660 research outputs found

    Additional Soft Jets in ttˉ{\rm t\bar{t}} Production at the Tevatron \pp Collider

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    A large fraction of top quark events in \pp collisions at 1.8\ \TeV will contain additional soft hadronic jets from gluon bremsstrahlung off the quarks and gluons in the hard processes \qq, gg \to \tt \to \bb \ww. These extra jets can cause complications when attempting to reconstruct mtm_t from the invariant mass of combinations of final-state quarks and leptons. We show how such soft radiation cannot be unambiguously associated with either initial-state radiation or or with final-state radiation off the bb quarks. The top quarks can radiate too, and in fact the pattern of radiation has a very rich structure, which depends on the orientation of the final-state particles with respect to each other and with respect to the beam. We calculate the full radiation pattern of soft jets in the soft gluon approximation and compare with several approximate forms which are characteristic of parton shower Monte Carlos. The implications for top mass measurements are discussed.Comment: plain LaTeX, 13 pages plus 9 figures included as a separate uuencoded file (or avail. from authors); DTP/94/60, UR-136

    Direct Measurement of the Top Quark Charge at Hadron Colliders

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    We consider photon radiation in tbar-t events at the upgraded Fermilab Tevatron and the CERN Large Hadron Collider (LHC) as a tool to measure the electric charge of the top quark. We analyze the contributions of tbar-t-gamma production and radiative top quark decays to p-p, pbar-p -> gamma l^+/- nu bbar-b jj, assuming that both b-quarks are tagged. With 20~fb^{-1} at the Tevatron, the possibility that the ``top quark'' discovered in Run I is actually an exotic charge -4/3 quark can be ruled out at the 95% confidence level. At the LHC, it will be possible to determine the charge of the top quark with an accuracy of about 10%.Comment: Revtex, 24 pages, 2 tables, 9 figure

    Slides for Focus Group-UTM

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    These slides form the first talking points for the CON3 focus groups. They are designed to give an overview of the UTM project to people with no prior knowledge so they can help us with ideas for a public portal USS

    Seroconversion to HCoV-NL63 in Rhesus Macaques

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    HCoV-NL63 is a recently identified respiratory virus. Its pathogenesis has not been fully unraveled because an animal model is currently lacking. Here we examined whether rhesus macaques encounter HCoV-NL63 infections during life, by examining the levels of antibodies to HCoV-NL63 in time. The animals were followed for 7 up till 19 years, and in three animals we observed a steep rise in antibodies during follow up, indicative of a natural infection with HCoV-NL63

    An overview of early investigational drugs for the treatment of human papilloma virus infection and associated dysplasia

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    Introduction: High-risk HPV (HR-HPV) related invasive cervical cancer (ICC) causes >270,000 deaths per annum world-wide with over 85% of these occurring in low-resource countries. Ablative and excisional treatment modalities are restricted for use with high-grade pre-cancerous cervical disease with HPV infection and low-grade dysplasia mostly managed by a watch-and-wait policy.Areas Covered: Various pharmacological approaches have been investigated as non-destructive alternatives for the treatment of HR-HPV infection and associated dysplasia. These are discussed dealing with efficacy, ease-of-use (physician or self-applied), systemic or locally applied, side-effects, cost and risks. The main focus is the perceived impact on current clinical practice of a self-applied, effective and safe pharmacological anti-HPV treatment.Expert opinion: Current prophylactic HPV vaccines are expensive, HPV type restricted and have little effect in already infected women. Therapeutic vaccines are under development but are also HPV type-restricted. At present, the developed nations use national cytology screening and surgical procedures to treat only women identified with HPV-related high-grade dysplastic disease. However, since HPV testing is rapidly replacing cytology as the test-of-choice, a suitable topically-applied and low-cost antiviral treatment could be an ideal solution for treatment of HPV infection per se with test-of-cure carried out by repeat HPV testing. Cytology would only then be necessary for women who remained HPV positive. Although of significant benefit in the developed countries, combining such a treatment with self-sampled HPV testing could revolutionise the management of this disease in the developing world which lack both the infrastructure and resources to establish national cytology screening programs

