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  1. Article: A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties: The NNPDF Collaboration.

    Bertone, Valerio / Carrazza, Stefano / Hartland, Nathan P / Nocera, Emanuele R / Rojo, Juan

    The European physical journal. C, Particles and fields

    2017  Volume 77, Issue 8, Page(s) 516

    Abstract: We present NNFF1.0, a new determination of the fragmentation functions (FFs) of charged pions, charged kaons, and protons/antiprotons from an analysis of single-inclusive hadron production data in electron-positron annihilation. This determination, ... ...

    Abstract We present NNFF1.0, a new determination of the fragmentation functions (FFs) of charged pions, charged kaons, and protons/antiprotons from an analysis of single-inclusive hadron production data in electron-positron annihilation. This determination, performed at leading, next-to-leading, and next-to-next-to-leading order in perturbative QCD, is based on the NNPDF methodology, a fitting framework designed to provide a statistically sound representation of FF uncertainties and to minimise any procedural bias. We discuss novel aspects of the methodology used in this analysis, namely an optimised parametrisation of FFs and a more efficient [Formula: see text] minimisation strategy, and validate the FF fitting procedure by means of closure tests. We then present the NNFF1.0 sets, and discuss their fit quality, their perturbative convergence, and their stability upon variations of the kinematic cuts and the fitted dataset. We find that the systematic inclusion of higher-order QCD corrections significantly improves the description of the data, especially in the small-
    Language English
    Publishing date 2017-08-03
    Publishing country France
    Document type Journal Article
    ZDB-ID 1459069-4
    ISSN 1434-6052 ; 1434-6044
    ISSN (online) 1434-6052
    ISSN 1434-6044
    DOI 10.1140/epjc/s10052-017-5088-y
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Boosting Higgs pair production in the [Formula: see text] final state with multivariate techniques.

    Behr, J Katharina / Bortoletto, Daniela / Frost, James A / Hartland, Nathan P / Issever, Cigdem / Rojo, Juan

    The European physical journal. C, Particles and fields

    2016  Volume 76, Issue 7, Page(s) 386

    Abstract: The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking and has a unique sensitivity to the Higgs ... ...

    Abstract The measurement of Higgs pair production will be a cornerstone of the LHC program in the coming years. Double Higgs production provides a crucial window upon the mechanism of electroweak symmetry breaking and has a unique sensitivity to the Higgs trilinear coupling. We study the feasibility of a measurement of Higgs pair production in the [Formula: see text] final state at the LHC. Our analysis is based on a combination of traditional cut-based methods with state-of-the-art multivariate techniques. We account for all relevant backgrounds, including the contributions from light and charm jet mis-identification, which are ultimately comparable in size to the irreducible 4
    Language English
    Publishing date 2016-07-08
    Publishing country France
    Document type Journal Article
    ZDB-ID 1459069-4
    ISSN 1434-6052 ; 1434-6044
    ISSN (online) 1434-6052
    ISSN 1434-6044
    DOI 10.1140/epjc/s10052-016-4215-5
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: A determination of the charm content of the proton: The NNPDF Collaboration.

    Ball, Richard D / Bertone, Valerio / Bonvini, Marco / Carrazza, Stefano / Forte, Stefano / Guffanti, Alberto / Hartland, Nathan P / Rojo, Juan / Rottoli, Luca

    The European physical journal. C, Particles and fields

    2016  Volume 76, Issue 11, Page(s) 647

    Abstract: We present an unbiased determination of the charm content of the proton, in which the charm parton distribution function (PDF) is parametrized on the same footing as the light quarks and the gluon in a global PDF analysis. This determination relies on ... ...

    Abstract We present an unbiased determination of the charm content of the proton, in which the charm parton distribution function (PDF) is parametrized on the same footing as the light quarks and the gluon in a global PDF analysis. This determination relies on the NLO calculation of deep-inelastic structure functions in the FONLL scheme, generalized to account for massive charm-initiated contributions. When the EMC charm structure function dataset is included, it is well described by the fit, and PDF uncertainties in the fitted charm PDF are significantly reduced. We then find that the fitted charm PDF vanishes within uncertainties at a scale [Formula: see text] GeV for all [Formula: see text], independent of the value of [Formula: see text] used in the coefficient functions. We also find some evidence that the charm PDF at large [Formula: see text] and low scales does not vanish, but rather has an "intrinsic" component, very weakly scale dependent and almost independent of the value of [Formula: see text], carrying less than [Formula: see text] of the total momentum of the proton. The uncertainties in all other PDFs are only slightly increased by the inclusion of fitted charm, while the dependence of these PDFs on [Formula: see text] is reduced. The increased stability with respect to [Formula: see text] persists at high scales and is the main implication of our results for LHC phenomenology. Our results show that if the EMC data are correct, then the usual approach in which charm is perturbatively generated leads to biased results for the charm PDF, though at small
    Language English
    Publishing date 2016-11-24
    Publishing country France
    Document type Journal Article
    ZDB-ID 1459069-4
    ISSN 1434-6052 ; 1434-6044
    ISSN (online) 1434-6052
    ISSN 1434-6044
    DOI 10.1140/epjc/s10052-016-4469-y
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Parton distributions from high-precision collider data: NNPDF Collaboration.

