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Impact of large 13 on long- baseline measurements at PINGU PINGU Workshop Erlangen university May 5, 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 Matter density measurement? 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 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) MH?
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6 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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7 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; Smirnov‘s talk! However: also long-baseline proposals! (LBNO: superbeam ~ 2200 km – LAGUNA design study; CERN-SuperK ~ 8870 km – Agarwalla, Hernandez, arXiv:1204.4217) Perhaps different facilities for MH and CPV proposed/discussed?
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Oscillation physics using a core-crossing baseline
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9 Matter profile of the Earth … as seen by a neutrino (PREM: Preliminary Reference Earth Model) Core Inner core
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10 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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11 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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12 Parameter mapping (two flavors) 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 ~ 7 GeV - ~ 10.8 g/cm 3 (Earth’s outer core): E res ~ 3 GeV Resonance energy: MH
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13 Mantle-core-mantle profile Probability for CERN-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 GeV5 GeV10 GeV Beam energy and detector thresh. have to pass these! Is that part useful? Challenge: Relative size of CP -terms smaller for longer L
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Neutrino beam to PINGU? Beams and detector parameterization
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15 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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16 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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17 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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18 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 Jason‘s current results) E th V eff E res ( E) = E
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19 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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21 Superbeam Mass hierarchy measurement very robust (even with large misID and total rates only possible) Even with much smaller-scale beam? Existing equipment, such as CNGS? NuMI? CPV not promising (requires flavor mis-ID at the level of 1%, V eff > 5 Mt, E res = 0.2 E or better) (Tang, Winter, JHEP 1202 (2012) 028) (misIDtracks = 0.01) Fraction of CP
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22 NuMI-like beam to PINGU? Difference to atmospherics: can even live without energy resolution and cascade ID (NC and added) (if some track ID and systematics controlled) NuMI
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23 Beta beam Similar results for mass hierarchy measurement (easy) CPV not so 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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24 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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25 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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26 Precision measurements? … only if good enough energy resolution ~ 10% E and misID (cascades versus tracks) <~ 1% can be achieved! (Tang, Winter, JHEP 1202 (2012) 028)
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The BONUS program: Matter density measurement of the Earth‘s core?
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28 Example: 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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29 Conclusions [my personal view] Superbeams Electron sample (cascades) probably contaminated by other flavors; therefore precision measurements unlikely Interesting option: Use more or less existing equipment for a mass hierarchy measurement? (e.g. CNGS/MINOS with new beam line?) Bonus: matter density measurement of Earth‘s core Unique experiment as low-budget alternative to LBNE? Neutrino factory Energy resolution critical, since non-magnetized detector Detector simulation needed to produce event migration matrices for reliable conclusions if E res ~ 10% E achievable? Beta beams Intrinsically best-suited for PINGU/MICA: flavor-clean beam, requires muon neutrino flavor-ID However: need high intensity, high energy 8 B- 8 Li setups for reasonable sensitivities; there are better ways to build a beta beam for large 13 to do both MH+CPV
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30 Statement of PINGU collaboration needed now (or never)!?
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BACKUP
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32 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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33 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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34 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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35 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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36 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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