arXiv subjects
Publications and source records attributed to G. Parente.
We investigate the Q^2 evolution of parton distributions at small x values, obtained in the case of flat initial conditions. The results are in excellent agreement with deep inelastic scattering experimental data from HERA.
We investigate the Q^2 evolution of parton distributions at small x values, recently obtained in the case of soft initial conditions. The results are in excellent agreement with deep inelastic scattering experimental data from HERA.
We study prospects for the observations of high-energy cosmic tau neutrinos (E \geq 10^6 GeV) originating from proton acceleration in the cores of active galactic nuclei. We consider the possibility that vacuum flavor neutrino oscillations induce a tau to muon neutrino flux ratio greatly exceeding the rather small value expected from intrinsic production. The criterias and event rates for under water/ice light Cerenkov neutrino telescopes are given by considering the possible detection of downgoing high-energy cosmic tau neutrinos through characteristic double shower events.
The summary of the results of our next-to-next-to-leading fits of Tevatron experimental data for $xF_3$ structure function of the $νN$ deep-inelastic scattering is given. The special attention is paid to the extraction of twist-4 contributions and demonstration of the interplay between these effects and higher-order perturbative QCD corrections. The factorization and renormalization scale uncertainties of the results obtained are analysed
A detailed next-to-next-to-leading order (NNLO) QCD analysis is performed for the experimental data of the CCFR collaboration for the $xF_3$ structure function. Theoretical ambiguities of the results of our NNLO fits are estimated by application of the Padé resummation technique and variation of the factorization and renormalization scales. The NNLO and N$^3$LO $α_s(Q^2)$ $\bar{MS}$-matching conditions are used. In the process of the fits we are taking into account of twist-4 $1/Q^2$-terms. We found that the amplitude of the $x$-shape of the twist-4 factor is decreasing in NLO and NNLO, though some remaining twist-4 structure seems to retain in NNLO in the case when statistical uncertainties are taken into account. The question of the stability of these results to the application of the [0/2] Padé resummation technique is considered. Our NNLO results for $α_s(M_Z)$ values, extracted from the CCFR $xF_3$ data, are $α_s(M_Z)=0.118 \pm 0.002 (stat) \pm 0.005 (syst)\pm 0.003 (theory)$ provided the twist-4 contributions are fixed through the infrared renormalon model and $α_s(M_Z)=0.121^{+0.007}_{0.010}(stat)\pm 0.005 (syst) \pm 0.003 (theory)$ provided the twist-4 terms are considered as free parameters.
The next-to-next-to-leading order (NNLO) QCD analysis of the experimental $xF_3$ structure function from CCFR data is performed. The theoretical uncertainties of the analysis are discussed.
We continue the systematic next-to-next-to-leading order (NNLO) QCD analysis of the CCFR data for $xF_3$ SF. The NNLO results forthe $Q^2$-dependence of the parameters, which describe the $x$-dependence of this SF, are presented.
The results of the more detailed NNLO QCD analysis of the CCFR data for $xF_3$ SF are presented. The factorization scale uncertainties are analysed. The NNLO results for $alpha_s(M_Z)$ and twist-4 contributions are obtained. Despite the fact that the amplitude of the $x$-shape of the twist-4 factor is consequently decreasing at the NLO and NNLO, our new QCD analysis seems to reveal the remaining twist-4 structure at the NNLO level. The definite N$^3$LO uncertainties are fixed using the [0/2] Padé resummation technique.
We investigate the Q2 evolution of parton distributions at small x values, recently obtained in the case of soft initial conditions. The results are in excellent agreement with deep inelastic scattering experimental data from HERA.
