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Oscillation Research with Cosmics in the Abyss

Oscillation Research with Cosmics in the Abyss. ORCA. Status report on the feasibility of measuring the neutrino mass hierarchy with an underwater Cherenkov detector. Antoine Kouchner University Paris 7 Diderot- AstroParticle and Cosmology . [INTERNAL DOCUMENT ] ALL PRELIMINARY.

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Oscillation Research with Cosmics in the Abyss

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  1. Oscillation Research with Cosmics in the Abyss ORCA Status report on the feasibility of measuring the neutrino mass hierarchy with an underwater Cherenkov detector Antoine Kouchner University Paris 7 Diderot- AstroParticle and Cosmology [INTERNAL DOCUMENT ] ALL PRELIMINARY KM3NeT STAC meeting Rome 16/01/2014

  2. Outline • Organization of ORCA • The ORCA report for the KM3NeT STAC • Introduction • Reference detector simulation • Intrinsic fluctuations • Event selection and reconstruction • Sensitivity studies • Flavouridentification • Impact of misidentification • Electron neutrino studies • Detector optimisationstrategy • A Neutrino Beam towards the ORCA detector • Outlook

  3. ORCA organization • Study started in September 2012 (after Neutrino 2012 conference) • KM3NeT collaboration (phase I) + few other neutrino physics colleagues • Coordination: A.Kouchner • Mailing list: orca-l@in2p3.fr • ORCA indico: https://indico.cern.ch/categoryDisplay.py?categId=4384 • Wiki page : https://sbgorcawiki.in2p3.fr/doku.php • Document editorial board: Th. Eberl, A. Kouchner, V. Van Elewyck

  4. ORCA organization External invited speakers Announce of a change in strategy  towards optimization of the detector geometry • Not completely successful in establishing • a tight working group with PINGU • MANTs meeting useful • GNN will hopefully help

  5. Oscillations of Massive Neutrinos • Neutrinos have distinct masses and mix (PMNS) Normal hierarchy Atmospheric qA~45° Reactor q13~9°  CP violating phase dCP Solar q~30° Majorana • Neutrino oscillations can be described with 6 • parameters (3 Dirac neutrinos): • 3 mixing angles • 2 mass-squared differences • CP phase  Phys. Rev. D 86 (2012) (<10%) Inverted hierarchy MH • Absolute mass scale • Nature (Dirac vsMajorana) • Origin of neutrino mass and flavor • Core-Collapse Supernovae Physics Which octant for q23 ?

  6. Oscillations of Massive Neutrinos  G. L. Fogli, E. Lisi, A. Marrone, D. Montanino, A. Palazzo and A. M. Rotunno, Phys. Rev. D 86 (2012)

  7. MH with LBL experiments eff eff • « Standard approach » :probe nmne governed by Dm213 (D13) • Insensitive to the sign of Dm213 at leading order. • Matter effects (MSW) come to the rescue • Earth density variations (e.g. mantle-core) also affect the oscillations (parametric resonance) [Neglecting solar (> a few GeV and >1000’s km) and CP violation effects] • Through matter, neutrinos interact • acquiring an effective mass (forward scattering) • Only electron neutrinos interact through • CCwith electrons • Additional potential A in the Hamiltonian (−)+ for (anti-)neutrinos • Modify the oscillation probability

  8. (Constant Density) Matter Effects From A. de Gouvea Same signs Opposite signs Matter resonance: A D13cos2q13- Effective mixing maximal- Effective osc. frequency minimal Resonance energy Earth: - Mantle Eres ~ 7 GeV- Core Eres ~ 3 GeV • Requirements: • D13 ~ A matter potential must be significant but not overwhelming • L large enough – matter effects are absent near the origin • Distinction between neutrinos and anti-neutrinos •  different flux and cross-sections!

