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But cosmic rays that collide with atoms in the upper atmosphere have been measured with collision energies about ten times as high. The two types of observations complement each other. At the LHC, energies are smaller, but collisions happen in a closely controlled experimental environment, directly surrounded by detectors.

General Relativity 4: Astrophysics & Cosmology (Everyone's Guide Series Book 25)

This is not the case for cosmic rays — their collisions reach higher energies, but the experimental uncertainties are higher. Recent results from the Pierre Auger Cosmic Ray observatory at center-of-mass energies of approximately TeV are incompatible with the Standard Model of particle physics and hint at unexplained new phenomena. The statistical significance is not high, currently at 2. This is approximately a one-in probability to be due to random fluctuations.

Cosmic rays are created either by protons or light atomic nuclei which come from outer space. These particles are accelerated in galactic magnetic fields, though the exact way how their get their high speeds is often unknown.

When they enter the atmosphere of planet Earth, they sooner or later hit an air molecule. This destroys the initial particle and creates a primary shower of new particles. This shower has an electromagnetic part and a part of quarks and gluons that quickly form bound states known as hadrons. These particles undergo further decays and collisions, leading to a secondary shower. The particles of the secondary shower can be detected on Earth in large detector arrays like Pierre Auger , which is located in Argentina.

Pierre Auger has two types of detectors: 1 detectors that directly collect the particles which make it to the ground, and 2 fluorescence detectors which captures the light emitted from the ionization air molecules. The hadronic component of the shower is dominated by pions, which are the lightest mesons and composed of a quark and an anti-quark. The neutral pions decay quickly, mostly into photons; the charged pions create muons which make it into the ground-based detectors.

It has been known for several years that the muon signal seems too large compared to the electromagnetic signal — the balance between them is off. In the new paper — just published in PRL — the Pierre Auger collaboration used a different analysis method for the data, one that does not depend on the total energy calibration.

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They individually fit the results of detected showers by comparing them to computer-simulated events. From a previously generated sample, they pick the simulated event that best matches the fluorescence result. Then they add two parameters to also fit the hadronic result: The one parameter adjusts the energy calibration of the fluorescence signal, the other rescales the number of particles in the hadronic component. Then they look for the best-fit values and find that these are systematically off the standard model prediction. As an aside, their analysis also shows that the energy does not need to be recalibrated.

The main reason for the mismatch with the standard model predictions is that the detectors measure more muons than expected. Nobody knows, but the origin of the mystery seems not in the muons themselves, but in the pions from whose decay they come. Since the neutral pions have a very short lifetime and decay almost immediately into photons, essentially all energy that goes into neutral pions is lost for the production of muons. Besides the neutral pions there are two charged pions and the more energy is left for these and other hadrons, the more muons are produced in the end.

So the result by Pierre Auger indicates that the total energy in neutral pions is smaller than what the present simulations predict.

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One possible explanation for this, which has been proposed by Farrar and Allen , is that we misunderstand chiral symmetry breaking. It is the breaking of chiral symmetry that accounts for the biggest part of the masses of nucleons not the Higgs! The pions are the pseudo Goldstone bosons of that broken symmetry, which is why they are so light and ultimately why they are produced so abundantly.

The chiral phase transition is believed to be close by the confinement transition, that being the transition from a medium of quarks and gluons to color-neutral hadrons. For all we know, it takes place at a temperature of approximately MeV. Chiral symmetry restoration almost certainly plays a role in the cosmic ray collisions, and a more important role than it does at the LHC. So, quite possibly this is the culprit here. But it might be something more exotic, new short-lived particles that become important at high energies and which make interaction probabilities deviate from the standard model extrapolation.

Our accelerators would then be as good as the heavens. Saturday, December 10, Away Note. I'll be in Munich next week, attending a workshop at the Center for Advanced Studies on the topic " Reasoning in Physics. I take that to mean I'm hitting a nerve ;. Thursday, December 08, No, physicists have no fear of math.

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But they should have more respect. Heart curve. This, I thought, is ridiculous. But the headline was supposedly based on scientific research. Someone, somewhere, had written a paper claiming that physicists are more likely to cite papers which are light on math. So, I put aside my confirmation bias and read the paper. It was more interesting than expected.

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Instead, it was a reply to a comment on an analysis of an earlier paper which had claimed that biologists are afraid of math. They analyzed a sample of papers published in the top journals in ecology and evolution and looked for a correlation between the density of equations equations per text and the number of citations. They found a statistically significant negative correlation: Papers with a higher density of equations were less cited.

Unexpectedly, a group of physicists came to the defense of biologists. With these methods, the authors claimed, you could show anything, even that physicists are afraid of math. Which is surely absurd. They argued that Fawcett and Higginson had arrived at a wrong conclusion because they had sorted their data into peculiar and seemingly arbitrarily chosen bins.

The chance that you find a correlation with any one binning is much higher than the chance that you find it with one particular binning. Therefore, you can easily screw over measures of statistical significance if you allow a search for a correlation with different binnings. As example, Kollmer at al used a sample of papers from Physical Review Letters PRL and showed that, with the bins used by Fawcett and Higginson, physicists too could be said to be afraid of math. Alas, the correlation goes away with a finer binning and hence is meaningless. PRL, for those not familiar with it, is one of the most highly ranked journals in physics generally.

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It publishes papers from all subfields that are of broad interest to the community. PRL also has a strictly enforced page limit: You have to squeeze everything on four pages — an imo completely idiotic policy that more often than not means the authors have to publish a longer, comprehensible, paper elsewhere. The paper that now made headline is a reply by the authors of the original study to the physicists who criticized it.

They point out that the citation rates have a pronounced rich-get-richer trend which amplifies any initial differences. In that case, a more complicated statistical analysis is necessary, which is the type of analysis they had done in the original paper.

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The arbitrarily seeming bins were just chosen to visualize the results, they write, but their finding is independent of that. Fawcett and Higginson then repeated the same analysis on the physics papers and revealed a clear trend: Physicists too are more likely to cite papers with a smaller density of equations! A paper with fewer verbal explanations per equation assumes the reader is more familiar with the particular formalism being used, and this means the target audience shrinks.

The consequence is fewer citations. These citation habits therefore show mostly that the more specialized a paper, the fewer people will read it.