F Zomer

Publications (536)117.51 Total impact

• Source

  Available from: M. V. Galynskii

  Dataset: IJMP TESLA 2004

  B. Badelek, C. Blochinger, J.Blumlein, E. Boos, R. Brinkmann, H. Burkhardt, P. Bussey, C. Carimalo, J. Chyla, A. K. Ciftci, [......], I. Watanabe, T. Wengler, I. Will, S. Wipf, O. Yavas, K. Yokoya, M. Yurkov, A. F. Zarnecki, P. Zerwas, F. Zomer
• Article: On the Relation of the LHeC and the LHC

  J. L. Abelleira Fernandez, C. Adolphsen, P. Adzic, A. N. Akay, H. Aksakal, J. L. Albacete, B. Allanach, S. Alekhin, P. Allport, V. Andreev, [......], U. A. Wiedemann, U. Wienands, F. Willeke, B. -W. Xiao, V. Yakimenko, A. F. Zarnecki, Z. Zhang, F. Zimmermann, R. Zlebcik, F. Zomer
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  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;
• Article: A Large Hadron Electron Collider at CERN

  J. L. Abelleira Fernandez, C. Adolphsen, P. Adzic, A. N. Akay, H. Aksakal, J. L. Albacete, B. Allanach, S. Alekhin, P. Allport, V. Andreev, [......], U. A. Wiedemann, U. Wienands, F. Willeke, B. -W. Xiao, V. Yakimenko, A. F. Zarnecki, Z. Zhang, F. Zimmermann, R. Zlebcik, F. Zomer
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  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 electron-ion 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;
• Article: Combination and QCD Analysis of Charm Production Cross Section Measurements in Deep-Inelastic ep Scattering at HERA

  H. Abramowicz, I. Abt, L. Adamczyk, M. Adamus, R. Aggarwal, C. Alexa, V. Andreev, S. Antonelli, P. Antonioli, A. Antonov, [......], W. Zeuner, Z. Zhang, B. O. Zhautykov, N. Zhmak, A. Zichichi, R. Žlebčík, H. Zohrabyan, Z. Zolkapli, F. Zomer, D. S. Zotkin
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  ABSTRACT: Measurements of open charm production cross sections in deep-inelastic ep scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections sigma_red^{c\bar{c}} for charm production are obtained in the kinematic range of photon virtuality 2.5<Q2<2000 GeV2 and Bjorken scaling variable 0.00003<x<0.05. The combination method accounts for the correlations of the systematic uncertainties among the different data sets. The combined charm data together with the combined inclusive deep-inelastic scattering cross sections from HERA are used as input for a detailed NLO QCD analysis to study the influence of different heavy flavour schemes on the parton distribution functions. The optimal values of the charm mass as a parameter in these different schemes are obtained. The implications on the NLO predictions for W^{\pm} and Z production cross sections at the LHC are investigated. Using the fixed flavour number scheme, the running mass of the charm quark is determined.
  11/2012;
• Article: A Large Hadron Electron Collider at CERN: Report on the Physics and Design Concepts for Machine and Detector

  J. L. Abelleira Fernandez, C. Adolphsen, A. N. Akay, H. Aksakal, J. L. Albacete, S. Alekhin, P. Allport, V. Andreev, R. B. Appleby, E. Arikan, [......], U. A. Wiedemann, U. Wienands, F. Willeke, B. -W. Xiao, V. Yakimenko, A. F. Zarnecki, Z. Zhang, F. Zimmermann, R. Zlebcik, F. Zomer
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  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 four-momentum 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 electron-deuteron and electron-ion scattering in a $(Q^2, 1/x)$ range extended by four orders of magnitude as compared to previous lepton-nucleus DIS experiments for novel investigations of neutron's and nuclear structure, the initial conditions of Quark-Gluon Plasma formation and further quantum chromodynamic phenomena. The LHeC may be realised either as a ring-ring or as a linac-ring 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 high-luminosity phase. It thus represents a major opportunity for progress in particle physics exploiting the investment made in the LHC.
  06/2012;
• Source

  Available from: Andreas Werner Jung

  Article: Search for squarks in R-parity violating supersymmetry in ep collisions at HERA

