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Vernon Barger

Physics of Massive Neutrinos. Vernon Barger. NuFact 03. June 5, 2003. Apologies to the many contributors to this science for the omission of references in my talk. 1998–2003 : The Neutrino Revolution. Neutrino flavors oscillate  Neutrinos have mass. Post 2003.

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Vernon Barger

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  1. Physics of Massive Neutrinos Vernon Barger NuFact 03 June 5, 2003 Apologies to the many contributors to this science for the omission of references in my talk

  2. 1998–2003 : The Neutrino Revolution Neutrino flavors oscillate  Neutrinos have mass Post 2003 Era of further discovery and precision lies ahead Fundamental properties of neutrinos within reach Experimental pathways falling in place – Reactors – Off-axis beams – Superbeams – New detector technologies Ultimately and inevitably lead to neutrino factories Goal: unravel the enigma of flavor physics

  3. Neutrino Oscillations flavor states :   = e, , , … mass states : i i = 1, 2, 3, … Vacuum oscillations: For 3 Neutrino Mixing solar unknown Majorana phases atm • 3 mixing angles qa , qs , qx • 3 complex phases d , f2 , f3 (CP) Oscillation probabilities do not depend on f2 , f3

  4. Empirically, the observed oscillations have very different m2 scales and are nearly decoupled Useful effective 2-neutrino approximation when one m2 is dominant # independent m2 = N1

  5. Matter effects on e oscillations e scattering on electrons modifies e oscillation amplitudes and wavelengths in matter Enhancement for m2 > 0 Suppression for m2 < 0 • Crucial for: • solar neutrinos (Ne varies) • long-baselines through Earth (E varies) Analogous matter effects on oscillations to steriles (Ne Ne /2)

  6. e disappear Where we stand today: Evidence of oscillations Atmospheric neutrinos SuperKamiokande, Macro, Soudan, … a ~ 45°, x small Solar neutrinos SNO, SuperK, Gallium, Chlorine e disappear LMA solution matter enhancement, but not resonant s ~ 33° Reactor antineutrinos KamLAND, L ≈ 175 km Confirms LMA KamLAND + Solar further constrains KamLAND massacre: all other solar solutions killed

  7. Solar + KamLAND 2s 3s

  8. e do not disappear Reactor antineutrinos CHOOZ, L ≈ 1 km x ≤ 9° Accelerator antineutrinos LSND, KARMEN LSND ~ 0.5° Limits on nmns atm nens solar nmnm accelerator/reactor at short baselines Barely acceptable global fits in models with sterile neutrinos (tension between atm/solar and SBL) Is cosmology consistent with steriles?

  9. Big Bang Nucleosynthesis (D and 4He) age ≈ few minutes Nn = 1.7–3.0 (2s range) Cosmic Microwave Background (TT power spectrum) age ≈ 380,000 years Nn = 0.9–8.3 (2s range) Neutrino Counting in the Early Universe Photons and light neutrinos dominate the relativistic energy density at very early epochs Extra neutrinos speed up the expansion of the Universe LSND sterile neutrino would be fully thermalized by BBN era. Standard BBN cosmology rejects it.

  10. Houdini’s escape from the BBN constraints A large asymmetry between numbers of eandein the early universeallows extra neutrinos degeneracy parameter e reconciles LSND neutrino with BBN by suppressing its thermalization prior to BBN LSND sterile neutrino implies Huge compared to baryon asymmetry

  11. Neutrino mass and Large Scale Structure in the Universe Even small ∑mn influences power spectrum of galaxy correlations Neutrinos that are more massive cluster more on large scales ∑mn < 0.7 eV 2dF + Lya Forest + WMAP 2dF + WMAP ∑mn < 1 eV LSND Just escapes LSS bounds Final resolution of LSND sterile neutrino awaits miniBooNE

  12. Key Neutrino Issues and how they are being/can be solved Key issue #1: VERIFY OSCILLATIONS / PRECISION “See” the oscillation wiggles versus energy, not just average suppressions P ( ) 2 n m n  d e e s KamLAND 2 m P ( ) d n  n m m a † K2K (250 km) MINOS (730 km) CNGS (730 km) Observe nt appearance 2 P ( ) m n n d  m t a CNGS (OPERA, ICARUS) † †

