probing the origins of neutrino masses and baryon asymmetry of the universe

Probing the origins of neutrino masses and baryon asymmetry of the universe

@Maskawa Institute for Science and Culture (2014/01/27)

Takehiko Asaka (Niigata Univ.)

Contents

27/01/2014Takehiko Asaka (Niigata Univ.)

Overview – nMSM –

RH neutrinos and Dark Matter

RH neutrinos and Baryon Asymmetry

Search for RH neutrinos

Summary

TA, Blanchet, Shaposhnikov ’05TA, Shaposhnikov ‘05

TA, Ishida ‘10TA, Eijima, Ishida ‘11, ‘12

TA, Eijima, Watanabe ‘13TA, Eijima ‘13

Introduction

Higgs had been discovered !!

All elementary particles in the Standard Model had been confirmed by experiments !!

2012/07/04

What’s next after Higgs discovery?

Prologue: Physics beyond the SM About 20 years ago …,

There was no “convincing” evidence for physics beyond the standard model (SM)

People looked for physics beyond the SM “mainly” based on theoretical arguments and curiosities:

Hierarchy problemNaturalness problemGravity, String, …Strong CP problemWhy 3 generations?Why anomalies cancel?…

News from the skyNeutrino Oscillations

Cosmic MicrowaveBackground (CMB)

[SuperK]

[WMAP]27/01/2014Takehiko Asaka (Niigata Univ.)

Physics beyond the SM In the last decade(s), we have collected

quite “convincing” evidences for physics beyond the SM Neutrino oscillations

Baryon asymmetry

Dark matter

Dark energy

Primordial density perturbations

Physics beyond the SM In the last decade(s), we have collected

quite “convincing” evidences for physics beyond the SM Neutrino oscillations

Baryon asymmetry

Dark matter

Dark energy

Primordial density perturbations

Today, I would like to explain nMSM, which can solve first three problems!

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.) 27/01/2014

10Standard Model

(left-handed) (right-handed)

HiggsBosons

Quarks and Leptons Gauge Bosons

h 𝑔𝑍 0

𝑊 ±

11Standard Model

HiggsBosons

h 𝑔𝑍 0

𝑊 ±

12Neutrino Minimal SM (nMSM)

HiggsBosons

h 𝑔𝑍 0

𝑊 ±

TA, Blanchet, Shappshnikov (‘05),TA, Shaposhnikov (‘05)

𝜈𝑅1𝜈𝑅2𝜈𝑅3

Extension by RH neutrinos

Seesaw mechanism ()

Light active neutrinos → explain neutrino oscillations

Heavy neutral leptons Mass Mixing

+ h.c.2

cMR R R R R

ML i F L n n n n n

0 01 1( , ) . ( , ) . .02 2

c cDc L

L R TD R

M ML h c h c

𝜈𝐿=𝑈𝜈+Θ𝑁

M M MMn

1 2 3( , , )TU M U diag m m mn

(𝑁≃𝜈¿¿𝑅)¿

mixing in CC current

Where is the

scale of mass?

Minkowski ’77Yanagida ’79Gell-Mann, Ramond, Slansky ‘79Glashow ‘79

Scale of Majorana mass The simplest case: one pair of and

221 /TD D M

M M M F M MMn n

2atmM mn

Majorana Mass

ing tF F

Convenstional seesaw scenario:

Neutrino Yukawa couplings are comparable to those of quarks and charged leptons

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]

221 /TD D M

M M M F M MMn n

Majorana Mass

ing tF F

Baryogenesis via leptogenesis

Fukugita, Yanagida ‘86

The nMSM: No new mass scale is introduced

Oscillation of RH neutrinos can account for baryon asymmetry of the universe

Lightest RH neutrino (~keV) can be DM

Physics of RH neutrinos can be tested directly by experiments

[TA, Blanchet, Shaposhnikov; TA, Shposhnikov]

[Dodelson, Widrow,…]

[Akhmedov, Rubakov, Smirnov/ TA, Shaposhnikov]

221 /TD D M

M M M F M MMn n

Majorana Mass

ing tF F

Baryogenesis via neutrino osc.Akhmedov, Rubakov,

Smirnov ‘98TA, Shaposhnikov ‘05

Dark Matter Candidate

Neutrino Oscillation dataMasses and mixings

Baryon Asymmetry of the Universe (BAU)Mechanism via neutrino oscillation

Roles of three HNL

2 3 and N N

Unique Candidate:lightest heavy neutral lepton N1 with keV mass

Dark matter in the nMSM

27/01/2014

Dodelson, Widrow / Shi, Fuller / Dolgov, Hansen / Abazajian, Fuller, Patel /…(Incomplete list)

Decays of DM N1 is not completely stable particle !

