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Sam Zeller, NO-VE Workshop, 02/07/06 1 Neutrino and Antineutrino Cross Sections at MiniBooNE Sam Zeller Columbia University (for the MiniBooNE collaboration) NO-VE Workshop February 7, 2006 - our 1 st cross section results (CC + /QE) - future directions in MiniBooNE program
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Sam Zeller, NO-VE Workshop, 02/07/06 2 MiniBooNE is a Oscillation Experiment main goal: confirm or rule out e LSND results search for → e oscillations not going to be showing oscillation results working hard on performing a very careful e appearance analysis … you’ll have to stay tuned
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Sam Zeller, NO-VE Workshop, 02/07/06 3 * 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) MiniBooNE On the Way MiniBooNE is a dynamic experiment while designed for e oscillation search … updating is important
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Sam Zeller, NO-VE Workshop, 02/07/06 4 Previous Measurements most of present low energy knowledge comes from bubble chamber exps early experiments at ANL, BNL, FNAL, CERN, Serpukhov, etc. 20-100% errors due to: - low statistics (100’s of events) - uncertainties in 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 … GGM BNL FNAL
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Sam Zeller, NO-VE Workshop, 02/07/06 5 Low Energy Cross Sections MINOS, NuMI K2K, NOvA MiniBooNE, T2K Super-K atmospheric 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
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Sam Zeller, NO-VE Workshop, 02/07/06 6 Low Energy Cross Sections MINOS, NuMI K2K, NOvA MiniBooNE, T2K Super-K atmospheric 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 H 2, D 2 ) further motivates need for new measurements new data adding new info; revealing interesting features K2K, NOMAD, MiniBooNE
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Sam Zeller, NO-VE Workshop, 02/07/06 7 magnetic horn: meson focusing decay region: K→ movable absorber: stops muons, undecayed mesons “LMC” measure K flux in-situ 450 m earth berm: magnetic focusing horn FNAL 8 GeV Booster MiniBooNE detector (CH 2 ) MiniBooNE Beamline >700,000 contained events providing a valuable sample to study low E cross sections
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Sam Zeller, NO-VE Workshop, 02/07/06 8 Flux at MiniBooNE Detector MC predicted energy spectrum mainly from production constrained by global data & E910 … - eventually HARP - really advance knowledge of low E hadroproduction (see Gibin’s talk) incident on detector: high purity beam (>99% flavor) PRELIMINARY
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Sam Zeller, NO-VE Workshop, 02/07/06 9 Flux at MiniBooNE Detector MC predicted energy spectrum - 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 ~ 1.3 GeV ~ 10 GeV ~ 24 GeV PRELIMINARY
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Sam Zeller, NO-VE Workshop, 02/07/06 10 Event Fractions at MiniBooNE - 48% CC QE - 31% CC - 8% NC 0 - 5% CC 0 - 3% NC +/- - 4% multi- - 1% NC elastic MiniBooNE flux- averaged event compositions (N TANK >200, N VETO <6) demonstrate understanding of 79% of events before analyzing e (<1% of total) this flux spectrum dictates what type of interactions we see …
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Sam Zeller, NO-VE Workshop, 02/07/06 11 Quasi-Elastic Scattering Why important? n → - p QE necessary to accurately predict signal rates in oscillation experiments (including our own) * e QE are main signal for e 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)
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Sam Zeller, NO-VE Workshop, 02/07/06 12 Quasi-Elastic Scattering highest statistics ~2500 events low E data on D 2 n → - p
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Sam Zeller, NO-VE Workshop, 02/07/06 13 Quasi-Elastic Scattering n → - p new information already coming in (NOMAD, 12 C) (R. Petti, NuInt05)
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Sam Zeller, NO-VE Workshop, 02/07/06 14 Quasi-Elastic Scattering n → - p MiniBooNE: - 12 C (valuable for osc exps) - this analysis: 60k events (3.2x10 20 POT) (already more data than all previous exps combined) - can select 86% pure QE sample
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Sam Zeller, NO-VE Workshop, 02/07/06 15 MiniBooNE QE Data measure visible E and from mostly Čerenkov ( ) + some scintillation light (p) n → - p most copious events at MiniBooNE also simplest: two body kinematics (J. Monroe) forward muons corresponds to low Q 2 …
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Sam Zeller, NO-VE Workshop, 02/07/06 16 to improve data, MC agreement performing shape fits for: (J. Monroe) - axial form factor (M A ) & - nuclear model pars (E B,p F ) incorporating new nuclear models (R. Tayloe) (that are constrained by modern electron scattering data) MiniBooNE QE Data similar effect seen by K2K working on understanding these features in our data … Q 2 = m 2 - 2E (E -p cos )
