Measurement of Flux

1. Measurement of Flux

2. numu Flux measurement • strategy: CC QE exclusive reconstruction in off-axis detector.mu(MIP)+p(highly ionizing) • non-QE (1 pi)/QE measurement to get purity of sample • off-axis, can separate easily pi and kaon contributions • reference cross-section “well understood” • high efficiency in ND280 is important in order to minimize systematic error on efficiency • need a quantitative goal for this systematic

3. forming an error budget • make reference to disappearance measurement • current studies assumed 20% uncertainty in non-QE/QE ratio at superK • this was roughly equivalent to statistical

4. predicting far flux at SK • studies exist of how hadron producting impacts far/near ratio • effect is small in peak region (few-5% effect) • effect is larger in high energy tail (non-kaon part) • can we make reference to ORIGINAL hadron production uncertainties from the data? • can we use these studies to set requirements for hadron production EXPERIMENTS?

5. moving the detector? • technical impact on infrastructure is very large, so we should try to decide soon • another way to view this… moving the detector provides a good cross-check on the far prediction • can we cover “enough” angle by not moving? (detector transverse size) • can build on MC work by Konaka and colleagues

6. most extreme version: on-axis • is on-axis spectrum measurement useful for near/far ratio? • we know this is not helpful for K/pi for example • also, how do we measure spectrum on axis technically? (measurement, 14m deeper, etc…) • one counter argument… cross-sections are easier to understand, e.g. QE at high E flat(E) • counter-counter argument. backgrounds are larger to QE measurement

7. electron neutrino prediction • contributions: pi->mu, K+, K0 • 1.0:0.8:0.2 mu:K+:K0 in ND (without veto on final state particle). somewhat higher muon contribution in far detector • pi and Ks are well measured off-axis in ND • concerns: • no handle on neutral kaons (get from production experiments only) • concerned about robust pi->mu->nu chain? • accuracy needed is not high. • 10ev/5 yrs, 20% uncertainty allowed in far detector?? should do better

8. electron neutrino measurement in ND280 • technique : electron+proton final state • what does this measurement constrain? • ND sees a different mix of kaon and muon background • it’s a cross-check rather than a robust prediction, but want much better than 20% in ND • minor concern: we should check calculations of QE cross-section ratio for electron and muon neutrinos • 4% at 500 MeV, so probably no worries…

9. anti-neutrinos? • is it important to measure in near detector? • do we plan to ever run anti-neutrinos? don’t want a situation where ND PROHIBITS anti neutrino running • other reasons: some of HE tail is wrong sign. Wrong sign helps to constraint neutral kaons • technically, want to make sure we can add the capability “in a summer shutdown”

10. predicting backgrounds at SK

11. non-QE background at SK • this is a SEPARATE issue from measurement of the flux using QE and subtracting backgroun intrinsic to the near detector • here we want to PREDICT the non-QE background at SK using measurements at ND280

12. issues for non-QE background at SK • probably need to measure on oxygen since nuclear absorption is different • dominant non-QE background at SK is single pion • measure exclusive final state rates relative to QE rate at ND280 • differential cross-sections • two types of background. real muons and fake muons • fake muons (e.g., pions) are probably not a big issue at SK • are they a background to exclusive states at the near detector?

13. is off-axis detector enough? • do we need to move the detector to vary the spectrum (separate peak region from high energy tail)

14. what is the role of electron scattering? • in principle, very valuable information about nuclear effects with very high statistics • does it work? • probably need the option at least in reserve to have an oxygen rich ND280 part

15. pi0 background at superK • similar comments about carbon/oxygen difference • 2/3 of background at superK is resonant single pion • coherent production is estimated ~15%, but essentially unknown

16. a coherent program… • can measure in CC and NC both • in fully active detector, can measure in carbon • what does that tell us about oxygen? • there will at least be upper limits from K2K 1kT data • even CC coherent is a challenge to the detector. NC coherent is a very hard final state • it is enough to have CC in oxygen and carbon plus NC in carbon

17. resonance pi0 • need total and differential cross-sections • does NC pi0 resonant production require a variety of beam energies to do correctly? • CC allows you to deconvolute and CC can feed models of NC(Energy) • also, we need to temper severe requirements here with the knowledge that it can be measured directly at superK. • are there ND measurements that help reduce these systematics? such as backgrounds to pi0 at SK

18. search for single gamma • in principle, there are direct single photons • through radiative effectsany contribution from coherent nucleus? • ΔNγ • merits theoretical and experimental? study • probably are existing limits from old old experiments on this process

19. detector discussion

20. muon monitor

21. thoughts on muon monitor • position well established • need sensitivity to >~5 GeV muons • fluence (10^8 mu/spill/cm^2) requirements limit detector technology • Nakaya: “choose technology that is not too exotic” • ionization chamber for example (get input from MINOS) • Konaka: “diamond detector” • we should begin R&D here. beam tests at TRIUMF, K2K • can we afford only one detector technology? • what if one fails? • homework for Jan.: conceptual design and cost est. • TRIUMF/UK(?) for diamond; Kyoto/KEK for I.C.

