The PAMELA excess from neutralino annihilation in the NMSSM - High Energy Physics - PhenomenologyReport as inadecuate

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Abstract: We examine whether the cosmic ray positron excess observed by PAMELA can beexplained by neutralino annihilation in the Next-to-Minimal SupersymmetricStandard Model NMSSM. The main dark matter annihilation products are thelightest CP-even scalar h1 plus the lightest CP-odd scalar a1, with the a1decaying into two muons. The energetic positrons needed to explain PAMELA arethus obtained in the NMSSM simply from kinematics. The required largeannihilation cross section is obtained from an s-channel resonance with theheavier CP-odd scalar a2. Various experiments constrain the PAMELA-favoredNMSSM parameter space, including collider searches for a light a1. Theseconstraints point to a unique corner of the NMSSM parameter space, having alightest neutralino mass around 160 GeV and a very light pseudoscalar mass lessthan a GeV. A simple parameterized formula for the charge-dependent solarmodulation effects reconciles the discrepancy between the PAMELA data and theestimated background at lower energies. We also discuss the electron and gammaray spectra from the Fermi LAT observations, and point out the discrepancybetween the NMSSM predictions and Fermi LAT preliminary results and possibleresolution. An NMSSM explanation of PAMELA makes three striking and uniquelycorrelated predictions: the rise in the PAMELA positron spectrum will turn overat around 70 GeV, the dark matter particle mass is less than the top quarkmass, and a light sub-GeV pseudoscalar will be discovered at colliders.

Author: Yang Bai, Marcela Carena, Joseph Lykken


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