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A neutrino beam to IceCube/PINGU? (PINGU = “Precision IceCube Next-Generation Upgrade“) NPAC (Nuclear/Particle/Astro/Cosmo) Forum UW-Madison, USA May 15, 2012 Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAA A A A
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2 Contents Introduction Oscillation physics using a core-crossing baseline Neutrino beam to PINGU: Beams and detector parameterization Detector requirements for large 13 Comments on LBNE reconfiguration Summary
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3 Three flavor mixing Use same parameterization as for CKM matrix Pontecorvo-Maki-Nakagawa-Sakata matrix ( ) ( ) ( ) =xx (s ij = sin ij c ij = cos ij ) Potential CP violation ~ 13
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4 13 discovery 2012 First evidence from T2K, Double Chooz Discovery (~ 5 ) independently (?) by Daya Bay, RENO (from arXiv:1204.1249) 1 error bars Daya Bay 3
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5 Mass spectrum/hierarchy Specific models typically come together with specific MH prediction (e.g. textures are very different) Good model discriminator (Albright, Chen, hep-ph/0608137) 8 8 NormalInverted
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6 Three flavors: 6 params (3 angles, one phase; 2 x m 2 ) Describes solar and atmospheric neutrino anomalies, as well as reactor antineutrino disapp.! Three flavors: Summary Coupling : 13 Atmospheric oscillations: Amplitude: 23 Frequency : m 31 2 Solar oscillations : Amplitude: 12 Frequency : m 21 2 Suppressed effect : CP (Super-K, 1998; Chooz, 1999; SNO 2001+2002; KamLAND 2002; Daya Bay, RENO 2012)
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7 Consequences Parameter space for CP starts to become constrained; MH/CPV difficult (need to exclude CP =0 and ) Need new facility! Huber, Lindner, Schwetz, Winter, 2009
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8 Mass hierarchy discovery? 90% CL, existing equipment 3 , Project X and T2K with proton driver, optimized neutrino-antineutrino run plan Huber, Lindner, Schwetz, Winter, JHEP 11 (2009) 44
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9 Mass hierarchy measurement? Mass hierarchy [sgn( m 2 )] discovery possible with atmospheric neutrinos? (liquid argon, HyperK, MEMPHYS, INO, PINGU?, LENA?, …) Barger et al, arXiv:1203.6012; IH more challenging However: also long-baseline proposals! (LBNO: superbeam ~ 2200 km – LAGUNA design study; CERN-SuperK ~ 8870 km – Agarwalla, Hernandez, arXiv:1204.4217; South Pole: Dick et al, 2000) Perhaps different facilities for MH and CPV proposed/discussed?
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Oscillation physics using a core-crossing baseline
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11 What is PINGU? 2012
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12 PINGU fiducial volume? A few Mt fiducial mass for superbeam produced with FNAL main injector protons (120 GeV) (Jason Koskinen) LBNE- beam
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13 Beams to PINGU? Labs and potential detector locations (stars) in “deep underground“ laboratories: (Agarwalla, Huber, Tang, Winter, 2010) FNAL-PINGU: 11620 km CERN-PINGU: 11810 km RAL-PINGU: 12020 km JHF-PINGU: 11370 km All these baselines cross the Earth‘s outer core!
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14 Matter profile of the Earth … as seen by a neutrino (PREM: Preliminary Reference Earth Model) Core Inner core
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15 Matter effect (MSW) Ordinary matter: electrons, but no , Coherent forward scattering in matter: Net effect on electron flavor Hamiltonian in matter (matrix form, flavor space): Y: electron fraction ~ 0.5 (electrons per nucleon) (Wolfenstein, 1978; Mikheyev, Smirnov, 1985)
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16 Parameter mapping Oscillation probabilities in vacuum: matter: Matter resonance: In this case: - Effective mixing maximal - Effective osc. frequency minimal For appearance, m 31 2 : - ~ 4.7 g/cm 3 (Earth’s mantle): E res ~ 6.4 GeV - ~ 10.8 g/cm 3 (Earth’s outer core): E res ~ 2.8 GeV Resonance energy: MH
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17 Mantle-core-mantle profile Probability for FNAL-PINGU (numerical) (Parametric enhancement: Akhmedov, 1998; Akhmedov, Lipari, Smirnov, 1998; Petcov, 1998) Core resonance energy Mantle resonance energy Inter- ference Threshold effects expected at: 2 GeV4-5 GeV Beam energy and detector threshold have to pass ~ 2 GeV! Naive L/E scaling does not apply! Parametric enhancement through mantle-core-mantle profile of the Earth. Unique physics potential! !
