G. ManganoG. Mangano NOW 2006NOW 2006 11
Interacting relic neutrinos Interacting relic neutrinos and free streaming and free streaming
Gianpiero ManganoGianpiero Mangano
INFN, Sezione di NapoliINFN, Sezione di Napoli
ItalyItaly
22G. ManganoG. Mangano NOW 2006NOW 2006
33G. ManganoG. Mangano NOW 2006NOW 2006
rimo exponitur usitatam neutrinorum naturam. Considerandum est utrum neutrinos habeant insolitum vel novum novorum entium commercium . Et circa hoc quaeruntur tres:Primo utrum entes in neutrinis defluant postquam neutrini segregati sunt ab electronibusSecundo utrum mundum sine neutrinis sint
Tertio utrum novorum entium commercio obscurae etiam levis materiae dispositionem mutetur
P
44G. ManganoG. Mangano NOW 2006NOW 2006
Pseudo-thermal distribution: T = 1.95 K
Number density ( v + v ): 112 cm-3 /flavor
Mean kinetic energy: 10-7(eV/m) eV
Direct searches:
GF2me Ev 10-50 (Ev/eV) cm2 hopeless ?
Standard picture
Indirect searches: cosmological observables
neutrino influence weak + gravity (T> 1 MeV)
gravity (T< 1 MeV)
Primo exponitur usitatam neutrinorum naturam
55G. ManganoG. Mangano NOW 2006NOW 2006
Neutrinos and CMB
Neff affects the radiation-matter equality point
ISW: Integrated Sachs-Wolfe Effect on acoustic peaks
The large number of cosmological parameters does not allow for a stringent limit
66G. ManganoG. Mangano NOW 2006NOW 2006
Neutrinos and Large Scale Structuresneutrinos suppress inhomogeneities which grow for gravitational instability until they become nonrelativistic
mv=1.2 eVmv=2.3 eV
mv=4.6 eV
mv=6.9 eV
Key parameters:
Mpchm
eVl
eV
mh
vv
nr
v
1
5.38
1.94
12
2/1
02
77G. ManganoG. Mangano NOW 2006NOW 2006
How strong are present (and future) bounds
on exotic features in v distribution?
General parametrization
nnanya yPa
e
yyf )(
1)(
2
Pn orthogonal polynomials with respect to Fermi-Dirac distribution
an in one to one correspondence with moments of distribution Qn
dyyyfQ nn 2)(41
3
2
3002
4
11
7
120
4
11058.0
TQN
TQeV
mh
eff
v
Articulus IPrimo utrum entes in neutrinis defluant postquam neutrini segregati sunt ab electronibus
88G. ManganoG. Mangano NOW 2006NOW 2006
A model Cuoco, Lesgourgues, G.M. and Pastor 2005
Extra neutrinos from out of equilibrium decay of scalars after neutrino decoupling
In the instantaneous decay limit at TD )( DTH
22* 2/)(
2
22
21
1)(
yy
ya eA
eyyf
Non thermal features in neutrino distributions
Effects seen in CMB and LSS
99G. ManganoG. Mangano NOW 2006NOW 2006
*2
202
7
12099.0104.3
)3(3
299.01
2.93
AyN
AeV
mh
eff
v
Bounds from BBN
particles (decoupled) should not contribute too much to the expansion rate H
A < 0.1 at 95% C.L.
1010G. ManganoG. Mangano NOW 2006NOW 2006
Present constraints from CMB (WMAP+ACBAR+VSA+CBI) and LSS (2dFGRS+SDSS) + SNIa data (Riess et al.)
Model: standard CDM + nonthermal v’s
Cl and P(k) computed using CAMB code (Lewis and Challinor 2002)
Likelihoods (using COSMOMC Lewis and Bridle 2002))
1111G. ManganoG. Mangano NOW 2006NOW 2006
Forecast:
“conservative”: Planck+ SDSS
“ambitious”: CMBPOL+ 40 h-3 Gpc survey with kmax=0.1 h Mpc-1
m0 and vh2 (q) large degeneracy
=vh2(93.2eV/m0)
1212G. ManganoG. Mangano NOW 2006NOW 2006
Articulus II
A neutrinoless Universe?
Models where v’s interact with light (pseudo)scalar particles
vv
chvvgvvhL jiijjiij ..
