The positron was first discovered in cosmic ray debris. Some cosmic ray protons have millions of times the energy that the LHC can achieve. If supersymmetry particles exist, could they be created and detected in cosmic ray debris?


3 Answers 3


Discriminating between physics models needs accuracy in measurements. Accuracy means knowledge of four vectors of detected particles, the interaction vertex and the initial four vector of the impinging cosmic ray.

In the case of the discovery of the positron the signal of a new particle was simple, not needing a lot of energy or knowledge of four vectors:

While studying cosmic rays in a Wilson cloud chamber, the Soviet academic Dimitri Skobeltsyn noticed something unexpected among the tracks left by high-energy charged particles. Some particles would act like electrons but curve the opposite way in a magnetic field. In an independent experiment that same year, Caltech graduate student Chung-Yao Chao observed the same phenomenon. The results were inconclusive, and both scientists disregarded the anomaly.

The energies were low enough and all the cosmic ray flux could provide the luminocity.

Why was not the Higgs found in the cosmic ray TeV experiments? Because the accuracy for detecting the multiparticle decays would require enormous detectors with magnetic fields for momentum determination.

The Higgs to gamma gamma, the simplest decay of the Higgs is easily lost in a cosmic ray shower where no control can be had of the initial four vectors.

Have a look at the complexity of expected three decays of supersymmetric particles here to understand how the combination of "nocontrol of initial four vectors", need of " huge detectors" and complexity in the number of generated particels make it highly improbable to detect new resonances in cosmic ray showers.


The problem is that the energy of the cosmic ray itself is effectively irrelevant for producing SUSY particles. What is needed is a large center of mass energy, as that is all that is available for particle creation- the rest necessarily goes into the kinetic energy of the created particles.

To produce a SUSY particle, a cosmic ray would need to interact with a particle in our atmosphere. Since particles in our atmosphere are approximately at rest in the earth's frame, we can compute the center of mass energy $\sqrt{s}$ of a particle of mass $m$ in our atmosphere interacting with a cosmic ray of energy $E$ as:

$$ \sqrt{s}=\sqrt{2mE} $$

Or, solving this for the energy required to achieve a given $\sqrt{s}$: $$ E=\frac{s}{2m}$$

To compete with the LHC, this energy needs to be larger than what the LHC can achieve. So $\sqrt{s} \gt 13~\rm TeV$. The best we can do for $m$ is a proton or a neutron. Plugging those numbers in gives:

$$ E \gt 90~\rm PeV$$

So, to produce particles that the LHC cannot requires cosmic rays of approximately $100~\rm PeV$ or more. Looking at the graph of cosmic ray frequencies posted on @Nikl's answer, these cosmic rays are extraordinarily rare. Furthermore, even if SUSY was produced, it would be expected to occur at very low cross sections. We're talking like a one in $10^{15}$ sort of event.

Note that even the highest energy cosmic rays ever seen (on the order of ten joules) still have less than a hundred times the center of mass energy of the LHC when they collide with a proton at rest.


Theoretically the high Energy of some of the cosmic particles would suffice to create superpartners of SM-particles (if they exist and are in the energy range).

The problem I see here is the detection. We mainly look for supersymmetry by comparing our measured created particles to the current model (Standard Model). If our model is missing any particles then we should see discrepancies between measurement and prediction. To be certain about such a discrepancy we need very good statistics, meaning many events (Luminosity).

For the high energy cosmic rays there would't be enough events (even in a large detector) to look for new particles. Our current Standard Model fits pretty well.

LHC operates at several TeV. Looking at the graph below you will see that at that energy range there is only around one cosmic ray event of that energy per sqare meter and hour.

Cosmic ray flux versus particle energy

Cosmic ray flux versus particle energy (from: wikipedia)

  • $\begingroup$ Since May 2011, AMS has collected data from more than 90 billion cosmic rays with up to multi-TeV energies That's a lot of data.. So is detection still the problem, or is that we are looking for primarily matter related events, or is it that supersymmetry is now a more tentative idea than previously thought? I genuinely don't know, I don't have the background to assess the AMS results, but I wonder is this a confirmation of the LHC negative results. ams02.org/2016/12/… $\endgroup$
    – user163104
    Jul 30, 2017 at 21:13
  • 2
    $\begingroup$ @count Look at the graph. The "multi-TeV" flux is surpressed by a factor of roughly $10^9$ relative GeV events. (Log scales can be deceptive until you get used to them.) Ninety billion cosmic rays mean doesn't necessarily mean a lot at LHC energies. $\endgroup$ Jul 31, 2017 at 2:31

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