Search

After an introduction motivating the study of quarkonium production, we review the recent developments in the phenomenology of quarkonium production in inclusive scatterings of hadrons and leptons. We naturally address data and predictions relevant for the LHC, the Tevatron, RHIC, HERA, LEP, B factories and EIC. An up-to-date discussion of the contributions from feed downs within the charmonium and bottomonium families as well as from b hadrons to charmonia is also provided. This contextualises an exhaustive overview of new observables such as the associated production along with a Standard Model boson (γ , W and Z), with another quarkonium, with another heavy quark as well as with light hadrons or jets. We address the relevance of these reactions in order to improve our understanding of the mechanisms underlying quarkonium production as well as the physics of multi-parton interactions, in particular the double parton scatterings. An outlook towards future studies and facilities concludes this review. [ABSTRACT FROM AUTHOR]

The cross sections of high-energy μ + μ − pair production and paradimuonium production by a relativistic electron in the atomic field are discussed. The calculation is performed exactly in the parameters of the atomic field. Though the Coulomb corrections to the cross sections, related to the multiple Coulomb exchange of μ + , μ − and an atom, are negligible, the Coulomb corrections to the differential cross sections, related to the electron interaction with an atom, are large. However, the latter Coulomb corrections to the cross sections integrated over the final electron momentum are small. Apparently, this effect can easily be observed experimentally. Furthermore, it is shown that the asymmetry of the cross section with respect to the permutation of the momenta of μ − and μ + is large. [ABSTRACT FROM AUTHOR]

The cross section of high-energy e + e − pair production by a heavy charged particle in the atomic field is investigated in detail. We take into account the interaction with the atomic field of e + e − pair and a heavy particle as well. The calculation is performed exactly in the parameters of the atomic field. It is shown that, in contrast to the commonly accepted point of view, the cross section differential with respect to the final momentum of a heavy particle is strongly affected by the interaction of a heavy particle with the atomic field. However, the cross section integrated over the final momentum of a heavy particle is independent of this interaction. [ABSTRACT FROM AUTHOR]

We describe the electroproduction ratios of baryon–meson states from nucleon, inferring from the sea quarks in the nucleon using an extension of the quark model that takes into account the sea. As a result we provide, with no adjustable parameters, the predictions of ratios of exclusive meson–baryon final states: Λ K + , Σ ⁎ K , Σ K , p π 0 , and n π + . These predictions are in agreement with the new JLab experimental data showing that sea quarks play an important role in the electroproduction. We also predicted further ratios of exclusive reactions that can be measured and tested in future experiments. In particular, we suggested new experiments on deuterium and tritium. Such measurements can provide crucial tests of different predictions concerning the structure of nucleon and its sea quarks helping to solve an outstanding problem. Finally, we compute the so called strangeness suppression factor, λ s , that is the suppression of strange quark–antiquark pairs compared to nonstrange pairs, and we found that our finding with this simple extension of the quark model is in good agreement with the results of JLab and CERN experiments. [ABSTRACT FROM AUTHOR]

Abstract: Professor Osamu Hashimoto of Tohoku University passed away on February 3, 2012. As well as leading the nuclear physics laboratory of Tohoku University, Prof. Hashimoto contributed much to hypernuclear and strangeness nuclear physics community for years. In this decade, he devoted himself to establish the hypernuclear spectroscopy. I will review progresses of Λ hypernuclear spectroscopy with a memory of this decade which I was privileged to share with Prof. Hashimoto. [Copyright &y& Elsevier]

Abstract: A pilot experiment in the search for light gauge bosons at the spectrometer setup of the A1 collaboration at MAMI is presented. Light gauge bosons arise naturally in a wide range of theoretical approaches beyond the standard model and are in accordance with several pieces of experimental evidence not yet understood in the standard model. A first test measurement at MAMI showed that existing limits on the coupling of such a light gauge boson can be improved by nearly an order of magnitude by fixed target experiments at existing electron accelerators. [Copyright &y& Elsevier]

Abstract: Isobar models for the electromagnetic production of kaons are discussed with emphasis on the K+ photoproduction at very small kaon angles and K0 photoproduction on deuteron. Distorted-wave impuls approximation calculations of the cross sections for the electroproduction of hypernuclei are presented on the case of the 12 ΛB production. [Copyright &y& Elsevier]