Beacom, Bell and Dodelson 2004
For the tightly coupled regime
v density strongly reduced, v’s play no role in LSS
Delay in matter domination epoch, different content in relativistic species after v decays (Neff=6.6 after decays)
Secundo utrum mundum sine neutrinis sint
couplings < 10-5 from several data (meson decay, 0, SN)
1313G. ManganoG. Mangano NOW 2006NOW 2006
Beacom, Bell and Dodelson 2004
1414G. ManganoG. Mangano NOW 2006NOW 2006
Including CMB in the analysis:
•No free streaming (no anisotropic stress) leads to
smaller effects on LSS (for massive v’s)
change of sub-horizon perturbations at CMB epoch
•Change of sound speed and equation of state of the the titghly coupled v - fluid
•v decays
larger Neff i.e. larger ISW effect for CMB
smaller effects on LSS (no v left at LSS formation epoch
Bell, Pierpaoli and Sigurdson 2005
Hannestad 2005
1515G. ManganoG. Mangano NOW 2006NOW 2006
Massless interacting Massive decaying
1616G. ManganoG. Mangano NOW 2006NOW 2006
Massive decaying
1717G. ManganoG. Mangano NOW 2006NOW 2006
Articulus IIITertio utrum novorum entium commercio obscurae etiam levis materiae dispositionem mutetur
Usual picture of Dark Matter: cold collisionless massive particles which decoupled around the weak scale for freeze-out of annihilation processes
Ex: neutralino in MSSM with mass of O(100 GeV)
Difficulties:
Excess of small scale structures
Far more satellite galaxies in the Milky Way than observed (from numerical simulation)
DM in the MeV range: SPI spectrometer on the INTEGRAL satellite observed a bright 511 KeV gamma line from the galactic bulge
Boehm, Fayet and Silk 2003 ee
1818G. ManganoG. Mangano NOW 2006NOW 2006
Framework: light (MeV) DM interacting with neutrinos
Several options for lagrangian density
Effects on cosmological scales: if DM - v’s scatterings at work during LSS formation we expect an oscillating behavior in the power spectrum (analogous to baryon – photon fluid during CMB epoch)
G.M., Melchiorri, Serra, Cooray and Kamionkowski 2006
1919G. ManganoG. Mangano NOW 2006NOW 2006
Constraints
from BBN: if DM annihilate with a picobarn cross section (correct relic density) then its mass cannot be too large or it would distrub light nuclide formation
from SNII: if DM also inteacts more than weakly with nucleons neutrinos woulb be kept in equilibrium inside a SN down to a lower temperature neutrinosphere
Serpico and Raffelt 2004
Fayet, Hooper and Sigl 2006
mDM > 10 MeV
2020G. ManganoG. Mangano NOW 2006NOW 2006
Effects on LSS•DM is not collisionless
•v’s are not free streaming
Scattering cross section depends upon the model
Ex. Scalar DM
2
4
222
24
1
3
4
3
4
DM
DMDM
vsc
DMF
DMDM
vsc
mhn
mm
Thn
mF mDM
mF = mDM
Scatterings leave an imprint only if efficient at very late times. Is this compatible with a picobarn DM annihilation cross section into neutrinos?
2121G. ManganoG. Mangano NOW 2006NOW 2006
NOT AT ALL !
mF mDM
mF = mDM
If annihilations freeze-out around mDM (order MeV), also scatterings do so!
DM relic abundance produced rather than e.g. an asymmetry in particle/antiparticle (as baryons, electrons…)
2222G. ManganoG. Mangano NOW 2006NOW 2006
Equation for velocity perturbations
Effect depends upon the parameter Q
mF mDM
mF = mDM
2323G. ManganoG. Mangano NOW 2006NOW 2006
Bounds on differential opacity Q from SDSS data
mDM mF scenario almost ruled out. Requires coupling of order one
mDM = mF still viable
2424G. ManganoG. Mangano NOW 2006NOW 2006
Very small effect on CMB sub-horizon scales
2525G. ManganoG. Mangano NOW 2006NOW 2006
Astrophysical bounds1. Neutrinos from SN 1987A from LMC were not disturbed by
scatterings with DM, since their spectrum at earth is in agreement with SN model
2. Scattering length for high energy neutrinos emitted by astrophysical sources:
2626G. ManganoG. Mangano NOW 2006NOW 2006
Conclusions
Worth studying exotic properties of v’s as a tool to explore physics beyond standard model
Keeping in mind Occam razor……
2727G. ManganoG. Mangano NOW 2006NOW 2006
2828G. ManganoG. Mangano NOW 2006NOW 2006
Degeneracies:
DM, Neff and m0
Neff >4 not forbidden
by BBN !
Future perspectives:
can we remove the
degeneracy?
2929G. ManganoG. Mangano NOW 2006NOW 2006
If we add extra relativistic particles the situation gets even more involved
For each non thermal model there is a “twin” model with extra thermal relativistic particles, sharing the same value of Neff, vh2 but a different value of the neutrino mass scale.
Way to solve the degeneracy:
independent information on the absolute neutrino mass scale (beta decay experiments)
*2
202
7
12099.0104.3
)3(3
299.01
2.93
AyN
AeV
mh
eff
v
NNeV
mh
eff
v
04.3 2.93
'02
Mpchm
eVl v
vnr
15.38
12
2/1
3030G. ManganoG. Mangano NOW 2006NOW 2006
If neutrino interacts during LSS formation the picture can be quite different even for massless v’s!
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