22. on axis 280m detector

23. opening thoughts on on-axis 280m detector • physics need not as well established as other detectors • how is it not redundant with muon monitor? • how is it not redundant with 280m off axis? • Some ideas: • position of neutrino beam (independent of muons) • is high rate important during commissioning for establishing neutrino beam? (first check) • important to measure the spectrum for checking pion spectrum? (for example, Konaka matrix argument) • Need to understand soon • digging deep requires ¥ ¥ ¥ (building cost ~ volume)

24. more comments • neutrino position measurement is important for sensitivity to low energy pions • so need to identify low energy neutrinos • detector could be extremely simple • need to select energy; need to preserve rate in order to make day-by-day measurements of beam • can there be a simple structure to house it? • is it worth working very hard to try to be clever and save money, or does it cost most to be clever in the end? • how complicated a detector would be needed to implement the on-axis matrix method?

25. homework for on-axis detector • Ichikawa’s detector is costed • grid detector covering large area • should we cost a large area detector? • scaling from OPERA (magnetized) MRD? • anyone to study a more “sparse” design? • need more complete understanding of building costs with these design concepts in mind • i.e., for monolithic large detector, is there a floor load problem? • Konaka will study matrix method and which detector positions are needed

26. off-axis 280m detector

27. opening thoughts on off-axis 280m • physics need is crucial (yesterday’s discussion) • flux and neutrino interaction background • how will role change when 2km is present? • many detector concepts • integrated nuclear targets vs localized “external targets” • how can oxygen rich targets be made active? • gamma converter inside vs outside detector • outer muon detector design? magnetized? • test ideas in K2K beam or at NUMI • our job today: need to establish physics benchmarks to test these

28. magnetization and MRD • this is possibly independent from other physics studies • maybe good to design a detector that can be run magnetized or not • can magnetization replace some of the mass of the detector (the compromise would be that high energy muons are not measured as precisely) • what is the requirement for energy resolution at high muon energies? • what is the requirement for low energy muons (drives sampling) [this is a question for later]

29. what is the required size of the FGD? • total mass of the detector is driven by size of the fine-grained part (because MRD size scales as square of the transverse size of the FGD)

30. technical risk • how do we evaluate “new” technologies that are proposed for this detector? • e.g., “exotic” photosensors, stability of plastic scintillator in a water bath, active water detectors • specific questions • do we know the operational costs of VLPCs?(Clark wants to lead an R&D investigation on this)

31. physics signatures for study • quasi-elastics (proton tag, mu+p or e+p) • selection with high efficiency important? • unbiased efficiency as a function of angle. well-understood proton inefficiency as a function of momentum • requires understanding of both very soft and showering (interacting) protons? • opening angle also angle • the critical test: should be able to understand efficiency and background as a function of neutrino energy • is it important to identify by PID (rather than kinematically) the lepton to reject pions? • ability to observe additional activity as a inelastic tag • this leads to small systematic error on flux • configuration of absorber will change results… simulation!

32. physics signatures (cont’d) • resonant (and multi-pion) pi0 production in NC and CC • pi0 momentum and angle (unbiased) • additional activity… can the detector predict which events would give no additional activity in SuperK • ability to reconstruct events without tracks starting from the vertex (e.g., nu+n->nu+n+pi0) • systematic uncertainty in identifying fiducial volume • measurement of the pi0s from oxygen • possible techniques: statistical subtraction, event-by-event, active water target

33. coherent • full program to understand coherent rate requires NC and CC measurements • NC covered on previous page • CC: need to separate the two tracks (mu and pi) in the final state • role of magnetization? • effectiveness of vertex activity anti-tag • or kinematic subtraction?

34. measuring exclusive prcesses that produce backgrounds at SK • pion multiplicity in “DIS” (NSDIS “not so deep inelastic scattering) region • pi/p separation in DIS events

35. anti-neutrinos • QE in anti-neutrino? • vertex anti-tag • neutrons? (look along presumed direction?)

36. anything else? • study mu->e decay • ability to identify single gamma (discriminate from single electron or pi0)

37. a proposal and a thank you • thank you all for contributing to a very successful meeting • thank you to our hosts • a proposal:NUINT04 is 17-21 March at Gran Sasso or Rome?maybe we will hold a ND280 meeting at Gran Sasso March 16? • (also, afternoon December meeting at Stony Brook on or about December 12th)