Probing minimal supergravity via the extreme universe space observatory

Luis Anchordoqui, Northeastern University
Haim Goldberg, Northeastern University
Pran Nath, Northeastern University

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Originally published in Physical Review D v.70 (2004): 025014. DOI: 10.1103/PhysRevD.70.025014

Abstract

An analysis is carried out within mSUGRA of the estimated number of events originating from upward moving ultrahigh energy neutralinos passing through Earth’s crust that could be detected by the Extreme Universe Space Observatory (EUSO). The analysis exploits a recently proposed technique that differentiates ultrahigh energy neutralinos from ultrahigh energy neutrinos using their different absorption lengths in the Earth’s crust. It is shown that for the part of the parameter space, where the neutralino is mostly a B-ino and with squark mass ∼1TeV, EUSO could see ultrahigh energy neutralino events within mSUGRA models with essentially no background. In the energy range 10⁹GeV1¹GeV the unprecedented aperture of EUSO makes the telescope sensitive, after 3 yr of observation, to neutralino fluxes as low as dΦ/dEₓ>1.1×10⁻⁶(Eₓ/GeV)^-1.3GeV⁻¹cm⁻²yr⁻¹sr⁻¹, at the 95% confidence limit (CL). Such a hard spectrum is characteristic of supermassive particles’ N-body hadronic decay. The case in which the flux of ultrahigh energy neutralinos is produced via decay of metastable heavy (mₓ=2×10¹²GeV) particles with uniform distribution throughout the Universe, and primary decay mode into 5 quarks + 5 squarks, is analyzed in detail. The normalization of the ratio of the relics’ density to their lifetime has been fixed so that the baryon flux produced in the supermassive particle decays contributes to about 1/3 of the events reported by the AGASA Collaboration below 10¹¹GeV, and hence the associated GeV γ-ray flux is in complete agreement with EGRET data. For this particular case, EUSO will collect between 4 and 5 neutralino events (with 0.3 of background) in ≈3yr of running. NASA’s planned mission, the Orbiting Wide-angle Light-collectors (OWL), is also briefly discussed in this context.