Speaker
Ms
Jhilik Majumdar
(PhD student in UniHH)
Description
Well-motivated extensions of the standard model predict ultra-light and
fundamental pseudo-scalar particles (e.g., axions or axion-like particles: ALPs). Similarly to the Primakoff-effect for axions, ALPs can mix with photons and consequently
be searched for in laboratory experiments and with astrophysical observations. Here,
we search for energy-dependent modulations of high-energy gamma-ray spectra which
are the evidential signatures of photon-ALPs mixing. To verify this, we analyze the data
recorded with the Fermi-LAT from Galactic pulsars selected to have a line of sight crossing
spiral arms at a large pitch angle. For the six selected Galactic pulsars, the energy spectrum is well described by a smooth model spectrum (a power-law with a sub-exponential
cut-off) while a common fit of the ALPs parameters improves the goodness of fit in comparison to a smooth model spectrum with a significance of 4.6 σ. We determine the most-likely values for ALPs mass and photon-ALPs coupling constant which are by a factor of ≈ 3 larger than the
current best limit on solar ALPs generation obtained with the CAST helioscope, although
known modifications of the photon-ALP mixing in the high density solar environment
could provide a plausible explanation for the apparent tension between the helioscope
bound and the current indication for photon-ALPs mixing.
Primary author
Ms
Jhilik Majumdar
(PhD student in UniHH)
Co-authors
Prof.
Dieter Horns
(University of Hamburg)
Dr
Francesca Calore
(LAPTh, CNRS)
