1 Mike Kordosky – NuFact 06 - Aug 27, 2006 Neutrino Interactions in the MINOS Near Detector Mike Kordosky University College London on behalf of the MINOS Collaboration

2 Mike Kordosky – NuFact 06 - Aug 27, 2006 Plan for this talk ● Introduction & CC sample: – NuMI beam, energy and kinematics coverage – MINOS Near Detector, data collection and reconstruction – Selection of n m -CC events, energy spectra, kinematics distributions ● Flux extraction strategies: – Low-n method – QE selection and method ● DIS measurements: – Projected cross section and structure function measurements – Prospects for a di-muon measurement

3 Mike Kordosky – NuFact 06 - Aug 27, 2006 Introduction and CC sample

4 Mike Kordosky – NuFact 06 - Aug 27, 2006 The NuMI neutrino beam ● Variable target position = variable beam energy! ● Two magnetic focusing horns ● Sign selected beam: neutrino or anti-neutrino enriched to Near Detector

5 Mike Kordosky – NuFact 06 - Aug 27, 2006 The NuMI neutrino beam  = 92.9%  = 5.8% e  e = 1.3% Exposure (to March 3, 2006) Beam Composition (LE)

6 Mike Kordosky – NuFact 06 - Aug 27, 2006 Kinematic Coverage of the LE Beam A B C D A) Safe-DIS: 24.2% ● |Q| > 1 GeV/c ● |W| > 2 GeV B) Low Q 2 DIS: 8.5% ● |Q| < 1 GeV/c ● |W| > 2 GeV C) RES ⇔ DIS: 32.4% ● 2.0<W<1.3 GeV D) QEL + D: 34.8% ● W<1.3 GeV Kinematic Regions QE/RES/DIS: 19/23/57%

7 Mike Kordosky – NuFact 06 - Aug 27, 2006 Kinematic Coverage of the LE Beam A B C D A) Safe-DIS: 24.2% ● |Q| > 1 GeV/c ● |W| > 2 GeV B) Low Q 2 DIS: 8.5% ● |Q| < 1 GeV/c ● |W| > 2 GeV C) RES ⇔ DIS: 32.4% ● 2.0<W<1.3 GeV D) QEL + D: 34.8% ● W<1.3 GeV Kinematic Regions QE/RES/DIS: 19/23/57%

8 Mike Kordosky – NuFact 06 - Aug 27, 2006 Near Detector ● 1km from Target ● 0.98 kton ● 282 steel planes – = calorimeter – 120+ = spectrometer ● B=1.2 T ● 64-anode PMTs ● High Rates ● QIE electronics – no deadtime! Near detector during installation Partial Plane PMTs, QIE electronics Beam Full Plane Coil Hole To Far detector

9 Mike Kordosky – NuFact 06 - Aug 27, 2006 Detector Technology 2.54cm Steel absorber ● Tracking-Sampling calorimeter ● Segmentation: – 5.94cm longitudinal – 4.1cm transverse ● Planes rotated +/- 90 deg ● WLS collects/routes light to PMTs Scint. 1cm thick, 4.1 cm wide WLS Fibers Multi-anode PMT Fiber ''cookie'' Scint. Plane Readout Cable PMT Dark Box M64 PMT M16 PMT

10 Mike Kordosky – NuFact 06 - Aug 27, 2006 Event Reconstruction ● High rate in Near detector results in multiple neutrino interactions per MI spill ● Events are separated by topology and timing (19ns resolution) Batch structure clearly seen! One near detector spill 7.1 m beam direction

11 Mike Kordosky – NuFact 06 - Aug 27, 2006 CC event topology E = E shower +P  Shower Energy Resolution: ~56%/  E Muon Energy Resolution 6% range, 13% curvature n m -CC event

12 Mike Kordosky – NuFact 06 - Aug 27, 2006 ● 1 good track – Stopping = p range – Exiting = p curvature ● Vertex in fiducial volume – Centered on beam spot ● Negative charge (for n m ) ● Topological PID to discriminate CC/NC n m -CC event selection Calorimete r Spectrometer m-m-

