119 research outputs found
Color-flavor locked strange matter and strangelets at finite temperature
It is possible that a system composed of up, down and strange quarks consists
the true ground state of nuclear matter at high densities and low temperatures.
This exotic plasma, called strange quark matter (SQM), seems to be even more
favorable energetically if quarks are in a superconducting state, the so-called
color-flavor locked state. Here are presented calculations made on the basis of
the MIT bag model considering the influence of finite temperature on the
allowed parameters characterizing the system for stability of bulk SQM (the
so-called stability windows) and also for strangelets, small lumps of SQM, both
in the color-flavor locking scenario. We compare these results with the
unpaired SQM and also briefly discuss some astrophysical implications of them.
Also, the issue of strangelet's electric charge is discussed. The effects of
dynamical screening, though important for non-paired SQM strangelets, are not
relevant when considering pairing among all three flavor and colors of quarks.Comment: 17 pp. 15 figs., to appear in Phys. Rev.
Propagation of strangelets in the Earth's atmosphere
A new model for the description of the behaviour of strangelets in the
Earth's atmosphere is presented. Strangelet fission induced by collision with
air nuclei is included. It is shown that strangelets with certain parameters of
initial mass and energy may reach depths near sea level, which can be examined
by ground-based experiments.Comment: 10 pages, 6 figure
Trapping of strangelets in the geomagnetic field
Strangelets coming from the interstellar medium (ISM) are an interesting
target to experiments searching for evidence of this hypothetic state of
hadronic matter. We entertain the possibility of a {\it trapped} strangelet
population, quite analogous to ordinary nuclei and electron belts. For a
population of strangelets to be trapped by the geomagnetic field, these
incoming particles would have to fulfill certain conditions, namely having
magnetic rigidities above the geomagnetic cutoff and below a certain threshold
for adiabatic motion to hold. We show in this work that, for fully ionized
strangelets, there is a narrow window for stable trapping. An estimate of the
stationary population is presented and the dominant loss mechanisms discussed.
It is shown that the population would be substantially enhanced with respect to
the ISM flux (up to two orders of magnitude) due to quasi-stable trapping.Comment: 10 pp., 5 figure
The internal alignment and position resolution of the AMS-02 silicon tracker determined with cosmic-ray muons
Abstract The Alpha Magnetic Spectrometer is a large acceptance cosmic-ray detector ( 0.5 m 2 sr ) designed to operate at an altitude of 400 km on the International Space Station. The AMS-02 silicon tracker contains 2264 silicon microstrip sensors (total active area 6.75 m 2 ). The internal alignment parameters of the assembled tracker have been determined on the ground with cosmic-ray muons. The alignment procedure is described and results for the alignment precision and position resolution are reported
Positrons and antiprotons from inert doublet model dark matter
In the framework of the Inert Doublet Model, a very simple extension of the
Standard Model, we study the production and propagation of antimatter in cosmic
rays coming from annihilation of a scalar dark matter particle. We consider
three benchmark candidates, all consistent with the WMAP cosmic abundance and
existing direct detection experiments, and confront the predictions of the
model with the recent PAMELA, ATIC and HESS data. For a light candidate, M_{DM}
= 10 GeV, we argue that the positron and anti-proton fluxes may be large, but
still consistent with expected backgrounds, unless there is an enhancement
(boost factor) in the local density of dark matter. There is also a substantial
anti-deuteron flux which might be observable by future experiments. For a
candidate with M_{DM} = 70 GeV, the contribution to positron and anti-proton
fluxes is much smaller than the expected backgrounds. Even if a boost factor is
invoked to enhance the signals, the candidate is unable to explain the observed
positron and anti-proton excesses. Finally, for a heavy candidate, M_{DM} = 10
TeV, it is possible to fit the PAMELA excess (but, unfortunately, not the ATIC
one) provided there is a large enhancement, either in the local density of dark
matter or through the Sommerfeld effect.Comment: 17 pages ; v2: matches JCAP published versio
Precision Measurement of the Boron to Carbon Flux Ratio in Cosmic Rays from 1.9 GV to 2.6 TV with the Alpha Magnetic Spectrometer on the International Space Station
Knowledge of the rigidity dependence of the boron to carbon flux ratio (B/C) is important in understanding the propagation of cosmic rays. The precise measurement of the B/C ratio from 1.9 GV to 2.6 TV, based on 2.3 million boron and 8.3 million carbon nuclei collected by AMS during the first 5 years of operation, is presented. The detailed variation with rigidity of the B/C spectral index is reported for the first time. The B/C ratio does not show any significant structures in contrast to many cosmic ray models that require such structures at high rigidities. Remarkably, above 65 GV, the B/C ratio is well described by a single power law R[superscript Δ] with index Δ=-0.333±0.014(fit)±0.005(syst), in good agreement with the Kolmogorov theory of turbulence which predicts Δ=-1/3 asymptotically.National Science Foundation (U.S.) (Grants 1455202 and 1551980)Wyle Research (Firm) (Grant 2014/T72497)United States. National Aeronautics and Space Administration (NASA Earth and Space Science Fellowship Grant HELIO15F-0005
Properties of Iron Primary Cosmic Rays: Results from the Alpha Magnetic Spectrometer
We report the observation of new properties of primary iron (Fe) cosmic rays in the rigidity range 2.65 GV to 3.0 TV with 0.62 million iron nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. Above 80.5 GV the rigidity dependence of the cosmic ray Fe flux is identical to the rigidity dependence of the primary cosmic ray He, C, and O fluxes, with the Fe/O flux ratio being constant at 0.155±0.006. This shows that unexpectedly Fe and He, C, and O belong to the same class of primary cosmic rays which is different from the primary cosmic rays Ne, Mg, and Si class
Properties of Heavy Secondary Fluorine Cosmic Rays: Results from the Alpha Magnetic Spectrometer
Precise knowledge of the charge and rigidity dependence of the secondary cosmic ray fluxes and the secondary-to-primary flux ratios is essential in the understanding of cosmic ray propagation. We report the properties of heavy secondary cosmic ray fluorine F in the rigidity R range 2.15 GV to 2.9 TV based on 0.29 million events collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The fluorine spectrum deviates from a single power law above 200 GV. The heavier secondary-to-primary F/Si flux ratio rigidity dependence is distinctly different from the lighter B/O (or B/C) rigidity dependence. In particular, above 10 GV, the F/SiB/O ratio can be described by a power law Rδ with δ=0.052±0.007. This shows that the propagation properties of heavy cosmic rays, from F to Si, are different from those of light cosmic rays, from He to O, and that the secondary cosmic rays have two classes
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