What is the problem with the particle masses in the Standard Model?

In summary, the conversation discusses the argument about a "problem" with the masses in the Standard Model and the confusion surrounding it. The concern about the smallness of neutrino masses is reasonable, but for the rest of the particles, there is no clear understanding. Some theories suggest a possible connection between the masses, while others argue for the simplicity and beauty of a single governing value. However, there is no fundamental issue with different fermions having different masses. The pattern of fermion Yukawa values is not random, with some values being significantly smaller than others. This raises the question of whether there is a reason for this pattern that is currently not understood.
  • #1
ChrisVer
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TL;DR Summary
mass hierarchy, top quark mass, neutrino masses
Hi,
Several times I encounter the argument that there is a "problem" with the masses in the Standard Model that we try to "understand". From the one side, you have people who ask why the neutrino masses are so small, and from the other side they ask why the top quark mass is so large. The smallness of the neutrino mass sounds a reasonable concern (as there is no "known"/"verified" mechanism to give neutrinos masses without for example extending the SM with right handed neutrinos or assigning them a Majorana nature), but for the rest of the particles I am a little confused when I see this argument in use.

So I was wondering, how relevant is a concern about this? Or is it also an argument about having a beautiful single value that governs everything (similar to a GUT)? So, is it because there exist some theories can (somehow) connect the masses together? Or is there something fundamentally suspicious about having a large gap of available masses?

Because, at least in the scope of the SM, if we say that the (bare) masses enter as free parameters, I don't understand what stops them from taking any value. Also, to my understanding, there is no problem associated with fermions having different masses (as for example with the mass of the scalar field like the Higgs which brings about the "hierarchy problem"). They are distinct particles, known for not being excitations of each other (a muon is not an excited electron), nor composite particles (as for example the nuclei or the atoms).
 
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  • #2
Suppose the fermion Yukawas are just random numbers between 0 and 1. The pattern we see does not look like these random numbers are drawn from a U(0,1). One number is bang up against 1, and 11 are all below 0.03. Ten are below 0.01. Nine are below 0.001. Three are below 10-12.

Given this, which seems more likely?
A. There is no reason for this.
B. There is a reason for this that we don't understand.
 
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FAQ: What is the problem with the particle masses in the Standard Model?

What is the problem with the particle masses in the Standard Model?

The Standard Model is a theory that describes the fundamental particles and their interactions. However, it has some limitations and one of the main problems is the issue of particle masses.

What is the significance of particle masses in the Standard Model?

Particle masses play a crucial role in the Standard Model as they determine the strength of the fundamental forces and the stability of atoms. They also provide insight into the structure of matter and the nature of the universe.

Why are the masses of particles in the Standard Model unequal?

The Standard Model predicts that particles should have equal masses, but in reality, they have vastly different masses. This is known as the "hierarchy problem" and it is one of the major challenges in particle physics.

How does the Higgs mechanism attempt to solve the problem of particle masses in the Standard Model?

The Higgs mechanism is a proposed solution to the hierarchy problem in the Standard Model. It introduces a new particle, the Higgs boson, which gives mass to other particles through a process called electroweak symmetry breaking.

What are some current theories and research being done to address the issue of particle masses in the Standard Model?

Scientists are currently conducting experiments at the Large Hadron Collider to study the properties of the Higgs boson and search for new particles that could help explain the unequal masses in the Standard Model. They are also exploring alternative theories, such as supersymmetry and extra dimensions, which could provide a more comprehensive explanation for particle masses.

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