13 Mike Kordosky – NuFact 06 - Aug 27, 2006 CC/NC classification event length fraction of signal in track PID efficiency average track signal/plane ~dE/dx Require PID > -0.1

14 Mike Kordosky – NuFact 06 - Aug 27, 2006 Energy Spectra Reweight pion x F and p T to improve data/MC agreement Include horn focusing, NC normalization, energy scale as nuisance parameters low energy beam medium energy beam high energy beam

15 Mike Kordosky – NuFact 06 - Aug 27, 2006 ● NEUGEN3 generator (H.Gallagher, Nucl.Phys.Proc.Suppl. 112, , 2002) ● QEL: dipole parameterisation with m A = GeV/c 2 ● Resonance production: Rein- Seghal for W<1.7 GeV/c 2 ● DIS: Bodek-Yang modified LO model, tuned to e and n data in resonance/DIS overlap region ● Coherent production ● Nuclear model: Fermi Gas model, Pauli blocking of QEL scattering ● Final state interactions for pions Event Generation

16 Mike Kordosky – NuFact 06 - Aug 27, 2006 Kinematic Distributions High Energy Tail 10 < E < 30 GeV Best understood flux “Safe DIS” W>2 GeV, Q>1 GeV/c Best understood cross-section MINOS preliminary MINOS preliminary

17 Mike Kordosky – NuFact 06 - Aug 27, 2006 Neutrino Flux Measurements

18 Mike Kordosky – NuFact 06 - Aug 27, 2006 Low-n approach

19 Mike Kordosky – NuFact 06 - Aug 27, 2006 Low-n approach ● Require, in lieu of PID: p m > 2 GeV/c, E shw < 1 GeV ● Acceptance correction from MC to give N(E) ● Correction for energy dependent s QEL (35-45% QE) ● B/A correction to inelastic cross section Bands computed from physical limits Neutrino: < B/A < 0.0 Anti-neutrino: -2.0 < B/A < -1.7

20 Mike Kordosky – NuFact 06 - Aug 27, 2006 Measured Flux LE Beam Data v. MC flux for LE-10 beam. Normalization is to POT exposure. flux data/MC MINOS preliminary data MC

21 Mike Kordosky – NuFact 06 - Aug 27, 2006 Low-n Approach Prognosis ● Current uncertainties dominated by MC statistics for acceptance correction ● B/A corrections have large uncertainty for E n < 5 GeV ● Evaluation of systematic errors ● Improve purity of anti-neutrino sample (now 91.4%) ● Investigating radiative corrections ● “unfolding” rather than binned acceptance correction? muon energy scale +/- 2% shower energy scale +/- 2%

22 Mike Kordosky – NuFact 06 - Aug 27, 2006 Quasi-elastic approach ● s QEL reasonably well constrained, and ~flat ● select QE enriched sample GeV ● flux shape ● Inclusive s CC well measured above 30 GeV on Fe ● inclusive CC sample GeV ● flux normalization shape normalization neutrino energy (GeV)  CC /E

23 Mike Kordosky – NuFact 06 - Aug 27, 2006 Quasi-elastic flux extraction Selected Events NC background (MC) Extracted Flux Cross Sections (MC) Selection Efficiencies (MC) Normalization fixed according to inclusive sample GeV

24 Mike Kordosky – NuFact 06 - Aug 27, 2006 Quasi-elastic selection efficiency ~ 40% purity ~ 70% Monte Carlo ● PDF based selection procedure, using shower topology, expected proton direction, reco-W. ● 40% efficiency, 70% purity (MC), energy independent

25 Mike Kordosky – NuFact 06 - Aug 27, 2006 Quasi-elastic prognosis ● Basic method works when applied to fake data ● Selection procedure based on low-energy shower topology. Uncertainties in: – single particle response (have test beam data) – final state interactions (difficult to quantify and model) ● cross-section uncertainties less serious – s RES also flat w/energy

