Hadron Production in Hadron-Hadron and Lepton-Hadron Collisions

Abstract

Summary. We review a recent global analysis of inclusive single-charged-hadron production in high-energy colliding-beam experiments, which is performed at nextto-leading order (NLO) in the parton model of quantum chromodynamics endowed with nonperturbative fragmentation functions (FFs). Comparisons of pp data from CERN SppS and the Fermilab Tevatron and γp data from DESY HERA with the corresponding NLO predictions allow for quantitative tests of the scaling violations in the FFs and their universality. We emphasize the potential of new measurements at the Tevatron to place tight constraints in the large-x region and on the gluon FF, complementary to those from e + e − data, which are indispensible in order to reliably predict the π 0 background for the H → γγ signal of the intermediate-mass Higgs boson at the Tevatron and the CERN LHC. Adopting a similar theoretical framework for b-hadron production, we show that the notorious excess of the Tevatron data over existing theoretical calculations can be ascribed, at sufficiently large values of pT , to nonperturbative fragmentation effects inadequately included previously.

Prompt neutrinos from atmospheric charm in the general-mass variable-flavor-number scheme

“…In order to make the perturbative series converge in the whole kinematic range, the potentially large logarithms can be resummed by properly factorizing the cross section and running the components to their appropriate scales. A suitable framework for this is the zero-mass variable-flavor number scheme (ZM-VFNS) [12][13][14][15][16][17][18][19][20][21][22][23]. Here, also the heavy quark is considered massless and may appear in the initial state.…”

Inclusive D*± meson cross sections and D*±-jet correlations in photoproduction at HERA

“…Heavy quark production is calculated either in the massive scheme [24], where heavy quarks are produced only perturbatively via boson gluon fusion, or in the massless scheme [25], where heavy quarks are treated as massless partons. These two schemes should be appropriate in different regions of phase space [26]: the massive scheme should be reliable when the transverse momentum p t of the heavy quarks is of similar size compared to m c , whereas the massless scheme is expected to be valid for p t m c .…”

“…The zero-mass variable-flavour-number scheme (ZMVFNS) [25,47] provides a next-to-leading order calculation (O(α 2 s )) for D * + other jet cross sections in the collinear approach, neglecting the charm mass. The transition from the charm quark to the D * meson is treated using the scale dependent fragmentation functions determined in [33].…”