  The Collaboration, F. D. Aaron, C. Alexa, V. Andreev, S. Backovic, A. Baghdasaryan, S. Baghdasaryan, E. Barrelet, W. Bartel, K. Begzsuren, [......], Y. Vazdik, M. von den Driesch, D. Wegener, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, H. Zohrabyan, F. Zomer
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  ABSTRACT: A search for squarks in R-parity violating supersymmetry is performed in e ± p collisions at HERA using the H1 detector. The full data sample taken at a centre-of-mass energy Ös=319\sqrt{s}=319GeV is used for the analysis, corresponding to an integrated luminosity of 255pb−1 of e + p and 183pb−1 of e − p collision data. The resonant production of squarks via a Yukawa coupling λ′ is considered, taking into account direct and indirect R-parity violating decay modes. Final states with jets and leptons are investigated. No evidence for squark production is found and mass dependent limits on λ′ are obtained in the framework of the Minimal Supersymmetric Standard Model and in the Minimal Supergravity Model. In the considered part of the parameter space, for a Yukawa coupling of electromagnetic strength λ′=0.3, squarks of all flavours are excluded up to masses of 275GeV at 95% confidence level, with down-type squarks further excluded up to masses of 290GeV.
  European Physical Journal C 04/2012; 71(3):1-16. · 3.63 Impact Factor
• Article: Inclusive D*± meson and associated dijet production in deep-inelastic scattering at HERA

  A. Aktas, V. Andreev, T. Anthonis, B. Antunovic, S. Aplin, A. Asmone, A. Astvatsatourov, A. Babaev, S. Backovic, A. Baghdasaryan, [......], J. Zálešák, Z. Zhang, A. Zhelezov, A. Zhokin, Y.C. Zhu, J. Zimmermann, T. Zimmermann, H. Zohrabyan, F. Zomer, The Collaboration
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  ABSTRACT: Inclusive D*± production is measured in deep-inelastic ep scattering at HERA with the H1 detector. In addition, the production of dijets in events with a D*± meson is investigated. The analysis covers values of photon virtuality 2 ≤ Q2 ≤ 100GeV2 and of inelasticity 0.05≤y≤0.7. Differential cross sections are measured as a function of Q2 and x and of various D*± meson and jet observables. Within the experimental and theoretical uncertainties all measured cross sections are found to be adequately described by next-to-leading order (NLO) QCD calculations, based on the photon–gluon fusion process and DGLAP evolution, without the need for an additional resolved component of the photon beyond what is included at NLO. A reasonable description of the data is also achieved by a prediction based on the CCFM evolution of partons involving the kT-unintegrated gluon distribution of the proton.
  European Physical Journal C 04/2012; 51(2):271-287. · 3.63 Impact Factor
• Article: Measurement of the inclusive e±p scattering cross section at high inelasticity y and of the structure function FL

  The Collaboration, F. D. Aaron, C. Alexa, V. Andreev, S. Backovic, A. Baghdasaryan, S. Baghdasaryan, E. Barrelet, W. Bartel, O. Behrend, [......], Y. Vazdik, M. von den Driesch, D. Wegener, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, H. Zohrabyan, F. Zomer
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  ABSTRACT: A measurement is presented of the inclusive neutral current e ± p scattering cross section using data collected by the H1 experiment at HERA during the years 2003 to 2007 with proton beam energies E p of 920, 575, and 460GeV. The kinematic range of the measurement covers low absolute four-momentum transfers squared, 1.5GeV2<Q 2<120GeV2, small values of Bjorken x, 2.9⋅10−5<x<0.01, and extends to high inelasticity up to y=0.85. The structure function F L is measured by combining the new results with previously published H1 data at E p =920GeV and E p =820GeV. The new measurements are used to test several phenomenological and QCD models applicable in this low Q 2 and low x kinematic domain.
  European Physical Journal C 04/2012; 71(3):1-50. · 3.63 Impact Factor
• Source

  Available from: Andreas Werner Jung

  Article: Measurement of leading neutron production in deep-inelastic scattering at HERA

  The Collaboration, F. D. Aaron, C. Alexa, V. Andreev, B. Antunovic, S. Backovic, A. Baghdasaryan, E. Barrelet, W. Bartel, K. Begzsuren, [......], D. Wegener, C. Wissing, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, F. Zomer
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  ABSTRACT: The production of leading neutrons, where the neutron carries a large fraction x L of the incoming proton’s longitudinal momentum, is studied in deep-inelastic positron-proton scattering at HERA. The data were taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 122pb−1. The semi-inclusive cross section is measured in the phase space defined by the photon virtuality 6<Q 2<100GeV2, Bjorken scaling variable 1.5⋅10−4<x<3⋅10−2, longitudinal momentum fraction 0.32<x L <0.95 and neutron transverse momentum p T <0.2GeV. The leading neutron structure function, F2LN(3)(Q2,x,xL)F_{2}^{LN(3)}(Q^{2},x,x_{L}), and the fraction of deep-inelastic scattering events containing a leading neutron are studied as a function of Q 2, x and x L . Assuming that the pion exchange mechanism dominates leading neutron production, the data provide constraints on the shape of the pion structure function.
  European Physical Journal C 04/2012; 68(3):381-399. · 3.63 Impact Factor
• Article: Three- and four-jet production at low x at HERA

