quarks (2)

Right-Handed Photons...


Topics: Modern Physics, Particle Physics, Quantum Mechanics, Quarks

Note: A primer on quarks at Hyperphysics</a>

On 17 January 1957, a few months after Chien-Shiung Wu’s discovery of parity violation, Wolfgang Pauli wrote to Victor Weisskopf: “Ich glaube aber nicht, daß der Herrgott ein schwacher Linkshänder ist” (I cannot believe that God is a weak left-hander). But maximal parity violation is now well established within the Standard Model (SM). The weak interaction only couples to left-handed particles, as dramatically seen in the continuing absence of experimental evidence for right-handed neutrinos. In the same way, the polarisation of photons originating from transitions that involve weak interaction is expected to be completely left-handed.

The LHCb collaboration recently tested the handedness of photons emitted in rare flavor-changing transitions from a b-quark to an s-quark. These are mediated by the bosons of the weak interaction according to the SM – but what if new virtual particles contribute too? Their presence could be clearly signaled by a right-handed contribution to the photon polarization.

In pursuit of right-handed photons, A report from the LHCb experiment, CERN Courier

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In Finnegan's Wake...

Murray Gell-Mann won the 1969 Nobel Prize in Physics.Credit: Santa Fe Institute


Topics: Nobel Laureate, Nobel Prize, Particle Physics, Quarks, Standard Model, Theoretical Physics

The Nobel Prize in Physics 1969 was awarded to Murray Gell-Mann "for his contributions and discoveries concerning the classification of elementary particles and their interactions."

The Nobel Prize in Physics 1969. NobelPrize.org. Nobel Media AB 2019. Wed. 29 May 2019. < https://www.nobelprize.org/prizes/physics/1969/summary/ >

Murray Gell-Mann, one of the founders of modern particle physics, died on 24 May, aged 89. Gell-Mann’s most influential contribution was to propose the theory of quarks — fundamental particles that make up most ordinary matter.

To bring order to a plethora of recently discovered subatomic particles, in 1961 Gell-Mann proposed a set of rules based on symmetries in the fundamental forces of nature. The rules classified subatomic particles called hadrons into eight groups, a scheme he named the eightfold way in a reference to Buddhist philosophy.

In 1964, he realized that such rules would naturally arise if the particles were composed of two, three or more fundamental particles, held together by the strong nuclear force. (US–Russian physicist George Zweig came to the same conclusion independently in the same year.) Protons and neutrons, for example, would be made up of three of these more fundamental particles, which Gell-Man named quarks, inspired by a quote — “Three quarks for Muster Mark!” — from James Joyce’s 1939 novel Finnegan's Wake. [1]

Quarks and Leptons are the building blocks which build up matter, i.e., they are seen as the "elementary particles". In the present standard model, there are six "flavors" of quarks. They can successfully account for all known mesons and baryons (over 200). The most familiar baryons are the proton and neutron, which are each constructed from up and down quarks. Quarks are observed to occur only in combinations of two quarks (mesons), three quarks (baryons). There was a recent claim of observation of particles with five quarks (pentaquark), but further experimentation has not borne it out. [2]


1. Murray Gell-Mann, father of quarks, dies - US physicist was one of the chief architects of the standard model of particle physics. Davide Castelvecchi, Nature
2. Hyperphysics: Quarks

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