The QCD Pomeron in ultraperipheral heavy ion collisions: III. Photonuclear production of heavy quarks

We calculate the photonuclear production of heavy quarks in ultraperipheral heavy ion collisions. The integrated cross section and the rapidity distribution are computed employing sound high energy QCD formalisms as the collinear and semihard approaches as well as the saturation model. In particular, the color glass condensate (CGC) formalism is also considered using a simple phenomenological parameterization for the color field correlator in the medium, which allow us to obtain more reliable estimates for charm and bottom production at LHC energies.Comment: 15 pages, 2 figures. Extended version to be published in Eur. Phys. J.

Geometric Scaling in Inclusive Charm Production

We show that the cross section for inclusive charm production exhibits geometric scaling in a large range of photon virtualities. In the HERA kinematic domain the saturation momentum $Q_{sat}^2(x)$ stays below the hard scale $\mu_c^2=4m_c^2$, implying charm production probing mostly the color transparency regime and unitarization effects being almost negligible. We derive our results considering two saturation models which are able to describe the DESY ep collider HERA data for the proton structure function at small values of the Bjorken variable $x$. A striking feature is the scaling on $\tau=Q_2^2/Q_{sat}^2(x)$ above saturation limit, corroborating recent theoretical studies.Comment: 4 pages, 2 figures. Version to be published in Physical Review Letter

Saturation physics at HERA and RHIC: An unified description

One of the frontiers of QCD which are intensely investigated in high energy experiments is the high energy (small $x$) regime, where we expect to observe the non-linear behavior of the theory. In this regime, the growth of the parton distribution should saturate, forming a Color Glass Condensate (CGC). In fact, signals of parton saturation have already been observed both in $ep$ deep inelastic scattering at HERA and in deuteron-gold collisions at RHIC. Currently, the description of the experimental data of these experiments is possible considering different phenomenological saturation models for the two processes within the CGC formalism. In this letter we analyze the universality of these dipole cross section parameterizations and verify that they are not able to describe the HERA and RHIC data simultaneously. We analyze possible improvements in the parameterizations and propose a new parametrization for the forward dipole amplitude which allows us to describe quite well the small-$x$ $ep$ HERA data on $F_2$ structure function as well as the $dAu$ RHIC data on charged hadron spectra. It is an important signature of the universality of the saturation physics.Comment: 12 pages, 4 figures. Version to be published in Physics Letters

Policy challenges for agroforestry implementation in Europe

Agroforestry (AF) is a sustainable land use practice and system that increases the ecosystem services delivery from agricultural lands compared with treeless systems. Agroforestry can be considered a practice when linked to plot scale (silvoarable, silvopasture, homegarden, woody linear landscape strips, and forest farming), and a system when associated with the global farm scale. The enhancement of the ecosystem services is associated with the use and promotion of the biodiversity caused by the presence of trees that optimizes the use of the resources if adequate species are mixed. Agroforestry can be implemented at temporal and spatial scales. At the temporal scale, the use of woody perennials to increase soil fertility is a traditional technique that improves soil health and reduces the need of using herbicides (e.g., the legume Ulex sown for 10 years in between crop cultivation). Five agroforestry practices can be implemented at the plot level: silvopasture, silvoarable/alley cropping, homegardens/kitchengardens, woody linear landscape strips, and forest farming. A farm including these practices is considered an agroforestry system working at the landscape level when several farms are mixed. In spite of the acknowledgment that AF has at the European level for being included as part of Pillars I and II, the spread of AF is limited across Europe. Four challenges, linked with technical, economic, educational, and policy development, have been identified by the AFINET thematic network that, if addressed, may foster policy adoption across the EU. This article proposes 15 different policy recommendations to overcome them and the need of developing an AF strategy for the EU.We acknowledge funding through Grant 101086563 from the European Commission (Project AF4EU, HEUROPE). This study was supported by National Funds by the FCT—Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020. NF-D was funded by the Pilot Program of the University of Santiago de Compostela (USC) for the hiring of distinguished research staff—call 2021, funded under the collaboration agreement between USC and Banco Santander, for the years 2021–2024. JJS-F was supported by the USC and the Spanish Ministry of Universities through the “Convocatoria de Recualificación del Sistema Universitario Español” on its modality “Margarita Salas”; Ministry of Universities - Recovery Transformation and Resilience Plan (funded by the European Union through the NextGenerationEU).info:eu-repo/semantics/publishedVersio

