Probing the MSSM Higgs Sector at an e−e− Collider

The theoretical structure of the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) is briefly described. An outline of Higgs phenomenology at future lepton colliders is presented, and some opportunities for probing the physics of the MSSM Higgs sector at an e−e− collider are considered. To appear in e−e− 97: Proceedings of Electron–Electron Linear Collider Workshop Santa Cruz, CA, September 22–24, 1997 International Journal of Modern Physics A Special Proceedings Issue, June 1998 PROBING THE MSSM HIGGS SECTOR AT AN e−e− COLLIDER HOWARD E. HABER∗ Santa Cruz Institute for Particle Physics University of California, Santa Cruz, CA 95064, USA The theoretical structure of the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) is briefly described. An outline of Higgs phenomenology at future lepton colliders is presented, and some opportunities for probing the physics of the MSSM Higgs sector at an e−e− collider are considered. 1. Review of the MSSM Higgs Sector The Minimal Supersymmetric extension of the Standard Model (MSSM) contains the Standard Model particle spectrum and the corresponding supersymmetric partners.1−3 In addition, the MSSM must possess two Higgs doublets in order to give masses to up and down type fermions in a manner consistent with supersymmetry (and to avoid gauge anomalies introduced by the fermionic superpartners of the Higgs bosons). In particular, the MSSM Higgs sector is a CP-conserving two-Higgs-doublet model, which can be parameterized at tree-level in terms of two Higgs sector parameters. This structure arises due to constraints imposed by supersymmetry that fix the Higgs quartic couplings in terms of electroweak gauge coupling constants. Let Φ1 and Φ2 denote two complex Y = 1, SU(2)L doublet scalar fields. The most general gauge invariant CP-conserving scalar potential is given by V = m11Φ † 1Φ1 +m 2 22Φ † 2Φ2 − [m 2 12Φ † 1Φ2 + h.c.] + 12λ1(Φ † 1Φ1) 2 + 12λ2(Φ † 2Φ2) 2 + λ3(Φ † 1Φ1)(Φ † 2Φ2) + λ4(Φ † 1Φ2)(Φ † 2Φ1) + { 1 2λ5(Φ † 1Φ2) 2 + [ λ6(Φ † 1Φ1) + λ7(Φ † 2Φ2) ] Φ†1Φ2 + h.c. } , (1) where all parameters introduced above are real. Supersymmetry imposes the following constraints on the tree-level values of the quartic couplings λi: λ1 = λ2 = 1 4 (g 2 + g) , λ3 = 1 4 (g 2 − g) , λ4 = − 1 2g 2 , λ5 = λ6 = λ7 = 0 . (2) The tree-level Higgs masses and mixing can now be computed in the usual manner. The scalar fields will develop non-zero vacuum expectation values if the mass matrix ∗Work supported in part by the Department of Energy, Contract DE-FG03 92ER40689