Neutrino and Antineutrino Cross Sections at MiniBooNE

1. Neutrino and Antineutrino Cross Sections at MiniBooNE Sam Zeller Columbia University (for the MiniBooNE collaboration) NO-VE Workshop February 7, 2006 - our 1stn cross section results (CC +/QE) - future directions in MiniBooNE program

2. MiniBooNE is a  Oscillation Experiment • main goal: confirm or rule out e LSND results • search for nm → ne oscillations • not going to be showing • oscillation results • working hard on performing • a very careful e appearance • analysis … • you’ll have to stay tuned

3. MiniBooNE is a dynamic experiment updating  is important MiniBooNE On the Way • while designed for  ne oscillation search … * well-suited for low E  cross section physics - useful to the community - important for oscillation analysis - will tell you about * plus some new opportunities (mention at end) - antineutrino data! (big change for us)

4. Previous Measurements • most of present low energy n knowledge • comes from bubble chamber exps • early experiments at ANL, BNL, • FNAL, CERN, Serpukhov, etc. GGM BNL FNAL • 20-100% errors due to: • - low statistics (100’s of events) • - uncertainties in n flux • in addition to large errors, results • often conflicting (some care in interpreting) • data useful to constrain our MCs • idea of caliber of past data …

5. predictions from NUANCE • - MC which MBooNE uses • - open source code • - supported & maintained • by D. Casper (UC Irvine) • - standard inputs • (common ingredients - osc exps) • - Smith-Moniz Fermi Gas • - Rein-Sehgal 1 • - Bodek-Yang DIS Low Energy  Cross Sections MINOS, NuMI K2K, NOvA MiniBooNE, T2K Super-K atmospheric n

6. Low Energy  Cross Sections • imperative to precisely • predict signal & bkgd rates • for future oscillation exps • - will be more sensitive • to sources of syst error • - nuclear targets! • (most past data on H2, D2) • further motivates need for • new measurements • new data adding new info; • revealing interesting features • K2K, NOMAD, MiniBooNE MINOS, NuMI K2K, NOvA MiniBooNE, T2K Super-K atmospheric n

7. MiniBooNE Beamline • >700,000 contained  events • providing a valuable sample • to study low E  cross sections FNAL 8 GeV Booster decay region: p  mnm , K→mnm “LMC” measure K flux in-situ MiniBooNE detector (CH2) magnetic horn: meson focusing 450 m earth berm: n movable absorber: stops muons, undecayed mesons magnetic focusing horn

8.  Flux at MiniBooNE Detector • incident on detector: high purity beam (>99% flavor) •  mainly from p+ m+ nm •  production constrained by • global  data & E910 … • - eventually HARP • - really advance knowledge • of low E hadroproduction • (see Gibin’s talk) PRELIMINARY MC predicted  energy spectrum

9.  Flux at MiniBooNE Detector • - <E>MBooNE ~ 0.7 GeV • - well-suited for low energy •  cross section studies • - small tail; enjoy smaller • backgrounds from higher • multiplicity  interactions • - complementary to other •  experiments • <EK2K> ~ 1.3 GeV • <ENuMI > ~ 10 GeV • <ENOMAD > ~ 24 GeV PRELIMINARY MC predicted  energy spectrum

10. demonstrate understanding of 79% of events before analyzing e (<1% of total) Event Fractions at MiniBooNE this flux spectrum dictates what type of  interactions we see … - 48% CC QE - 31% CC p+ - 8% NC p0 - 5% CC p0 - 3% NC p+/- - 4% multi-p - 1% NC elastic MiniBooNE flux-averaged event compositions (NTANK>200, NVETO<6)

11. Quasi-Elastic Scattering Why important? nm n → m- p • nm QE s necessary to accurately predict • signal rates in oscillation experiments (including our own) • * ne QE are main signal for nm ne appearance searches; • have similar kinematics &  • channel used as “golden mode” to normalize other • cross section samples - lots of events, well known (common practice that we will also adopt for now)

12. Quasi-Elastic Scattering nm n → m- p • highest statistics • ~2500 events • low E data on D2

13. new information already • coming in (NOMAD, 12C) (R. Petti, NuInt05) Quasi-Elastic Scattering nm n → m- p

