Hi Alfredo,
Our experiment (KOTO) has a mixture of neutral beams (K0L, n, gamma),
generally spread over a range of a few GeV and below, collimated from a
production target.
Specific cases I am testing at the moment include pi- on LH2 and
neutrons on Al, both at 3 GeV. I get nice pi0 and eta peaks, with a
sensible ratio, for pi-/LH2. I get pi0s, but no etas at all (exactly
zero), for n/Al, even after >10^8 beam particles and over 13,000 pi0s.
The meson vertex is in the suitably thin target, and the particle is
identified from the 2-gamma decay mode.
The experiment is set to identify pi0s from K0Ls. However, a nasty BG
mode comes from "halo" neutrons that hit some charged-particle veto
detectors in front of the main photon detectors, producing etas.
Unfortunately, the etas can reconstruct to look like legitimate pi0s.
This BG was identified in an earlier version of the experiment, and
studied by inserting an Al target in the beam path. A figure from a
thesis is attached. The MC was produced from a Geant3-based code, and
the normalization matches very well. But the current Fluka is not
producing etas for this case.
Most eta decay modes will get vetoed in the detector. Even without
considering normalization, we need to study where etas are produced and,
preferably, bias the decay to the 2-gamma mode.
It is very clear to me, as you indicated, that major revisions to the
code would be a huge task. I am instead looking for places where I can
more simply tap in to determine the eta birth location and its decay
mode. Being a Fortran person, I would prefer to stay with Fluka if
possible.
Thank you,
Joe Comfort
Received on Tue Nov 05 2013 - 23:43:41 CET