Double Regge Exchange Meeting

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Location

Jefferson Lab

  • 10:00am: F326/327
Bluejeans: https://bluejeans.com/776007194

Google Group

gluex-jpac-double-regge-discussion@googlegroups.com

March 30

Colin presented updated beam asymmetries that corrected a sign issue. He also showed beam asymmetries in bins of recoil particles (eta Delta++ or pi- Delta++ mass). The results show the the beam asymmetry is independent of these variables. Lawrence presented beam asymmetries for uncertainties that were calculated from bootstrapping. For both analyses, we had a long discussion on why the beam asymmetry is ~0.5 and not 1. For the experimenters, we were tasked with looking at potential backgrounds and playing around with some cuts, such as the eta pi mass. The theorists were tasked with thinking about why the asymmetry was saturating at 0.5, and if there is a good physics reason behind it.

March 16

Minutes:

  • Colin showed asymmetries as a function of t_eta and t_pi-. There appears to be an issue with the sign based off the expectations. Eg t_eta is negative, but should be positive. Colin check his fit function and extraction of the asymmetry with Lawrence and they are using the same function and the phi0 offsets are nearly identical. Therefore, the extraction method does not appear to cause the sign issue. In discussion with Adam and Vincent, the sign may need to be flipped if one has a Delta++ as the recoiling particle. Adam and Vincent will look into this more offline.
  • Lawrence showed asymmetries as a function of t_eta and t_pi0. They agree with what is to be expected.
  • Vincent showed some slides going over the theory aspects of having 3 particle final states. This needs to be studied more for the kinematics where double Regge production is dominant (high eta pi masses). Hopefully this will give a reason for the sign difference between having a recoil proton and Delta++. It may be that the sign of the asymmetry depends on the product of naturality between the two exchange particles. If this is the case, then having a Delta++ at the bottom vertex would cause a sign flip. This has not been accounted for in Colin's asymmetries.

March 2020 Agenda

  • 9:30: Colin - γ p -> η π- Δ++
  • 10:00: Lawrence - γ p -> η π0 p
  • 10:30: Vincent - [1]
  • 11:00: Discussion
    • Study secondary exchange vertex. If η is on the upper vetex, look at yields as a function of s_{πp} and t_{p}. Do we see the features of Reggeon exchange at this vertex?
    • Calculate beam asymmetries as a function of low t_{π} and t_{η}. Can make some general cuts on the kinematics to reduce potential backgrounds. For example, with a fast π, we can cut to make sure the remaining particles are slow/backwards.
    • Vincent and Lukasz will provide the amplitudes for us to fit to out data. Can we extract reasonable values for α?
    • Can a prediction be made for ηπ+n? Yes, can use this channel as a check.
    • Work on setting up a bi weekly (or monthly) meeting to keep things moving forward.

December 2019 Agenda

Action Items