Speaker
Prof.
Attila Krasznahorkay
(Inst. of Nucl. Res. of the Hung. Acad. of Sci. (ATOMKI), Head, Division of Nuclear Physics)
Description
In a recent series of papers the intriguing possibility was explored
that the cosmic dark matter consists of new elementary particles with
masses in the MeV range, which could be searched for in nuclear
physics laboratories. Such particles are not excluded by any obvious
laboratory measurements or astrophysical arguments. There are even
some experimental indications for a light neutral boson with a mass
of around 9 MeV/c2 [1,2]. The spectrometers used for the above
studies were plastic telescopes, which are insufficient for the
required precision. We have improved the setups already and got
somewhat stronger indications, but the reliability of the results can
still be questioned because of the large systematic errors [3,4].
The signature of the new particle is the very characteristic angular
correlation of the e+e- pairs from their decay. Quantum
electrodynamics predicts that the angular correlation between the
e+e- pairs emitted in internal pair creation drops smoothly with
the separation angle. In striking contrast, when the transition takes
place by the emission of a short-lived neutral particle annihilating
into an e$^+$e$^-$ pair, the angular correlation becomes sharply
peaked at large angles. In order to search for this signature with
high confidence we need an internal pair spectrometer with much better
specifications, which was ever built for studying nuclear transitions.
We started to build a Compact Orange type Positron
Electron spectrometer (COPE) for precise studies of the e+e-
pair creation in the energy range of 10-20 MeV with large solid angle,
good energy (1\%) and angular (2 deg.) resolutions,
using strong permanent magnets. The diameter of such a spectrometer
will be about 30 cm, which is versatile and can be used at different
laboratories. With the presently available tracking detectors,
data-acquisition systems and computers we will be able to study the
differential internal pair creation process more precisely than ever
before, with a precision enaugh for confirming (or discarding with
high confidence) the existence of such light neutral particles.
References:
[1] F.W.N. de Boer and R. van Dantzig, Phys. Rev. Lett. 61,
1274 (1988).
[2] F.W.N. de Boer et al., Phy. Lett. B 388, 235. (1996);
J. Phys. G 23, L85 (1997); J. Phys. G 27 L29 (2001).
[3] A. Krasznahorkay et al., Acta Phys. Polonica B 37, 239
(2006); Nucl. Phys. News Int. 15, 36 (2005); AIP Conf. Proc. 802,
236 (2005).
[4] A. Vitez et al., Acta Phys. Polonica B 39 (2008) 483.
Primary author
Prof.
Attila Krasznahorkay
(Inst. of Nucl. Res. of the Hung. Acad. of Sci. (ATOMKI), Head, Division of Nuclear Physics)
