E. Reya

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Papers by E. Reya

CERN Accelerating science

2.3 Non-Perturbative Operator/Current Algebra

Introduction 2. The Structure Function gl and the Spin of the Nucleon 2.1 The Large Total Sea-Qua... more Introduction 2. The Structure Function gl and the Spin of the Nucleon 2.1 The Large Total Sea-Quark Polarization 2.2 The Large Total Gluon Polarization 2.3 Non-Perturbative Operator/Current Algebra Approaches and Estimates 2.4 Phenomenological Signatures for .Dog and .Doq 3. The Transverse Spin Structure Function g2 4. Transverse Chiral-Odd Structure Functions 5.

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On the charged current neutrino-nucleon total cross section at high energies

We evaluate the charged current neutrino-nucleon total cross section up to neutrino energies of 1... more

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NNLO of QCD

Utilizing recent DIS measurements and data on hadronic dilepton production we determine at NNLO (... more Utilizing recent DIS measurements and data on hadronic dilepton production we determine at NNLO (3-loop) of QCD the dynamical parton distributions of the nucleon generated radiatively from valencelike positive input distributions at an optimally chosen low resolution scale (Q 2 0 < 1 GeV 2) by employing the "fixed flavor number factorization scheme" (FFNS). These are compared with "standard" NNLO distributions, generated at some fixed and higher resolution scale (Q 2 0 > 1 GeV 2). The NNLO corrections imply in both approaches an improved value of χ 2 , typically χ 2 NNLO ∼ 0.9χ 2 NLO. The dynamical NNLO uncertainties are somewhat smaller than the NLO ones and both are, as expected, smaller than those of their "standard" counterparts. The dynamical predictions for F L (x, Q 2) become perturbatively stable already at Q 2 = 2-3 GeV 2 , where precision measurements could even delineate NNLO effects in the very small-x region. We obtain α s (M 2 Z) = 0.1124 ± 0.0020 to be compared with 0.1145 ± 0.0018 at NLO. Using these NNLO dynamical parton distributions in the FFNS as input, we generate radiatively parton distributions in the "variable flavor number factorization scheme" (VFNS) as well, where also the heavy quark flavors (c,b,t) become massless partons within the nucleon. Only within the VFNS are NNLO calculations feasible at present, since the required partonic subprocesses are available only in the approximation of massless initial-state partons. The NNLO predictions for gauge boson production are typically larger (by more than 1σ) than the NLO ones, and rates at LHC energies can be predicted with an accuracy of about 5%, whereas at Tevatron they are more than 2σ above the NLO ones. The NNLO predictions for SM Higgs boson production via the dominant gluon fusion process have a total (PDFs and scale) uncertainty of about 10% at LHC which almost doubles at the lower Tevatron energies; these predictions are typically about 20% larger than the ones at NLO but the total uncertainty bands overlap.

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Duality predictions for the production of heavy quark systems in QCD

Physics Letters B, 1978

Abstract Using partonic semi-local duality ideas combined with QCD we derive absolute, parameter-... more Abstract Using partonic semi-local duality ideas combined with QCD we derive absolute, parameter-free predictions for the cross sections of heavy quarkonia (J/ψ, ψ′, ′, …) production in purely hadronic collisions as well as in photoproduction proces We also discuss “open” charm (D D ) production and show how the CERN SPS beam dump measurements at √s = 27.4 GeV can be naturally reconciled with the predictions of QCD; similarly the recent ISR data are in good agreement with QCD.

Light gauge fermions and scalar-electron pair production in e+e- annihilation

Physical Review D, 1985

$Research paper thumbnail of i • III•••IIUIII \ o 1160 0026060 8 \ On Dynamically Generated Partons /y in Hadrons and Photons$

i • III•••IIUIII \ o 1160 0026060 8 \ On Dynamically Generated Partons /y in Hadrons and Photons

The perturbative properties of parton distributions generated radiatively from a valence-like inp... more The perturbative properties of parton distributions generated radiatively from a valence-like input at some low resolution scale are discussed with the aim of explaining the physical aspects underlying the reliability of the predicted distributions in the small-x region. Aspects of higher-twist (shadowing) effects as well as small-x resummations are discussed, and possible implications for lattice calculations are pointed out. r, LY The original attempt

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On the transport equations of cosmic neutrinos passing through Earth and secondary nu_mu fluxes

The convergence of the iterative solutions of the transport equations of cosmic muon and tau neut... more The convergence of the iterative solutions of the transport equations of cosmic muon and tau neutrinos propagating through Earth is studied and analyzed. For achieving a fast convergence of the iterative solutions of the coupled transport equations of nu_tau, nubar_tau and the associated tau^± fluxes, a new semi-analytic input algorithm is presented where the peculiar tau-decay contributions are implemented already in the initial zeroth order input. Furthermore, the common single transport equation for muon neutrinos is generalized by taking into account the contributions of secondary nu_mu and nubar_mu fluxes due to the prompt tau-decay tau -> nu_mu initiated by the associated tau flux. Differential and total nadir angle integrated upward-going mu^- + mu^+ event rates are presented for underground neutrino telescopes and compared with the muon rates initiated by the primary nu_mu, nu_tau and tau fluxes.

