Carlo Rubbia and the discoveries of the weak bosons

http://t.co/KGVNarwZMG by @ulaulaman about #CarloRubbia #NobelPrize #physics #particlephysics

On that day 30 years ago, I was almost certainly at school. Physics still was not my passion. Of course I started very well: when the teacher asked what is the space, I thought immediately to the universe, but the question was not referring to that "space", but in another, the geometric. But it is not about those memories that I have to indulge, but on a particular photo, in which Carlo Rubbia and Simon van der Meer, with two goblets, presumably of wine in hand, are celebrating the announcement of the Nobel Prize for Physics

for their decisive contributions to the large project, which led to the discovery of the field particles W and Z, communicators of weak interaction

The story of this Nobel, however, began eight years earlier, in 1976. In that year, in fact, SPS, the Super Proton Synchrotron, begins to operate at CERN, originally designed to accelerate particles up to an energy of 300 GeV.

The same year David Cline, Carlo Rubbia and Peter McIntyre proposed transforming the SPS into a proton-antiproton collider, with proton and antiproton beams counter-rotating in the same beam pipe to collide head-on. This would yield centre-of-mass energies in the 500-700 GeV range⁽¹⁾.

On the other hand antiprotons must be somehow collected. The corresponding beam was then

(...) stochastically cooled in the antiproton accumulator at 3.5 GeV, and this is where the expertise of Simon Van der Meer and coworkers played a decisive role⁽¹⁾.

Refining the mass of W

In our standard model of elementary particles we have four fundamental interactions: gravity, electromagnetism, strong nuclear force and weak interaction. In particular the last force is responsible for the radioactive decay and for the hydrogen fusion in stars. The bosons of the interaction (the particle exchanged between two fermions) are $W^\pm$ and $Z$ bosons. An example of weak interaction is $\pi^+$ decay:

The weak bosons are predicted in 1968 by Glashow, Weinberg and Salam⁽¹⁾ and discovered at CERN in 1983 in a series of experiments conducted by Carlo Rubbia and Simon van der Meer⁽²⁾. Now, from one of the last analysis from Tevatron, we have the last measure of W bosons. Indeed CDF's researchers propose the following preliminary value for $W$: \[M_W = (80.387 \pm 0.019) GeV\] and combining it with previous measures, the new preliminary world average is

I must remember that $(80.390 \pm 0.016) GeV$ will became the new $W$ mass only after the publication of the CDF's preprint (pdf) in a peer review journal and after the publication of the further calculation on the Particle Data Group. Indeed Wired (and en.wiki, following Wired), following Tommaso Dorigo, who simply described the experimental process that carries to the measure and to the new proposal, has just setted the new mass, forgetting the reviewing scientific process. So, until then, the average mass is $(80.399 \pm 0.023) GeV$⁽³⁾.