Publications (200)440.62 Total impact
 [Show abstract] [Hide abstract]
ABSTRACT: Journal articlePhysics Letters B 09/2014; 682(45):351354. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Journal articlePhysics Letters B 09/2014; 684(23):114118. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The momentum and helicity density distributions of the strange quark sea in the nucleon are obtained in leading order from chargedkaon production in deepinelastic scattering on the deuteron. The distributions are extracted from spinaveraged K± multiplicities, and from K± and inclusive doublespin asymmetries for scattering of polarized positrons by a polarized deuterium target. The shape of the momentum distribution is softer than that of the average of the and quarks. In the region of measurement 0.02<x<0.6 and Q2>1.0 GeV2, the helicity distribution is zero within experimental uncertainties.Physics Letters B 09/2014; 666(5):446450. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The dependence on Q2 (the negative square of the 4momentum of the exchanged virtual photon) of the generalised Gerasimov–Drell–Hearn integral for the proton has been measured in the range 1.2 GeV2<Q2<12 GeV2 by scattering longitudinally polarised positrons on a longitudinally polarised hydrogen gas target. The contributions of the nucleonresonance and deep inelastic regions to this integral have been evaluated separately. The latter has been found to dominate for Q2>3 GeV2, while both contributions are important at low Q2. The total integral shows no significant deviation from a 1/Q2 behaviour in the measured Q2 range, and thus no sign of large effects due to either nucleonresonance excitations or nonleading twist.Physics Letters B 09/2014; 494(12):18. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Journal articlePhysics Letters B 09/2014; 679(2):100105. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Journal articlePhysics Letters B 09/2014; 682(45):345350. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A series of semiinclusive deepinelastic scattering measurements on deuterium, helium, neon, krypton, and xenon targets has been performed in order to study hadronization. The data were collected with the HERMES detector at the DESY laboratory using a 27.6 GeV positron or electron beam. Hadron multiplicities on nucleus A relative to those on the deuteron, , are presented for various hadrons (π+, π−, π0, K+, K−, p, and ) as a function of the virtualphoton energy ν, the fraction z of this energy transferred to the hadron, the photon virtuality Q2, and the hadron transverse momentum squared . The data reveal a systematic decrease of with the mass number A for each hadron type h. Furthermore, increases (decreases) with increasing values of ν (z), increases slightly with increasing Q2, and is almost independent of , except at large values of . For pions twodimensional distributions also are presented. These indicate that the dependences of on ν and z can largely be described as a dependence on a single variable Lc, which is a combination of ν and z. The dependence on Lc suggests in which kinematic conditions partonic and hadronic mechanisms may be dominant. The behaviour of at large constitutes tentative evidence for a partonic energyloss mechanism. The Adependence of is investigated as a function of ν, z, and of Lc. It approximately follows an Aα form with α≈0.5–0.6.Nuclear Physics B 09/2014; 780(12):127. · 3.95 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The transversetarget singlespin asymmetry for inclusive deepinelastic scattering with effectively unpolarized electron and positron beams off a transversely polarized hydrogen target was measured, with the goal of searching for a twophoton exchange signal in the kinematic range 0.007<xB<0.9 and . In two separate regions and , and for both electron and positron beams, the asymmetries are found to be consistent with zero within statistical and systematic uncertainties, which are of order 10−3 for the asymmetries integrated over xB.Physics Letters B 09/2014; 682(45):351354. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Journal articlePhysical Review C 09/2014; 81:035202. · 3.88 Impact Factor 
Article: Doublespin asymmetry in the cross section for exclusive ρ0 production in lepton–proton scattering
[Show abstract] [Hide abstract]
