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God Plays Dice
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Does anyone know how close a photon needs to be to a nucleus (an ion really, no shielding from electrons) for pp to occur? I assume it's a probability as a function of distance, any ideas/equations?
Thanks
Thanks
Did you say pp on a bare nucleus with a photon? Good luck getting a photon of >2 GeV energy! and for the second part, charge conjugation occurs when the photon ( I seriously suggest a high-energy proton for this) enters the coulomb field of a nucleus (or another proton). The probability of pp increases with increasing energy from the threshold energy level, the equation that governs this : σ(pair E)≈αZ2r(electron)2InEγGod Plays Dice said:Does anyone know how close a photon needs to be to a nucleus (an ion really, no shielding from electrons) for pp to occur? I assume it's a probability as a function of distance, any ideas/equations?
Thanks
Photons are special since they are massless. There's a unique gauge invariant definition of total angular momentum only. The split into orbital and spin-angular momentum is arbitrary and gauge dependent and thus unphysical.snorkack said:Does a photon have a definable (and quantized) angular momentum of its translational angular momentum past a target?
Zypheros_Knight said:Good luck getting a photon of >2 GeV energy
What does "charge conjugation occurs" mean? Charge conjugation is a mathematical operation. When does "addition of two numbers" occur in collision processes?Zypheros_Knight said:and for the second part, charge conjugation occurs when the photon ( I seriously suggest a high-energy proton for this) enters the coulomb field of a nucleus (or another proton)
I would be surprised if that works for hadron production.Zypheros_Knight said:The probability of pp increases with increasing energy from the threshold energy level, the equation that governs this : σ(pair E)≈αZ2r(electron)2InEγ
Its okay , and yes the equation is for pair-production of electron which, if I remember distinctly ,I mentioned in the equation. And yes again I forgot to mention both the equations for Hadron pp and that charge conjugation operator changes the signs of all quantum charges (dammit). Nevertheless I will get better, I'm still in the process of healing.mfb said:I read "pp" as "pair production", not "proton antiproton", but it does not matter. Multi-GeV photons (and even a few photons with more than 1 TeV, see e.g. this recent ATLAS publication) are routinely produced at colliders like the LHC.What does "charge conjugation occurs" mean? Charge conjugation is a mathematical operation. When does "addition of two numbers" occur in collision processes?I would be surprised if that works for hadron production.
ATLAS public resultsZypheros_Knight said:Keep me posted on latest stuff like this!
mfb said:few photons with more than 1 TeV
Thank you very much! I've read about ALICE before, oh and have you read about AWAKE? Its a new method for accelerating charged particles!( I'm talking about Wakefield Acceleration).mfb said:ATLAS public results
CMS public results
https://lhcb.web.cern.ch/lhcb/Physics-Results/LHCb-Physics-Results.html
ALICE public results
hep-ex arXiv submissions
So, in a frame where angular momentum is defined with respect to the nucleus, you can define and measure:vanhees71 said:Photons are special since they are massless. There's a unique gauge invariant definition of total angular momentum only. The split into orbital and spin-angular momentum is arbitrary and gauge dependent and thus unphysical.
There are different complete one-photon bases. One is the momentum-helicity basis. These states are the usual plane-wave states of circular-left (##\lambda=-1##) and circular-right (##\lambda=+1##) polarization. Of course you could choose for each momentum any other polarization basis like linear polarized states etc.
You mean its possible for massless spin-## \frac 1 2 ## particles?vanhees71 said:(or any massless particle with spin ##\geq 1##).
Does the circular polarization of electromagnetic field depend on observer?vanhees71 said:There's no way to split the total angular momentum of the em. field into spin and orbital angular momentum. Only total angular momentum is well-defined and gauge invariant.
Yes, the circular polarization weather left-handed or right-handed will tell us about the directions of spin of a photon.snorkack said:So, if you have a photon whose circular polarization/helicity is known, do you also know its spin?
Pair production proximity is the process by which a particle and its antiparticle are created in close proximity to each other in space. This occurs when a high-energy photon interacts with a nucleus, creating a particle-antiparticle pair.
In quantum mechanics, pair production proximity is a manifestation of the principle of conservation of energy. The energy of the photon is converted into the mass of the particle and antiparticle pair.
Pair production proximity can create any type of elementary particle and its corresponding antiparticle. This includes electrons and positrons, as well as more massive particles like protons and antiprotons.
Pair production proximity has been studied extensively in particle accelerators and is important in understanding the fundamental interactions between particles. It also plays a role in astrophysics, explaining the production of high-energy particles in extreme environments such as black holes.
Unlike other forms of particle creation, such as radioactive decay or particle collisions, pair production proximity involves the creation of both a particle and its antiparticle simultaneously. It also occurs in the presence of a strong electromagnetic field, rather than through the decay of a larger particle.