Publications (189)487.9 Total impact
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ABSTRACT: A search for excited electrons is performed using the full e±p data sample collected by the H1 experiment at HERA, corresponding to a total luminosity of 475 pb−1. The electroweak decays of excited electrons e∗→eγ, e∗→eZ and e∗→νW with subsequent hadronic or leptonic decays of the W and Z bosons are considered. No evidence for excited electron production is found. Mass dependent exclusion limits on e∗ production cross sections and on the ratio f/Λ of the coupling to the compositeness scale are derived within gauge mediated models. These limits extend the excluded region compared to previous excited electron searches. The e∗ production via contact interactions is also addressed for the first time in ep collisions.Physics Letters B 09/2013; 666(2):131139. DOI:10.1016/j.physletb.2008.07.014 · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A search for scalar and vector leptoquarks coupling to first generation fermions is performed using the e+p and e−p scattering data collected by the H1 experiment between 1994 and 2000. The data correspond to a total integrated luminosity of 117 pb−1. No evidence for the direct or indirect production of such particles is found in data samples with a large transverse momentum final state electron or with large missing transverse momentum. Constraints on leptoquark models are established. For leptoquark couplings of electromagnetic strength, leptoquarks with masses up to 275–325 GeV are ruled out at 95% confidence level. These limits improve and supercede earlier H1 limits based on subsamples of the data used here.Physics Letters B 09/2013; 629(1):919. DOI:10.1016/j.physletb.2005.09.048 · 6.02 Impact Factor 
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ABSTRACT: The inclusive photoproduction of D ∗ mesons and of D ∗tagged dijets is investigated with the H1 detector at the ep collider HERA. The kinematic region covers small photon virtualities Q 2<2 GeV2 and photon–proton centreofmass energies of 100<W γp <285 GeV. Inclusive D ∗ meson differential cross sections are measured for central rapidities η(D ∗)<1.5 and transverse momenta p T (D ∗)>1.8 GeV. The heavy quark production process is further investigated in events with at least two jets with transverse momentum p T (jet)>3.5 GeV each, one containing the D ∗ meson. Differential cross sections for D ∗tagged dijet production and for correlations between the jets are measured in the range η(D ∗)<1.5 and p T (D ∗)>2.1 GeV. The results are compared with predictions from Monte Carlo simulations and nexttoleading order perturbative QCD calculations.European Physical Journal C 05/2012; 72(5). DOI:10.1140/epjc/s1005201219950 · 5.44 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The cross section of diffractive deepinelastic scattering ep→eXp is measured, where the system X contains at least two jets and the leading final state proton is detected in the H1 Forward Proton Spectrometer. The measurement is performed for fractional proton longitudinal momentum loss x ℙ<0.1 and covers the range 0.1<t<0.7 GeV2 in squared fourmomentum transfer at the proton vertex and 4<Q 2<110 GeV2 in photon virtuality. The differential cross sections extrapolated to t<1 GeV2 are in agreement with nexttoleading order QCD predictions based on diffractive parton distribution functions extracted from measurements of inclusive and dijet cross sections in diffractive deepinelastic scattering. The data are also compared with leading order Monte Carlo models.European Physical Journal C 04/2012; 72(4). DOI:10.1140/epjc/s1005201219709 · 5.44 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A search for first generation scalar and vector leptoquarks produced in ep collisions is performed by the H1 Collaboration at HERA. The full H1 data sample is used in the analysis, corresponding to an integrated luminosity 446 pb^1. No evidence for the production of leptoquarks is observed in final states with a large transverse momentum electron or with large missing transverse momentum, and constraints on leptoquark models are derived. For leptoquark couplings of electromagnetic strength lambda=0.3, first generation leptoquarks with masses up to 800 GeV are excluded at 95% confidence level.Physics Letters B 07/2011; 704:388396. DOI:10.1016/j.physletb.2011.09.017 · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: First measurements are presented of the diffractive cross section $\sigma_{ep \rightarrow eXY}$ at centreofmass energies $\sqrt{s}$ of 225 and 252 GeV, together with a precise new measurement at $\sqrt{s}$ of 319 GeV, using data taken with the H1 detector in the years 2006 and 2007. Together with previous H1 data at $\sqrt{s}$ of 301 GeV, the measurements are used to extract the diffractive longitudinal structure function F_L^D in the range of photon virtualities 4.0 <= Q^2 <= 44.0 GeV^2 and fractional proton