ABSTRACT: Evidence for a positive longitudinal doublespin asymmetry 〈A1ρ〉=0.24±0.11stat±0.02syst in the cross section for exclusive diffractive ρ0(770) vector–meson production in polarised lepton–proton scattering was observed by the HERMES experiment. The longitudinally polarised 27.56 GeV HERA positron beam was scattered off a longitudinally polarised pure hydrogen gas target. The average invariant mass of the photon–proton system has a value of 〈W〉=4.9 GeV, while the average negative squared fourmomentum of the virtual photon is 〈Q2〉=1.7 GeV2. The ratio of the present result to the corresponding spin asymmetry in inclusive deepinelastic scattering is in agreement with an early theoretical prediction based on the generalised vector–meson dominance model.Physics Letters B 09/2014; 513(34):301310. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The beamhelicity asymmetry in associated electroproduction of real photons, $ep\to e\gamma \pi N$, in the $\Delta$(1232)resonance region is measured using the longitudinally polarized HERA positron beam and an unpolarized hydrogen target. Azimuthal Fourier amplitudes of this asymmetry are extracted separately for two channels, $ep\to e\gamma \pi^0 p$ and $ep\to e\gamma \pi^+ n$, from a data set collected with a recoil detector. All asymmetry amplitudes are found to be consistent with zero.10/2013;  [Show abstract] [Hide abstract]
ABSTRACT: The present note relies on the recently published conceptual design report of the LHeC and extends the first contribution to the European strategy debate in emphasising the role of the LHeC to complement and complete the high luminosity LHC programme. The brief discussion therefore focuses on the importance of high precision PDF and $\alpha_s$ determinations for the physics beyond the Standard Model (GUTs, SUSY, Higgs). Emphasis is also given to the importance of high parton density phenomena in nuclei and their relevance to the heavy ion physics programme at the LHC.11/2012;  [Show abstract] [Hide abstract]
ABSTRACT: This document provides a brief overview of the recently published report on the design of the Large Hadron Electron Collider (LHeC), which comprises its physics programme, accelerator physics, technology and main detector concepts. The LHeC exploits and develops challenging, though principally existing, accelerator and detector technologies. This summary is complemented by brief illustrations of some of the highlights of the physics programme, which relies on a vastly extended kinematic range, luminosity and unprecedented precision in deep inelastic scattering. Illustrations are provided regarding high precision QCD, new physics (Higgs, SUSY) and electronion physics. The LHeC is designed to run synchronously with the LHC in the twenties and to achieve an integrated luminosity of O(100) fb$^{1}$. It will become the cleanest high resolution microscope of mankind and will substantially extend as well as complement the investigation of the physics of the TeV energy scale, which has been enabled by the LHC.11/2012;  [Show abstract] [Hide abstract]
ABSTRACT: We report on recent results on higher twist contributions to the unpolarized structure functions $F_2^{p,d}(x,Q^2)$ at N$^3$LO in the large $x$ region and constraints on the twist3 contribution to polarized structure function $g_2(x,Q^2)$.07/2012;  [Show abstract] [Hide abstract]
ABSTRACT: The physics programme and the design are described of a new collider for particle and nuclear physics, the Large Hadron Electron Collider (LHeC), in which a newly built electron beam of 60 GeV, up to possibly 140 GeV, energy collides with the intense hadron beams of the LHC. Compared to HERA, the kinematic range covered is extended by a factor of twenty in the negative fourmomentum squared, $Q^2$, and in the inverse Bjorken $x$, while with the design luminosity of $10^{33}$ cm$^{2}$s$^{1}$ the LHeC is projected to exceed the integrated HERA luminosity by two orders of magnitude. The physics programme is devoted to an exploration of the energy frontier, complementing the LHC and its discovery potential for physics beyond the Standard Model with high precision deep inelastic scattering measurements. These are designed to investigate a variety of fundamental questions in strong and electroweak interactions. The physics programme also includes electrondeuteron and electronion scattering in a $(Q^2, 1/x)$ range extended by four orders of magnitude as compared to previous leptonnucleus DIS experiments for novel investigations of neutron's and nuclear structure, the initial conditions of QuarkGluon Plasma formation and further