cosmological mass bounds on hot-dark matter axions
DESCRIPTION
NOW 2008- Neutrino Oscillation Workshop Conca Specchiulla, September 6-13 2008. Cosmological mass bounds on hot-dark matter axions. Alessandro MIRIZZI (MPI, Munich). [based on works in collaboration with S.Hannestad, G.G. Raffelt, Y.Y.Y. Wong]. OUTLINE. Strong CP problem and the axions - PowerPoint PPT PresentationTRANSCRIPT
Cosmological mass Cosmological mass boundsbounds
on hot-dark matter on hot-dark matter axionsaxions
Alessandro MIRIZZIAlessandro MIRIZZI
(MPI, Munich)(MPI, Munich)
NOW 2008- Neutrino Oscillation WorkshopNOW 2008- Neutrino Oscillation Workshop
Conca Specchiulla, September 6-13 2008Conca Specchiulla, September 6-13 2008
[based on works in collaboration with S.Hannestad, G.G. Raffelt, Y.Y.Y. Wong][based on works in collaboration with S.Hannestad, G.G. Raffelt, Y.Y.Y. Wong]
OUTLINE
• Strong CP problem and the axions
• Axions and large-scale structures
• Cosmological mass limit
• Implication for axion search (CAST experiment)
• Conclusions
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
THE STRONG CP PROBLEM
The QCD Lagrangian includes a term which violates CP (and T)
arg det QCD qM
250.63 10 cmnd e
15(0.04 2.0) 10 cmnd e
where
Prediction of an electric dipole moment for the neutron:
Present experimental limit :
910 Why so small ?
8s
CP G G
L
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
THE PECCEI-QUINN MECHANISM
Introduction of a new global U(1)PQ simmetry, spontaneously broken at a scale fa.
Existence of a massless pseudoscalar field a(x), the axion, interacting with the gluon field.
2
1
2 8s
aa
a a G Gf
L L
Peccei & Quinn 1977, Wilczek 1978, Weinberg 1978
( )
a
a x
f Re-interpret as a dynamical variable:
• PQ Symmetry
Introduce a symmetry that results in a term which dynamically minimize .
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
aa
V(a)V(a)
0 0
Potential (mass term)Potential (mass term)induced by Linduced by La a drivesdrives
a(x) to CP-conservinga(x) to CP-conservingminimumminimum
CP-symmetry CP-symmetry dynamically restoreddynamically restored
1/ 2
6
6.0
1 /10aa a
f mz eVm
z f f GeV
At low energy (QCD) the gga vertex generates the potential V(a) which has its minimum at a0=0, restoring dynamically CP-simmetry.
Axions pick up a small mass
Axions generically coupleAxions generically couple to gluons and mix with to gluons and mix with 00
gluongluon
aagluongluon
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
AXION PROPERTIES
Nucleon couplingNucleon coupling(axial vector)(axial vector)
af2
CL NN
a
NaN 5
af2
CL NN
a
NaN 5
NN
NNaa
Electron couplingElectron coupling(optional (optional absent absent for hadronic axionsfor hadronic axions))
af2
CL ee
a
eae 5
af2
CL ee
a
eae 5
ee
eeaa
Gluon couplingGluon coupling(Generic property)(Generic property)
aG~Gf8
La
saG
aG~G
f8L
a
saG
aa
GG
GG
Photon couplingPhoton couplingaBEgaF~F
4
gL a
aa
aBEgaF~F
4
gL a
aa
92.1NE
f2g
aa
92.1NE
f2g
aa
aa
Pion couplingPion coupling a...)(ff
CL 0
a
aa
a...)(
ffC
L 0
a
aa
aa
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
This talk
Hadronic axion windowma~ O(eV), fa~106 GeV
COSMOLOGICAL AND ASTROPHYSICAL AXION LIMITS
DARK MATTER CANDIDATES
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
DARK-MATTER AXIONS
log(log(aa))
log(mlog(maa))
MM
30 eV30 eV100 meV100 meV
CDCDMM
HDHDMMAxionsAxions
Thermal RelicsThermal RelicsNon-ThermalNon-Thermal
RelicsRelics
log(log())
log(mlog(m))
MM
30 eV30 eV
CDCDMM
HDHDMM
3 GeV3 GeV
NeutrinosNeutrinos
Thermal RelicsThermal Relics
THERMAL PRODUCTION OF AXIONS
If fa < 1.2 ×1012 GeV there would be a primordial population of axions produced in hot thermal plasma [Turner (1987), Masso’ (2002)]
Freeze-out temperature
If axions were sufficiently strong interacting (fa < 3 ×107 GeV, ma > 0.2 eV) they decouple after QCD phase transition (T < 200 MeV). The most generic interaction process involves hadrons rather than quarks and gluons that would be relevant at earlier epochs.
