Fastsim Production

Systematics for W Physics

Strategy for fragmentation studies

We have entered the high luminosity/precision measurement regime for WW physics, thus the need of a very careful study of systematics in our measurements starts to urge.
The sources where most of the work is needed are quark fragmentation and FSI. The only way to study their effect in details is to have huge MC samples generated with different tunings of the fragmentation parameter (or different hadronisation schemes) and different reconnection models.
These samples can be used by all the WW teams (especially W mass, WW cross-section and TGC) and, more generally, by everybody in the collaboration.
The natural way to do this is using a fast detector simulation to produce an output that can be easily interfaced to different kind of analyses.
WWANA users can now find a working example of how to read the ntuple and fill accordingly the SKELANA common blocks in WWANA framework in the directory: /afs/cern.ch/delphi/tasks/wphysics/wwana/fastsim/. There is also a (slightly) modified version of the latest WWANA (v6.02) to properly run with FASTSIM outputs.

Ntuple structure

The ntuple is a CWN and consist of only one block with event and track information. Its structure is as follows:

NRUN Run number
NEVT Event number
NTRACK Total multiplicity
NCMUL Charged multiplicity
NRND Random seed number

PTRACKS(1,i) Px of track i, i=1:NTMUL
PTRACKS(2,i) Py of track i, i=1:NTMUL
PTRACKS(3,i) Pz of track i, i=1:NTMUL
PTRACKS(4,i) P of track i, i=1:NTMUL
PTRACKS(5,i) Charge of track i, i=1:NTMUL

CALE(1,i) E of associated e.m. shower i=1:NTMUL
CALE(2,i) theta of associated e.m. shower i=1:NTMUL
CALE(3,i) phi of associated e.m. shower i=1:NTMUL
CALH(1,i) E of associated hadronic shower i=1:NTMUL
CALH(2,i) theta of associated hadronic shower i=1:NTMUL
CALH(3,i) phi of associated hadronic shower i=1:NTMUL

IDMU(i) Muon identification word KMUID(1,i) i=1:NTMUL

VECW(1,i) Px of particle from W i=1:4
VECW(2,i) Py of particle from W i=1:4
VECW(3,i) Pz of particle from W i=1:4
VECW(4,i) E of particle from W i=1:4
VECW(5,i) Code of particle from W i=1:4
(The order is the following: fermion from W-, antifermion from W-, fermion from W+, antifermion from W+)

Fragmentation samples

The first high statistic samples have been produced (thanks to J.C. Marin). They contain 1M signal events each: besides the default one, we have produced one without tau polarization, and four varying independently two of the QCD parameters that affect the transverse shower development. The parameter settings have been taken from the reference Zeit. Phys. C73 (1996) 11-59 and have been varied of +/- two sigmas from their fitted values.
Here you have the details of the samples:


         Files              Runs                  Description

 Y13770.1-199       10001-10200    No tau polarisation
 Y13770.200-399     20001-20200    Default
 Y13770.400-599     30001-30200    Lambda_QCD +2sigma (PARJ(81)=.315)
 Y13770.600-799     40001-40200    Lambda_QCD -2sigma (PARJ(81)=.279)
 Y13770.800-999     50001-50200    sigma_Q +2sigma (PARJ(21)=.419)
 Y14122.1-200       60001-60200    sigma_Q -2sigma (PARJ(21)=.405)

The files can be staged by using the command delstage -f 1-3 ED5235.

Crete CR events with FASTSIM

The new FASTSIM samples of the Crete event files are now ready. The run and event number should now be available (except for the very first file due to a mistake). The string overlap for CR samples is stored in VECW(5,4). In the CR samples, the initial 4-fermions are not stored; instead, the W- is in VECW(i,1) and the W+ is in VECW(i,2).


         Files              Runs                  Description

 Y14122.201-220                        Jetset standard
 Y14122.221-230                        Jetset with CR (qqqq only)

Colour Reconnection samples

Fastsim samples of 500K WW->qqqq events with and without full CR (SK1 model) are available. The same comments for the Crete CR ntuple structure are valid.


         Files              Runs                  Description

 Y14122.331-430                        Default 
 Y14122.231-330                        Full CR (qqqq, SKI)

CR and BEcorrected samples

Fastsim samples of 200K WW->qqqq events with and without CR, with and without BE are available. The generated events are the same in all ntuples.


         Files                  Description                              PYTHIA settings

 Y01463.01-40           reference                      
 Y01463.41-80           SKI-standard                MSTP(115)=1, PARP(117)=100, standard PYRECO routine 
 Y01463.81-120          SKI-Sharka improved         MSTP(115)=1, PARP(117)=100, PYRECO routine by Sharka 
 Y01463.121-160         SKII                        MSTP(115)=2
 Y01463.161-200         BE3-in same W               MSTJ(51)=2, MSTJ(53)=1, MSTJ(54)=1, PARJ(92)=1.6, PARJ(93)=0.6 
 Y01463.201-240         BE3-all pions               MSTJ(51)=2, MSTJ(53)=0, MSTJ(54)=1, PARJ(92)=1.6, PARJ(93)=0.6
 Y01463.241-280         BE32-in same W              MSTJ(51)=2, MSTJ(53)=1, MSTJ(54)=2, PARJ(92)=1.6, PARJ(93)=0.6
 Y01463.281-320         BE32-all pions              MSTJ(51)=2, MSTJ(53)=0, MSTJ(54)=2, PARJ(92)=1.6, PARJ(93)=0.6

BE samples with new tuning

Fastsim samples of 200K WW->qqqq with the new PYTHIA tuning with BE are available. They contain the same events of the previous reference sample.


         Files                  Description                              PYTHIA settings

 Y01463.321-360         BE3-all pions              MSTJ(51)=1, MSTJ(53)=0, MSTJ(54)=2, PARJ(92)=1.73548, PARJ(93)=0.26133 
 Y01463.361-400         BE3-inside W               MSTJ(51)=1, MSTJ(53)=1, MSTJ(54)=2, PARJ(92)=1.73548, PARJ(93)=0.26133

The retuned fragmentation parameters have the following values:

parj(41) = 0.15711 ! lund a

parj(21) = 0.42303 ! sigma q

parj(81) = 0.32855 ! lambda_qcd

parj(82) = 1.82573 ! Q0

parj(42) = 0.58513 ! lund b

Last update 6 February 2001,

Alessandra and Roberto