As a result of today’s talks, here’s the updated body-count (all four experiments with a lot of overlap):
| Particle | Original discovery | Method of observation in the LHC experiments |
| Electron/positron | 1896 (e-), 1932 (e+) | Peak at 1.0 in calorimeter energy to track momentum ratio, also observed in pairs from photon conversions in matter (X γ → X e+e- where X is a nucleus) |
| Photon | 1900 (Planck’s quanta) | Photon conversions and π0→ γγ |
| Proton | 1911 | Energy loss charged particle’s trajectory (dE/dx) |
| Deuteron | 1931 | Also seen in dE/dx |
| Muon | 1936 | Specialized muon detectors |
| Pion | 1950 (π0) | Neutral pion in π0→ γγ, charged pions in dE/dx |
| Eta meson | 1961 | η → γγ |
| Kaon | 1947 (KS) | Neutral kaon in KS → π+π-, charged kaons (K+ and K-) in dE/dx and ring-imaging Cerenkov detectors |
| Phi meson | 1962 | φ → K+ K- |
| Lambda | 1947 (Λ0) | Λ0→ π+p- / Λ0→ π-p+ |
| Xi baryon | 1964 | Ξ → π Λ0 |
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| Dark matter WIMPs | not yet | two candidates in the unblinded signal region of the Cryogenic Dark Matter Search (CDMS) (not an LHC experiment) |
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The last entry is for yesterday’s CDMS paper, which shows two candidate events surviving all analysis cuts, set prior to looking at the result (unblinding). The probability for background fluctuating up to account for these two events is 20-23%, so no one is calling it a signal. Both are close to the edges of the analysis cuts, so even if the observed events had significantly exceeded the background estimates, there would be room for doubt. This may be the tip of the iceberg for direct dark matter detection, but then again, it may not.
December 19, 2009 at 5:54 pm |
Hi Jim,
this is a nice way to organize the first signals from the LHC experiments. I wonder what the next ones will be – care to venture a guess?
Michael
December 22, 2009 at 4:55 pm |
I’ve been found out!
My guess would be either Sigma+ -> proton pi0 (1953) or Sigma0 -> Lambda photon (1956), since these have the same strangeness content as the Lambda and therefore a similar rate of production in proton collisions. Also, a Sigma signature can be constructed from already-established components (the proton, pi0, Lambda, and photon).
— Jim
January 10, 2010 at 8:28 am |
a story with a difference http://bennymay.wordpress.com/
January 11, 2010 at 11:28 am |
Hi Jim,
any chance you will make another nice post? Perhaps I can suggest one: concerning alignment, how would we recognize and error in which all dimensions were mis-measured by 0.5%? I’m talking about a complete rescaling of all length scales by a factor close to but not equal to one? I have one idea, but I’ll bet you have better ideas, and this may interest readers of your blog. :)
regards.
Michael
August 18, 2010 at 9:24 pm |
Great thanks for sharing.
February 20, 2014 at 4:52 am |
Isn’t it time you stopped idly blogging from your mobile phone and took your website seriously. When I first started using them, I only had Twitter and Facebook widgets which were placed several inches apart on the homepage of my blog.
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