The document summarizes a presentation given on neutrino research. It begins with a brief history of neutrinos, including their theoretical postulation in 1930 and first experimental detection in 1956. It then discusses the topic of neutrino oscillation, which provides evidence that neutrinos have mass and mix between flavor states. The presentation also outlines how neutrino oscillation experiments work by measuring probabilities of different neutrino flavors at a baseline, and provides the T2K experiment as an example. Finally, it discusses the importance of neutrino oscillation in going beyond the Standard Model of particle physics.

1. S. Cao
IPNS, KEK
& Neutrino Group, I
7/22/2017 Serminar at HUST, 2017
Ø Brief Neutrino History
Ø Neutrino Oscillation
Ø Future prospects
Ø Neutrino Group / IFIRSE
1
The Light from The Invisible World
of Neutrinos

2. Claims
7/22/2017 Serminar at HUST, 2017 2
o I will focus on neutrino oscillation (other interesting
topics such as double-neutrinoless beta decay, neutrino
astronomy, geoneutrino… are not included)
o I borrow heavily from other talks, results but
sometimes missing references
o Stop me anytime if you have questions

3. Brief neutrino history
7/22/2017 Serminar at HUST, 2017 3
Credit to APS
² 1930: On-paper appearance as “desperate” remedy by W. Pauli
² 1956: first experimentally discovered by Reines and Cowan
² 1962: existence confirmed by Lederman et al.
² 1998: Atmospheric neutrino oscillations discovered by Super-K
² 2000: first evidence reported by DONUT experiment
² 2001: Solar neutrino oscillations detected by SNO (KamLAND 2002)
² 2011: transitions observed by OPERA
² 2011-13: by T2K, by Daya Bay(2012)
² 2015: Nobel prizes for 𝜈 oscillations, Breakthrough prize (2016)
¯⌫e
⌫µ
⌫⌧
⌫µ ! ⌫⌧
⌫µ ! ⌫e ¯⌫e ! ¯⌫e
2015
T2K observe 𝜈 𝜇 à𝜈e
appearance
Nobel & Breakthrough
for 𝜈 oscillations

4. Early day of Neutrino
7/22/2017 Serminar at HUST, 2017 4
o 1914~1930, energy conservation
in β decays went crisis
o 1930, W. Pauli postulated a new
"invisible" particle
https://en.wikipedia.org/wiki/Beta_decay
“I have done a terrible thing. I invented a particle that cannot be detected”
– W. Pauli

5. Early day of Neutrino
7/22/2017 Serminar at HUST, 2017 5
o ~1930, energy conservation in β
decays went crisis
o 1930, W. Pauli postulated a new
"invisible" particle
o 1933, E. Fermi built weak
interaction theory of neutrinos
o 1956, Reines & Cowan, first
detected (anti-)neutrino
experimentally
à Nobel prize in 1995

6. Three observed types of neutrinos
7/22/2017 Serminar at HUST, 2017 6
https://goo.gl/V4ig39
three types of neutrinos observed

7. 7/22/2017 Serminar at HUST, 2017 7
From “inivisble” particle, neutrinos become detectable, …
and it turns out neutrinos are very abundant

8. 7/22/2017 Serminar at HUST, 2017 8
Neutrino grand spectrum
300 / cm3
65 billions / cm2 / s
1058 in 10 s
10-12
10-8
10-4
100
104
108
1012
1016
1020
1024
Flux(cm-2s-1MeV-1)
10-6 10-3 1 103 106 109 1012 1015 1018
µeV meV eV keV MeV GeV TeV PeV EeV
Neutrino energy (eV)
Cosmological neutrinos
Solar neutrinos
Supernova neutrinos
geoneutrinos
Nuclear reactors
Atmospheric neutrinos
AGN neutrinos
Neutrino sources
Credit to F. Vannucci

9. 7/22/2017 Serminar at HUST, 2017 9
o Each second, 1012 neutrinos from the Sun passing through your
body. In timeline, ~1022 neutrinos passing but only One interact w/
your body in average
Some facts
o In Universe, neutrino density is about 300 neutrinos/cm3, 2nd
abundant particle after photon 1000/cm3.
o Atom density is equivalent to 1 proton/ 4m3, i.e 1/10-9 of neutrino
density. Even neutrino has very small mass, 10-9 of proton mass,
total weight of neutrinos is in order of sum of all stars in Universe
Indeed, neutrino mass is non-zero!

