Introduction 2 Higgs had been discovered !! 2012/07/04 All - - PowerPoint PPT Presentation
The MSM Neutrino masses, Dark Matter, and Baryon Asymmetry Takehiko Asaka (Niigata Univ.) @Toyama Univ. (2014/01/12) Introduction 2 Higgs had been discovered !! 2012/07/04 All elementary particles in the Standard Model had been
Neutrino masses, Dark Matter, and Baryon Asymmetry
@Toyama Univ. (2014/01/12)
Takehiko Asaka (Niigata Univ.)
Introduction
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Higgs had been discovered !! All elementary particles
in the Standard Model had been confirmed by experiments !!
2012/07/04
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Prologue: Physics beyond the SM
About 20 years ago …, There was no “convincing” evidence for physics
beyond the minimal standard model (SM)
People looked for physics beyond the SM “mainly”
based on theoretical arguments and curiosities:
Hierarchy problem Gravity, String, … Strong CP problem Why 3 generations? Why anomalies cancel? …
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News from the sky Neutrino Oscillations Cosmic Microwave Background (CMB
[SuperK] [WMAP]
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Physics beyond the MSM
In the last decade(s), we have collected quite
“convincing” evidences for physics beyond the MSM
Neutrino oscillations Baryon asymmetry Dark matter Dark energy Primordial density perturbations
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Physics beyond the MSM
In the last decade(s), we have collected quite
“convincing” evidences for physics beyond the MSM
Neutrino oscillations Baryon asymmetry Dark matter Dark energy Primordial density perturbations Today, I would like to explain the MSM, which can
solve first three problems!
?? ??
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Origin of neutrino masses
Neutrino mass scales
Atmospheric:
Solar：
⇒ Need for physics beyond the SM !
Important questions: “What is the origin of neutrino masses?” “How do we test it experimentally?”
Takehiko Asaka (Niigata Univ.) 12/01/2014 8
Standard Model
9
R
(left-handed) (right-handed)
R R
u d
R R
c s
R R
t b
L
u d
e L
e
L
L
L
c s
R
e
R
L
t b
Higgs Bosons Quarks and Leptons Gauge Bosons
Takehiko Asaka (Niigata Univ.)
Standard Model
10
R
(left-handed) (right-handed)
R R
u d
R R
c s
R R
t b
L
u d
e L
e
L
L
L
c s
R
e
R
L
t b
Higgs Bosons Quarks and Leptons Gauge Bosons
Takehiko Asaka (Niigata Univ.)
Neutrino Minimal SM (MSM)
11
R
(left-handed) (right-handed)
R R
u d
R R
c s
R R
t b
L
u d
e L
e
L
L
L
c s
R
e
R
L
t b
Higgs Bosons Quarks and Leptons Gauge Bosons
TA, Shaposhnikov (ʻ05)
Takehiko Asaka (Niigata Univ.)
Extension by RH neutrinos
Seesaw mechanism ( Φ ≪ ) Light, active neutrinos
→ explain neutrino oscillations
Heavy, neutral leptons
Mass Mixing Θ /
+ h.c. 2
c M R R R R R
M L i F L
1 1 ( , ) . ( , ) . . 2 2
c c D c L L R T D R c M M
M M L h c h c M N M N M
T D D M
M M M M
1 2 3
( , , )
T
U M U diag m m m
≃
mixing in CC current
Where is the scale
Minkowski ʼ77 Yanagida ʼ79 Gell-Mann, Ramond, Slansky ʻ79 Glashow ʻ79 Takehiko Asaka (Niigata Univ.) 12/01/2014 12
Scale of Majorana mass
The simplest case: one pair of and
2 2
1 /
T D D M M
M M M F M M M
2 atm
M m
Majorana Mass Neutrino Yukawa Coupling
2
log10(F) log10(MM/GeV)
t
F F
e
F F
Takehiko Asaka (Niigata Univ.) 12/01/2014 13
Convenstional seesaw scenario:
Neutrino Yukawa couplings are comparable to those
MR >> 100GeV
Explain smallness of neutrino masses via seesaw Decays of RH neutrino(s) can account for baryon
asymmetry through leptogenesis
Physics of RH neutrino cannot be tested directly
by experiments
[Fukugita, Yanagida] [Yanagida; Gell-Mann, Ramond, Slansky]
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Scale of Majorana mass
The simplest case: one pair of and
2 2
1 /
T D D M M
M M M F M M M
Majorana Mass Neutrino Yukawa Coupling
2
log10(F) log10(MM/GeV)
t
F F
e
F F
Baryogenesis via leptogenesis
Fukugita, Yanagida ʻ86
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The MSM:
No new mass scale is introduced MR ~<100GeV
Lightest RH neutrino (~keV) can be DM (?) Oscillation of RH neutrinos can account for
baryon asymmetry of the universe
Physics of RH neutrinos can potentially tested by
experiments
[TA, Blanchet, Shaposhnikov; TA, Shposhnikov]
[Dodelson, Widrow,…] [Akhmedov, Rubakov, Smirnov/ TA, Shaposhnikov]
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Scale of Majorana mass
The simplest case: one pair of and
2 2
1 /
T D D M M
M M M F M M M
Majorana Mass Neutrino Yukawa Coupling
2
log10(F) log10(MM/GeV)
t
F F
e
F F
Baryogenesis via leptogenesis
Fukugita, Yanagida ʻ86
Baryogenesis via neutrino osc.
