The dark matter interpretation of the DAMA modulation signal depends on the NaI(Tl) scintillation efficiency of nuclear recoils. Previous measurements for Na recoils have large discrepancies, especially in the DAMA/LIBRA modulation energy region. We report a quenching effect measurement of Na recoils in NaI(Tl) from 3 to 52 keV nr , covering the whole DAMA/LIBRA energy region for dark matter-Na scattering interpretations. By using a low-energy, pulsed neutron beam, a double time-of-flight technique, and pulse-shape discrimination methods, we obtained the most accurate measurement of this kind for NaI(Tl) to date. The results differ significantly from the DAMA reported values at low energies but fall between the other previous measurements. We present the implications of the new quenching results for the dark matter interpretation of the DAMA modulation signal.
We have measured the ionization efficiency of silicon nuclear recoils with kinetic energy between 1.8 and 20 keV. We bombarded a silicon-drift diode with a neutron beam to perform an elastic-scattering experiment. A broad-energy neutron spectrum was used and the nuclear recoil energy was reconstructed using a measurement of the time of flight and scattering angle of the scattered neutron. The overall trend of the results of this work is well described by the theory of Lindhard et al. above 4 keV of recoil energy. Below this energy, the presented data shows a deviation from the model. The data indicates a faster drop than the theory prediction at low energies.
I IntroductionThe development of technologies for detecting low energy nuclear recoils has been a very active field in recent years, mainly driven by dark matter searches and coherent neutrino nucleus scattering (CENNS) experiments. When a nucleus recoils in a semiconductor detector, it loses its kinetic energy through two mechanisms: the generation of free charge carriers by ionization and the production of phonons by collisions with the lattice atoms. The partition of energy is quantified by the ionization efficiency, ε, defined as the ratio of the energy lost via ionization, E i , to the kinetic energy of the nuclear recoil, E N R . In the literature, E i is usually denoted by eV
The 90 Zr(α,γ) 94 Mo, 92 Zr(α,γ) 96 Mo, and 74 Ge(α,γ) 78 Se reaction cross sections were measured for the first time in an effort to expand the existing experimental database for (α,γ) reactions relevant for the production of the p nuclei in the universe. In particular, the 90 Zr(α,γ) 94 Mo reaction was identified by a sensitivity study for its potential impact for the γ-process mass flow in the region of the light p nuclei. The measurements were performed for energies Eα = 9.5 − 12.0 MeV at the University of Notre Dame using the SuN detector and the γ-summing technique. The results are compared to theoretical calculations from the TALYS and NON-SMOKER nuclear reaction codes, and it is shown that the data greatly reduces the uncertainty in the cross section for the measured energies. The TALYS parameters that provide the best description of the experimental data are reported.PACS numbers 24.60. Dr, 25.40.Lw, 26.30.Ef
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