134 research outputs found

    THERMAL MODELLING IN THE EASTERN OTWAY BASIN

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    Vitrinite reflectance data across the Otway Ranges yield a thermal maturity map that indicates the presence of a broad NE-SW trending anticline with strong vergence to the southeast. Surface Rv max values for the central part of the ranges are &gt;1.5 whilst those on both limbs decrease to Apatite fission track analysis of seven Eumeralla (Lower Cretaceous) samples from the coast around Wye River yields an AFTA age of 90±5 Ma, consistent with similar cooling ages measured around most of the SE Australia margin. Modelling of the data is consistent with a stratigraphic age of -100 Ma, rapid heating to −80°C for −5 Ma followed by cooling from 95–80 Ma and further cooling in the Miocene.Geologically the very large asymmetric anticline can be explained by inversion of a thick rift sequence along a major, listric northwest-dipping fault, perhaps soling at mid-crustal levels. This is consistent with structures observed offshore in the Torquay Embayment and is being tested by the AGSO deep seismic profile BMR 920T1. Observed gravity highs in the Otway Ranges may be associated with inverted high density sediments. Fission track analysis indicates that the major cooling was at −90 Ma, which is therefore likely to be the time of inversion. However, this implies compression during continental breakup, the mechanisms of which are not fully understood.</jats:p

    Three- and four-jet final states in photoproduction at HERA

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    Three- and four-jet final states have been measured in photoproduction at HERA using the ZEUS detector with an integrated luminosity of 121   pb -1. The results are presented for jets with transverse energy E Tjet > 6   GeV and pseudorapidity | η jet | < 2.4, in the kinematic region given by the virtuality of the photon Q 2 < 1   GeV 2 and the inelasticity 0.2 ≤ y ≤ 0.85 and in two mass regions defined as 25 ≤ M n j < 50   GeV and M n j ≥ 50   GeV, where M n j is the invariant mass of the n-jet system. The four-jet photoproduction cross section has been measured for the first time and represents the highest-order process studied at HERA. Both the three- and four-jet cross sections have been compared with leading-logarithmic parton-shower Monte Carlo models, with and without multi-parton interactions. The three-jet cross sections have been compared to an O (α α s2) perturbative QCD calculation. © 2007 Elsevier B.V. All rights reserved

    Measurement of high-Q (2) charged current deep inelastic scattering cross sections with a longitudinally polarised positron beam at HERA

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    Measurements of the cross sections for charged current deep inelastic scattering in e+p collisions with a longitudinally polarised positron beam are presented. The measurements are based on a data sample with an integrated luminosity of 132 pb-1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is presented at positive and negative values of the longitudinal polarisation of the positron beams. The single-differential cross-sections dσ/dQ2, dσ/dx and dσ/dy are presented for Q2>200 GeV2. The reduced cross-section σ̃ is presented in the kinematic range 200&lt;Q2&lt;60000 GeV2 and 0.006&lt;x&lt;0.562. The measurements agree well with the predictions of the Standard Model. The results are used to determine a lower limit on the mass of a hypothetical right-handed W boson. © 2010 The Author(s)

    Measurement of (anti)deuteron and (anti)proton production in DIS at HERA

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    The first observation of (anti)deuterons in deep inelastic scattering at HERA has been made with the ZEUS detector at a centre-of-mass energy of 300-318 GeV using an integrated luminosity of 120 pb-1. The measurement was performed in the central rapidity region for transverse momentum per unit of mass in the range 0.3 < pT / M < 0.7. The particle rates have been extracted and interpreted in terms of the coalescence model. The (anti)deuteron production yield is smaller than the (anti)proton yield by approximately three orders of magnitude, consistent with the world measurements. © 2007 Elsevier B.V. All rights reserved

