TY - JOUR

T1 - Theoretical constraints on the Higgs effective couplings

AU - Low, Ian

AU - Rattazzi, Riccardo

AU - Vichi, Alessandro

PY - 2010

Y1 - 2010

N2 - We derive constraints on the sign of couplings in an effective Higgs Lagrangian using prime principles such as the naturalness principle, global symmetries, and unitarity. Specifically, we study four dimension-six operators, OH, Oy, Og, and Oγ, which contribute to the production and decay of the Higgs boson at the Large Hadron Collider (LHC), among other things. Assuming the Higgs is a fundamental scalar, we find: 1) the coefficient of OH is positive except when there are triplet scalars, resulting in a reduction in the Higgs on-shell coupling from their standard model (SM) expectations if no other operators contribute, 2) the linear combination of OH and Oy controlling the overall Higgs coupling to fermion is always reduced, 3) the sign of Og induced by a new colored fermion is such that it interferes destructively with the SM top contribution in the gluon fusion production of the Higgs, if the new fermion cancels the top quadratic divergence in the Higgs mass, and 4) the correlation between naturalness and the sign of Oγ is similar to that of Og, when there is a new set of heavy electroweak gauge bosons. Next considering a composite scalar for the Higgs, we find the reduction in the on-shell Higgs couplings persists. If further assuming a collective breaking mechanism as in little Higgs theories, the coefficient of OH remains positive even in the presence of triplet scalars. In the end, we conclude that the gluon fusion production of the Higgs boson is reduced from the SM rate in all composite Higgs models. Our study suggests a wealth of information could be revealed by precise measurements of the Higgs couplings, providing strong motivations for both improving on measurements at the LHC and building a precision machine such as the linear collider.

AB - We derive constraints on the sign of couplings in an effective Higgs Lagrangian using prime principles such as the naturalness principle, global symmetries, and unitarity. Specifically, we study four dimension-six operators, OH, Oy, Og, and Oγ, which contribute to the production and decay of the Higgs boson at the Large Hadron Collider (LHC), among other things. Assuming the Higgs is a fundamental scalar, we find: 1) the coefficient of OH is positive except when there are triplet scalars, resulting in a reduction in the Higgs on-shell coupling from their standard model (SM) expectations if no other operators contribute, 2) the linear combination of OH and Oy controlling the overall Higgs coupling to fermion is always reduced, 3) the sign of Og induced by a new colored fermion is such that it interferes destructively with the SM top contribution in the gluon fusion production of the Higgs, if the new fermion cancels the top quadratic divergence in the Higgs mass, and 4) the correlation between naturalness and the sign of Oγ is similar to that of Og, when there is a new set of heavy electroweak gauge bosons. Next considering a composite scalar for the Higgs, we find the reduction in the on-shell Higgs couplings persists. If further assuming a collective breaking mechanism as in little Higgs theories, the coefficient of OH remains positive even in the presence of triplet scalars. In the end, we conclude that the gluon fusion production of the Higgs boson is reduced from the SM rate in all composite Higgs models. Our study suggests a wealth of information could be revealed by precise measurements of the Higgs couplings, providing strong motivations for both improving on measurements at the LHC and building a precision machine such as the linear collider.

KW - Beyond standard model

KW - Higgs physics

KW - Technicolor and composite models

UR - http://www.scopus.com/inward/record.url?scp=77954934625&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77954934625&partnerID=8YFLogxK

U2 - 10.1007/JHEP04(2010)126

DO - 10.1007/JHEP04(2010)126

M3 - Article

AN - SCOPUS:77954934625

SN - 1126-6708

VL - 2010

JO - Journal of High Energy Physics

JF - Journal of High Energy Physics

IS - 4

M1 - 126

ER -