33,147 research outputs found

    Parton Distributions in the Higgs Boson Era

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    Parton distributions are an essential ingredient of the LHC program. PDFs are relevant for precision Standard Model measurements, for Higgs boson characterization as well as for New Physics searches. In this contribution I review recent progress in the determination of the parton distributions of the proton during the last year. Important developments include the impact of new LHC measurements to pin down poorly known PDFs, studies of theoretical uncertainties, higher order calculations for processes relevant for PDF determinations, PDF benchmarking exercises with LHC data, as well as methodological and statistical improvements in the global analysis framework. I conclude with some speculative considerations about future directions in PDF determinations from the theory point of view.Comment: 11 pages, 5 figures, write-up of the plenary talk at the XXI International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2013), Marseille, 22-26 April 201

    PDF uncertainties in the determination of the W boson mass and of the effective lepton mixing angle at the LHC

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    The precision measurement of the W boson mass allows to perform stringent consistency tests of the Standard Model by means of global electroweak fits. The accurate determination of the W boson mass is one of the legacy results of the Tevatron, where the experimental accuracy is such that MWM_W is now limited by theoretical uncertainties related to the parton distributions of the proton. In this contribution, we show how to quantify the impact of PDF uncertainties in the measurement of MWM_W at the Tevatron and the LHC by means of a template method, and study both the use of the W transverse mass and the lepton pT kinematical distributions to generate these templates. We also present preliminary results on the quantification of the PDF uncertainties in the determination of the effective lepton mixing angle at the LHC, based on the same template method as for the W mass determinationComment: 5 pages, 4 figures, to appear in the proceedings of the XXI International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2013), Marseille, 22-26 April 201

    Improving quark flavor separation with forward W and Z production at LHCb

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    We quantify the constraints on the flavour separation between the quarks and antiquarks in the proton provided by the recent forward weak gauge boson production data from the LHCb experiment at s=7\sqrt{s}=7 and 8 TeV. Performed in the framework of the NNPDF3.1 global analysis, this study highlights the key role that the LHCb W and Z data have in achieving a robust quark flavour separation in the large-x region, including the strange and charm quarks. We demonstrate how the LHCb measurements lead to improved determinations of the the up and down quark PDFs in the region x0.1x\ge 0.1, with an uncertainty reduction that can be as large as a factor 2. We also show how the LHCb forward measurements severely restrict the size of the fitted charm PDF at large x, imposing stringent constraints on non-perturbative models for the charm content of the nucleon.Comment: 5 pages, 5 figures, to appear in the proceedings of the XXV International Workshop on Deep-Inelastic Scattering and Related Subjects, 3-7 April 2017, University of Birmingham, U

    Erich Leo Lehmann---A glimpse into his life and work

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    Through the use of a system-building approach, an approach that includes finding common ground for the various philosophical paradigms within statistics, Erich L. Lehmann is responsible for much of the synthesis of classical statistical knowledge that developed from the Neyman--Pearson--Wald school. A biographical sketch and a brief summary of some of his many contributions are presented here. His complete bibliography is also included and the references present many other sources of information on his life and his work.Comment: Published in at http://dx.doi.org/10.1214/11-AOS927 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Brief history of the Lehmann Symposia: Origins, goals and motivation

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    The idea of the Lehmann Symposia as platforms to encourage a revival of interest in fundamental questions in theoretical statistics, while keeping in focus issues that arise in contemporary interdisciplinary cutting-edge scientific problems, developed during a conversation that I had with Victor Perez Abreu during one of my visits to Centro de Investigaci\'{o}n en Matem\'{a}ticas (CIMAT) in Guanajuato, Mexico. Our goal was and has been to showcase relevant theoretical work to encourage young researchers and students to engage in such work. The First Lehmann Symposium on Optimality took place in May of 2002 at Centro de Investigaci\'{o}n en Matem\'{a}ticas in Guanajuato, Mexico. A brief account of the Symposium has appeared in Vol. 44 of the Institute of Mathematical Statistics series of Lecture Notes and Monographs. The volume also contains several works presented during the First Lehmann Symposium. All papers were refereed. The program and a picture of the participants can be found on-line at the website http://www.stat.rice.edu/lehmann/lst-Lehmann.html.Comment: Published at http://dx.doi.org/10.1214/074921706000000347 in the IMS Lecture Notes--Monograph Series (http://www.imstat.org/publications/lecnotes.htm) by the Institute of Mathematical Statistics (http://www.imstat.org

    Review on recent developments in jet finding

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    We review recent developments related to jet clustering algorithms and jet finding. These include fast implementations of sequential recombination algorithms, new IRC safe algorithms, quantitative determination of jet areas and quality measures for jet finding, among many others. We also briefly discuss the status of jet finding in heavy ion collisions, where full QCD jets have been measured for the first time at RHIC.Comment: 5 pages, 5 figures, proceedings of the International Symposium on Multiparticle Dynamics 08, 15-20 september 2008, DES

    Study of macroscopic and microscopic properties of liposomes produced using microfluidic methods

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    For the last decades, lipid vesicles or liposomes, vesicles formed by a bilayer of amphiphilic lipids, have been used as a toy model for studying the cell membrane and for applications in cosmetics and drug delivery. Traditional methods for producing liposomes face some problems such as the heterogeneity in size and composition of the liposomes produced. A few years ago, a novel method that produces liposomes with homogeneous size and composition was developed. This novel method is based on the use of water in oil in water ultra-thin double emulsions, with lipids dissolved in the oil phase, as templates for the liposome production. These ultra-thin double emulsions are produced using glass capillary microfluidic devices. This new method for producing liposomes seems very promising, but since the liposomes are formed by the oil phase evaporation of the double emulsions, the doubt that some residual oil in the bilayer may alter the properties of the liposomes appears. In this work different phenomena and properties of liposomes that have been studied for the ones produced using conventional methods are studied for liposomes produced using microfluidic methods. The microfluidic apprOutgoin
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