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Neutrino beam to PINGU? Beams and detector parameterization
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19 There are three possibilities to artificially produce neutrinos Beta decay: Example: Nuclear reactors, Beta beams Pion decay: From accelerators: Muon decay: Muons produced by pion decays! Neutrino Factory Muons, neutrinos Possible neutrino sources Protons TargetSelection, focusing Pions Decay tunnel Absorber Neutrinos Superbeam
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20 Considered setups (for details: Tang, Winter, JHEP 1202 (2012) 028, arXiv:1110.5908; Sec. 3) Single baseline reference setups: Idea: similar beam, but detector replaced by PINGU/MICA [need to cover ~ 2 – 5 GeV]: L [km]
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21 Want to study e - oscillations Beta beams: In principle best choice for PINGU (need muon flavor ID only) Superbeams: Need (clean) electron flavor sample. Difficult? Neutrino factory: Need charge identification of + and - (normally) Oscillation channels
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22 PINGU fiducial volume? In principle: Mton-size detector in relevant ranges: Unclear how that evolves with cuts for flavor-ID etc. (background reduction); MICA even larger? Use effective detector parameterization to study requirements: E th, V eff, E res (Tang, Winter, JHEP 1202 (2012) 028; V eff somewhat smaller than J. Koskinen ‘s current results) E th V eff E res ( E) = E
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23 Detector paramet.: mis-ID misIDtracks << misID <~ 1 ? (Tang, Winter, JHEP 1202 (2012) 028) misID: fraction of events of a specific channel mis-identified as signal
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Detector requirements for large 13
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25 Superbeam (LBNE-like) Mass hierarchy measurement very robust (even with large misID and total rates only possible) (Tang, Winter, JHEP 1202 (2012) 028) (misIDtracks = 0.01) Fraction of CP
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26 Low-intensity alternative? Use existing equipment, new beam line Here: use most conservative assumption NuMI beam, 10 21 pot (total), neutrinos only [compare to LBNE: 22+22 10 20 pot without Project X ~ factor four higher exposure than the one considered here] (FERMILAB-PROPOSAL-0875, NUMI-L-714) Low intensity allows for shorter decay pipe (rough estimate: ~ 100 m for 700kW beam) Advantage: Peaks in exactly the right energy range for the parametric enhancement due to the Earth‘s core (Tang, Winter, JHEP 1202 (2012) 028)
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27 Detector parameterization Challenges: Electron flavor ID Systematics (efficiency, flux normalization near detector?) Energy resolution Make very (?) conservative assumptions here: Fraction of mis-identified muon tracks (muon tracks may be too short to be distinguished from signal) ~ 20% Irreducible backgrounds (zeroth order assumption!): Intrinsic beam background Neutral current cascades cascades (hadronic and electromagnetic cascades indistinguishable) Systematics uncorrelated between signal and background No energy resolution (total rates only) (for details on parameterization: Tang, Winter, JHEP 1202 (2012) 028)
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28 Event rates Normal hier.Inv. hierarchy Signal156054 Backgrounds: e beam 3959 Disapp./track mis-ID511750 appearance 34 Neutral currents2479 Total backgrounds30323292 Total signal+backg.45923346 (Daya Bay best-fit) >18 (stat. only)
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29 NuMI-like beam to PINGU? Very robust mass hierarchy measurement (as long as either some energy resolution or control of systematics); track mis-identification maybe too conservative (Daya Bay best-fit; current parameter uncertainties, marginalized over) GLoBES 2012 All irreducible backgrounds included
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30 Probabilities: CP -dependence There is a rich CP -phenomenology: (probably works for NH only!?) NH
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31 Upgrade path towards CP ? Measurement of CP in principle possible, but challenging Requires: Electromagnetic shower ID (here: 1% mis-ID) Energy resolution (here: 20% x E) Maybe: volume upgrade (here: ~ factor two) Project X Performance and optimization of PINGU, and possible upgrades (MICA, …) require further study = LBNE + Project X! (Tang, Winter, JHEP 1202 (2012) 028) same beam to PINGU
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32 Beta beam Similar results for mass hierarchy measurement (easy) CPV less promising: long L, asymmetric beam energies (at least in CERN-SPS limited case ~656 for 8 B and =390 for 8 Li) although moderate detector requirements (Tang, Winter, JHEP 1202 (2012) 028) (misID ~ 0.001, E th =2 GeV, E res =50% E, V eff =5 Mt)
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33 Neutrino factory No magnetic field, no charge identification Need to disentangle P e and P by energy resolution: (from: Tang, Winter, JHEP 1202 (2012) 028 ; for non-magnetized detectors, see Huber, Schwetz, Phys. Lett. B669 (2008) 294) )