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Sam Zeller, NO-VE Workshop, 02/07/06 17 MiniBooNE QE Data 2M p E – m 2 E QE = 2(M p -E +p cos ) (J. Monroe) energy distribution that will be used for CC + /QE cross section measurement next, numerator (CC + ) … making use of E , …
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Sam Zeller, NO-VE Workshop, 02/07/06 18 forward emitted low Q 2 CC 1 + Production coherent + productionresonant + production (dominant) A A ++
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Sam Zeller, NO-VE Workshop, 02/07/06 19 CC 1 + Production coherent + productionresonant + production (dominant)
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Sam Zeller, NO-VE Workshop, 02/07/06 20 (K2K, hep-ex/0506008) K2K: 1 st search for coh + prod at low E somewhat surprising results … see no evidence for coh + production! CC 1 + Production coherent + productionresonant + production (dominant)
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Sam Zeller, NO-VE Workshop, 02/07/06 21 forward emitted low Q 2 CC 1 + Production MiniBooNE:- inclusive measurement, CH 2 - this analysis: 40k events (3.2x10 20 POT) (5x more than previous bubble chamber data combined) coherent + productionresonant + production (dominant) A A ++
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Sam Zeller, NO-VE Workshop, 02/07/06 22 CC + Production Why important? poses largest background to QE samples (large & + can be absorbed in nucleus) useful for understanding production in CH 2 ( → N a background to → e search) possibility for CC + oscillation search useful in understanding our event reconstruction N → N +
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Sam Zeller, NO-VE Workshop, 02/07/06 23 MiniBooNE CC + Selection very simple selection: - events with 2 decay electrons - unique, results in 84% purity -- e-e- e+e+ ++ ++ ee (M. Wascko) =2070 ±16 ns = 2242 ± 17 ns +e++e+ expect to have shorter lifetime from capture (8% in 12 C) - will also make use of this later
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Sam Zeller, NO-VE Workshop, 02/07/06 24 MiniBooNE CC + Reconstruction measure Čerenkov light from muon (to avoid light from + ) (M. Wascko) see larger deficit in forward (low Q 2 ) than in QE data
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Sam Zeller, NO-VE Workshop, 02/07/06 25 MiniBooNE CC + Data (M. Wascko) 2M p E – m 2 + (m 2 -M p 2 ) “E QE ” = 2(M p -E +p cos ) 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
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Sam Zeller, NO-VE Workshop, 02/07/06 26 MiniBooNE CC + /QE Ratio efficiency corrected CC + /QE ratio meas on CH 2 eff corrections from MC ample statistics can perform a binned measurement (J. Monroe, M. Wascko) first measurement of this cross section ratio on a nuclear target at low energy! current systematics estimate: - light propagation in oil: ~20% - cross sections: ~15% - energy scale: ~10% - statistics: ~5%
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Sam Zeller, NO-VE Workshop, 02/07/06 27 MiniBooNE CC + Cross Section multiplying measured CC + /QE ratio by QE prediction ( QE with M A =1.03 GeV, BBA non-dipole vector form factors) (J. Monroe, M. Wascko) ~25% lower than prediction, but within errors MC error band from external data constraints
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Sam Zeller, NO-VE Workshop, 02/07/06 28 Plausible Interpretation since MiniBooNE 1 st meas on nuclear target at these E’s at 1 st glance, one might think this is pointing to a potential problem with nuclear corrs
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Sam Zeller, NO-VE Workshop, 02/07/06 29 Plausible Interpretation since MiniBooNE 1 st meas on nuclear target at these E’s at 1 st glance, one might think this is pointing to a potential problem with nuclear corrs 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 but free nucleon ’s disagree! BNL ANL MC prediction splits difference
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Sam Zeller, NO-VE Workshop, 02/07/06 30 New Directions at MiniBooNE new antineutrino data! observing events from NuMI coming soon: new fine-grained new detector to this beamline (comparisons to MiniBooNEwill be interesting)
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Sam Zeller, NO-VE Workshop, 02/07/06 31 MiniBooNE Antineutrino Running 1 st MiniBooNE antineutrino event goals are two-fold: - check LSND → e signal (longer program) - measure cross sections - systematic check of analyses - low Q 2 investigations - coherent production just started antineutrino running (January 19 th ) - ~1,000 events/week - will have world’s largest low E data set in a few weeks!
