Improved limit on invisible decays of positronium

Abstract

The results of a new search for positronium decays into invisible final states are reported. Convincing detection of this decay mode would be a strong evidence for new physics beyond the Standard Model (SM): for example the existence of extra-dimensions, of milli-charged particles, of new light gauge bosons or of mirror particles. Mirror matter could be a relevant dark matter candidate.In this paper the setup and the results of a new experiment are presented. In a collected sample of about (6.31 ± 0.28) × 10 6 orthopositronium decays, no evidence for invisible decays in an energy window [0,80] keV was found and an upper limit on the branching ratio of orthopositronium o − P s → invisible could be set:Our results provide a limit on the photon mirror-photon mixing strength ǫ ≤ 1.55 × 10 −7 (90% C.L.) and rule out particles lighter than the electron mass with a fraction Q x ≤ 3.4 × 10 −5 of the electron charge. Furthermore, upper limits on the branching ratios for the decay of parapositronium Br(p − P s → invisible) ≤ 4.3 × 10 −7 (90% C.L.) and the direct annihilation Br(e + e − → invisible) ≤ 2.1 × 10 −8 (90% C.L.) could be set.

Experimental limits on neutron disappearance into another braneworld

“…[16], we get g < 3 × 10 10 m −1 from the millicharge constraint ε < 4.1 × 10 −5 [38]. Even with more recent and stringent constraints [13,39], we get g < 9 × 10 7 m −1 from ε < 3 × 10 −10 (see Berezhiani and Lepidi in Ref. [39]).…”

“…on a brane) values of the magnetic vector potentials. H cm leads to a phenomenology which shares some similarities with the mirror matter paradigm [6,[11][12][13] or other approaches involving some hidden or dark matter sectors [14]. Nevertheless the present approach differs in several ways:…”

“…Testing the existence of branes or extra dimensions is therefore becoming a fundamental challenge. Such evidences are expected to be obtained through high energy collisions [2][3][4], but it has been also demonstrated that some detectable effects could also be observed at low energy [2,3,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . This is the topic of the present paper.…”

“…Such an experimental approach can be accepted with confidence. Indeed, the lowest considered frequencies of the swapping probability are about 10 13 Hz in relation to η (see section 2). This is far to the highest expected collision rates, and then Eqs.…”

“…Other works also considered that fluctuations of our home-brane could yield small bubbles branes, which carry chargeless matter particles (such as neutrons for instance) into the bulk [3]. In another context, other approaches consider some coupling between certain particles of the standard model and some hidden or dark sectors [6,[8][9][10][11][12][13][14]. It is sometimes suspected that such hidden sectors could live in other branes.…”