    Inclusive-Jet Photoproduction at HERA and Determination of αs\alpha_{s}

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    Inclusive-jet cross sections have been measured in the reaction ep→e+jet+X for photon virtuality Q 2<1 GeV 2 and γp centre-of-mass energies in the region 14217 GeV and -1< jet<2.5. In addition, measurements of double-differential inclusive-jet cross sections are presented as functions of ETjet in different regions of jet. Next-to-leading-order QCD calculations give a good description of the measurements, except for jets with low ETjet and high jet. The influence of non-perturbative effects not related to hadronisation was studied. Measurements of the ratios of cross sections using different jet algorithms are also presented; the measured ratios are well described by calculations including up to O(αs2) terms. Values of α s(M Z) were extracted from the measurements and the energy-scale dependence of the coupling was determined. The value of α s(M Z) extracted from the measurements based on the k T jet algorithm is αs(MZ)=0.1206-0.0022+0.0023(exp.)-0.0035+0.0042(th.); the results from the anti-k T and SIScone algorithms are compatible with this value and have a similar precision. © 2012 Elsevier B.V

    Combined inclusive diffractive cross sections measured with forward proton spectrometers in deep inelastic ep scattering at HERA

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    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 √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 GeV 2 in photon virtuality, 0.00035 < xP < 0.09 in proton fractional momentum loss, 0.09 <{pipe}t{pipe}< 0.55 GeV 2 in squared four-momentum transfer at the proton vertex and 0.0018 < β <0.816 in β=x/xP, where x is the Bjorken scaling variable. © 2012 The Author(s).0H1 and ZEUS CollaborationsSCOPUS: ar.jinfo:eu-repo/semantics/publishe

    Exclusive electroproduction of two pions at HERA

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    The exclusive electroproduction of two pions in the mass range 0.4&#60;M &#960;&#960;&#60;2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb&lt;sup&gt;-1&lt;/sup&gt;. The analysis was carried out in the kinematic range of 2&#60;Q &lt;sup&gt;2&lt;/sup&gt;&#60;80 GeV&lt;sup&gt;2&lt;/sup&gt;, 32&#60;W&#60;180 GeV and |t|&#60;0.6 GeV&lt;sup&gt;2&lt;/sup&gt;, where Q&lt;sup&gt;2&lt;/sup&gt; is the photon virtuality, W is the photon-proton centre-of-mass energy and &lt;i&gt;t&lt;/i&gt; is the squared four-momentum transfer at the proton vertex. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, |F(M &#960;&#960; )|, assuming that the studied mass range includes the contributions of the ρ, ρ′ and ρ′′ vector-meson states. The masses and widths of the resonances were obtained and the Q&lt;sup&gt;2&lt;/sup&gt; dependence of the cross-section ratios &#948;(ρ′→&#960;&#960;)/&#948;(ρ) and &#948;(ρ′′&#8594;)/&#948;(ρ) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in e&lt;sup&gt;+&lt;/sup&gt; e&lt;sup&gt;−&lt;/sup&gt;→&#960;&lt;sup&gt;+&lt;/sup&gt; &#960;&lt;sup&gt;−&lt;/sup&gt;

    Inclusive dijet cross sections in neutral current deep inelastic scattering at HERA

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    Single- and double-differential inclusive dijet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector using an integrated luminosity of 374 pb&lt;sup&gt;−1&lt;/sup&gt;. The measurement was performed at large values of the photon virtuality, Q 2, between 125 and 20 000 GeV&lt;sup&gt;2&lt;/sup&gt;. The jets were reconstructed with the k&lt;sub&gt;T&lt;/sub&gt; cluster algorithm in the Breit reference frame and selected by requiring their transverse energies in the Breit frame, E&lt;sup&gt;jet&lt;/sup&gt;&lt;sub&gt;TB&lt;/sub&gt;, to be larger than 8 GeV. In addition, the invariant mass of the dijet system, M&lt;sub&gt;jj&lt;/sub&gt;, was required to be greater than 20 GeV. The cross sections are described by the predictions of next-to-leading-order QCD
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