10. Solar & atmospheric deficits
7/22/2017 Serminar at HUST, 2017 10
o New chapter of neutrino physics started when differences between
data and scientist’s prediction observed
o So called, Solar neutrino anomaly and Atmospheric neutrino
anomaly
Solar neutrino anomaly Atmospheric neutrino anomaly

11. 7/22/2017 Serminar at HUST, 2017 11
"for the discovery of neutrino oscillations,
which shows that neutrinos have mass"

12. 7/22/2017 Serminar at HUST, 2017 12
Breakthrough prize in fundamental physics 2016
Awarded to five experiments investigating neutrino oscillation

13. What is Neutrino Oscillation?
7/22/2017 Serminar at HUST, 2017
13

14. 7/22/2017 Serminar at HUST, 2017
14
Neutrino oscillations
Is a quantum mechanical phenomenon whereby a neutrino created
with a specific lepton flavor (electron, muon, or tau) can later be
measured to have different flavor Wikipedia

15. 7/22/2017 Serminar at HUST, 2017
15
Neutrino oscillations
Is a quantum mechanical phenomenon whereby a neutrino created
with a specific lepton flavor (electron, muon, or tau) can later be
measured to have different flavor
|⌫↵(0)i = U↵i|⌫i(0)i
↵ = e, µ, ⌧ i = 1, 2, 3
|⌫↵(0)i |⌫ (t)i
U⇤
↵i U j
e mit
Credit to Boris K.
Wikipedia
Flavor eigenstates
Mass eigenstates
|⌫ (t)i = U j|⌫j(t)i
= e, µ, ⌧ j = 1, 2, 3

16. 7/22/2017 Serminar at HUST, 2017
16
Neutrino oscillations
Is a quantum mechanical phenomenon whereby a neutrino created
with a specific lepton flavor (electron, muon, or tau) can later be
measured to have different flavor
0
@
⌫e
⌫µ
⌫⌧
1
A =
0
@
1 0 0
0 c23 s23
0 s23 c23
1
A
0
@
c12 s12 0
s12 c12 0
0 0 1
1
A
0
@
c13 0 s13e i CP
0 1 0
s13ei CP
0 c13
1
A
0
@
⌫1
⌫2
⌫3
1
A
cij = cos ✓ij, sij = sin ✓ij
Atmospherics / Accelerators
Wikipedia

17. Neutrino oscillation landscape
7/22/2017 Serminar at HUST, 2017 17
Gonzalez-Garcia et al., arXiv:1512.06856
⌫e ⌫µ ⌫⌧
Normal hierarchy Inverted hierarchy
m2
lightest m2
lightest
0
@
⌫e
⌫µ
⌫⌧
1
A =
0
@
1 0 0
0 c23 s23
0 s23 c23
1
A
0
@
c12 s12 0
s12 c12 0
0 0 1
1
A
0
@
c13 0 s13e i CP
0 1 0
s13ei CP
0 c13
1
A
0
@
⌫1
⌫2
⌫3
1
A
sign( m2
32) = ?
✓23 is maximal ?
CP = ?
mlightest = ?
m2
32
m2
31
m2
21
m2
21
⌫1
⌫2
⌫3
⌫1
⌫2
⌫3
m2
21 = 7.50+0.19
0.17 ⇥ 10 5
eV2
m2
31 = 2.457+0.047
0.047 ⇥ 10 3
eV2
✓13 = 8.50+0.20
0.21( )
✓12 = 33.48+0.78
0.75( )
✓23 = 42.3+3.0
1.6( )
m2
ij = m2
⌫i
m2
⌫j
Global fit – Normal hierarchy

18. Why is Neutrino Oscillation
important?
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18

19. Standard Model & neutrino oscillations
37/22/2017 Serminar at HUST, 2017
Source: AAAS
Standard Model:
² Neutrinos interact through the weak
interaction
² Lepton flavor is strictly conserved
² Neutrinos have zero mass
Spontaneously breaking

20. Standard Model & neutrino oscillations
Standard Model:
² Neutrinos interact through the weak
interaction
² Lepton flavor is strictly conserved
² Neutrinos have zero mass
Neutrino oscillations:
² Indicate massive neutrinos
² Mix flavor and mass eigenstates
² Beyond Standard Model
47/22/2017 Serminar at HUST, 2017
Source: AAAS
The only lab-based evidence beyond Standard Model

21. How to measure neutrino
oscillations?
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21

22. 𝜈 oscillation measurement
7/22/2017 Serminar at HUST, 2017 22
It’s about probability measurement, basic needs:
ü Source of well-understood neutrino flavor composition
ü Detector at optimal baseline, enable to distinguish flavors
ü Neutrino energy is necessary to known
Defined baseline
𝜈 source
𝜈 detector
Theoretical,
simple

23. Example: T2K experiment
7/22/2017 23Serminar at HUST, 2017
Short version Disappearance channel
Appearance channel

24. Disappearance channel
7/22/2017 Serminar at HUST, 2017 24
⌫µ + n ! µ + p
⌫e + n ! e + p
Disappearance channel
(GeV)νE
0.5 1 1.5 2 2.5 3
Osc.Prob
0
0.5
1
flux
µ
νOff-axis°2.5
=0.523θ2
, sin2
eV
-3
=2.5x1032
2
m∆
µν→µν=µν→µν
q Sensitive to 𝜃23 and 𝛥m2
31 (atmospheric sector)
à Precision measurement (𝜃23 is maximal?)
q CPT symmetry test by comparing disappearance
in muon neutrinos and muon anti-neutrinos

