1. Neutrinos – Ghost Particles of the Universe
Georg G. Raffelt
Max-Planck-Institut für Physik, München, Germany

2. Periodic System of Elementary Particles
Quarks
Leptons
Charge /3
Down
Charge
Electron
Charge
e-Neutrino ne e d
Charge /3 Up u
Down
Strange
Bottom
Electron
Muon
Tau
e-Neutrino
m-Neutrino
t-Neutrino nt nm ne e m t d s b
1st Family
2nd Family
3rd Family Up
Charm
Top u c
Neutron
Proton
Strong Interaction (8 Gluons)
Electromagnetic Interaction (Photon)
Weak Interaction (W and Z Bosons)
Gravitation (Gravitons?)
Higgs

3. Where do Neutrinos Appear in Nature?
Nuclear Reactors 
Sun 
Particle Accelerators 
Supernovae
(Stellar Collapse)
SN 1987A 
Earth Atmosphere
(Cosmic Rays) 
Astrophysical
Accelerators 
Earth Crust
(Natural Radioactivity) 
Cosmic Big Bang
(Today 330 n/cm3)
Indirect Evidence

4. Neutrinos from the Sun Solar radiation: 98 % light (photons)
Reaction-
chains
Energy
26.7 MeV
Helium
Solar radiation: 98 % light (photons)
2 % neutrinos
At Earth 66 billion neutrinos/cm2 sec
Hans Bethe ( , Nobel prize 1967)
Thermonuclear reaction chains (1938)

5. Sun Glasses for Neutrinos?
8.3 light minutes
Several light years of lead
needed to shield solar
neutrinos
Bethe & Peierls 1934:
… this evidently means
that one will never be able
to observe a neutrino.

6. First Detection (1954 – 1956) n g Cd p g g 𝝂 𝐞 e + e − Clyde Cowan
(1919 – 1974)
Fred Reines
(1918 – 1998)
Nobel prize 1995
Detector prototype
Anti-Electron
Neutrinos
from
Hanford
Nuclear Reactor
3 Gammas
in coincidence n Cd g
𝝂 𝐞 p g g
e +
e −

7. First Measurement of Solar Neutrinos
Inverse beta decay
of chlorine
600 tons of
Perchloroethylene
Homestake solar neutrino
observatory (1967–2002)

8. 2002 Physics Nobel Prize for Neutrino Astronomy
Ray Davis Jr.
(1914–2006)
Masatoshi Koshiba
(*1926)
“for pioneering contributions to astrophysics, in
particular for the detection of cosmic neutrinos”

9. Elastic scattering or CC reaction
Cherenkov Effect
Cherenkov Ring
Elastic scattering or CC reaction
Light
Electron or Muon
(Charged Particle)
Neutrino
Water

10. Super-Kamiokande Neutrino Detector (Since 1996)

11. Super-Kamiokande: Sun in the Light of Neutrinos
ca. 60,000 solar neutrinos measured in Super-K (1996–2012)

12. Results of Chlorine Experiment (Homestake)
ApJ 496:505, 1998
Theoretical
Expectation
Average
Rate
Average ( )  0.16stat  0.16sys SNU
(SNU = Solar Neutrino Unit = 1 Absorption / sec / 1036 Atoms)
Theoretical Prediction 6-9 SNU
“Solar Neutrino Problem” since 1968

13. Neutrino Flavor Oscillations
Two-flavor mixing
𝜈 𝑒 𝜈 𝜇 = cos 𝜃 sin 𝜃 −sin 𝜃 cos 𝜃 𝜈 1 𝜈 2
Each mass eigenstate propagates as 𝑒 i𝑝𝑧
with 𝑝= 𝐸 2 − 𝑚 2 ≈𝐸− 𝑚 2 2𝐸
Phase difference 𝛿 𝑚 2 2𝐸 𝑧 implies flavor oscillations
Probability 𝜈 𝑒 → 𝜈 𝜇
sin2(2𝜃)
Bruno Pontecorvo
(1913–1993)
Invented nu oscillations z
Oscillation
Length
4𝜋𝐸 𝛿 𝑚 2 =2.5 m 𝐸 MeV eV 𝛿𝑚 2

