Shi-lun Guo

Bio: Shi-lun Guo is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Electron capture & Ion. The author has an hindex of 5, co-authored 6 publications receiving 111 citations.

Search for Grand-Unified-Theory Magnetic Monopoles at a Flux Level below the Parker Limit

Abstract: We report the results of the first direct search for grand-unified-theory magnetic monopoles with adequate sensitivity to detect a flux as small as the Parker flux limit. If stable monopole-nucleus bound states exist then the observed absence of monopole tracks in our 4.6\ifmmode\times\else\texttimes\fi{}${10}^{8}$-yr-old mica detector places an upper limit of ${10}^{\ensuremath{-}17}$ to ${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ ${\mathrm{sr}}^{\ensuremath{-}1}$ ${\mathrm{s}}^{\ensuremath{-}1}$ on the flux of grand-unified-theory monopoles having velocity $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}c$ to $1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}c$.

Charge resolution of plastic track detectors used to identify relativistic nuclei

Abstract: We present measurements of charge resolution in the plastic track detectors CR39(DOP) and Tuffak polycarbonate over the region 10≤ Z β ≤105 , determined from plastic stacks exposed to projectile fragments of 1.29 GeV u 139La, 1.45 GeV u 84Kr, and 1.70 GeV u 56Fe produced by nuclear interactions within the stacks, and to 0.96 GeV u 238U and 1.0 GeV u 197Au ions. The charge resolution obtained is shown to be comparable to the irreducible limit set by fluctuations in energy loss and is consistent with that expected of a track-formation model based on the effects of both K-shell ionization and restricted energy loss.

Nuclear Tracks in Solids (Principles and Applications)

Abstract: (1976). Nuclear Tracks in Solids (Principles and Applications) Nuclear Technology: Vol. 30, No. 1, pp. 91-92.

Nuclearites—a novel form of cosmic radiation

Abstract: E. Witten (personal communication) has raised the intriguing possibility that nuclear matter consisting of aggregates of up, down and strange quarks in roughly equal proportions may be less massive than ordinary nuclear matter of the same quark number consisting of protons and neutrons (triplets of non-strange quarks). These nuggets of strange quark matter may be stable for almost any baryon number (A), including values intermediate between those of ordinary nuclei (A≲263) and neutron stars (A ∼ 1057). We use the term ‘nuclearite’ to describe such strange quark nuggets in collision with Earth and suggest experiments to detect these encounters.

Theoretical and experimental status of magnetic monopoles

Abstract: The Tevatron has inspired new interest in the subject of magnetic monopoles. First there was the 1998 D0 limit on the virtual production of monopoles, based on the theory of Ginzburg and collaborators. In 2000 and 2004 results from an experiment (Fermilab E882) searching for real magnetically charged particles bound to elements from the CDF and D0 detectors were reported. The strongest direct experimental limits, from the CDF collaboration, have been reported in 2005. Less strong, but complementary, limits from the H1 collaboration at HERA were reported in the same year. Interpretation of these experiments also require new developments in theory. Earlier experimental and observational constraints on point-like (Dirac) and non-Abelian monopoles were given from the 1970s through the 1990s, with occasional short-lived positive evidence for such exotic particles reported. The status of the experimental limits on monopole masses will be reported, as well as the limitation of the theory of magnetic charge at present.

Macro dark matter

Abstract: Dark matter is a vital component of the current best model of our Universe, Λcold dark matter. There are leading candidates for what the dark matter could be (e.g. weakly interacting massive particles, or axions), but no compelling observational or experimental evidence exists to support these particular candidates, nor any beyond-the-Standard-Model physics that might produce such candidates. This suggests that other dark matter candidates, including ones that might arise in the Standard Model, should receive increased attention. Here we consider a general class of dark matter candidates with characteristic masses and interaction cross-sections characterized in units of grams and cm^2, respectively – we therefore dub these macroscopic objects as Macros. Such dark matter candidates could potentially be assembled out of Standard Model particles (quarks and leptons) in the early Universe. A combination of Earth-based, astrophysical, and cosmological observations constrain a portion of the Macro parameter space. A large region of parameter space remains, most notably for nuclear-dense objects with masses in the range 55–10^17 g and 2 × 10^20–4 × 10^24 g, although the lower mass window is closed for Macros that destabilize ordinary matter.