Dominant decay: for keV Lifetime can be very long

N1 is not completely dark ! Subdominant decay: Branching ratio is small

But, severely restricted from X-ray observations

𝜏 N1=5×1026 sec ( keV𝑀 1 )

5( 10−8

Θ 2 )

𝐵𝑟=27𝛼𝑒𝑚 /8𝜋

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

Shi-Fuller scenarioProduction is boosted in the presence of lepton asymmetry due to

the MSW effect

Production of DM

W,Z na N1𝜽❑

Cosmological Constraints Radiative decays of DM

No signal Upper bound on mixing angle !

Light heavy neutral lepton = WDM

Lower bound on mass (Ly-a forest observations) (DW scenario)

Phase-space analysis (Tremaine-Gunn bound)

𝜆𝐹𝑆 Mpc( keV𝑀 1 )⟨|𝑞𝑁|⟩⟨|𝑞𝜈|⟩

Erase structures on smaller scales!

Boyarsky, Lesgourgues, Ruchayskiy, Viel ’09,…..

Tremaine, Gunn ‘79Boyarsky, Ruchayskiy, Iakubovskyi ‘08Gorbunov, Khmelnitsky, Ruvakov ‘08

Dark Matter

Laine, Shaposhnikov ‘08

Dark Matter

Dodelson-Widrow mechanism does not work due to stringent constraints from X-ray and Ly-a Shi-Fuller mechanism ?? Entropy production ?? U(1)_B-L extension ?? (see Ishida, Jeong, Takahashi ‘13) …

Yukawa couplings of N1 are very suppressed N1 decouples from the seesaw mechanism

-> Lightest active neutrino 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

TA, Takeda ‘14

Entropy production by heavier neutral lepton N2 and N3 can cool down DM’s velocity dispersion !

Active neutrino masses

exclude the degenerate masses of active neutrinos

Baryogenesis via neutrino oscillation

BAU in the nMSM

27/01/2014

Akhmedov, Rubakov, Smirnov (’98) TA, Shaposhnikov (‘05)

We find baryons mostly, not antibaryons ! Existence of antiproton

In cosmic rays, At TEVATRON, X

Asymmetry between baryons and antibaryons

2011/05/25(Wed)

Baryon v.s. antibaryon

How large ???

Baryon　 proton （ ) 　

　 neutron （ ) 　

Antibaryonantiproton （ )antineutron （ )

30Baryon asymmetry of the universe (BAU)

2011/05/25(Wed)

[Strumia 06]

Planck 2013 resultsarXiv:1303.5076

Baryon number densityEntropy density

Baryon Number = (# of baryons) (# of antibaryons)

𝒏𝑩

𝒔 =(𝟖 .𝟓𝟕𝟗±𝟎 .𝟏𝟎𝟗 )×𝟏𝟎−𝟏𝟏

Primordial abundances of 4He, D, 3He, Li

BAU from BBN

2011/05/25(Wed)

[PDG][Strumia 06]

32Brief history of the universe

2011/05/25(Wed)

Inflation

Recombination

generateBAU ! Baryogenesi

CMB 4He, D,…

33Conditions for baryogenesis

2011/05/25(Wed)

Sakharov (1967)

“According to our hypothesis, the occurrence of C asymmetry is the consequence of violation of CP invariance in the nonstationary expansion of the hot Universe during the superdense stage, as manifest in the difference between the partial probabilities of the charge-conjugate reactions.”

34Conditions for baryogenesis

2011/05/25(Wed)

Sakharov (1967)(1) Baryon number B is violated

(2) C and CP symmetries are violated

(3) Out of thermal equilibrium

Let us see whether the SM satisfies these conditions

35B violation in the SM

2011/05/25(Wed)

At classical level, B and L are conserved At quantum level, B and L are violated by non-perturbative anomaly effect

BL is conserved, but B+L is violated !

