First limit on inclusive B → Xsνν̄ decay and constraints on new physics

Yuval Grossman, Zoltan Ligeti, Enrico Nardi

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The inclusive Β → Χs ν ν̄ decay rate, on which no experimental bound exists to date, can be constrained by searching for large missing energy events in B decays. Carefully examining the experimental and theoretical aspects of such an analysis, we argue that the published ALEPH limit on BR(B → τν̄) implies, conservatively, the bound BR(B → Xs ν ν̄) < 3.9 × 10-4, which is less than one order of magnitude above the standard model prediction. The LEP collaborations could significantly improve this bound by a dedicated experimental analysis. We study the constraints this new limit imposes on various extensions of the standard model. We derive new bounds on the couplings of third generation fermions in models with leptoquarks, and in supersymmetric models without R-parity. We also constrain models where new gauge bosons are coupled dominantly to the third generation, such as TopColor models and models based on horizontal gauge symmetries. For models which predict an enhanced effective bsZ vertex, the constraint from B → Xs ν ν̄ is competitive with the limits from inclusive and exclusive B → Xs+ℓ decays.

Original languageEnglish
Pages (from-to)369-398
Number of pages30
JournalNuclear Physics B
Issue number3
StatePublished - 22 Apr 1996
Externally publishedYes

Bibliographical note

Funding Information:
We are grateful to Ian Tomalin of ALEPH for very helpful correspondence about the experimental analysis. We also thank Yossi Nir and Mark Wise for discussions and comments on the manuscript. Z.L. was supported in part by the U.S. Dept. of Energy under Grant no. DE-FG03-92-ER 40701.


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