Akhmedov, Rubakov, Smirnov ʻ98 TA, Shaposhnikov ʻ05
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(“Dark” sterile neutrino)
Dark Matter Candidate (Here, we do not specify
its detail.)
To avoid constraints, Yukawaʼs should be
suppressed essentially,
(“Bright” and “Clear” sterile neutrinos)
Neutrino Oscillation data
Masses and mixings
Baryon Asymmetry of the Universe (BAU)
Mechanism via sterile neutrino oscillation
Roles of three HNL
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F
LINK
1
N
2 3
and N N
Dark Matter Candidate: lightest heavy neutral lepton N1 with ~keV mass
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Takehiko Asaka (Niigata Univ.)
Dodelson, Widrow / Shi, Fuller / Dolgov, Hansen / Abazajian, Fuller, Patel /… (Incomplete list)
Decays of DM
N1 is not completely stable particle ! Dominant decay:
Lifetime can be very long N1 is not completely dark ! Subdominant decay:
But, severely restricted from X-ray observations
+ … + …
5 10sec keV
Θ 27/8
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Due to smallness of Yukawa couplings,
N1 is not thermalized in the early universe
Production scenarios: Dodelson-Widrow scenario
Production via active-sterile neutrino mixing Dominant production at 100MeV
Shi-Fuller scenario
Production is boosted in the presence of lepton asymmetry
due to the MSW effect
Production of DM
W,Z
N1
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Cosmological Constraints
Radiative decays of DM No signal Upper bound on mixing angle ! Light heavy neutral lepton = WDM Lower bound on mass (Ly- forest observations)
≳ 8 keV (DW scenario)
Phase-space analysis (Tremaine-Gunn bound)
≳ 1 2 keV
~Mpc keV
Boyarsky, Lesgourgues, Ruchayskiy, Viel ʼ09,ʼ09
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Tremaine, Gunn ʻ79 Boyarsky, Ruchayskiy, Iakubovskyi ʻ08 Gorbunov, Khmelnitsky, Ruvakov ʻ08
Dark Matter
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Laine, Shaposhnikov ʻ08
Dark Matter
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Dodelson-Widrow mechanism does not work by Ly-
constraint
Shi-Fuller mechanism ?? Entropy production?? Yukawa couplings of N1 are very suppressed
N1 decouples from the seesaw mechanism
N1 contribution is negligible for baryogenesis
N2 and N3 are responsible for
Seesaw mass matrix for neutrino masses Baryon asymmetry of the universe
Entropy Production in the nuMSM
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TA, Takeda ʻ14
Entropy production by heavier neutral lepton N2 and N3 can cool down DMʼs velocity dispersion !
Active neutrino masses
exclude the degenerate masses of active neutrinos
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Dark Matter Candidate: lightest sterile neutrino N1 with ~keV mass
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Takehiko Asaka (Niigata Univ.)
Dodelson, Widrow / Shi, Fuller / Dolgov, Hansen / Abazajian, Fuller, Patel /… (Incomplete list)
Baryogenesis via neutrino osc.
