TeVPA 2012 TIFR Mumbai, India Dec 10-14, 2012 Walter Winter Universität Würzburg Neutrino physics with IceCube DeepCore-PINGU … and comparison with alternatives TexPoint fonts used in EMF: AAAAA A A A

2 Contents  Introduction  Oscillation physics with Earth matter effects  Mass hierarchy determination with PINGU  Neutrino beam to PINGU?  Atmospheric neutrinos  Comparison with alternatives, and outlook  Summary

3 Atmospheric neutrino anomaly  The rate of neutrinos should be the same from below and above  But: About 50% missing from below  Neutrino change their flavor on the path from production to detection: Neutrino oscillations (Super-Kamiokande: “Evidence for oscillations of atmospheric neutrinos”, 1998)

4  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 ; KamLAND 2002; Daya Bay, RENO 2012)

5 (also: T2K, Double Chooz, RENO) (short baseline)

6 Consequences of large  13   13 to be well measured by Daya Bay  Mass hierarchy: 3  discovery for up to 40% of all  CP possible iff ProjectX, possibly until 2025  CP violation measurement extremely difficult Need new facility! Huber, Lindner, Schwetz, Winter, 2009

Oscillation physics with Earth matter effects

8 Matter profile of the Earth … as seen by a neutrino (PREM: Preliminary Reference Earth Model) Core Inner core (not to scale)

9 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)

10 Parameter mapping … for 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 ~ 6.4 GeV -  ~ 10.8 g/cm 3 (Earth’s outer core): E res ~ 2.8 GeV Resonance energy:  MH

11 Mantle-core-mantle profile  Probability for L=11810 km (numerical) (Parametric enhancement: Akhmedov, 1998; Akhmedov, Lipari, Smirnov, 1998; Petcov, 1998) Core resonance energy Mantle resonance energy Param. enhance- ment Threshold effects expected at: 2 GeV4-5 GeV Naive L/E scaling does not apply! Parametric enhancement through mantle-core-mantle profile of the Earth. Unique physics potential! !

Mass hierarchy determination with PINGU

13 What is PINGU? (“Precision IceCube Next Generation Upgrade“)  Fill in IceCube/DeepCore array with additional strings  Drive threshold to lower energies  LOI in preparation  Modest cost ~30-50M$ (dep. on no. of strings)  Two season deployment anticipated: 2015/2016/2017 (PINGU, 12/2012)

14 PINGU fiducial volume?  A ~ Mt fiducial mass for superbeam produced with FNAL main injector protons (120 GeV)  Multi-Mt detector for E > 10 GeV  atmospheric neutrinos  Fid. volume depends on trigger level (earlier V eff higher, which is used for following analyses!) LBNE-like beam Atm. neutrinos (PINGU, 12/2012)

15 Mass hierarchy measurement: statistical significance (illustrated) Source (spectrum, solid angle) Osc. effect (in matter) Detector mass Cross section ~ E Atmospheric neutrinos arXiv: Beams M. Bishai x > 2 GeV > 5 GeV xx Core res. Measurement at threshold  application rather for future upgrades: MICA?

16 Beams to PINGU?  Labs and potential detector locations (stars) in “deep underground“ laboratories: (Agarwalla, Huber, Tang, Winter, 2010) FNAL-PINGU: km CERN-PINGU: km RAL-PINGU: km JHF-PINGU: km All these baselines cross the Earth‘s outer core!

17 Example: “Low-intensity“ superbeam?  Here: use most conservative assumption NuMI beam, pot (total), neutrinos only [compare to LBNE: pot without Project X ~ factor four higher exposure than the one considered here] (FERMILAB-PROPOSAL-0875, NUMI-L-714)  Low intensity may allow for shorter decay pipe  Advantage: Peaks in exactly the right energy range for the parametric enhancement  Include all irreducible backgrounds (intrinsic beam, NC, hadronic cascades), 20% track mis-ID M. Bishai

18 Event rates Normal hier.Inv. hierarchy Signal Backgrounds: e beam 3959 Disapp./track mis-ID  appearance 34 Neutral currents2479 Total backgrounds Total signal+backg (for V eff 03/2012) >18  (stat. only)

19 Mass hierarchy with a beam  Very robust mass hierarchy measurement (as long as either some energy resolution or control of systematics) (Daya Bay best-fit; current parameter uncertainties included; based on Tang, Winter, JHEP 1202 (2012) 028 ) GLoBES 2012 All irreducible backgrounds included

20 Atmospheric neutrinos  Neutrino source available “for free“  Source not flavor- clean  different channels contribute and mask effect  Power law spectrum A. Smirnov  Many different baselines at once, weighted by solid angle  Detector: angular+energy resolution required! arXiv: Akhmedov, Razzaque, Smirnov, 2012

21 Mass hierarchy with atmospheric neutrinos Akhmedov, Razzaque, Smirnov, 2012  Statistical significance depends on angular and energy resolution  About 3-10  likely for reasonable values  Final proof of principle will require event reconstruction techniques (in progress)

Comparison with alternatives … and outlook

23 Mass hierarchy  PINGU completed by beginning of 2017?  No “conventional“ atm. neutrino experiment could be built on a similar timescale or at a similar cost  Bottleneck: Cavern!  3 , Project X and T2K with proton driver, optimized neutrino-antineutrino run plan Huber, Lindner, Schwetz, Winter, JHEP 11 (2009) 44 PINGU ? Akhmedov, Razzaque, Smirnov, 2012; v5 33

24 Probabilities:  CP -dependence  There is rich  CP -phenomenology: NH L=11810 km

25 Upgrade path towards  CP ?  Measurement of  CP in principle possible, but challenging  Wish list:  Electromagnetic shower ID (here: 1% mis-ID)  Energy resolution (here: 20% x E)  Maybe: volume upgrade (here: ~ factor two)  Project X  Currently being discussed in the context of further upgrades - MICA; requires further study  PINGU as R&D exp.? = LBNE + Project X! Tang, Winter, JHEP 1202 (2012) 028 same beam to PINGU

26 Matter density measurement Example: LBNE-like Superbeam  Precision ~ 0.5% (1  ) on core density  Complementary to seismic waves (seismic shear waves cannot propagate in the liquid core!) from: Tang, Winter, JHEP 1202 (2012) 028; see also: Winter, PRD72 (2005) ; Gandhi, Winter, PRD75 (2007) ; Minakata, Uchinami, PRD 75 (2007)

27 Conclusions: 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 MSW effect in Earth matter  Atmospheric neutrinos:  Neutrino source for free, many different baselines  Requires energy and angular resolution (reconstruction work in progress)  PINGU to be the first experiment to discover the mass hierarchy at 3-5  ?  Neutrino beam:  Requires dedicated source, with relatively low intensity  Proton beams from FNAL main injectior have just right energy to hit mantle- core-mantle parameteric enhancement region  Even possible as counting experiment, no angular resolution needed  Beyond PINGU: CPV and matter density measurements perhaps possible with beam to even denser array (MICA)?  PINGU as R&D experiment; worth further study!  Technology also being studied in water  ORCA

BACKUP

29 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

30 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 1.0?

31 Want to study e -  oscillations with different sources:  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) Detector requirements  13,  CP

32 Detector parameterization (low intensity superbeam)  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)

33  Many proposals for measuring CP violation with a neutrino beam  Require all a dedicated (new) detector + control of systematics Measurement of  CP ? Coloma, Huber, Kopp, Winter, 2012