Publications (145)329.9 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.  [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. 

Dataset: desy06110

Dataset: desy06110
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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, photonproton centre of mass energy 35 ≤ W ≤ 180 GeV and squared fourmomentum 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 \( q\overline q \) 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.  [Show abstract] [Hide abstract]
ABSTRACT: The production of jets is studied in deepinelastic e ± p scattering at large negative four momentum transfer squared 150<Q 2<15000 GeV2 using HERA data taken in 1999–2007, 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 \(\alpha_{s}(M_{Z})=0.1168\pm0.0007\,\mathrm{(exp.)}{}^{+0.0046}_{0.0030}\,\mathrm{(th.)}\pm 0.0016\) (PDF).  [Show abstract] [Hide abstract]
ABSTRACT: 120 pages, 48 figures, 57 tables 
Article: Measurement of the charm and beauty structure functions using the H1 vertex detector at HERA
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ABSTRACT: Inclusive charm and beauty cross sections are measured in ep and e+p neutral current collisions at HERA in the kinematic region of photon virtuality 5<Q^2<2000 GeV^2 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 189 pb^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. 

Article: Events with Isolated Leptons and Missing Transverse Momentum and Measurement of W Production at HERA
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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^\pm p data sample collected by the H1 experiment at HERA, corresponding to an integrated luminosity of 474 pb^{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 \pm 0.25 (stat.) \pm 0.14 (sys.) pb, in agreement with the Standard Model expectation. The data are also used to establish limits on the WW\gamma gauge couplings and for a measurement of the W boson polarisation.  [Show abstract] [Hide abstract]
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 340 pb−1 collected by the H1 experiment. Cross sections are measured for photons with transverse momentum and pseudorapidity in the range GeV and −1.0<η γ <2.4, respectively. Cross sections for events with an additional jet are measured as a function of the transverse energy and pseudorapidity of the jet, and as a function of the fractional momenta x γ and x p carried by the partons entering the hard scattering process. The correlation between the photon and the jet is also studied. The results are compared with QCD predictions based on the collinear and on the k T factorization approaches.  [Show abstract] [Hide abstract]
ABSTRACT: A first measurement is presented of the charge asymmetry in the hadronic final state from the hard interaction in deepinelastic ep neutral current scattering at HERA. The measurement is performed in the range of negative squared four momentum transfer 100 < Q2 < 8, 000 GeV2 . The difference between the event normalised distributions of the scaled momentum, xp, for positively and negatively charged particles, measured in the current region of the Breit frame, is studied together with its evolution as a function of Q. The results are compared to Monte Carlo models at the hadron and parton level.  [Show abstract] [Hide abstract]
ABSTRACT: The first measurement of diffractive scattering of quasireal photons with large momentum transfer gamma p > gamma Y, where Y is the proton dissociative system, is made using the H1 detector at HERA. The measurement is performed for initial photon virtualities Q^2 < 0.01 GeV^2. Cross sections are measured as a function of W, the incident photonproton entre of mass energy, and t, the square of the fourmomentum transferred at the proton vertex, in the range 175 < W < 247 GeV and 4<t<36 GeV^2. The W dependence is well described by a model based on perturbative QCD using a leading logarithmic approximation of the BFKL evolution. The measured t dependence is harder than that predicted by the model and those observed in exclusive vector meson production. 

Article: Deeply Virtual Compton Scattering and its Beam Charge Asymmetry in e^pm p Collisions at HERA
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ABSTRACT: A measurement of elastic deeply virtual Compton scattering gamma* p > gamma p using e^+ p and e^ p collision data recorded with the H1 detector at HERA is presented. The analysed data sample corresponds to an integrated luminosity of 306 pb^1, almost equally shared between both beam charges. The cross section is measured as a function of the virtuality Q^2 of the exchanged photon and the centreofmass energy W of the gamma* p system in the kinematic domain 6.5 < Q^2 < 80 GeV^2, 30 < W < 140 GeV and t < 1 GeV^2, where t denotes the squared momentum transfer at the proton vertex. The cross section is determined differentially in t for different Q^2 and W values and exponential tslope parameters are derived. Using e^+ p and e^ p data samples, a beam charge asymmetry is extracted for the first time in the low Bjorken x kinematic domain. The observed asymmetry is attributed to the interference between BetheHeitler and deeply virtual Compton scattering processes. Experimental results are discussed in the context of two different models, one based on generalised parton distributions and one based on the dipole approach. 

Article: Measurement of the charm and beauty structure functions using the H1 vertex detector at HERA
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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.  [Show abstract] [Hide abstract]
ABSTRACT: A first measurement is presented of the charge asymmetry in the hadronic final state from the hard interaction in deepinelastic ep neutral current scattering at HERA. The measurement is performed in the range of negative squared four momentum transfer 100Q28000 GeV2. The difference between the event normalised distributions of the scaled momentum, xp, for positively and negatively charged particles, measured in the current region of the Breit frame, is studied together with its evolution as a function of Q. The results are compared to Monte Carlo models at the hadron and parton levels.
Publication Stats
1k  Citations  
329.90  Total Impact Points  
Top Journals
Institutions

20082013

Deutsches ElektronenSynchrotron
Hamburg, Hamburg, Germany


20062013

Institute for Theoretical and Experimental Physics
 Laboratory of Theoretical Physics
Moskva, Moscow, Russia


20062009

University of Hamburg
 Institut für Experimentalphysik
Hamburg, Hamburg, Germany


2007

University of Twente
Enschede, Overijssel, Netherlands 
University of Birmingham
 School of Physics and Astronomy
Birmingham, England, United Kingdom
