Searches for axions with the Searches for axions with the International AXion Observatory IAXO Igor G Irastorza Universidad de Zaragoza Workshop on Off-the-Beaten-Track Dark Matter Workshop on Off-the-Beaten-Track Dark Matter and Astrophysical Probes of Fundamental Physics Trieste, 13-17 April, 2015
Outline Outline Outline Outline Axion motivation: Axion motivation: Axion motivation: Axion motivation: – Strong CP problem Strong CP problem – Axions as CDM Axions as CDM – Solar axions Solar axions Solar axions Solar axions Previous helioscopes & CAST Previous helioscopes & CAST IAXO Conceptual Design IAXO Conceptual Design p p g g – Magnet Magnet – Optics Optics – Detectors Detectors I AXO Letter of I ntent : CERN-SPSC- IAXO physics potential IAXO physics potential 2013-022 Status of project. Next steps Status of project. Next steps 90 signatures / 38 institutions I AXO Conceptual Design : JINST 9 I AXO Conceptual Design : JINST 9 Conclusions Conclusions Conclusions Conclusions (2014) T05002 (arXiv:1401.3233) 2 Off-the-beaten-track DM, Igor G. Irastorza / Universidad de Trieste, Apr2015 Zaragoza
Why axions? Why axions? Strong CP problem: why strong interactions seem not to violate CP? – CP violating term in QCD is not forbidden But neutron – CP violating term in QCD is not forbidden. But neutron electric dipole moment not observed Natural answer if Peccei-Quinn mechanism exists New U(1) global symmetry spontaneously broken – N U(1) l b l t t l b k – Proposed in 1977 As a result, new pseudoscalar, neutral A lt d l t l and very light particle is predicted, the axion (Weinberg, Wilczek) PRIMAKOFF I t couples to the photon in every model I t l t th h t i d l EFFECT Off Off- -the the- -beaten beaten- -track DM, track DM, Igor G. Igor G. Irastorza Irastorza / Universidad de / Universidad de Trieste, Apr2015 Trieste, Apr2015 Zaragoza Zaragoza 3 3
Beyond Beyond Beyond axions Beyond axions axions axions Minicharged c a ged Hidden photons Hidden photons AXI ONS AXI ONS ALPS Chamaleons particles / paraphotons WI SP WI SPs (Weakly interacting Sub-eV Particle) (W kl i t ti S b V P ti l ) Diverse Diverse theory Diverse Diverse theory theory motivation theory motivation motivation motivation – Higher scale Higher scale symm symm. . breaking breaking – String String theory theory – DM / DE DM / DE candidates DM / DE DM / DE candidates candidates candidates – Astrophysical hints Astrophysical hints Generic Generic Axion Axion- -like like particles particles space (ALPs ALPs) ) parameter parameter space Off-the-beaten-track DM, Igor G. Irastorza / Universidad de 4 Trieste, Apr2015 Zaragoza
Non thermal cosmological axions Non thermal cosmological axions Non thermal cosmological axions Non thermal cosmological axions Axion realignment Axion realignment When T When T ~ T QCD T <a phys > 0 As the Universe cools down below T QCD , space is filled with low energy axion field fl fluctuations. Their density depends on the initial value of < a phys > ( misalignment angle ) < a > (“ misalignment angle”) But also… topological defects But inflation may “wipe out” topological defects defects… Did inflation happen before or Did inflation happen before or after the creation of defects (PQ transition) ? pre-inflation or post-inflation scenarios scenarios Off-the-beaten-track DM, Igor G. Irastorza / Universidad de 5 Trieste, Apr2015 Zaragoza
Axions as Dark Matter? Axions as Dark Matter? Axions as Dark Matter? Axions as Dark Matter? Axions Axions are produced are produced in the early Universe by a number of in the early Universe by a number of processes: processes: – Axion Axion realignment realignment NON NON NON-RELATI VI STI C NON RELATI VI STI C RELATI VI STI C RELATI VI STI C – Decay of Decay of axion Decay of Decay of axion axion strings axion strings strings strings (COLD) AXI ONS (COLD) AXI ONS – Decay of Decay of axion axion walls walls Axion mass giving the right CDM density? Depends on cosmological Axion mass giving the right CDM density? Depends on cosmological assumptions: assumptions: assumptions: assumptions: 5 – 10 3 eV Post Post- -inflation scenario inflation scenario (“classical window”) (“classical window”) ~ 10 10 -5 10 -3 eV Pre Pre- -inflation scenario inflation scenario (“anthropic window”) ~ lower masses possible (“anthropic window”) ~ lower masses possible Higher masses subdominant CDM / non Higher masses subdominant CDM / non- -standard scenarios standard scenarios RELATI VI STI C RELATI VI STI C – Thermal production Thermal production (HOT) AXI ONS (HOT) AXI ONS ( ( ) ) Axion masses Axion masses ma ma > ~ 0.9 > ~ 0.9 eV eV gives densities too much in excess to be gives densities too much in excess to be compatible with latest CMB compatible with latest CMB data data Hannestad et al, JCAP 08 (2010) 001 (arXiv:1004.0695) Off-the-beaten-track DM, Igor G. Irastorza / Universidad de 6 Trieste, Apr2015 Zaragoza
