Problems for superstring models with vacuum expectation values for conjugate sneutrinos

B. Campbell, J. Ellis, M. K. Gaillard, D. V. Nanopoulos, K. A. Olive

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Superstring models compactified on Calabi-Yau manifolds contain two new neutral scalars in each 27 generation of chiral supermultiplets. We consider implications of a vacuum expectation value for one of the neutral scalars, the conjugates neutrino νLc:〈0|;νLc|;0〉 y. Apart from a coupling from a coupling which generates a Dirac neutrino mass and which must be small [{less-than or approximate} O(10-9)], its only superpotential interaction is with DLdL, so there would be D-d mixing if y ≠ 0. The fact that md is not much less than me or mu then tells us that y {less-than or approximate} O (few TeV). When the four-dimensional gauge group has rank 5, a pseudo-Goldstone boson, aν, arises if y ≠ 0, and the D-d mixing would then induce the decay K → π + aν at an unacceptable rate. Regardless of the gauge group rank, we show that the combined constraints on D-d mixing, and on the flavour-changing neutral currents it would induce, are sufficient to rule out DLdLcνLc superpotential coupling large enough to produce 〈0|;νLc|;0〉 ≠ 0. These problems are avoided in models with a rank-5 gauge group and 〈0|;νLc|;0〉 {less-than or approximate} 40 KeV.

Original languageEnglish (US)
Pages (from-to)77-82
Number of pages6
JournalPhysics Letters B
Issue number1-2
StatePublished - Nov 6 1986

Bibliographical note

Funding Information:
One of us (B.A.C.) thankst heCERN Theory Divisionf or its kind hospitalityB.. A.C.'sr esearchis supporteidn part by NSERC grantA 8863. M.K.G.'s researcihs supporteidn part by the US Department of Energyu nderc ontracDt E-AC03-76SF00098a,n d in part by the NationaSl cienceF oundationu nder grantn umberP HY-85-15857K. .A.O. is supporteidn part by DOE grantD E-ACO2-83ER-40105.


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