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22 papers found.
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Neutrino telescopes as QCD microscopes

Abstract We present state-of-the-art predictions for the ultra-high energy (UHE) neutrino-nucleus cross-sections in charged- and neutral-current scattering. The calculation is performed in the framework of collinear factorisation at NNLO, extended to include the resummation of small-x BFKL effects. Further improvements are made by accounting for the free-nucleon PDF constraints...

Direct photon production and PDF fits reloaded

Direct photon production in hadronic collisions provides a handle on the gluon PDF by means of the QCD Compton scattering process. In this work we revisit the impact of direct photon production on a global PDF analysis, motivated by the recent availability of the next-to-next-to-leading (NNLO) calculation for this process. We demonstrate that the inclusion of NNLO QCD and leading...

Parton distributions with small-x resummation: evidence for BFKL dynamics in HERA data

We present a determination of the parton distribution functions of the proton in which NLO and NNLO fixed-order calculations are supplemented by NLLx small-x resummation. Deep-inelastic structure functions are computed consistently at \(\hbox {NLO+NLL}x\) or \(\hbox {NNLO+NLL}x\), while for hadronic processes small-x resummation is included only in the PDF evolution, with...

Higgs pair production in vector-boson fusion at the LHC and beyond

The production of pairs of Higgs bosons at hadron colliders provides unique information on the Higgs sector and on the mechanism underlying electroweak symmetry breaking (EWSB). Most studies have concentrated on the gluon-fusion production mode which has the largest cross section. However, despite its small production rate, the vector-boson fusion channel can also be relevant...

Precision determination of the strong coupling constant within a global PDF analysis

Zahari Kassabov 3 Juan Rojo 4 5 Emma Slade 6 Maria Ubiali 7 0 The Higgs Centre for Theoretical Physics, University of Edinburgh , JCMB, KB, Mayfield Rd, Edinburgh, Scotland EH9 3JZ , UK 1 Theoretical

A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties

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...

Pinning down the large-x gluon with NNLO top-quark pair differential distributions

Abstract Top-quark pair production at the LHC is directly sensitive to the gluon PDF at large x. While total cross-section data is already included in several PDF determinations, differential distributions are not, because the corresponding NNLO calculations have become available only recently. In this work we study the impact on the large-x gluon of top-quark pair differential...

The asymptotic behaviour of parton distributions at small and large x

It has been argued from the earliest days of quantum chromodynamics that at asymptotically small values of x the parton distribution functions (PDFs) of the proton behave as \(x^\alpha \), where the values of \(\alpha \) can be deduced from Regge theory, while at asymptotically large values of x the PDFs behave as \((1-x)^\beta \), where the values of \(\beta \) can be deduced...

The prompt atmospheric neutrino flux in the light of LHCb

The recent observation of very high energy cosmic neutrinos by IceCube heralds the beginning of neutrino astronomy. At these energies, the dominant background to the astrophysical signal is the flux of ‘prompt’ neutrinos, arising from the decay of charmed mesons produced by cosmic ray collisions in the atmosphere. In this work we provide predictions for the prompt atmospheric...

A compression algorithm for the combination of PDF sets

The current PDF4LHC recommendation to estimate uncertainties due to parton distribution functions (PDFs) in theoretical predictions for LHC processes involves the combination of separate predictions computed using PDF sets from different groups, each of which comprises a relatively large number of either Hessian eigenvectors or Monte Carlo (MC) replicas. While many fixed-order...

Charm production in the forward region: constraints on the small-x gluon and backgrounds for neutrino astronomy

The recent observation by the IceCube experiment of cosmic neutrinos at energies up to a few PeV heralds the beginning of neutrino astronomy. At such high energies, the ‘conventional’ neutrino flux is suppressed and the ‘prompt’ component from charm meson decays is expected to become the dominant background to astrophysical neutrinos. Charm production at high energies is however...

Parton distributions with threshold resummation

We construct a set of parton distribution functions (PDFs) in which fixed-order NLO and NNLO calculations are supplemented with soft-gluon (threshold) resummation up to NLL and NNLL accuracy respectively, suitable for use in conjunction with any QCD calculation in which threshold resummation is included at the level of partonic cross sections. These resummed PDF sets, based on...

Epidemiology of home enteral nutrition: an approximation to reality

  , Pilar Cao-Sánchez1  , Reyes Durán-Martínez1  , María José Rodríguez-Iglesias1  , Brígida Rodríguez-Blanco4  , Juan Rojo-Valdés4  1Departments of Endocrinology and Nutrition. Complejo Hospitalario

Parton distributions from high-precision collider data

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...

Characterizing new physics with polarized beams at high-energy hadron colliders

Abstract The TeV energy region is currently being explored by both the ATLAS and CMS experiments of the Large Hadron Collider and phenomena beyond the Standard Model are extensively searched for. Large fractions of the parameter space of many models have already been excluded, and the ranges covered by the searches will certainly be increased by the upcoming energy and luminosity...

Scale-invariant resonance tagging in multijet events and new physics in Higgs pair production

We study resonant pair production of heavy particles in fully hadronic final states by means of jet substructure techniques. We propose a new resonance tagging strategy that smoothly interpolates between the highly boosted and fully resolved regimes, leading to uniform signal efficiencies and background rejection rates across a broad range of masses. Our method makes it possible...

Cross section ratios between different CM energies at the LHC: opportunities for precision measurements and BSM sensitivity

Michelangelo L. Mangano 0 Juan Rojo 0 0 PH Department, TH Unit , CERN, CH-1211 Geneva 23, Switzerland The staged increase of the LHC beam energy provides a new class of interesting observables

Bayesian reweighting of nuclear PDFs and constraints from proton-lead collisions at the LHC

New hard-scattering measurements from the LHC proton-lead run have the potential to provide important constraints on the nuclear parton distributions and thus contributing to a better understanding of the initial state in heavy ion collisions. In order to quantify these constraints, as well as to assess the compatibility with available nuclear data from fixed target experiments...

Constraints on the gluon PDF from top quark pair production at hadron colliders

AbstractUsing the recently derived NNLO cross sections [1], we provide NNLO+NNLL theoretical predictions for top quark pair production based on all the available NNLO PDF sets, and compare them with the most precise LHC and Tevatron data. In this comparison we study in detail the PDF uncertainty and the scale, m t and α s dependence of the theoretical predictions for each PDF set...

Jet reconstruction in heavy ion collisions

We examine the problem of jet reconstruction at heavy-ion colliders using jet-area-based background subtraction tools as provided by FastJet. We use Monte Carlo simulations with and without quenching to study the performance of several jet algorithms, including the option of filtering, under conditions corresponding to RHIC and LHC collisions. We find that most standard...