Large Scale Structure Signals of Neutrino Decay

Home , Scale factor (cosmology)

Peizhi Du University of Maryland

Phenomenology 2019 University of Pittsburgh

based on the work with Zackaria Chacko, Abhish Dev, Vivian Poulin, Yuhsin Tsai (to appear) Motivation

SM neutrinos:

We have detected neutrinos 50 years ago

Least known particles in the SM

1 Motivation

SM neutrinos:

We have detected neutrinos 50 years ago

Least known particles in the SM

What we don’t know:

• Origin of mass

• Majorana or Dirac

• Mass ordering

• Total mass

1 Motivation

SM neutrinos:

We have detected neutrinos 50 years ago

Least known particles in the SM

What we don’t know:

• Origin of mass

• Majorana or Dirac

• Mass ordering D1 • Total mass ⌫ • Lifetime

…… D2

1 Motivation

SM neutrinos:

We have detected neutrinos 50 years ago

Least known particles in the SM

What we don’t know:

• Origin of mass

• Majorana or Dirac probe them in cosmology • Mass ordering D1 • Total mass ⌫ • Lifetime

…… D2

1 Why cosmology?

Best constraints on (m⌫ , ⌧⌫ ) CMB LSS

Planck SDSS

Huge number of neutrinos

Neutrinos are non-relativistic

Cosmological time/length

2 Why cosmology?

Best constraints on (m⌫ , ⌧⌫ ) Near future is exciting! CMB LSS CMB LSS

Planck SDSS CMB-S4 Euclid

Huge number of neutrinos Passing the threshold:

Neutrinos are non-relativistic ( m⌫ ) . 0.02 eV < 0.06 eV

“Guaranteed”X evidence for ( m , ⌧ ) Cosmological time/length ⌫ ⌫ or new physics

2 Massive neutrinos in structure formation ⇢ /⇢ cdm ⌘ cdm cdm 1 t H ⇠

Dark matter/baryon

3 Massive neutrinos in structure formation ⇢ /⇢ cdm ⌘ cdm cdm 1 t H ⇠

Dark matter/baryon

1 t t H ⇠

cdm Neutrinos ⌦⌫

Neutrinos don’t clump efﬁciently Lesgourgues, Pastor 2006

Increase H, shorten the time for CDM growth，suppress cdm 3 Decaying neutrinos in structure formation

1 t H ⇠

Dark matter/baryon

Neutrinos

4 Decaying neutrinos in structure formation

1 t H ⇠

Dark matter/baryon

Assuming daughter are massless

Neutrinos Daughter radiation ⌦⌫ a anr adec Serpico 2007 4 Serpico 2009 Decaying neutrinos in structure formation

Numerical simulation: modiﬁed CLASS code

0 Mν =0.25 eV ﬁx H0 k=0.1 h/Mpc

[%] -1 1 )- 0 = ν -2 CDM,m δ / ⌫ =0 ν -3 3 ⌫ = 10 km/s/Mpc

CDM,m 4 δ

( ⌫ = 10 km/s/Mpc -4

anr adec adec

10-3 10-2 10-1 1 Scale Factor a degenerate neutrino masses and massless daughters Chacko, Dev, PD, Poulin, Tsai (to appear) 5 Degeneracy in mass and lifetime

0 k=0.1 h/Mpc ﬁx H0

[%] -1 1 )- 0 = ν -2 (M⌫ , ⌫ ) CDM,m δ

/ (0.25, 0) ν -3 (0.30, 102.9) CDM,m

δ 3.8 ( -4 (0.40, 10 )

10-3 10-2 10-1 1 Scale Factor a

Can we measure M ⌫ , ⌫ independently ?

6 Degeneracy in mass and lifetime

0 k=0.1 h/Mpc ﬁx H0

[%] -1 1 )- 0 = ν -2 (M⌫ , ⌫ ) CDM,m δ

/ (0.25, 0) ν -3 (0.30, 102.9) CDM,m

δ 3.8 ( -4 (0.40, 10 )

10-3 10-2 10-1 1 Scale Factor a

Can we measure M ⌫ , ⌫ independently ?