  F.D. Aaron, A. Aktas, C. Alexa, V. Andreev, B. Antunovic, S. Aplin, A. Asmone, A. Astvatsatourov, S. Backovic, A. Baghdasaryan, [......], J. Žáček, J. Zálešák, Z. Zhang, A. Zhelezov, A. Zhokin, Y.C. Zhu, T. Zimmermann, H. Zohrabyan, F. Zomer, The Collaboration
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  ABSTRACT: Three- and four-jet production is measured in deep-inelastic ep scattering at low x and Q2 with the H1 detector using an integrated luminosity of 44.2pb-1. Several phase space regions are selected for the three-jet analysis in order to study the underlying parton dynamics from global topologies to the more restrictive regions of forward jets close to the proton direction. The measurements of cross sections for events with at least three jets are compared to fixed order QCD predictions of O(a\texts2){\mathcal{O}}(\alpha_{{\text{s}}}^2) and O(a\texts3){\mathcal{O}}(\alpha_{{\text{s}}}^3) and with Monte Carlo simulation programs where higher order effects are approximated by parton showers. A good overall description is provided by the O(a\texts3){\mathcal{O}}(\alpha_{{\text{s}}}^3) calculation. Too few events are predicted at the lowest x∼10-4, especially for topologies with two forward jets. This hints to large contributions at low x from initial state radiation of gluons close to the proton direction and unordered in transverse momentum. The Monte Carlo program in which gluon radiation is generated by the colour dipole model gives a good description of both the three- and the four-jet data in absolute normalisation and shape.
  European Physical Journal C 04/2012; 54(3):389-409. · 3.63 Impact Factor
• Article: Measurement of charm and beauty jets in deep inelastic scattering at HERA

  The Collaboration, F. D. Aaron, C. Alexa, V. Andreev, S. Backovic, A. Baghdasaryan, E. Barrelet, W. Bartel, K. Begzsuren, A. Belousov, [......], Y. Vazdik, M. von den Driesch, D. Wegener, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, H. Zohrabyan, F. Zomer
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  ABSTRACT: Measurements of cross sections for events with charm and beauty jets in deep inelastic scattering at HERA are presented. Events with jets of transverse energy $E_{T}^{\mathrm{jet}}>6$E_{T}^{\mathrm{jet}}>6GeV and pseudorapidity −1.0<η jet<1.5 in the laboratory frame are selected in the kinematic region of photon virtuality Q 2>6GeV2 and inelasticity variable 0.07<y<0.625. Measurements are also made requiring a jet in the Breit frame with $E_{T}^{*{\mathrm{jet}}}>6$E_{T}^{*{\mathrm{jet}}}>6GeV. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189pb−1. The numbers of charm and beauty jets are determined using variables reconstructed using the H1 vertex detector with which the impact parameters of the tracks to the primary vertex and the position of secondary vertices are measured. The measurements are compared with QCD predictions and with previous measurements where heavy flavours are identified using muons.
  European Physical Journal C 04/2012; 71(1):1-21. · 3.63 Impact Factor
• Article: Jet production in ep collisions at high Q2 and determination of αs

  The Collaboration, F. D. Aaron, C. Alexa, K. Alimujiang, V. Andreev, B. Antunovic, A. Asmone, S. Backovic, A. Baghdasaryan, E. Barrelet, [......], Ch. Wissing, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, F. Zomer, R. Zus
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  ABSTRACT: The production of jets is studied in deep-inelastic e ± p scattering at large negative four momentum transfer squared 150<Q 2<15000GeV2 using HERA data taken in 1999–2007, corresponding to an integrated luminosity of 395pb−1. Inclusive jet, 2-jet and 3-jet cross sections, normalised to the neutral current deep-inelastic scattering cross sections, are measured as functions of Q 2, jet transverse momentum and proton momentum fraction. The measurements are well described by perturbative QCD calculations at next-to-leading order corrected for hadronisation effects. The strong coupling as determined from these measurements is as(MZ)=0.1168±0.0007(exp.)+0.0046-0.0030(th.)±0.0016\alpha_{s}(M_{Z})=0.1168\pm0.0007\,\mathrm{(exp.)}{}^{+0.0046}_{-0.0030}\,\mathrm{(th.)}\pm 0.0016 (PDF).
  European Physical Journal C 04/2012; 65(3):363-383. · 3.63 Impact Factor
• Article: Diffractive electroproduction of ρ and ϕ mesons at HERA

