G. Mangano INFN Napoli NOW 2014. We know a lot about neutrino properties from lab experiments. We...
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Precision Cosmology and Neutrino Properties G. Mangano INFN Napoli NOW 2014
G. Mangano INFN Napoli NOW 2014. We know a lot about neutrino properties from lab experiments. We would like to know more exploiting their impact on cosmological
We know a lot about neutrino properties from lab experiments.
We would like to know more exploiting their impact on cosmological
and astrophysical observables. Precision Cosmology: precise
observations which fit the standard model extremely well. But: as
soon as we move away from our comfortable standard? Robust vs. weak
predictions: which is the case for neutrino properties ? NOW
2014
Slide 3
Are there neutrinos in the universe? How many of them? (the
long tale of N eff ) Neutrino mass: universe better than labs ?
Oscillations and neutrino asymmetries Sterile states ? Any relation
with dark matter ? Majorana or Dirac particles ? NOW 2014
Slide 4
BBN and CMB probe the light particle content at different
epochs: both require relativistic species in addition to photons
NOW 2014 For BBN: N eff = 3 is a good fit (see later) BBN requires
electron neutrinos!
Slide 5
CMB fixing the angular scale of acoustic peaks and z eq, a
larger N eff gives a higher expansion speed, a shorter age of the
universe T at recombination. Diffusion length T Sound horizon T N
eff = 3 is a good fit (see later) NOW 2014
Slide 6
Perturbation effects: gravitational feedback of neutrino free
streaming damping anisotropic stress contributions c vis
:velocity/metric shear anisotropic stress relation (Hu 1998) NOW
2014 Trotta & Melchiorri 2005
Slide 7
CMB and BBN are quite consistent NOW 2014 Ade et al. 2013
(Planck XVI)
Slide 8
both 4 He mass fraction Y p and 2 H/H are increasing functions
of N eff : change of expansion rate v e distribution crucial in
weak rates baryon density basically fixed by CMB! (but still 2 H/H
can varies a lot) crucial inputs: experimental values nuclear rates
NOW 2014 Cyburt 2004
Slide 9
4 He still affected by a remarkable systematic uncertainty
Recent re-analysis 2 H/H is presently quite well determined, thanks
to new very metal poor system measurements (Cooke et al. 2013) NOW
2014 Izotov & Thuan 2010 Aver et al. 2010 Aver etl. 2012 Aver
et al. 2013 Izotov & Thuan 2014 Mangano & Serpico 2011
Slide 10
Several claims, spanning from Evidence for extra neutrinos to
No room for extra neutrinos Conservative estimate: N eff < 4
(still !) One example: for Planck baryon density a higher deuterium
N eff smaller than 3 (2.7)? Maybe, or a larger S-factor for d(p, )
3 He, as in the theoretical estimate of Marcucci et al. (2005) NOW
2014
Slide 11
News from Planck: a narrower 95 % C.L. range for N eff, but
still Inconclusive. H 0 problem: NOW 2014 Ade et al. 2013 (Planck
XVI) 3.40.7 3.30.5 3.60.5 3.50.5
Slide 12
Mass bounds Laboratory is still missing! 2 eV for e Katrin wil
tell us more (when?) Cosmology blind to neutrino mass till recent
times. CMB: For the expected mass range the main effect is around
the first acoustic peak due to the early integrated Sachs-Wolfe
(ISW) effect; Planck: gravitational lensing. Increasing neutrino
mass, increases the expansion rate at z >1 and so suppresses
clustering on scales smaller than the horizon size at the
nonrelativistic transition (Kaplinghat et al. 2003 ; Lesgourgues et
al. 2006 ). Suppression of the CMB lensing potential. NOW 2014
Slide 13
Total neutrino mass also affects the angular-diameter distance
to last scattering, and can be constrained through the angular
scale of the rst acoustic peak. Degenerate with (and so the derived
H0 ) Including BAO constraint is much tighter: m v < 0.98 eV
(CMB) m v < 0.32 eV (CMB + BAO) NOW 2014
Slide 14
Early times: Kinetic and chemical equilibrium MeV scale (set by
G F and m 2 s) : freezing of weak interaction processes
distributions mixed up, depending on mixing angles f a slightly
distorted N eff = 3.046
Slide 15
density matrix formalism aa occupation number ab ab ab mixing
vac vacuum oscillations: M 2 /2p matter matter term: 2 1/2 G F n i
+ 8 2 1/2 G F p T 0 0 /3M 2 W,Z C: collisional integral (loss of
coherence and distribution re-shuffling) NOW 2014 Stodolski 1987
Raffelt ad Sigl 1993 .
