Summary of the structure function session at PHOTON 2001

The status of and ongoing developments in the measurements and theoretical studies of the structure of the photon have been presented at the PHOTON 2001 conference in Ascona. The results presented in the structure function session are briefly summarised.Comment: Invited talk at the International Conference on the Structure and Interactions of the Photon, including the 14th International Workshop on Photon-Photon Collisions, Ascona, Switzerland, 2-7 September, 2001, 8 pages, 5 figure

On the combination of correlated estimates of a physics observable

The combination of a number of correlated estimates of a given observable is frequently performed using the Best Linear Unbiased Estimate (BLUE) method. Most features of such a combination can already be seen by analysing the special case of a pair of estimates from two correlated estimators of the observable. Two important parameters of this combination are the weight of the less precise estimate and the ratio of uncertainties of the combined result and the more precise estimate. Derivatives of these quantities are derived with respect to the correlation and the ratio of uncertainties of the two estimates. The impact of using either absolute or relative uncertainties in the BLUE combination is investigated on a number of examples including Peelle's Pertinent Puzzle. Using an example, a critical assessment is performed of suggested methods to deal with the fact that both the correlation and the ratio of uncertainties of a pair of estimates are typically only known with some uncertainty. Finally, a proposal is made to decide on the usefulness of a combination and to perform it. The proposal is based on possible improvements with respect to the most precise estimate by including additional estimates. This procedure can be applied to the general case of several observables.Comment: 22 pages, 7 figures, Version accepted by EPJ

Experimental Results on Two-Photon Physics from LEP

This review covers selected results from the LEP experiments on the structure of quasi-real and virtual photons. The topics discussed are the total hadronic cross-section for photon-photon scattering, hadron production, jet cross-sections, heavy quark production for photon-photon scattering, photon structure functions, and cross-sections for the exchange of two virtual photons.Comment: 13 pages, 11 figures, to appear in Proceedings of the Ringberg Workshop 'New Trends in HERA Physics' 1999, May 30 - June 4, 199

Experimental Review of Photon Structure Function Data

The present knowledge of the structure of the photon is presented based on results obtained by measurements of photon structure functions at e+e- collider. Results are presented both for the QED structure of the photon as well as for the hadronic structure, where the data are also compared to recent parametrisations of the hadronic structure function F2gamma(x,Q^2). Prospects of future photon structure function measurements, especially at an International Linear Collider are outlined.Comment: 9 pages, 8 figures, Contribution to the Photon09 Conferenc

QCD results from the LHC

A selection of results from the 2010 data taking period of the ATLAS and CMS experiments at the LHC at a proton-proton centre-of-mass energy of 7 TeV is presented. These results comprise differential jet cross sections for varying jet multiplicities, the investigation of properties of large rapidity gaps spanned by a dijet system, the production of heavy gauge bosons together with jets, and finally the investigations of properties of top quark pair production.Comment: 12 pages, 21 figures, to appear in the proceedings of the "Ringberg Workshop: New Trends in HERA Physics 2011", Ringberg Castle, Germany, 25-28 September, 201

First Measurement of the Photon Structure Function F_2,c^gamma

The first measurement of F_2,c^gamma is presented. At low x the measurement indicates a non-zero hadron-like component to F_2,c^gamma. At large x the measurement constitutes a test of perturbative QCD at next-to-leading order, with only m_c and alpha_s as free parameters, with a precision of O(40%).Comment: 6 pages, 6 figures, Invited talk given at the PHOTON 2000 Conference, Ambleside, UK, August 26-31, 2000, to appear in the Proceeding

The QED Structure of the Photon

Measurements of the QED structure of the photon based on the reaction ee --> ee \gamma(*)(P^2)\gamma*(Q^2) --> ee mumu are discussed. This review is an update of the discussion of the results on the QED structure of the photon presented in Refs.[1], and covers the published measurements of the photon structure functions F_2, F_A nd F_B and of the differential cross-section dsig/dx for the exchange of two virtual photons.Comment: Invited talk given at the 7th International Workshop on Deep Inelastic Scattering and QCD, April 19 to 23, 1999, Zeuthen, to appear in the proceedings. 8pages 4 figure

Two Photon Physics at a Future Linear Collider

Some general considerations on a future linear collider and selected topics of two photon physics measurements which can be performed at such a collider are presented. This review discusses the total photon-photon cross section, jet cross sections, structure functions, charm production, the BFKL Pomeron, $W$ pair production, and Higgs production.Comment: 17 pages, 16 figures, Invited talk at the Workshop on photon interactions and the photon structure, 10-13 September 1998, Lund, Schweden, to appear in the Proceeding