Abstract: Developments in strangeness photo- and electro- production off the proton, as investigated using the CLAS system in Hall B at Jefferson Lab, are discussed in this paper. By measuring sufficient spin observables one can decompose the reaction mechanism into elementary amplitudes. We discuss progress toward this end in recent data from CLAS, including cross sections and spin observables. We next discuss new results on the mass distribution of the Λ(1405), which shows signs of being a composite meson-baryon object of mixed isospin. The work on other hyperons such as the Ξ resonances will be mentioned, and future prospects outlined. [Copyright &y& Elsevier]

Abstract: We examine the space–time evolution of (pre-)hadron production within the Lund string fragmentation model. The complete four-dimensional information of the string breaking vertices and the meeting points of the prehadron constituents are extracted for each single event in Monte Carlo simulations using the Jetset-part of Pythia. We discuss the implication on the deep inelastic lepton scattering experiments at HERMES as well as on observables in ultra-relativistic heavy ion collisions at RHIC, using Pythia also for modeling the hard part of the interaction. [Copyright &y& Elsevier]

Abstract: In a framework for non-perturbative QCD calculation of high energy processes, the amplitudes for photo- and electroproduction of vector mesons are written as integrals of the overlap product of photon and vector meson wave functions, multiplied by the amplitude for the scattering of dipole pairs off the proton. For sizes of the overlap functions that are smaller than the typical ranges of the interaction of the dipoles with the proton, the amplitudes factorize in the form of integrals, here called overlap strengths, formed only with the overlap of the wave functions times the square of the dipole separation. The integration is extended over the light front coordinates describing the dipoles. With this result, the overlap strengths contain all dependence of the observables. We show the importance of this factorization in the description of the experimental data for all S-wave vector mesons. [Copyright &y& Elsevier]

A parameter-free, nonperturbative calculation of the ΔNγ electromagnetic transition amplitudes GM*(q2), GE*(q2), and the resonant multipole ratio REM(q2)≡E1+3/2(q2)/M1+3/2(q2) is performed in terms of the well-known nucleon isovector Sachs form factor GMV. Our methods are fully relativistic with conservation of the electromagnetic current guaranteed. We find that GM*(q2) decreases more rapidly than the nucleon dipole form factor when -q2≳1 GeV2/c2 and that REM(q2) remains small even for very high four-momentum transfer implying that the perturbative QCD prediction REM(q2)→1 is purely asymptotic and is valid only for extremely high &z.sfnc;q2&z.sfnc;. [Copyright &y& Elsevier]

We investigate hadron formation in deep inelastic lepton scattering on N, Kr and Xe nuclei in the kinematic regime of the HERMES experiment. The elementary electron–nucleon interaction is described within the event generator PYTHIA while a full coupled-channel treatment of the final state interactions is included by means of a BUU transport model. We find a good agreement with the measured charged hadron multiplicity ratio RMh for N and Kr targets by accounting for the deceleration and absorption of the primarily produced particles as well as for the creation of secondary hadrons in the final state interactions. [Copyright &y& Elsevier]

A nonperturbative calculation of elastic electroproduction of the J/ψ meson is presented and compared to the experimental data. Our model describes well the observed dependences of the cross sections on the photon virtuality Q2 and on the energy, and the measured ratio R=σL/σT of longitudinal to transverse cross sections. [Copyright &y& Elsevier]

Analytic expressions for electron distributions in bremsstrahlung and virtual photon radiation are derived and discussed. The results are used to investigate possible electron scattering geometries which maximize the virtual photon production at forward angles while limiting bremsstrahlung to acceptable values. [Copyright &y& Elsevier]

Eta photo- and electroproduction on the nucleon is studied using an isobar model. The model contains Born terms, and contributions from vector-meson exchanges and nucleon resonances. Our results are compared with recent eta-photoproduction data for differential and total cross sections, beam asymmetry, and target asymmetry, as well as electroproduction data. Besides the dominant S11(1535) resonance, we show that the second S11 resonance, S11(1650), is also necessary to be included in order to extract S11(1535) resonance parameters properly. In addition, the beam asymmetry data allow us to extract very small (<0.1%) N&ast;→ηN decay branching ratios of the D13(1520) and F15(1680) resonances because of the overwhelming s-wave dominance. This model (ETA-MAID) is implemented as a part of the MAID program (the MAID program can be accessed from the webpage: http://www.kph.uni-mainz.de/MAID/maid.html). [Copyright &y& Elsevier]