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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

BE ISOTOPE MEASUREMENT WITH AMS-02 TO REDUCE ASTROPHYSICAL UNCERTAINTY IN DARK MATTER MODELS

Dass, Abhinandan 14 June 2024 (has links)
The p̄/p ratio published by AMS-02 shows an excess of p̄ at rigidities above 60 GV , which can potentially be from WIMP annihilation. To that end, one has to decouple the contribution of secondary p̄ coming from standard p + He/H → p̄ + X process. However models computing the latter component are affected by astrophysical and nuclear uncertainties. To reduce the former, the 10 Be/ 9 Be ratio is calculated by analysing 10 years of AMS-02 Be data. A set of selection criteria is developed to extract a pure sample of Be, and a fit model is constructed to extract the counts of the Be isotopes viz. 7 Be, 9 Be, and 10 Be. Additionally, the detector acceptance is computed using the AMS-MC datasets for Be, and the RTI information from the AMS-02 data is employed to calculate the exposure time. Using these components, the detector level fluxes are calculated for each of the isotopes which is then unfolded using a Bayesian iterative unfolding procedure to extract the particle level fluxes. These fluxes are then utilised to compute the ratios, 10 Be/ 9 Be and 7 Be/Total Be. The former is compared with various theoretical models for computation of galactic halo sizes from the 10 Be/ 9 Be ratio; which suggests that the AMS-02 results severely challenges our understanding of halo sizes. Furthermore, for the measurement of the p̄ production cross-section, p beam at various energies from the CERN Super Proton Synchrotron are directed at a liquid He target within the COMPASS++/AMBER experimental hall. For this purpose, the COMPASS-RICH detector is used for p̄ identification. As such, a Monte-Carlo simulation of the detector is developed in Geant4, and a reconstruction algorithm is written. This work is presented as an appendix to the thesis.

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