If Higgs has mass of 125GeV why did the LHC need 3.5TeV?

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Discussion Overview

The discussion revolves around the question of why the Large Hadron Collider (LHC) operated at 3.5 TeV energy levels to discover the Higgs boson, which has a mass of 125 GeV. Participants explore the relationship between collider energy and the likelihood of producing and detecting the Higgs particle, considering both theoretical and practical aspects of particle collisions.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions the necessity of the LHC's high energy, suggesting a misunderstanding of the relationship between the Higgs mass and collider energy.
  • Another participant explains that the 3.5 TeV energy refers to the protons' collision energy, but partons within the protons carry only a fraction of this energy, making Higgs production less likely.
  • A subsequent reply confirms that while it is technically possible to produce the Higgs at lower energies, it is highly improbable due to the nature of particle collisions and the dominance of other particle production.
  • Further, a participant notes that higher energy increases the probability of collisions resulting in Higgs production.
  • Another participant mentions that a different collider, the Tevatron, could have potentially found the Higgs in a specific decay mode, but would have required an impractically long operational time to do so.

Areas of Agreement / Disagreement

Participants generally agree that while it is theoretically possible to find the Higgs at lower energies, the likelihood is very low, and the discussion reflects a mix of understanding and uncertainty regarding the practical implications of collider energy levels.

Contextual Notes

The discussion highlights the complexities of parton energy distribution within protons and the challenges of detecting rare events amidst numerous other particle collisions, without resolving the specifics of energy thresholds or detection methods.

SheriffPeabody
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Hi, I've tried to find an answer to this question, sorry if it's already been asked. I'm sure I have misunderstood something important here, but if the Higgs was found to have a mass of 125GeV, why did we need such a powerful collider to find it? (I think the LHC was running at 3.5TeV when they found the Higgs particle)

I'm guessing there's more to it than just power, but I'm wondering why it wasn't possible to have found the Higgs at a different lower powered collider?
 
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The 3.5 TeV was the energy of the protons being collided. The partons inside the proton (quarks and gluons) only carry a fraction of this energy. At 3.5 TeV, you would need to get very lucky to find a parton collision where the partons each carry a large part of the energy. It is much more likely to have a collision where the partons carry only a fraction of the total energy.
 
Ah right so it's technically possible to find it at lower energy collisions, but just incredibly unlikely?
 
It is technically possible to produce it at lower energy, just incredibly unlikely. Finding it is even more challenging, because most collisions produce other particles and you have to find the few events with Higgs in them. I wrote an insights article about this.
A higher energy increases the fraction of collisions with a Higgs.
 
It's a question of practicality. The Teavtron would have found the Higgs in the 2 photon mode (which is not the best mode for them) had they run long enough. However, "long enough" is 1600 years.
 

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