𝜕𝜇( 𝑗𝐵𝜇 − 𝑗𝐿𝜇 )=0

𝜕𝜇( 𝑗𝐵𝜇+ 𝑗𝐿𝜇 )≠0

36B and L

2011/05/25(Wed)

Energy

• Chern-Simons number (integer)

2011/05/25(Wed)

B and L At T = 0 Energy

Instanton

B+L breaking effect is negligible

[‘t Hooft ’76]

2011/05/25(Wed)

B and L For high temperatures

Energy Sphaleron

[Moore ‘00]

Sphaleron process is in equilibrium

[Buchmuller]

[Kuzumin, Rubakov, Shaposhnikov ’85]

39Sphaleron conversion

2011/05/25(Wed)

Initial (B-L) asymmetry is converted into B

(B-L)=0 initially leads to B=0 universe asymmetries are wahshed out!

[Khlebnikov, Shaposhnikov ‘88, Harvey, Turner ‘90]

We have to generate(B-L)>0 initially to explain B>0 universe !

40Baryogenesis conditions in the SM

2011/05/25(Wed)

B+L violations Sphaleron for T>100GeV

CP violation 　 1 CP phase in the quark-mixing (CKM) matrix

too small Out of equilibrium

Strong 1st order phase transition if but not satisfied

2 2 2 2 2 2 2 2 2 2 2 2 12 19CPV ( )( )( )( )( )( ) / 10CP t c t u c u b s b d s d EWJ m m m m m m m m m m m m T

[Kajantie, Laine, Rummukainen, Shaposhnikov]

<72GeVHM114.4GeV (exp.)HM

We have to go beyond the SM !!

2011/05/25(Wed)

Neutrino Masses

Baryon Asymmetry of the Universe

Leptogenesis

Baryogenesis via neutrino osc.

Overview

RH neutrinos

Seesaw

2011/05/25(Wed)

Leptogenesis Majorana masses break

RH neutrino decay can produce

Produced L is partially converted into B by sphaleron

[Fukugita, Yanagida ’86]

lepton number

( ) ( ) if CPVN L N L

CP violation

2011/05/25(Wed)Takehiko Asaka (Niigata Univ.)

CP violation in neutrino Yukawa couplings

44Out of equilibrium decay

2011/05/25(Wed)

For , is in thermal equilibrium

For EQ

Out of equilibrium decay of

45BAU via Leptogenesis

2011/05/25(Wed)

CP asymmetry

Sphaleron conv.

Efficiency factor

Number of

[Giudice et al 03]

2011/05/25(Wed)

Lower bound on mass M1

[Giudice et al ‘03]

Lower bound on mass

47Conventional seesaw scenario

2011/05/25(Wed)

Neutrino masses

RH neutrinos

Leptogenesis

Smallness of mn & BAU

SUSY GUTGauge coupling unification Naturalness problemLSP dark matterREWSB

Seesaw

Exp. test of RH is impossible!

Question

Can we have a realistic scenario of baryogenesis, even if RH neutrinos have Majorana masses smaller than ～ 100GeV ?

Answer:

Baryogenesis via neutrino oscillation

2011/05/25(Wed)

[Akhmedov, Rubakov, Smirnov ‘98][TA, Shaposhnikov ’05]

221 /TD D M

M M M F M MMn n

Majorana Mass

ing tF F

Baryogenesis via neutrino osc.Akhmedov, Rubakov,

Smirnov ‘98TA, Shaposhnikov ‘05

51Baryogenesis conditions

2011/05/25(Wed)

B and L violations (B+L) violation due to sphaleron L violation due to Majorana masses

Majorana masses < 100 GeV negligible for T>100 　 GeV

C and CP violations 1 CP phase in quark sector 6 CP phases in lepton sector

52Baryogenesis conditions

2011/05/25(Wed)

Out of equilibrium No 1st order EW phase transition as in the MSM Heavy neutral leptons can be out of equilibrium, if Yukawa couplings are small enough

To ensure this condition up to T ～ 100GeV7

1,2,3 2 10f La

Conclusion: The nMSM can potentially realize all three conditions for baryogenesis

53Baryogenesis via neutrino oscillations

RH neutrinos are created and oscillate with CPV The total lepton number is zero but is distributed

between LH and RH leptons The asymmetry of left-handed leptons is transferred

into baryon asymmetry by sphaleron effects

[Akhmedov, Rubakov, Smirnov ’98/ TA, Shaposhnikov ’05]