The improved next-to-next-to-leading order (NNLO) QCD analysis of the experimental data of the CCFR collaboration for the $xF_3$ structure function is made. Theoretical ambiguities of the NNLO fits are estimated by means of the Padé resummation technique, which was applied both in the expanded and non-expanded forms. The NNLO and the new N$^3$LO $α_s(Q^2)$ $\bar{MS}$-matching conditions are used. In the process of the fits we are taking into account the target mas corrections and the twist-4 $1/Q^2$-terms. Our NNLO results for $α_s(M_Z)$ values, extracted from the CCFR $xF_3$ data, are $α_s(M_Z)=0.118 \pm 0.002 (stat)\pm 0.005 (syst) \pm 0.003(theory)$ provided the twist-4 contributions are fixed through the infrared renormalon model and $α_s(M_Z)=0.116^{+ 0.006}_{-0.007}(stat)\pm 0.005 (syst) \pm 0.004(theory)$ provided the twist-4 terms are considered as the free parameters. It is shown that the extracted at the NNLO order $x$-shape of the twist-4 correction is almost unchanged after application of the Padé resummation approximant.
We present an analytical parametrization of the QCD description of the small x behaviour of parton distribution functions in the leading twist approximation of the Wilson operator product expansion, in the case of soft initial conditions. The results are in very good agreement with deep inelastic scattering experimental data from HERA.
We show that the Auger Air Shower Array has the potential to detect neutrinos of energies in the $10^{19}~$eV range through horizontal air showers. Assuming some simple conservative trigger requirements we obtain the acceptance for horizontal air showers as induced by high energy neutrinos by two alternative methods and we then give the expected event rates for a variety of neutrino fluxes as predicted in different models which are used for reference.
We present very simple non-integral relations between deep inelastic structure functions $F_L$, $F_2$ and the gluon distribution at small $x$ based on perturbative QCD which are useful for the phenomenological analysis of data at low $x$. As an application we extract the deep inelastic scattering cross-sections ratio $R= σ_L/σ_T$ in the range $10^{-4} \leq x \leq 10^{-2}$ from $F_2$ HERA data.
The next-to-next-to-leading order (NNLO) QCD analysis of the revised experimental data of the CCFR collaboration for the $xF_3$ structure function of the deep-inelastic scattering of neutrinos and antinuetrinos on the nucleons is made by means of the Jacobi polynomial expansion technique. The NNLO values of the QCD coupling constant are determined both without and with twist--4 contributions taken into account. Theoretical ambiguities of $α_s$ are fixed using the methods of the Padé approximants. We observe that the [0/2] Padé approximant is more appropriate for this purpose than the [1/1] one.
We present the results of the next-to-next-to-leading order QCD analysis of the recently revised experimental data of the CCFR collaboration for the $xF_3$ structure function using the Jacobi polynomial expansion method. The effects of the higher twist contributions are included into the fits following the infrared renormalon motivated model. The special attention is paid to the checks of the predictive abilities of the infrared renormalon model and to the independent extraction of the $x$-shape of the twist-4 contributions to the $xF_3$ structure function in the process of the leading order, next-to-leading order and next-to-next-to-leading order fits of the revised CCFR data. We stress that at the next-to-next-to-leading order the results for $α_s(M_Z)$ turn out to be almost nonsensitive to the higher-twist terms. We obtain the following result $α_s(M_Z)^{NNLO}=0.117 \pm 0.002(stat) \pm 0.005 (syst)\pm 0.003 (theory)$. The comparison of the outcomes of our next-to-leading order and next-to-next-to-leading order analysis indicate that the theoretical QCD uncertainties were underestimated in the process of the next-to-leading order determination of $α_s(M_Z)$, made recently by the CCFR collaboration itself.
We extract the deep inelastic scattering cross-sections ratio $R= σ_L/σ_T$ in the range $10^{-4} \leq x \leq 10^{-1}$ from $F_2$ HERA data using very simple relations based on perturbative QCD. The result depends on only one parameter $δ$, being $x^{-δ}$ the behavior of the parton densities at low $x$, which has been determined recently with a good accuracy by the H1 group.
We present a set of formulae to extract the longitudinal deep inelastic structure function $F_L$ from the transverse structure function $F_2$ and its derivative $dF_2/dlnQ^2$ at small $x$. Using $F_2$ HERA data we obtain $F_L$ in the range $10^{-4} \leq x \leq 10^{-2}$ at $Q^2=20$ GeV$^2$