Strangelets: who is looking and how?

Abstract

Abstract.It has been over 30 years since the first suggestion that the true ground state of cold hadronic matter might be not nuclear matter but rather strange quark matter (SQM). Ever since, searches for stable SQM have been proceeding in various forms and have observed a handful of interesting events but have neither been able to find compelling evidence for stable strangelets nor to rule out their existence. I will survey the current status and near future of such searches with particular emphasis on the idea of SQM from strange star collisions as part of the cosmic ray flux.Strange Quark Matter (SQM) is a proposed state of hadronic matter made up of roughly one-third each of up, down, and strange quarks in a single hadronic bag that can be as small as baryon number A = 2 or as large as a star. It was suggested some 30 years ago that SQM (of which a small chunk is called a "strangelet") might in fact be the true ground state of hadronic matter [1,2]. Whether this is true is still an open question today.The idea that Quark Matter made of only up and down quarks is stable can be dismissed immediately by the observation that normal nuclear matter doesn't decay into it. However, in the case of SQM such a decay would require several simultaneous weak interactions, making it prohibitively unlikely. The stability of SQM cannot yet be determined from first principles within QCD, but has been addressed in various phenomenological models. The most commonly used of these is the MIT Bag Model [3,4] which also has been extended to include the effects of colour superconducting states [5,6]. The results of such calculations are inconclusive, but for a large part of the "reasonable" parameter space in these models, SQM is in fact absolutely stable for baryon number greater than some minimum value (smaller strangelets are disfavored due to curvature energy). This minimum, depending on parameter choices, is generally larger than 50 and smaller than 1000 although shell effects which are important for A 100 may cause islands of stability at smaller A values. The key point is that SQM stability is a question that must be settled experimentally or observationally.If it turns out that SQM is stable, the implications would be potentially tremendous not only for the resultant direct and indirect understanding of the strong interaction but also for practical applications ranging from new materials (effectively, nuclear charges up to Z ≈ 1000 would become possible) to potential as a clean energy source [7].

Charges on strange quark nuggets in space

“…Is the game worth the candle? Finch says in [11] "If it turns out that SQM is stable, the impli-cations would be potentially tremendous not only for the resultant direct and indirect understanding of the strong interactions but also for the practical applications ranging from new materials..." In brief, the answer to "are they there?" seems to be that it's a long shot, but to some worth trying.…”

Mass Ejection by Strange Star Mergers and Observational Implications

“…Also indirectly, the observation of compact stars can help to decide on the SMH especially by pinning down the mass-radius relation [3,4,5]. For a review on additional SQM searches see [4,18].…”

On muon bundles from the Universe

“…Therefore, it is reasonable to expect that it exists in some form in the Universe and can be detected. This supposition resulted in a number of searches for strange stars and quark stars, in which such a form of matter would be dominant and which could therefore be a possible source of strangelets penetrating outer space [22][23][24][25][26][27][28][29]. The experimental data mentioned above lead to a flux of strangelets which follows the A −7.5 behaviour, which in turn coincides with the behaviour of the abundance of 1 Nev…”