14. Quasi-Elastic Scattering nm n → m- p • MiniBooNE: • - 12C (valuable for osc exps) • - this analysis: 60k events (3.2x1020 POT) • (already more data than all previous exps combined) • - can select 86% pure QE sample

15. forward muons corresponds to low Q2 … MiniBooNE QE Data (J. Monroe) • most copious events at MiniBooNE • also simplest: two body kinematics measure visible E and qm from mostly Čerenkov (m) + some scintillation light (p) nm n → m- p

16. MiniBooNE QE Data • similar effect seen by K2K • working on understanding • these features in our data … • to improve data, MC agreement • performing shape fits for: • (J. Monroe) • - axial form factor (MA) & • - nuclear model pars (EB,pF) • incorporating new nuclear models(R. Tayloe) • (that are constrained by modern electron scattering data) Q2 = m2 - 2E(E-pcos)

17. 2MpEm – mm2 EnQE = 2(Mp-Em+pmcosm) MiniBooNE QE Data • making use of E,  … • energy distribution that • will be used for CC +/QE • cross section measurement • next, numerator (CC +) … (J. Monroe)

18. + A A CC 1p+ Production resonant + production (dominant) coherent + production • forward emitted  • low Q2

19. CC 1p+ Production resonant + production (dominant) coherent + production

20. (K2K, hep-ex/0506008) • K2K: 1st search for coh + prod at low E • somewhat surprising results … • see no evidence for coh + production! CC 1p+ Production resonant + production (dominant) coherent + production

21. + A A CC 1p+ Production resonant + production (dominant) coherent + production • forward emitted  • low Q2 • MiniBooNE:- inclusive measurement, CH2 • - this analysis: 40k events (3.2x1020 POT) • (5x more than previous bubble chamber data combined)

22. CC p+ Production • Why important? • poses largest background to  QE samples • (large s & p+ can be absorbed in nucleus) • useful for understanding D production in CH2 • (D→ N g a background to nm→ne search) • possibility for CC p+ oscillation search • useful in understanding our event reconstruction nm N → m- N p+

23. e- m- nm e +e+ e+ p+ m+ • expect  to have • shorter lifetime from • m capture (8% in12C) • will also make use • of this later t =2070 ±16 ns t = 2242 ± 17 ns (M. Wascko) MiniBooNE CC p+ Selection • very simple selection: • - events with 2 decay electrons • - unique, results in 84% purity

24. measure Čerenkov light from muon (to avoid light from +) seelarger deficit in forward  (low Q2) than in QE data MiniBooNE CC + Reconstruction (M. Wascko)

25. MiniBooNE CC p+ Data 2MpEm – mm2 + (m2-Mp2)“EnQE” = 2(Mp-Em+pmcosQm) (M. Wascko) • use 2 body (QE) kinematics • assume  in final state • (instead of p in QE case) • energy distribution that • will be used for CC +/QE • cross section measurement

26. MiniBooNE CC +/QE Ratio (J. Monroe, M. Wascko) • efficiency corrected CC +/QE •  ratio meas on CH2 • eff corrections from MC • ample statistics  can perform • a binned measurement • current systematics estimate: • - light propagation in oil: ~20% • -  cross sections: ~15% • - energy scale: ~10% • - statistics: ~5% first measurement of this cross section ratio on a nuclear target at low energy!

27. MC error band from external  data constraints MiniBooNE CC + Cross Section • multiplying measured CC +/QE ratio by QE  prediction • (QE with MA=1.03 GeV, BBA non-dipole vector form factors) • ~25% lower than prediction, but within errors (J. Monroe, M. Wascko)

28. Plausible Interpretation • since MiniBooNE 1st meas • on nuclear target at these E’s • at 1st glance, one might think • this is pointing to a potential • problem with nuclear corrs

29. BNL ANL Plausible Interpretation • since MiniBooNE 1st meas • on nuclear target at these E’s • at 1st glance, one might think • this is pointing to a potential • problem with nuclear corrs • but free nucleon ’s disagree! • MC prediction splits difference • MiniBooNE results more consistent with ANL than BNL • - new data helping to decide between 2 disparate  meas • - once final, type of info that can feed back into open source MC

