Forward $\pi^\circ$ production and associated transverse energy flow in deep-inelastic scattering at HERA

Abstract

Deep-inelastic positron-proton interactions at low values of Bjorken-x down to x ≈ 4 · 10 −5 which give rise to high transverse momentum π • -mesons are studied with the H1 experiment at HERA. The inclusive cross section for π • -mesons produced at small angles with respect to the proton remnant (the forward region) is presented as a function of the transverse momentum and energy of the π • and of the four-momentum transfer Q 2 and Bjorken-x. Measurements are also presented of the transverse energy flow in events containing a forward π • -meson. Hadronic final state calculations based on QCD models implementing different parton evolution schemes are confronted with the data.

Challenges with large transverse momentum in semi-inclusive deeply inelastic scattering

“…Given the discussion above, we should expect to find reasonable agreement between fixed order calculations and SIDIS measurements where q T /Q ratios easily exceed 1 and typical x and z are not such that higher orders are extremely large. This at first appears promising when considering H1 [23] kinematics 1 , where the fixed order large-q T prediction from Fig. 4 of [24] (copied here in Fig.…”

“…4 from [24]. The differential cross section was integrated over x, z and bins of Q with H1 cuts, calculated with both leading order and next-to-leading order, and compared with π 0 production data from [23]. Here pT corresponds to our PH,T -see Eq.…”