What is a GeV/beam? What is 45.6GeV/beam for 1 electron only

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Discussion Overview

The discussion centers around the concept of energy per beam in the context of the L3 experiment and the LEP collider, specifically focusing on the meaning of "45.6 GeV/beam" for electrons and positrons. Participants explore the implications of this energy for individual particles and the associated mass changes, while also referencing the historical context of the collider's energy levels.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Historical

Main Points Raised

  • One participant seeks to understand the meaning of "per beam" in the context of the energy stated for the LEP collider.
  • Another participant suggests that "per beam" indicates that both the electron and positron beams have particles with energy of 45.6 GeV each.
  • A question arises about whether one electron possesses 45.6 GeV of energy, which is confirmed by another participant.
  • There is a discussion about the mass change of the electron, with one participant estimating it will not exceed +0.4% of the electron mass and providing a calculation related to the energy levels.
  • A participant provides historical context about the LEP collider's purpose and energy levels required for producing Z bosons and W bosons, noting the evolution of the collider's energy capabilities over time.
  • Another participant mentions the energy threshold needed for specific particle interactions, indicating a missed opportunity related to Higgs boson detection.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the energy per beam and the resulting mass changes, with no consensus reached on the exact interpretations or calculations presented.

Contextual Notes

The discussion includes assumptions about energy conversions and mass-energy relationships, but does not resolve the complexities involved in these calculations or the historical decisions regarding the LEP collider's operation.

applestrudle
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I'm doing an essay on L3 experiment and the LEP collider and the first energy the electrons and positrons had were "45.6GeV/beam". I want to convert this to the amount of energy for one electron/positron and see how much mass a single electron/positron gains.

I know 1GeV = 10^9 * 1.6 x 10^-19 J

and I know E = mc^2 +(pc)^2

and electron mass 9.11 x 10^-31kg but I need to know what the "per beam" bit means?!

Thank you
 
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applestrudle said:
I need to know what the "per beam" bit means?!

I think what they mean is that both beams (the beam of electrons and the beam of positrons) contain particles with energy 45.6 GeV.
 
Oh? So one electron has 45.6GeV of energy!?
 
Right.

(the alternative number is "per collision", 2*45.6 GeV)
 
The change of the mass won't exceed the +0.4% of m_e=511 keV
It should be approximately m_e^{1-loop} (46.5~GeV) \approx 512.6 ~keV
 
LEP was built to study W and Z physics in high precision. To create a Z boson in an ##e^+ e^-## collision you need at least the ##Z## mass of about 91 GeV. That's why at first they had a total collision energy around this value. So the electron and the positron each have a total energy (including rest energy) around half this value. Later it was upgraded to make even two W bosons (for which you need ##2 m_W \simeq 160 \mathrm{GeV}##). At the very end of its time in the year 2000 they pushed the cm. energy even up to around 210 GeV if I remember right, because there was some hint of a possible Higgs signal. They let LEP even run longer than planned for a while. Then Maiani had to make the difficult decision to stop it, because otherwise the construction of the LHC, using the LEP tunnnel, would have been delayed too much, and such an experiment to be delayed is very expensive!
 
They would have needed roughly 125+90=215 GeV (electron+positron->Z->Z+H) and missed it by about 10 GeV (the exclusion limit went up to 115 GeV).
 
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