[Halld-physics] PYTHIA Lam0 K+ events

[Eugene Chudakov]

Concerning the discussion at the physics meeting today on the reason
for no gamma+p --> L0 K+ events from PYTHIA.

The cross section for a 2-body exclusive reaction is typically
dropping with energy. The L0K+ cross section was measured at 4 GeV of
about 100nb.

I looked at the PYTHIA-simulated 400k events in the beam energy range
of 3-12GeV. There were about 80 L0K+ events, mostly at low beam
energies (see the plot attached). There are some events in the
coherent peak region, of about 3e-5 of all interactions (about 3nb).
At 4 GeV the PYTHIA result is about 40nb.

Eugene
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pbeam_lamk+.pdf
Type: application/pdf
Size: 5893 bytes
Desc: Beam photon energy for the events with L0 K+ in the final
	state
Url : https://mailman.jlab.org/pipermail/halld-physics/attachments/20130325/4e68d76c/attachment.pdf