The LEP QCD Annihilations Working Group homepage

These webpages are under constant revision. Some parts are password protected.

Next meeting

We are currently calling short-notice telephone conferences (+41 22 767 7000) advertised on the LEP QCD mailing list in order to complete our combinations paper.

Minutes of annihilations group meetings

are available here. (These are password protected.)

What do we want?

• Many QCD measurements from LEP 1.5 and LEP 2 are statistics limited, in contrast to the situation at LEP 1. We might thus hope to gain some reduction of the total errors of QCD measurements by combining the results from the four LEP experiments. This is important for studies of the running of the strong coupling constant with energy-scale.
• Some fraction of the systematic uncertainties are correlated between the four LEP experiments. Unfortunately, the precise degree of correlation is hard to estimate, but the correlations are important for any meaningful combination of results.
• The largest correlated uncertainty is that associated with the missing higher orders in the theoretical predictions used to extract the strong coupling. It is also important for combination or comparison that the experiments use comparable theory predictions, and label each theory variant in the same way. This has been an important part of the work of the group.
• We provide files of our results in a tabular format; here is an example.

What have we done?

• Our current combination results are presented here.
• Our most recent work has concerned more direct combinations of the strong coupling constant values determined from event shapes. Results have been provided twice yearly since the Summer 2002 conferences; an example plot shows the running of the coupling as derived from event shape data. A note describing this work is in preparation; please contact us for details. This work kas been refined and improved by a systematic investigation of the theoretical input used in the strong coupling extractions from the different experiments. This leads to both a better understanding and higher correlation (through a common treatment) of the theoretical uncertainties.
• We have produced a paper, pdf format of the estimation of the theoretical uncertainties.
• A presentation of our results to the LEP Jamboree on the 6th March 2003 is available in pdf and Powerpoint.
• Our initial studies concentrated on the moments of event shape variables. This work was presented to the LEPC in a talk and was documented in an internal note in the four collaborations.

Who are we?

• We are people from the four LEP experiments interested in QCD at in annihilation events at LEP and in QCD at LEP 2 in particular.
• The LEP QCD annihilations WG is open to everybody interested in the subject.

Miscellaneous

• There is a (closed) majordomo mailing list for the LEP QCD WG lep-qcd-wg@listbox.cern.ch. List members can see a web-based archive of the list here. Your CERN mailserver username and password are required.

Last modified: 27 February 2004