Idea: Oscillation of RH neutrinos is a source of BAU

Shaposhnikov (’08), Canetti, Shaposhnikov (‘10)TA, Ishida (‘10), Canetti, Drewes, Shaposhnikov (’12), TA, Eijima, Ishida (‘12)Canetti, Drewes, Shaposhnikov (‘12), Canetti, Drewes, Frossard, Shaposhnikov (‘12)

54Key points

27/01/2014

Baryogenesis via neutrino osc.

sphaleron

B L B L

55First step: at F2 order

2011/05/25(Wed)

N2 and N3 are produced via scatterings

N2 and N3 oscillate

N NLF †F

8NTV F Fk

Medium effects𝑇 osc (𝑀 0 𝑀𝑁 𝛥𝑀 )1 /3

56Second step: at F4 order

2011/05/25(Wed)

Active flavor asymmetries are generated

L LN†F F

[TA, Shaposhnikov]

Evolution rates of and are different due to CPV in

Evolution of each asymmetries

Active sector Sterile sector

Evolution of asymmetries

[Kuzmin, Rubakov, Shaposhnikov]

Shaleron converts L partially into baryon asymmetry

28 079 totB L

42.5 10 ( )Btot W

n L Ts

𝒏𝑩

𝒔 =(𝟖 .𝟓𝟕𝟗±𝟎 .𝟏𝟎𝟗 )×𝟏𝟎−𝟏𝟏

[Planck 2013]

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 (’98) / TA, Shaposhnikov (‘05)

Yield of BAU depends on Yukawa couplings and masses

Shaposhnikov (’08), Canetti, Shaposhnikov (‘10)TA, Ishida (‘10), Canetti, Drewes, Shaposhnikov (’12), TA, Eijima, Ishida (‘12)Canetti, Drewes, Shaposhnikov (‘12), Canetti, Drewes, Frossard, Shaposhnikov (‘12)

Especially, CP violating parametersand mass difference

𝑇 osc (𝑀 0 𝑀𝑁 𝛥𝑀 )1 /3

Baryogenesis via neutrino osc.Region accounting for

Canetti, Shaposhnikov ‘10

8.55-9.00)

(1) quasi-degenerate(2) masses are

TA, Eijima ‘13Two RH neutrino case

NHIH MeV (NH)

MeV (IH)

8.55-9.00)

(1) quasi-degenerate(2) masses are

TA, Eijima ‘13Two RH neutrino case

NHIH MeV (NH)

MeV (IH)

8.55-9.00)

Such light RH neutrinos can be directly tested by experiments!

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 ‘86, ’88]

𝜋+¿ ,𝐾 +¿→𝑒 +¿𝑁 ¿¿ ¿

𝑁⟶ ℓ+¿ ℓ−𝜈 , ℓ−𝜋+¿¿ ¿

BBN constraint on lifetime Long-lived may spoil the success of BBN

Speed up the expansion of the universe p-n conv. decouples earlier overproduction of

Distortion of spectrum of active neutrinos

Additional neutrinos may not be thermalized Upper bound on lifetime

Dolgov, Hansen, Rafflet, Semikoz (’00) One family case:

𝑛+𝜈⟷𝑝+𝑒− ,…

sec for Takehiko Asaka (Niigata Univ.) 27/01/2014

Constraints on light RH neutrinos

Cosmology

Direct search

Normal hierarchy Inverted hierarchy

MeV MeVMeV

TA, Eijima ‘13

Implication to 02 decay

Constraints on light RH neutrinos

Cosmology

Direct search

Normal hierarchy Inverted hierarchy

MeV MeVMeV

TA, Eijima ‘13

Mixing elements in IH caseMixing elements of heavy neutrinos

Mixing elements strongly depend on “”

We find allowed range of Majorana phase !

Θ𝛼 𝐼=⟨Φ ⟩ 𝐹 𝛼𝐼

𝑀 𝐼

𝑊𝑁 𝐼

𝑔Θ𝛼 𝐼ℓ𝛼+¿ ¿

Majorana phase in IH casesin𝜂 1 sin𝜂 0.3 all is allowed

𝐾 +¿→𝑒+¿𝑁 ¿¿

+cc 𝐾 +¿→𝜇+¿𝑁 ¿ ¿

Majorana phase is restricted for MeV!

