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

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

jtbell
Mentor
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!?

mfb
Mentor
Right.

(the alternative number is "per collision", 2*45.6 GeV)

ChrisVer
Gold Member
The change of the mass won't exceed the +0.4% of $m_e=511 keV$
It should be approximately $m_e^{1-loop} (46.5~GeV) \approx 512.6 ~keV$

vanhees71