Katsushi Arisaka, Paolo Beltrame, Chamkaur Ghag, Kevin Lung, Paul Robert Scovell
A new data analysis method based on physical observables for WIMP dark matter
searches with noble liquid Xe dual-phase TPCs is presented. Traditionally, the
nuclear recoil energy from a scatter in the liquid target has been estimated by
means of the initial prompt scintillation light (S1) produced at the
interaction vertex. The ionization charge (C2), or its secondary scintillation
(S2), is combined with the primary scintillation in Log(S2/S1) vs. S1 only as a
discrimination parameter against electron recoil background. Arguments in favor
of C2 as the more reliable nuclear recoil energy estimator than S1 are
presented. The new phase space of Log(S1/C2) vs. C2 is introduced as more
e?cient for nuclear recoil acceptance and exhibiting superior energy
resolution. This is achieved without compromising the discrimination power of
the LXe TPC, nor its 3D event reconstruction and ?ducialization capability, as
is the case for analyses that exploit only the ionization channel. Finally, the
concept of two independent energy estimators for background rejection is
presented: E2 as the primary (based on C2) and E1 as the secondary (based on
S1). Log(E1/E2) vs. E2 is shown to be the most appropriate phase space in which
to evaluate WIMP signal candidates.
View original:
http://arxiv.org/abs/1202.1924
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