  It is proposed that the neutral, B=2, flavor singlet sexaquark (S) composed
of uuddss quarks, has mass m_S <~ 2 GeV. If m_S < 2 (m_p + m_e), it is
absolutely stable, while for m_S < m_p+m_e + m_Lambda, its lifetime can be
greater than the age of the Universe. Lattice gauge theory cannot yet predict
m_S, but indirect evidence supports the hypothesis of stability. A stable S is
consistent with QCD theory and would have eluded detection in accelerator and
non-accelerator experiments. If it exists, the S is a good Dark Matter
candidate. Analyses of existing Upsilon decay and LHC data can be used to
discover it and measure its mass.
