B.T. King

Measurement and QCD analysis of the photon structure function F2(x, Q2)

Abstract We present a measurement of the hadronic structure function F2γ(x, Q2) of the photon in the Q2 range from 10 to 100 GeV2. Data were taken with the PLUTO detector at the e+e- storage ring PETRA. This measurement and previous PLUTO measurements in the Q2 range of 1.5 to 16 GeV2 are compared with higher order QCD calculations. The structure function is consistent with the predicted log Q2 behaviour when charm contributions are subtracted. The x dependence can be well described for 0.1 Λ MS = 183 + 65/ −40( stat. ) + 46/ −36( sys. ) MeV for the QCD scale parameter.

Measurement of the total photon-photon cross section for the production of hadrons at small Q2

The total photon-photon cross section for the production of hadrons, σγγ(W, Q2), has been measured in the single-tag condition for 0.1 < Q2 < 1.0 GeV2 and 1.5 < W < GeV. The results are based on 2929 multihadron events obtained with the PLUTO detector at PETRA. The Q2 dependence of σγγ average over W can be described by GVDM. The dependence of σγγ on the mass W of the hadronic final state has been extracted at Q2 = 0.44 GeV2 by unfolding the effects of experimental resolution and acceptance. The cross section is found to rise at small W. The result is compared with VDM and the parton model.

Measurement of exclusive η′ production in γγ reactions

Abstract We observe γγ → η′ production in the reaction e + e − → e + e − π + π − γ. We measure the product γ γγ ( η ′) B ( η ′ → ϱ 0 γ ) to be 1.14 ± 0.08 ± 0.11 keV. A first measurement of the γγ → η′ transition form factor is made for Q 2 up to 1 GeV 2 .

Evidence for exclusive ηc production in γγ interactions

Abstract We observe for evidence for γγ → η c production in the reaction e + e − → e + e − K S 0 K ± π ∓ . The product Γ γγ ( η c )· B ( η c → K S 0 K ± π ∓ ) is measured to be 0.5 −0.15 +0.2 ±0.1 keV.

Tagged two photon production of muon Pairs

The processe+e−→e+e− μ+μ− has been studied using the PLUTO detector at PETRA. The data agree well with QED calculations to order α4. Comparison is also made with the predicted leptonic structure function of the real photon using the deep inelastice-γ scattering formalism.

Formation of the tensor meson A2(1320) in photon-photon interactions

Abstract We have measured the reaction γγ → π + π − π 0 using the PLUTO detector at PETRA. A pronounced enhancement is seen in the π + π − π 0 mass distribution corresponding to the A 2 meson. The event configuration in this enhancement favors a 2 + spin-parity assignment. The value of Γ γγ =1.06 ±0.18±0.19 keV obtained for the two-photon decay width of the A 2 agrees with previous measurements and with quark model predictions.

Exclusive production of hadron pairs at large momentum transfer in photon-photon interactions

Abstract We report on the exclusive production of π, K and proton pairs from photon-photon interactions at momentum transfers | t |⩾1 GeV 2 . Using the PLUTO detector at the e + e − storage ring PETRA, we have observed 15 events in an integrated luminosity of 41.7 pb −1 . The data lie far below the expectations for point-like hadrons, and are in reasonable agreement with the QCD-based predictions of Brodsky and Lepage.

A measurement of theQ 2 andW dependence of the ?? total cross section for hadron production

A measurement of the γγ total cross section, σγγ(Q2W), is presented for theQ2 range 0.1 to 100 GeV2, and for the massW of the hadronic final state between 1.5 and 10 GeV. The dependence of σγγ on bothQ2 andW is measured. The results are compared with theoretical predictions. It is found that the data are well described by a sum of quarkparton model and vector dominance contributions.

A Measurement of the

A measurement of the γγ total cross section, σγγ(Q2W), is presented for theQ2 range 0.1 to 100 GeV2, and for the massW of the hadronic final state between 1.5 and 10 GeV. The dependence of σγγ on bothQ2 andW is measured. The results are compared with theoretical predictions. It is found that the data are well described by a sum of quarkparton model and vector dominance contributions.