1. Looking for New Physics in Neutrino Experiments Morgan Wascko Imperial College London

2. 11 January, 2007 Morgan Wascko, Aspen 2007Page 2 The Open Questions of Neutrino Physics 1.What else can neutrinos reveal beyond the Standard Model? 2.How does the mixing really work? 3.What is the nature of neutrino mass? 4.What do neutrinos tell us about cosmology? (I won’t actually cover this today.)

3. 11 January, 2007 Morgan Wascko, Aspen 2007Page 3 Comment on the open questions The open questions I listed are all motivated by experimental results –You might say that some results are more compelling than others, but they’re all worth pursuing Answering these questions will at least give us a more precise picture of neutrino masses and mixings This is so far the only observation of physics beyond the Standard Model If nature is kind, the next generation of neutrino experiments will tear the roof off of the Standard Model!

4. 11 January, 2007 Morgan Wascko, Aspen 2007Page 4 Comment on the open questions The open questions I listed are all motivated by experimental results –You might say that some results are more compelling than others, but they’re all worth pursuing Answering these questions will at least give us a more precise picture of neutrino masses and mixings This is so far the only observation of physics beyond the Standard Model If nature is kind, the next generation of neutrino experiments will tear the roof off of the Standard Model!

5. 11 January, 2007 Morgan Wascko, Aspen 2007Page 5 The Open Questions of Neutrino Physics 1.What else can neutrinos reveal beyond the Standard Model? A.How many generations? 2.How does the mixing really work? 3.What is the nature of neutrino mass?

6. 11 January, 2007 Morgan Wascko, Aspen 2007Page 6 Nu Oscillation HOWTO Neutrinos oscillate their flavour with distance travelled (time) Ideally, one measures neutrino flux at birth in a near detector Then measure flux after ’s have time to oscillate Can measure appearance and disappearance MINOS near detector data

7. 11 January, 2007 Morgan Wascko, Aspen 2007Page 7 Nu Oscillation HOWTO Neutrinos oscillate their flavour with distance travelled (time) Ideally, one measures neutrino flux at birth in a near detector Then measure flux after ’s have time to oscillate Can measure appearance and disappearance MINOS far detector data

8. 11 January, 2007 Morgan Wascko, Aspen 2007Page 8 Neutrino Oscillations Current Situation Three oscillation signals Allowed regions indicated – Note: The true answers are actually single points! Only mass differences, not absolute scale For 3 neutrinos, should find:  m 2 12 +  m 2 23 =  m 2 13 Reactor Limit LSND    e Sorel

9. 11 January, 2007 Morgan Wascko, Aspen 2007Page 9 LSND Signal & MiniBooNE LSND observed 3.8  excess –     e Taken with atmospheric and solar oscillations, the oscillation hypothesis implies additional neutrino flavours –Sterile! MiniBooNE is sensitive to the same parameter space See J. Monroe’s MiniBooNE talk in today’s evening session

10. 11 January, 2007 Morgan Wascko, Aspen 2007Page 10 Post MiniBooNE If MiniBooNE sees a signal, build BooNE –Second detector –Precise measurement Near term: ICARUS –LAr detector in Gran Sasso –Great  / e PID Longer Term: –OscSNS at Oak Ridge –T2K 2km detector Future currently uncertain –NOvA near detector

11. 11 January, 2007 Morgan Wascko, Aspen 2007Page 11 Post MiniBooNE If MiniBooNE sees a signal, build BooNE –Second detector –Precise Measurement Near term: ICARUS –LAr detector in Gran Sasso –Great  / e PID Longer Term: –OscSNS at Oak Ridge –T2K 2km detector Future currently uncertain –NOvA near detector

12. 11 January, 2007 Morgan Wascko, Aspen 2007Page 12 Sterile Neutrinos: Solar Hints MSW model predicts upturn in spectrum at low energy SNO and Super-K data do not show it! Sterile neutrino mixing models give best global fits to data Reducing threshold should resolve the question SNO is doing just that with LETA Smirnov

