cosmological mass bounds on hot-dark matter axions

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]

http://www.ba.infn.it/new/barilogo.html

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


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 .


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


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


This talk

Hadronic axion windowma~ O(eV), fa~106 GeV

COSMOLOGICAL AND ASTROPHYSICAL AXION LIMITS

DARK MATTER CANDIDATES


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


POWER SPECTRUM OF MATTER DENSITY FLUCTUATIONS

xx

Density contrast

2( ) kP k

Power spectrum


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


NEUTRINO MASS LIMITS

[Fogli et al., arXiv: 0805.2517]


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


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


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:


Thank you!

cosmological mass bounds on hot-dark matter axions

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