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The Higgs Sector in a $U(1)^\prime$ Extension of the MSSM

Tao Han, Paul Langacker, Bob McElrath

Abstract

We consider the Higgs sector in an extension of the MSSM with extra SM singlets, involving an extra $U(1)^\prime$ gauge symmetry, in which the domain-wall problem is avoided and the effective $μ$ parameter is decoupled from the new gauge boson $Z^\prime$ mass. The model involves a rich Higgs structure very different from that of the MSSM. In particular, there are large mixings between Higgs doublets and the SM singlets, significantly affecting the Higgs spectrum, production cross sections, decay modes, existing exclusion limits, and allowed parameter range. Scalars considerably lighter than the LEP2 bound (114 GeV) are allowed, and the range $\tan β\sim 1$ is both allowed and theoretically favored. Phenomenologically, we concentrate our study on the lighter (least model-dependent, yet characteristic) Higgs particles with significant SU(2)-doublet components to their wave functions, for the case of no explicit CP violation in the Higgs sector. We consider their spectra, including the dominant radiative corrections to their masses from the top/stop loop. We computed their production cross sections and reexamine the existing exclusion limits at LEP2. We outline the searching strategy for some representative scenarios at a future linear collider. We emphasize that gaugino, Higgsino, and singlino decay modes are indicative of extended models and have been given little attention. We present a comprehensive list of model scenarios in the Appendices.

The Higgs Sector in a $U(1)^\prime$ Extension of the MSSM

Abstract

We consider the Higgs sector in an extension of the MSSM with extra SM singlets, involving an extra gauge symmetry, in which the domain-wall problem is avoided and the effective parameter is decoupled from the new gauge boson mass. The model involves a rich Higgs structure very different from that of the MSSM. In particular, there are large mixings between Higgs doublets and the SM singlets, significantly affecting the Higgs spectrum, production cross sections, decay modes, existing exclusion limits, and allowed parameter range. Scalars considerably lighter than the LEP2 bound (114 GeV) are allowed, and the range is both allowed and theoretically favored. Phenomenologically, we concentrate our study on the lighter (least model-dependent, yet characteristic) Higgs particles with significant SU(2)-doublet components to their wave functions, for the case of no explicit CP violation in the Higgs sector. We consider their spectra, including the dominant radiative corrections to their masses from the top/stop loop. We computed their production cross sections and reexamine the existing exclusion limits at LEP2. We outline the searching strategy for some representative scenarios at a future linear collider. We emphasize that gaugino, Higgsino, and singlino decay modes are indicative of extended models and have been given little attention. We present a comprehensive list of model scenarios in the Appendices.

Paper Structure

This paper contains 27 sections, 79 equations, 10 figures, 1 table.

Table of Contents

  1. Introduction
  2. The Model
  3. General structure
  4. Higgs sector and electroweak symmetry breaking
  5. Phenomenological Constraints
  6. Parameter Space
  7. $Z^\prime$ Mass and $Z-Z^\prime$ Mixing
  8. Chargino and Neutralino Mass Bounds
  9. LEP2 Bounds on the Higgs Masses
  10. Mass Spectrum and Couplings for Higgs Bosons
  11. Higgs Boson Decay and Production in $e^+e^-$ Collisions
  12. Lightest CP-Even State $H_1$
  13. CP-Odd
  14. The Higgs signatures at a linear collider
  15. Summary and Conclusions
  16. ...and 12 more sections

Figures (10)

  • Figure 1: Cross sections at LEP2 (a) for $ZH_i$ production and (b) for $A_iH_j$ production versus the relevant Higgs boson mass. In (a), the solid curve is the SM production, and the dashed, dotted and dash-dotted are for the MSSM with $\tan\beta=5,10,20$, respectively. In (b), the curves is with $\tan\beta=5$.
  • Figure 2: (a) $M_H-M_A$ mass plane, labeled according to MSSM fraction $\xi_{\rm MSSM}$. For each point both $H_i$ and $A_i$ satisfy the condition $\xi_{\rm MSSM} > 0, 0.001, 0.01, 0.1$, or $0.9$. All pairs $(M_{H_i}, M_{A_j})$ are plotted. (b) $M_{H^+}-M_A$ mass plane with the MSSM $A^{\rm MSSM}$ mass $M^{\rm MSSM}_A = 2 A_h h v_s/\sin{2 \beta}$ included for comparison.
  • Figure 3: The MSSM fraction (a) for the CP-even and (b) for the CP-odd states.
  • Figure 4: $ZZH$ coupling of the CP-even Higgs, relative to the Standard Model $ZZH$ coupling.
  • Figure 5: Range of $\tan\beta$ versus (a) the CP-even, and (b) CP-odd masses.
  • ...and 5 more figures