13. 11 January, 2007 Morgan Wascko, Aspen 2007Page 13 The Open Questions of Neutrino Physics 1.What else can neutrinos reveal beyond the Standard Model? A.How many generations? (MiniBooNE) 2.How does the mixing really work? A.Is  23 maximal? B.What is the value of  13 ? C.Mass hierarchy? D.Do leptons violate CP? 3.What is the nature of neutrino mass? Accelerator neutrino beams And reactor neutrinos

14. 11 January, 2007 Morgan Wascko, Aspen 2007Page 14 Neutrino Flavour Mixing ATMOSPHERIC SK, K2K, MINOS  23 =~45   m 2 23 = ~2.5E-3 eV 2 CROSS MIXING CHOOZ, Bugey  13 <~12   is unknown SOLAR SNO, others, KamLAND  12 =~32   m 21 2 = ~8E-5 eV 2 Flavour Mass

15. 11 January, 2007 Morgan Wascko, Aspen 2007Page 15 Neutrino Flavour Mixing ATMOSPHERIC SK, K2K, MINOS  23 =~45   m 2 23 = ~2.5E-3 eV 2 SOLAR SNO, others, KamLAND  12 =~32   m 21 2 = ~8E-5 eV 2 Flavour Mass 0.7 0.7 <0.12 0.5 -0.5 0.7 -0.5 0.5 0.7 Neutrino mixing matrix values are large! But so are the uncertainties…

16. 11 January, 2007 Morgan Wascko, Aspen 2007Page 16 Improving Precision for Oscillations: Off-Axis Beams Use kinematics of pion decay to tune the neutrino energy Flux peak at target energy for desired value of L/E –L is often constrained by geographic considerations…

17. 11 January, 2007 Morgan Wascko, Aspen 2007Page 17 T2K: Tokai-to-Kamioka Start with world’s largest detector: Super-Kamiokande –Super-K III (50kt) is running now Build new neutrino beam –J-PARC facility in Tokai Off-axis beam to Super-K –L = 295 km –E = 0.7 GeV Near detector at 280m to constrain beam flux Beam should be running in April 2009 Expect 5E21 POT in 5 years Nishikawa

18. 11 January, 2007 Morgan Wascko, Aspen 2007Page 18 T2K: Tokai-to-Kamioka Start with world’s largest detector: Super-Kamiokande –Super-K III is running now Build new neutrino beam –J-PARC facility in Tokai Off-axis beam to Super-K –L = 295 km –E = 0.7 GeV Near detector at 280m to constrain beam flux Beam should be running in April 2009 Expect 5E21 POT in 5 years

19. 11 January, 2007 Morgan Wascko, Aspen 2007Page 19 T2K: Tokai-to-Kamioka Start with world’s largest detector: Super-Kamiokande –Super-K III is running now Build new neutrino beam –J-PARC facility in Tokai Off-axis beam to Super-K –L = 295 km –E = 0.7 GeV Near detector at 280m to constrain beam flux Beam should be running in April 2009 Expect 5E21 POT in 5 years

20. 11 January, 2007 Morgan Wascko, Aspen 2007Page 20 NO A: (NuMI Off-axis e Appearance) Start with world’s (current) most powerful beam –NuMI facility at Fermilab Build new detectors in off- axis locations –FNAL & Ash River, MN (810 km) 25 kton far detector Program of beam upgrades –Goal: 6E21POT –50%, 50%  NOvA turn-on as early as 2011 —NUMI-On-axis beam —14mrad off-axis beam (no oscillation) Mualem

21. 11 January, 2007 Morgan Wascko, Aspen 2007Page 21 NO A: (NuMI Off-axis e Appearance) Start with world’s (current) most powerful beam –NuMI facility at Fermilab Build new detectors in off- axis locations –FNAL & Ash River, MN (810 km) 25 kton far detector Program of beam upgrades –Goal: 6E21POT –50%, 50%  NOvA turn-on as early as 2011

