Minimal supersymmetric standard model (MSSM)

Definition

The minimal supersymmetric standard model (MSSM) is an extension of the Standard Model of particle physics that incorporates supersymmetry, a theoretical symmetry relating bosons and fermions. It introduces superpartners for each particle in the Standard Model and aims to resolve several issues like hierarchy problems and unification of forces, while being minimal in its structure by keeping the number of new parameters to a minimum.

5 Must Know Facts For Your Next Test

1. The MSSM includes two Higgs doublets, which leads to five physical Higgs bosons, instead of just one as in the Standard Model.
2. It predicts the existence of superpartners, such as squarks and sleptons, which are heavier counterparts of quarks and leptons, respectively.
3. The MSSM allows for the unification of the three gauge couplings at high energy scales, providing a more consistent picture of particle interactions.
4. One of the key motivations for MSSM is to address the hierarchy problem, particularly why gravity is so much weaker than other forces.
5. The model contains a wealth of new parameters, such as mass and mixing angles for superpartners, leading to rich phenomenology and predictions for experiments.

Review Questions

• How does the minimal supersymmetric standard model address the hierarchy problem?
  • The minimal supersymmetric standard model tackles the hierarchy problem by introducing superpartners for each particle in the Standard Model. These superpartners can cancel out radiative corrections to mass terms, which would otherwise lead to large mass discrepancies. This cancellation mechanism helps to stabilize the mass of the Higgs boson at low energy scales, thereby addressing why its mass remains relatively light compared to the Planck scale.
• Discuss the significance of introducing two Higgs doublets in the MSSM compared to the Standard Model.
  • In contrast to the Standard Model, which contains only one Higgs doublet, the MSSM introduces two Higgs doublets. This results in five physical Higgs bosons: two charged Higgs bosons and three neutral ones. The presence of multiple Higgs states not only helps in accommodating supersymmetry but also allows for richer dynamics regarding electroweak symmetry breaking and potential implications for phenomena such as dark matter candidates.
• Evaluate how R-parity plays a role in stabilizing the predictions made by the MSSM and its implications for particle searches.
  • R-parity is crucial in maintaining consistency within the minimal supersymmetric standard model by distinguishing between ordinary particles and their superpartners. It ensures that superpartner production processes lead to stable lightest supersymmetric particles (LSPs), often considered candidates for dark matter. This stabilization helps guide experimental searches for supersymmetric particles by predicting that LSPs will escape detection without decaying, leading to missing energy signatures in high-energy collisions.

Related terms

Supersymmetry: A theoretical framework that proposes a symmetry between bosons and fermions, suggesting that every known particle has a superpartner with different spin.

Higgs Boson: A fundamental particle associated with the Higgs field, responsible for giving mass to other particles through the Higgs mechanism.

R-parity: A multiplicative quantum number used in supersymmetric theories that distinguishes between ordinary particles and their superpartners, helping to conserve certain symmetries.