Testing QCD: Direct photons ine + e ? collisions

Koller, K.; Walsh, Thomas; Zerwas, P.M.

doi:10.1007/bf01474661

Cited by 61 publications

(59 citation statements)

References 7 publications

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“…At next-to-leading order (NLO) of perturbative QCD, also gluons fragment into photons through intermediate quarks, which gives rise to the corresponding FF D γ /g (z, Q 2 ). The evolution of these FFs with the scale Q is described by renormalization group equations [15],…”

Section: Photon Fragmentation Functionsmentioning

confidence: 99%

New information on photon fragmentation functions

Klasen

König

2014

Eur. Phys. J. C

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Thermal photons radiated in heavy-ion collisions represent an important signal for a recently discovered new state of matter, the deconfined quark-gluon plasma. However, a clean identification of this signal requires precise knowledge of the prompt photons produced simultaneously in hard collisions of quarks and gluons, mostly through their fragmentation. In this paper, we demonstrate that PHENIX data on photons produced in proton-proton collisions with low transverse momenta allow one to extract new information on this fragmentation process. While existing data do not yet convincingly favor one parameterization (BFG II) over the two other frequently used photon fragmentation functions (BFG I and GRV NLO), the data sets recorded by PHENIX and STAR at BNL RHIC in 2013 with tenfold higher statistics should allow for such an analysis.

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Section: Photon Fragmentation Functionsmentioning

confidence: 99%

New information on photon fragmentation functions

Klasen

König

2014

Eur. Phys. J. C

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“…In resolved events, the photon emitted by the electron fluctuate into a hadronic state and a gluon and/or a quark of this hadronic fluctuation takes part in the hard interactions. Also observed final state photon may arise from fragmentation process [5], where a quark or gluon decays into γ. The cross section of such processes involves relative poorly known partonto-photon fragmentation functions [6].…”

Section: Introductionmentioning

confidence: 99%

Prompt photon photoproduction at DESY HERA in thekT-factorization approach

2005

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We present calculations of the prompt photon photoproduction at HERA collider in the k T -factorization approach. Both direct and resolved contributions are taken into account. The conservative error analisys is performed. The unintegrated parton densities in a proton and in a photon are determined using the Kimber-Martin-Ryskin prescription. We investigate both inclusive and associated with jet prompt photon photoproduction rates. In particular, we study the angular correlations between produced photon and hadronic jet in the transverse momentum plane which can provide a unique information about non-collinear evolution dynamics. We compare our theoretical predictions with recent experimental data taken by the H1 and ZEUS collaborations.

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“…The approach is thus analogous to the calculation of (2 + 1)-and (3 + 1)-jet cross sections, where one of the final state gluons is replaced by a photon [7]. In addition to the direct production, photons can also be produced through the fragmentation of a hadronic jet into a single photon carrying a large fraction of the jet energy [8]. This long-distance process is described in terms of the quark-to-photon and gluon-to-photon fragmentation functions which absorb collinear singularities present in the perturbative calculation.…”

Section: Introductionmentioning

confidence: 99%