longitudinal momentum loss 5 10^{4} <= x_{IP} <= 3 10^{3}. The measured F_L^D is compared with leading twist predictions based on diffractive parton densities extracted in NLO QCD fits to previous measurements of diffractive DeepInelastic Scattering and with a model which additionally includes a higher twist contribution derived from a colour dipole approach. The ratio of the diffractive cross section induced by longitudinally polarised photons to that for transversely polarised photons is extracted and compared with the analogous quantity for inclusive DeepInelastic Scattering.European Physical Journal C 07/2011; 71(12). DOI:10.1140/epjc/s1005201118366 · 5.44 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A search for second and third generation scalar and vector leptoquarks produced in ep collisions via the lepton flavour violating processes ep to muX and ep to tauX is performed by the H1 Collaboration at HERA. The full H1 ep data sample taken at a centreofmass energy of 319 GeV is used for the analysis, corresponding to an integrated luminosity of 411 pb^1. No evidence for the production of such leptoquarks is observed in the H1 data. Leptoquarks produced in ep collisions with a coupling strength of lambda=0.3 and decaying with the same coupling strength to a muonquark pair or a tauquark pair are excluded at 95% confidence level up to leptoquark masses of 712 GeV and 479 GeV, respectively.Physics Letters B 06/2011; 701:2030. DOI:10.1016/j.physletb.2011.05.023 · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The cross section for the diffractive deepinelastic scattering process ep→eXp is measured, with the leading final state proton detected in the H1 Forward Proton Spectrometer. The data sample covers the range x ℙt2 in squared fourmomentum transfer at the proton vertex and 4Q 22 in photon virtuality. The cross section is measured fourfold differentially in t,x ℙ,Q 2 and β=x/x ℙ, where x is the Bjorken scaling variable. The t and x ℙ dependences are interpreted in terms of an effective pomeron trajectory and a subleading exchange. The data are compared with perturbative QCD predictions at nexttoleading order based on diffractive parton distribution functions previously extracted from complementary measurements of inclusive diffractive deepinelastic scattering. The ratio of the diffractive to the inclusive ep cross section is studied as a function of Q 2,β and x ℙ.European Physical Journal C 03/2011; 71:1578. DOI:10.1140/epjc/s1005201115785 · 5.44 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A search for squarks in Rparity violating supersymmetry is performed in e ± p collisions at HERA using the H1 detector. The full data sample taken at a centreofmass 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 Rparity 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 downtype squarks further excluded up to masses of 290GeV.European Physical Journal C 03/2011; 71(3):116. DOI:10.1140/epjc/s100520111572y · 5.44 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: 31 pages, 11 figures, 1 table  Subm. to Eur. Phys. J. C  [Show abstract] [Hide abstract]
ABSTRACT: A search for second and third generation scalar and vector leptoquarks produced in ep collisions via the lepton flavour violating processes ep > mu X and ep > tau X is performed by the H1 experiment at HERA. The full data sample taken at a centreofmass energy sqrt{s} = 319 GeV is used for the analysis, corresponding to an integrated luminosity of 245 pb^1 of e^+ p and 166 pb^1 of e^ p collision data. No evidence for the production of such leptoquarks is observed in the H1 data. Leptoquarks produced in e^+ p collisions with a coupling strength of lambda=0.3 and decaying with the same coupling strength to a muonquark pair or a tauquark pair are excluded at 95% confidence level up to leptoquark masses of 712 GeV and 479 GeV, respectively.  [Show abstract] [Hide abstract]
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 fourmomentum 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 01/2011; 71(3):150. DOI:10.1140/epjc/s1005201115794 · 5.44 Impact Factor 
Article: Measurement of the Diffractive DeepInelastic Scattering Cross Section with a Leading Proton at HERA
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ABSTRACT: The cross section for the diffractive deepinelastic scattering process ep > e X p is measured, with the leading final state proton detected in the H1 Forward Proton Spectrometer. The data sample covers the range x_pom<0.1 in fractional proton longitudinal momentum loss, 0.1 < t < 0.7 GeV^2 in squared fourmomentum transfer at the proton vertex and 4 < Q^2 < 700 GeV^2 in photon virtuality. The cross section is measured fourfold differentially in t, x_pom, Q^2 and beta=x/x_pom, where x is the Bjorken scaling variable. The t and x_pom dependences are interpreted in terms of an effective pomeron trajectory and a subleading exchange. The data are compared to perturbative QCD predictions at nexttoleading order based on diffractive parton distribution functions previously extracted from complementary measurements of inclusive diffractive deepinelastic scattering. The ratio of the diffractive to the inclusive ep cross section is studied as a function of Q^2, beta and x_pom.  [Show abstract] [Hide abstract]
