A cosmological lower bound on the neutron electric dipole moment

John Ellis, Mary K. Gaillard, D. V. Nanopoulos, Serge Rudaz

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33 Scopus citations

Abstract

We argue that in a wide class of grand unified theories diagrams similar to those generating baryon number in the early universe also contribute to renormalization of the CP-violating θ parameter of QCD and hence to the neutron electric dipole moment dn. We then use the apparent baryon-to-photon ratio ( nB nγ) ≳ 1.3 × 10-10 to deduce an order-of-magnitude lower bound on the neutron electric dipole moment: dn ≳ 3 × 10-28 e cm. Conversely the present experimental upper limit on dn implies ( nB nγ) ≲ 6 × 10-7. We find as a corollary that there is not much scope for entropy generation after the creation of the baryon-antibaryon asymmetry in the very early universe.

Original languageEnglish (US)
Pages (from-to)101-106
Number of pages6
JournalPhysics Letters B
Volume99
Issue number2
DOIs
StatePublished - Feb 12 1981

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