Particle body-count 2

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
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.

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