14. Oscillation of Reactor Neutrinos at KamLAND (Japan)
Oscillation pattern for anti-electron neutrinos from
Japanese power reactors as a function of L/E
KamLAND Scintillator
detector (1000 t)

15. Atmospheric Neutrino Oscillations (1998)
Atmospheric neutrino oscillations show characteristic L/E variation

16. Long-Baseline (LBL) Experiments
K2K Experiment
(KEK to Kamiokande)
measures precise
neutrino oscillation
parameters.
Since then other LBL
Experiments:
Minos (US)
Opera (Europe)
T2K (Japan)
Nova (US)
(construction)

17. Q13 from Reactor Experiments (2012)
4MeV ͞e
sin22θ13 = ± (stat) ± (syst)
Daya Bay (China)
0.113 ± (stat) ± (syst)
Reno (Korea)
0.086 ± (stat) ± (syst)
Double Chooz (Europe)

18. Three-Flavor Neutrino Parameters
Three mixing angles 𝜃 12 , 𝜃 13 , 𝜃 23 (Euler angles for 3D rotation), 𝑐 𝑖𝑗 = cos 𝜃 𝑖𝑗 ,
a CP-violating “Dirac phase” 𝛿, and two “Majorana phases” 𝛼 2 and 𝛼 3
𝜈 𝑒 𝜈 𝜇 𝜈 𝜏 = 𝑐 23 𝑠 − 𝑠 23 𝑐 𝑐 𝑒 −𝑖𝛿 𝑠 −𝑒 𝑖𝛿 𝑠 𝑐 𝑐 12 𝑠 − 𝑠 12 𝑐 𝑒 𝑖 𝛼 𝑒 𝑖 𝛼 𝜈 1 𝜈 2 𝜈 3
39 ∘ < 𝜃 23 < 53 ∘
7 ∘ <𝜃 13 < 11 ∘
33 ∘ < 𝜃 12 < 37 ∘
Relevant for
0n2b decay
Atmospheric/LBL-Beams
Reactor
Solar/KamLAND
Normal
Inverted
Tasks and Open Questions
Precision for all angles
CP-violating phase d ?
Mass ordering ?
(normal vs inverted)
Absolute masses ?
(hierarchical vs degenerate)
Dirac or Majorana ?
Δ 𝑚 2
72–80 meV2 3 m t 2 m e t
Atmosphere
Sun 1 m e t
Atmosphere
2180–2640 meV2 2 m e t
Sun 1 m e t 3 m t

19. Antineutrino Oscillations Different from Neutrinos?
𝝂 𝐞 = 𝑐 12 𝑐 𝝂 𝟏 + 𝑠 12 𝑐 𝝂 𝟐 + 𝑠 13 𝑒 −𝑖𝛿 𝝂 𝟑
𝝂 𝐞 = 𝑐 12 𝑐 𝝂 𝟏 + 𝑠 12 𝑐 𝝂 𝟐 + 𝑠 13 𝑒 +𝑖𝛿 𝝂 𝟑
Dirac phase causes different 3-flavor oscillations
for neutrinos and antineutrinos
𝜈 𝑒 → 𝜈 𝑒
same as 𝜈 𝑒 → 𝜈 𝑒
𝜈 𝑒 → 𝜈 𝜇
𝜈 𝑒 → 𝜈 𝜇
Distance [1000 km] for E = 1 GeV

20. n Neutrino Carabiner Now also in color Greek “nu”
Named for a subatomic particle
with almost zero mass, …
Now also in color n
Greek “nu”

21. “Weighing” Neutrinos with KATRIN
Sensitive to common mass scale m
for all flavors because of small mass
differences from oscillations
Best limit from Mainz und Troitsk
m < 2.2 eV (95% CL)
KATRIN can reach 0.2 eV
Under construction
Data taking to begin 2015/16

22. KATRIN Ante Portas (25 Nov 2006)

23. Weighing Neutrinos with the Universe

24. Cosmological Limit on Neutrino Masses
Cosmic neutrino “sea” ~112 cm-3 neutrinos + anti-neutrinos per flavor
Ω 𝜈 ℎ 2 = 𝑚 𝜈 93 eV <0.25
For all
stable flavors
∑ 𝑚 𝜈 ≲20 eV
JETP Lett. 4 (1966) 120

