Measurements of the proton quenching effect in various organic liquid scintillators

Understanding the quenching effect for protons in organic liquid scintillators is important for both signal and background detection in present and future neutrino experiments, like Double Chooz, Borexino, LENA and JUNO. This effect defines the energy scale for proton recoil events in the scintillator, which is of particular importance for the detection of neutrinos from a galactic core collapse supernova by elastic ν-p-scattering. A time-of-flight based experiment has been established at the Maier-Leibnitz-Laboratorium in Garching. Using a pulsed ¹¹B-beam and a fixed H₂-target, monoenergetic neutrons with different energies between ∝4.7 and ∝11.2 MeV were produced to induce proton recoils in the scintillator samples. To quantify the quenching effect for protons the semi-empiric Birks quenching model was utilized. The final results on the Birks quenching factors kB, obtained from the performed measurements for various scintillator samples, including the Borexino and Double Chooz scintillators and different LAB-based mixtures, are presented.