| 1. |
- Aaron, F. D., et al.
(author)
-
A precision measurement of the inclusive ep scattering cross section at HERA
- 2009
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 64:4, s. 561-587
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Journal article (peer-reviewed)abstract
- A measurement of the inclusive deep inelastic neutral current e(+) p scattering cross section is reported in the region of four-momentum transfer squared, 12GeV(2) <= Q(2) <= 150 GeV2, and Bjorken x, 2 x 10(-4) <= x <= 0.1. The results are based on data collected by the H1 Collaboration at the ep collider HERA at positron and proton beam energies of E-e = 27.6 GeV and E-p = 920 GeV, respectively. The data are combined with previously published data, taken at E-p = 820 GeV. The accuracy of the combined measurement is typically in the range of 1.3-2%. A QCD analysis at next-to-leading order is performed to determine the parton distributions in the proton based on H1 data.
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| 2. |
- Aaron, F. D., et al.
(author)
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Measurement of D*(+/-) meson production and determination of F-2(c(c)over-bar) at low Q(2) in deep-inelastic scattering at HERA
- 2011
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:10
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Journal article (peer-reviewed)abstract
- Inclusive production of D* mesons in deep-inelastic ep scattering at HERA is studied in the range 5 < Q(2) < 100 GeV2 of the photon virtuality and 0.02 < y < 0.7 of the inelasticity of the scattering process. The observed phase space for the D* meson is (pT) (D*) > 1.25 GeV and |eta( D*)| < 1.8. The data sample corresponds to an integrated luminosity of 348 pb(-1) collected with the H1 detector. Single and double differential cross sections are measured and the charm contribution F-2(c (c) over bar) to the proton structure function F-2 is determined. The results are compared to perturbative QCD predictions at next-to-leading order implementing different schemes for the charm mass treatment and with Monte Carlo models based on leading order matrix elements with parton showers.
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| 3. |
- Aaron, F. D., et al.
(author)
-
Measurement of the inclusive ep scattering cross section at low Q (2) and x at HERA
- 2009
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 63:4, s. 625-678
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Journal article (peer-reviewed)abstract
- A measurement of the inclusive ep scattering cross section is presented in the region of low momentum transfers, 0.2 GeV2 a parts per thousand currency signQ (2)a parts per thousand currency sign12 GeV2, and low Bjorken x, 5a <...10(-6)a parts per thousand currency signxa parts per thousand currency sign0.02. 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.
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| 4. |
- Aaron, F. D., et al.
(author)
-
Measurement of the proton structure function F-L(x, Q(2)) at low x
- 2008
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In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 665:4, s. 139-146
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Journal article (peer-reviewed)abstract
- A first measurement is reported of the longitudinal proton structure function FL(X, Q(2)) at the ep collider HERA. It is based on inclusive deep inelastic e(+)p scattering cross section measurements with a positron beam energy of 27.5 GeV and proton beam energies of 920, 575 and 460 GeV. Employing the energy dependence of the cross section, FL is measured in a range of squared four-momentum transfers 12 <= Q2 <=, 90 GeV2 and low Bjorken x 0.00024 <= x <= 0.0036. The F-L values agree with higher order QCD calculations based on parton densities obtained using cross section data previously measured at HERA. (C) 2008 Elsevier B.V. All rights reserved.
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| 5. |
- Aaron, F. D., et al.
(author)
-
Search for contact interactions in e(+/-)p collisions at HERA H1 Collaboration
- 2011
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In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 705:1-2, s. 52-58
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Journal article (peer-reviewed)abstract
- A search for physics beyond the Standard Model in neutral current deep inelastic scattering at high negative four-momentum transfer squared Q(2) is performed in e(+/-)p collisions at HERA. The differential cross section d sigma/dQ(2), measured using the full H1 data sample corresponding to an integrated luminosity of 446 pb(-1), is compared to the Standard Model prediction. No significant deviation is observed. Limits on various models predicting new phenomena at high Q(2) are derived. For general four-fermion eeqq contact interaction models, lower limits on the compositeness scale A are set in the range 3.6 TeV to 7.2 TeV. Leptoquarks with masses M-LQ and couplings lambda are constrained to M-LQ/lambda > 0.41-1.86 TeV and limits on squarks in R-parity violating supersymmetric models are derived. A lower limit on the gravitational scale in 4 + n dimensions of M-S > 0.9 TeV is established for low-scale quantum gravity effects in models with large extra dimensions. For the light quark radius an upper bound of R-q < 0.65 . 10(-18) m is determined. (C) 2011 Elsevier B.V. All rights reserved.
