Resummation, Evolution, Factorization 2022

Session

PDF uncertainties, PDF theory

PDF uncertainties

31 Oct 2022, 16:10

Conveners

PDF uncertainties, PDF theory: PDF uncertainties

• Natasa Raicevic

PDF uncertainties, PDF theory: PDF uncertainties

• Laurent Favart (Université Libre de Bruxelles)

14. MSHT20 - Inclusion of Theoretical Uncertainties and Higher Order Effects into PDFs

Thomas Cridge

31/10/2022, 16:10

I will discuss our recent paper within the MSHT PDF collaboration on the inclusion of theoretical uncertainties and higher order (N3LO) terms into the MSHT PDFs, producing the MSHT20aN3LO (approximate N3LO) set. This represents the first global analysis of parton distribution functions (PDFs) at approximate N3LO as well as the first inclusion of theoretical uncertainties from missing higher...

20. Comments on global parton analyses

Ryskin Mikhail

31/10/2022, 16:30

We consider a few effects which are usually ignored in PDF studies.

1. The double counting of the low $k_T included in the NLO splitting and coefficient functions, and that hidden in the
   PDF input at $Q=Q_0$. Formally this is a power $Q^2/\mu^2$ correction but
   it is non-negligible at moderate scales $\mu$.
2. The $\epsilon/\epsilon$ contribution generated by the...

9. Triple-collinear one-loop splitting functions in QCD

Sebastian Sapeta (IFJ PAN, Kraków)

31/10/2022, 16:50

I shall present the results for one-loop triple-collinear splitting operators for all five possible sub-processes. The expressions are exact in dimensionally-regulated massless QCD up to a single integral, which we expand to second order in the dimensional-regularisation parameter. Our results are both sufficient and indispensable for the construction of subtraction and integrated-subtraction...

6. Alien operators and the four-loop DGLAP evolution

Giulio Falcioni (Nikhef)

31/10/2022, 17:40

The scale evolution of the parton distribution functions is controlled by the anomalous dimensions of twist-two operators, which correspond to the Mellin moments of the DGLAP splitting functions. The four-loop anomalous dimensions are important for precision physics at the LHC and at the future EIC. Computing the anomalous dimensions of the flavour singlet operators is highly challenging, due...

34. Theoretical uncertainties on the evolution of alpha_s, PDFs, and TMDs

Valerio Bertone (NIKHEF)

31/10/2022, 18:00

The QCD strong coupling (alpha_s) and the parton distribution functions, both collinear (PDFs) and transverse-momentum dependent (TMDs), are fundamental ingredients for phenomenology at high-energy facilities such as the Large Hadron Collider (LHC).
It is therefore of crucial importance to estimate any theoretical uncertainties associated to them.

Both alpha_s and PDFs/TMDs obey their own...

77. Theoretical and sampling uncertainties in global PDF fits.

Aurore Courtoy (Instituto de Física, UNAM)

31/10/2022, 18:20

We review recent developments on the estimation of uncertainties in unpolarized nucleon PDFs by the CT group. In particular, we will discuss how global PDF analyses can be affected by the so-called “big-data paradox” and why, as a consequence, sampling uncertainties should be considered. From that point, we will also discuss theoretical non-perturbative aspects of determinations of strange,...

85. PDF uncertainties in TMD extractions

Ignazio Scimemi

31/10/2022, 18:40

A recent study of the Artemide group has analyzed the impact of PDF uncertainties in the extractions of TMD from data. This result shows that beyond the usual chi^2 analysis, a control of PDF replica distributions must be achieved in order to remove differences among different PDF sets in TMD analysis. When this is achieved, errors coming from several PDF sets are finally found compatible...