Astrophysical Astrophysical Astrophysical hints Astrophysical hints hints for hints for for axions(?) for axions(?) axions(?) axions(?) Neutron star Red White CAS A CAS A Gi Giants t dwarfs However, diverse evidence of G Gama ray telescopes l anomalous cooling has been like MAGIC or HESS observed in a number of stars… observe HE photons f from very distant di t t C Complex situation, but generally l it ti b t ll sources… compatible with QCD axions with masses at the 10 meV scale… ALP: Off-the-beaten-track DM, Igor G. Irastorza / Universidad de 7 Trieste, Apr2015 Zaragoza
Axion Axion motivation Axion Axion motivation motivation in a motivation in a in a nutshell in a nutshell nutshell nutshell Most compelling solution to the Strong CP problem of the SM Axion-like particles (ALPs) predicted by many extensions of the SM (e g string theory) SM (e.g. string theory) Axions, like WIMPs, may solve the DM problem for free . (i.e. not ad hoc solution to DM) Astrophysical hints Astrophysical hints for axion/ALPs? for axion/ALPs? – Transparency of the Universe to UHE gammas Transparency of the Universe to UHE gammas White dwarfs anomalous cooling point to few White dwarfs anomalous cooling point to few – White dwarfs anomalous cooling White dwarfs anomalous cooling point to few meV point to few meV meV axions meV axions axions axions Relevant axion/ALP parameter space at reach of current and near-future experiments f i Still too little experimental effort devoted to axions when compared e.g. to WIMPs… (not justified…) e.g. to WIMPs… (not justified…) Off-the-beaten-track DM, Igor G. Irastorza / Universidad de 8 Trieste, Apr2015 Zaragoza
Detecting Detecting axions Detecting axions Detecting axions axions Relic Relic Axions Axions – Axions Axions that are part of galactic dark matter halo: that are part of galactic dark matter halo: Axion Axion Haloscopes Haloscopes ADMX in US Solar Solar Axions Axions – Emitted by the solar core. Emitted by the solar core. Crystal detectors C Crystal detectors C t l d t t l d t t t CAST @ CERN Axion Helioscopes Axion Helioscopes I AXO Axions Axions in the lab in the lab “Light shinning through wall” experiments “Light shinning through wall” experiments Vacuum Vacuum birrefringence Vacuum birrefringence Vacuum birrefringence experiments birrefringence experiments experiments experiments ALPS-I I @ DESY OSQAR @ CERN Off-the-beaten-track DM, Igor G. Irastorza / Universidad de 9 Trieste, Apr2015 Zaragoza
Solar Axions Solar Axions Solar Axions Solar Axions S l Solar axions produced by photon- Solar axions produced by photon S l i i d d d b d b h h -to to- - axion conversion of the solar plasma axion conversion of the solar plasma photons in the solar core photons in the solar core Solar axion flux [ van Bibber PRD 39 (89)] [ CAST JCAP 04(2007)010] Solar physics + Primakoff effect Primakoff effect Only one unknown parameter g a Igor G. Irastorza / Universidad de Igor G. Irastorza / Universidad de Off Off- -the the- -beaten beaten- -track DM, track DM, Zaragoza Zaragoza Trieste, Apr2015 Trieste, Apr2015 10 10
Solar Axions Solar Axions Solar Axions Solar Axions S l Solar axions produced by photon- Solar axions produced by photon S l i i d d d b d b h h -to to- - axion conversion of the solar plasma axion conversion of the solar plasma photons in the solar core photons in the solar core “ABC” Solar axion flux [ J Redondo JCAP 1312 008] If the axion couples with the electron (g ae ) (g ae ) (non hadronic axion) Igor G. Irastorza / Universidad de Igor G. Irastorza / Universidad de Off Off- -the the- -beaten beaten- -track DM, track DM, Zaragoza Zaragoza Trieste, Apr2015 Trieste, Apr2015 11 11
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