Letters

• ISOLDE then and now • Neutrinos and the Standard Model • Dick Garwin and g-2

ISOLDE then and now

I was pleased to see your piece about the 50th anniversary of the ISOLDE project (CERN Courier December 2017 p36). It is truly remarkable how ISOLDE, over such a long time and in its evolving shapes, has succeeded in maintaining world leadership in the study of exotic nuclei. This is a success story for the scientists involved and CERN as an organisation willing to support excellent science in areas other than mainstream particle physics.

The picture from 1967 that you used shows the original ISOLDE team in the underground cavern between the Synchrocyclotron building and the main gates (note the white lab coats – the experiment was run by the then nuclear chemistry group). The person standing to the right in the picture is group leader Arve Kjelberg, a nuclear chemist originating from Pappas’ group in Oslo. Kjelberg moved on to become deputy director of the nuclear physics division under Herwig Schopper and, after leaving CERN, he held senior positions in the Norwegian Ministry of Science and Education until retirement. He passed peacefully away in June 2016.

•  Leif Westgaard

Neutrinos and the Standard Model

I read with interest your interview with Weinberg (CERN Courier November 2017 p31) and would like to draw attention to a statement made on page 34, “Whereas simply inserting neutrino masses into the theory would violate the SU(2)×U(1) symmetry.”

There is a simple way to put neutrino masses into the Standard Model (SM): just add their right-handed terms like any other fermion, and standard Higgs doublet couplings, and you get masses, SU(2)×U(1) symmetry and renormalisability. This point was not addressed in the article and it gives the impression that it is really impossible to maintain SM renormalisibility and give mass to the neutrinos at the same time. This would be a clear failure of the SM and gauge theories, but it isn’t the case.

• Biagio Di Micco

Editor’s reply:

The article perhaps could have been clearer that the symmetries of the SM make it impossible to give masses to neutrinos without introducing either non-renormalisable interactions or new fields, namely right-handed neutrino fields that have no interactions with SM gauge fields. The latter would leave the mystery of why neutrino masses are so tiny, however, while the effective-field theory point of view ensures that non-renormalisable terms in the SM are naturally very small, explaining the smallness of neutrino masses and potentially other observables, too.

Dick Garwin and g-2

Last year CERN Courier reported on measurements of the anomalous magnetic moment of the muon, g-2 (July/August 2017 p11). There was a second (hidden) occasion in the January/February issue (“Atomic pioneer wins presidential medal”) where it was reported that Dick Garwin received the Presidential Medal of Freedom from former US president Barack Obama for his long career in research and invention. Garwin’s significant contributions to particle physics and his work at CERN, however, were not mentioned.

In an experiment undertaken at Columbia in 1957 together with Leon Lederman and Marcel Weinrich, Garwin made the first observation of parity violation in muon decay and measured the value of g-2 to a precision of around 10%. At CERN, starting in 1959, Garwin was also a member of the group that performed the first g-2 experiment at the Synchrocyclotron.

•  Pier Giorgio Innocenti