25. What is wrong with neutrino dark matter?
Galactic Phase Space (“Tremaine-Gunn-Limit”)
Maximum mass density of a degenerate
Fermi gas
Spiral galaxies
mn > 20–40 eV
Dwarf galaxies
mn > 100–200 eV
𝜌 max = 𝑚 𝜈 𝑝 max 3 3 𝜋 𝑛 max = 𝑚 𝜈 𝑚 𝜈 𝑣 escape 𝜋 2
Neutrino Free Streaming (Collisionless Phase Mixing)
At T < 1 MeV neutrino scattering in early universe is ineffective
Stream freely until non-relativistic
Wash out density contrasts on small scales
Neutrinos are “Hot Dark Matter”
Ruled out by structure formation
Neutrinos
Neutrinos
Over-density

26. Sky Map of Galaxies (XMASS XSC)

27. Structure Formation with Hot Dark Matter
Standard LCDM Model
Neutrinos with Smn = 6.9 eV
Structure fromation simulated with Gadget code
Cube size 256 Mpc at zero redshift
Troels Haugbølle,

28. Neutrino Mass Limits Post Planck (2013)
CMB alone constraining Smn
CMB + BAO constraining Smn + Neff
CMB + BAO limit: Smn < 0.23 eV (95% CL)
Ade et al. (Planck Collaboration), arXiv:

29. Future Cosmological Neutrino Mass Sensitivity
Pin down the neutrino mass in the sky!
ESA’s Euclid satellite to be
launched in 2020
Precision measurement of the
universe out to redshift of 2
Basse, Bjælde, Hamann, Hannestad & Wong, arXiv: :
Dark energy and neutrino constraints from a future EUCLID-like survey

30. Neutrinos as Astrophysical Messengers
Nuclear Reactors 
Sun 
Particle Accelerators 
Supernovae
(Stellar Collapse)
SN 1987A 
Earth Atmosphere
(Cosmic Rays) 
Astrophysical
Accelerators 
Earth Crust
(Natural Radioactivity) 
Cosmic Big Bang
(Today 330 n/cm3)
Indirect Evidence

31. Geo Neutrinos: What is it all about?
We know surprisingly little about
the Earth’s interior
Deepest drill hole ~ 12 km
Samples of crust for chemical
analysis available (e.g. vulcanoes)
Reconstructed density profile
from seismic measurements
Heat flux from measured
temperature gradient TW
(Expectation from canonical BSE
model ~ 19 TW from crust and
mantle, nothing from core)
Neutrinos escape unscathed
Carry information about chemical composition, radioactive energy
production or even a hypothetical reactor in the Earth’s core

32. Geo Neutrinos Expected Geoneutrino Flux
KamLAND Scintillator-Detector (1000 t)
Reactor Background

33. Reactor On-Off KamLAND Data
2011 Earthquake
Reactors shut down
Scintillator
Purification
KamLAND-Zen
Construction
KamLAND Collaboration, arXiv: (2013)

34. KamLAND Geo-Neutrino Flux
116 − Geoneutrino events
(U/Th = 3.9 fixed)
Separately free fitting:
U events
Th events
Beginning of
neutrino geophysics!
KamLAND Collaboration, arXiv: (2013)

35. Applied Anti-Neutrino Physics (AAP)
Annual Conference Series since 2004
• Neutrino geophysics
• Reactor monitoring
(“Neutrinos for Peace”)
Relatively small detectors can
measure nuclear activity
without intrusion
Of interest for monitoring by
International Atomic Energy Agency
(Monitors fissile material in civil
nuclear cycles)

36. What are the sources for the primary cosmic rays? Cosmic Rays
100 years later we are still asking
What are the sources
for the primary
cosmic rays?
Cosmic Rays
Victor Hess (1911/12)
Air Shower:
1019 eV primary particle
100 billion secondary
particles at sea level

37. Neutrino Beams: Heaven and Earthp
Target:
Protons or Photons
𝜋 0
𝜋 ± 𝜸
Approx. equal fluxes of
photons & neutrinos
𝝁 𝝂 𝝁
𝒆 𝝂 𝒆 𝝂 𝝁
Equal neutrino fluxes
in all flavors due to
oscillations
𝝂 𝒆 𝝂 𝝁 𝝂 𝝉
F. Halzen (2002)

