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RE: Particle physics @ Utopian - Implementing an LHC analysis on a computer: the physics objects
I'm having a little trouble interpreting the 4th column matching criterion. Specifically, the term in the denominator.
I'm pretty confident that the first term is just the momentum of the lepton being compared, but what screws me up is the division by GeV. Is this just to remove units?
In particle physics, the system of unit is the following
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.