  13. vs. energy Measure qx from wiggles in P ( )  n n e e KEY ISSUE #2:HOW SMALL IS qx? Proposed reactor experiments with two detectors Short L (< few km) Detector 2 Detector 1 Reactor Sensitivity limit: sin22qx ≈ 0.01 L1 L2 Krasnoyarsk 0.1 km 1 km Kashiwazaki 0.3 km 1.7 km LBNL 1 km 3 km 6 km 7.8 km

  14. detector accelerator qOA≈1–2° Future accelerator experiments Measure qx via appearance: P(nmne) or P(nenm) ≈ sin22qx sin2Da • Off-axis “magic” (JHF, FNAL) ~ monochromatic En , lower backgrounds • Superbeams (upgrades 4–5) Off-axis or Wide-band* (BNL) *binning quasi-elastic events gives equivalent of many narrow-band beams • Neutrino factory stored m+ Golden channel: nenm , n n e m

  15. New detector technologies with 50–500 kton sizes low-Z calorimeter liquid Argon water Cherenkov iron scintillator Approximate discovery reaches in sin22x Current limit 101 Reactor 102 Conventional n-beam 102 Superbeam 3103 NuFact (entry level) 5104 NuFact (high performance) 5105 † How low in sin22qx will we need to go?

  16. KEY ISSUE #3:MASS HIERARCHY? Present data allow 2 mass orderings invertedhierarchy normal hierarchy 2 3 3 2 m 0 d > 1 s 2 m 0 d > a 2 m 0 d < a 2 2 m 0 d > 3 1 † s Grand Unified Theories predict normal hierarchy † † † Earth matter effects • enhance and suppress or vice-versa, depending on sign of • increase with distance • long baselines needed (L > 900 km) to determine hierarchy

  17. Neutrino factory: Hairpin prediction Error bars: 21020 decays/yr for 5 years

  18. Is ? • Both and oscillations must contribute KEY ISSUE #4:CP VIOLATION? (intrinsic) •  measurement depends on x (sinqx eid in V) • Must distinguish intrinsic CP-violation from • fake CP-violation due to matter effects Magic baselines P(nm ne) L/E ≈ 500 km depends only on sind (not cosd) L ≈ 7600 km no d-dependence (no CP-violation) — matter oscillation wavelength

  19. Approximate discovery reaches in sin22qx CP-violation Superbeam 310 3102 NuFact (entry level) 3104 2103 NuFact (high performance) 1104 5104

  20. Must resolve degeneracies that can confuse CP-violating and CP-conserving solutions Parameter sets that give same Eight-fold degeneracy (, x) Best strategies: 1) detector at first oscillation peak 2) long L ( >1000 km) 3) 2 distances

  21. 8-fold parameter degeneracy qx fixed, d varied (, x ) degeneracy P P P

  22. KEY ISSUE #5: 33 MIXING MATRIX UNITARITY? Need to measure all elements ne beams required: only at a neutrino factory channel detect With ne beams can also test time reversal violation P(ne n)  P(n  ne)

  23. KEY ISSUE #6: DIRAC OR MAJORANA? Neutrinoless double-b decay only if neutrinos are Majorana Neutrinoless double-b decay can constrain ∑m (upper and lower bounds)

  24. KEY ISSUE #7: WHAT THEORY? See-Saw mechanism favored NR: singlets in GUT representations GUT models can accommodate all quark and lepton data Make differing predictions for x and CP violation

  25. KEY ISSUE #8: LEPTOGENESIS? Matter-antimatter asymmetry from processes that violate CP in the early universe Baryon number could be associated with violation of lepton number Lepton asymmetry from decays of heavy right-handed neutrinos l l N N  H H

  26. In some models, sign of cosmological baryon number is related to the CP phase in neutrino oscillations These models make testable low energy predictions

  27. SUMMARY Neutrino mass is the first discovery of physics beyond the Standard Model. Oscillation experiments “on the table” have great potential for another breakthrough in measuring qx. The future of oscillation physics is very bright, with Superbeams and longer baselines as the next horizon Whatever experiments accomplish over the next decade, Neutrino Factories will be essential to reconstruct all neutrino mixings with high precision. Combine Neutrino Factory and Superbeam data.

  28. If theoretical prejudices for Grand Unified Theories are correct, neutrino mass owes its origin to right-handed neutrinos with masses near the GUT scale. The sign of the baryon asymmetry may be related to the CP phase in neutrino oscillations. These and other ideas can soon be “put to the test,” at least in the context of models, by measuring qx, sign and d. Neutrino physics has always been full of surprises. There will likely be more surprises to comes!

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