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New search for correlated e+e- pairs in the \( \alpha\) decay of 241Am

  • R. Bernabei
  • P. Belli
  • F. Cappella
  • V. Caracciolo
  • S. Castellano
  • R. Cerulli
  • C. J. Dai
  • A. d’Angelo
  • A. Di Marco
  • H. L. He
  • A. Incicchitti
  • M. Laubenstein
  • X. H. Ma
  • F. Montecchia
  • X. D. Sheng
  • V. I. Tretyak
  • R. G. Wang
  • Z. P. Ye
Regular Article - Experimental Physics

Abstract.

A new search for production of correlated \(e^{+}e^{-}\) pairs in the \(\alpha\) 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 \(\lambda=(4.70\pm 0.63)\times 10^{-9}\) 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 \(\lambda < 5.5\times 10^{-9}\) (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 \( \lambda\) value obtained in the present work is independent of the live-time estimate.

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Copyright information

© SIF, Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • R. Bernabei
    • 1
    • 2
  • P. Belli
    • 1
    • 2
  • F. Cappella
    • 3
    • 4
  • V. Caracciolo
    • 5
  • S. Castellano
    • 5
  • R. Cerulli
    • 5
  • C. J. Dai
    • 6
  • A. d’Angelo
    • 3
    • 4
  • A. Di Marco
    • 1
    • 2
  • H. L. He
    • 6
  • A. Incicchitti
    • 3
    • 4
  • M. Laubenstein
    • 5
  • X. H. Ma
    • 6
  • F. Montecchia
    • 1
    • 7
  • X. D. Sheng
    • 6
  • V. I. Tretyak
    • 8
  • R. G. Wang
    • 6
  • Z. P. Ye
    • 6
    • 9
  1. 1.INFN, Sezione Roma “Tor Vergata”RomeItaly
  2. 2.Dipartimento di FisicaUniversità di Roma “Tor Vergata”RomeItaly
  3. 3.INFN, Sezione RomaRomeItaly
  4. 4.Dipartimento di FisicaUniversità di Roma “La Sapienza”RomeItaly
  5. 5.INFNLaboratori Nazionali del Gran SassoAssergi (AQ)Italy
  6. 6.IHEPChinese AcademyBeijingChina
  7. 7.Dipartimento di Ingegneria Civile e Ingegneria InformaticaUniversità di Roma “Tor Vergata”RomeItaly
  8. 8.Institute for Nuclear ResearchKyivUkraine
  9. 9.University of Jing GangshanJiangxiChina

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