26 Mike Kordosky – NuFact 06 - Aug 27, 2006 Cross Section Measurements

27 Mike Kordosky – NuFact 06 - Aug 27, 2006 Total cross section ● Event selection, as before but: – p m > 2 GeV/c, separate by muon charge ● purity: n m =99.4%, anti-n m = 91.4% ● Cross section simply: ● Energy dependence only: norm. to world average at high energy “Mock Data” Extracted Cross Section

28 Mike Kordosky – NuFact 06 - Aug 27, 2006 Cross Section Systematics ● Very large (0.8e5 /1e20 POT) event sample, measurement will be systematics limited, even for anti-n shower energy scale muon energy scale

29 Mike Kordosky – NuFact 06 - Aug 27, 2006 Structure Functions MINOS: Statistics only, 7.4e20 POT Systematics due to energy scale +/- 2% E m scale +/- 5% E had scale Q 2 = 2 (GeV/c) 2 X F 2 (x) F 2 (x,Q 2 ) Q 2 (GeV/c) 2 Q 2 =2 (GeV/c) 2 Projected F 2 reach (MC study) MINOS(MC) NuTeV CCFR CDHSW GRV98o+HT

30 Mike Kordosky – NuFact 06 - Aug 27, 2006 Di-muon prospects Rev.Mod.Phys. v70, n4 (1998) neutrino energy (GeV) Reconstructed Energy Spectrum LE Beam (MC) arbitrary normalization Di-m rate & shape sensitive to charm production mechanism, charm mass MINOS event sample concentrated in interesting low energy region (few 10s of GeV)

31 Mike Kordosky – NuFact 06 - Aug 27, 2006 Di-muon prospects Estimated Sample Size A fully reconstructed di-m event A work in progress, main challenges: Efficient 2 track reconstruction Background rejection: ~1e4 needed for ~10% background

32 Mike Kordosky – NuFact 06 - Aug 27, 2006 Summary ● Intense NuMI beam and highly efficient MINOS Near Detector offer excellent opportunities for cross-section measurements at low energy and low-Q 2 ● Data collection/ reconstruction well understood ● Several analyses nearing maturity – Flux extraction – Total n m -CC cross section ● Much to do in the future – Differential cross sections, structure functions – di-muon analysis – m QEL, coherent p production, s NC

33 Mike Kordosky – NuFact 06 - Aug 27, 2006 Backup Slides

34 Mike Kordosky – NuFact 06 - Aug 27, 2006 CC efficiency PID cut only all cuts

35 Mike Kordosky – NuFact 06 - Aug 27, 2006 Energy Spectrum Tuning peak HE tail P T v P z weights

36 Mike Kordosky – NuFact 06 - Aug 27, 2006 Oscillation Result

37 Mike Kordosky – NuFact 06 - Aug 27, 2006 Muon Range v. Curvature

38 Mike Kordosky – NuFact 06 - Aug 27, 2006 ● Calibration Detector = mini-MINOS ● CERN PS ● Sixty 1-m 2 planes ● Near and Far Electronics ● p, e, p and m response at few GeV/c CalDet in T7 1 m Optical Cables PMTs Beam Energy Scale

39 Mike Kordosky – NuFact 06 - Aug 27, 2006 ND Track angle Area normalize d Beam points down 3 degrees to reach Soudan Track angle w.r.t. vertical

40 Mike Kordosky – NuFact 06 - Aug 27, 2006 ND event rate and vertex dist. X Z Y Event rate is flat as a function of time Horn current scans – July 29 – Aug 3 LE-10 Beam

41 Mike Kordosky – NuFact 06 - Aug 27, 2006 Energy spectrum & reconstruction stability ● Reconstructed energy distributions agree to within statistical uncertainties (~1-3%) ● Beam is very stable and there are no significant intensity-dependent biases in event reconstruction. June July August September October November proton intensity ranges from 1e13 ppp - 2.8e13 ppp Energy spectrum by batch Energy spectrum by Month

42 Mike Kordosky – NuFact 06 - Aug 27, 2006 Kinematic Distributions High Energy Tail 10 < E < 30 GeV Best understood flux “Low-Q 2 DIS” W>2 GeV, Q<1 GeV/c Few cross-section measurements MINOS preliminary MINOS preliminary