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 08/2010; 71(1):121. DOI:10.1140/epjc/s100520101509x · 5.44 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Measurements are presented of single and doubledifferential dijet cross sections in diffractive photoproduction based on a data sample with an integrated luminosity of 47 pb^1. The events are of the type ep > eXY, where the hadronic system X contains at least two jets and is separated by a large rapidity gap from the system Y, which consists of a leading proton or lowmass proton excitation. The dijet cross sections are compared with QCD calculations at nexttoleading order and with a Monte Carlo model based on leading order matrix elements with parton showers. The measured cross sections are smaller than those obtained from the nexttoleading order calculations by a factor of about 0.6. This suppression factor has no significant dependence on the fraction x_gamma of the photon fourmomentum entering the hard subprocess. Ratios of the diffractive to the inclusive dijet cross sections are measured for the first time and are compared with Monte Carlo models.  [Show abstract] [Hide abstract]
ABSTRACT: The production of jets is studied in deepinelastic e+p scattering at low negative four momentum transfer squared 5<Q^2<100 GeV^2 and at inelasticity 0.2<y<0.7 using data recorded by the H1 detector at HERA in the years 1999 and 2000, corresponding to an integrated luminosity of 43.5 pb^1. Inclusive jet, 2jet and 3jet cross sections as well as the ratio of 3jet to 2jet cross sections are measured as a function of Q^2 and jet transverse momentum. The 2jet cross section is also measured as a function of the proton momentum fraction xi. The measurements are well described by perturbative quantum chromodynamics at nexttoleading order corrected for hadronisation effects and are subsequently used to extract the strong coupling alpha_s.European Physical Journal C 05/2010; 67:124. DOI:10.1140/epjc/s100520101282x · 5.44 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Diffractive electroproduction of rho and phi 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 rho and 2000 phi events are analysed in the kinematic range of squared photon virtuality 2.5 < Q^2 < 60 GeV^2, photonproton centre of mass energy 35 < W < 180 GeV and squared fourmomentum transfer to the proton t < 3 GeV^2. 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\bar{q} dipoles, for Q^2 larger than 10 to 20 GeV^2. They support flavour independence of the diffractive exchange, expressed in terms of the scaling variable (Q^2 + M_V^2)/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.Journal of High Energy Physics 05/2010; 1005:032. DOI:10.1007/JHEP05(2010)032 · 6.22 Impact Factor  [Show abstract] [Hide abstract]
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 deepinelastic positronproton scattering at HERA. The data were taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 122 pb^{1}. The semiinclusive cross section is measured in the phase space defined by the photon virtuality 6 < Q^2 < 100 GeV^2, Bjorken scaling variable 1.5x10^{4} < x < 3x10^{2}, longitudinal momentum fraction 0.32 < x_L < 0.95 and neutron transverse momentum p_T < 0.2 GeV. The leading neutron structure function, F_2^{LN(3)}(Q^2,x,x_L), and the fraction of deepinelastic 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 01/2010; 68:381399. DOI:10.1140/epjc/s1005201013694 · 5.44 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The production of jets is studied in deepinelastic ep scattering at large negative four momentum transfer squared 150<Q^2<15000 GeV^2 using HERA data taken in 19992007, corresponding to an integrated luminosity of 395 pb^1. Inclusive jet, 2jet and 3jet cross sections, normalised to the neutral current deepinelastic 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 nexttoleading order corrected for hadronisation effects. The strong coupling as determined from these measurements is alpha_s(M_Z) = 0.1168 +/0.0007 (exp.) +0.0046/0.0030 (th.) +/0.0016(pdf).European Physical Journal C 01/2010; 65:363383. DOI:10.1140/epjc/s1005200912087 · 5.44 Impact Factor
Publication Stats
1k  Citations  
487.90  Total Impact Points  
Top Journals
Institutions

2003–2013

University of Hamburg
 Institut für Experimentalphysik
Hamburg, Hamburg, Germany


2007–2012

Joint Institute for Nuclear Research
 Bogoliubov Laboratory of Theoretical Physics
Dubno, Moskovskaya, Russia


2010

University of Antwerp
Antwerpen, Flemish, Belgium


2005

University of Birmingham
 School of Physics and Astronomy
Birmingham, ENG, United Kingdom
