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Topical afternoon on parton distribution functions

Aula Conversi (Dip. di Fisica - Edificio G. Marconi)

Aula Conversi

Dip. di Fisica - Edificio G. Marconi

Angelo Esposito (Istituto Nazionale di Fisica Nucleare)
    • 2:30 PM 3:20 PM
      New frontiers in the determination of Parton Distribution Functions 50m

      The interpretation of LHC data, and the assessment of possible hints of new physics, require the precise knowledge of the proton structure in terms of parton distribution functions (PDFs). In this talk I will illustrate recent progress in PDF global fits, and the challenges of providing a precise and accurate determination of such functions.
      I will also present new studies that shed light on the interplay between the parametrization of the proton structure and the parametrization of new physics, according to two complementary approaches. On the one hand, a new framework is introduced, which allows the determination of PDFs alongside the Wilson coefficients of a model-independent EFT to parametrize heavy new physics. On the other hand, a systematic methodology designed to determine whether and how global PDF fits might inadvertently ‘fit away’ signs of new physics in the high-energy tails of the distributions are presented. A scenario in which the PDFs may completely absorb such signs of new physics is showcased. Strategies to single out the effects in this scenario and disentangle the inconsistencies that stem from them are discussed.

      Speaker: Maria Ubiali (University of Cambridge)
    • 3:20 PM 4:00 PM
      Precision measurement of the Z-boson transverse momentum and consequent extraction of the strong coupling constant. 40m

      This seminar presents a precise measurement of the production properties of the Z-boson in the full phase space of the decay leptons, based on 8 TeV pp collision data collected by the ATLAS experiment in 2012. The double-differential cross-section distributions in Z-boson transverse momentum and rapidity are measured in the pole region. In a novel approach, the measured Z transverse momentum is used to determine the strong coupling constant. The analysis uses state-of-the-art predictions at third order accuracy in perturbative QCD, supplemented by resummation of logarithmically-enhanced contributions in the small transverse-momentum region of the lepton pairs. The extracted alphaS(mZ) result is the most precise single measurement to date.

      Speaker: Francesco Giuli (CERN)
    • 4:00 PM 4:25 PM
      Theoretical Motivations and Experimental Confirms of the Quantum Statistical Parton Distribution Functions 25m

      The Quantum Statistical Parton Distributions, which follows logically from the role of Pauli principle, have received also recently experimental confirms and describe better the large-x region than the standard distributions. The stability of the value of the "Temperature", $\bar{x}$, is remarkable.

      Speaker: Franco Buccella (NA)