  The Collaboration, F. D. Aaron, M. Aldaya Martin, C. Alexa, V. Andreev, B. Antunovic, A. Asmone, S. Backovic, A. Baghdasaryan, E. Barrelet, [......], Ch. Wissing, E. Wünsch, J. Žáček, J. Záleák, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, F. Zomer, R. Zus
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  ABSTRACT: Diffractive electroproduction of ρ and ϕ mesons is measured at HERA with the H1 detector in the elastic and proton dissociative channels. The data correspond to an integrated luminosity of 51 pb−1. About 10500 ρ and 2000 φ events are analysed in the kinematic range of squared photon virtuality 2.5 ≤ Q 2 ≤ 60 GeV2, photon-proton centre of mass energy 35 ≤ W ≤ 180 GeV and squared four-momentum transfer to the proton |t| ≤ 3 GeV2. The total, longitudinal and transverse cross sections are measured as a function of Q 2, W and |t|. The measurements show a transition to a dominantly “hard” behaviour, typical of high gluon densities and small q[`(q)] q\overline q dipoles, for Q 2 larger than 10 to 20 GeV2. They support flavour independence of the diffractive exchange, expressed in terms of the scaling variable (Q 2+M 2 V )/4, and proton vertex factorisation. The spin density matrix elements are measured as a function of kinematic variables. The ratio of the longitudinal to transverse cross sections, the ratio of the helicity amplitudes and their relative phases are extracted. Several of these measurements have not been performed before and bring new information on the dynamics of diffraction in a QCD framework. The measurements are discussed in the context of models using generalised parton distributions or universal dipole cross sections. KeywordsLepton-Nucleon Scattering
  Journal of High Energy Physics 04/2012; 2010(5):1-111. · 5.83 Impact Factor
• Article: Strangeness production at low Q2 in deep-inelastic ep scattering at HERA

  Collaboration, F. D. Aaron, C. Alexa, V. Andreev, B. Antunovic, S. Aplin, A. Asmone, A. Astvatsatourov, A. Bacchetta, S. Backovic, [......], V. Yeganov, J. Žáček, J. Zálešák, Z. Zhang, A. Zhelezov, A. Zhokin, Y. C. Zhu, T. Zimmermann, H. Zohrabyan, F. Zomer
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  ABSTRACT: The production of neutral strange hadrons is investigated using deep-inelastic scattering events measured with the H1 detector at HERA. The measurements are made in the phase space defined by the negative four-momentum transfer squared of the photon 2<Q 2<100 GeV2 and the inelasticity 0.1<y<0.6. The K s 0 and \varLambda([`\varLambda])\varLambda(\bar{\varLambda}) production cross sections and their ratios are determined. K s 0 production is compared to the production of charged particles in the same region of phase space. The Λ– [`\varLambda]\bar{\varLambda} asymmetry is also measured and found to be consistent with zero. Predictions of leading order Monte Carlo programs are compared to the data.
  European Physical Journal C 04/2012; 61(2):185-205. · 3.63 Impact Factor
• Article: Prompt photons in photoproduction at HERA

  The Collaboration, F. D. Aaron, M. Aldaya Martin, C. Alexa, V. Andreev, B. Antunovic, S. Backovic, A. Baghdasaryan, E. Barrelet, W. Bartel, [......], Ch. Wissing, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, F. Zomer, R. Zus
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  ABSTRACT: The production of prompt photons is measured in the photoproduction regime of electron–proton scattering at HERA. The analysis is based on a data sample corresponding to a total integrated luminosity of 340pb−1 collected by the H1 experiment. Cross sections are measured for photons with transverse momentum and pseudorapidity in the range 6 < ETg < 156
  European Physical Journal C 04/2012; 66(1):17-33. · 3.63 Impact Factor
• Article: Measurement of the charm and beauty structure functions using the H1 vertex detector at HERA

  The Collaboration, F. D. Aaron, M. Aldaya Martin, C. Alexa, K. Alimujiang, V. Andreev, B. Antunovic, A. Asmone, S. Backovic, A. Baghdasaryan, [......], C. Wissing, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, F. Zomer, R. Zus
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  ABSTRACT: Inclusive charm and beauty cross sections are measured in e − p and e + p neutral current collisions at HERA in the kinematic region of photon virtuality 5≤Q 2≤2000GeV2 and Bjorken scaling variable 0.0002≤x≤0.05. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189pb−1. The numbers of charm and beauty events are determined using variables reconstructed by the H1 vertex detector including the impact parameter of tracks to the primary vertex and the position of the secondary vertex. The measurements are combined with previous data and compared to QCD predictions.
  European Physical Journal C 04/2012; 65(1):89-109. · 3.63 Impact Factor
• Article: Search for baryonic resonances decaying to Ξπ in deep-inelastic scattering at HERA