30. new antineutrino data! • observing  events from NuMI • coming soon: new fine-grained • new detector to this beamline • (comparisons to MiniBooNEwill • be interesting) New  Directions at MiniBooNE

31. goals are two-fold: • - check LSND nm→ ne signal • (longer program, not yet approved) • - measure n cross sections • - systematic check of  analyses • - low Q2 investigations • - coherent production MiniBooNE Antineutrino Running • just started antineutrino running (January 19th) • - ~1,000  events/week • - will have world’s largest low E  data set in a few weeks! 1st MiniBooNE antineutrino event

32. MiniBooNE will make world’s • 1st meas of ns in this E range • - expect ~10k nm QE • in 1 year (after cuts) • provide valuable input for • future CP violation searches • P(nm→ ne) ≠ P( nm→ ne) • prefer not to rely on extrapolation of • models into regions where no data Need for  Measurements • ns data even less abundant

33. Added Difficulty with  Beams • contending with “wrong sign” backgrounds ( in  beam) • - MiniBooNE beam is no exception … • in neutrino mode, • antineutrinos are ~2% • of total events

34. “ -enhanced beam” • need a way to constrain •  backgrounds in  data • Čerenkov detectors • cannot distinguish • , + event-by-event • (no magnetic field) Added Difficulty with  Beams • contending with “wrong sign” backgrounds ( in  beam) • - MiniBooNE beam is no exception … • in antineutrino mode, • neutrinos are ~30% • of total events

35. 1st and most powerful … • makes use of fact that QE n & n • have different angular distributions • large angle QE’s as means of • measuring  content in n data • (“poor man’s sign-selection”) Constraining n Backgrounds in n Data • needed to be more clever • developed several novel techniques to measure from data

36. QE angular distributions provide best “wrong-sign” • constraint, but also … 7% constraint 2. add’l constraint from CC p+ events in n mode data (come entirely from n interactions as n ’s produce a p_in final state) - higher E constraint 15% constraint 3.also muon lifetimes (m vs. m+ to distinguish n vs. n ) - m and m+ have different lifetimes due to m capture probability in oil - not as precise a constraint, but indep of kinematics & recon 30% constraint Three Independent Constraints redundant checks → allows precise antineutrino s measurements (once have a handle on  backgrounds)

37. Antineutrino  Measurements • can add new info by mere fact that  scattering is different  QE  QE different shape & axial contribution d dQ2 difference isolates interference term - directly  to axial FF

38. latest K2K results say this peak will be missing: very apparent in  data Antineutrino  Measurements • can add new info by mere fact that  scattering is different  NC 0  NC 0 • 40% is coherent production • “enhanced” coherent sample • 20% is coherent production

39. Can Detect ’s from NuMI ! • neighbor’s beam • first off-axis • neutrino beam! (A. Aquilar-Arevalo) • ~10,000 n events so far • 100’s of ne events (calibration) • also opened up possibility to • use this sample for meas • (slightly diff beam spectrum) • MINOS also sees MiniBooNE • neutrinos in their detector NuMI n events in MiniBooNE detector

40. SciBooNE (E954) • new Int’l collaboration • couple well-understood, fine-grained • detector with high rate beam • - unique, low risk opportunity

41. - excellent final state resolution - improve on MiniBooNE studies SciBooNE (E954) • new Int’l collaboration • couple well-understood, fine-grained • detector with high rate beam • - unique, low risk opportunity

42. - excellent final state resolution - improve on MiniBooNE studies SciBooNE (E954) • new Int’l collaboration • couple well-understood, fine-grained • detector with high rate beam • - unique, low risk opportunity -  measurements for T2K • just received Stage 1 approval (Dec ‘05) • rapid schedule: begin data taking this Fall • www-sciboone.fnal.gov

43.  cross sections  flux Conclusions • collected > 700k neutrino (> 1k antineutrino) events (7 x 1020 POT) • - amassed the world’s largest  sample in 1 GeV range • - already an order of magnitude more data than previous • bubble chamber based measurements • - part of effort to help improve our current understanding of low E  • - 1st results on MiniBooNE CC +/QE cross section • coming soon … • -  CC QE cross section results • - NC 0 cross sections - HARP results (8 GeV, Be, thick target) • stay tuned for  e oscillation results