Inclusive cross sections for pairs of identified light charged hadrons and for single protons ine+e−ats=10.58 

Abstract

We report the first double differential cross sections of two charged pions and kaons (e + e − → hhX) in electron-positron annihilation as a function of the fractional energies of the two hadrons for any charge and hadron combination. The dependence of these di-hadron cross sections on the topology (same, opposite-hemisphere or anywhere) is also studied with the help of the event shape variable thrust and its axis. The ratios of these di-hadron cross sections for different charges and hadron combinations directly shed light on the contributing fragmentation functions. For example, we find that the ratio of same-sign pion pairs over opposite-sign pion pairs drops toward higher fractional energies where disfavored fragmentation is expected to be suppressed. These di-hadron results are obtained from a 655 fb −1 data sample collected near the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. Extending the previously published single-pion and single-kaon cross sections, single-proton (e + e − → pX) cross sections are extracted from a 159 fb −1 data sub-sample.

Measurements of fragmentation functions and implications for semi-inclusive deep-inelastic scattering

“…[25,26,27], the addition of the B-factory measurements contributes to significant reductions of the uncertainties, especially in the gluon and light-quark fragmentation functions. Comparing those data to the LEP data clearly indicate QCD scaling violations, and the different electroweak coupling at the different scales even Cross section for inclusive production of single charged pions, kaons as well as (anti)protons [9] as a function of the fractional energy z, compared to different PYTHIA tunes.…”

“…Recently, in the process of analyzing inclusive production of hadron pairs, the Belle collaboration revisited the single-hadron cross-section measurement and included, in a somewhat coarser kinematic binning, also results for protons and anti-protons [9]. The cross sections are shown in Fig.…”

“…[35]. Hadrons in opposite hemispheres are predominantly produced by different partons and can thus be used to further constrain the flavor dependence of fragmentation functions, but also to study the transverse-momentum [9]. Note that for the unlike-hadron pairs a factor two is missing in the cross sections.…”

“…[39]. The recent results from Belle on inclusive cross sections of hadron pairs [9] do not focus on the transverse momentum dependence (those are subject to ongoing analyses), but on the flavor dependence of hadronization and the hemisphere decomposition of hadron pair production. A clear hierarchy depending on topology and hadron species can be made out in Fig.…”

“…In particular, when studying the transversemomentum structure of the nucleon through semi-inclusive DIS it will be unavoidable to also know the transverse-momentum structure of hadronization as the transverse momentum of the hadrons in semi-inclusive DIS arises through convolutions of the transverse-momentum dependence of both the parton distribution and fragmentation functions. Fragmentation functions are mainly constrained through measurements of semi-inclusive DIS [2,3,4,5] and of hadron production in electron-positron annihilation, especially the very precise data from the B factories [6,7,8,9,10,11,12]. [In case of transverse-momentum integrated fragmentation functions, data on hadron production in proton-proton collision is also used in global analyses.]…”