THE HUNT FOR NEUTRINO HIERARCHY · ⌫ = 0.06 eV COrE+BAO,M ﬁd ⌫ = 0.06 eV COrE,M ﬁd ⌫ =...

THE HUNT FOR NEUTRINO HIERARCHYMartina Gerbino

OKC&NORDITA, Stockholm University

Neutrino Oscillation Workshop 2016, Otranto

6 Sep 2016 based on Gerbino,Lattanzi,Mena,Freese,in prep

Martina Gerbino, NOW 2016

Roadmap

• The characters: neutrinos in cosmology

• A method to quantify cosmological sensitivity to the hierarchy

• Results from current and forecasted data

• Conclusion

500 1000 1500 2000 25000.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

{

{3H{+1LC {ê2p@109

mK2 D

Smn = 0.06 eVSmn = 0.2 eVSmn = 0.4 eVSmn = 0.6 eVSmn = 0.8 eV

Massive neutrinos alter background and perturbation evolution

Abazaijan+,2015

WMAP9 data end here

Linear regime ends roughly here

Martina Gerbino, COSMO-16

credits: M.Lattanzi

3 active families, sub-eV masses Relativistic at early times, non-relativistic today

(Almost) peculiar effects on cosmological observables


Where are we?Present

Mnu<0.46eV (Planck TT,TE,EE+lowP) Mnu<0.17eV (Planck TT,TE,EE+lowP+BAO)

(see e.g. Planck collaboration XIII)

Mnu<0.13eV (Planck TT,TE,EE+lowP+BAO+ matter power shape) (see e.g. Cuesta et al, 2015)

Mnu<0.12eV (Planck TT,TE,EE+lowP+Lya) (see e.g. Palanque-Delabrouille et al, 2015)

Future sigma(Mnu)~0.02eV (COrE,Stage4,DESI,Euclid,…)


Where are we?Present

Mnu<0.46eV (Planck TT,TE,EE+lowP) Mnu<0.17eV (Planck TT,TE,EE+lowP+BAO) Mnu<0.13eV (Planck TT,TE,EE+lowP+BAO+

matter power shape) Mnu<0.12eV (Planck TT,TE,EE+lowP+Lya)

Future sigma(Mnu)~0.02eV (COrE,Stage4,DESI,Euclid,…)

Questions: • Will we be able to measure

Mnu? • Will we be able to

discriminate the hierarchy? • Can we provide a

statistically robust answer?


The standard methodMnu

(+other cosmological parameters)

Degenerate spectrum: m⌫,i = M⌫/3, i = 1, 2, 3Different authors obtain upper bounds from current data approaching the

“critical” value of 0.1 eV. These results suggest that IH starts to get under

pressure from cosmology. […] Such a claim should be based on a proper statistical analysis. The question to be answered is, whether the hypothesis

of IH can be rejected with some confidence against NH.

(Hannestad&Schwetz,2016)

0.1eV


The proposed methodMnu + other cosmological parameters

+ h Hyper-parameter h flat in [0,1]

h<0.5 h>0.5

NORMAL HIERARCHY INVERTED HIERARCHYm⌫,1 = mlight

m⌫,2 =q

m21 +�m2

12

m⌫,3 =q

m21 +�m2

13

m⌫,3 = mlight

m⌫,1 =q

m23 +�m2

13

m⌫,2 =q

m21 +�m2

12

Advantages: • neutrinos modelled with exact mass spectrum • information from oscillations taken into account • quantifies sensitivity to the hierarchy • takes into account uncertainties related to the hierarchy


Sensitivity to the hierarchy: current data

Mild preference for NORMAL HIERARCHY (~5:3) CMB only mildly sensitive (with polarisation)

Sensitivity increases when BAO are added

0.0 0.2 0.4 0.6 0.8 1.0

htype

0.0

0.2

0.4

0.6

0.8

1.0

P/P

max

TT+lowP

TT+lowP+BAO

TT,TE,EE+lowP

TT,TE,EE+lowP+BAO

Preliminary


Constraints on Mnu: current data

0.25 0.50 0.75 1.00

M⌫ [eV]

0.0

0.2

0.4

0.6

0.8

1.0

P/P

max

TT+lowP

TT+lowP+BAO

TT,TE,EE+lowP

TT,TE,EE+lowP+BAO

Mmin⌫ M⌫ 0.740 eV




95%, Planck TT+lowP

95%, Planck TT+lowP+BAO

95%, Planck TT,TE,EE+lowP

95%, Planck TT,TE,EE+lowP+BAO

Mmin⌫ = 0.059 eV

Preliminary


Sensitivity to the hierarchy: forecasts

0.0 0.2 0.4 0.6 0.8 1.0

htype

0.0

0.2

0.4

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0.8

1.0

P/P

max

COrE,Mfid⌫ = 0.06 eV

COrE+BAO,Mfid⌫ = 0.06 eV

COrE,Mfid⌫ = 0.1 eV

COrE+BA=,Mfid⌫ = 0.1 eV

If Mnu is minimal, 10:1 odds for NH!!! If Mnu=0.1eV, cosmology almost insensitive

Mfid⌫ = 0.1 eV

Mfid⌫ = 0.06 eV

Preliminary


0.10 0.15 0.20 0.25

M⌫ [eV]

0.0

0.2

0.4

0.6

0.8

1.0

P/P

max

COrE,Mfid⌫

= 0.06 eV

COrE+BAO,Mfid⌫

= 0.06 eV

COrE,Mfid⌫

= 0.1 eV

COrE+BA=,Mfid⌫

= 0.1 eV


M⌫ = 0.112+0.037�0.040 eV

95%, COrE+BAO, minimal mass

95%, COrE+BAO, 0.1eV fiducial

Constraints on Mnu: forecastsPreliminary


Implications for 0n2b: present

0.03 0.1

0.01

0.03

0.1

Mn @eVD

mbb@eVD

KamLAND-Zen, optimistic

KamLAND-Zen, pessimistic

0n2b searches almost competitive cosmology (provided nuclear modelling under control)

Preliminary

Cosmology+ oscillations

only


0.03 0.10.003

0.01

0.03

0.1

Mn @eVDmbb@eVD

KamLAND-Zen H90%L

nEXO 10yrwê Ba tag H90%L

0.03 0.10.003

0.01

0.03

0.1

Mn @eVD

mbb@eVD

KamLAND-Zen H90%L

nEXO 10yrwê Ba tag H90%L

Implications for 0n2b: forecasts

Mfid⌫ = 0.06 eVMfid

⌫ = 0.1 eV

PreliminaryCosmology+oscillations only

If Mnu=0.1eV, sigma(mbb)~10meV could guarantee 0n2b measurement

If Mnu minimal, hard times


CONCLUSIONS

• Tight bounds on neutrino mass from cosmology • Inverted hierarchy in trouble: how much? • By introducing an hyper-parameter we can: 1)

easily account for exact neutrino mass spectra; 2) quantify sensitivity to the hierarchy; 3) take

into account uncertainty due to imperfect knowledge of the hierarchy

• NH favoured 5:3 by current data • NH favoured 10:1 by future measurements, if the

mass is minimal

THE HUNT FOR NEUTRINO HIERARCHY · ⌫ = 0.06 eV COrE+BAO,M ﬁd ⌫ = 0.06 eV COrE,M ﬁd ⌫ =...

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