Testing the universality of fragmentation functions

Abstract

Using fragmentation functions for charged pions, charged kaons, and (anti)protons recently extracted from experimental data of e + e − annihilation at the Z-boson resonance and at centre-of-mass energy √ s = 29 GeV, we perform a global study of inclusive charged-hadron production in pp, γp, and γγ collisions at next-to-leading order in the parton model of quantum chromodynamics. Comparisons of our results with pp data from CERN SppS and the Fermilab Tevatron, γp data from DESY HERA, and γγ data from CERN LEP2 allow us to test the universality of the fragmentation functions predicted by the factorization theorem. Furthermore, we perform comparisons with e + e − -annihilation data from LEP2 so as to test the scaling violations predicted by the Altarelli-Parisi evolution equations.

Direct photons in d+Au and p+p collisions

“…The double ratio is consistent with a pQCD calculation [11] based on the CTEQ6M parton density functions [12], the GRV parton-to-photon [13], and the KKP parton-to-pion fragmentation functions [14] as shown for three different factorization scales by the curves in Figure 2. The parton-to-photon fragmentation functions are included since this analysis does not make use of an isolation cut for the photon candidates.…”

Event-by-EventHydrodynamics+JetEnergy Loss: A Solution to theRAA⊗vNoronha-Hostler1, Betz2, Noronha3 et al. 2016Phys. Rev. Lett.11861573View full textAdd to dashboardCite

“…All jet production points with local temperature above 160 MeV are taken into account. In this study we used the KKP pion fragmentation functions [87], which have been tested against RHIC and LHC data [88]. …”

Electromagnetic Probes in PHENIX

“…In √ s = 200GeV p+p collisions the measured π 0 cross section [7] is well described by the KKP set of fragmentation functions [8] up to p T = 13GeV/c (recent preliminary results from Run-5 ex- tend this measurement and confirm the agreement with pQCD up to p T = 18GeV/c). In order to characterize what is different in heavy ion collisions we introduce the nuclear modification factor R AA R AA (p T ) = dN AuAu /dp T T AA · dσ pp /dp T…”