[G12] g12 note: Normalization issue

[Lei Guo]

Following our discussion from Monday on the g12 normalization factor in all cross section calculation, I had a very productive discussion with MK today, together with what we discussed on Monday’s g12 meeting: I’d like to summarize what we have now.

There are really two things that are contributing, and nothing is really pointing to a specific “trigger inefficiency”.

1. Beam current dependent inefficiency. As Will has shown in his beam current dependent omega normalized yields, this is a small factor and sub-5% issue. But this needs to be verified since we weren’t sure the omega yields were extracted after applying any cuts on the photon multiplicity. That 5% could be just a photon multiplicity effect, or a real effect that we need to correct for.

2. Photon multiplicity. At g12 beam currents, there are non-negligible fraction of the data that has more than one photon in the same 2ns window. (There are also chances with three photons). This multiplicity could be both topology and beam energy dependent. So, this correction probably should not be a flat correction that’s good for all topoligies and all energies. But fortunately, deriving this is trivial and shouldn’t take too long.

3. Reconstruction/Simulation(in)efficiency. MK has done extensive studies using ppi+pi- events to study each track’s reconstruction efficiency in both real data and simulation. The method was look at the efficiency of proton, e.g., detection, if there is a missing proton. Do this for both data and MC, you will end up with a ratio that’s 1— ideally. However, he has a slightly inefficiency in data for each kind of tracks. This study was not dependent on the lepton trigger, and should be applicable for all g12 cross section measurements that involve the detection of charged triggers. However, there could be double counting there since the study was not done requiring only one good photon in the same time bucket.

But I think overall, we are pretty close to finish this issue. Let’s meet on Monday. And MK should be able to attend, especially since I might have misinterpreted his study.

See you!

Lei Guo
Assistant Professor
Physics Department
Florida International University
Miami, FL

email: leguo at fiu.edu <mailto:leguo at fiu.edu> or lguo at jlab.org
Office:305-348-0234

> On Feb 27, 2015, at 5:47 PM, Lei Guo <lguo at jlab.org> wrote:
> 
> HI, All,
> 
> We are still missing some mass (invariant and missing) plots of narrow states showing g12 mass resolutions. We have a lot of analyses going on, but not all have applied the g12 corrections ( eloss, beam energy, momentum). If you did, and has a narrow state in your data (such as Ks, Lambda, omega, Sigma), or a missing neutron/proton, could you send me a plot? When you send me that plot, could you also save the .C macro in root when you are making the plot, so I can combine plots from various people.
> 
> Thanks.
> 
> Lei Guo
> Assistant Professor
> Physics Department
> Florida International University
> Miami, FL
> 
> email: leguo at fiu.edu <mailto:leguo at fiu.edu> or lguo at jlab.org <mailto:lguo at jlab.org>
> Office:305-348-0234
> 

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