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DIRT2 Meeting

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Some notes from Rik.

Action items:   the CERN group (Laura, Stephen, Adam) have brought us quite close to a nuclear initial state model.   They are going to see if they can turn on or patch the CFG.   Rik was supposed to touch base with Andy but hasn’t done it yet.  Aim to have the ingredients for a decision at the CERN meeting in two weeks?

We would like to harvest some knobs from Minoo’s insights, even if we aren’t literally able to harvest the entire model.   DIRT2 folks should think what to ask for and then reach out.

Minoo

Summarizing one perspective.   Previous work was an update of Rein Sehgal.   Her current work and upcoming results fully switches to the Rarita-Schwinger formalism (used by Hernandez et al., Lalakulich and Paschos, and most others in electron scattering) and away from the Feynman Kislinger Ravndal formalism used by Rein Sehgal.   One innovation going in is that previous neutrino implementations above have only had one or a few resonances in the Rarita-Schwinger formalism (Minoo will have all of them) while Rein-Sehgal has had almost all of them from the very beginning.    The former has better access to formfactor work and non-resonance contributions to the cross section, while the latter has been limited to simple dipoles and DIS kludges.

 

Hugh asks about Regge trajectory (from 80s) and VMD , discussion of the theory.    There is a discussion of a layer of detail that I missed because my connection was too flaky.

Extended discussion Kevin, Rik, Minoo of the feature (free nucleon)/(deuterium) that suggests the cross section in D is 20% higher than implied by free nucleons.   The plot is labeled “FSI” which might be throwing us off and making us think it is a surprise.   But on the other hand, our experience is that 2p2h models add 10-20% to the cross section in the QE region, with some scaling by A.   And(separately) the SRC component is 20% of the total in carbon and should be present and thought to have mild scaling with A.   In retrospect, both the direction nor the magnitude should have been guessed.   There is some thought on the electron side that the presence of a single nucleon brings strong effects, and the range between onset and saturation is quite narrow.   Kevin: "I agree with what Rik is saying about the two body contributions to pion production.  While we might first think about “suppression" (FSI-like) effects, it's natural to generalize what we've learned about the quasielastic-like process."


Chris, practical question, implemented a continuous parameter that goes between MK and RS.     Suggestion, are there features or parameters or insight that turn out to be particularly important in light of the electron scattering constraints.  88 parameters, but several slides note that a few knobs that stand out, but not yet a demo of it.   For DUNE and DIRT2 we can get by with something less than what experiments with data want.

A few of us can work directly with the Valencia or SuSA 2p2h code and remake the hadron tensors.   I'm not sure if we have the expertise to swap form factors without major effort, but it is not out of the question.

Adam

Slides:  not much difference between nue/numu from letpton mass effects.   Not much a surprise either.   Major difference between anumu/numu this is where we are going to work.

Chris.  This 3% uncertainty is a dangeresque simplification.   1-2 GeV, especially for. (Rik  2nd max, still not enough flux.  ) 2nd min.

Can attempt to parameterize the parameter spread vs. underlying model parameters.   Is this the way to “break” the ND sample statistical problems ?

Minoo mentioned PPP a couple times with specific reference to an early (the original?) implementation of the workaround in nuclear neutron something, including the context of two data sets with very different statistical power.

We have a couple weeks still to decide on a GENIE configuration.   The FarDet folks have a test sample that covers unrelated innovations they need.    We see the LFG is doing the NEUT thing.   The CERN group is going to see if they can turn on or back port the CFG feature too.   Can we get the ingredients together for a thumbs-up discussion at the CERN meeting ?

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