Browsing by Author "Sinha, Kuver"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Natural supersymmetry, muon g−2, and the last crevices for the top squark
    (American Physical Society, 2015) Padley, B. Paul; Sinha, Kuver; Wang, Kechen
    We study the interplay of natural supersymmetry and a supersymmetric solution to the discrepancy observed in measurements of the muon magnetic moment. The strongest constraints on the parameter space currently come from chargino searches in the trilepton channel and slepton searches in the dilepton channel at the LHC, and vast regions are currently allowed, especially at large tanβ. With light top squarks in the spectrum, as required from naturalness arguments, the situation changes dramatically; stop-assisted chargino and neutralino production via t˜→bχ˜±1 and t˜→tχ˜01 are already probing the entire parameter space compatible with the muon magnetic moment at tanβ∼O(10), while upcoming stop searches will probe most of the parameter space at larger tanβ∼40. Direct Higgsino searches as well as compressed slepton and stop searches are crucial to close out corners of parameter space. We consider one such example: in the presence of light sleptons and charginos as required to obtain appreciable contributions to the muon magnetic moment, compressed stops can dominantly undergo the following decay t˜→bℓ˜ν(ν˜ℓ)→bℓνχ˜01, facilitated by off-shell charginos. We find that the enhanced branching to leptons leads to a 5σ mass reach (with 3000  fb−1 of data at LHC14) of mt˜∼350  GeV, with the mass difference between stops and the lightest neutralino being ∼80  GeV. This will further close out a significant part of the parameter space compatible with naturalness and the muon magnetic moment.
  • Thumbnail Image
    Item
    New limits on the dark matter lifetime from dwarf spheroidal galaxies using Fermi-LAT
    (American Physical Society, 2016) Baring, Matthew G.; Ghosh, Tathagata; Queiroz, Farinaldo S.; Sinha, Kuver
    Dwarf spheroidal galaxies (dSphs) are promising targets for the indirect detection of dark matter through gamma-ray emission due to their proximity, lack of astrophysical backgrounds and high dark matter density. They are often used to place restrictive bounds on the dark matter annihilation cross section. In this paper, we analyze six years of Fermi-LAT gamma-ray data from 19 dSphs that are satellites of the Milky Way, and derive from a stacked analysis of 15 dSphs, robust 95% confidence level lower limits on the dark matter lifetime for several decay channels and dark matter masses between ∼1  GeV and 10 TeV. Our findings are based on a bin-by-bin maximum likelihood analysis treating the J-factor as a nuisance parameter using the Pass 8 event class. Our constraints from this ensemble are among the most stringent and solid in the literature, and competitive with existing ones coming from the extragalactic gamma-ray background, galaxy clusters, AMS-02 cosmic ray data, Super-K and ICECUBE neutrino data, while rather insensitive to systematic uncertainties. In particular, among gamma-ray searches, we improve existing limits for dark matter decaying into ¯bb (μ+μ−) for dark matter masses below ∼30(200)  GeV, demonstrating that dSphs are compelling targets for constraining dark matter decay lifetimes.