Pion and kaon production ine+e−andep

Abstract

We present new sets of fragmentation functions for charged pions and kaons, both at leading and next-to-leading order. They are fitted to data on inclusive charged-hadron production in e+eannihilation taken by the TPC Collaboration at SLAC PEP (fi = 29 GeV) and to similar data by ALEPH at CERN LEP, who discriminated between events with charm, bottom, and light-flavor fragmentation in their charged-hadron sample. In contrast with our previous analysis, where we only distinguished between valence-quark, sea-quark, and gluon fragmentation, we are now able to treat all partons independently and to properly incorporate the charm and bottom thresholds. Because of the sizable energy gap between PEP and LEP, we are sensitive to the scaling violation in the fragmentation process, which allows us to extract a value for the asymptotic scale parameter of QCD, A. Recent data on inclusive charged-hadron production in tagged three-jet events by OPAL and similar data for longitudinal electron polarization by ALEPH allow us to pin down the gluon fragmentation functions. Our new fragmentation functions lead to an excellent description of a multitude of other e+e-data on inclusive charged-hadron production, ranging from fi = 5.2 GeV to LEP energy. In addition, they agree nicely with the transverse-momentum spectra of single charged hadrons measured by H1 and ZEUS in photoproduction at the DESY ep collider HERA, which represents a nontrivial check of the factorization theorem of the QCD-improved parton model. In this comparison, we also find first evidence for the interplay between the direct-and resolvedphoton mechanisms and for the existence of a gluon density inside the photon.PACS number(s): 13.65.+i, 13.60.Le, 13.87.Fh, 14.40.Aq LO FF's for ( T + + n-)

Unintegrated parton distributions and pion production in pp collisions at RHIC energies

“…The k tfactorization is much better but still some contribution is missing at large Feynman x F and at small transverse momenta. However, one should remember that other processes such as In Fig.4 we show our full result (diagrams A, B 1 and B 2 [13]) for different fragmentation functions [23,24,26]. In this calculation b 0 = 0.5 GeV −1 was used.…”

“…In the present application different fragmentation functions from the literature [23,24,26] will be used. All of them were obtained in global fits to the e + e − data.…”

Electroproduction of neutral pions in the Hall A at the Jefferson Laboratory; Electroproduction de pions neutres dans le Hall A au Jefferson Laboratory

“…and its inversion ∆k out 44) with U out uniform between 0 and 1. Note that the internal real radiative corrections are simulated in the event generation, but not in the full GEANT simulation of the detector.…”

“…Fragmentation functions are generally extracted from e + e − annihilation. Their parameterization frequently takes the form [43,44] 51) and they are normalized by 52) with N h the average multiplicity of the hadron h in inclusive process or in e + e − annihilation process.…”

Clustering, GUT Scale and Neutrino Masses in Ultrahigh Energy Cosmic Rays

“…For the proton's FF at present accelerator energies we use ref. [26]. We evolve the FFs in ordinary and in supersymmetric QCD to the energies of the SPs.…”