5,995 research outputs found

    Detection of new states using forward proton tagging at the LHC

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    This talk summarises the ongoing proposals to upgrade the ATLAS and CMS detectors by the installation of forward silicon detector systems close to the beam line at distances of approximately 220 m and 420 m from the respective Interaction Points. The physics motivation is outlined, with emphasis on detection of Higgs and Supersymmetric states, and some of the aspects of the apparatus and its performance are briefly described.Comment: For ICHEP XXXIV Conference Proceedings. 4 pages. v2 has updated refs and minor corrections. v3 has cosmetic layout change

    The virtual photon structure at HERA

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    An overview is given of the ongoing measurement at HERA of the parton structure of the photon, as a function of its virtuality. Preliminary ZEUS results show disagreement with an NLO QCD calculation.Comment: To appear in Proc. International Conference on the Structure and Interactions of the Photon, Frascati, April 200

    Prompt photon, Drell-Yan and Bethe-Heitler processes in hard photoproduction

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    We present prospects and requirements for the study at HERA of hard photon processes which generate high pTp_T photons in the final state, and processes which generate Drell-Yan lepton pairs.Comment: 6 pages, 3 embedded figures. To appear in the proceedings of the workshop "Future physics at HERA

    Inclusive Jets and alpha_s at HERA

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    A brief survey is given of recent HERA results in jet production and prompt photon production, together with the evaluation of the QCD coupling constant alpha_s.Comment: To appear in Proc. International Conference on the Structure and Interactions of the Photon, Frascati, April 200

    Resonance Contributions to η\eta Photoproduction on Protons Found Using Dispersion Relations and an Isobar Model

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    The contributions of the resonances D13(1520)D_{13}(1520), S11(1535)S_{11}(1535), S11(1650)S_{11}(1650), D15(1675)D_{15}(1675), F15(1680)F_{15}(1680), D13(1700)D_{13}(1700), P11(1710)P_{11}(1710), P13(1720)P_{13}(1720) to γp→ηp\gamma p\to \eta p are found from the data on cross sections, beam and target asymmetries using two approaches: fixed-t dispersion relations and an isobar model. Utilization of the two approaches and comparison of the results obtained with different parametrizations of the resonance contributions allowed us to make conclusions about the model-dependence of these contributions. We conclude that the results for the contributions of the resonances D13(1520)D_{13}(1520), S11(1535)S_{11}(1535), F15(1680)F_{15}(1680) to corresponding multipole amplitudes are stable. With this the results for D13(1520)D_{13}(1520) and F15(1680)F_{15}(1680), combined with their PDG photoexcitation helicity amplitudes, allowed us to find the branching ratios Br(D13(1520)→ηN)=0.05±0.02Br (D_{13}(1520)\to \eta N)=0.05\pm 0.02%, Br(F15(1680)→ηN)=0.16±0.04Br (F_{15}(1680)\to \eta N)=0.16\pm0.04% which have significantly better accuracy than the PDG data. The total Breit-Wigner width of the S11(1535)S_{11}(1535) is model-dependent, we have obtained Γ(S11(1520))=142MeV\Gamma (S_{11}(1520))=142 MeV and 195MeV195 MeV using dispersion relations and the isobar model, respectively. The results for the S11(1650)S_{11}(1650), D15(1675)D_{15}(1675), P11(1710)P_{11}(1710), P13(1720)P_{13}(1720) are model dependent, only the signs and orders of magnitude of their contributions to multipole amplitudes are determined. The results for the D13(1700)D_{13}(1700) are strongly model-dependent.Comment: 26 pages, 6 figure

    Functionally dissociating aspects of event memory: the effects of combined perirhinal and postrhinal cortex lesions on object and place memory in the rat.

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    Reciprocal interactions between the hippocampus and the perirhinal and parahippocampal cortices form core components of a proposed temporal lobe memory system. For this reason, the involvement of the hippocampus in event memory is thought to depend on its connections with these cortical areas. Contrary to these predictions, we found that NMDA-induced lesions of the putative rat homologs of these cortical areas (perirhinal plus postrhinal cortices) did not impair performance on two allocentric spatial tasks highly sensitive to hippocampal dysfunction. Remarkably, for one of the tasks there was evidence of a facilitation of performance. The same cortical lesions did, however, disrupt spontaneous object recognition and object discrimination reversal learning but spared initial acquisition of the discrimination. This pattern of results reveals important dissociations between different aspects of memory within the temporal lobe. Furthermore, it shows that the perirhinal-postrhinal cortex is not a necessary route for spatial information reaching the hippocampus and that object familiarity-novelty detection depends on different neural substrates than do other aspects of event memory

    Fornix lesions can facilitate acquisition of the transverse patterning task: a challenge for configural theories of hippocampal function.

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    Configural theories of hippocampal function predict that hippocampal dysfunction should impair acquisition of the transverse patterning task, which involves the concurrent solution of three discrimination problems: A+ versus B-; B+ versus C-; and C+ versus A-. The present study tested this prediction in rats using computer-graphic stimuli presented on a touchscreen. Experiment 1 assessed the effects of fornix lesions when the three problems were introduced sequentially (phase 1: A+ vs B-; phase 2: A+ vs B-, B+ vs C-; phase 3: A+ vs B-, B+ vs C-, C+ vs A-). Fornix lesions significantly facilitated acquisition of the complete transverse patterning task (phase 3) but had no effect on the number of sessions or errors required to attain criterion during phase 1 or phase 2. In experiment 2, in which all three problems were presented concurrently from the outset of training, fornix-lesioned animals outperformed control animals during the seventh block of acquisition trials and were not impaired during any stage of acquisition. Importantly, these same animals were significantly impaired on two allocentric spatial tasks: T-maze alternation (experiments 1 and 2) and the Morris Swim Task (experiment 1). These results contradict the predictions of configural theories of hippocampal function and cast doubt on the popular notion that spatial learning is a special case of configural learning
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