25. Appearance channel
7/22/2017 Serminar at HUST, 2017 25
⌫µ + n ! µ + p
⌫e + n ! e + p
Appearance channel
(GeV)νE
0.5 1 1.5 2 2.5 3
Osc.Prob
0
0.02
0.04
0.06
0.08
0.1
flux
µ
νOff-axis°2.5
ν, NH,°=0cpδ
ν, NH,°=270cpδ
ν, NH,°=0cpδ
ν, NH,°=270cpδ
eν→µν,eν→µν
q Sensitive to 𝜃13 and 𝛿CP
o Degeneracy 𝜃13 - 𝛿CP is difficult to disentangle with
long baseline experiment à Need constraint from
reactor measurement on 𝜃13 (or high statistics)
q 20-30% effect of 𝛿CP and 10% effect of matter effect
(not too long baseline 295km)
Large CP effect
Small matter effect
(in vacuum)
(in matter)

26. 7/22/2017 Serminar at HUST, 2017 26
⌫µ + n ! µ + p
⌫e + n ! e + p
Each channel is essentially sensitive to sub-set of parameters. To
precise measurement of neutrino oscillation parameters, data from
multiple channels are used.

27. 𝜈 oscillation measurement (cont’d)
7/22/2017 Serminar at HUST, 2017 27
It’s about probability measurement, basic needs:
ü Source of well-understood neutrino flavor composition
q Neutrino weak interactionà powerful source
q Flux uncertainty
ü Detector at optimal baseline, enable to distinguish flavors
q Uncertainty in neutrino-nuclei interactionà interaction uncertainty
q Response is not perfect, misidentify flavor à detector uncertainty
ü Neutrino energy is necessary to known
q Typically not mono-energy neutrino source
q Can bias in reconstructing neutrino energy
Defined baseline
𝜈 source
𝜈 detector
Experimental,
NOT simple

28. How to make neutrino beam?
7/22/2017 Serminar at HUST, 2017
28

29. J-PARC neutrino beam line
7/22/2017
² High intensity, almost pure muon (anti) neutrino beam from J-PARC
29Serminar at HUST, 2017
² 30 GeV p extracted from J-PARC main ring, impinge on 90-cm, graphite target
² Induced 𝜋+ (𝜋-) focused by three horns, pass through a 96-m decay pipe
² Beam dump to stop all particles except neutrinos and high-energy muons
² Muon monitor, downstream of beam dump, to monitor beam intensity and direction by
measuring induced muon profile.
1.9 ⇥ int

30. Neutrino flux
7/22/2017
² High intensity, almost pure muon (anti) neutrino beam from J-PARC
30Serminar at HUST, 2017
² You need to know how many
neutrinos you produced and what
flavor they are
² Knowledge of hadron production
is needed
Currently we know neutrino flux with 10% uncertainty
𝜈̅ mode
< 1%(⌫e/⌫e)
< 1%(⌫e/⌫e)
T2K Far Detector
T2K Far Detector
(Beam modes changed by switching horn polarity)
𝝂-mode

31. How to detect neutrino?
7/22/2017 Serminar at HUST, 2017
31

32. 7/22/2017 Serminar at HUST, 2017
32
How to detect neutrinos?
It means
To have 100 events interactions
In 1 tons of water, you will need
100/(106/18*8*6.02*1023*7*10-39)
~ 5x 1010 neutrino
Nevent = ⇥ ⇥ T ⇥ ✏
Neutrino interaction is very weak. To study neutrinos,
need very big detector and/or powerful neutrino beam

33. 7/22/2017 Serminar at HUST, 2017
33
How to detect neutrinos?
Also need to put underground to reduce
the noise (like you need headphone to
cancel the noise)
Super-Kamiokande
(41.4 m tall x 39.3m diameter)
Contain 50,000 tons of water
1000m underground

34. 7/22/2017 Serminar at HUST, 2017
34
How to detect neutrinos?
“Eyes”
A lot of “Eyes”
You can’t directly detect/see neutrinos. You look at
their trace when they interact w/ nuclear instead

35. 7/22/2017 Serminar at HUST, 2017
35
How to detect neutrinos?
“Eyes”
A lot of “Eyes”
1. charged particles
2. Light generated & reflected
3. Light captured &
guided by WLS
Act like capacitor
w/ C = 10-100 fF
Or use ionization to track charged particle

36. 7/22/2017 Serminar at HUST, 2017 36
Many techniques to detect neutrinos, identify their flavor, and
measure neutrino energy

37. Opening Questions
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37

38. Opening questions (1)
7/22/2017 Serminar at HUST, 2017 38
Credit to H. Murayama
q How do neutrinos get mass?
q Why are their masses so small?