22. 11 January, 2007 Morgan Wascko, Aspen 2007Page 22  disappearance T2K and NOvA have same goal for  23 –  (sin 2 2  23 ) ~ 0.01 Problem: Background estimate uncertainties due to neutrino cross section are large Example: T2K uncertainties in atmospheric parameters –stat. Only – (nQE/QE)= 5% – (nQE/QE)=20% Need better data for physics input! Is  23 Maximal? NovA (sin 2 2)(m2)(m2) Hiraide Mualem

23. 11 January, 2007 Morgan Wascko, Aspen 2007Page 23 Reducing Cross Section Uncertainties Two FNAL experiments embarking on campaigns to bring  uncertainties down to needed levels Both experiments will have high statistics data sets with fine-grained detectors SciBooNE (E-954) –Near detector in Booster beam –Energy perfect for T2K –Antineutrino data! –Will be running this spring (07) MINER A (E-938) –Near detector in NuMI beam –Wide range of energies –Different nuclear targets –Data in 2009   Events K. Hiraide SciBooNE detector assembly MINERvA design MINERvA detector protoyping

24. 11 January, 2007 Morgan Wascko, Aspen 2007Page 24 Measuring  13 : Current Situation Reminder:  13 is how CP violation enters the mixing matrices –We hope it’s large enough! To measure  13, must observe e appearance Want sensitivities to sin 2 2  13 >0.01 Most troublesome BG: mis-identified NC  0 –SciBooNE and MINERvA data will solve that! Accelerator experiments have ambiguities in measuring  13 Reactor Limit LSND    e Sorel

25. 11 January, 2007 Morgan Wascko, Aspen 2007Page 25 Measuring  13 : Accelerators Reminder:  13 is how CP violation enters the mixing matrices –We hope it’s large enough! To measure  13, must observe e appearance Want sensitivities to sin 2 2  13 >0.01 Most troublesome BG: mis-identified NC  0 –SciBooNE and MINERvA data will solve that! Accelerator experiments have ambiguities in measuring  13 E rec  m 2 =2.5x10 -3 eV 2,sin 2 2  13 =0.1 events/22.5kt/5yrs T2K Simulated e Appearance Signal Mine

26. 11 January, 2007 Morgan Wascko, Aspen 2007Page 26 Measuring  13 : Accelerators —Statistics only —  (BG) = 10% —  (BG) = 20% Reminder:  13 is how CP violation enters the mixing matrices –We hope it’s large enough! To measure  13, must observe e appearance Want sensitivities to sin 2 2  13 >0.01 Most troublesome BG: mis-identified NC  0 –SciBooNE and MINERvA data will solve that! Accelerator experiments have ambiguities in measuring  13 T2K Simulated e Appearance Sensitivity Mine

27. 11 January, 2007 Morgan Wascko, Aspen 2007Page 27 Measuring  13 : Accelerators Reminder:  13 is how CP violation enters the mixing matrices –We hope it’s large enough! To measure  13, must observe e appearance Want sensitivities to sin 2 2  13 >0.01 Most troublesome BG: mis-identified NC  0 –SciBooNE and MINERvA data will solve that! Accelerator experiments have ambiguities in measuring  13 –Tied to atmospheric parameters –CP violation?

28. 11 January, 2007 Morgan Wascko, Aspen 2007Page 28 Measuring  13 : Reactors Use near/far detectors to search for  e disappearance Use inverse  decay –Well know cross section –Great BG rejection  13 2 Reactor Near Detector e e ? Far Detector

29. 11 January, 2007 Morgan Wascko, Aspen 2007Page 29 Measuring  13 : Reactors Double CHOOZ –Build two detectors at CHOOZ site –First data in 2008 Daya Bay –Two detectors at Daya Bay reactor site in China –First data in 2011 Unambiguous sensitivity to sin 2 2  13 –DC: ~0.03 –DB: ~0.01 Double CHOOZ (France) Daya Bay (China)

