Some data from ATLAS at the LHC

No, the Large Hadron Collider hasn’t vanished. It might not be so prominent in the news as it was two years ago, but it is quietly colliding protons together and generating lots of useful data for analysis.

Here’s a couple of bits which I gleaned in Melbourne

1. What lies inside a quark (if anything?).  Us physicists are happy with the notion that at the centre of an atom lies a nucleus, consisting of protons and neutrons, and each proton and neutron contains three quarks. (For the case of a proton, it’s two ‘up’ quarks and one ‘down’ quark; for the neutron its two ‘down’ quarks and one ‘up’. Protons and neutrons are actually very, very similar things.)  But is the quark made of anything? How could we tell? Basically, the way you do this is to collide protons together (i.e. 3 quarks on 3 quarks) and carefully analyze the statistics of the scattering. At what angles are the protons scattered? Is there fine-structure in the scattering pattern? This is exactly what Rutherford did with Geiger and Marsden’s alpha-particles on gold-foil results to determine that there must be a nucleus to an atom. In the case of the gold-foil, the structure in the pattern is pretty obvious. In the proton-proton case, it’s not. In fact, results from the ATLAS experiment at the LHC fail to indicate any structure at current energies (3.4 TeV).  (In particle physics, higher energies equate to probing smaller distances). So we can conclude that IF there is structure (and it’s a big if), it must appear at energy scales larger than 3.4 TeV. So far, the quark remains ‘fundamental’.

2. Can we find dark matter?  Dark matter is what is thought to make up 23% of the mass/energy of the universe. It has the annoying property that you can’t see it – in fact it doesn’t interact with any electromagnetic things. So why do we think it’s there?  If you study the way galaxies are moving, knowing what we know about gravity, we come to the conclusion that there simply isn’t enough visible mass in a galaxy to account for its movement. Galaxies seem to be more massive than we can account for by ‘counting’ stars in them. This missing mass is called ‘dark matter’.  (N.B. There’s also dark energy, that makes up about 73% of the universe, which is another thing, but I won’t go there today.) So, what is it? We don’t know, but there are theories. Moreover, these theories are testable – in that you can use them to make predictions about what might be observed in the LHC. So people are busy analysing results of collisions to see if there are features observed in the LHC that can only be explained by the theories of dark matter. If there are, that’s strong evidence for the ‘discovery’ of dark matter.  I have to say that listening to a couple of talks I was impressed at the size of the research effort on theories of dark matter – given that this stuff hasn’t actually been observed yet. It must take a bit of faith to spend your PhD studying something that might not even exist.

3 thoughts on “Some data from ATLAS at the LHC”

  • “It must take a bit of faith to spend your PhD studying something that might not even exist.”
    I should say since our esteemed scientists have been looking for the dark matter with underground detectors for the last 18 years and have not found it.
    Some scientist talk about the dark matter and the dark energy problem. They should not use this phrasing. They should rather say “extragalactic catastrophe.” Then our scientists might consider that something might be wrong with Newton’s and Einstein’s mass-based gravity theories.
    Why am I getting a ~10% increase in weight when I place a copper test mass above a 1000 W heat source and below a copper container filled with ice-water? It could not be that the transfer of infrared radiation is gravitationally attractive could it? If this were so that that would imply that starlight, sunlight and a planet’s heat is gravitationally attractive. Such a notion constitutes paradigm shift.
    But a paradigm shift is what should be expected if you have an “extragalactic catastrophe” that will not go away with the long-standing, venerated, gravity theories of Newton and Einstein. For those who think that the dark matter and dark energy are just like the aether go to:

  • Marcus Wilson says:

    Yes, dark matter and dark energy at the moment are simply suggestions as to what might be going on. The question of ‘how long do you have to look for something before you conclude it doesn’t exist?’ is always a vexed one in science. You might want to rephrase it – ‘if it did exist, what evidence would it leave behind?’ (or, more powerfully, what evidence would show that it DOESN’T exist? – e.g. if a theory implies that event A cannot happen, but we observe event A, that disproves the theory.) This is basically what the dark matter people are trying to do – e.g. by looking for jets of bottom and anti-bottom quarks in the ATLAS detector.
    The trouble with calling Einstein’s gravitational theory a ‘catastrophe’ is that it has been very well tested and works – at least in the vicinity of earth, where we have control of the experiments. For example, without accounting for general relativity our GPS system wouldn’t stay accurate – the fact that it does is evidence that our understanding of general relativity is good – at least for this application – i.e. no ‘catastrophe’ there. Contrast this with the ‘ultraviolet catastrophe’ of classical physics which predicted a spectrum for blackbody radiation that clearly did not correspond with what was observed.
    One could of course counter that, in the case of moving galaxies, general relativity doesn’t correspond to what is observed (we observe more gravitational force than there should be based on the mass we observe).
    So does dark matter exist? I don’t know. But once the LHC is up to its full energy one might be able to talk a bit more definitely.

  • I did not call Einstein’s theory a catastrophe. I said it would be better to call the dark matter and the dark energy problem as the “extragalactic catastrophe”. Einstein’s theory works great in all the places you mention. But does it work well when scientist were able to get above the atmosphere and see beyond the Milky Way. When this happened the flat rotation curves and cosmic acceleration were observed. Both Newton’s and Einstein’s theory fail beyond the Milky Way as bad as the classical theory failed to predict the blackbody spectrum. What our esteemed scientist have done to avoid this “catastrophe” is to invent these neo-aether entities called the dark matter and the dark energy where close to a billion dollars has been spent looking for these elusive concepts and delay the time when they are going to have to face the fact that Einstein’s and Newton’s theory do not work beyond the Milky Way. Once they or the public realize that a billion dollars have been wasted looking for these two kinds of fool’s gold they might want to look at my four experiments which cost $300. With these experiment I have observed a ~10% increase in weight when a test mass was placed above a 1000 W heat source and below a ice-water heat sink. Podkletnov got a ~2.% decrease in weight in a test mass that was hovered over a vat of liquid nitrogen ( I have gotten a 4.9% decrease in weight when I hovered a hollow copper sphere over a copper container filled with ice ( ). Podkletnov got all kinds of publicity for his experiment which most people think was due to the superconductor which was also in the vat. No one has paid any attention to my experiments because of they do not want to think of the simple embarrassing possibility that it is just the luminosity interchanged between stars, planets, galaxies and clusters that keeps these astrophysical bodies gravitationally bound.

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