38. Nucleus of the Active Galaxy NGC 4261

39. IceCube Neutrino Telescope at the South Pole
Instrumentation of 1 km3 antarctic
ice with ~ 5000 photo multipliers
completed December 2010

40. Two High-Energy Events in IceCube
Ernie ~ 1.1 PeV
Bert ~ 1.3 PeV

41. Ernie & Bert and 26 Additional Events in IceCube
Significance of all 28 events: 4.1s, Background −
Ernie & Bert

42. SN 1006 over Sydney
Supernova Neutrinos

43. Crab Nebula

44. Stellar Collapse and Supernova Explosion
Onion structure
Degenerate iron core:
r  109 g cm-3
T  K
MFe  1.5 Msun
RFe  3000 km
Hydrogen Burning
Main-sequence star
Collapse (implosion)
Helium-burning star
Helium
Burning
Hydrogen

45. Stellar Collapse and Supernova Explosion
Newborn Neutron Star
~ 50 km
Proto-Neutron Star
r ~ rnuc = 3  g cm-3
T ~ 30 MeV
Collapse (implosion)
Explosion

46. Stellar Collapse and Supernova Explosion
Newborn Neutron Star
~ 50 km
Neutrino
cooling by
diffusion
Gravitational binding energy
Eb  3  1053 erg  17% MSUN c2
This shows up as
99% Neutrinos
1% Kinetic energy of explosion
0.01% Photons, outshine host galaxy
Neutrino luminosity
Ln ~ 3  1053 erg / 3 sec
~ 3  1019 LSUN
While it lasts, outshines the entire
visible universe
Proto-Neutron Star
r ~ rnuc = 3  g cm-3
T ~ 30 MeV

47. Diffuse Supernova Neutrino Background (DSNB)
• A few core collapses per second
in the visible universe
• Emitted 𝜈 energy density
~ extra galactic background light
~ 10% of CMB density
• Detectable 𝜈 𝑒 flux at Earth
∼10 cm −2 s −1
mostly from redshift 𝑧∼1
• Confirm star-formation rate
• Nu emission from average core
collapse & black-hole formation
• Pushing frontiers of neutrino
astronomy to cosmic distances!
Beacom & Vagins,
PRL 93:171101,2004
Window of opportunity between
reactor 𝜈 𝑒 and atmospheric 𝜈 bkg

48. Sanduleak -69 202 Supernova 1987A Sanduleak -69 202 23 February 1987
Tarantula Nebula
Large Magellanic Cloud
Distance 50 kpc
( light years)

49. Neutrino Signal of Supernova 1987A
Kamiokande-II (Japan)
Water Cherenkov detector
2140 tons
Clock uncertainty 1 min
Irvine-Michigan-Brookhaven (US)
Water Cherenkov detector
6800 tons
Clock uncertainty 50 ms
Baksan Scintillator Telescope
(Soviet Union), 200 tons
Random event cluster ~ 0.7/day
Clock uncertainty +2/-54 s
Within clock uncertainties,
all signals are contemporaneous

50. Do Neutrinos Gravitate?
Early light curve of SN 1987A
Shapiro time delay for particles
moving in a gravitational potential
Δ𝑡=−2 𝐴 𝐵 𝑑𝑡 Φ 𝑟 𝑡
For trip from LMC to us, depending
on galactic model,
Δ𝑡≈1–5 months
Neutrinos and photons respond to
gravity the same to within
1–4× 10 −3
Longo, PRL 60:173, 1988
Krauss & Tremaine, PRL 60:176, 1988
• Neutrinos arrived several hours
before photons as expected
• Transit time for 𝜈 and 𝛾 same
( yr) within a few hours

51. Supernova 1987A Energy-Loss Argument
SN 1987A neutrino signal
Neutrino
sphere
Volume emission
of new particles
Neutrino
diffusion
Emission of very weakly interacting
particles would “steal” energy from the
neutrino burst and shorten it.
(Early neutrino burst powered by accretion,
not sensitive to volume energy loss.)
Late-time signal most sensitive observable

52. Flavor Oscillations in Core-Collapse Supernovae
Neutrino-neutrino
refraction causes
a flavor instability,
flavor exchange
between different
parts of spectrum
Flavor eigenstates are
propagation eigenstates
Neutrino flux
Neutrino
sphere
MSW region

