A new kaonic helium measurement in gas by SIDDHARTINO at the DA{\Phi}NE collider

The SIDDHARTINO experiment at the DA{\Phi}NE Collider of INFN-LNF, the pilot run for the SIDDHARTA-2 experiment which aims to perform the measurement of kaonic deuterium transitions to the fundamental level, has successfully been concluded. The paper reports the main results of this run, including the optimization of various components of the apparatus, among which the degrader needed to maximize the fraction of kaons stopped inside the target, through measurements of kaonic helium transitions to the 2p level. The obtained shift and width values are {\epsilon}_2p = E_exp-E_e.m = 0.2 {\pm} 2.5(stat) {\pm} 2(syst) eV and {\Gamma}_2p = 8 {\pm} 10 eV (stat), respectively. This new measurement of the shift, in particular, represents the most precise one for a gaseous target and is expected to contribute to a better understanding of the kaon-nuclei interaction at low energy.