| 1. |
- Aaron, F. D., et al.
(författare)
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Combined inclusive diffractive cross sections measured with forward proton spectrometers in deep inelastic ep scattering at HERA
- 2012
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 72:10
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Tidskriftsartikel (refereegranskat)abstract
- A combination of the inclusive diffractive cross section measurements made by the H1 and ZEUS Collaborations at HERA is presented. The analysis uses samples of diffractive deep inelastic ep scattering data at a centre-of-mass energy root s = 318 GeV where leading protons are detected by dedicated spectrometers. Correlations of systematic uncertainties are taken into account, resulting in an improved precision of the cross section measurement which reaches 6 % for the most precise points. The combined data cover the range 2.5 < Q(2) < 200 GeV2 in photon virtuality, 0.00035 < x(P) < 0.09 in proton fractional momentum loss, 0.09 < vertical bar t vertical bar < 0.55 GeV2 in squared four-momentum transfer at the proton vertex and 0.0018 < beta < 0.816 in beta = x/x(P), where x is the Bjorken scaling variable.
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| 2. |
- Abramowicz, H., et al.
(författare)
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Combination and QCD analysis of charm production cross section measurements in deep-inelastic ep scattering at HERA
- 2013
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 73:2
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Tidskriftsartikel (refereegranskat)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(c (c) over bar)(red) for charm production are obtained in the kinematic range of photon virtuality 2.5 <= Q(2) <= 2000 GeV2 and Bjorken scaling variable 3 . 10(-5) <= x <= 5 . 10(-2). 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-+/- 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.
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| 3. |
- Aaron, F. D., et al.
(författare)
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Measurement of the inclusive e(+/-) p scattering cross section at high inelasticity y and of the structure function F-L
- 2011
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:3
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Tidskriftsartikel (refereegranskat)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 460 GeV. The kinematic range of the measurement covers low absolute four-momentum transfers squared, 1.5 GeV2 < Q(2) < 120 GeV2, 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 = 920 GeV and E-p = 820 GeV. The new measurements are used to test several phenomenological and QCD models applicable in this low Q(2) and low x kinematic domain.
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| 4. |
- Aaron, F. D., et al.
(författare)
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Inclusive deep inelastic scattering at high Q(2) with longitudinally polarised lepton beams at HERA
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :9
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Tidskriftsartikel (refereegranskat)abstract
- Inclusive e(+/-)p single and double differential cross sections for neutral and charged current deep inelastic scattering processes are measured with the H1 detector at HERA. The data were taken at a centre-of-mass energy of root s = 319 GeV with a total integrated luminosity of 333.7 pb(-1) shared between two lepton beam charges and two longitudinal lepton polarisation modes. The differential cross sections are measured in the range of negative four-momentum transfer squared, Q(2), between 60 and 50 000GeV(2), and Bjorken x between 0.0008 and 0.65. The measurements are combined with earlier published unpolarised H1 data to improve statistical precision and used to determine the structure function xF(3)(gamma Z). A measurement of the neutral current parity violating structure function F-2(gamma Z) is presented for the first time. The polarisation dependence of the charged current total cross section is also measured. The new measurements are well described by a next-to-leading order QCD fit based on all published H1 inclusive cross section data which are used to extract the parton distribution functions of the proton.
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| 5. |
- Aaron, F. D., et al.
(författare)
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Measurement of beauty photoproduction near threshold using di-electron events with the H1 detector at HERA
- 2012
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 72:10
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Tidskriftsartikel (refereegranskat)abstract
- The cross section for ep -> eb (b) over barX in photoproduction is measured with the H1 detector at the ep-collider HERA. The decay channel b (b) over bar -> eeX' is selected by identifying the semi-electronic decays of the b-quarks. The total production cross section is measured in the kinematic range given by the photon virtuality Q(2) <= 1 GeV2, the inelasticity 0.05 <= y <= 0.65 and the pseudorapidity of the b-quarks vertical bar eta(b)vertical bar, vertical bar eta((b) over bar)vertical bar <= 2. The differential production cross section is measured as a function of the average transverse momentum of the beauty quarks < P-T(b)> down to the threshold. The results are compared to next-to-leading-order QCD predictions.
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| 6. |
- Aaron, F. D., et al.
(författare)
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Determination of the integrated luminosity at HERA using elastic QED Compton events
- 2012
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 72:10
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Tidskriftsartikel (refereegranskat)abstract
- A measurement of the integrated luminosity at the ep collider HERA is presented, exploiting the elastic QED Compton process ep -> e gamma p. The electron and the photon are detected in the backward calorimeter of the H1 experiment. The integrated luminosity of the data recorded in 2003 to 2007 is determined with a precision of 2.3%. The measurement is found to be compatible with the corresponding result obtained using the Bethe-Heitler process.