30. 11 January, 2007 Morgan Wascko, Aspen 2007Page 30 Measuring  13 : Reactors Double CHOOZ –Build two detectors at CHOOZ site –First data in 2008 Daya Bay –Two detectors at Daya Bay reactor site in China –First data in 2011 Unambiguous sensitivity to sin 2 2  13 –DC: ~0.03 –DB: ~0.01 Double CHOOZ Daya Bay Wang Tonazzo

31. 11 January, 2007 Morgan Wascko, Aspen 2007Page 31 Mass Hierarchy Is m 3 >m 2 ? –  m 2 atm ~10 -3 –  m 2 sol ~10 -5 e and  e scatter with different rates in matter –Raises effective mass of e –Lowers effective mass of  e Changes oscillation probabilities! –P(    e )  P (   e ) Diagram taken from Boris Kayser e W e

32. 11 January, 2007 Morgan Wascko, Aspen 2007Page 32 Mass Hierarchy Matter effects change oscillation probabilities! –P(    e )  P (   e ) –If neutrinos oscillate more, it’s a normal hierarchy –If antineutrinos oscillate more, it’s an inverted hierarchy Effect grows with energy Two experiments at fixed L/E –R>1  Normal –R<1  Inverted NOvA, with higher L and E, will see a much larger effect than T2K Where S = Sign(  m 2 23 )

33. 11 January, 2007 Morgan Wascko, Aspen 2007Page 33 CP Violation via Oscillation Measurements The Holy Grail of oscillations Further ambiguities: –P(    e )  P (   e ) is also the signature for CP violation Because of the need to know  13, and disentangle matter effects, observing CP violation requires a broad program of experiments –Want a reactor to measure  13 –Want an accelerator that will see matter effects –Want an accelerator that will NOT see matter effects –Need a lot of statistics in both neutrino and antineutrinos!

34. 11 January, 2007 Morgan Wascko, Aspen 2007Page 34 The Open Questions of Neutrino Physics 1.What else can neutrinos reveal beyond the Standard Model? A.How many generations? MiniBooNE 2.How does the mixing really work? A.Is  23 maximal? B.What is the value of  13 ? C.Mass hierarchy? D.Do leptons violate CP? 3.What is the nature of neutrinos? A.What is the absolute scale? B.Majorana or Dirac? C.Are neutrino interactions different? Accelerator neutrino beams And reactor neutrinos

35. 11 January, 2007 Morgan Wascko, Aspen 2007Page 35 Absolute Mass Scale Why so light? Can use kinematics to determine the mass of neutrinos directly – e : m < ~2 eV (  decay) –  : m < 0.19 MeV (  decay) –  : m < 18.2 MeV (  decay (hadronic)) Best limits come from tritium decay 2 main experimental techniques –Spectrometers Measure energy of emitted electron –Calorimeters Measure heat increase due to emitted electron

36. 11 January, 2007 Morgan Wascko, Aspen 2007Page 36 Tritium Decay Experiments Measure tritium decay spectrum Look at endpoint for evidence of neutrino mass Detector resolution sets mass sensitivity 3 H  3 He   e Elliot Bornschein

37. 11 January, 2007 Morgan Wascko, Aspen 2007Page 37 Source Electron analyzer Electron counter T2T2 Tritium Decay: Spectrometers Best existing limits come from spectrometer experiments –“MAC-E filter” Magnetic Adiabatic Collimation with Electrostatic Filter –Integrating high pass filter Troitsk –m 2 ( ) = -2.3 ± 2.5 ± 2.0 eV 2 m( )< 2.2 eV (95% C.L.) Mainz –m 2 ( ) = -0.6 ± 2.2 ± 2.1 eV 2 m( )< 2.3 eV (95% C.L.) Troitsk Detector Mainz Detector

38. 11 January, 2007 Morgan Wascko, Aspen 2007Page 38 Next Generation Tritium Decay: KATRIN Combine best of Mainz and Troitsk techniques Much larger experiment! Aim: improve mass reach by one order of magnitude –sensitivity m( ) < 0.2 eV (90% CL) –discovery potential m( ) = 0.35 eV (5  ) Will observe Heidelberg- Moscow size mass neutrino if it exists! Installation in progress… 70 m

