montecarlo

The The KORALW event generator, version 1.51 [], is used to produce W pair events. These events are weighted by the O(a)  correction to the double-resonant W-pair process using YFSWW3 program version 1.16 []. Within KORALW all four-fermion (4-f) diagrams producing WW-like final states are computed, including Cabbibo suppressed decay modes, using the fixed-width scheme for W and Z propagators. The JETSET 7.4 [] or PYTHIA 6.1 [] packages are used for the hadronisation of quarks in the final states. Their parameters are tuned at the Z with a selection of q[`q] events with anti b quark tagging. Colour reconnection and Bose-Einstein final state interactions are not included. A sample of 106 4-f events to all decay modes was generated with KORALW at each value of a set of eight CM energies ranging from 182.7 to 206.5 GeV []. The W mass was set to 80.35 GeV/c2 and the width taken from Standard Model (SM) predictions to be 2.094 GeV/c2. These samples are used as reference samples for fitting to the data in the reweighting procedure (see section ), as well as for the study of detector systematic errors. Additional samples of 200k events to all decay modes were generated with W masses up to 0.5 GeV/c2  and separately with W widths up to 0.6 GeV/c2 different from the reference sample, for checking the stability of the results. Also, an independent sample of 500k W pair events was generated at each CM energy with KORALW restricted to the doubly resonant CC03 diagrams []. This sample is used to train the neural networks and parametrise the corrections used in the kinematic fitting.

For studies of the systematic errors from fragmentation in W decays, 106 W pair events generated with KORALW were hadronised using JETSET. To suppress statistical fluctuations in the comparison between the hadronisation models, these events were hadronised using JETSET, HERWIG 6.2 [] and ARIADNE 4.10 [] and then processed through the full detector simulation. Similarly, fully simulated samples of 100k to 500k events, generated with KORALW, were hadronised with modified versions of JETSET [] [], HERWIG and ARIADNE containing various implementations of colour reconnection, to assess the influence of final state interactions between W decay products on the mass and width. Samples of KORALW events were also re-hadronised with a version of JETSET that includes Bose Einstein correlations [], to determine their influence on the W mass and width measurements.

Fully simulated samples of events of at least hundred times the data luminosity were generated for all background processes at each CM energy. The e+e-® q[`q](g) events were generated with KKMC version 4.14 [] with hadronization performed by PYTHIA and including the final state radiation in the parton shower step. Interference between initial and final state was not taken into account. Events from ZZ-like final states were generated using PYTHIA (NC08 diagrams), but particular care was taken to avoid double counting of ZZ events already included in the signal generation as WW-like events (i.e. u[`u]d[`d],m+ m-n[`(n)],..). The same applies to Zee final states, generated with a 12 GeV/c2 minimum mass for the Z system. Possible double counting of e+e-n[`(n)] events was handled in a similar way. Two-photon (gg) reactions into leptons and hadrons were simulated with the PHOT02 [], PYTHIA and HERWIG generators but no events survived the selection cuts in the q[`q]q[`q] and lnq[`q] channels. Dilepton final states were simulated using KKMC for tt(g) and mm(g) and BHWIDE 1.01 [] for ee(g) events.

[ht]

[kk] Overview of the number of simulated events generated for each process type at each centre-of-mass energies (in unit of 1000 events) and corresponding data integrated luminosity. Events generated from the same 4f (2f) samples are shown in italics

-1.5mmyear 1997 1998 1999 1999 1999 1999 2000 2000
-1.5mmEnergy (GeV) 182.655 188.628 191.584 195.519 199.516 201.625 204.860 206.530
-1.5mmLuminosity and 56.812 174.209 28.931 79.857 86.277 41.893 81.409 133.212
-1.5mmtotal error () ±0.312 ±0.766 ±0.145±0.359 ±0.380 ±0.201 ±0.383 ±0.599
-1.5mm4f- signal 1000 1000 1000 1000 1000 1000 1000 1000
-1.5mm4f-JETSET 1000 1000
-1.5mm4f-HERWIG 1000 1000
-1.5mm4f-ARIADNE 1000 1000
-1.5mmZZ (NC08) 200 200 200 200 200 200 200 200
-1.5mmZee ( > 12 GeV/c2)200 200 200 200 200 200 200 200
-1.5mme+e-1000 3000 1000 3000 3000 1000 3000 3200
-1.5mmm+ m-300 300 300 350 300 300 300 300
-1.5mmt+ t-100 100 100 100 100 100 100 100
-1.5mmq[`q]2000 1000 2000 2000 2000 2000 2000 1000
-1.5mmq[`q]-JETSET 1000 1000
-1.5mmq[`q]-HERWIG 1000 1000
-1.5mmq[`q]-ARIADNE 250 250
-1.5mmq[`q]-BE32 150 150
-1.5mmgg®e+e- 200 600 100 300 300 200 300 500
-1.5mmgg®m+ m- 200 600 100 300 300 200 300 500
-1.5mmgg®t+ t- 200 600 100 300 300 200 300 500
-1.5mmgg® hadrons
-1.5mmun-tagged 1000 3000 500 1500 1500 500 1500 2500
-1.5mmtagged 500 1000 500 1000 1000 500 1000 1000
-1.5mmCC03-JETSET 500500500500500500500500
-1.5mmCR model SKI 500 500 500 500 500500500500
-1.5mmCR model SKII 500500
-1.5mmCR model SKII' 500500
-1.5mmCR model GAL 150 150 100 100 150 100 100 150
-1.5mmBE32 2 models 150 150 100 100 150 100 100 150
-1.5mmCC03-ARIADNE 500500500500500500500500
-1.5mmCR model AR2500500500500500500500500
-1.5mmCC03-HERWIG 500500500500500500500500
-1.5mmCR model 11%500500500500500500500500

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On 10 Nov 2004, 16:45.