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34 contamination Challenge: Reconstructed at lower energies! (Indumathi, Sinha, PRD 80 (2009) 113012; Donini, Gomez Cadenas, Meloni, JHEP 1102 (2011) 095) Choose low enough E to avoid Need event migration matrices (from detector simulation) for reliable predictions! (neutral currents etc) (sin 2 2 13 =0.1) (Tang, Winter, JHEP 1202 (2012) 028)
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35 Matter density measurement Example: LBNE-like Superbeam Precision ~ 0.5% (1 ) Highly competitive to seismic waves (seismic shear waves cannot propagate in the liquid core!) (Tang, Winter, JHEP 1202 (2012) 028)
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LBNE reconfiguration (some personal comments) Thanks discussions with: A. de Gouvea, F. Halzen, J. Hylen, B. Kayser, J. Kopp, S. Parke, PINGU collaboration, …
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37 ~ 600M$
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38 Landscape (before reconfiguration) LBNE one out of many options to measure CPV Can this reach be matched in a phased approach? How can one define a truly unique experiment for <= 600M US$? How would one react if T2HK happens? (P. Huber)
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39 Reconfiguration options? … or how to spend 600 M$ New detector, existing beam line MINOS site (L=735 km) NOvA site (L=810 km) New site? New (smaller) detector, new beam line (~300 M$) Smaller detector in Homestake (L=1300 km) Surface detector at Homestake (L=1300 km) New beam line (<= 550 M$?), (then) existing detector PINGU (L=11620 km) …… Idea ~ 2 weeks old
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40 Best physics concept? (Barger, Huber, Marfatia, Winter, PRD 76 (2007) 053005) NuMI beam line New beam line Homestake, on-axis
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41 Conclusion: LBNE – smaller version? How many does one need? Combination of experiments tolerable as physics result? MH, 5 This is what T2HK cannot do This is what T2HK can also do
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42 Conclusions: FNAL-PINGU? FNAL-PINGU Megaton-size ice detector as upgrade of DeepCore with lower threshold; very cost-efficient compared to liquid argon, water Unique mass hierarchy measurement through parameteric enhancement; proton beams from main injector may just have right energy In principle, MH even with counting experiment measurable (compared to MH determination using atmospheric neutrinos) Challenges on beam side (questions from PINGU meeting): Tilt of beam line – feasibility, cost? Near detector necessary? Maybe not, if 10% systematics achievable … Beam bunching (to reduce atmospheric backgrounds)? NB: very low exposure required for MH; shorter decay pipe, one horn only, …? Perspectives CP violation challenging (requires energy resolution, flavor identification), but not in principle excluded; needs further study on detector side Measurement of Earth‘s core density, in principle, possible (Tang, Winter, JHEP 1202 (2012) 028) Upgrades of PINGU discussed (MICA) Truly unique and spectacular long-baseline experiment with no other alternative proposed doing similar physics!? The LBNE alternative if T2HK is going to be funded?
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BACKUP
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44 NOvA+INO (atm.)? (Blennow, Schwetz, arXiv:1203.3388) MH, 3
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45 NF: Precision measurements? … only if good enough energy resolution ~ 10% E and misID (cascades versus tracks) <~ 1% can be achieved! Requires further study … (Tang, Winter, JHEP 1202 (2012) 028)
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46 Beams: Appearance channels (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Akhmedov et al, 2004) Antineutrinos: Magic baseline: L~ 7500 km: Clean measurement of 13 (and mass hierarchy) for any energy, value of oscillation parameters! (Huber, Winter, 2003; Smirnov 2006) In combination with shorter baseline, a wide range of very long baseline will do! (Gandhi, Winter, 2006; Kopp, Ota, Winter, 2008)
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47 Quantification of performance Example: CP violation discovery Sensitive region as a function of true 13 and CP CP values now stacked for each 13 Read: If sin 2 2 13 =10 -3, we expect a discovery for 80% of all values of CP No CPV discovery if CP too close to 0 or No CPV discovery for all values of CP 33 ~ Precision in quark sector! Best performance close to max. CPV ( CP = /2 or 3 /2)
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48 Effective volume Difference E th = 2 GeV, V eff =5 Mt to actual (energy-dependent) fiducial volume: (Tang, Winter, JHEP 1202 (2012) 028)
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49 Note: Pure baseline effect! A 1: Matter resonance VL baselines (1) (Factor 1) 2 (Factor 2) 2 (Factor 1)(Factor 2) Prop. To L 2 ; compensated by flux prop. to 1/L 2
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50 Factor 1: Depends on energy; can be matter enhanced for long L; however: the longer L, the stronger change off the resonance Factor 2: Always suppressed for longer L; zero at “magic baseline” (indep. of E, osc. Params) VL baselines (2) ( m 31 2 = 0.0025, =4.3 g/cm 3, normal hierarchy) Factor 2 always suppresses CP and solar terms for very long baselines; note that these terms include 1/L 2 -dep.!
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