Publication Date:
2020-12-01
Description:
Recently, the ATOMKI experiment has reported new evidence for the excess of $$e^+e^-$$ e + e - events with a mass $$sim $$ ∼ 17 MeV in the nuclear transitions of $$^4$$ 4 He, that they previously observed in measurements with $$^8$$ 8 Be. These observations could be explained by the existence of a new vector $$X17$$ X 17 boson. So far, the search for the decay $$X17
ightarrow e^+ e^-$$ X 17 → e + e - with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining $$X17$$ X 17 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the $$X17$$ X 17 decay with the proposed method. To reach this goal an optimization of the $$X17$$ X 17 production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results [1], validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate show that the goal of the proposed search is feasible.
Print ISSN:
1434-6044
Electronic ISSN:
1434-6052
Topics:
Physics
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