What did HERA teach us about the structure of the proton?

Abstract

Starting in 2008 the H1 and ZEUS experiments have been combining their data in order to provide the most complete and accurate set of deep-inelastic data as the legacy of HERA. The present review presents these combinations, both published and preliminary, and explores how they have been used to give information on the structure of the proton. The HERAPDF parton distribution functions (PDFs) are presented and compared with other current PDFs and with data from the Tevatron and LHC colliders.

DETERMINATION OF CHARM QUARK MASS AND αs(MZ) FROM HERA DATA

“…This more flexible parametrisation is called HERAPDF1.5f. 1 The extra flexibility does not change the NLO PDFs central values significantly, and the PDF uncertainties are also not much increased.…”

“…The full details for all HERAPDFs are given in Ref. 1. The experimental uncertainties on the HERAPDF are determined using the conventional χ 2 tolerance, ∆χ 2 = 1, for 68% C.L.…”

“…The for- A. M. Cooper-Sarkar malism of how the deep inelastic cross-sections relate to the parton distributions though the QCD-improved parton model, and how parton distribution functions are then extracted from the data, is well-documented (see, for example Ref. 1) and only a brief description of the HERAPDF formalism will be given here. This contribution concentrates on results of relevance for the fundamental parameters of QCD: α s (M Z ) and the charm quark mass m c .…”

Nonlinear effects and the behavior of total hadronic and photonic cross sections

“…Once established the energy dependence of the total and inelastic pp and p " p cross sections (1), the inelastic proton-Air, the total gamma-proton, and gammagamma cross sections were then obtained according to Eqs. (5), (7), and (8).…”

Impact of charm H1-ZEUS combined data and determination of the strong coupling in two different schemes

“…As we can see from Eqs. (19)(20)(21)(22), we obtain four different values of χ 2 TOTAL /dof, corresponding to four different fits, which in turn imply four different fit-qualities in some PDFs. Now, according to the relative change of χ 2 , which is defined by…”