Rare/other processes working group summary Motto: 100% uncertainties - - PowerPoint PPT Presentation

“Rare/other” processes working group summary

Motto: “100% uncertainties sound conservative, but...” Jeremy Wolcott Tufts University “Nu-Print” Neutrino Cross Section Strategy Workshop March 14, 2018

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What are we considering?

• Any reactions not covered by the other working groups

– NC – νe, ντ CC – Strange production (K, Λ, Σ, ...) – Truly “rare” things:

• Coherent/diffractive processes
• ν+e elastic scattering
• Exotic stuff (e.g. “explanations” for MiniBooNE excess)
• Corrections/subdominant channels to more common processes

– Final-state radiation in CC reactions – Processes with radiative delta resonance decays (Δ+→p γ, etc.)

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What are the physics needs?

• Backgrounds for oscillation physics

– NC π channels (π± for νμ disapp., π0 for νe app.) – Single-photon- or π0-producing CC reactions (νe app.)

• Signals for oscillation physics

– νe appearance – NC inelastic processes for sterile searches – Rare subprocesses of νμ CC (e.g. ν → Λ CCQE)

• Backgrounds for BSM physics searches

– Strange production (particularly kaons)

• Beam characterization

– ν+e elastic, CC coherent?

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Evaluating the prospects

Model quality Are models available? Are there known flaws? Is there active work underway? Constraint quality Are there measurements? Of what quality/applicability? If not, are measurements plausible? [All opinions the author's, discussion members may (will?) disagree]

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Evaluating the prospects

How much should we be panicking?

Are our models for some important process poor or missing? Do we have data constraints? [All opinions the author's, discussion members may (will?) disagree]

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νe CC (lepton non-universality)

Good quality models Good quality measurements

DIS/SIS form factors:

• No theory work??
• Challenging to measure (bknds).

NOvA measurement in progress should probe SIS 1π form factors:

• No theory work. Could maybe

treat analogously to 0π??

• NOvA measurement in progress

0π form factors:

• Detailed phenom. investigation of

possible univ. violation exists

• Several measurements

(MINERvA, T2K; NOvA ongoing), but no prospects of stringent non- universality constraints Radiative effects:

• Theory tractable for real radiation; virtual radiation

challenging but not impossible?

• All measurements challenging

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• Panic level: elevated

– Critical, major oscillation signal channel – Phenom. work (Day-McF) suggests form factor differences under control for CCQE (~few %

unc.); currently no guidance for higher W

– Real radiation possible signal confusion for T2K (less worry for calo. style detectors) – Virtual radiation (box diagrams) challenging to calculate, ~few % effects for νe app. – Impossible to produce stringent data constraints without extremely well characterized νe flux (i.e.

muon source)

νe CC (lepton non-universality)

One instance of a “McFarland Bicycle Diagram” for virtual (internal) photon radiation in CCQE

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• Panic level: elevated

– Critical, major oscillation signal channel – Phenom. work (Day-McF) suggests form factor differences under control for CCQE (~few %

unc.); currently no guidance for higher W

– Real radiation possible signal confusion for T2K (less worry for calo. style detectors) – Virtual radiation (box diagrams) challenging to calculate, ~few % effects for νe app. – Impossible to produce stringent data constraints without extremely well characterized νe flux (i.e.

muon source)

νe CC (lepton non-universality)

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Neutral current

Good quality models Good quality measurements

NC DIS/SIS:

• formalism “should” work?

(but shadowing, EMC...)

• M. Kabirnezhad model

improvements

• no modern measurements

NC 1π:

• currently using Rein-Sehgal :-\
• T2K (π±), NOvA (π0)

measurements in progress; MiniBooNE (π0) NC 0π:

• Simplistic generator models. No
• npnh. (Better available? → ab

initio work)

• T2K measurement. (2-body??)

MiniBooNE attempt?

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Neutral current

• Panic level: high

– Important backgrounds for CC ν oscillation – Important signal for NC ν oscillation – Generator models very basic, little (no) current effort to improve? – Some effort from model-building side (e.g.: Lovato et al., 1711.02047) – Measurements in progress (T2K, NOvA)

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Strange production

Good quality models Good quality measurements

Single kaon production:

• Good quality model (Athar)
• Hard to measure (narrow energy

region where dominates) Associated strange production:

• Models available. FSI critical.
• Multiple MINERvA measurements

(CC, NC) ν → Λ CCQE:

• Model exists, almost in GENIE
• Challenging to measure.

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• Panic level: guarded

– Kaon measurements indicate models ~ok for now.

Further measurements challenging

– Lambda CCQE modeled but hard to measure, but

unclear how important

Strange production

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“Standard candle” processes

Good quality models Good quality measurements

ν + e elastic:

• Tree level prediction exact.

Radiative corrections improvable.

• MINERvA measurement. NOvA

in progress Coherent pion:

• Microscopic model only works at

low Eν, PCAC otherwise

• MINERvA & T2K measurements on

multiple targets (CC), NOvA (NC)

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• Panic level: low

– Detailed COH measurements. Rate is low. – DFR on H probably not important bknd for osc. (can

reject)

– ν + e path forward understood

“Standard candle” processes

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• Panic level: unsure

– Potential backgrounds for νe appearance – Disparate models, generally no generator implementations (radiative Δ decay an

exception)

– Unclear to what degree current νe ID techniques are susceptible – Difficult to measure (photon backgrounds from “conventional” sources – π0s, etc.) – “The #!$@ everywhere is also the problem” --anonymous

Other photon production

? ? ? ?

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Summary of this summary talk

• Fairly wide gulf between theory, generator

implementation, and measurements in many respects

• Most important (?) priorities for current and near-

future measurements:

– Neutral current (esp. inelastic channels) – Radiative effects in CC reactions (where possible)

• Serious thought on possible photon backgrounds

(and work on generator implementations) desirable