International study conducted by the University of Coimbra presents new leads for detecting dark matter
The work has just been published in Physical Review X (PRX)
An international research team led by researchers from the University of Coimbra (UC) has studied a new type of scintillation emission in xenon gas, which has an impact on dark matter and neutrino detectors.
The work has just been published in Physical Review X (PRX), the prestigious journal of the American Physical Society, and has been designed and carried out by researchers Cristina Monteiro and Carlos Henriques, from the Laboratory for Instrumentation, Biomedical Engineering and Radiation Physics (LIBPhys) of the Faculty of Sciences and Technology of the University of Coimbra (FCTUC), in the scope of the international collaboration NEXT.
According to Cristina Monteiro, this study " has unequivocally revealed the existence of the emission of a type of scintillation in the xenon gas, which has so far been ignored by scientists. The scattering of electrons in neutral atoms in xenon gas originates a new type of light emission that will affect the sensitivity of detectors in dark matter research and neutrino physics".
When ionizing radiation interacts with xenon, “copious amounts of ultraviolet light are emitted at particular wavelengths—an “electroluminescence” that is leveraged in dark matter searches and neutrino detectors. But researchers were not aware of the presence of another, fainter, light emission over a broader wavelength range, from the ultraviolet to the near infrared. Therefore, scientists explained the corresponding light pulses as being due to impurities in the gas. Here, we show that these pulses are instead signals of a new kind of light emitted in xenon, caused by the scattering of electrons onto neutral atoms.”, we may read in the article summary.
Cristina Monteiro points out that with this finding "scientists now know that discovering dark matter and observing neutrinos requires more than just making the xenon pure inside of large detector systems. Researchers should also separate the light due to neutral bremsstrahlung to optimize the design of the detectors and to improve their sensitivity."
In order to get to this conclusion, the FCTUC team, which also includes PhD student Joana Teixeira, carried out the studies in a small laboratory system specifically designed for this purpose and also identified this light, called neutral bremsstrahlung, in the large detector of the NEXT international experiment, a particle detector located in an underground laboratory in Spain.
“Given the smallness of our detector, its xenon purity is very well controlled. In addition, we can precisely isolate the scintillation emission from a specific region of the detector and study this emission under very well controlled conditions, both when electroluminescence can and cannot occur. This allows us to observe and study scintillation emission other than electroluminescence. Simultaneously, we implemented a robust theoretical model for the neutral bremsstrahlung, which describes the experimental data very well and allows us to unambiguously assign the observed scintillation mechanism to neutral bremsstrahlung.”, adds Cristina Monteiro.
The scientific article is available at: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.12.021005.
English version: Diana Taborda (with excerpts from the scientific paper included)