Slide 16
When oscillations matter: Lepton asymmetries expected quite
small in (standard) leptogenesis unless leptogenesis takes place
well below the EW breaking scale NOW 2014
Slide 17
The value of 13 is crucial (and to a minor extent the mass
hierarchy) NOW 2014 Pastor et al 2011 GM et al 2012
Slide 18
T mix >> T dec N eff = 3.046 T mix 3 unless = 0 f a
MIXING EQUILIBRIUM f b SINK & SOURCE , e NOW 2014 Pastor, Pinto
& Raffelt 2009
Slide 19
the bounds: scanning all asymmetries compatible with BBN N eff
< 3.2 -0.2 (-0.1) 0.15 (0.05) NOW 2014 GM et al 2012
Slide 20
N eff 3.2 still compatible with slightly degenerate neutrinos N
eff 3.2 some extra dark radiation required or higly non-thermal
neutrino distribution, or both After Planck I results still
inconclusive ! NOW 2014
Slide 21
Hints for sterile neutrino states from long(short) standing
anomalies LSND, MiniBoone Reactor anomaly Gallium anomaly m v eV,
sin 2 as 10 2 Too many sterile neutrinos in the early universe,
produced via oscillations NOW 2014
Slide 22
Unless there is a fine tuning, the typical outcome is either
too few or too many (and too heavy ! ) 1. The standard case 2.
Large lepton asymmetries 3. secret sterile interactions (unlikely 2
for Ockham) NOW 2014
Slide 23
Planck analysis (Planck XVI 2013) N eff < 3.91 m s < 0.59
eV N eff < 3.80 m s < 0.42 eV (including BAO) NOW 2014
Slide 24
The standard case (e.g. Mirizzi et al 2013) NOW 2014
Slide 25
Lepton asymmetry suppresses sterile Production V = 2 G F L v
NOW 2014 L v = 10 -4 Mirizzi et al. 2012
Slide 26
Large sterile self-interactions suppress sterile production due
to large potential (Hannestad et al 2013) G X larger than Fermi
constant. OK for N eff smaller than 1. BBN ? See Saviano talk NOW
2014 Saviano et al 2014
Slide 27
Can we distinguish Majorana or Dirac neutrinos from cosmology ?
Relativistic regime: NO Structure formation: NO Leptogenesis: YES
Direct detection: YES ! (really demanding) NOW 2014
Slide 28
Neutrino capture on 3 H (PTOLEMY R&D, Katrin too low 3 H
mass) e + 3 H e + 3 He Dirac: only the left-helicity neutrinos
& anti-neutrinos cannot be captured. Majorana: both left- and
right-helicity neutrinos, capture rate doubled PTOLEMY (100g 3 H)
:4 events yr -1 Dirac 8 events yr -1 Majorana NOW 2014 Weinberg
1962 Cocco et al 2007 Lunardini et al. 2014
Slide 29
NOW 2014 What we would like to know about neutrinos ? mass
Majorana or Dirac Other neutrinos (sterile, mirror,) Cosmological
data are precise today (% level) & Standard cosmological model
is extremely on shape !! Beware degeneracies and epicycles !!