Axions as Dark matter candidates. Javier Redondo Ramón y Cajal fellow Universidad de Zaragoza (Spain)

Transcription

1 Axions as Dark matter candidates Javier Redondo Ramón y Cajal fellow Universidad de Zaragoza (Spain)

2 The strong CP problem Flavor conserving CP-violation in the SM, one phase L SM ū d... L m u e i m d e i u d A... g R = QCD + N q s 8 G e G QCD J µ A µj µ 5 q g This CP violation is not observed (Neutron electric dipole moment,..) d n O(10 15 )[e cm] predictions d exp n < [e cm] < 10 10!!

3 The strong CP problem and axions In pure SM the vacuum energy has a minimum at =0 exp Z x V ( ) = Z DA i µ exp S e [,A i µ] exp i s 8 G G e < exp Z x V (0) V ( ) here we don t know it so well but theta is a constant of nature... If is a dynamical field (axion!), will roll down to zero, problem solved! s 8 G e G! s 8 G e G (x)+ 1 2 ( µ )( µ )f 2 a (x) = a(x) f a new energy scale!

4 Simple model KSVZ - Peccei-Quinn symmetry, color anomalous, spontaneously broken at f a L = L SM + i QDQ (y Q L Q R +h.c) 4 + µ 2 2 (x) = (x)e i a(x) fa - At energies below f a (SSB) L 1 2 ( a)2 + s 8 G e G a f a - At energies below, 0 QCD a 0... mixing ~fa ~GeV axion mass m a ' m f f a 6meV 109 GeV f a couplings L a,i = X N c N,a N µ 5 N a f a + c a 2 F µ e F µ a f a +... nucleons... photons... mesons... ENERGY

5 Landscape, what do we know? If axions exist, they are very light and VERY weakly interacting!

6 Landscape, what do we know? Dark Matter Astro-hints? Excluded If axions exist, they are very light and VERY weakly interacting!

7 Vacuum realignment, strings, walls... - Axions: small mass, small interactions, thermal DM - non-thermal DM, Initial conditions Domains=horizon Cosmic strings time, 1/T Damped oscillations=cdm =0 strings SSB QCD D. Walls

8 Vacuum realignment, strings, walls... - Axions: small mass, small interactions, thermal DM - non-thermal DM, Initial conditions SCENARIO-I realignment+cs+dws time, 1/T SSB Domains=horizon Cosmic strings O(1) inhomogeneous DM =0 QCD-horizon scale miniclusters QCD D. Walls Damped oscillations=cdm strings

9 Vacuum realignment, strings, walls... - Axions: small mass, small interactions, thermal DM - non-thermal DM, Initial conditions SCENARIO-II realignment only time, 1/T Damped oscillations=cdm SSB INFLATION!! =0 QCD D. Walls strings

10 Axion DM, how much 10 1 obs,dm Axion decay DM density today a kev cm I =0.01 I =0.1 cosmic strings + domain walls I =1 thermal a 10 4 realignment 10 5 µev mev ev m a

11 why decreases with the mass? - Energy density redshifts as matter, from the onset of oscillations a (t) 2 I 4 QCD R1 R(t) 3 / 2 I 4 QCDma 3/2 dilution factor R1 R 0 3 T0 T 1 3 T 0 p H1 m Pl 3 T 0 p ma m Pl 3 / m 3/2 a Smaller mass axions, start oscillating later, and get less diluted... a(t) t osc 1 m a m a t 1 - with T-dependence a (t 0 ) / 2 Im 7/6 a time

12 Axion DM, how much II I Excluded (too much DM) I Astro-hints? Excluded If axions exist, they are very light and VERY weakly interacting!

13 Axion DM, isocurvature issue and BICEP2 SCENARIO-II - Axion fluctuates during inflation (entropy perturbations) P iso = dhn ai n a dha2 i a 2 I = H2 I 2 a 2 I = H2 I 2 f 2 a 2 I insisting on axion DM I = I (f a ) Constraint, f a (H I ) f a H I BICEP2 would exclude SC-II in the simplest models... EXCLUDED of course, there are plenty of ways out...

14 Detecting Axions

15 Detecting Axion (Dark Matter) in the lab CDM ' 0.3 GeV cm 3 = m an a ' 1 2 m2 af 2 a 2 O(10 19 ) velocities in the galaxy phase space density occupation number is HUGE! v. 300 km/s 10 3 c n a 4 p µev m a 4 treat it like a classical coherent (NR) field Roughly... a(t) =a 0 cos(m a t) Fourier-transform a(x) ' m a (1 + v 2 /2+...) = m av 2 2!! 10 6! m a

16 Detecting Axion (Dark Matter) in the lab mass nev µev 0.1 mev Spin precession Cavity experiments Atomic transitions? CASPER (Mainz-Berkely) ADMX, ADMX-HF,Yale,WISPDMX CARRACK, IAXO, RADES... Oscillating EDM Axion-photon conversion Axion-electron absorption d n O(10 34 ) cos(m a t)[e cm] B B Graham, Rajendran 2011 Sikivie 2014

17 Axion DM in a B-field L I = c a 2 a f a B E - In a static magnetic field, the oscillating axion field generates EM-fields L I = c a 2 (t) B ext E B-field - Electric fields of order E O(10 12 V/m) B ext c a cos(m a t) - oscillating at a frequency given by the axion mass Do not depend on mass or coupling strength!