Oscillation of heavy neutrinos can be a source of BAU
CPV in oscillation and production generates asymmetries Asymmetries are separated into LH and RH leptons Asymmetry in LH leptons is converted into BAU
Akhmedov, Rubakov, Smirnov (ʼ98) / TA, Shaposhnikov (ʻ05)
Yield of BAU depends on Yukawa couplings
and masses
Shaposhnikov (ʼ08), Canetti, Shaposhnikov (ʻ10) TA, Ishida (ʻ10), Canetti, Drewes, Shaposhnikov (ʼ12), TA, Eijima, Ishida (ʻ12) Canetti, Drewes, Shaposhnikov (ʻ12), Canetti, Drewes, Frossard, Shaposhnikov (ʻ12)
Especially, CP violating parameters and mass difference
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Key points
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Baryogenesis via leptogenesis Baryogenesis via neutrino osc.
B B L L
sphaleron sphaleron
B L B L
Baryogenesis via neutrino osc.
Region accounting for
Canetti, Shaposhnikov ʻ10 IH NH
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Baryogenesis via neutrino osc.
Region accounting for (1) quasi-degenerate (2) masses are
TA, Eijima ʻ13
10-4 10-3 10-2 10-1 100 101 102 103 104 105 106 107 10-4 10-3 10-2 10-1 100 ∆Μ [eV] MN[GeV]
Two RH neutrino case NH IH
2.1 MeV (NH) 0.7 MeV (IH)
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Baryogenesis via neutrino osc.
Region accounting for (1) quasi-degenerate (2) masses are
TA, Eijima ʻ13
10-4 10-3 10-2 10-1 100 101 102 103 104 105 106 107 10-4 10-3 10-2 10-1 100 ∆Μ [eV] MN[GeV]
Two RH neutrino case NH IH
2.1 MeV (NH) 0.7 MeV (IH)
Such light RH neutrinos can be directly tested by experiments!
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Direct search experiment
PS191
Beam dump experiment performed at CERN in 1984
Production Detection
Upper bounds mixing elements
→ Lower bound on lifetime of
[Bernardi et al ʻ86, ʼ88]
, → ⟶ ℓ ℓ , ℓ
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BBN constraint on lifetime
Long-lived , may spoil the success of BBN Speed up the expansion of the universe
, ⇒
, → ̅ , , … Additional neutrinos may not be thermalized
⇒ Upper bound on lifetime
Dolgov, Hansen, Rafflet, Semikoz (ʼ00)
One family case:
⟷ , …
0.1 sec for
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Constraints on light RH neutrinos
10-3 10-2 10-1 100 200 300 400 τN [sec] MN[MeV] 10-3 10-2 10-1 100 200 300 400 τN [sec] MN [MeV]
Cosmology Direct search Normal hierarchy Inverted hierarchy
TA, Eijima ʻ13
Takehiko Asaka (Niigata Univ.) 12/01/2014 35
TA, Eijima, Watanabe
[JHEP1303 (2013) 125]
Takehiko Asaka (Niigata Univ.) 12/01/2014
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Search for light sterile neutrinos
Production by meson decays Peak search
Measure in →
Decays inside the detector
⟶ ℓ ℓ . .
events → → ν
→ , →
[Shrock ʼ80]
→
PS191
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Search for heavy neutrinos at T2K
Detection of
Count # of signal decay inside ND280 Derive upper bounds on mixing angles
SK
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Sensitivity: PS191 vs T2K
T2K at 10 POT has a better sensitivity than PS191 (0.86 10 POT) !
PS191 T2K TA, Eijima, Watanabe ʻ13
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Signal vs Background
Signal events: BG events:
To reduce BG,
Use the invariant mass distribution of ℓ and
since it has a peak at for signal decay
Use the low density part of detector filled with argon gas
(9m^3) out of 61.25m^3
See also the recent proposal to search for heavy neutrinos at the CERN SPS. → ℓ → (CC-) O → O (CC-coherent)
arXiv:1310.1762
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Summary
The MSM + three right-handed neutrinos (MSM) Lightest right-handed neutrino with mass ~10keV
can be dark matter
The simplest Dodelson-Widrow scenario conflicts
with X-ray and Ly-alpha constraints
Some other production mechanism is needed
Heavier two right-handed neutrinos can be
responsible to baryon asymmetry of the universe
Baryogenesis via neutrino oscillations
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Three sterile neutrinos
We may call N2, N3 and N1 as “bright”, “clear” and
“dark”
Clear and Bright, NC and NB: Heavier ones
Neutrino oscillations Baryon asymmetry M~10GeV, F~10-7,
Dark, ND: Lightest one
Dark matter (production?) M~keV, F<10-12, q<10-4
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