Pion PDFs

See below for recent highlights of pion PDFs in JAM.  Click images for enlargement.

PION PDFS WITH THRESHOLD RESUMMATION (2021)

A new paper by the Jefferson Lab Angular Momentum (JAM) collaboration reports the first global QCD analysis of the pion's quark and gluon (parton) distribution functions (PDFs) within a Bayesian Monte Carlo framework with threshold re-summation. Threshold resummation is a technique to account for logarithmic corrections in perturbative QCD calculations arising from partonic threshold effects that occur in corners of kinematics, such as when a single parton carries a large fraction x of the pion's momentum. Exploring various treatments of resummation, the study finds that the large-x asymptotics of the valence quark distribution ∼ (1 − x)β can differ significantly, with β ranging from ≈ 1 to > 2.5. Regardless of the specific implementation, however, the resummation induced redistribution of the momentum between valence quarks and gluons boosts the total momentum carried by gluons to 40%, increasing the gluon contribution to the pion mass to ≈ 40 MeV.

TOWARDS THE THREE-DIMENSIONAL PARTON STRUCTURE OF THE PION (2021)

A new Monte Carlo QCD analysis of pion parton distributions has been performed by the Jefferson Lab Angular Momentum collaboration (JAM), including for the first time the transverse momentum (pT) dependent pion-nucleus Drell-Yan cross sections together with pT -integrated Drell-Yan and leading neutron electroproduction data from HERA. The study assesses the sensitivity of the Monte Carlo fits to kinematic cuts, factorization scale and parametrization choice, and it discusses the impact of the various data sets on the pion's quark and gluon distributions. The work provides the necessary step toward the simultaneous analysis of collinear and transverse momentum dependent pion distributions and the determination of the pion's three-dimensional structure.

PION PDFS WITH THRESHOLD RESUMMATION (2021)

A new paper by the Jefferson Lab Angular Momentum (JAM) collaboration reports the first global QCD analysis of the pion's quark and gluon (parton) distribution functions (PDFs) within a Bayesian Monte Carlo framework with threshold re-summation. Threshold resummation is a technique to account for logarithmic corrections in perturbative QCD calculations arising from partonic threshold effects that occur in corners of kinematics, such as when a single parton carries a large fraction x of the pion's momentum. Exploring various treatments of resummation, the study finds that the large-x asymptotics of the valence quark distribution ∼ (1 − x)β can differ significantly, with β ranging from ≈ 1 to > 2.5. Regardless of the specific implementation, however, the resummation induced redistribution of the momentum between valence quarks and gluons boosts the total momentum carried by gluons to 40%, increasing the gluon contribution to the pion mass to ≈ 40 MeV.

TOWARDS THE THREE-DIMENSIONAL PARTON STRUCTURE OF THE PION (2021)

A new Monte Carlo QCD analysis of pion parton distributions has been performed by the Jefferson Lab Angular Momentum collaboration (JAM), including for the first time the transverse momentum (pT) dependent pion-nucleus Drell-Yan cross sections together with pT -integrated Drell-Yan and leading neutron electroproduction data from HERA. The study assesses the sensitivity of the Monte Carlo fits to kinematic cuts, factorization scale and parametrization choice, and it discusses the impact of the various data sets on the pion's quark and gluon distributions. The work provides the necessary step toward the simultaneous analysis of collinear and transverse momentum dependent pion distributions and the determination of the pion's three-dimensional structure.