  9. Phenomenological Considerations Inverted Hierachy cosq = −0.6 cosq = −1 Normal Hierachy In each case, CP-phase is varied in steps of 30 degrees • Hierarchy differences disappear at around 15 GeV • P(nmne) < 2% at 20 GeV GLoBES GLoBES P(nm nm), NH

  10. Phenomenological Considerations Inverted Hierachy cosq = −0.6 cosq = −1 Normal Hierachy In each case, CP-phase is varied in steps of 30 degrees • Hierarchy differences disappear at around 15 GeV • P(nmne) < 2% at 20 GeV GLoBES GLoBES 2 flavor P(nmnt) in vacuum is a valid approximation Recent results from ANTARES and IceCube

  11. Phenomenological Considerations Inverted Hierachy cosq = −0.6 cosq = −1 Normal Hierachy In each case, CP-phase is varied in steps of 30 degrees • Hierarchy differences disappear at around 15 GeV • P(nmne) < 2% at 20 GeV GLoBES GLoBES cosq = −0.6 Degeneracies due to parameter uncertainties must be carefully considered!

  12. First (optimistic) sensitivities  Akhmedov et al. JHEP 02 (2013) 082 With exceedingly large PINGU effective volume Uncorrelated systematics E=4 GeV, = 22.5° Perfect resolutions S=7.2 (f=0%) S=4.5 (f=5%) S=3.0 (f=10%) S=45.5 (f=0%) S=28.9 (f=5%) S=18.8 (f=10%) In 5 years

  13. x Atmospheric neutrino spectrum A beam for free! • Honda et al. PRD 83:123001,2011 f x E-2 (GeV cm-1 sr-1 s-1) • Produce neutrinos and anti-neutrinos • Broad energy range – Steeply falling spectrum • Requires good energy resolution • Broad path-length range •  Requires good direction resolution Calculations now made as a function of the position on Earth and the time in year r “Screening effect” r~2 sin2q23~0.5 But enhancement possible: - r increases with energy - Larger effect for second octant

  14. Muon versus Electron channels • Agarwalla et al. arXiv:1212.2238 Muons provide more statistics Electron channel is more robust against detector resolutions… Brings sensitivity to the Mass hierarchy Lately considered by PINGU and ORCA as opposed to SK/HK ±10% Earth density

  15. x x Neutrino Interactions Different cross sections for n and n ! Different topologies: cosq = −0.6 Track-like • M.S. Athar et al. • arXiv:1210.5154 • Calculations now made as a function of the position on Earth and the time in year f x E-2 (GeV cm-1 sr-1 s-1) Shower-like s/E(10-38 GeV-1 cm-2) Systematics  Use external measurements and regions without oscillations • Kajita, New J. Phys. 6 (2004) 194

  16. Studies on intrinsic physics fluctuations Showers (hadronic & electromagnetic) • Study to derive intrinsic limits on achievable reconstruction accuracies. • energy (direction) resolution for a 5 GeV muon is limited to 0.5 GeV (0.2°). • energy (direction) resolution for a 5 GeV hadonic cascade limited to 25% (14°) Energy Showers Direction Showers Useful results to guide the optimization of the detector design and to set upper bounds on the sensitivity to the NMH

  17. Studies on intrinsic physics fluctuations Muons Energy Direction From fluctuations of muon path length Fluctuation from detection ~1m So 0.2GeV for both start & end-point Based on straight line fit of muon direction generated along z-axis. Useful results to guide the optimization of the detector design and to set upper bounds on the sensitivity to the NMH

  18. Reference Detector generation Simulation chain GENIE checkedagainst GENHEN

  19. Reference Detector generation ORCA reference detector

  20. Detector performance studies Trigger studies (Pure noise) TnOMm : n OMs with m pulses neighboured or next-to-neighboured 10ns TnSm : n Strings with m OMs Trigger rate (atmospheric muons) 5Hz Encouraging results. Should be pursued. No high priority

  21. Detector performance studies Improvements in reconstruction for muon neutrinos ANTARES-inspired reconstruction 1/ Improved hit selection (75% efficiency, 90% purity) 2/ Muon track reconstruction 3/ Muon tracklength estimation: First-guess vertex position « pseudo-vertex »

  22. Detector performance studies Improvements in reconstruction for muon neutrinos 4/ Identification of shower hits based on time residuals, distance from vertex and Cherenkov light emission pattern 5/ Re-estimation of pseudo-vertex pos. (assuming spherically expanding hadronic shower) improved pseudo-vertex identification improved track length estimate

  23. Detector performance studies Improvements in reconstruction for muon neutrinos Instrumented volume Current official plot ANGULAR RESOLUTION EFFECTIVE VOLUME Non Contained degrade improve Inputs for guaranteed sensitivity estimates

