1. The (Past &) Future of Neutrino Physics
Peter Ratoff
Lancaster University

2. The Vitality of Neutrino Physics
SPIRES: find title NEUTRINOS and date XX
> Papers
Reines Cowan
Davis 68
Golden time (1)
Koshiba 87
Golden time (2) ??
EXAMPLES:
1956
discovery of ’s
1968
solar  anomaly
1987
supernova ’s
1998
atmospheric ’s

3. The 1970’s “Gargamelle” Heavy Liquid Bubble Chamber,
PS/SPS Neutrino Beams, CERN, mid-1970’s
The 1970’s
Neutrinos were a very useful tool...
Couple to matter only via weak interactions:
Discovery of weak neutral currents (Z0), 1973
Clean probe of nucleon structure (DIS expts)
... but not particularly interesting themselves!
(i.e. had simple, well understood properties)

4. The neutrino story: 1930’s – 1960’s
“desperate remedy” to
avoid non-conservation
of energy in β decays
Fermi
1933, “neutrino”
& first theory of
weak interactions
Pauli, 1930
The neutrino story: 1930’s – 1960’s
Lederman, Schwartz & Steinberger et al
1962, first accelerator ν beam, discovery of νμ
Reines & Cowan 1956, reactor
beam experiment, discovery of νe

5. ‘Known’ properties of neutrinos in the 1970’s
electrically neutral
spin ½
maximal helicity: LH neutrinos & RH antineutrinos
couple to matter via weak interactions (W/Z)
3 flavours: νe νμ (ντ)
apparently massless (?)

6. SSM prediction = 7.6+1.3-1.1 n .6+1.3-1.1 The solar neutrino anomaly
Homestake Mine, N. Dakota
Davis & Bahcall
νe + 37Cl 37Ar + e-
Rate = 2.56  0.23 SNU
(1SNU = captures/s/target atom )
SSM prediction =   n

7. Observed ratio ~1, Look at zenith angle distributions…

8. SuperKamiokande ... proved that neutrinos have mass Oscillation dip
Decay/decoherence excluded
upgoing
neutrinos
Oscillation
dip
22.5 Ktons
H2O

9. The Sudbury Neutrino Observatory (SNO)
... demonstrated that solar neutrinos change flavour
1 kton D2O
SSM

10. Neutrino Oscillations
If neutrinos have mass, must consider two distinct types of neutrino state :
the eigenstates of the weak interaction: nl = ne, nm, nt
- the flavour eigenstates
the eigenstates of the free particle Hamiltonian: ni = n1, n2, n3
- the mass eigenstates
There is absolutely no reason to believe that these are the same thing.
In general:

11. If neutrinos have mass:
For three neutrinos: Maki, Nakagawa, Sakata & Pontecorvo (MNSP)
Three Angles
In a two-neutrino model, with one angle, the transition probability is

12. If neutrinos have mass:
For three neutrinos:
atmospheric
solar
Two squared-mass differences
- each has a sign

13. If neutrinos have mass:
For three neutrinos:
CP violating phase!

14. KamLAND reactor νe experiment_
KamLAND reactor νe experiment
80% of flux from L = km
1 kton liquid
scintillator
...probes same oscillation parameters as solar ν expts

15. ... KamLAND proved (with other results) that neutrinos oscillate
2005
KamLAND, 2008

16. Long baseline νμ accelerator beam expts: probe same parameters as atmospheric ν
MINOS

17. Consistent picture emerges from all experiments...
Solar/reactor neutrinos
(small mass difference Δm12,
mixing angle θ12 ~ )
Atmospheric/accelerator neutrinos
(large mass difference Δm23,
mixing angle θ23 ~ 450)
Mixing angle θ13 < 140
CHOOZ Reactor ν

18. ...well, a nearly
consistent picture
emerges from all expts!
“LSND region”
– 4th sterile ν ?
Atmos./ Accel. ν expts
Solar/Reactor ν expts

20. The current perspective
(Borexino)

23. Strong UK effort/RAL

24. The 6 ton ND280 Downstream ECAL module, Lancaster, November 2008
Lead & scintillator calorimeter; 33 x 1cm active layers

25.  Use ND280 to study these!

28.  sin22θ13 ~ 0.03 in 5 yrs?

32. Super Beam Experiments: The Incremental Approach
Increased proton driver power
2-4 MW
Targetry
Longer Baseline
FNAL-DUSEL
1300 km
Very deep beam line
600’
Larger Detector
100 KT LAr
300+ KT H2O
Control Systematics
Near Detector
Hadron production
Alan Bross ICHEP July 30, 2008

33. b Beam - CERN baseline scenario:
Flux
6He ( νe):
2.9 × 1018 ion
decays/straight/year
18Ne (νe):
1.1 × 1018 ion
MEMPHYS: 400 kT fiducial water Cherenkov
At Frejus: 130 km
Sensitivities:
Combine with atmospheric neutrino data
Baseline ion energies:
6He: γ = 60
18Ne: γ = 100
Alan Bross ICHEP July 30, 2008

34. Neutrino Factory - International Design Study Baseline
Proton Driver
4 MW, 2 ns bunch
Target, Capture & Phase Rotation
Hg Jet
200 MHz train
Cooling
30 pmm ( ^ )
150 pmm ( L )
Acceleration
103 MeV ® 25 GeV
Storage/Decay ring
MICE
Alan Bross ICHEP July 30, 2008

35. The way ahead?

36. Backup slides

37. 71±5

38. Flavour content of solar flux (SNO + SK)