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Electroweak Supersymmetry with an Approximate U(1)_PQ

Lawrence J. Hall, Taizan Watari

TL;DR

The paper presents a TeV-scale SUSY framework in which the μ parameter is dynamically generated by a singlet S via the λSH1H2 coupling, within an approximate U(1)_{PQ} that gives a heavy pseudo-Goldstone boson G. Electroweak phenomenology closely mirrors the MSSM, but with μ predicted by a CP-consistent relation μ = (A/2) sin(2β) and the presence of light singlet-dominated states that alter collider cascades through an extra decay stage involving the NLSP and the singlet sector. The framework remains compatible with terrestrial, astrophysical, and cosmological constraints, with cosmology offering novel signatures such as modified Nν during BBN and CMB, and a potential light LSP that could serve as warm dark matter given suitable entropy production. Its predictive μ relation and distinctive collider signals provide clear experimental tests that can distinguish it from the NMSSM and other PQ-breaking scenarios, while preserving MSSM-like EW-scale physics across a wide parameter range.

Abstract

A predictive framework for supersymmetry at the TeV scale is presented, which incorporates the Ciafaloni-Pomarol mechanism for the dynamical determination of the μparameter of the MSSM. It is replaced by (λS), where S is a singlet field, and the axion becomes a heavy pseudoscalar, G, by adding a mass, m_G, by hand. The explicit breaking of Peccei-Quinn (PQ) symmetry is assumed to be sufficiently weak at the TeV scale that the only observable consequence is the mass m_G. Three models for the explicit PQ breaking are given; but the utility of this framework is that the predictions for all physics at the electroweak scale are independent of the particular model for PQ breaking. Our framework leads to a theory similar to the MSSM, except that μis predicted by the Ciafaloni-Pomarol relation, and there are light, weakly-coupled states in the spectrum. The production and cascade decay of superpartners at colliders occurs as in the MSSM, except that there is one extra stage of the cascade chain, with the next-to-LSP decaying to its "superpartner" and \tilde{s}, dramatically altering the collider signatures for supersymmetry. The framework is compatible with terrestrial experiments and astrophysical observations for a wide range of m_G and <s>. If G is as light as possible, 300 keV < m_G < 3 MeV, it can have interesting effects on the radiation energy density during the cosmological eras of nucleosynthesis and acoustic oscillation, leading to predictions for N_{νBBN} and N_{νCMB} different from 3.

Electroweak Supersymmetry with an Approximate U(1)_PQ

TL;DR

The paper presents a TeV-scale SUSY framework in which the μ parameter is dynamically generated by a singlet S via the λSH1H2 coupling, within an approximate U(1)_{PQ} that gives a heavy pseudo-Goldstone boson G. Electroweak phenomenology closely mirrors the MSSM, but with μ predicted by a CP-consistent relation μ = (A/2) sin(2β) and the presence of light singlet-dominated states that alter collider cascades through an extra decay stage involving the NLSP and the singlet sector. The framework remains compatible with terrestrial, astrophysical, and cosmological constraints, with cosmology offering novel signatures such as modified Nν during BBN and CMB, and a potential light LSP that could serve as warm dark matter given suitable entropy production. Its predictive μ relation and distinctive collider signals provide clear experimental tests that can distinguish it from the NMSSM and other PQ-breaking scenarios, while preserving MSSM-like EW-scale physics across a wide parameter range.

Abstract

A predictive framework for supersymmetry at the TeV scale is presented, which incorporates the Ciafaloni-Pomarol mechanism for the dynamical determination of the μparameter of the MSSM. It is replaced by (λS), where S is a singlet field, and the axion becomes a heavy pseudoscalar, G, by adding a mass, m_G, by hand. The explicit breaking of Peccei-Quinn (PQ) symmetry is assumed to be sufficiently weak at the TeV scale that the only observable consequence is the mass m_G. Three models for the explicit PQ breaking are given; but the utility of this framework is that the predictions for all physics at the electroweak scale are independent of the particular model for PQ breaking. Our framework leads to a theory similar to the MSSM, except that μis predicted by the Ciafaloni-Pomarol relation, and there are light, weakly-coupled states in the spectrum. The production and cascade decay of superpartners at colliders occurs as in the MSSM, except that there is one extra stage of the cascade chain, with the next-to-LSP decaying to its "superpartner" and \tilde{s}, dramatically altering the collider signatures for supersymmetry. The framework is compatible with terrestrial experiments and astrophysical observations for a wide range of m_G and <s>. If G is as light as possible, 300 keV < m_G < 3 MeV, it can have interesting effects on the radiation energy density during the cosmological eras of nucleosynthesis and acoustic oscillation, leading to predictions for N_{νBBN} and N_{νCMB} different from 3.

Paper Structure

This paper contains 27 sections, 64 equations, 2 figures, 1 table.

Table of Contents

  1. Introduction
  2. Theoretical Framework
  3. The Higgs Sector
  4. The Higgs Potential
  5. A Large Singlet vev
  6. An Effective $\mu$ Parameter
  7. The Scalar Spectrum and Mixing
  8. The Fermion Spectrum
  9. Limits from LEP
  10. Other Terrestrial Limits
  11. Low-energy effective action of the Goldstone boson
  12. Rare decay of mesons
  13. Beam dump experiment
  14. Reactor experiments
  15. Astrophysical Limits
  16. ...and 12 more sections

Figures (2)

  • Figure 1: Various limits from terrestrial experiments are schematically described (coloured online). "bdmp-SLAC", "bdmp-KEK", and "bdmp-SIN" in the figure stand for the region excluded by the beam dump experiments at SLAC, KEK, and SIN, respectively, and "reactor $e^+ e^-$", and "reactor $np$" for that by the reactor experiments through the process $G \rightarrow e^+ + e^-$, and $G+d \rightarrow n + p$, respectively. The limit "bdmp-KEK" is taken from KEKbeam and "reactor $e^{+}e^{-}$" from Bugey. Note that the theoretical uncertainties are so large that details in this figure do not have importance. The limits from LEP experiments $F_G \mathop{}_{ \sim}^{ >}$ (a few TeV) is not shown in this figure. (The $m_G\hbox{--}F_G$ relation of the QCD axion is shown by a thick (red) line.)
  • Figure 2: Various limits from astrophysics (coloured online). The limits from the Sun (emission from the thermal plasma) and horizontal branch stars, HB in the figure, are taken from RStrCS with $m_G$ increased by 2.5 keV for the Sun and by 25 keV for the horizontal branch stars. The limit from red giants, RG in the figure, is taken from Raffelt-PRpt1. The limit from the Goldstone boson emitted from pp-chain nuclei does not take account of the possible decay $G \rightarrow \tilde{\chi}^0_0\tilde{\chi}^0_0$. The limit from SN 1987A for $m_G \mathop{}_{ \sim}^{ >} 1 \; {\rm MeV}$ requires numerical analysis. c.f. MT.