53. Neutrino Oscillations in Matter
3700 citations
Neutrinos in a medium suffer flavor-dependent
refraction f W Z n n n n f
𝑉 weak = 2 𝐺 F × 𝑁 e − 𝑁 n −𝑁 n for 𝜈 e for 𝜈 μ
Lincoln Wolfenstein
Typical density of Earth: 5 g/cm3
Δ 𝑉 weak ≈2× 10 −13 eV=0.2 peV

54. Flavor-Off-Diagonal Refractive Index
2-flavor neutrino evolution as an effective 2-level problem
i 𝜕 𝜕𝑡 𝜈 𝑒 𝜈 𝜇 =𝐻 𝜈 𝑒 𝜈 𝜇 𝝂
Effective mixing Hamiltonian Z n n
𝐻= 𝑀 2 2𝐸 𝐺 F 𝑁 𝑒 − 𝑁 𝑛 − 𝑁 𝑛 𝐺 F 𝑁 𝜈 𝑒 𝑁 〈𝜈 𝑒 𝜈 𝜇 𝑁 〈𝜈 𝜇 𝜈 𝑒 𝑁 𝜈 𝜇
Mass term in
flavor basis:
causes vacuum
oscillations
Wolfenstein’s weak
potential, causes MSW
“resonant” conversion
together with vacuum
term
Flavor-off-diagonal potential,
caused by flavor oscillations.
(J.Pantaleone, PLB 287:128,1992)
Flavor oscillations feed back on the Hamiltonian: Nonlinear effects!

55. Collective Supernova Nu Oscillations since 2006
Two seminal papers in 2006 triggered a torrent of activities
Duan, Fuller, Qian, astro-ph/ , Duan et al. astro-ph/
Balantekin, Gava & Volpe [ ]. Balantekin & Pehlivan [astro-ph/ ]. Blennow, Mirizzi & Serpico [ ]. Cherry, Fuller, Carlson, Duan & Qian [ , ]. Cherry, Wu, Fuller, Carlson, Duan & Qian [ ]. Cherry, Carlson, Friedland, Fuller & Vlasenko [ ]. Chakraborty, Choubey, Dasgupta & Kar [ ]. Chakraborty, Fischer, Mirizzi, Saviano, Tomàs [ , ]. Choubey, Dasgupta, Dighe & Mirizzi [ ]. Dasgupta & Dighe [ ]. Dasgupta, Dighe & Mirizzi [ ]. Dasgupta, Dighe, Raffelt & Smirnov [ ]. Dasgupta, Dighe, Mirizzi & Raffelt [ , ]. Dasgupta, Mirizzi, Tamborra & Tomàs [ ]. Dasgupta, Raffelt & Tamborra [ ]. Dasgupta, O'Connor & Ott [ ]. Duan [ ]. Duan, Fuller, Carlson & Qian [astro-ph/ , , , ]. Duan, Fuller & Qian [ , , , ]. Duan, Fuller & Carlson [ ]. Duan & Kneller [ ]. Duan & Friedland [ ]. Duan, Friedland, McLaughlin & Surman [ ]. Esteban-Pretel, Mirizzi, Pastor, Tomàs, Raffelt, Serpico & Sigl [ ]. Esteban-Pretel, Pastor, Tomàs, Raffelt & Sigl [ , ]. Fogli, Lisi, Marrone & Mirizzi [ ]. Fogli, Lisi, Marrone & Tamborra [ ]. Friedland [ ]. Gava & Jean-Louis [ ]. Gava & Volpe [ ]. Galais, Kneller & Volpe [ ]. Galais & Volpe [ ]. Gava, Kneller, Volpe & McLaughlin [ ]. Hannestad, Raffelt, Sigl & Wong [astro-ph/ ]. Wei Liao [ , ]. Lunardini, Müller & Janka [ ]. Mirizzi [ , ]. Mirizzi, Pozzorini, Raffelt & Serpico [ ]. Mirizzi & Serpico [ ]. Mirizzi & Tomàs [ ]. Pehlivan, Balantekin, Kajino & Yoshida [ ]. Pejcha, Dasgupta & Thompson [ ]. Raffelt [ , ]. Raffelt, Sarikas & Seixas [ ]. Raffelt & Seixas [ ]. Raffelt & Sigl [hep-ph/ ]. Raffelt & Smirnov [ , ]. Raffelt & Tamborra [ ]. Sawyer [hep-ph/ , , , ]. Sarikas, Raffelt, Hüdepohl & Janka [ ]. Sarikas, Tamborra, Raffelt, Hüdepohl & Janka [ ]. Saviano, Chakraborty, Fischer, Mirizzi [ ]. Väänänen & Volpe [ ]. Volpe, Väänänen & Espinoza [ ]. Vlasenko, Fuller Cirigliano [ ]. Wu & Qian [ ].

