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C. Pisano

Publications and source records attributed to C. Pisano.

27 records · Page 2Linked to original sources
arXiv2006

The curvature of $F_2^p(x,Q^2)$ as a probe of the range of validity of perturbative QCD evolutions in the small-$x$ region

Perturbative NLO and NNLO QCD evolutions of parton distributions are studied, in particular in the (very) small-$x$ region, where they are in very good agreement with all recent precision measurements of $F_2^p(x,Q^2)$. These predictions turn out to be also rather insensitive to the specific choice of the factorization scheme ($\bar{\rm MS}$ or DIS). A characteristic feature of perturbative QCD evolutions is a {\em{positive}} curvature of $F_2^p$ which increases as $x$ decreases. This perturbatively stable prediction provides a sensitive test of the range of validity of perturbative QCD.

hep-ph↗
arXiv2005

Probing the Perturbative NLO Parton Evolution in the Small-$x$ Region

A dedicated test of the perturbative QCD NLO parton evolution in the very small-$x$ region is performed. We find a good agreement with recent precision HERA-data for $F_2^p(x,Q^2)$, as well as with the present determination of the curvature of $F_2^p$. Characteristically, perturbative QCD evolutions result in a positive curvature which increases as $x$ decreases. Future precision measurements in the very small $x$-region, $x<10^{-4}$, could provide a sensitive test of the range of validity of perturbative QCD

hep-ph↗
arXiv2004

Accessing the Longitudinally Polarized Photon Content of the Proton

We investigate the QED Compton process (QEDCS) in longitudinally polarized lepton-proton scattering both in the elastic and inelastic channels and show that the cross section can be expressed in terms of the polarized equivalent photon distribution of the proton. We provide the necessary kinematical constraints to extract the polarized photon content of the proton using this process at HERMES, COMPASS and eRHIC. We also discuss the suppression of the major background process coming from virtual Compton scattering. We point out that such an experiment can give valuable information on $g_1(x_B, Q^2)$ in the small $x_B$, broad $Q^2$ region at the future polarized collider eRHIC and especially in the lower $Q^2$, medium $x_B$ region in fixed target experiments.

hep-ph↗
arXiv2004

Delineating the (Un)polarized Photon Content of the Nucleon

We investigate the QED Compton process (both elastic and inelastic) in unpolarized and longitudinally polarized electron-proton scattering. The cross section can be expressed in terms of the equivalent photon distribution of the proton. We provide the necessary kinematical cuts to extract the photon content of the proton at HERMES and eRHIC. We point out that such a process can give valuable information on $g_1(x_B, Q^2)$ in the small $x_B$, broad $Q^2$ region at eRHIC and especially in the lower $Q^2$, medium $x_B$ region in fixed target experiments.

hep-ph↗
arXiv2003

Energy dependence of Cronin momentum in saturation model for $p+A$ and $A+A$ collisions

We calculate $\sqrt{s}$ dependence of Cronin momentum for $p+A$ and $A+A$ collisions in saturation model. We show that this dependence is consistent with expectation from formula which was obtained using simple dimentional consideration. This can be used to test validity of saturation model (and distinguish among its variants) and measure $x$ dependence of saturation momentum from experimental data.

hep-ph↗
arXiv2003

Manifestly Covariant Analysis of the QED Compton Process in $e p\to e γp$ and $e p \to e γX$

We calculate the unpolarized QED Compton scattering cross section in a manifestly covariant way. Our approach allows a direct implementation of the specific kinematical cuts imposed in the experiments, {\it e. g.} HERA-H1. We compare the 'exact' cross section in terms of the structure functions $F_{1,2} (x_B,Q^2)$, assuming the Callan-Gross relation, with the one obtained using the equivalent photon approximation (EPA) as well as with the experimental results. We find that the agreement with the EPA is better in $x_γ$ bins, where $x_γ$ is the fraction of the longitudinal momentum of the proton carried by the virtual photon, compared to the bins in the leptonic variable $x_l$.

hep-ph↗
arXiv2002

Delineating the polarized and unpolarized photon distributions of the nucleon in eN collisions

The production rates of lepton-photon and dimuon pairs at the HERA collider and the HERMES experiment are evaluated in the leading order equivalent photon approximation. It is shown that the production rates are sufficient to facilitate the extraction of the polarized and unpolarized equivalent photon distributions of the proton and neutron in the available kinematical regions. It is pointed out that these results indicate the possibility of additional, independent, tests concerning the unpolarized and polarized structure functions F_{1,2}^N and g_{1,2}^N, respectively, of the nucleon.

hep-ph↗
arXiv2002

The Polarized and Unpolarized Photon Content of the Nucleon

The equivalent photon content of polarized and unpolarized nucleons (protons, neutrons), utilized in Weizsäcker--Williams approximations, are presented. For this purpose a new expression for the elastic photon component of a polarized nucleon is derived. The inelastic photon components are obtained from the corresponding momentum evolution equations subject to the boundary conditions of their vanishing at some low momentum scale. The resulting photon asymmetries, important for estimating cross section asymmetries in photon induced subprocesses are also presented for some typical relevant momentum scales.

hep-ph↗