5,995 research outputs found
Detection of new states using forward proton tagging at the LHC
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
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
We present prospects and requirements for the study at HERA of hard photon
processes which generate high 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
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 Photoproduction on Protons Found Using Dispersion Relations and an Isobar Model
The contributions of the resonances , ,
, , , , ,
to 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 , , to corresponding
multipole amplitudes are stable. With this the results for and
, combined with their PDG photoexcitation helicity amplitudes,
allowed us to find the branching ratios , which have significantly
better accuracy than the PDG data. The total Breit-Wigner width of the
is model-dependent, we have obtained and using dispersion relations and the isobar model,
respectively. The results for the , ,
, are model dependent, only the signs and orders
of magnitude of their contributions to multipole amplitudes are determined. The
results for the 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.
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.
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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