124067127
PROGRESS REPORT ON THE 200-GeV ACCELERATOR OF THE NATIONAL ACCELERATOR LABORATORY.
121757543
Measurement of single spin asymmetry for direct photon production in pp collisions at 200 GeV/c
The single spin asymmetry for inclusive direct-photon production has been measured using a polarized proton beam of 200 GeV/c with an unpolarized proton target at −0.15 < xf < 0.15 and 2.5 < pt < 3.1 GeV/c at Fermilab. The data on the cross section for pp → γX at 2.5 < pt < 3.8 GeV/c are also provided. The measurement was done using lead-glass calorimeters and photon detectors which surrounded the fiducial area of the calorimeters. Background rejection has been done using these surrounding photon detectors. The cross section obtained is consistent with the results of previous measurements assuming a nuclear dependence of A1.0. The single spin asymmetry, AN, for the direct-photon production is consistent with zero within experimental uncertainty.
123662576
Observation of a likely example of the decay of a charmed particle produced in a high energy neutrino interaction
Abstract In a study of neutrino interactions occurring in nuclear emulsion, an event has been found that is most readily interpreted as the decay of a charmed particle with lifetime a few times 10 −13 s.
120981188
LARGE-ANGLE PION--PROTON ELASTIC SCATTERING AT HIGH ENERGIES.
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A POSSIBLE SPECTROMETER FOR ACCOMPLISHING A SECONDARY BEAM SURVEY AT NAL.
118121131
USE OF THE 3.5-MRAD BEAM FOR ELECTRONS.
110034857
The DELPHI small angle tile calorimeter
The small angle tile Calorimeter (STIC) provides calorimetric coverage in the very forward region for the DELPHI experiment at the CERN LEP collider. A veto system composed of two scintillator layers allows one to trigger on single photon events and provides e-/spl gamma/ separation. We present here some results of extensive measurements performed on part of the calorimeter and the veto system in the CERN test beams prior to installation and report on the performance achieved during the 1994 LEP run. >
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The small angle tile calorimeter in the DELPHI experiment
Abstract The Small angle TIle Calorimeter (STIC) provides calorimetric coverage in the very forward region of the DELPHI experiment at the CERN LEP collider. The structure of the calorimeters, built with a so-called “shashlik” technique, gives a perfectly hermetic calorimeter and still allows for the insertion of tracking detectors within the sampling structure to measure the direction of the showering particle. A charged-particle veto system, composed of two scintillator layers, makes it possible to trigger on single photon events and provides e–γ separation. Results are presented from the extensive studies of these detectors in the CERN testbeams prior of installation and of the detector performance at LEP.
121947981
Modified frequentist analysis of search results (The CL(s) method)
The statistical analysis of direct Higgs searches at LEP is described. The likelihood ratio with respect to the background-only hypothesis (or a related teststatistic) is used to order experimental results. The ratio of the confidences in the signal+background to background hypotheses, so-called “CLs”, is used to set lower bounds on the Higgs boson mass. The excluded mass interval which results has an untraditional but useful interpretation which differs both from frequentist intervals which require coverage and from Bayesian credible intervals. Issues such as flip-flopping, experimental uncertainties, discovery significance and the transition to measurement are discussed. The interpretation of results of searches for new particles and phenomena near the sensitivity limit of an experiment is a common problem in particle physics. The loss of sensitivity may be due to a combination of small signal rates, the presence of background comparable to the expected signal, and the loss of discrimination between two models due to insufficient experimental resolution. The search for Higgs bosons at LEP is such an experiment. The LEP experiments have separately, and in collaboration through the LEP working group for Higgs boson searches, developed a nearly common strategy for carrying out and reporting the results of their direct searches. For the time being no significant evidence of Higgs production at LEP has been observed and lower bounds on Higgs masses have been reported. In this report I hope to explain how the lower bound is derived with the so-called CLs method, why this method is used, and how to interpret the result. Since the SM Higgs search has the lowest number of free parameters (1) it will be used to illustrate the features of the CLs method. The generalization to models with several parameters (e.g. the MSSM) is straightforward if more time-consuming in practice. The techniques described in this talk are in fact successfully used in general scans over the many-parameter space of the MSSM in searches for the h and A neutral bosons, in 2-parameter searches for charged Higgs bosons of a general 2-doublet Higgs model, and in combined searches for sparticles by the LEP working group for SUSY particle searches. The individual LEP experiments use either the likelihood ratio, a close approximation of the likelihood ratio, or the integral of the likelihood function as their test-statistics in Higgs searches. Exhaustive studies [1] have shown that they have similar performances for exclusion. To simplify my presentation I only described the likelihood ratio and I will do the same here. I will also show how the CLs method can be applied in other contexts with an example of a hypothetical search for new physics via deviations of a parameter which is measured with normal-distributed uncertainty.
128147551
Searches for the SM Higgs boson at LEP with s**(1//2) <= 189-GeV
110552488
Complete distributed computing environment for a HEP experiment: experience with ARC-connected infrastructure for ATLAS
Computing and storage resources connected by the Nordugrid ARC middleware in the Nordic countries, Switzerland and Slovenia are a part of the ATLAS computing Grid. This infrastructure is being commissioned with the ongoing ATLAS Monte Carlo simulation production in preparation for the commencement of data taking in 2008. The unique non-intrusive architecture of ARC, its straightforward interplay with the ATLAS Production System via the Dulcinea executor, and its performance during the commissioning exercise is described. ARC support for flexible and powerful end-user analysis within the GANGA distributed analysis framework is also shown. Whereas the storage solution for this Grid was earlier based on a large, distributed collection of GridFTP-servers, the ATLAS computing design includes a structured SRM-based system with a limited number of storage endpoints. The characteristics, integration and performance of the old and new storage solutions are presented. Although the hardware resources in this Grid are quite modest, it has provided more than double the agreed contribution to the ATLAS production with an efficiency above 95% during long periods of stable operation.