Understanding Critical Energy and Thresholds in High Energy Physics

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Discussion Overview

The discussion revolves around the concept of critical energy and thresholds in high energy physics (HEP) versus low energy physics. Participants explore whether there is a definitive threshold energy that separates these two domains and how such distinctions might be defined or understood within the context of relativistic effects and experimental observations.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • One participant questions the existence of a critical energy threshold, suggesting that the effects of special relativity (SR) depend more on the experimental context than on specific energy levels.
  • Another participant argues that any proposed threshold energy would be arbitrary and questions the relevance of such a distinction.
  • There is a discussion about the relationship between high energy physics and condensed matter physics, with some suggesting that knowledge in both areas is interconnected and that categorization may not be meaningful.
  • Participants express skepticism about the utility of defining clear boundaries between high and low energy physics, likening it to arbitrary distinctions in other contexts, such as the size of ponds and lakes.
  • One participant notes that relativistic formulas can approximate Newtonian mechanics, implying that the distinction may not be as clear-cut as it seems.
  • Another participant mentions the historical term "elastic scattering" as a reference to energy levels that do not result in particle breakage, hinting at traditional categorizations in physics.

Areas of Agreement / Disagreement

Participants generally do not agree on the existence of a clear distinction between high and low energy physics. Multiple competing views remain regarding the significance and definition of critical energy thresholds.

Contextual Notes

Participants express uncertainty about the definitions of energy thresholds and the implications of relativistic effects, indicating that the discussion is influenced by subjective interpretations and the context of specific experiments.

Who May Find This Useful

This discussion may be of interest to those studying high energy physics, condensed matter physics, or anyone exploring the conceptual boundaries and definitions within the field of physics.

MathematicalPhysicist
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I believe that once I asked for what is the critical speed that above it it's considered ultra-relativistic speed and below it slow speeds.
I forgot to ask about the critical energy, what is the threshold energy that below it it's considered low energy physics and above it it's considered HEP, is there such an energy? in that case how to compute it?

I would assume one needs to use the equation ##E^2=p^2+m^2##, but which momentum and mass to insert?

Is this distinction between high energies and low energies really have a threshold?
 
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MathematicalPhysicist said:
Is this distinction between high energies and low energies really have a threshold?
No. The reason is that detecting the effects of SR would depend more on the actual experiment that the velocity involved. Take a high quality Frequency Standard with you on a trip round the Earth in a fast jet and you will detect a relativistic shift. Check the pilot's watch against the watch of his brother, who remains at the airport, and you will see no (measurable) relativistic shift.
Any "threshold" energy would be totally arbitrary. But why would that matter at all?
 
sophiecentaur said:
No. The reason is that detecting the effects of SR would depend more on the actual experiment that the velocity involved. Take a high quality Frequency Standard with you on a trip round the Earth in a fast jet and you will detect a relativistic shift. Check the pilot's watch against the watch of his brother, who remains at the airport, and you will see no (measurable) relativistic shift.
Any "threshold" energy would be totally arbitrary. But why would that matter at all?
Then why is there such a distinction between HEP and Condensed Matter Physics?
I mean HEP= High Energy Physics so there's also low energy physics I guess, so where's the critical energy at?
 
MathematicalPhysicist said:
Then why is there such a distinction between HEP and Condensed Matter Physics?
Is there "such a distinction"? How slow is the slowest 'fast car' on the road and how low is the lowest mountain that gets climbed?
Research departments have names which give a clue about what is studied but the names are not exclusive. Knowledge about condensed matter is needed in a High Energy Physics lab and you can bet that there will be a high energy specialist working somewhere in a Condensed Matter Physics if measurements involve high energy radiation.
I'd advise not wasting time on categorising. It's the least interesting part of Science, imo.
 
Where do you draw the line between the largest pond and the smallest lake?
 
This is heading in the direction of Zen, I think.:wink:
 
But what is the dividing line between Zen and other forms of Buddhism?

More helpfully for the OP, you can usally approximate relativistic formulae and recover Newtonian ones (e.g. relativistic K.E. is ##(\gamma-1)mc^2=mv^2/2+O(v^4/c^2)##). If the neglected parts are significant to whatever precision you are measuring, you shouldn't neglect them and should consider a full-fledged relativistic treatment.
 
Vanadium 50 said:
Where do you draw the line between the largest pond and the smallest lake?
If you are an estate agent (realtor?) there can be a large overlap. The seller's lake could be a buyer's pond.
 
Vanadium 50 said:
Where do you draw the line between the largest pond and the smallest lake?
So there's no difference between high and low energies? it's just a convention.
A condensed matter physicist can work in HEP and vice versa, since there's no difference.
I mean we have particles in both of them... :-)
 
  • #10
There is the old-fashioned term "elastic scattering" which meant not enough energy to break anything.
 
  • #11
MathematicalPhysicist said:
So there's no difference between high and low energies?

So there's no difference between ponds and lakes?
 
  • #12
MathematicalPhysicist said:
So there's no difference between high and low energies? it's just a convention.
A condensed matter physicist can work in HEP and vice versa, since there's no difference.
I mean we have particles in both of them... :-)
I'm really not sure what you want out of this thread. You are treating Physics a bit like Top Trumps.
 
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