2.4 Future Experiments
41
• Pair annihilation: Collider experiment at higher energies and luminosities can use
the same striking signature of a mono-photon plus missing energy to search for
the dark photon. Even though the dipole interaction is suppressed and severely
constrained in this case by the astrophysical and cosmological bounds discussed
in Sect. 2.1, it is no more suppressed than the equivalent cross sections for the
massive case. Moreover, the dipole operator scales as the center-of-mass energy
in the process and higher energies make it more and more relevant;
• Magnons: An interesting possibility is the use of magnons in ferromagnetic materials and their interaction with dark photons (QUAX proposal) [80, 81]. The estimated sensitivity is again done for axions but can be translated for massless dark
photons as in the discussion about stars above.
• Astrophysics: Gravitation waves emitted during the inspiral phase of neutron star
collapse can test the presence of other forces beside gravitation. Dipole radiation
by even small amount of charges on the stars modifies the energy emitted; the dark
photon is a prime candidate for this kind of correction [82–85].
References
1. S. Hoffmann, Paraphotons and Axions: similarities in stellar emission and detection. Phys.
Lett. B 193, 117–122 (1987). https://doi.org/10.1016/0370-2693(87)90467-9
2. G.G. Raffelt, Stars as laboratories for fundamental physics, vol. 664 (University Press, Chicago,
USA, 1996), p. 1996. http://wwwth.mpp.mpg.de/members/raffelt/mypapers/199613.pdf
3. E.D. Carlson, Limits on a new U(1) coupling. Nucl. Phys. B 286, 378–398 (1987). https://doi.
org/10.1016/0550-3213(87)90446-9
4. B.A. Dobrescu, Massless gauge bosons other than the photon. Phys. Rev. Lett. 94, 151802
(2005). https://doi.org/10.1103/PhysRevLett.94.151802. arXiv:hep-ph/0411004 [hep-ph]
5. M. Nakagawa, Y. Kohyama, N. Itoh, Axion bremsstrahlung in dense stars. Astrophys. J. 322,
291 (1987). https://doi.org/10.1086/165724
6. G.G. Raffelt, Axion bremsstrahlung in red giants. Phys. Rev. D 41, 1324–1326 (1990). https://
doi.org/10.1103/PhysRevD.41.1324
7. M.M. Miller Bertolami, B.E. Melendez, L.G. Althaus, J. Isern, Revisiting the Axion
bounds from the Galactic white dwarf luminosity function. JCAP 1410 (10), 069 (2014).
arXiv:1406.7712 [hep-ph]. https://doi.org/10.1088/1475-7516/2014/10/069
8. N. Viaux, M. Catelan, P.B. Stetson, G. Raffelt, J. Redondo, A.A.R. Valcarce, A. Weiss, Neutrino
and Axion bounds from the globular cluster M5 (NGC 5904). Phys. Rev. Lett. 111, 231301
(2013). https://doi.org/10.1103/PhysRevLett.111.231301. arXiv:1311.1669 [astro-ph.SR]
9. M. Giannotti, I. Irastorza, J. Redondo, A. Ringwald, Cool WISPs for stellar cooling excesses.
JCAP 1605(05), 057 (2016). arXiv:1512.08108 [astro-ph.HE]. https://doi.org/10.1088/14757516/2016/05/057
