Signatures of hidden particles in strong external fields
Final Report Abstract
Optical searches assisted by the field of strong laser pulses might allow for exploring a variety of not yet detected dark matter candidates such as paraphotons, axionlike particles and minicharged particles. These hypothetical degrees of freedom arise as natural consequence in certain extensions of the Standard Model incorporating hidden sectors. Throughout this investigation, we have paid special attention to the capabilities that both long laser pulses of moderate intensity and short pulses of ultrahigh intensity offer for the exploration of the low-energy frontier of particle physics. We have pointed out that, when the former are used as backgrounds driving a polarimetric search of the yet unobserved vacuum birefringence, their long durations may compensate for their small intensities. The combinination of this feature with the fact that they are also characterized by a well-defined frequency manifests in the realization of minicharged particle creation thresholds, in which the projected sensitivities can be higher by one order of magnitude than those achieved in experiments driven by dipole magnets, for minicharges with mass around 1 eV. Besides, we have noted that – depending upon the external parameters and the internal spin value of the minicharges – the photon-paraphoton oscillations in such long laser pulses could be either facilitated or suppressed. This intrinsic property might manifest through the probe photon beam and can be exploited to discern the quantum statistics of these particle candidates. A special emphasis has been laid on a plausible change in the ellipticity sign that the probe photon may undergo, due to the minicharged particle’s nature [fermionic or bosonic]. Particular attention has been paid to the impact of both the wave profile and the polarization of the strong laser field onto the projected bounds found for minicharge carriers and axionlike particles. Our analysis shows that, for axionlike particles, the upper limits resulting from the ellipticity are relatively insensitive to this change, whereas those arising from the rotation of the polarization plane turn out to be more dependent on the field shape. Besides, our results indicate that a planned experiment looking for vacuum birefringence – to be managed by the HiBEF consortium utilizing an optical petawatt and an x-ray free-electron laser – could improve the existing laboratory bounds on axionlike particles by three orders of magnitude for axion masses around 100 eV. We have even found that various experimental setups based on contemporary laser facilities and instrumentation might lead to new exclusion bounds on the parameter space of these dark matter candidates. Finally, it was revealed that, in a constant and homogeneous magnetic background much stronger than a specific critical scale, quantum vacuum fluctuations of axionlike fields might modify the polarization properties of the vacuum substantially. Considering the framework of axion-electrodynamics, the corresponding self-energy operator for the electromagnetic field was determined, and utilized for establishing the modified Coulomb potential of a static pointlike charge. The resulting potential is shortranged in the direction perpendicular to the magnetic field while it follows approximately the behavior of Coulomb’s law along it. This anisotropic screening has been exploited to assess the ground-state energy of a nonrelativistic electron in a hydrogenlike atom placed in such a strong magnetic field. The limiting value for the corresponding ground-state energy turns out to be comparable with the outcome obtained in QED, when the respective vacuum polarization effect is taken into account and the magnetic field grows unlimitedly.
Publications
- Light dark matter candidates in intense laser pulses I: paraphotons and fermionic minicharged particles, JHEP 1506, 177 (2015)
S. Villalba-Chávez and C. Müller
(See online at https://doi.org/10.1007/JHEP06(2015)177) - Light dark matter candidates in intense laser pulses II: the relevance of the spin degrees of freedom, JHEP 1602, 027 (2016)
S. Villalba-Chávez and C. Müller
(See online at https://doi.org/10.1007/JHEP02(2016)027) - Minicharged particles search by strong laser pulse-induced vacuum polarization effects. Phys. Lett. B 763, 445 (2016)
S. Villalba-Chávez, S. Meuren and C. Müller
(See online at https://doi.org/10.1016/j.physletb.2016.10.068) - Polarization-operator approach to optical signatures of axion-like particles in strong laser pulses. Phys. Lett. B 769, 233 (2017)
S. Villalba-Chávez, T. Podszus and C. Müller
(See online at https://doi.org/10.1016/j.physletb.2017.03.043)
