THE ZEUS NLO-QCD FIT TO DETERMINE PARTON DISTRIBUTION FUNCTIONS OF PROTON AND STRONG COUPLING CONSTANT αS

2002 ◽  
Author(s):  
K. NAGANO ◽  
Keyword(s):  
Strong Coupling ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Strong Coupling Constant ◽  
Coupling Constant ◽  
Parton Distribution Functions

scholarly journals Erratum to: Determination of the strong coupling constant $${{\varvec{\alpha _{\mathrm{s}} (m_{\mathrm{Z}})}}}$$ in next-to-next-to-leading order QCD using H1 jet cross section measurements

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
◽  
V. Andreev ◽  
A. Baghdasaryan ◽  
K. Begzsuren ◽  
A. Belousov ◽  
...  
Keyword(s):  
Strong Coupling ◽  
Cross Section ◽  
Distribution Functions ◽  
Strong Coupling Constant ◽  
Leading Order ◽  
Coupling Constant ◽  
Parton Distribution Functions ◽  
Section Data ◽  
Dijet Data

AbstractThe determination of the strong coupling constant $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$$ α s ( m Z ) from H1 inclusive and dijet cross section data [1] exploits perturbative QCD predictions in next-to-next-to-leading order (NNLO) [2–4]. An implementation error in the NNLO predictions was found [4] which changes the numerical values of the predictions and the resulting values of the fits. Using the corrected NNLO predictions together with inclusive jet and dijet data, the strong coupling constant is determined to be $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1166\,(19)_{\mathrm{exp}}\,(24)_{\mathrm{th}}$$ α s ( m Z ) = 0.1166 ( 19 ) exp ( 24 ) th . Complementarily, $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$$ α s ( m Z ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1147\,(25)_{\mathrm{tot}}$$ α s ( m Z ) = 0.1147 ( 25 ) tot obtained is consistent with the determination from jet data alone. Corrected figures and numerical results are provided and the discussion is adapted accordingly.

scholarly journals Delineating the Polarized and Unpolarized Parton Structure of the Nucleon

2015 ◽  
Vol 37 ◽  
pp. 1560053
Author(s):  
Pedro Jimenez-Delgado
Keyword(s):  
Parton Distribution ◽  
Distribution Functions ◽  
Distribution Analysis ◽  
Coupling Constant ◽  
Parton Distribution Functions ◽  
Careful Treatment ◽  
Future Data ◽  
The Impact

Reports on our latest extractions of parton distribution functions of the nucleon are given. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are reported, including a careful treatment of hadronic and nuclear corrections, as well as reports on the impact of present and future data in our understanding of the spin of the nucleon.

scholarly journals αs from global fits of parton distribution functions

2016 ◽  
Vol 31 (25) ◽  
pp. 1630023 ◽  
Author(s):  
S. Alekhin ◽  
J. Blümlein ◽  
S.-O. Moch
Keyword(s):  
Inelastic Scattering ◽  
Deep Inelastic Scattering ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Scattering Data ◽  
Hard Scattering ◽  
Coupling Constant ◽  
Parton Distribution Functions ◽  
The Status

The status of the determination of the strong coupling constant [Formula: see text] from deep-inelastic scattering and related hard scattering data is reviewed.

scholarly journals Calculations for deep inelastic scattering using fast interpolation grid techniques at NNLO in QCD and the extraction of $$\alpha _{\mathrm {s}}$$ from HERA data

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
D. Britzger ◽  
J. Currie ◽  
A. Gehrmann-De Ridder ◽  
T. Gehrmann ◽  
E. W. N. Glover ◽  
...  
Keyword(s):  
Inelastic Scattering ◽  
Deep Inelastic Scattering ◽  
Strong Coupling ◽  
Distribution Functions ◽  
Strong Coupling Constant ◽  
Model Parameters ◽  
Coupling Constant ◽  
Section Data ◽  
Inclusive Jet ◽  
Interpolation Grid