    Ball, Richard D / Bertone, Valerio / Carrazza, Stefano / Debbio, Luigi Del / Forte, Stefano / Groth-Merrild, Patrick / Guffanti, Alberto / Hartland, Nathan P / Kassabov, Zahari / Latorre, José I / Nocera, Emanuele R / Rojo, Juan / Rottoli, Luca / Slade, Emma / Ubiali, Maria

    The European physical journal. C, Particles and fields

    2017  Volume 77, Issue 10, Page(s) 663

    Abstract: We present a new set of parton distributions, NNPDF3.1, which updates NNPDF3.0, the first global set of PDFs determined using a methodology validated by a closure test. The update is motivated by recent progress in methodology and available data, and ... ...

    Abstract We present a new set of parton distributions, NNPDF3.1, which updates NNPDF3.0, the first global set of PDFs determined using a methodology validated by a closure test. The update is motivated by recent progress in methodology and available data, and involves both. On the methodological side, we now parametrize and determine the charm PDF alongside the light-quark and gluon ones, thereby increasing from seven to eight the number of independent PDFs. On the data side, we now include the D0 electron and muon
    Language English
    Publishing date 2017-10-04
    Publishing country France
    Document type Journal Article
    ZDB-ID 1459069-4
    ISSN 1434-6052 ; 1434-6044
    ISSN (online) 1434-6052
    ISSN 1434-6044
    DOI 10.1140/epjc/s10052-017-5199-5
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Book ; Online: Parton distributions from high-precision collider data

    The NNPDF Collaboration / Ball, Richard D. / Bertone, Valerio / Carrazza, Stefano / Del Debbio, Luigi / Forte, Stefano / Groth-Merrild, Patrick / Guffanti, Alberto / Hartland, Nathan P. / Kassabov, Zahari / Latorre, José I. / Nocera, Emanuele R. / Rojo, Juan / Rottoli, Luca / Slade, Emma / Ubiali, Maria

    2017  

    Abstract: We present a new set of parton distributions, NNPDF3.1, which updates NNPDF3.0, the first global set of PDFs determined using a methodology validated by a closure test. The update is motivated by recent progress in methodology and available data, and ... ...

    Abstract We present a new set of parton distributions, NNPDF3.1, which updates NNPDF3.0, the first global set of PDFs determined using a methodology validated by a closure test. The update is motivated by recent progress in methodology and available data, and involves both. On the methodological side, we now parametrize and determine the charm PDF alongside the light quarks and gluon ones, thereby increasing from seven to eight the number of independent PDFs. On the data side, we now include the D0 electron and muon W asymmetries from the final Tevatron dataset, the complete LHCb measurements of W and Z production in the forward region at 7 and 8 TeV, and new ATLAS and CMS measurements of inclusive jet and electroweak boson production. We also include for the first time top-quark pair differential distributions and the transverse momentum of the Z bosons from ATLAS and CMS. We investigate the impact of parametrizing charm and provide evidence that the accuracy and stability of the PDFs are thereby improved. We study the impact of the new data by producing a variety of determinations based on reduced datasets. We find that both improvements have a significant impact on the PDFs, with some substantial reductions in uncertainties, but with the new PDFs generally in agreement with the previous set at the one sigma level. The most significant changes are seen in the light-quark flavor separation, and in increased precision in the determination of the gluon. We explore the implications of NNPDF3.1 for LHC phenomenology at Run II, compare with recent LHC measurements at 13 TeV, provide updated predictions for Higgs production cross-sections and discuss the strangeness and charm content of the proton in light of our improved dataset and methodology. The NNPDF3.1 PDFs are delivered for the first time both as Hessian sets, and as optimized Monte Carlo sets with a compressed number of replicas.

    Comment: Revised version, to be publ.in EPJC. Typos corrected and points clarified. Figs 2.4, 4.21, 4.30 and 4.31 added. PDF comparison plots added. Fit with nuclear corrections added in Sect 4.11. Labeling of all distance plots corrected (u and d were interchanged). Points in charm cross-sections without cuts added to Tab 3.2
    Keywords High Energy Physics - Phenomenology ; High Energy Physics - Experiment
    Subject code 306
    Publishing date 2017-06-01
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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