56. Operational Detectors for Supernova Neutrinos
MiniBooNE
(200)
HALO
(tens)
LVD (400)
Borexino (100)
Baksan
(100)
Super-K (104)
KamLAND (400)
Daya Bay
(100)
In brackets events
for a “fiducial SN”
at distance 10 kpc
IceCube (106)

57. SuperNova Early Warning System (SNEWS)
Early light curve of SN 1987A
Super-K
IceCube
Coincidence
Server
@ BNL
Alert
• Neutrinos arrive several hours
before photons
• Can alert astronomers several
hours in advance
LVD
Borexino

58. Local Group of Galaxies
With megatonne class (30 x SK)
60 events from Andromeda
Current best neutrino detectors
sensitive out to few 100 kpc

59. The Red Supergiant Betelgeuse (Alpha Orionis)
First resolved
image of a star
other than Sun
Distance
(Hipparcos)
130 pc (425 lyr)
If Betelgeuse goes Supernova:
6 107 neutrino events in Super-Kamiokande
2.4 103 neutrons /day from Si burning phase
(few days warning!), need neutron tagging
[Odrzywolek, Misiaszek & Kutschera, astro-ph/ ]

60. IceCube as a Supernova Neutrino Detector
SN signal at 10 kpc
10.8 Msun simulation
of Basel group
[arXiv: ]
Accretion
Cooling
• Each optical module (OM) picks up Cherenkov light from its neighborhood
• ~ 300 Cherenkov photons per OM from SN at 10 kpc, bkgd rate in one OM < 300 Hz
• SN appears as “correlated noise” in ~ 5000 OMs
• Significant energy information from time-correlated hits
Pryor, Roos & Webster, ApJ 329:355, Halzen, Jacobsen & Zas, astro-ph/
Demirörs, Ribordy & Salathe, arXiv:

61. First Realistic 3D Simulation (27 M ⊙ Garching Group)
Hanke, Müller, Wongwathanarat, Marek & Janka [arXiv: (26 March 2013)]

62. Variability seen in Neutrinos (3D Model)
Tamborra, Hanke, Müller, Janka & Raffelt, arXiv:
See also Lund, Marek, Lunardini, Janka & Raffelt, arXiv:

63. Next Generation Large-Scale Detector Concepts
5-100 kton
liquid Argon
DUSEL
LBNE
100 kton scale
scintillator
Hyper-K
Memphys
LENA
HanoHano
Megaton-scale
water Cherenkov

64. LENA: From Dream to Reality
Juno (formerly Daya Bay II), Collaboration formed (2014)
20 kt scintillator detector
Hierarchy determination with reactor neutrinos
Also good for low-energy neutrino astronomy
50 kt
Scintillator

65. Summary Understanding neutrino internal properties — a mature field
Neutrino mixing parameters:
Matrix well known from astro and lab evidence
New experiments for missing parameters in the making
Absolute masses yet to be determined (KATRIN, cosmology)
Majorana nature yet to be found (neutrino-less double beta expts)
Neutrinos as astrophysical messengers — a field in its infancy
Detailed measurement of solar nus (ca 60,000 events in Super-K)
First geo-neutrinos (ca 116 events in KamLAND)
SN 1987A (ca 20 events)
First high-E events in IceCube (Ernie, Bert, and 26 others)
More statistics needed in all of these areas:
bigger/better detectors planned or discussed
- Waiting for next nearby supernova

66. Neutrinos at the center
Astrophysics & Cosmology
Elementary Particle Physics n
Cosmic Rays