Excluded by BBN +PS191

decays in IHEffective neutrino mass from light and heavy neutrinos 𝑚eff=𝑚𝑖𝑈 𝑒𝑖

2 + 𝑓 𝛽 (𝑀 𝐼 )𝑀 𝐼Θ𝑒𝐼2 =[1− 𝑓 𝛽 (𝑀 𝑁 ) ]𝑚eff

𝜈 TA, Eijima, Ishida (‘11)

𝑚eff𝜈𝜂=

Heavy neutrinos give negative contribution to

Constraint on restricts the predicted range of

Search for heavy neutrinos at T2K

TA, Eijima, Watanabe [JHEP1303 (2013) 125]

Search for light sterile neutrinos Production by meson decays

Peak searchMeasure in

Decays inside the detector𝑁⟶ ℓ+¿ ℓ

−𝜈+𝑐 .𝑐 . ¿

𝐸𝑒=𝑚𝐾

2 −𝑚𝑒2−𝑀𝑁

2𝑚𝐾

𝐾 +¿→𝑒+¿𝑁 ¿¿

𝐾 +¿→𝑒+¿ν ¿ ¿𝐾 +¿→𝑒+¿𝑁 ,𝐾 +¿→𝜇+ ¿𝑁 ¿ ¿¿ ¿

[Shrock ’80]

𝐾 +¿→𝑒+¿𝑁 ¿¿

𝐸𝑒

CERNPS191

Search for heavy neutrinos at T2K

Production of Detection of

𝐾 +¿→ℓ +¿+𝑁 ¿ ¿ 𝑁→ℓ−+𝜋+¿ ¿

Estimate flux of at ND280 Count # of signal decay inside ND280 Derive upper bounds on mixing angles

(ℓ−=𝑒− ,𝜇−)

Sensitivity: PS191 vs T2K

T2K at POT has a better sensitivity than PS191 ( POT) !

TA, Eijima, Watanabe ‘13

Signal vs Background Signal events: BG events:

To reduce BG, Use the invariant mass distribution of 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.

𝑁→ℓ−+𝜋+¿ ¿

(CC-) (CC-coherent)

arXiv:1310.1762

Summary The SM + three right-handed neutrinos

(nMSM) Lightest right-handed neutrino with mass

~10keV can be dark matterThe simplest Dodelson-Widrow scenario conflicts

with X-ray and Ly-alpha constraintsSome other production mechanism is needed

Heavier two right-handed neutrinos can be responsible to baryon asymmetry of the universeBaryogenesis via neutrino oscillationsGood target for future search experiments

Three sterile neutrinos We may call N2, N3 and N1 as “bright”, “clear” and

“dark”

Clear and Bright, NC and NB: Heavier onesNeutrino oscillationsBaryon asymmetryM~10GeV, F~10-7,

Dark, ND: Lightest oneDark matter (production?)M~keV, F<10-12, q<10-4

Backup

Comparison

T2K2013/4/12: 6.39x10^20 POT2013/5/8: 6.63x10^20 POT

GOAL: 7.8x10^21 POT

Neutrino Yukawa couplings for 1/2 1/2

PMNS /NF U D Dn

2 31/2 diag( , )ND M M

1 2 31/2 diag( , , )0D m m mn

cos sin

sin cos

12 13 12 13 13

PMNS 23 12 23 12 13 23 12 23 12 13 23 13

23 12 23 12 13 23 12 23 12 13 23 13

c c s c s e

U c s s c s e c c s s s e s c e

s s c c s e s c c s s e c c

[Casas, Ibarra ’01]

Parameters of active neutrinos

Parameters of sterile neutrinos

: active n masses

: sterile n masses

Dirac phase

(in NH)

Majorana phase

complex number

Effective neutrino mass 𝑚eff= ∑

𝑖=1,2,3𝑚𝑖𝑈 𝑒𝑖

2 + ∑𝐼=1,2,3

𝑓 𝛽 (𝑀 𝐼 )𝑀 𝐼Θ𝑒𝐼2

active neutrinos sterile neutrinos

[Blennow, Frenandez-Martinez, Pavon, Mnendez ’10]

𝑓 𝛽 (𝑀 )=𝑀0𝜈𝛽𝛽 (𝑀 )/𝑀 0𝜈𝛽𝛽(0)

in the MSM

in the nMSM is smaller than active ’s one

No significant constraint on in the nMSM !

NH case IH case

[TA, Eijima, Ishida ’11]

probing the origins of neutrino masses and baryon asymmetry of the universe

scale of mass

neutrino minimal sm

solar neutrino experimentsas

origins of neutrino

distinct neutrino mass

dark matter rh neutrinos

standard model sm people

minimal standard model

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