Parton content of virtual photons

Abstract

The QCD treatment of the parton structure of virtual photons is briefly recalled, and possible limitations and open questions are pointed out. Various models for these densities are compared, completed by a short discussion of the treatment of heavy flavors. Finally, different ways to measure the parton distributions of virtual photons in e + e − and ep experiments are summed up.Talk presented at the workshop on 'Photon Interactions and the Photon Structure', Lund, Sweden, September 1998. The Parton Content of Virtual Photons

Constraining gluon shadowing using photoproduction in ultraperipheralpAandAAcollisions

“…Another source of differences is in the choice and scope of experimental data from which F γ 2 is extracted. At present there is an appreciable number of photon parton distribution sets available, both at leading and next-to-leading orders [55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70]. It should be noted that unlike in the case of a nucleon, there are no valence quarks present in the photon; therefore antiquark distributions are the same as quark distributions.…”

Spin structure function of the virtual photon beyond the leading order in QCD

“…And the parton contents of virtual photon were studied in ref. [14,15] and the target mass effect of unpolarized and polarized virtual photon structure in LO was discussed in ref. [16].…”

First measurement of the photon structure function F[sub 2,c][sup γ]

“…for different values of m c is shown in Figure 3, using the SaS1D [5] and GRS [6] parametrisations. For x > 0.1 the structure function is saturated by the point-like component which is only slowly suppressed for increasing virtualities P 2 of the quasi-real photon.…”