  24. Detector performance studies Improvements in reconstruction for muon neutrinos • Performances on muon energy reconstruction • (color band is 1σ range, line ismedian per muon energybin) VERTEX CONTAINED Upgoingevents TRACK FULLY CONTAINED Input for “worst case” sensitivity estimates Muon energyestimatemostreliable for fullycontainedtracks need estimation of showerenergy to obtain neutrino energy

  25. Detector performance studies Improvements in reconstruction for muon neutrinos Performances on neutrino energy reconstruction inferred from MC parameterisation ~30% @ 10GeV But better can be done ! Using the hits from the hadronic shower should help a priority

  26. Detector performance studies Improvements in reconstruction for muon neutrinos Alternative reconstruction: FilteringFit

  27. Detector performance studies Improvements in reconstruction for muon neutrinos Alternative reconstruction: FilteringFit 0.5<y<1 0<y<0.5 Consistency! Robustness

  28. Detector performance studies Muon background rejection Cut on the reconstructed pseudo-vertex and quality parameters of reconstruction Atmospheric muons Atmospheric neutrinos Atmospheric neutrinos below 20 GeV Encouraging results indicating that an instrumental veto is not mandatory To be continued…

  29. Flavour (mis)-identification Classification Strategy Use of machine learning algorithm based on decision trees,with 32 observables tested including: time residuals, tensor of inertia, hit distance to vertex… Performances expressed in terms of: Goal discriminate between track-like and !(track-like) 80% of muon CC with E>8GeVwith less than 20% contamination from cascades The classification rate is much more sensitive to the event energy than the purity

  30. Flavour (mis)-identification Impact of shower misidentification Classification Strategy Used to evaluate the impact on the NMH sensitivity in the muon channel Adding Gaussian smearing for shower: And only kinematic smearing for muons Energy independent for showers Dropin significance (Asymmetry) is only limited to 15%, but dependent on assumptions

  31. Flavour (mis)-identification Impact of tau neutrino appearance Classification Strategy Effective volume assumed: 1Mt constant for tau neutrino. Energy lost in neutrinos from tau decay subtracted Dropin significance (Asymmetry) is less than 10%,

  32. cos(q) example of 1yr of data log(E) Sensitivitystudies Global Fit Approach to optimally distinguish between IH and NH: likelihood ratio test with nuisance parameters → in other words: deal with degeneracies by fitting! 1) fit mixing parameters assuming NH 2) fit mixing parameters assuming IH 3) compute DlogL = log( L(NH)/L(IH) ) toy datasets generated with IH toy datasets generated with NH

  33. Sensitivity studies Fit working well. Good sensitivity to Dm2large &q23 Results of Parameters Fit Example shown: 1 Mton*year ( NHtrue, NHfit ) fitted value fitted value fitted value generatedDm2large generatedq13 generatedq23 Config B Config A

  34. Sensitivity studies Calculation of the significance (1.8 Mt.yr) (9 Mt.yr) DT Median Significance S50%= ½(sIH+sNH) (18 Mt.yr) (36 Mt.yr) Note: in practice S50% (exclude NH) > S50% S50% (exclude IH) < S50% DT

  35. Sensitivity studies (muons) Updated results (50% chance) (50% chance) Worst case scenario Config A Perfect muon direction from Generator Gaussian smearing for Energy • Config B • Selected-rec. angular resolution • bias towards low-y events • Selected-rec. energy resolution • as obtained with muon path length 10 years: 2.6 -- 4.6 s

  36. Sensitivity studies (muons) Study of Systematics Method: extended unbinned log-likelihood ratio  D. Franco et al, JHEP 04 (2013) 008 Almost negligible impact Earth Model • Atmospheric neutrinos flux • Shape • Normalization Moderate impact Large impact but normalization from data PMNS uncertainties Negligible impact varying combinations of {q12, Dm221} (± 1s) Large impact varying combinations of {q13,q23, Dm231} (± 1s) Small impact varying CP phase Several other studies point to the same conclusions…

