Contents

We discuss the current minimisation strategies adopted by research projects involving the determination of parton distribution functions (PDFs) and fragmentation functions (FFs) through the training of neural networks. We present a short overview of a proton PDF determination obtained using the covariance matrix adaptation evolution strategy (CMA-ES) optimisation algorithm. We perform comparisons between the CMA-ES and the standard nodal genetic algorithm (NGA) adopted by the NNPDF collaboration

Research infrastructures in the LHC era : a scientometric approach

When a research infrastructure is funded and implemented, new information and new publications are created. This new information is the measurable output of discovery process. In this paper, we describe the impact of infrastructure for physics experiments in terms of publications and citations. In particular, we consider the Large Hadron Collider (LHC) experiments (ATLAS, CMS, ALICE, LHCb) and compare them to the Large Electron Positron Collider (LEP) experiments (ALEPH, DELPHI, L3, OPAL) and the Tevatron experiments (CDF, D0). We provide an overview of the scientific output of these projects over time and highlight the role played by remarkable project results in the publication-citation distribution trends. The methodological and technical contributions of this work provide a starting point for the development of a theoretical model of modern scientific knowledge propagation over time

APFELgrid: A high performance tool for parton density determinations

We present a new software package designed to reduce the computational burden of hadron collider measurements in Parton Distribution Function (PDF) fits. The APFELgrid package converts interpolated weight tables provided by APPLgrid files into a more efficient format for PDF fitting by the combination with PDF and as evolution factors provided by APFEL. This combination significantly reduces the number of operations required to perform the calculation of hadronic observables in PDF fits and simplifies the structure of the calculation into a readily optimised scalar product. We demonstrate that our technique can lead to a substantial speed improvement when compared to existing methods without any reduction in numerical accuracy. Program Summary Program Title: APFELgrid Program Files doi: http://dx.doi.org/10.17632/mhwjt5nsg7.1 Licensing provisions: MIT license Programming language: C++ Nature of problem: Fast computation of hadronic observables under the variation of parton distribution functions. Solution method: Combination of interpolated weight grids from APPLgrid files and evolution factors from APFEL into efficient FastKernel tables. External routines/libraries: APPLgrid, APFE

Towards an unbiased determination of parton distributions with QED corrections

Electroweak corrections to hadron collider processes become relevant at the level of precision reached by present-day LHC experiments. We provide a preliminary discussion of the impact of electroweak corrections to parton distributions, concentrating on electrodynamics corrections to parton evolution equations, and showing a preliminary assessment of their impact. Furthermore, we determine the parton distribution function of the photon from deep inelastic scattering data using the NNPDF methodology

Engaging lay people to build a resilient Big Science organization? Some preliminary insights

Knowledge co-production in \u201cBig Science\u201d projects \u2013 i.e. scientific endeavours characterized by organizational complexity due to their size, exploratory nature, and diversity of participating specializations, cultures, and individual orientations (Child, Ihrig, and Merali, 2014) \u2013 is a brand-new concept, which is based on the assumption that lay people are able to establish dynamic and contingent relationships with professional researchers and/or expert scientists, in an attempt to contribute in forming, validating, and adapting knowledge (Bonney et al., 2014). Our aim here is to draw a more comprehensive picture of this phenomenon, in order to better frame, on the one hand, the conceptual and contextual underpinnings of knowledge co-production in Big Science and, on the other hand, to disentangle the role played by lay people who \u2013 as volunteers \u2013 support expert scientists in pushing forward scientific knowledge. Also, this paper focuses on how knowledge co-production empowers Big Science organizations\u2019 capacity and dynamic reach, enabling them to develop a greater ability to manage unforeseen and/or unforeseeable external forces and to become more resilient

Les Houches 2015: Physics at TeV Colliders Standard Model Working Group Report

This Report summarizes the proceedings of the 2015 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt with (I) new developments relevant for high precision Standard Model calculations, (II) the new PDF4LHC parton distributions, (III) issues in the theoretical description of the production of Standard Model Higgs bosons and how to relate experimental measurements, (IV) a host of phenomenological studies essential for comparing LHC data from Run I with theoretical predictions and projections for future measurements in Run II, and (V) new developments in Monte Carlo event generators.Comment: Proceedings of the Standard Model Working Group of the 2015 Les Houches Workshop, Physics at TeV Colliders, Les Houches 1-19 June 2015. 227 page

The photon PDF from high-mass Drell Yan data at the LHC

Achieving the highest precision for theoretical predictions at the LHC requires the calculation of hard-scattering cross-sections that include perturbative QCD corrections up to (N)NNLO and electroweak (EW) corrections up to NLO. Parton distribution functions (PDFs) need to be provided with matching accuracy, which in the case of QED effects involves introducing the photon parton distribution of the proton, $x\gamma(x,Q^2)$. In this work a determination of the photon PDF from fits to recent ATLAS measurements of high-mass Drell-Yan dilepton production at $\sqrt{s}=8$ TeV is presented. This analysis is based on the xFitter framework, and has required improvements both in the APFEL program, to account for NLO QED effects, and in the aMCfast interface to account for the photon-initiated contributions in the EW calculations within MadGraph5_aMC@NLO. The results are compared with other recent QED fits and determinations of the photon PDF, consistent results are found