quantum chromodynamic phenomena. The LHeC may be realised either as a ringring or as a linacring collider. Optics and beam dynamics studies are presented for both versions, along with technical design considerations on the interaction region, magnets and further components, together with a design study for a high acceptance detector. Civil engineering and installation studies are presented for the accelerator and the detector. The LHeC can be built within a decade and thus be operated while the LHC runs in its highluminosity phase. It thus represents a major opportunity for progress in particle physics exploiting the investment made in the LHC.Journal of Physics G Nuclear and Particle Physics 06/2012; 39(7). · 2.84 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We summarize the results of recent determinations of $\alpha_s(M_Z^2)$ in NNLO QCD analyses of the deepinelastic world data.04/2011;  [Show abstract] [Hide abstract]
ABSTRACT: Internal report  PreprintRed Report (2009),. 01/2011;  [Show abstract] [Hide abstract]
ABSTRACT: The results of a recent nexttoleading order QCD analysis of the world data on polarized deep inelastic scattering are reported. New parameterizations are derived for the quark and gluon distributions, accounting for the massive Wilson coefficient for the charm quarks, and the value of $\alpha_s(M_z^2)$ is determined with correlated errors. We obtain $\alpha_s^{\rm NLO}(M_Z^2)= 0.1132 {array}{l} + 0.0056 0.0095 {array}$. Limits on potential higher twist contributions to the structure function $g_1(x,Q^2)$ are derived. We also compare to the results obtained by other groups.AIP Conference Proceedings. 12/2010; 1369(1).  [Show abstract] [Hide abstract]
ABSTRACT: Polarisation asymmetries are measured for the hard exclusive leptoproduction of real photons from a longitudinally polarised hydrogen target. These asymmetries arise from the deeply virtual Compton scattering and BetheHeitler processes. From the data are extracted two asymmetries in the azimuthal distribution of produced real photons about the direction of the exchanged virtual photon: AUL with respect to the target polarisation and ALL with respect to the product of the beam and target polarisations. Results for both asymmetries are compared to the predictions from a generalised parton distribution model. The sin φ and cos(0φ) amplitudes observed respectively for the AUL and ALL asymmetries are compatible with the sizeable predictions from the model. Unexpectedly, a sin(2φ) modulation in the AUL asymmetry with a magnitude similar to that of the sin φ modulation is observed.Journal of High Energy Physics 06/2010; 1006((2010)):019. · 6.22 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A QCD analysis of the world data on polarized deep inelastic scattering is presented in nexttoleading order, including the heavy flavor Wilson coefficient in leading order in the fixed flavor number scheme. New parameterizations are derived for the quark and gluon distributions and the value of is determined. The impact of the variation of both the renormalization and factorization scales on the distributions and the value of αs is studied. We obtain . The first moments of the polarized twist2 parton distribution functions are calculated with correlated errors to allow for comparisons with results from lattice QCD simulations. Potential higher twist contributions to the structure function g1(x,Q2) are determined both for proton and deuteron targets.Nuclear Physics B 05/2010; · 3.95 Impact Factor
Publication Stats
2k  Citations  
440.62  Total Impact Points  
Top Journals
Institutions

2003–2014

Deutsches ElektronenSynchrotron
Hamburg, Hamburg, Germany


2012

University of Southampton
Southampton, England, United Kingdom


2009

VU University Amsterdam
 Department of Physics and Astronomy
Amsterdamo, North Holland, Netherlands


2006

University of Michigan
Ann Arbor, Michigan, United States


2003–2005

Yerevan Physics Institute
Ayrivan, Yerevan, Armenia


1991

Syracuse University
Syracuse, New York, United States 
University of Helsinki
Helsinki, Southern Finland Province, Finland


1981

Deen Dayal Rustagi College
Khandela, Rajasthan, India


1971

Austrian Academy of Sciences
 Institute for High Energy Physics
Vienna, Vienna, Austria


1970–1971

Institut für Hochenergiephysik Wien
Wien, Vienna, Austria


1969–1970

RWTH Aachen University
 III. Physikalisches Institut A: Elementarteilchenphysik
Aachen, North RhineWestphalia, Germany
