Re: [fluka-discuss]: eta(550) decays

From: paola sala <paola.sala_at_cern.ch>
Date: Wed, 6 Nov 2013 10:15:13 +0100

Hi Joe
I have a naive question: experimentally, how can you be sure that those
etas are produced by neutrons and not by kaons?
Paola
On 11/05/2013 10:44 PM, Joseph Comfort wrote:
> 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 Wed Nov 06 2013 - 11:10:02 CET