First Test of Evt Gen in ATHENA James

Contents § Current methodology for B-meson decay simulation in ATHENA § Integrating Evt. Gen

Current Methodology § Generate partonic events using PYTHIA § Passed to Pythia. BModule (M.

Partonic event PYTHIA B-hadrons Initialisation Pythia. BModule Any b’s? N Throw away Y N

Evt. Gen Interface § Evt. Gen has several advantages for B-decays § Amplitude approach

Pythia. BModule Any b’s ? N Y N Throw away Passes cuts? Y Evt.

First Attempt – angular distribution of B 0 d J/ ( + -)K 0*(K+

The plan for the next month § Investigate instabilities in results § Fix various

Conclusions § Evt. Gen can be operated smoothly from within ATHENA § The preliminary

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First Test of Evt. Gen in ATHENA § James R Catmore (Lancaster, UK) § § Maria Smizanska (Lancaster, UK) Malte Muller (University College London, UK)

Contents § Current methodology for B-meson decay simulation in ATHENA § Integrating Evt. Gen into ATHENA § First results

Current Methodology § Generate partonic events using PYTHIA § Passed to Pythia. BModule (M. Smizanska) § Checked for b-quarks § If found, passed back to Pythia for hadronization ¨ Each b-event is repeatedly hadronized to save CPU time § Hadrons from PYTHIA checked for the desired mother particles § If found and if they pass the appropriate cuts, passed back to PYTHIA for decay § Results converted to Hep. MC format and displayed

Partonic event PYTHIA B-hadrons Initialisation Pythia. BModule Any b’s? N Throw away Y N Repeated hadronization Passes cuts? Y ASCII log Store. Gate Decayed Bhadrons HEPMC conversion

Evt. Gen Interface § Evt. Gen has several advantages for B-decays § Amplitude approach § Helicity amplitudes § ‘Nodal’ approach to decay tree - efficient § PYTHIA still needed for the hadronic event generation § Use an interface class “Evt. Decay” (adapted for ATHENA by Malte Muller) to decay B-mesons with Evt. Gen code § Instantiated within Pythia. BModule § DECAY. DEC and MY. DEC read in via ATHENA Job. Options

Partonic event PYTHIA B-hadrons Initialisation Pythia. BModule Any b’s? N Throw away Y N ASCII log Store. Gate Repeated hadronization Passes cuts? Y Decayed Bhadrons HEPMC conversion

Pythia. BModule Any b’s ? N Y N Throw away Passes cuts? Y Evt. Decay Evt. Gen Store. Gate Repeated hadronization HEPMC conversion ASCII log

First Attempt – angular distribution of B 0 d J/ ( + -)K 0*(K+ -) + J/ - B 0 d K 0* K+ -

Angles J/ K*

Results

The plan for the next month § Investigate instabilities in results § Fix various memory leaks § Develop code so that Evt. Gen can be invisibly operated within ATHENA following a single request from the user § Automatic generation of MY. DEC § CP violation studies?

Conclusions § Evt. Gen can be operated smoothly from within ATHENA § The preliminary results require investigation