7,727 research outputs found
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Subsolar noble gases in an acid-resistant residue of the EH5 chondrite St Mark's
Extract from the introduction: Enstatite chondrites have remarkable properties: they were formed in a reducing environment, they are putatively similar to precursor material of Earth, Venus, or Mercury, have a terrestrial oxygen isotopic composition and an uncommon noble gas signature [1-5]. Trapped noble gases in Echondrites are intermediate between solar and chondritic composition and consist of two components: Subsolar, enriched in Ar and Kr relative to Xe and Q-gas, possibly residing in enstatite, micro-vesicles or graphite within enstatite [6,7] and Q-gases [5,8]
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Phase Q - A carrier for subsolar noble gases
We discuss noble gases in the E-chondrite St. Mark's indicating that the subsolar component does not exclusively reside in enstatite. Element and isotope abundances including He are presented. Fractionation probably took place prior to incorporation
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Helium isotopic ratios in carbonaceous chondrites: Significant for the early solar nebula and circumstellar diamonds?
Stepwise etching of acid-resistant residues from carbonaceous chondrites yields a new, extraordinarily low He isotopic ratio for phase Q that might represent early solar nebula composition. A much lower ratio possibly characterizes He-P3 from circumstellar diamonds
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On line etching of bulk EH5 St. Mark's – Radiogenic and subsolar noble gases
Introduction: On line etching is very useful to analyse noble gas components such as 'Q' or the solar wind [1, 2]. A bulk meteorite sample, however, has never been analysed by on line etching in order to characterise its complete noble gas inventory
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Solar noble bases in enstatite chondrites and implications for the formation of the terrestrial planets
We report evidence for tiny amounts of - most likely primordial - noble gases with solar-like elemental and isotopic composition admixed to Q-type primordial noble gases in an E chondrite. We will discuss possible implications of this finding for terrestrial planet formation
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The ingredients of the “Subsolar” noble gas component
On the basis of several experiments on separates of the EH5 chondrite St. Mark–s, we will argue that the 'subsolar' noble gas component is a mixture of solar-like, Q- and terrestrial noble gases
Bremsstrahlung Pair Production In Relativistic Heavy Ion Collision
We calculate production of electron- and muon-pairs by the bremsstrahlung
process in hadron collisions and compare it with the dominant two-photon
process. Results for the total cross section are given for proton-proton and
heavy-ion collisions at energies of the Relativistic Heavy Ion Collider (RHIC)
and the Large Hadron Collider (LHC).Comment: 6 pages, Latex, 9 figures using epsf-style. Accepted for publication
in Z. Phys.
Hadron collider limits on anomalous couplings
A next-to-leading log calculation of the reactions and
is presented including a tri-boson
gauge coupling from non-Standard Model contributions. Two approaches are made
for comparison. The first approach considers the tri-boson coupling
as being uniquely fixed by tree level unitarity at high energies to its
Standard Model form and, consequently, suppresses the non-Standard Model
contributions with form factors. The second approach is to ignore such
considerations and calculate the contributions to non-Standard Model tri-boson
gauge couplings without such suppressions. It is found that at Tevatron
energies, the two approaches do not differ much in quantitative results, while
at Large Hadron Collider (LHC) energies the two approaches give significantly
different predictions for production rates. At the Tevatron and LHC, however,
the sensitivity limits on the anomalous coupling of are too weak to
usefully constrain parameters in effective Lagrangian models.Comment: Revtex 23 pages + 8 figures, UIOWA-94-1
Mechanisms for Direct Breakup Reactions
We review some simple mechanisms of breakup in nuclear reactions. We mention
the spectator breakup, which is described in the post-form DWBA. The relation
to other formulations is also indicated. An especially important mechanism is
Coulomb dissociation. It is a distinct advantage that the perturbation due to
the electric field of the nucleus is exactly known. Therefore firm conclusions
can be drawn from such measurements. Some new applications of Coulomb
dissociation for nuclear astrophysics are discussed.Comment: 17 pages, 5 figures, to appear in the proceedings of the RCNP-TMU
Symposium on Spins in Nuclear and Hadronic Reactions, October 16-18 199
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