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RE: Particle physics @ Utopian - Implementing an LHC analysis on a computer: the physics objects
In particle physics, the system of unit is the following
- the speed of light = 1
- the Planck constant =1
Under these conditions, a momentum is expressed in energy units. GeV is one of those (and very appropriate for LHC physics). The fraction pT / GeV means that the numerical value to be used for the pT has to be given in GeV units. By default, madanalysis 5 returns the pT in GeV.
In short: you can ignore the GeV. I just leads to a dimensionless quantity (an angular distance is dimensionless). Does it clarify?
Definitely clarifies. We do similar dimension removal for a bunch of fluid dynamics stuff, but I'm not used to the convention of putting the units into the equation like that. Glad to see my intuition was good.
A goods choice of units is always healthy to make our lives easier :)
I can't help but feel that 'unis' is a bit of a Freudian slip.
Although it's not dimensionless, my favorite is how we civil engineers often refer to pressure in units of 'head'. Literally, the height of a water column per unit area. (Analogous in concept to mm Hg) A very handy unit when you're concerned with lifting fluids/making sure they flow well after friction losses.
The typo is fixed :D
What is the atmospheric pressure in terms of heads? 10 or something?
I actually do not know off the top of my head. We often work in 'gauge pressure', setting 1 atm as the 0 point. The trivial answer I guess, is 0. Looking up the answer, it's a little over 10 1/3 m.
that is a big head :D
In hindsight, I should've known this both because it's the same as the limit for sucking water up a tube in a vacuum (at 1 atm) and the rule of thumb that pressure increases by 1 atm every 10 m.
This is why I actually suggested 10 in the very beginning. This being said, the next episode is finally out :D