There would be a background of low-mass (~ eV) relic axions
Massive neutrinos affect Large Scale Structures.
They smooth out the distribution: no small scale structures.
Cold Dark Matter(no neutrino mass)
Hot + Cold Dark Matter(non-zero neutrino mass)
S. Dodelson, ‘04
Low mass thermal relics affect structure formation because they are source of hot dark matter
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
POWER SPECTRUM OF MATTER DENSITY FLUCTUATIONS
xx
Density contrast
2( ) kP k
Power spectrum
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
Neutrinos affect the Power Spectrum of the 2-point density correlation function.
P(k)=A kn T2(k)
T2(k) = Transfer function
It is possible to obtain constraints on m
Neutrino Free Streaming P(k)/P(k) = -8 /m (Hu et al. 1998)
0 eV
0.3 eV
1 eV
Power suppression for FS 100 Mpc/h≲
S.Hannestad,hep-ph/0404239
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
NEUTRINO MASS LIMITS
[Fogli et al., arXiv: 0805.2517]
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
THERMALIZATION OF HADRONIC AXIONS
The Lagrangians relevant for axion decoupling processes are the following
0 0 0 2a aa
aC
f f
L
• Pion-axion interaction
a
Contact interaction
0a 0a 0a
1
0.0943 1a
zC
z
Choi & Chang, PLB 316, 51(1993); Hannestad, Mirizzi & Raffelt, JCAP 07 (2005) 02
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
Freeze-out temperatureCosmic thermal degrees offreedom at axion freeze-out
Present-day axion density*,
*,
( )
( ) 2S
aS
ng todayn
g decoupling
*, ( ) 3.91Sg today 3411 n cm
3112 n cm
AXION HOT-DARK MATTER
H
AXION HOT-DARK MATTER LIMIT FROM PRECISION DATA
Credible regions for neutrinos plus axions HDM (WMAP-5, LSS, BAO; SN-Ia)
Hannestad, Mirizzi, Raffelt & Wong [arXiV: 0803.1585]
Dashed (red) curves: Same with WMAP-3
HMRW [arXiv: 0706.4198]
Marginalizing over unknown neutrino hot-dark matter component
WMAP5, LSS, BAO, SN Ia
Hannestad, Mirizzi, Raffelt & Wong [arXiV:0803.1585]
WMAP3, small-scale CMB, HST, BBN, LSS, Ly
Melchiorri, Mena & Slosar [arXiV: 0705.2695]
1 eV (95% CL)am
0.4 eV (95% CL)am
NEW AXION MASS LIMIT
Our limit ma < 1 eV, corrisponding to fa> 5.7×106 GeV, is comparable with the one obtained with the globular-cluster. However, the globular cluster limit depends on axion-photon coupling that is rather model dependent.
Our limit closes the “hadronic axion window” left open by SN1987A arguments
New cosmological mass limit
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
IMPLICATION FOR AXION SEARCHES
Searches for solar axions: Axion helioscopes
Axion-photon oscillationPrimakoff process
• Tokyo axion helioscope Results since 1998
• CERN Axion Solar Telescope (CAST) Data since 2003
Sun Laboratory
CAST PHASE II AND OUR COSMOLOGICAL AXION MASS LIMIT PROBABLY CONNECT.
ga < 8.8 x 10-11 GeV-1 at 95% CL for ma < 0.02 eV
LIMITS FROM CAST-I AND CAST-II
CAST-I
ga < 2.2 x 10-10 GeV-1 at 95% CL for ma < 0.39 eV
CAST-II (Preliminary)
CONCLUSIONS
• For hadronic axions we find a new mass limit ma < 1 eV (95% CL), corresponding to fa> 5.7×106 GeV.
• It is comparable with the (model-dependent) limit obtained with the globular clusters.
• It closes the “hadronic axion” window.
• It is nicely complementary with the CAST search.
• If neutrino masses are detected in laboratory (KATRIN) : Less room for axions in the dark matter inventory.
Observations of the cosmological large-scale structure provide well-estabilished neutrino mass limit. We extend this argument to thermal relic axions:
Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008
Thank you!