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Radiatively Generated Isospin Violations in the Nucleon

arXiv: High Energy Physics - Phenomenology, 2005

Isospin violating valence and sea distributions are evaluated due to QED leading O(�) corrections... more Isospin violating valence and sea distributions are evaluated due to QED leading O(�) corrections to the standard QCD evolution equations. Unique perturbative predictions are obtained within the radiative parton model, and confirm earlier results. Nonperturbative contributions have been estimated and depend on a single free parameter chosen to be the current quark mass. The relevance of our predictions for extracting sin 2 �W from DIS �(¯�)N data (‘NuTeV anomaly’) is discussed as well.

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Top physics at LHC

Polarized structure functions and the spin of the proton

Lecture Notes in Physics

The generalized Veneziano model for charged pion photoproduction

Nuclear Physics B, 1971

Abstract Charged pion photoproduction is investigated in the framework of Veneziano B 5 amplitude... more Abstract Charged pion photoproduction is investigated in the framework of Veneziano B 5 amplitudes using Sugawara's “spurion” technique in order to introduce fixed J -plane poles. The Regge exchanges are taken to be evasive. The agreement with experiment for the differential cross section, the π − π + ratio and the polarisation asymmetries for photon energies between 3.4 and 18 GeV is quite reasonable.

The Lamb shift contribution of very light millicharged particles

The leading order vacuum polarization contribution of very light millicharged fermions and scalar... more The leading order vacuum polarization contribution of very light millicharged fermions and scalar (spin-0) particles with charge \epsilon e and mass \mu to the Lamb shift of the hydrogen atom is shown to imply universal, i.e. \mu-independent, upper bounds on \epsilon: \epsilon \lsim 10^{-4} for \mu \lsim 1 keV in the case of fermions, and for scalars this bound is increased by a factor of 2. This is in contrast to expectations based on the commonly used approximation to the Uehling potential relevant only for conventionally large fermion (and scalar) masses.

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A critical appraisal and evaluation of modern PDFs

The European Physical Journal C

We review the present status of the determination of parton distribution functions (PDFs) in the ... more We review the present status of the determination of parton distribution functions (PDFs) in the light of the precision requirements for the LHC in Run 2 and other future hadron colliders. We provide brief reviews of all currently available PDF sets and use them to compute cross sections for a number of benchmark processes, including Higgs boson production in gluon-gluon fusion at the LHC. We show that the differences in the predictions obtained with the various PDFs are due to particular theory assumptions made in the fits of those PDFs. We discuss PDF uncertainties in the kinematic region covered by the LHC and on averaging procedures for PDFs, such as advocated by the PDF4LHC15 sets, and provide recommendations for the usage of PDF sets for theory predictions at the LHC. Contents

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Paarungseffekte und Neutron-Proton-Oberflächendelta-Restwechselwirkung in sphärischen Kernen ungerader Massenzahl

Zeitschrift für Naturforschung A, 1969

Assuming a surface delta interaction (SDI) between identical as well as between non-identical nuc... more Assuming a surface delta interaction (SDI) between identical as well as between non-identical nuclei, we investigate the pairing properties of spherical odd mass (s.o.m.) nuclei in the regions 40 ≦ Z ≦ 49, 53 ≦ N 70 and 51 ≦ Z ≦ 59, 64 ≦ 82. Applying Bogoliubov’s transformation to the neutrons and protons separately and applying the compensation principle we arrive at the coupled system of BCS equations. Determining the quasi-particle energies and the chemical potentials of the neutron and proton system by numerical solution of these equations, we find rather impressive agreement between theory and experiment. We further find that for a SDI-model the incorporation of n-p forces seems to be both necessary and sufficient for a detailed understanding of the low-lying energy levels in the above mentioned regions. In addition, the SDI-model has the advantage of analytic simplicity as compared to more refined realistic (multiparameter) models

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Supersymmetry in two-photon processes

Physics Letters B, 1983

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The spin content of nucleons

Physics Letters B, 1991

Abstract Recent constraints on the unpolarized strange quark and gluon distributions in the nucle... more

Short-Distance Behavior of Spontaneously Broken Quantum Chromodynamics

Physical Review Letters, 1982

Light, colored scalars are shown to preserve all presently observed short-distance properties of ... more Light, colored scalars are shown to preserve all presently observed short-distance properties of quantum chromodynamics even when belonging to large multiplets of SU(3)/sub c/. However, light-scalar pair production by gluon fusion dominates hadronic high-p/sub T/ single-particle inclusive production cross sections at p-barp collider energies (..sqrt..s = 540 GeV) and two-jet production even at ..sqrt..sroughly-equal50--60 GeV. Embedding in a unified SU(5) theory requires many scalars to be superheavy in order to preserve asymptotic freedom below the unification mass.

Testing unified gauge theories with polarized-electron-nucleon elastic scattering

Physical Review D, 1978

The parity-violating left-right asymmetry in longitudinally-polarized-electron elastic scattering... more The parity-violating left-right asymmetry in longitudinally-polarized-electron elastic scattering off unpolarized nucleons is studied in the contest of unified gauge theories of the weak and electromagnetic interactions. Predictions of a large variety of gauge models of present interest are given. It is shown that measurements at low electron beam energies, typically 150 to 800 MeV, and over a wide range of scattering, angles, are of particular importance for distinguishing between various SU(2) ⊗ U(1) models and between models based on larger gauge groups, such as SU(2)L⊗SU(2)R⊗U(1) and SU(3) ⊗ U(1) theories.

Spin-dependent structure functions of real and virtual photons

The European Physical Journal C, 2001

E. Reya

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