Hunting for Neutrinos (40:38)
Vincenzo Cavasinni & Paola Catapano (2007).
Directed by Emanuele Angiuli
and produced, under the name "Orione", by CERN,
Istituto Nazionale di Fisica Nucleare (INFN-Pisa),
Laboratori Nazionali Gran Sasso (LNGS),
Laboratori Nazionali del Sud (LNS-Catania) and the
association for scientific culture La Limonaia (Pisa).
Beta-Decay, Weak Interactions & Neutrinos
(2018-05-27) Conservation laws in beta-decay (1930)
This is what led Pauli to postulate the existence of an elusive neutral particle
of spin 1/2, now called neutrino.
" I have done a terrible thing: I have postulated a particle that cannot be detected.."
Wolfgang Pauli (Dec. 1930).
Pauli was definitely too harsh on himself.
The fact that three conserved quantity would otherwise be missing
in beta-decay (energy, linear momentum and angular momentum)
would now be considered a definite proof of something otherwise
undetected. Pauli had proposed to call the new particle "neutron"
because it had no electrical charge but that name would soon be preempted
by James Chadwick
(1891-1974; Nobel 1935) for the massive nuclear particle he
discovered in 1932,
which now stands.
The particle postulated by Pauli was given its final name of neutrino
(Italian for "little neutron") by
Enrico Fermi (1901-1954)
who first used the name in public at a meeting in Paris
(July 1932) following a suggestion made jokingly
in a friendly conversation with another Italian physicist
Edoardo Amaldi (1908-1989)
in the wake of Chadwick's aforementioned discovery of the neutron.
In 1942, Wang Ganchang (1907-1998)
had suggested that reversebeta capture could provide an experimental
way to detect the influx of antineutrinos from a nearby nuclear reactor, through the reaction:
ne + p+
® n + e+
It would take another 14 years to actually make such a detection,
which earned the surviving experimenter (Reines) a belated Nobel prize in 1995.
In a supernova, a huge number of neutrinos are
typically observed several hours before the explosion can be detected optically.
This was first noticed (after the fact)
in the case of SN1987A,
a naked-eye supernova from the
Large Magellanic Cloud
whose light first reached us on 1987-02-23.
Now, a system of neutrino detectors is in place
(SNEWS)
to provide early-warning directional information to all observatories a few hours before the
the next nearby supernova becomes visible...
We don't want to miss it!
(2018-06-06) Electroweak Theory
Quantum unification of electromagnetism and weak interactions.
As a student of Julian Schwinger (1918-1994;
Nobel 1965)
Sheldon Glashow (b. 1932) originally
came up with the idea which eventually led to our current understanding of the weak force with three intermediate
vector bosons (massive bosons of spin 1) besides the photon, using
Yang-Mills theory.
Two of opposite unit charge (W- and W+) and a neutral one (Zo).
It wasn't yet clear at this point how this would account for the observed
strangeness-changing properties of weak interactions.
In Paris, in 1959,
Glashow talked about that to Gell-Mann,
who reformulated the idea and reported on it at the Rochester conference of 1960.
The problem was then to generalize Yang-Mills theory beyond the SU(2) of isospin.
It took a young assistant professor of mathematics at Caltech (Dick Bloch)
to point out to Gell-Mann, in the Fall of 1960, that simple Lie groups had already
been classified before SU(3) appeared as the next logical choice for such a generalization,
