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, our 1 st cross section results (CC  + /QE) - future directions in MiniBooNE   program

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

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

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 % 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

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

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

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

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

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

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 …

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)

Sam Zeller, NO-VE Workshop, 02/07/06 12 Quasi-Elastic Scattering highest statistics ~2500 events low E data on D 2  n →  - p

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)

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

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 …

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   )

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 ,   …

Sam Zeller, NO-VE Workshop, 02/07/06 18 forward emitted  low Q 2 CC 1  + Production coherent  + productionresonant  + production (dominant) A A ++

Sam Zeller, NO-VE Workshop, 02/07/06 19 CC 1  + Production coherent  + productionresonant  + production (dominant)

Sam Zeller, NO-VE Workshop, 02/07/06 20 (K2K, hep-ex/ ) 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)

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 ++

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  +

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+ ++ ++ ee (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

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

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

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%

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

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

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

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)

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!

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)

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

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”

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”)

Sam Zeller, NO-VE Workshop, 02/07/ 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

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

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

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!

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

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

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

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 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)