https://doi.org/10.1140/epja/i2013-13064-1
Regular Article - Experimental Physics
New search for correlated e+e- pairs in the
decay of 241Am
19894
INFN, Sezione Roma “Tor Vergata”, I-00133, Rome, Italy
29894
Dipartimento di Fisica, Università di Roma “Tor Vergata”, I-00133, Rome, Italy
39894
INFN, Sezione Roma, I-00185, Rome, Italy
49894
Dipartimento di Fisica, Università di Roma “La Sapienza”, I-00185, Rome, Italy
59894
INFN, Laboratori Nazionali del Gran Sasso, I-67100, Assergi (AQ), Italy
69894
IHEP, Chinese Academy, P.O. Box 918/3, 100039, Beijing, China
79894
Dipartimento di Ingegneria Civile e Ingegneria Informatica, Università di Roma “Tor Vergata”, Rome, Italy
89894
Institute for Nuclear Research, MSP 03680, Kyiv, Ukraine
99894
University of Jing Gangshan, Jiangxi, China
* e-mail: rita.bernabei@roma2.infn.it
Received:
15
February
2013
Accepted:
3
May
2013
Published online:
29
May
2013
A new search for production of correlated pairs in the
decay of 241Am has been carried out deep underground at the Gran Sasso National Laboratory of the INFN by using pairs of NaI(Tl) detectors of the DAMA/LIBRA set-up. The experimental data show an excess of double coincidences of events with energy around 511keV in faced pairs of detectors, which are not explained by known side reactions. This measured excess gives a relative activity
for the Internal Pair Production (IPP) with respect to the alpha decay of 241Am; this value is of the same order of magnitude as previous determinations. In a conservative approach the upper limit
(90% C.L.) can be derived. It is worth noting that this is the first result on IPP obtained in an underground experiment, and that the
value obtained in the present work is independent of the live-time estimate.
© SIF, Springer-Verlag Berlin Heidelberg, 2013