Many indirect evidences from astronomical and cosmological observation indicate that dark matter (DM) represents about 85% of the mass of the universe, however its microscopic nature is still unknown. A well motivated hypothesis is that dark matter is made of weakly interacting massive particles (WIMPs).
The CYGNO detector is a gaseous TPC at atmospheric pressure with the aim of demonstrate that this technology is effective for the identification of nuclear recoils down to the O(keV) energy, potentially probing low mass DM and introducing sensitivity to directionality. To be sensitive to the rare DM interactions, ultra radio-pure material have to be employed in the detector construction, and high rejection of background have to be implemented.
A complete simulation of the radioactivity from the setup materials and from the environment is crucial in order to optimize the detector and the shielding design. The simulation is also an important tool to understand and characterize the residual background in the data.
This project has the goal to develop a simulation of the total background budget in order to finalize the setup design for the Technical Design Report of CYGNO. The second phase consists in a full simulation that includes the digitization of the optical readout and produce a Monte Carlo output format identical to real data. This will allow to study in detail the efficiency of particle identification and background rejection, and to optimize the reconstruction technique with pseudo-data with the same format of real data. An active participation to the installation and commissoning of the CYGNO prototype at LNGS in 2020 is also forseen as part of this project.
Large detectors based on dual phase Xe and Ar TPCs are quickly approaching to the so called "neutrino floor", i.e. the point when neutrinos from the Sun, cosmic rays and supernovae will represent an irreducible background for the DM search.
The sensitivity to lower WIMP masses, on the other hand, is limited by the threshold of nuclear recoil detection and therefore the low mass region is still largely unexplored.
The future of DM research, both in the high mass region and in the low mass, is limited by the present technology, because the simple scaling of the current experiments to higher masses and exposures will not be sufficient to extend their physics reach.
To overcome this bound, it is necessary to explore new techniques and measure new observables to distinguish effectively signal from background at low energy.
Directionality is a promising observable, because the expected dark matter direction relative to an Earth-based target is always different from the neutrinos' direction during the year.
A gaseous TPCs at atmospheric pressure and low density, like the one proposed by CYGNO collaboration, will be able to reconstruct the tracks of nuclear recoils down to the keV recoil energy and infer the arrival direction of the invisible particle.
The CYGNO detector, with only 1m^3 of gas and 1 year of exposure, will reach a sensitivity to WIMP-nucleon SI interaction down to ~10^-40 cm^2 in the region of 1-10 GeV DM mass. In the PHASE-2, with 30 m^3 and 3 years of exposure, the sensitivity will go down to 10^-43 cm^2.
CYGNO will also put constraints on SD WIMP-nucleon interactions with a limit of ~10^-40 cm^2 in 1 year and 1 m^3 of active gas, reaching 10^-42 cm^2 in 3 years with 30 m^3.
In both SI and SD, CYGNO with 1 m^3 and year exposure will put more stringent limits than the current best exclusion in the low mass DM region [1,2].
[1] A.H. Abdelhameed, et al., arXiv:1904.00498 (2019)
[2] C. Amole et al., Phys. Rev. Lett. 118, 251301