Abstract
We study the effect of a dibaryon, S, in the mass range 1860 MeV < m_S < 2054 MeV, which is heavy enough not to disturb the stability of nuclei and light enough to possibly be cosmologically metastable. Such a deeply bound state can act as a baryon sink in regions of high baryon density and temperature. We find that the ambient conditions encountered inside a newly born neutron star are likely to sustain a sufficient population of hyperons to ensure that a population of S dibaryons can equilibrate in less than a few seconds. This would be catastrophic for the stability of neutron stars and the observation of neutrino emission from the proto-neutron star of Supernova 1987A over ~ O(10)s. A deeply bound dibaryon is therefore incompatible with the observed supernova explosion, unless the cross section for S production is severely suppressed.
Highlights
The possibility that six light quarks form the QCD bound state uuddss, known as the H dibaryon with binding energy BH ≡ 2mΛ − mH ≳ 0, has been considered for several decades [1]
Given n∞Λ, Eq (2c) dictates that the S abundance will rise linearly as long as fission is unimportant, nSðtÞ ≃ n SðtÞ≡ ðn∞Λ Þ2hσΛΛ→Sγvit. This is true until an Oð1Þ fraction of baryons are in S dibaryons, which happens at a time tS defined by 2nSðtSÞ 1⁄4 nNðtSÞ
We have shown that the hot interior of a proto-neutron star provides a valuable laboratory for probing the nature of the proposed deeply bound S dibaryon
Summary
The possibility that six light quarks form the QCD bound state uuddss, known as the H dibaryon with binding energy BH ≡ 2mΛ − mH ≳ 0, has been considered for several decades [1]. We consider an S that is light enough to be metastable but massive enough that it is not exothermically produced as a fusion product of two nucleons. This gives the constrained mass range 1860 < mS < mΛ þ mp þ me≃ 2054 MeV, which in turn implies. Due to its electric neutrality and its (meta)stability, such a particle would be a candidate for the dark matter of the Universe [11] Such a state would avoid detection in underground direct detection experiments due to the overburden of Earth, and may inefficiently deposit energy in the only relevant high-altitude direct detection search [19]. We conclude that observations are in grave tension with the hypothesis of a deeply bound S unless the S production cross section is highly suppressed
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