Resolution:

Need measurements at earlier time/ higher redshift z

Need precision . 1% 6 Breaking the degeneracy

Preliminary

3.4

Euclid 2021 ⌫

3.07 10

2.74 can probe 0.5 . z . 2 Log 2.42

0.208 0.235 0.262 0.289 2.42 2.74 3.07 3.4 from 2D map to 3D map m⌫ Log10⌫ P with ~ 0.1 - 1% precision For mock data M⌫ =0.25 eV 3 ⌫ = 10 km/s/Mpc

7 2D parameter space Existing constraints:

Non-radiative decay lifetime: CMB neutrino free-streaming Archidiacono, Hannestad 2014

Total mass: M⌫ m⌫ < 0.23 eV Planck+SDSS ⌘ X Assuming neutrinos are stable

1010 CMB neutrino free 109 -streaming 108 107

] 106 5 Mpc

/ 10 s / 104 km [

ν 3 Γ 10 102 10 Log Scale 1 Planck+SDSS Linear Scale 0 0.06 0.1 0.2 0.3 0.5 0.7 0.9

Mν [eV] 8 2D parameter space

The best exclusion for non-radiative decay neutrino lifetime!

CMB-S4+Euclid can measure M ⌫ , ⌫ independently

1010 CMB neutrino free 109 Preliminary -streaming 108 107

] 106 5 Mpc

/ 10 s / Γ = H(anr) 104 ν km [

ν 3 Γ 10

102 CMB-S4+Euclid Planck+SDSS (this work) 10 Log Scale 1 Planck+SDSS Linear Scale 0 0.06 0.1 0.2 0.3 0.5 0.7 0.9

Mν [eV] 8 2D parameter space

The best exclusion for non-radiative decay neutrino lifetime!

CMB-S4+Euclid can measure M ⌫ , ⌫ independently Interplay with terrestrial neutrino mass measurements: e.g KATRIN

1010 CMB neutrino free 109 Preliminary -streaming 108 7 10 KATRINKATRAN

] 6 ] 106 5 Mpc 5 Mpc / / 10 s s / / a ) Γν = H(anr 104 ν km km [ [ ν ν 3 Γ 3 Γ 10

102 CMB-S4+Euclid Planck+SDSS (this work) 10 Log Scale 1 Planck+SDSS Linear Scale 0 0.06 0.1 0.2 0.3 0.5 0.7 0.9

Mν [eV] 8 Conclusions • The non-radiative decay lifetime of neutrino is poorly constrained. • Current CMB and LSS data place the best constraint on both neutrino mass and lifetime • Near future experiments could break the degeneracy and measure the mass and lifetime separately.

DESI (2019) Euclid (2021) LSST (2023) CMB-S4 (202?) Near future precision cosmology can tell us a lot about neutrino physics and much more! 9 Thank you! Decaying neutrinos in structure formation

m⌫ a ¨ 2 ˙ 6 ⌦⌫ (⌘) cdm(a) 3 da ⌦⌫ (a) cdm + cdm 2 1 cdm m =0 exp ⌘ ⇡ ⌘ ⌦tot ⌫ (a) / 5 a ⌦tot ✓ ◆ ) cdm  Zai q 1 1 2 1(a

0 0 Mν =0.25 eV ﬁx H0 Mν =0.25 eV ﬁx H0

[%] k=0.1 h/Mpc

[%] 2 -1 - 1 1 )- 0 )- = 0 ν = -2 Numerical ν -4 Numerical m CDM,m

Analytic cb, Analytic δ / P ν / -3 ν 6 ⌫ =0 m - ⌫ =0 CDM,m 3 cb, 3 δ P ( ⌫ = 10 km/s/Mpc ⌫ = 10 km/s/Mpc -4 4 ( 4 ⌫ = 10 km/s/Mpc -8 ⌫ = 10 km/s/Mpc

10-3 10-2 10-1 1 10-5 10-4 10-3 10-2 10-1 1 Scale Factor a k [h/Mpc] 10