Physics beyond the standard model through atoms and molecules

AMO physics meets fundamental physics

In our group, we study the possibility of finding new physics beyond the standard model through atomic and molecular systems.  In particular, we exploit the capability of controlling internal degrees of freedom in molecules to propose novel detectors for the search of light dark matter. In the same vein, we employ the remarkable precision of spectroscopy of atoms and molecules to constrain existing boundaries on different theoretical models regarding new physics.

Molecules and atoms as dark matter detectors

Observations from radial velocity curves in galaxies, galactic velocities in clusters of galaxies and the temperature anisotropies of the cosmic microwave background (CMB) point towards the existence of dark matter. Thererby, dark matter affects the dynamics of the universe to all the scales: from the galaxy scale to the cosmological one. In particular, the CMB measurement established that around 24% fo the energy budget of the universe is in the form of dark matter, whereas only 4.6% is regular matter. The astrophysical observations show that dark matter feels the gravitational force, but they do not reveal any physics regarding the particle nature of dark matter. Therefore, experiments based on interactions beyond the gravitational force are needed to elucidate the ultimate particle dark matter nature

In our group, we study atomic and molecular systems that may be potential candidates to detect dark matter with mass below the proton mass. This is possible thanks to the energy scale associated with the different internal degrees of freedom of the molecules. In particular, vibrational degrees of freedom in diatomic molecules shows an energy scale of ~0.5 eV. Therefore, assuming a typical dark matter speed of 600 km/s, excitation of a single vibrational quantum in molecules will correlate with dark matter masses below 100 MeV. Indeed, this sensitivity to low dark matter particle masses is hardly achievable by accelerator-based experiments. Therefore, our research is complementary to the ongoing research in the high energy physics community. 

High precision spectroscopy to constrain the existence of new physics

The standard model of particle physics is the most complete theory for the fundamental forces of nature except for gravity. However, it does not answer questions like: what is dark matter? or what is the origin of the neutrino masses? Thus, new theoretical models need to be developed and tested, which are known as physics beyond the standard model. As an example of physics beyond the standard model, we present the typical pair annihilation into two photons, although in this case, one of the photons is dark, has mass, and decays into a pair of dark matter particle-antiparticle.

The spectra of atoms and molecules, ultimately, are the consequence of the interaction between hadrons and leptons. In our group, we study how atomic and molecular spectroscopy can elucidate the fingerprints of physics beyond the standard model. In particular, one uses the precision on the measurements to put constraints on different physics models beyond the standard model. Among the different candidates, we like to use exotic atoms like positronium (Ps) or muonium (pµ-).


L. Gurung, T. J. Babij, J. Pérez-Ríos, S. D. Hogan, and D. B. Cassidy
Observation of asymmetric line shapes in precision microwave spectroscopy of the positronium 23S1→ 23PJ(J=1,2) fine-structure intervals
Phys. Rev. A 103, 042805
Rouven Essig, Jesús Pérez-Ríos, Harikrishnan Ramani, and Oren Slone
Direct detection of nuclear scattering of sub-Gev dark matter using molecular excitations
Phys. Rev. Research 1, 033105
Claudia Frugiuele, Jesús Pérez Ríos and Clara Peset
Current and future perspectives of positronium and muonium spectroscopy as dark sectors probe
Phys. Rev. D 100, 015010
Jesús Pérez Ríos and Sherwin T. Love
Searching for light dark matter through Positronium decay
Eur. J. Phys. D 72, 44
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