    Evaluation of APREQCFR Coordination Procedures for Charlotte Douglas International Airport

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    NASA has been collaborating with the Federal Aviation Administration (FAA) and aviation industry partners to develop and demonstrate new concepts and technologies for the Integrated Arrival, Departure, and Surface (IADS) traffic management capabilities under the Airspace Technology Demonstration 2 (ATD-2) project. One of the goal of The IADS capabilities in the ATD-2 project is to increase predictability and increase throughput via improving TMI compliance. The IADS capabilities that will impact TMI compliance are built upon previous NASA research, the Precision Departure Release Capability (PDRC). The proposed paper will evaluate the APREQCFR process between ATC Tower and Center and information sharing between ATC Tower and the airline Ramp tower. Subjective measures collected from the HITL surveys (e.g., workload, situational awareness, acceptability, usability) and performance metrics such as TMI, TMAT, and pushback advisory compliance from APREQCFR flights and will be reported

    Gluon Radiation in ttˉt\bar t Production and Decay at the LHC

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    Understanding the pattern of gluon radiation in ttˉt \bar t production and decay processes is important for making an accurate determination of the top mass from the momenta of its decay products. The larger energy of the LHC pppp collider boosts the top cross section by a factor of 100 compared to that at the Tevatron, but it also increases the amount of additional gluon radiation. We calculate the cross section for gluon radiation in top production and decay at the LHC. The distributions of this radiation are presented and the exact matrix-element results are compared with results from the HERWIG parton-shower Monte Carlo.Comment: 16 pages including 7 figures, plain LaTeX; minor corrections to text; results unchange

    Are Debris Disks and Massive Planets Correlated?

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    Using data from the Spitzer Space Telescope Legacy Science Program ``Formation and Evolution of Planetary Systems'' (FEPS), we have searched for debris disks around 9 FGK stars (2-10 Gyr), known from radial velocity (RV) studies to have one or more massive planets. Only one of the sources, HD 38529, has excess emission above the stellar photosphere; at 70 micron the signal-to-noise ratio in the excess is 4.7 while at wavelengths < 30 micron there is no evidence of excess. The remaining sources show no excesses at any Spitzer wavelengths. Applying survival tests to the FEPS sample and the results for the FGK survey published in Bryden et al. (2006), we do not find a significant correlation between the frequency and properties of debris disks and the presence of close-in planets. We discuss possible reasons for the lack of a correlation.Comment: 24 pages, 3 figures. Accepted to Astrophysical Journa

    NASA's UTM Research

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    The Technology Capability Level-2 National Campaign (TCL2nc) was conducted at six different test sites located across the USA, during May and June of 2017. The campaign resulted in over 250 data collection flights using 26 different aircraft and involving 23 flight crews. Flights not only varied in duration, but also in the environments and terrains over which they flew. The TCL2nc highlighted beyond visual line of sight (BVLOS) and altitude-stratified operations, and saw five partners bring their own, independently built, UTM Service Supplier (USS) for use during the flight tests. This document presents data collected during the TCL2nc that informs the 'Operator' section of the 'Requirements/Best Practices' from the UTM Technical Capability Matrix and Guidelines to Operate (Rios, version as of March 2017). A review of the data collected indicated that although teams were well qualified on paper (in terms of both completing training and having experience with flying UAS vehicles), greater consideration should be given to the unique perspectives and backgrounds of future UAS operators. Overall, teams looked at a variety of sources for information, including USS client-displays, and participants became more aware of the need to be aware of other vehicles, highlighting the value of reporting information. Observations found that flight crews' time to respond to a UTM issue depended heavily on the team structure, communication efficiency, and crew procedures
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