  A. Aktas, C. Alexa, V. Andreev, T. Anthonis, B. Antunovic, S. Aplin, A. Asmone, A. Astvatsatourov, S. Backovic, A. Baghdasaryan, [......], J. Žáček, J. Zálešák, Z. Zhang, A. Zhelezov, A. Zhokin, Y.C. Zhu, T. Zimmermann, H. Zohrabyan, F. Zomer, The Collaboration
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  ABSTRACT: A search for narrow baryonic resonances decaying into Ξ-π- or Ξ-π+ and their antiparticles is carried out with the H1 detector using deep inelastic scattering events at HERA in the range of negative photon four-momentum transfer squared 2 < Q2 < 100GeV2. No signal is observed for a new baryonic state in the mass range 1600–2300MeV in either the doubly charged or the neutral decay channels. The known Ξ(1530)0 is observed through its decay mode into Ξ-π+. Upper limits are given on the ratio of the production rates of new baryonic states, such as the hypothetical pentaquark states Ξ– 5q or Ξ0 5q, relative to the Ξ(1530)0 baryon state.
  European Physical Journal C 04/2012; 52(3):507-514. · 3.63 Impact Factor
• Article: Inelastic production of J/ψ mesons in photoproduction and deep inelastic scattering at HERA

  The Collaboration, F. D. Aaron, C. Alexa, V. Andreev, B. Antunovic, S. Backovic, A. Baghdasaryan, E. Barrelet, W. Bartel, K. Begzsuren, [......], D. Wegener, Ch. Wissing, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, F. Zomer
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  ABSTRACT: A measurement is presented of inelastic photo- and electroproduction of J/ψ mesons in ep scattering at HERA. The data were recorded with the H1 detector in the period from 2004 to 2007. Single and double differential cross sections are determined and the helicity distributions of the J/ψ mesons are analysed. The results are compared to theoretical predictions in the colour singlet model and in the framework of non-relativistic QCD. Calculations in the colour singlet model using ak T factorisation ansatz are able to give a good description of the data, while colour singlet model calculations to next-to-leading order in collinear factorisation underestimate the data.
  European Physical Journal C 04/2012; 68(3):401-420. · 3.63 Impact Factor
• Article: Measurement of the inclusive ep scattering cross section at low Q2 and x at HERA

  The Collaboration, F. D. Aaron, C. Alexa, V. Andreev, B. Antunovic, S. Aplin, A. Asmone, A. Astvatsatourov, S. Backovic, A. Baghdasaryan, [......], D. Wegener, Ch. Wissing, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, F. Zomer
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  ABSTRACT: A measurement of the inclusive ep scattering cross section is presented in the region of low momentum transfers, 0.2 GeV2 ≤Q 2≤12 GeV2, and low Bjorken x, 5⋅10−6≤x≤0.02. The result is based on two data sets collected in dedicated runs by the H1 Collaboration at HERA at beam energies of 27.6 GeV and 920 GeV for positrons and protons, respectively. A combination with data previously published by H1 leads to a cross section measurement of a few percent accuracy. A kinematic reconstruction method exploiting radiative ep events extends the measurement to lower Q 2 and larger x. The data are compared with theoretical models which apply to the transition region from photoproduction to deep inelastic scattering.
  European Physical Journal C 04/2012; 63(4):625-678. · 3.63 Impact Factor
• Article: Events with isolated leptons and missing transverse momentum and measurement of W production at HERA

  The Collaboration, F. D. Aaron, C. Alexa, V. Andreev, B. Antunovic, S. Aplin, A. Asmone, A. Astvatsatourov, S. Backovic, A. Baghdasaryan, [......], D. Wegener, Ch. Wissing, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, F. Zomer
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  ABSTRACT: Events with high energy isolated electrons, muons or tau leptons and missing transverse momentum are studied using the full e ± p data sample collected by the H1experiment at HERA, corresponding to an integrated luminosity of 474pb−1. Within the Standard Model, events with isolated leptons and missing transverse momentum mainly originate from the production of single W bosons. The total single W boson production cross section is measured as 1.14±0.25(stat.)±0.14(sys.)pb, in agreement with the Standard Model expectation. The data are also used to establish limits on the WW γ gauge couplings and for a measurement of the W boson polarisation.
  European Physical Journal C 04/2012; 64(2):251-271. · 3.63 Impact Factor