Dipole model for double meson production in two-photon interactions at high energies

In this work the double vector meson production in two-photon interactions at high energies is investigated considering saturation physics. We extend the color dipole picture for this process and study the energy and virtuality dependence of the forward differential cross section. Comparison with previous results is presented and the contribution of the different photon polarizations is estimated.Comment: 20 pages, 8 figures, 1 table. Version to be published in European Physical Jornal

Non-linear QCD dynamics and exclusive production in epep collisions

The exclusive processes in electron-proton ($ep$) interactions are an important tool to investigate the QCD dynamics at high energies as they are in general driven by the gluon content of proton which is strongly subject to parton saturation effects. In this paper we compute the cross sections for the exclusive vector meson production as well as the deeply virtual Compton scattering (DVCS) relying on the color dipole approach and considering the numerical solution of the Balitsky-Kovchegov equation including running coupling corrections. We show that the small-$x$ evolution given by this evolution equation is able to describe the DESY-HERA data and is relevant for the physics of the exclusive observables in future electron-proton colliders and in photoproduction processes to be measured in coherent interactions at the LHC.Comment: 6 pages, 4 figure

Parenting Styles and Internet Use

The Internet has become the most popular way for young people to communicate with one another. Recent data indicate that 95% of students have Internet access. This study examined the links between Internet use and the parenting styles that shape parent-child interactions. Empirical analysis showed that Internet use accounts for the majority of adolescents' leisure time. The neglecting parenting style has the strongest relationship with addictive Internet use by adolescent girls and boys. For boys, addictive Internet use is also related to a combination of different parenting styles resulting from inconsistencies and contradictions between parents

Analyse de la durabilité des entreprises agricoles Européennes

L'activité agricole européenne a un rôle important pour la sécurité alimentaire européenne et mondiale et aussi dans la préservation du monde rural. L'objectif principal de cet article est l’analyse de la durabilité agricole des vingt-huit États Membres de l'Union Européenne en termes économiques, environnementales, sociales et politiques. La information utilisée dans l’analyse correspond à la base de données Réseau D'information Comptable Agricole (RICA) de la Commission Européenne et la méthodologie inclut l'approche min-max et les méthodes multivariées, notamment l'analyse du Composant Principal et l'analyse de regroupement (Cluster). Les résultats confirment l'existence de trois groupes de pays/entreprises agricoles européens: les pays de l’Éurope Centrale, les Nouveaus Etats-Membres, et les pays Méditerranéens. Les résultats confirment également que les entreprises agricoles européennes et leurs pays respectifs presentment une durabilité moyenne. Les points-clés de la conclusion principale confirment aussi l'importance de la durabilité pour mieux ajuster les politiques agricoles entre les Etats-Membres Européens.N/

Parton Percolation and J/Psi Suppression

The geometric clustering of partons in the transverse plane of nuclear collisions leads for increasing A or sqrt(s) to percolation. In the resulting condensate, the partons are deconfined but not yet in thermal equilibrium. We discuss quarkonium dissociation in this precursor of the quark-gluon plasma, with an onset of dissociation when the saturation scale of the parton condensate reaches that of the given quarkonium state.Comment: 13 pages latex file, 7 eps figure

Thermal Dileptons at LHC

We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb collisions at LHC. Hadronic emission in the low-mass region is calculated using in-medium spectral functions of light vector mesons within hadronic many-body theory. In the intermediate-mass region thermal radiation from the Quark-Gluon Plasma, evaluated perturbatively with hard-thermal loop corrections, takes over. An important source over the entire mass range are decays of correlated open-charm hadrons, rendering the nuclear modification of charm and bottom spectra a critical ingredient.Comment: 2 pages, 2 figures, contributed to Workshop on Heavy Ion Collisions at the LHC: Last Call for Predictions, Geneva, Switzerland, 14 May - 8 Jun 2007 v2: acknowledgment include