How Close to Light Speed Do Protons Move in the LHC?

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Homework Help Overview

The discussion revolves around the speeds of protons in the Large Hadron Collider (LHC) and involves concepts from relativistic physics. The original poster seeks to determine how fast protons are moving relative to the speed of light, given a center-of-mass energy of 14 TeV.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between energy and speed using relativistic equations. There are attempts to calculate the speed of protons and their relative velocities using the velocity addition formula. Some participants question the assumptions made regarding the momentum and energy of the protons.

Discussion Status

There is ongoing exploration of the calculations involved, with some participants providing guidance on simplifying expressions. Multiple interpretations of the calculations are being discussed, particularly regarding the treatment of small quantities and the implications of sign errors in the equations.

Contextual Notes

Participants note potential issues with the accuracy of calculations and the need to consider higher-order terms in expansions. There is also mention of a typo regarding units, which highlights the importance of careful attention to detail in mathematical expressions.

  • #31
PeroK said:
n the first method you used the approximation 1−ϵ1−ϵ1-\epsilon in the calculations for part b) and dropped the term in ϵ2ϵ2\epsilon^2 (which wasn't needed for part a). If you put that term back in, you should get the same answer as in the second method.
This was never an issue. The relation ##v=c(1-\epsilon)## from (a) is what defines ##\epsilon## and it is therefore exact. He only needs to keep terms to order ##\epsilon^2## when adding the velocities, which he did.
 
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  • #32
Orodruin said:
This was never an issue. The relation ##v=c(1-\epsilon)## from (a) is what defines ##\epsilon## and it is therefore exact. He only needs to keep terms to order ##\epsilon^2## when adding the velocities, which he did.

I thought the same.
 
  • #33
PeroK said:
Which is the order of ##\epsilon^2##.

In the first method you used the approximation ##1-\epsilon## in the calculations for part b) and dropped the term in ##\epsilon^2## (which wasn't needed for part a). If you put that term back in, you should get the same answer as in the second method.

Ignored this comment.

PeroK said:
You may also want to check that value for ##\epsilon##. Shouldn't it be approx ##10^{-8}##?

Showed the equivalence of the two approaches using this piece of advice.
 
  • #34
Thanks so much to vela, Orodruin and PeroK for helping me out with this problem with your suggestions and problem-solving tips!

I've learned a lot from solving just this one single problem. :smile:
 

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