two different fits to proton-proton and antiproton-proton total cross section and rho parameter data are developed, reproducing well the experimental information in the energy region 5 GeV - 7 TeV. The parametrization for the total cross sections is then extended to fit the elastic (integrated) cross section data in the same energy region, with satisfactory results. From these empirical results we extract the energy dependence of several physical quantities: inelastic cross section, ratios elastic/total, inelastic/total cross sections, ratio total-cross-section/elastic-slope, elastic slope and optical point. All data, fitted and predicted, are quite well described. We find a statistically consistent solution indicating: (1) an increase of the hadronic cross sections with the energy faster than the log-squared bound by Froissart and Martin; (2) asymptotic limits 1/3 and 2/3 for the ratios elastic/total and inelastic/total cross sections, respectively, a result in agreement with unitarity. These indications corroborate recent theoretical arguments by Ya. I. Azimov on the rise of the total cross section.

hep-ph↗

arXiv2013

Hunting for asymptotia at LHC

We discuss whether the behaviour of some hadronic quantities, such as the total cross-section, the ratio of the elastic to the total cross-section, are presently exhibiting the asymptotic behaviour expected at very large energies. We find phenomenological evidence that at LHC7 there is still space for further evolution.

hep-ph↗

arXiv2012

Reply to "Commentary on "Total Hadronic Cross Section Data and the Froissart-Martin Bound", by Fagundes, Menon and Silva"

A reply to the above mentioned commentary by M.M. Block and F. Halzen on our quoted work is presented. We answer to each point raised by these authors and argument that our data reductions, strategies and methodology are adequate to the nonlinear-fit-problem in focus. In order to exemplify some arguments, additional information from our subsequent analysis is referred to. A brief commentary on the recent results by Block and Halzen is also presented. We understand that this reply gives support to the results and conclusions presented in our quoted work.

hep-ph↗

arXiv2012

Preliminary Results on the Empirical Applicability of the Tsallis Distribution in Elastic Hadron Scattering

We show that the proton-proton elastic differential cross section data at dip position and beyond can be quite well described by a parametrization based on the Tsallis distribution, with only five free fit parameters. Extrapolation of the results obtained at 7 TeV to large momentum transfer, suggests that hadrons may not behave as a black-disk at the asymptotic energy region.

hep-ph↗

arXiv2012

Total Hadronic Cross Section Data and the Froissart-Martin Bound

The energy dependence of the total hadronic cross section at high energies is investigated with focus on the recent experimental result by the TOTEM Collaboration at 7 TeV and the Froissart-Martin bound. On the basis of a class of analytical parametrization with the exponent $γ$ in the leading logarithm contribution as a free parameter, different variants of fits to $pp$ and $\bar{p}p$ total cross section data above 5 GeV are developed. Two ensembles are considered, the first comprising data up to 1.8 TeV, the second also including the data collected at 7 TeV. We shown that in all fit variants applied to the first ensemble the exponent is statistically consistent with $γ$ = 2. Applied to the second ensemble, however, the same variants yield $γ$'s above 2, a result already obtained in two other analysis, by U. Amaldi \textit{et al}. and by the UA4/2 Collaboration. As recently discussed by Ya. I. Azimov, this faster-than-squared-logarithm rise does not necessarily violate unitarity. Our results suggest that the energy dependence of the hadronic total cross section at high energies still constitute an open problem.

hep-ph↗

arXiv2012

Hadronic Cross Sections, Elastic Slope and Physical Bounds

An almost model-independent parametrization for the ratio of the total hadronic cross section to elastic slope is discussed. Its applicability in studies of asymptotia and analyses of extensive air shower in cosmic-ray physics is also outlined.

hep-ph↗

arXiv2012

Aspects of a dynamical gluon mass approach to elastic hadron scattering at LHC

We discuss how the main features of the recent LHC data on elastic scattering can be described by a QCD-inspired formalism with a dynamical infrared mass scale. For this purpose new developments on a dynamical gluon mass approach are reported, with emphasis on a method to estimate uncertainty bounds in the predictions for the high-energy scattering observables. We investigate the effects due to the correlations among the fixed and free parameters involved and show that the band of predictions are consistent with the recent data from the TOTEM experiment, including the forward quantities and the differential cross section up to the dip position.

hep-ph↗

arXiv2012

Total Hadronic Cross Section and the Elastic Slope: An Almost Model-Independent Connection

An almost model-independent parametrization for the ratio of the total cross section to the elastic slope, as function of the center of mass energy, is introduced. The analytical result is based on the approximate relation of this quantity with the ratio $R$ of the elastic to total cross section and empirical fits to the $R$ data from proton-proton scattering above 10 GeV, under the conditions of asymptotic unitarity and the black-disk limit. This parametrization may be useful in studies of extensive air showers and the determination of the proton-proton total cross section from proton-air production cross section in cosmic-ray experiments.

hep-ph↗

arXiv2012

Testing parameters in an eikonalized dynamical gluon mass model

In the framework of a dynamical gluon mass model recently developed, we investigate the effects of two essential parameters in the description of elastic $pp$ and $\bar{p}p$ data at high energies: the soft Pomeron intercept and the dynamical gluon mass. By considering relevant numerical intervals for both parameters and fits to the experimental data up to 1.8 TeV, with good statistical results, we discuss the predictions of the physical quantities at the LHC energies (7 and 14 TeV). We conclude that these quantities are sensitive to those variations and the predictions are correlated with the intervals considered for both parameters. This conclusion puts limits on the reliability of QCD inspired models predictions at the LHC energies, mainly those models with ad hoc fixed values for the mass scale and the Pomeron intercept.

hep-ph↗

arXiv2011

Applicability of a Representation for the Martin's Real-Part Formula in Model-Independent Analyses

Using a novel representation for the Martin's real-part formula without the full scaling property, an almost model-independent description of the proton-proton differential cross section data at high energies (19.4 GeV - 62.5 GeV) is obtained. In the impact parameter and eikonal frameworks, the extracted inelastic overlap function presents a peripheral effect (tail) above 2 fm and the extracted opacity function is characterized by a zero (change of sign) in the momentum transfer space, confirming results from previous model-independent analyses. Analytical parametrization for these empirical results are introduced and discussed. The importance of investigations on the inverse problems in high-energy elastic hadron scattering is stressed and the relevance of the proposed representation is commented. A short critical review on the use of Martin's formula is also presented.

hep-ph↗

arXiv2011

Model-independent data reductions of elastic proton-proton scattering

New developments in empirical analyses of the proton-proton differential cross section data at high energies are reported. Making use of an unconstrained model-independent parametrization for the scattering amplitude and two different fit procedures, all the experimental data in the center-of-mass energy interval 19.4 - 62.5 GeV are quite well described (optical point and data above the region of Coulomb-nuclear interference). The contributions from the real and imaginary parts of the amplitude beyond the forward direction are discussed and compared with the results from previous analyses and phenomenological models. Extracted overlap functions (impact parameter space) are outlined and a critical discussion on model-independent analyses and results are also presented.

hep-ph↗