10. R.P. Brinkmann, M.S. Turner, Numerical rates for Nucleon-Nucleon Axion Bremsstrahlung.
Phys. Rev. D 38, 2338 (1988). https://doi.org/10.1103/PhysRevD.38.2338
11. G. Raffelt, D. Seckel, A selfconsistent approach to neutral current processes in supernova
cores. Phys. Rev. D 52, 1780–1799 (1995). arXiv:astro-ph/9312019. https://doi.org/10.1103/
PhysRevD.52.1780
12. N. Iwamoto, Axion emission from neutron stars. Phys. Rev. Lett. 53, 1198–1201 (1984). https://
doi.org/10.1103/PhysRevLett.53.1198
41
• Pair annihilation: Collider experiment at higher energies and luminosities can use
the same striking signature of a mono-photon plus missing energy to search for
the dark photon. Even though the dipole interaction is suppressed and severely
constrained in this case by the astrophysical and cosmological bounds discussed
in Sect. 2.1, it is no more suppressed than the equivalent cross sections for the
massive case. Moreover, the dipole operator scales as the center-of-mass energy
in the process and higher energies make it more and more relevant;
• Magnons: An interesting possibility is the use of magnons in ferromagnetic materials and their interaction with dark photons (QUAX proposal) [80, 81]. The estimated sensitivity is again done for axions but can be translated for massless dark
photons as in the discussion about stars above.
• Astrophysics: Gravitation waves emitted during the inspiral phase of neutron star
collapse can test the presence of other forces beside gravitation. Dipole radiation
by even small amount of charges on the stars modifies the energy emitted; the dark
photon is a prime candidate for this kind of correction [82–85].
References
1. S. Hoffmann, Paraphotons and Axions: similarities in stellar emission and detection. Phys.
Lett. B 193, 117–122 (1987). https://doi.org/10.1016/0370-2693(87)90467-9
2. G.G. Raffelt, Stars as laboratories for fundamental physics, vol. 664 (University Press, Chicago,
USA, 1996), p. 1996. http://wwwth.mpp.mpg.de/members/raffelt/mypapers/199613.pdf
3. E.D. Carlson, Limits on a new U(1) coupling. Nucl. Phys. B 286, 378–398 (1987). https://doi.
org/10.1016/0550-3213(87)90446-9
4. B.A. Dobrescu, Massless gauge bosons other than the photon. Phys. Rev. Lett. 94, 151802
(2005). https://doi.org/10.1103/PhysRevLett.94.151802. arXiv:hep-ph/0411004 [hep-ph]
5. M. Nakagawa, Y. Kohyama, N. Itoh, Axion bremsstrahlung in dense stars. Astrophys. J. 322,
291 (1987). https://doi.org/10.1086/165724
6. G.G. Raffelt, Axion bremsstrahlung in red giants. Phys. Rev. D 41, 1324–1326 (1990). https://
doi.org/10.1103/PhysRevD.41.1324
7. M.M. Miller Bertolami, B.E. Melendez, L.G. Althaus, J. Isern, Revisiting the Axion
bounds from the Galactic white dwarf luminosity function. JCAP 1410 (10), 069 (2014).
arXiv:1406.7712 [hep-ph]. https://doi.org/10.1088/1475-7516/2014/10/069
8. N. Viaux, M. Catelan, P.B. Stetson, G. Raffelt, J. Redondo, A.A.R. Valcarce, A. Weiss, Neutrino
and Axion bounds from the globular cluster M5 (NGC 5904). Phys. Rev. Lett. 111, 231301
(2013). https://doi.org/10.1103/PhysRevLett.111.231301. arXiv:1311.1669 [astro-ph.SR]
9. M. Giannotti, I. Irastorza, J. Redondo, A. Ringwald, Cool WISPs for stellar cooling excesses.
JCAP 1605(05), 057 (2016). arXiv:1512.08108 [astro-ph.HE]. https://doi.org/10.1088/14757516/2016/05/057
10. R.P. Brinkmann, M.S. Turner, Numerical rates for Nucleon-Nucleon Axion Bremsstrahlung.
Phys. Rev. D 38, 2338 (1988). https://doi.org/10.1103/PhysRevD.38.2338
11. G. Raffelt, D. Seckel, A selfconsistent approach to neutral current processes in supernova
cores. Phys. Rev. D 52, 1780–1799 (1995). arXiv:astro-ph/9312019. https://doi.org/10.1103/
PhysRevD.52.1780
12. N. Iwamoto, Axion emission from neutron stars. Phys. Rev. Lett. 53, 1198–1201 (1984). https://
doi.org/10.1103/PhysRevLett.53.1198