8,509 research outputs found

    Top Quark Properties from the Tevatron

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    This report describes latest measurements and studies of top quark properties from the Tevatron in RunII with an integrated luminosity of up to 750pb-1. Due to its large mass of about 172GeV, the top quark provides a unique environment for tests of the Standard Model and is believed to yield sensitivity to new physics beyond the Standard Model. With data samples of close to 1fb-1 the CDF and D0 collaborations at the Tevatron enter a new aera of precision top quark measurements.Comment: 5 pages, Contribution to Proceedings of XLth Rencontres de Moriond 2006, Electroweak Interactions and Unified Theories, La Thuile, Italy, 11-18 March 200

    Physics Goals and Experimental Challenges of the Proton-Proton High-Luminosity Operation of the LHC

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    The completion of Run 1 of the CERN Large Hadron Collider has seen the discovery of the Higgs boson and an unprecedented number of precise measurements of the Standard Model, while Run 2 operation has just started to provide first data at higher energy. Upgrades of the LHC to high luminosity (HL-LHC) and the experiments (ATLAS, CMS, ALICE and LHCb) will exploit the full potential of the collider to discover and explore new physics beyond the Standard Model. In this article, the experimental challenges and the physics opportunities in proton-proton collisions at the HL-LHC are reviewed

    Beam Imaging and Luminosity Calibration

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    We discuss a method to reconstruct two-dimensional proton bunch densities using vertex distributions accumulated during LHC beam-beam scans. The xx-yy correlations in the beam shapes are studied and an alternative luminosity calibration technique is introduced. We demonstrate the method on simulated beam-beam scans and estimate the uncertainty on the luminosity calibration associated to the beam-shape reconstruction to be below 1\%.Comment: Figures added, typos correcte

    Evaluation of hole sizes in structures requiring EVA services as a means to prevent gloved-hand finger entrapment

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    One of the concerns of Space Station designers was making sure that the suited crewmembers' gloved fingers are not trapped in the holes that may be present in the structures during EVA activities. A study was conducted on 11 subjects to determine the minimum and maximum possible hole sizes that would eliminate the possibility of finger entrapment. Subjects wore pressurized gloves and attempted to insert their fingers into holes of various sizes. Based on the experimental results, it is recommended that the smallest diameter should be less than 13.0 mm and the largest diameter should be greater than 35.0 mm in order to eliminate the possibility of finger entrapment while wearing gloves. It is also recommended that the current requirements specified by the MSIS-STD-3000 (Section 6.3.3.4) should be modified accordingly

    A comparison of hand grasp breakaway strengths and bare-handed grip strengths of the astronauts, SML 3 test subjects, and the subjects from the general population

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    Astronauts have the task of retrieving and deploying satellites and handling massive objects in a around the payload bay. Concerns were raised that manual handling of such massive objects might induce loads to the shuttle suits exceeding the design-certified loads. The Crew and Thermal Division of NASA JSC simulated the satellite handling tasks (Satellite Manload Tests 1 and 3) and determined the maximum possible load that a suited member could impart onto the suit. In addition, the tests revealed that the load to the suit by an astronaut could be calculated from the astronaut's maximum hand grasp breakaway strength. Thus, this study was conducted to document that hand grasp breakaway strengths of the astronauts who were scheduled to perform EVA during the upcoming missions. In addition, this study verified whether the SML 3 test results were sufficient for documenting the maximum possible load. An attempt was made to predict grasp strength from grip strength and hand anthropometry. Based on the results from this study, the SML 3 test results were deemed sufficient to document the maximum possible load on the suit. Finally, prediction of grasp strength from grip strength was not as accurate as expected. Hence, it was recommended that grasp strength be collected from the astronauts in order to obtain accurate load estimation

    Anthropometric data from launch and entry suited test subjects for the design of a recumbent seating system

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    Returning space crews to Earth in a recumbent position requires the design of a new seating system. Current anthropometric data are based on measurements taken while the subjects were unsuited and sitting. To be most accurate, it is necessary to design by measurements of subjects in the launch and entry suit in a recumbent position. Since the design of the recumbent seating system must meet the requirements of both 5th percentile Japanese female and 95th percentile American male crew members, a delta is reported rather than absolute measurements of the test subjects. This delta is the difference in the measurements taken with the subjects unsuited and sitting and those taken with the subjects suited and recumbent. This delta, representative of the change due to the suit, can be added to the existing Man-Systems Integration Standards (NASA-STD-3000) anthropometric data to project the measurements for 5th percentile Japanese female and 95th percentile American male crew members. A delta accounting for the spinal elongation caused by prolonged exposures to microgravity is added as well. Both unpressurized and pressurized suit conditions are considered. Background information, the test protocol and procedure, analysis of the data, and recommendations are reported

    Measuring Higgs Couplings from LHC Data

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    Following recent ATLAS and CMS publications we interpret the results of their Higgs searches in terms of Standard Model operators. For a Higgs mass of 125 GeV we determine several Higgs couplings from 2011 data and extrapolate the results towards different scenarios of LHC running. Even though our analysis is limited by low statistics we already derive meaningful constraints on modified Higgs sectors.Comment: 5 pages, 4 figure

    Measuring Higgs Couplings at a Linear Collider

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    Higgs couplings can be measured at a linear collider with high precision. We estimate the uncertainties of such measurements, including theoretical errors. Based on these results we show an extrapolation for a combined analysis at a linear collider and a high-luminosity LHC.Comment: 4 pages, 2 figures; v2: small text clarification, results unchanged, version to appear in EP

    Minimizing Crossings in Constrained Two-Sided Circular Graph Layouts

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    Circular layouts are a popular graph drawing style, where vertices are placed on a circle and edges are drawn as straight chords. Crossing minimization in circular layouts is NP-hard. One way to allow for fewer crossings in practice are two-sided layouts that draw some edges as curves in the exterior of the circle. In fact, one- and two-sided circular layouts are equivalent to one-page and two-page book drawings, i.e., graph layouts with all vertices placed on a line (the spine) and edges drawn in one or two distinct half-planes (the pages) bounded by the spine. In this paper we study the problem of minimizing the crossings for a fixed cyclic vertex order by computing an optimal k-plane set of exteriorly drawn edges for k >= 1, extending the previously studied case k=0. We show that this relates to finding bounded-degree maximum-weight induced subgraphs of circle graphs, which is a graph-theoretic problem of independent interest. We show NP-hardness for arbitrary k, present an efficient algorithm for k=1, and generalize it to an explicit XP-time algorithm for any fixed k. For the practically interesting case k=1 we implemented our algorithm and present experimental results that confirm the applicability of our algorithm
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