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Direction de la Recherche Fondamentale  -  Saclay
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Saturday, September 23, 2017

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String Theory D3-brane constructions of physics beyond the Standard Model ruled out by the LHC   
imgThe standard model of particle physics arises in string theory from open strings ending on membranes (D-branes) extended along the three-dimensional space. Closed strings propagating along the whole ten-dimensional world of string theory play the role of the hidden sector, communicating to the matter sector the breaking of supersymmetry that takes place in the extra dimensions in the form of “soft terms” (which have this name because they break supersymmetry without causing ultraviolet divergences).
However, not any soft-supersymmetry-breaking Lagrangian can be obtained this way since the string theory equations of motion and consistency conditions impose relations between the soft couplings. Iosif Bena, Mariana Graña and collaborators have shown that for models realized on D3-branes the trace of the square of the boson mass matrix is equal to the trace of the square of the fermion mass matrix at tree level, and this equality holds at least up to two loops [1].  String theory thus dictates that supersymmetric extensions of the standard model built using these branes cannot have all the scalar super-particles very massive at the same time, and are therefore basically ruled out by LHC.

[1] I. Bena, M. Graña, S. Kuperstein, P. Ntokos and M. Petrini, "D3-brane model building and the supertrace rule", Phys. Rev. Lett. 116, 141601 (2016).
 
C. Pepin, 2017-03-22

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