Is the Graviton Too Elusive for Particle Physicists to Find at the LHC?

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In summary, the graviton is believed to be too difficult to find, but if it is ever found, it will be a big deal for the Physics world.
  • #1
joeyb9
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Why is there seemingly so little interest among particle physicists about discovering the graviton? Is it because it is believed to be too difficult, even hopeless, to find, or some other reason?
 
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  • #2
I think its because the graviton comes from the General Relativity world and theories trying to bridge between Quantum Mechanics and General Relativity are still too tenuous that it isn't seriously looked for.

Also, once gravity waves are found then they will dig deeper.

http://en.wikipedia.org/wiki/Graviton

but I'm sure if they ever do find a spin-2 massless particle there will be a lot of excitement in the Physics world...
 
  • #3
joeyb9 said:
Why is there seemingly so little interest among particle physicists about discovering the graviton? Is it because it is believed to be too difficult, even hopeless, to find, or some other reason?

Detecting gravitons experimentally is hopelessly infeasible, because they pass through everything with very high probability. This is similar to the problem of detecting neutrinos, but many many orders of magnitude worse. See e.g. http://arxiv.org/pdf/gr-qc/0601043v3.pdf
 
  • #4
The graviton Lagrangian is very roughly
[tex] L = \frac{1}{2G_N} |\nabla h|^2 - h \cdot T [/tex]
for Newtonian gravitational constant GN, metric perturbation h, and energy-momentum tensor T. Going over to quantum-mechanical units,
[tex] G_N = \frac{1}{m_{Pl}{}^2} [/tex]
where mPl is the Planck mass.

Let's rescale h by multiplying it by the Planck mass:
[tex] h = \frac{1}{m_{Pl}}{\tilde h} [/tex]
That makes the Lagrangian
[tex] L = \frac12 |\nabla {\tilde h}|^2 - \frac{1}{m_{Pl}}{\tilde h} \cdot T [/tex]

That makes interaction matrix elements proportional to the reciprocal of the Planck mass, and total process rates proportional to the reciprocal of the square of it. So,
[tex] \text{(process rate)} \sim \text{("normal" process rate)} \left( \frac{E}{m_{Pl}} \right)^2 [/tex]

At the LHC's energies of about 1 TeV/parton, that's about 10-32. Thus, it will be VERY difficult to see evidence of individual gravitons at the LHC, as opposed to macroscopic, classical-limit gravity.
 
  • #5
The "normal" graviton will be impossible to find with the LHC, but some models (in particular, models with extra dimensions) predict massive graviton-like particles that could be detectable.
CERN made a webpage for it, and searching for "graviton LHC" gives several publications about it.
 

1. What is a graviton?

A graviton is a hypothetical particle that is believed to be the carrier of the force of gravity.

2. How does the existence of a graviton affect our understanding of gravity?

If the graviton is proven to exist, it would confirm the theory of quantum gravity and provide a more complete understanding of how gravity works at a subatomic level.

3. Can the existence of a graviton be proven?

Currently, there is no experimental evidence for the existence of a graviton. However, many scientists are working on theories and experiments to try and detect this elusive particle.

4. What implications would the discovery of a graviton have on modern physics?

The discovery of a graviton would have significant implications on our understanding of the fundamental forces of nature and could potentially lead to the unification of all the forces in the universe.

5. Is the graviton the only possible explanation for the force of gravity?

No, there are other theories and explanations for the force of gravity, such as Einstein's theory of general relativity. The existence of a graviton is currently just one of many proposed explanations for gravity.

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