18 - Haloscope (Sikivie 83) Amplify resonantly the EM field in a cavity Cavity experiments P Q E a 2 (Vm a )G (on resonance) - Past experiments Florida U., RBF, ADMX, CARRACK - Future endeavors: ADMX, ADMX-HF, YMCE, CAPP - Parameters unexplored at low and high masses: WHY? Cylindrical cavity (h/r=b) like ADMX but scaled - Signal (V / m 3 a ) P out / Vm a 1 m 2 a - Noise P noise = T sys a / m 2 a - Signal/noise in a of time, t, - Scanning rate 1 d m a m a dt / c4 m 9 a S N = P out P noise p at c KSVZ [GHz] ADMX Scenario DFSZ II ADMX RBF ADMX2 UF ADMX-HF Very easy, but needs large magnet volume! CARRACK? m a [µev] IAXO I Very complicated, needs new ideas

19 Axion DM searches with IAXO? - Length = 20 m - Magnetised radius ~ 1 m - Peak value ~ 5.4 T - Average in bore 2.5 T - Available T ~ 4.5 K (but warm bores in design) 2 1 y[m] 0 field map of transverse cut x[m 1 - Sensitivity 2 x[m] Big cavity (realistic) Many flat (exploit the huge volume) (very speculative, R&D needed!)

20 Dish antenna experiment? P E 2 A dish B 5T c 2 2 A dish 1m 2 Watt spherical reflecting dish

21 Dish antenna experiment? GHz A=10m2,T=5K, B=5T, t=1year, A=10m2, T=QL, B=10T, t=1year, CDM 0.3GeV cm 3 c ADMX ADMX BFRT ADMX II ADMX HF CARRACK O(10^6) channels KSVZ DFSZ HS HKS Post Inflation PQ DS Pre Inflation PQ m a ev broadband! :-)!! O(1) measure 1/octave of a decade with the same detector at the same time

22 possible boost Enhance the emissivity by multilayers of dielectric E a E a N GHz back production and all reflexions... 4 layers tuned lambda/ Increases sensitivity but losses bandwidth boost eff factor m a ev

23 Dish antenna and miniclusters - Typical Dish antenna experiments fall a bit short, if the DM density is just CDM =0.3GeV/cm mev range is most interesting in Scenario-II Dish IAXOQL S-II predicts miniclusters of axion CDM M mc M mc/ acdm O(1) Zurek et al 07, See also Kolb & Tkachev 94 c 10 8-Dish IAXOSYS 1 Scenario II m a [ev] 10 - Encounter with the Earth (every 10 4 years) CDM 10 6,Q a 10 9,t 3days - Even with a modest realistic experiment one can get a huge signal! (if lucky...)

24 Detecting Axions Solar Axions 5th forces Photon regeneration IAXO CDR 2014 Arvanitaki Geraci PRL 2014 ALPS-II TDR 2013

25 Detecting Axions Solar Axions 5th forces Photon regeneration IAXO CDR 2014 Arvanitaki Geraci PRL 2014 ALPS-II TDR 2013

26 Detecting Axions Solar Axions 5th forces Photon regeneration IAXO CDR 2014 Arvanitaki Geraci PRL 2014 ALPS-II TDR 2013

27 Detecting Axions Solar Axions 5th forces Photon regeneration IAXO CDR 2014 Arvanitaki Geraci PRL 2014 ALPS-II TDR 2013

28 Detecting Axions Solar Axions 5th forces Photon regeneration IAXO CDR 2014 Arvanitaki Geraci PRL 2014 ALPS-II TDR 2013

29 A developing picture 5th forces? Atomic transitions? Dish Antenna? IAXO DM IAXO DM osc. EDM ADMX ADMX-HF

30 Conclusions - Axion DM - well motivated and testable - but underrepresented - key targets still not covered - plenty of new ideas - Cavity experiments on the run - micro-ev range by ADMX, ADMX-HF, CAPP? - lower masses, IAXO? - Dish antenna? - Millions of things not covered here - Axions in BSM physics - Axion DM astrophysics (BEC?, miniclusters?, BHs?)

31 Thank you!!!