Using methods of effective field theory, we derive the first all-order factorization theorem for the Higgs-boson production cross section with a jet veto, imposed by means of a standard sequential recombination jet algorithm. Like in the case of small-q T resummation in Drell-Yan and Higgs production, the factorization is affected by a collinear anomaly. Our analysis provides the basis for a systematic resummation of large logarithms ln(m H /p veto T) beyond leading-logarithmic order. Specifically, we present predictions for the resummed jet-veto cross section and efficiency at next-to-next-to-leading logarithmic order. Our results have important implications for Higgs-boson searches at the LHC, where a jet veto is required to suppress background events.

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In constructing collinear operators, which describe the production of energetic jets or energetic hadrons, important constraints are provided by reparametrization invariance (RPI). RPI encodes Lorentz invariance in a power expansion about a collinear direction, and connects the Wilson coefficients of operators at different orders in this expansion to all orders in α s . We construct reparametrization invariant collinear objects. The expansion of operators built from these objects provides an efficient way of deriving RPI relations and finding a minimal basis of operators, particularly when one has an observable with multiple collinear directions and/or soft particles. Complete basis of operators are constructed for pure glue currents at twist-4, and for operators with multiple collinear directions, including those appearing in e + e − → 3 jets, and for pp → 2 jets initiated via gluon-fusion. * Electronic address: cmarcant@mit.edu † Electronic address: iains@mit.edu 1 In Ref. [18] it was shown that the construction of heavy-to-light operators can be simplified if only operators in a particular frame are required, by taking linear combinations of the RPI transformations that only act in this frame. In Ref. [15] this was described as the derivation of RPI conditions on a projected surface, and the complete set of such transformations was used for the O(λ 2 ) analysis done there. The formalism derived here makes a full analysis sufficiently simple that the consideration of projected surfaces becomes unnecessary.

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The Robert Schuman Centre for Advanced Studies (RSCAS), created in 1992 and directed by Brigid Laffan since September 2013, aims to develop inter-disciplinary and comparative research and to promote work on the major issues facing the process of integration and European society.The Centre is home to a large post-doctoral programme and hosts major research programmes and projects, and a range of working groups and ad hoc initiatives. The research agenda is organised around a set of core themes and is continuously evolving, reflecting the changing agenda of European integration and the expanding membership of the European Union. Climate Policy Research UnitThe Climate Policy Research Unit (CPRU) is a research group within the Robert Schuman Centre for Advanced Studies under the Loyola de Palacio Chair. The goal of the CPRU is to provide a reliable source for information and analysis of EU climate policy and a forum for discussion of research carried out in this area among government officials, academics and industry.The CPRU was established in 2010 at the initiative of Josep Borrell, former President of the EUI and former President of the European Parliament, as a means of providing more focus to European climate policy developments. The director of the CPRU is Denny Ellerman, part-time professor at the RSCAS, and recently retired as a Senior Lecturer from MIT's Sloan School of Management. The CPRU works in collaboration with the energy and regulatory policy research groups of the Florence School of Regulation and Loyola de Palacio Chair and with the Global Governance Programme at the EUI. Starting in 2012, the CPRU has been funded primarily by the European Commission (DG Climate Action).The opinions expressed in this paper are those of the author(s) and do not represent the views of the European University Institute or any of its subsidiary components or those of the European Commission.For more information:http://fsr.eui.eu/CPRU/Index.aspx AbstractThis paper provides an introduction to the EU's Emissions Trading System. As such it provides a discussion of the historical and legal context in which the EU ETS developed and now operates, a presentation of the key performance indicators for the first eight years through the end of the second phase in 2012, and some concluding observations on the system's future. The paper is purposively descriptive to provide background for more analytically oriented articles, as well as to provide a matter-of-fact presentation for readers who wish to learn about or be updated on the progress of the EU ETS.