39. Opening questions (2)
7/22/2017 Serminar at HUST, 2017 39
arXiv:1212.6374
q Why does PMNS matrix differ from CKM matrix?
*Area of the squares represents square of matrix elements

40. Opening questions (3)
7/22/2017 Serminar at HUST, 2017 40
q What is neutrino’s role in Universe evolution?
q Where is anti-matter?
Credit: NASA/WMAP Science Team
Source: scienceabc.com

41. Opening questions (3-cont’d)
7/22/2017 Serminar at HUST, 2017 41
Credit to B. Kayser
q CP-violating phase in heavy neutrino decays leads to CP-
violating phase in the light neutrino mixing
Measure CP violation phase in neutrino
mixing via neutrino oscillations wanted!!!

42. A BIG question: How did the Universe begin?
7/24/17 42
² Amount of matter and anti-matter should be the same at the begin of Universe.
1,000,000,001
Proton
1,000,000,001
Anti-Proton
Begin of Universe

43. A BIG question: How did the Universe begin?
7/24/17 43
² Amount of matter and anti-matter should be the same at the begin of Universe.
² But our present Universe contains mostly matter. Tracking back, matter somehow
is dominant shorter
1,000,000,001
Proton
1,000,000,001
Anti-Proton
Begin of Universe
1,000,000,002
Proton
1,000,000,000
Anti-Proton
Shortly after

44. A BIG question: How did the Universe begin?
7/24/17 44
1,000,000,002
Matter
1,000,000,000
Anti-Matter
Shortly after
This is how the Universe begin!!!

45. A BIG question: How did the Universe begin?
7/24/17 45
² Amount of matter and anti-matter should be the same at the begin of Universe.
² But our present Universe contains mostly matter. Tracking back, matter somehow
is dominant shorter
1,000,000,001
Proton
1,000,000,001
Anti-Proton
Begin of Universe
1,000,000,002
Matter
1,000,000,000
Anti-Matter
Shortly after
² Anti-matter need to convert to matter ß But how? We need to find the
answer in the future. And this is the ULTIMATE goal of physics, find the
answer to question: How does the Universe begin?

46. Opening questions (3-cont’d)
7/22/2017 Serminar at HUST, 2017 46
q Can it be due to CP-violating decays of heavy neutrinos?
1,000,000,001
Baryons
1,000,000,001
Anti-Baryons
1,000,000,002
Baryons
1,000,000,000
Anti-Baryons
Begin of Universe Shortly after
?
CP-violating decays
(B = 0; L ≠ 0)
Sphaleron
Process
(B ≠ 0; L ≠ 0)(Fukugita, Yanagida)

47. Very recent results (selected)
7/22/2017 Serminar at HUST, 2017
47

48. Results: 𝛿CP
7/22/2017 Serminar at HUST, 2017 48
T2K data: δCP =0 is excluded at 2𝜎 CL.
T2K is about to release new result w/ double statistics

49. Results: 𝜃23 & ∆𝑚,-
-
7/22/2017 Serminar at HUST, 2017 49
Why T2K prefer maximal mixing, NOvA disfavors w/
2.6𝜎 CL.

50. Future of neutrinos
7/22/2017 Serminar at HUST, 2017
50
More powerful beam, bigger detector & more precise
detection

51. Future neutrino long baseline experiments
7/22/2017 Serminar at HUST, 2017 51

52. Vietnam Neutrino Group at IFIRSE
7/22/2017 Serminar at HUST, 2017
52
On July 17th 2017, Neutrino Group at IFIRSE is officially formed with the
MoU signing between Japanese Professors and Rencontres Du Vietnam
at ICISE center. More detail can be found at
http://www-he.scphys.kyoto-u.ac.jp/member/nuICISE/OpenMoU.html

53. 7/22/2017 Serminar at HUST, 2017
53
• Leader: Tsuyoshi Nakaya (Kyoto Univ.)
• Member: Van Nguyen (IFIRSE & IOP)
• Affiliated member: Yuichi Oyama (IPNS, KEK); Makoto Miura (ICRR, Univ. of
Tokyo); Atsumu Suzuki (Kobe Univ.); Son Cao (IPNS, KEK); TrungLe (Tufts
Univ.)
Vietnam Neutrino Group at IFIRSE
We organized Vietnam School
on Neutrinos & start enrolling
students

54. Summary
7/22/2017 Serminar at HUST, 2017
² Neutrino physics is very active field now
² Neutrinos are special & they keep surprising us
² We have a Vietnamese group start joining big experiment
Maybe we are lucky to know why the Life begin
54
*Number of anime taken http://higgstan.com