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Sam Zeller, NO-VE Workshop, 02/07/06 32 Need for Measurements data even less abundant provide valuable input for future CP violation searches P( → e ) ≠ P( → e ) prefer not to rely on extrapolation of models into regions where no data MiniBooNE will make world’s 1 st meas of in this E range - expect ~10k QE in 1 year (after cuts)
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Sam Zeller, NO-VE Workshop, 02/07/06 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
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Sam Zeller, NO-VE Workshop, 02/07/06 34 Added Difficulty with Beams contending with “wrong sign” backgrounds ( in beam) - MiniBooNE beam is no exception … need a way to constrain backgrounds in data Čerenkov detectors cannot distinguish , + event-by-event (no magnetic field) in antineutrino mode, neutrinos are ~30% of total events “ -enhanced beam”
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Sam Zeller, NO-VE Workshop, 02/07/06 35 Constraining Backgrounds in Data needed to be more clever developed several novel techniques to measure from data 1 st and most powerful … makes use of fact that QE & have different angular distributions large angle QE’s as means of measuring content in data (“poor man’s sign-selection”)
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Sam Zeller, NO-VE Workshop, 02/07/06 36 1.QE angular distributions provide best “wrong-sign” constraint, but also … 7% constraint 2. add’l constraint from CC + events in mode data (come entirely from interactions as ’s produce a _ in final state) - higher E constraint 15% constraint 3. also muon lifetimes ( vs. + to distinguish vs. ) - and + have different lifetimes due to capture probability in oil - not as precise a constraint, but indep of kinematics & recon 30% constraint → allows precise antineutrino measurements (once have a handle on backgrounds) redundant checks Three Independent Constraints
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Sam Zeller, NO-VE Workshop, 02/07/06 37 Antineutrino Measurements can add new info by mere fact that scattering is different d dQ 2 QE different shape & axial contribution difference isolates interference term - directly to axial FF
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Sam Zeller, NO-VE Workshop, 02/07/06 38 Antineutrino Measurements can add new info by mere fact that scattering is different NC 0 20% is coherent production 40% is coherent production “enhanced” coherent sample latest K2K results say this peak will be missing: very apparent in data
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Sam Zeller, NO-VE Workshop, 02/07/06 39 Can Detect ’s from NuMI ! NuMI events in MiniBooNE detector (A. Aquilar-Arevalo) ~10,000 events so far 100’s of e events (calibration) also opened up possibility to use this sample for meas (slightly diff beam spectrum) - MINOS also sees MiniBooNE neutrinos in their detector neighbor’s beam first off-axis neutrino beam!
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Sam Zeller, NO-VE Workshop, 02/07/06 40 SciBooNE (E954) new Int’l collaboration - couple well-understood, fine-grained detector with high rate beam - unique, low risk opportunity
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Sam Zeller, NO-VE Workshop, 02/07/06 41 SciBooNE (E954) new Int’l collaboration - excellent final state resolution - improve on MiniBooNE studies - couple well-understood, fine-grained detector with high rate beam - unique, low risk opportunity
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Sam Zeller, NO-VE Workshop, 02/07/06 42 SciBooNE (E954) new Int’l collaboration - measurements for T2K just received Stage 1 approval (Dec ‘05) rapid schedule: begin data taking this Fall www-sciboone.fnal.gov - excellent final state resolution - improve on MiniBooNE studies - couple well-understood, fine-grained detector with high rate beam - unique, low risk opportunity
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Sam Zeller, NO-VE Workshop, 02/07/06 43 Conclusions coming soon … - CC QE cross section results - NC 0 cross sections flux cross sections collected > 700k neutrino (> 1k antineutrino) events (7 x 10 20 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 - 1 st results on MiniBooNE CC + /QE cross section stay tuned for e oscillation results - HARP results (8 GeV, Be, thick target)
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