Abstract The extension of interpolation-grid frameworks for perturbative QCD calculations at next-to-next-to-leading order (NNLO) is presented for deep inelastic scattering (DIS) processes. A fast and flexible evaluation of higher-order predictions for any a posteriori choice of parton distribution functions (PDFs) or value of the strong coupling constant is essential in iterative fitting procedures to extract PDFs and Standard Model parameters as well as for a detailed study of the scale dependence. The APPLfast project, described here, provides a generic interface between the parton-level Monte Carlo program NNLOjet and both the APPLgrid and fastNLO libraries for the production of interpolation grids at NNLO accuracy. Details of the interface for DIS processes are presented together with the required interpolation grids at NNLO, which are made available. They cover numerous inclusive jet measurements by the H1 and ZEUS experiments at HERA. An extraction of the strong coupling constant is performed as an application of the use of such grids and a best-fit value of $$\alpha _{\mathrm {s}} (M_{{\mathrm {Z}}}) = 0.1170\,(15)_\text {exp}\,(25)_\text {th}$$αs(MZ)=0.1170(15)exp(25)th is obtained using the HERA inclusive jet cross section data.

scholarly journals Constraints on parton distributions and the strong coupling from LHC jet data

2015 ◽  
Vol 30 (31) ◽  
pp. 1546005 ◽  
Author(s):  
Juan Rojo
Keyword(s):  
Strong Coupling ◽  
State Of The Art ◽  
Distribution Functions ◽  
Coupling Constant ◽  
Hadron Colliders ◽  
Parton Distribution Functions ◽  
Jet Production ◽  
Future Developments ◽  
The Impact ◽  
First Time

Jet production at hadron colliders provides powerful constraints on the parton distribution functions (PDFs) of the proton, in particular on the gluon PDF. Jet production can also be used to extract the QCD coupling [Formula: see text] and to test its running with the momentum transfer up to the TeV region. In this review, I summarize the information on PDFs and the strong coupling that has been provided by Run I LHC jet data. First of all, I discuss why jet production is directly sensitive to the gluon and quark PDFs at large-x, and then review the state-of-the-art perturbative calculations for jet production at hadron colliders and the corresponding fast calculations required for PDF fitting. Then I present the results of various recent studies on the impact on PDFs, in particular the gluon, that have been performed using as input jet measurements from ATLAS and CMS. I also review the available determinations of the strong coupling constant based on ATLAS and CMS jet data, with emphasis on the fact that LHC jet data provides, for the first time, a direct test of the [Formula: see text] running at the TeV scale. I conclude with a brief outlook on possible future developments.

DETERMINATION OF THE STRONG COUPLING CONSTANT FROM NLO QCD ANALYSIS OF PROTON STRUCTURE FUNCTION

2011 ◽  
Vol 26 (03n04) ◽  
pp. 658-659 ◽  
Author(s):  
H. KHANPOUR ◽  
ALI N. KHORRAMIAN ◽  
S. ATASHBAR TEHRANI
Keyword(s):  
Structure Function ◽  
Perturbative Qcd ◽  
Strong Coupling ◽  
Distribution Functions ◽  
Strong Coupling Constant ◽  
Proton Structure Function ◽  
Coupling Constant ◽  
Proton Structure ◽  
Qcd Analysis

In this article we present a determination of the strong coupling constant and parton distribution functions (PDFs) based on a next-to-leading order (NLO) perturbative QCD analysis of proton structure function. More precisely, we extract [Formula: see text] and PDFs by fitting perturbative QCD predictions to the data from the measurements of the proton structure function [Formula: see text] in deep inelastic scattering, which are based on perturbative QCD calculations up to NLO. We obtain at NLO [Formula: see text] in the variable-flavor number scheme.

scholarly journals Can $$ \overline{\mathrm{MS}} $$ parton distributions be negative?

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Alessandro Candido ◽  
Stefano Forte ◽  
Felix Hekhorn
Keyword(s):  
Strong Coupling ◽  
Cross Sections ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Leading Order ◽  
Parton Distribution Functions ◽  
Parton Distributions ◽  
Factorization Scheme ◽  
Perturbative Regime

Abstract It is common lore that Parton Distribution Functions (PDFs) in the $$ \overline{\mathrm{MS}} $$ MS ¯ factorization scheme can become negative beyond leading order due to the collinear subtraction which is needed in order to define partonic cross sections. We show that this is in fact not the case and next-to-leading order (NLO) $$ \overline{\mathrm{MS}} $$ MS ¯ PDFs are actually positive in the perturbative regime. In order to prove this, we modify the subtraction prescription, and perform the collinear subtraction in such a way that partonic cross sections remain positive. This defines a factorization scheme in which PDFs are positive. We then show that positivity of the PDFs is preserved when transforming from this scheme to $$ \overline{\mathrm{MS}} $$ MS ¯ , provided only the strong coupling is in the perturbative regime, such that the NLO scheme change is smaller than the LO term.

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