  37. Cascade channel • Oscillation probabilities • Values from Fogli et al. (arxiv:1205.5254) • 23=45˚ (avoid octant problem) • CP-phases : colored bands (NH : red, IH : blue) • Averaged over fluxes (Honda) and cross sections muons electrons cos = 0.85 cos = 0.85

  38. Relative significances e Not combined yet. Expected increase of significance of about a factor 2.5 wrt muons only µ Significance (a.u) No particle ID The study will be continued (with high priority) including the development of a full cascade reconstruction

  39. Layout Optimisationstrategy The dense detector On going study • Dense geometry with a 3x3x3m spacing • Full GENIE followed by GEANT 4 simulation • Includes all physics processes (Scattering, Michel electrons…) • “Switch off” some OMs for optimization • Ignore shadowing effect in first stage • Advantages: • Allows for studying various config • Allows for (non-)containment /veto studies • Quite CPU consuming • Premiumeventsconcept Successfully used to reproduce results obtained with reference detector

  40. Layout Optimisation strategy Premium Events • Events where all the produced light is (nearly) contained in the instrumented volume • Advantages: • No simulated event is thrown away • Infinite Grid for study of chosen density • Surface/edge effects can by studied with masks Concept exported to the reference detector as well.

  41. A Neutrino beam to ORCA? I Counting muons • Optimum 6-8 GeV 6000-8000 km but beam inclination • Lujan-Peschard et al, Eur. Phys. J. C (2013) 73:2439 ; Tang & Winter, JHEP 1202 (2012) 028 1020 pot 1 Mt mass NUMI beamrescaled to 7800 km • 9 s separation on purely statistical • ground in one year

  42. A Neutrino beam to ORCA? II Counting electrons • Protvino-ORCA L=2588 km, beam inclined by 11.7° • (3° off-axis from Fréjus Underground laboratory)  J. Brunner, arXiv:1304.6230 NH 2nd octant CP band CP band 1st octant IH Neutrino Anti-neutrino Fluxes (SKAT exp. Needs update)

  43. A Neutrino beam to ORCA? III Counting electrons • Vertex inside ORCA reference detector • Flavor misidentification probability • based on C2GT project • Event rates for 1.5x1021 pot (3 years) 7 s statistical separation -- 3 s with 3-4% sys No assumption on energy reconstruction

  44. ORCA vs PINGU comparisons Geometries 450 m 50 lines, 20m spaced, 20 OM/line 6m spaced Instrumented volume ~2 Mt 1000 OM 40 strings, 20 spaced, 60 OM/string 5m spaced Instrumented volume ~ 6 Mt 2400 OM (~60-80M$)  PINGU Letter of Intent: http://arxiv.org/abs/1401.2046.

  45. ORCA vs PINGU comparisons Geometries ORCA 450 m (Muon channel) 50 lines, 20m spaced, 20 OM/line 6m spaced Instrumented volume ~1.8 Mt 1000 OM 40 strings, 20 spaced, 60 OM/string 5m spaced Instrumented volume ~ 5.5 Mt 2400 OM (~60-80M$)  PINGU Letter of Intent: http://arxiv.org/abs/1401.2046.

  46. ORCA vs PINGU comparisons Performances Water is a better tracker 450 m PINGU Ice is a better calorimeter Estimated with m path length ORCA (muon path length)

  47. ORCA vs PINGU comparisons Sensitivity ORCA TRACKS 2O strings Combined Cascades Tracks 40 strings Updated PINGU (tracks) Important loss of sensitivity wrt Snowmass partly recovered with “cascade” events Not fair comparison as PINGU includes more effects Now compatible with e.g. W. Winter, PRD 88, 1, 013013

  48. Summary • Many progresses made since September 2012 • Muon track, energy reconstruction • Sensitivity study, impact of systematics • Beam to ORCA, part of the feasibility study • Contacts made with LBL experiments colleagues • Design Optimisation strategy established in progress. • Conclusion so far: high enough physics case to pursue the feasibility study. Not high enough to discuss, within KM3NeT, a possible proposal. • Work program for 2014: • Use multi-PMT DOM features to full potential • Improvements in muon energy reconstruction • Improvement in the sensitivity from cascades based on newly developed algorithms • Combine all exiting studies in the sensitivity estimate to yield 3(5) sigma in 3(10) years. • ORCA should be present at Neutrino 2014!

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