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| 7. |
- Aaron, F. D., et al.
(författare)
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Inclusive measurement of diffractive deep-inelastic scattering at HERA
- 2012
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 72:7
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Tidskriftsartikel (refereegranskat)abstract
- The diffractive process ep -> eXY, where Y denotes a proton or its low mass excitation with M-Y < 1.6 GeV, is studied with the H1 experiment at HERA. The analysis is restricted to the phase space region of the photon virtuality 3 <= Q(2) <= 1600 GeV2, the square of the fourmomentum transfer at the proton vertex vertical bar t vertical bar < 1.0 GeV2 and the longitudinal momentum fraction of the incident proton carried by the colourless exchange x(P) < 0.05. Triple differential cross sections are measured as a function of x(P), Q(2) and beta = x/x(P) where x is the Bjorken scaling variable. These measurements are made after selecting diffractive events by demanding a large empty rapidity interval separating the final state hadronic systems X and Y. High statistics measurements covering the data taking periods 1999-2000 and 2004-2007 are combined with previously published results in order to provide a single set of diffractive cross sections from the H1 experiment using the large rapidity gap selection method. The combined data represent a factor between three and thirty increase in statistics with respect to the previously published results. The measurements are compared with predictions from NLO QCD calculations based on diffractive parton densities and from a dipole model. The proton vertex factorisation hypothesis is tested.
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| 8. |
- Alexa, C., et al.
(författare)
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Elastic and proton-dissociative photoproduction of J/psi mesons at HERA
- 2013
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 73:6
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Tidskriftsartikel (refereegranskat)abstract
- Cross sections for elastic and proton-dissociative photoproduction of J/psi mesons are measured with the H1 detector in positron-proton collisions at HERA. The data were collected at ep centre-of-mass energies root s approximate to 318 GeV and root s approximate to 225 GeV, corresponding to integrated luminosities of L = 130 pb(-1) and L = 10.8 pb(-1), respectively. The cross sections are measured as a function of the photon-proton centre-of-mass energy in the range 25 < W-gamma p < 110 GeV. Differential cross sections d sigma/dt, where t is the squared four-momentum transfer at the proton vertex, are measured in the range vertical bar t vertical bar < 1.2 GeV2 for the elastic process and vertical bar t vertical bar < 8 GeV2 for proton dissociation. The results are compared to other measurements. The W-gamma p and t-dependences are parametrised using phenomenological fits.
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| 9. |
- Alexa, C., et al.
(författare)
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Measurement of charged particle spectra in deep-inelastic ep scattering at HERA
- 2013
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 73:4
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Tidskriftsartikel (refereegranskat)abstract
- Charged particle production in deep-inelastic ep scattering is measured with the H1 detector at HERA. The kinematic range of the analysis covers low photon virtualities, 5 < Q(2) < 100 GeV2, and small values of Bjorken-x, 10(-4) < x < 10(-2). The analysis is performed in the hadronic centre-of-mass system. The charged particle densities are measured as a function of pseudorapidity (n(*)) and transverse momentum (p(T)(*)) in the range 0 < n(*) < 5 and 0 < p(T)(*) < 10 GeV in bins of x and Q(2). The data are compared to predictions from different Monte Carlo generators implementing various options for hadronisation and parton evolutions.
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| 10. |
- Ermolaev, G. A., et al.
(författare)
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Giant optical anisotropy in transition metal dichalcogenides for next-generation photonics
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Large optical anisotropy observed in a broad spectral range is of paramount importance for efficient light manipulation in countless devices. Although a giant anisotropy has been recently observed in the mid-infrared wavelength range, for visible and near-infrared spectral intervals, the problem remains acute with the highest reported birefringence values of 0.8 in BaTiS3 and h-BN crystals. This issue inspired an intensive search for giant optical anisotropy among natural and artificial materials. Here, we demonstrate that layered transition metal dichalcogenides (TMDCs) provide an answer to this quest owing to their fundamental differences between intralayer strong covalent bonding and weak interlayer van der Waals interaction. To do this, we made correlative far- and near-field characterizations validated by first-principle calculations that reveal a huge birefringence of 1.5 in the infrared and 3 in the visible light for MoS2. Our findings demonstrate that this remarkable anisotropy allows for tackling the diffraction limit enabling an avenue for on-chip next-generation photonics. Optical anisotropy in a broad spectral range is pivotal to efficient light manipulation. Here, the authors measure a birefringence of 1.5 in the infrared range and 3 in the visible light for MoS2.
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