1,721,118 research outputs found
Perturbative RGE systematics in precision observables
Full text linkQCD calculations for collider physics make use of perturbative solutions of renormalization group equations. Ambiguities related to these solutions can contribute significantly to systematic uncertainties of theoretical predictions for physical observables. We propose a general method to estimate these systematic effects using techniques inspired by soft-gluon and transverse-momentum resummation approaches. We first discuss the cases of the evolution of strong coupling αs, collinear parton-distribution functions, and transverse-momentum-dependent distributions. We then study the implications for precision observables in hadron-collider processes, such as the deep-inelastic scattering structure functions and the transverse-momentum distribution of the lepton pair in Drell-Yan production
Constraining Parton Distribution Functions from neutral current Drell-Yan measurements
Full text linkWe study the cross section σ and forward-backward asymmetry (AFB) in the process pp→γ∗,Z→+- (with =e, μ) for determinations of parton distribution functions (PDFs) of the proton. We show that, once mapped in the invariant mass of the dilepton final state, M(), both observables, σ and AFB, display a statistical error which is presently competitive with that assigned to the existing PDF sets and which will rapidly become smaller than the latter as the luminosity being accumulated at Run-II of the LHC grows. This statement is applicable to both on-peak and off-peak M() regions, both (just) below and above it, thereby offering a means of constraining the quark PDFs over a sizable (x,Q2) range.</p
Lepton-Charge and Forward-Backward Asymmetries in Drell-Yan Processes for Precision Electroweak Measurements and New Physics Searches
Full text linkPrecision determinations of Standard Model (SM) Electro-Weak (EW) parameters at the Large Hadron Collider (LHC) are dominated by uncertainties due to Parton Distribution Functions (PDFs). Reweighting and profiling techniques are routinely employed to treat this. We explore approaches based on combining measurements of charged current and neutral current Drell-Yan (DY) asymmetries to improve PDF uncertainties. We present the results of a numerical analysis performed with the open-source platform xFitter . PDF uncertainties are examined for lepton-charge and forward-backward asymmetries in regions of transverse and invariant masses near the vector-boson peak, based on LHC Run III and HL-LHC luminosity scenarios. We discuss the complementarity of the asymmetries in reducing PDF uncertainties in observables relevant to both SM and Beyond the SM (BSM) physics.Precision determinations of Standard Model (SM) Electro-Weak (EW) parameters at the Large Hadron Collider (LHC) are dominated by uncertainties due to Parton Distribution Functions (PDFs). Reweighting and profiling techniques are routinely employed to treat this. We explore approaches based on combining measurements of charged current and neutral current Drell-Yan (DY) asymmetries to improve PDF uncertainties. We present the results of a numerical analysis performed with the open-source platform xFitter. PDF uncertainties are examined for lepton-charge and forward-backward asymmetries in regions of transverse and invariant masses near the vector-boson peak, based on LHC Run III and HL-LHC luminosity scenarios. We discuss the complementarity of the asymmetries in reducing PDF uncertainties in observables relevant to both SM and Beyond the SM (BSM) physics
Resummation Scales and the Assessment of Theoretical Uncertainties in Parton Distribution Functions
Full text linkWe discuss perturbative solutions of renormalization group equations, and
propose the use of resummation scale techniques in assessing theoretical
uncertainties on the extraction of parton distribution functions from data.Comment: 4 pages, 2 figures. Contribution to Proceedings of 29th Workshop on
Deep-Inelastic Scattering and Related Subjects (May 2022
Enhancing the Large Hadron Collider Sensitivity to Charged and Neutral Broad Resonances of New Gauge Sectors
Full text linkIn scenarios beyond the Standard Model (BSM) characterised by charged (W′) or neutral (Z′) massive gauge bosons with large width, resonant mass searches are not very effective, so that one has to exploit the tails of the mass distributions measured at the Large Hadron Collider (LHC). In this case, the LHC sensitivity to new physics signals is influenced significantly by systematic uncertainties associated with the Parton Distribution Functions (PDF), particularly in the valence quark sector relevant for the multi-TeV mass region. As a BSM framework featuring such conditions, we consider the 4-Dimensional Composite Higgs Model (4DCHM), in which multiple W′ and Z′ broad resonances are present, with strongly correlated properties. By using the QCD tool xFitter, we study the implications on W′ and Z′ searches in Drell-Yan (DY) lepton decay channels that follow from the reduction of PDF uncertainties obtained through combining high-statistics precision measurements of DY lepton-charge and forward-backward asymmetries. We find that the sensitivity to the BSM states is greatly increased with respect to the case of base PDF sets, thereby enabling one to set more stringent limits on (or indeed discover) such new particles, both independently and in correlated searches.In scenarios beyond the Standard Model (BSM) characterized by charged () or neutral () massive gauge bosons with large width, resonant mass searches are not very effective, so that one has to exploit the tails of the mass distributions measured at the Large Hadron Collider (LHC). In this case, the LHC sensitivity to new physics signals is influenced significantly by systematic uncertainties associated with the Parton Distribution Functions (PDF), particularly in the valence quark sector relevant for the multi-TeV mass region. As a BSM framework featuring such conditions, we consider the 4-Dimensional Composite Higgs Model (4DCHM), in which multiple and broad resonances are present, with strongly correlated properties. By using the QCD tool xFitter, we study the implications on and searches in Drell-Yan (DY) lepton decay channels that follow from the reduction of PDF uncertainties obtained through combining high-statistics precision measurements of DY lepton-charge and forward-backward asymmetries. We find that the sensitivity to the BSM states is greatly increased with respect to the case of base PDF sets, thereby enabling one to set more stringent limits on (or indeed discover) such new particles, both independently and in correlated searches
Neutral current forward-backward asymmetry: from theta(W) to PDF determinations
No full textMeasurements of the forward–backward asymmetry in neutral-current Drell–Yan di-lepton production have primarily been used for determinations of the weak mixing angle θW. We observe that, unlike the case of Run-I of the Large Hadron Collider (LHC Run-I), for the first time at the LHC Run-II the reconstructed forward–backward asymmetry has the capability of placing useful constraints on the determination of the parton distribution functions (PDFs). By examining the statistical and the PDF uncertainties on the reconstructed forward–backward asymmetry, we investigate its potential for disentangling the flavour content of quark and antiquark PDFs. Access to the valence/sea u-quark and to the sea up-type antiquark PDFs, in particular, may be gained by the appropriate use of selection cuts in the rapidity of the emerging lepton pair in regions both near the Z-boson peak and away from it, in a manner complementary, though more indirect, to the case of the charged-current asymmetry. We study the extension of these results for the planned high-luminosity (HL) LHC.</p
Erratum to: Neutral current forward-backward asymmetry: from W to PDF determinations (vol 78, 663, 2018)
No full textWe submit an Erratum for our paper Eur. Phys. J. C (2018) 78: 663 (ID: EPJC-18-06-165), with title “Neutral current Forward-Backward Asymmetry:</p
-boson dilepton searches and the high- quark density
Full text linkWe study the influence of theoretical systematic uncertainties due to the quark density on LHC experimental searches for Z′-bosons. Using an approach originally proposed in the context of the ABMP16 PDF set for the high-x behaviour of the quark density, we present results on observables commonly used to study Z′ signals in dilepton channels.We study the influence of theoretical systematic uncertainties due to the quark density on LHC experimental searches for -bosons. Using an approach originally proposed in the context of the ABMP16 PDF set for the high- behaviour of the quark density, we presents results on observables commonly used to study signals in dilepton channels
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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