Recent content by MarekS

If two protons collide at the LHC and a quark from each undergo a weak interaction together to form a W/Z boson, then what happens to the remnants of the protons? I think that if the weakly interacted quark was a sea quark, then the proton can continue being itself, but may lead to jets. If...

I am having difficulty parsing this sentence. "fraction of the proton's momentum" would imply the vertical axis wouldn't go above 1, but it does. Could you phrase it longer/differently? If I think of the proton as a sack of balls with the sack moving with a large momentum, then all the balls...

Is the purpose of plotting the product xf instead of f to compress the functions along the vertical direction? That is to say, f goes up for low x quite a bit, but the product xf increases less as one decreases x.

I am slightly confused by the labelling of the vertical axis on parton distribution function plots. Take the one here: http://www.hep.phy.cam.ac.uk/~wjs/partons2008nlo.jpg as an example. The vertical axis is labelled as xf(x, Q^2), where f is the probability density of finding a...

Yes, most definitely. Remember, the LHC collides proton bunches, not just protons. In addition, protons aren't elementary particles and contain many quarks and gluons. Therefore, it is common to have many collisions. Also, even two particle interactions will involve more particles as spectators...

These measurements are made by ATLAS and CMS and are updated as new data comes in. They are viewable free on ArXiv. Particle physics blogs are also a source of good information. How do you make a non-quantitative measurement?

Jep, that's what I meant.

Why not integrate all the decay probabilities from 0 to t, add them up and then subtract the resulting probability from 1 to find the probability of the particle surviving?

Yes, as long as conservation laws are obeyed. Vacuum has nonzero energy density.

Electron is a fermion with spin 1/2 which can't be altered. The orientation of spin can be "up" or "down" and this can be seen by an external electromagnetic force. It may be interesting to read about the Stern-Gerlach experiment: http://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach_experiment

Thanks! What you say makes sense to me. Except that the question why then is there a mass difference between D1 and D2 remains. ##D^0## and ##\overline{D^0}## have the same mass and p, q are normalised. What is causing the difference in the mass of the mass eigenstates?

The K0--K0-bar, D0--D0-bar, B0--B0-bar, Bs0--Bs0-bar systems all exhibit oscillations whose rate is proportional to their mass difference via a second order weak interaction "box" diagram. I don't understand how their masses can differ, when they are simply C conjugates of one another...

Two types of integrals that are coming up in electrodynamics that I don't know how to do: (1-a(1-x^2))^(-3/2) with x as the integration variable. And the related and more nasty: x*(x^2-a*x+b))^(-3/2) What is the formula for doing these? Thanks!

Never mind. I thought this through and I understand now. Thanks for your help.

I can't see why I can't have both. Also, I don't actually understand why a down-type quark is a linear superposition of down-type quarks when the interaction takes from a down-type quark to an up-type quark (and vice versa). I think it would make sense for an up-type quark to be a linear...