2,299 research outputs found

    Abundance Uncertainties Obtained With the PizBuin Framework For Monte Carlo Reaction Rate Variations

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    Uncertainties in nucleosynthesis models originating from uncertainties in astrophysical reaction rates were estimated in a Monte Carlo variation procedure. Thousands of rates were simultaneously varied within individual, temperature-dependent errors to calculate their combined effect on final abundances. After a presentation of the method, results from application to three different nucleosynthesis processes are shown: the ╬│\gamma-process and the s-process in massive stars, and the main s-process in AGB stars (preliminary results). Thermal excitation of nuclei in the stellar plasma and the combined action of several reactions increase the final uncertainties above the level of the experimental errors. The total uncertainty, on the other hand, remains within a factor of two even in processes involving a large number of unmeasured rates, with some notable exceptions for nuclides whose production is spread over several stellar layers and for s-process branchings.Comment: 8 pages, 4 figures; Proceedings of OMEG 2017, Daejeon, Korea, June 27-30, 2017; to appear in AIP Conf. Pro

    The s-process nucleosynthesis : Impact of the uncertainties in the nuclear physics determined by monte carlo variations

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    We investigated the impact of uncertainties in neutron-capture and weak reactions (on heavy elements) on the s-process nucleosynthesis in low-mass stars and massive stars using a Monte-Carlo based approach. We performed extensive nuclear reaction network calculations that include newly evaluated temperature-dependent upper and lower limits for the individual reaction rates. We found ╬▓-decay rate uncertainties affect only a few nuclei near s-process branchings, whereas most of the uncertainty in the final abundances is caused by uncertainties in the neutron capture rates. We suggest a list of uncertain rates as candidates for improved measurement by future experiments.Peer reviewe

    Dynamical trapping and relaxation of scalar gravitational fields

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    We present a framework for nonlinearly coupled scalar-tensor theory of gravity to address both inflation and core-collapse supernova problems. The unified approach is based on a novel dynamical trapping and relaxation of scalar gravity in highly energetic regimes. The new model provides a viable alternative mechanism of inflation free from various issues known to affect previous proposals. Furthermore, it could be related to observable violent astronomical events, specifically by releasing a significant amount of additional gravitational energy during core-collapse supernovae. A recent experiment at CERN relevant for testing this new model is briefly outlined.Comment: 4 pages; version to appear in PL

    New physics searches with LUX and LZ

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    The frontier of experimental particle physics research, especially astroparticle physics, frequently involves the detection of signals that are both rare (fewer than an event per year per kilogram), and small (energy depositions at the keV scale). A prime example is the direct search for dark matter, although other signatures for new physics are also being sought, such as axions and various neutrino signals. The key technology that has evolved to meet this challenge is that of the ultra low background two-phase time projection chamber, deployed deep underground. The Large Underground Xenon (LUX) instrument was a leading device of this type. Now dismantled to make way for its successor, analysis of legacy data continues. The main scientific results of LUX are presented. With 50 times larger fiducial (usable) mass, and increased background rejection power, LUX-ZEPLIN (LZ) is presently under construction and is due to take first data in 2020. It will have a sensitivity at least two orders of magnitude beyond current best limits for the leading dark matter candidates. An overview of the LZ experiment is presented

    Cosmogenic production of 37Ar in the context of the LUX-ZEPLIN experiment

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    A consistent scalar-tensor cosmology for inflation, dark energy and the Hubble parameter

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    The authors are grateful for financial support to the Cruickshank Trust (CW), EPSRC/GG-Top (CW, JR), Omani Government (MA), Science Without Borders programme, CNPq, Brazil (DR), and STFC/CfFP (CW, AM, RB, JM). CW and AM acknowledge the hospitality of CERN, where this work was started. The University of Aberdeen and University of Edinburgh are charitable bodies registered in Scotland, with respective registration numbers SC013683 and SC005336.Peer reviewedPostprin

    Production Uncertainties of p-Nuclei in the ╬│-Process in Massive Stars Using a Monte Carlo Approach

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    T. Rauscher, N. Nishimura, R. Hirschi, G. Cescutti, A. St J. Murphy and A. Heger, 'Production Uncertainties of p-Nuclei in the ╬│-Process in Massive Stars Using a Monte Carlo Approach', in Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016). Niigata, Japan, June 19-25, 2016. ISBN: 978-4-89027-118-4. DOI: http://dx.doi.org/10.7566/JPSCP.14.010509. ┬ę 2017 The Physical Society of Japan.Proton-rich nuclei, the so-called p-nuclei, are made in photodisintegration processes in outer shells of massive stars in the course of the final supernova explosion. Nuclear uncertainties in the production of these nuclei have been quantified in a Monte Carlo procedure. Bespoke temperature-dependent uncertainties were assigned to different types of reactions involving nuclei from Fe to Bi and all rates were varied randomly within the uncertainties. The resulting total production uncertainties of the p-nuclei are below a factor of two, with few exceptions. Key reactions dominating the final uncertainties have been identified in an automated procedure using correlations between rate and abundance uncertainties. Our results are compared to those of a previous study manually varying reaction rates
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