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| 6. |
- Aaron, F. D., et al.
(author)
-
Search for squarks in R-parity violating supersymmetry in ep collisions at HERA
- 2011
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:3
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Journal article (peer-reviewed)abstract
- A search for squarks in R-parity violating super-symmetry is performed in e(+/-)p collisions at HERA using the H1 detector. The full data sample taken at a centre-of-mass energy root s = 319 GeV is used for the analysis, corresponding to an integrated luminosity of 255 pb(-1) of e(+)p and 183 pb(-1) of e(-)p collision data. The resonant production of squarks via a Yukawa coupling. lambda' 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 lambda' are obtained in the framework of the Minimal Supersymmetric Standard Model and in the Minimal Super-gravity Model. In the considered part of the parameter space, for a Yukawa coupling of electromagnetic strength lambda' = 0.3, squarks of all flavours are excluded up to masses of 275 GeV at 95% confidence level, with down-type squarks further excluded up to masses of 290 GeV.
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| 7. |
- Aaron, F. D., et al.
(author)
-
Strangeness production at low Q(2) in deep-inelastic ep scattering at HERA
- 2009
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 61:2, s. 185-205
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Journal article (peer-reviewed)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) s and Lambda((Lambda) over bar) production cross sections and their ratios are determined. K-s(0) s production is compared to the production of charged particles in the same region of phase space. The Lambda-(Lambda) over bar asymmetry is also measured and found to be consistent with zero. Predictions of leading order Monte Carlo programs are compared to the data.
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| 8. |
- Aaroe, Lene, et al.
(author)
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The journalistic preference for extreme exemplars: educational socialization, psychological biases, or editorial policy?
- 2024
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In: JOURNAL OF COMMUNICATION. - 0021-9916 .- 1460-2466. ; 74:1, s. 48-62
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Journal article (peer-reviewed)abstract
- Exemplars are central in news reporting. However, extreme negative exemplars can bias citizens' factual perceptions and attributions of political responsibility. Nonetheless, our knowledge of the factors shaping journalistic preferences for including exemplars in news stories is limited. We investigate the extent to which educational socialization, psychological biases, and editorial policy shape journalistic preferences for extreme negative exemplars. We field large-scale survey experiments to a population sample of journalism students, a nationally representative sample of citizens, and a representative sample of "young people" and obtain evaluations of news value, newsworthiness, and behavioral measures of the actual write-up of news articles. We find significant support for the role of editorial policy and limited support for the role of educational socialization and psychological biases. In a time where economic pressures and the proliferation of digital media potentially lead editors to prioritize clickbait, these findings suggest that structural biases in news coverage may be aggravated.
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| 9. |
- Aaron, F. D., et al.
(author)
-
Measurement of inclusive and dijet D* meson cross sections in photoproduction at HERA
- 2012
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 72:5
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Journal article (peer-reviewed)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 centre-of-mass energies of 100< W-gamma p < 285 GeV. Inclusive D* meson differential cross sections are measured for central rapidities vertical bar eta(D*)vertical bar < 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 vertical bar eta(D*)vertical bar < 1.5 and p(T) (D*) > 2.1 GeV. The results are compared with predictions from Monte Carlo simulations and next-to-leading order perturbative QCD calculations.
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| 10. |
- Aaron, F. D., et al.
(author)
-
Study of charm fragmentation into D (* +/-) mesons in deep-inelastic scattering at HERA
- 2009
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 59:3, s. 589-606
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Journal article (peer-reviewed)abstract
- The process of charm quark fragmentation is studied using D (* +/-) meson production in deep-inelastic scattering as measured by the H1 detector at HERA. The parameters of fragmentation functions are extracted for QCD models based on leading order matrix elements and DGLAP or CCFM evolution of partons together with string fragmentation and particle decays. Additionally, they are determined for a next-to-leading order QCD calculation in the fixed flavour number scheme using the independent fragmentation of charm quarks to D (* +/-) mesons. Two different regions of phase space are investigated defined by the presence or absence of a jet containing the D (* +/-) meson in the event. The fragmentation parameters extracted for the two phase space regions are found to be different.
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