Ancient Mica Research Articles

Old rocks, new limits: excavated ancient mica searches for dark matter

Minerals excavated from the Earth's crust contain gigayear-long astroparticle records, which can be read out using acid etching and microscopy, providing unmatched sensitivity to high mass dark matter. A roughly millimetre size slab of 500 million year old muscovite mica, calibrated and analyzed by Snowden-Ifft et al. in 1990, revealed no signs of dark matter recoils and placed competitive limits on the nuclear interactions for sub-TeV mass dark matter. A different analysis of larger mica slabs in 1986 by Price and Salamon searched for strongly interacting monopoles. After implementing a detailed treatment of Earth's overburden, we utilize these ancient etched mica data to obtain new bounds on high mass dark matter interactions with nuclei.

Prospects for strangelet detection with large-scale cosmic ray observatories

Quark matter which contains [Formula: see text]-quarks in addition to [Formula: see text]- and [Formula: see text]- could be stable or metastable. In this case, lumps made of this strange matter, called strangelets, could occasionally hit the Earth. When travelling through the atmosphere they would behave not dissimilar to usual high-velocity meteors with only exception that, eventually, strangelets reach the surface. As these encounters are expected to be extremely rare events, very large exposure is needed for their observation. Fluorescence detectors utilized in large ultra-high energy cosmic ray observatories, such as the Pierre Auger observatory and the Telescope Array are well suited for a task of the detection of these events. The flux limits that can be obtained with the Telescope Array fluorescence detectors could be as low as 2.5 × 10−22 cm−2s−1sr−1 which would improve by two orders of magnitude of the strongest present limits obtained from ancient mica crystals.

Charged Q-ball dark matter from B and L direction

We consider nearly equal number of gauge mediation type charged (anti-) Q-balls with charge of ±α−1 ≃ ±137 well before the BBN epoch and discussed how they evolve in time. We found that ion-like objects with electric charges of +O(1) are likely to become relics in the present universe, which we expect to be the dark matter. These are constrained by MICA experiment, where the trail of heavy atom-like or ion-like object in 109 years old ancient mica crystals is not observed. We found that the allowed region for gauge mediation model parameter and reheating temperature have to be smaller than the case of the neutral Q-ball dark matter.

Probing the structure of the cold dark matter halo using ancient mica

Mica can store (for $>1\mathrm{Gyr}$) etchable tracks caused by atoms recoiling from WIMPs. Ancient mica is a directional detector despite the complex motions it makes with respect to the WIMP ``wind.'' We can exploit the properties of directionality and long integration time to probe for structure in the dark matter halo of our galaxy. We compute a sample of possible signals in mica for a plausible model of halo structure.

Unique Signature of Dark Matter in Ancient Mica

Mica can store (for >1 Gy) etchable tracks caused by atoms recoiling from WIMPs. Because a background from fission neutrons will eventually limit this technique, a unique signature for WIMPs in ancient mica is needed. Our motion around the center of the Galaxy causes WIMPs, unlike neutrons, to enter the mica from a preferred direction on the sky. Mica is a directional detector and despite the complex rotations that natural mica crystals make with respect to this WIMP ``wind,'' there is a substantial dependence of etch pit density on present day mica orientation.

Response of mica to weakly interacting massive particles.

We calculate spin-dependent cross sections for the scattering from mica of hypothetical weakly interacting dark-matter particles such as neutralinos. The most abundant odd-A isotopes in mica, $^{27}\mathrm{Al}$ and $^{39}\mathrm{K}$, require different shell-model treatments. The calculated cross sections will allow the interpretation of ongoing experiments that look for tracks due to the interaction of dark-matter particles with nuclei in ancient mica.

Search for weakly interacting massive particles in ancient mica

For a WIMP search the collecting power of a crystal of mica with a track-retention age of 10 9 years is far greater than can be attained with electronic detectors. We use an Atomic Force Microscope to measure the depths of etchpits due to recoil atoms in mica that has been calibrated with fast neutrons and low-energy ions of O, Si, K, and Fe. The background of alpha recoils is eliminated by making a range cut. The mica contains target atoms (F-19, Al-27, K-39, and K-41) with high cross sections for elastic scattering by neutralinos. Our first result with the mica technique is a WIMP flux limit comparable to the best limit attained with Ge detectors. It may be possible to increase the sensitivity by several orders of magnitude.

Polonium haloes in mica

GENTRY1 has reported that some anomalous haloes found in ancient mica seem to arise from the α-decay of polonium isotopes only, without any observable long-lived β-emitting precursors. Fremlin2 suggested that these might occur as a result of the diffusion of β-emitting radiogenic lead isotopes from relatively distant or widely dispersed uranium or thorium inclusions, and the absorption of the lead ions by small preexisting inclusions of foreign material. As Gentry3 pointed out, this would involve abnormally high diffusion rates for lead. We have carried out experiments that demonstrate the possibility of such high rates. Here we also discuss the reasons for the absence of an excess of observable tracks left in mica by the recoil of the lead daughter when α-decay takes place in the polonium isotopes.

Radiogenic argon and strontium diffusion parameters in biotite at low temperatures obtained from Alpine Fault uplift in New Zealand

Rapid uplift along the Alpine Fault zone in New Zealand has exposed ancient mica schists which are estimated to have been at depths up to 9000 ft prior to the fault displacement, on the assumption that the smooth surface represented by the present, flat topped, peak elevations is truly representative of the mature Pliocene surface prior to uplift and glaciation. K-Ar age measurements on the micas show losses of radiogenic argon that vary with depth of burial up to almost complete loss from biotite at a depth of 9000 ft. The mean value of the diffusion parameter ( D a 2 ) calculated is 6 × 10 −16 sec −1 at an estimated temperature of 110°C. This value is much higher than expected but is compatible with effectively complete retention of argon at surface temperatures, and with measured diffusion losses at high temperatures, if in the relationship D a 2 = ( D 0 a 2 ) exp (- E RT ) D 0 a 2 = 1 sec −1 and E = 27 Kcals/ mole. A single Rb-Sr analysis on one of the low argon biotite samples showed an almost equal loss of radiogenic Sr 87.