Understanding Supersymmetry and Symmetry Breaking in the Higgs Sector

In summary, the conversation discusses the concept of symmetry breaking in supersymmetry (SuSy) and the role of two Higgs doublets in this process. The first Higgs doublet breaks SuSy at high energy scale, while the second one breaks the electroweak symmetry at a lower scale. The need for two doublets is explained by the need for anomaly cancellation and the coupling of Higgses and Higgsinos with particles/sparticles.
  • #1
Safinaz
259
8
Hi guys,

I have a question about symmetry breaking in Susy, I hope it won't be so naive that I just started to study supersymmetry ..

The question is that there are two Higgs doublets in Susy, H_u and H_d, how these two doublets first break supersymmetry at high energy scale and then make electroweak symmetry breaking at MZ scale ? It is not possible to take VeV. twice ..

I think the scale of Susy breakings is higher because Susy particles are heavier than their SM
partner so they have not found yet ..

I saw the equations where H_u and H_d couple to Susy particles like sleptons and squarks and where they couple to SM particles .. so what's happen ?


Bests,
S.S.
 
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  • #2
The reason you need two Higgs doublets in MSSM is to break the electroweak symmetry, and not SuSy. What breaks SuSy is still an unclear topic, and a very complicated one. At first someone, in order to break SuSy, introduces some soft breaking terms in the scalar potential which then lead to SuSy SSB. These soft terms may come from a hidden sector which is somehow mediated to MSSM and causes its breakdown, and the reason it's unclear is because there are many suggestions about this Hidden Sector mediation, for example:
1. gravity (Sugra)
2. Gauge
3. Anomaly
The reason you need a 2nd Higgs doublet is for an anomaly cancelation occurring due to the 1st field's higgsino (fermion with Y=-1/2)
I don't understand the other question about their coupling, what's the point? In general you can allow Yukawa terms in the superpotential, which give those couplings of Higgses and Higgsinos with particles/sparticles.
 
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  • #3
The second higgs doublet is needed to have a lamda term to your Higgs potential. Your superpotential due to renormalizability cannot accept a term like [itex]H_{u,d}^{4}[/itex] for example

I believe This not true. Event with one doublet, you would get quartic terms in your Lagrangian as in the SM from the D term scalar potential part.

The reason two doublet are needed is twofold.

1) It is not possible to couple a single Higgs doublet to the up and down type quarks in a supersymmetric way, and thus give masses to all quarks. Two doublets are needed.

2) Higgs doublets also have their fermionic partners, which are chiral in this case. They contribute to dangerous gauge anomalies and two are needed with opposite hypercharge for these to cancel.
 
  • #4
Yes ofirg, that was not true, that's why I corrected it. Fortunately the OP was still offline before the corrections :)
 

1. What is SUSY and how does it relate to symmetry breaking?

SUSY, or supersymmetry, is a theoretical concept in physics that proposes the existence of a new type of symmetry between particles. This symmetry would relate bosons (particles with integer spin) to fermions (particles with half-integer spin) and could potentially explain some of the unanswered questions in particle physics, such as the origin of dark matter. Symmetry breaking is a process by which a system with certain symmetries ends up in a state with lower symmetries. SUSY and symmetry breaking are closely related because SUSY predicts that the breaking of this symmetry could have occurred during the early stages of the universe, leading to the formation of the known particles and their properties.

2. How is SUSY tested and what are the current results?

SUSY has not yet been directly observed, but scientists are conducting experiments to search for evidence of its existence. These experiments involve high-energy particle colliders, such as the Large Hadron Collider, and the search for specific patterns in particle interactions. So far, no conclusive evidence of SUSY has been found, but the search is ongoing and new theories and experiments are being developed to test its validity.

3. What are the potential implications of SUSY for our understanding of the universe?

If SUSY is proven to be a valid concept, it could have major implications for our understanding of the universe. It could help explain the hierarchy problem, which is the large discrepancy between the predicted mass of the Higgs boson and its observed mass. SUSY could also provide a possible explanation for dark matter, which makes up about 85% of the matter in the universe but has not yet been directly detected. Additionally, it could offer insights into the unification of the fundamental forces of nature.

4. What are some of the challenges and criticisms of SUSY?

One of the main challenges and criticisms of SUSY is the lack of experimental evidence to support it. Many proposed SUSY particles have not yet been observed, and some of the predictions of SUSY have not been confirmed by experiments. Another criticism is that SUSY requires a large number of new particles, making it a more complex theory that may be difficult to test. Additionally, SUSY has not yet been fully integrated into the Standard Model of particle physics, which is the current framework for understanding the fundamental particles and forces in the universe.

5. Are there any alternative theories to SUSY and symmetry breaking?

Yes, there are several alternative theories to SUSY and symmetry breaking. Some of these include extra-dimensional theories, such as string theory, which propose the existence of additional dimensions beyond the three spatial dimensions we are familiar with. Another alternative is the composite Higgs model, which suggests that the Higgs boson is not a fundamental particle but is made up of smaller particles. These alternative theories are still being explored and tested, and it is possible that a combination of different theories may be needed to fully explain the mysteries of the universe.

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