39. 11 January, 2007 Morgan Wascko, Aspen 2007Page 39

40. 11 January, 2007 Morgan Wascko, Aspen 2007Page 40 Majorana Mass? Use rare nuclear transitions that emit 2  s “Line” detected at the endpoint energy indicates neutrinoless double  Can only happen if neutrinos are Majorana particles 2 primary experimental approaches: –Source = Detector (SED) –Tracker-Calorimeters (TC) Search for decays; limits on half-life for decays yield limits on neutrino mass P P n n Left C e1e1 e2e2 Thomas Gomez Cadenas

41. 11 January, 2007 Morgan Wascko, Aspen 2007Page 41 Experimental Techniques 1: SED Examples: –Ge detectors –Bolometers Excellent energy resolution, efficiency –No pattern in signal, just energy deposit Limited to single isotope per experiment Dominant BG: External radioactivity Current limits: –CUORICINO: –  m  < (0.18-0.94) eV Cuoricino detector block Cuoricino data Bellini

42. 11 January, 2007 Morgan Wascko, Aspen 2007Page 42 Experimental Techniques 2: TC Example: NEMO-3 “Pattern” signature observed Multiple sources in same detector Modest energy resolution –Resolution of calorimeter –Energy loss in foils Dominant BG: internal double  decays – 82 Se:  m  < 1.3 – 3.6 eV – 100 Mo:  m  < 0.7 – 1.2 eV Expected Reach in 5 years after RadonPurification – 100 Mo:  m  < 0.2 – 0.35 eV – 82 Se:  m  < 0.65 – 1.8 eV Top view Side view 3 m 4 m B (25 G) Source foils + tracker+ calorimeter

43. 11 January, 2007 Morgan Wascko, Aspen 2007Page 43  0 : Possible Signal? Heidelberg-Moscow experiment (Ge) has published a signal claim Enriched 76 Ge detector Total mass 10.9 kg m  = 0.39 eV (95% CL) Controversial Needs confirmation!

44. 11 January, 2007 Morgan Wascko, Aspen 2007Page 44  0 : Next Generation Many next generation experiment proposals 4 that are most on mass shell: –CUORE –EXO –MAJORANA –Super NEMO Broad program using different isotopes Will reach sensitivities sufficient to confirm or refute the Heidelberg- Moscow result Bellini Thomas

45. 11 January, 2007 Morgan Wascko, Aspen 2007Page 45 The NuTev Result Measurement of sin 2  W differs by 3  from SM! –Find: sin 2  W =0.2277  0.0013  0.0009 –cf. sin 2  W =0.2227  0.0003 Precise measurement uses Paschos- Wolfenstein relation Clean and  beams –SSQT Recall LEP result favors N = 2.9841  0.0083

46. 11 January, 2007 Morgan Wascko, Aspen 2007Page 46 Addressing NuTeV Reactor  elastic scattering can be used to measure weak angle Total event rate is sensitive to sin 2  W Normalize rate using inverse  decay –Cross section known to 0.2% Address the mixing angle with neutrinos at low Q 2 Main BGs come from other  decays and neutron spallation e Z ee e W ee Conrad

47. 11 January, 2007 Morgan Wascko, Aspen 2007Page 47 Addressing NuTeV Reactor  elastic scattering can be used to measure weak angle Total event rate is sensitive to sin 2  W Normalize rate using inverse  decay –Cross section known to 0.2% Address the mixing angle with neutrinos at low Q 2 Main BGs come from other  decays and neutron spallation e Z ee e W ee

48. 11 January, 2007 Morgan Wascko, Aspen 2007Page 48 Best Bets For New Physics “Soon” (N.B.: I bet on the USA to win the World Cup) MiniBooNE –Could reveal new generations Neutrinoless Double  Decay –Majorana neutrinos? Absolute mass scale NEW PHYSICS –Maybe not “NEW PHYSICS”, but it would set the scale for neutrino masses