Be Isotopes Measurement with AMS-02 to reduce Astrophysical Uncertainty from Dark Matter Models

by Dr Abhinandon Dass

Thursday Oct 10, 2024, 3:30 PM → 4:30 PM Pacific/Honolulu

Room 112 (Watanabe Hall)

The p/p ratio published by AMS-02 shows an excess of ¯p at rigidities above 60 GeV , which can potentially be from WIMP annihilation. To that end, one has to decouple the contribution of secondary ¯p coming from standard p + He/H → ¯p + X process. However models computing the latter component are affected by astrophysical and nuclear uncertainties. To reduce the former, the Φ10Be/Φ9Be ratio is calculated by analyzing 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. 7Be, 9Be, and 10Be. 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 utilized to compute the ratios, Φ10Be/Φ9Be and Φ7Be/ΦTotal Be. The former is compared with various theoretical models for computation of galactic halo sizes from the Φ10Be/Φ9Be ratio; which suggests that the AMS-02 results severely challenges our understanding of halo sizes.  Furthermore, for the measurement of the ¯p 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 ¯p identification. As such, a Monte-Carlo simulation of the detector is developed in Geant4, and a reconstruction algorithm is written. 

abhinandan_AMS_PhyCollq.pdf

Video - Dr. A. Dass