Meritocratic or mediocre?

ATLAS and CMS are the names given to two large experimental setups at the Large Hadron Collider (LHC), the world’s biggest accelerator for high energy physics (elementary particle physics) at the European CERN laboratory near Geneva. The setups are huge and heavy – 10,000 tons – and technologically very advanced and innovative: from superconducting magnets to highly integrated ‘deep sub-micron’ electronics. The detectors deal with tens of proton-proton collisions every 50 nanoseconds, producing thousands of particles at this high rate. In order words: the proton bunches in the beams meet and collide at the center of these detectors two hundred million times per second. Powerful and smartly programmed computer systems filter out about one hundred of the most interesting collision ‘events’ per second for recording them on a mass storage medium for further ‘off line’ analysis. In total the experiments record approximately 15 million gigabytes per year. The worldwide LHC computing grid – a distributed infrastructure – was developed for storing and analyzing these data.

The teams of scientists involved in each of these experiments (ATLAS, CMS) number two and a half, maybe three thousand persons. The period over which ATLAS/CMS were designed, constructed, built, commissioned up to ‘data taking’ and data analysis (‘physics’) is about 15 years, longer for the hand full of pioneers involved from the very early days of audacious planning. Audacious because they had to plan for technological advances that were by no means sure to happen. They had to work hard to make them happen!

ATLAS/CMS fully live up to the expectations. They collect their data very efficiently from the collisions provided prolifically by the Large Hadron Collider, also working wonderfully well. Prolific is also the production of scientific papers by ATLAS/CMS. I read them with great interest. It is exciting, breathtaking, to follow the hunt for the Higgs boson (its ‘hiding place’ has been localized quite accurately; before the end of 2012 we will have captured it!).

But there is one thing that disturbs me about the scientific publications of ATLAS/CMS. And that is the author list, in particular the length of it. You can find all 3000 authors on every paper. That is ridiculous. It brings high energy physics into a cultural crisis. It prevents the young and brilliant to manifest themselves through a distinctive publication record. It allows mediocrity to creep in.

I call on ATLAS/CMS to do something about this. In these days of web-based publishing it should be technically easy to distinguish, say, five categories of authors. 1: those who really did the innovative analysis published in a particular paper; 2: those, usually more senior, who were closely involved in inspiring, supervising, checking, improving the work; 3: those who made distinctive, but more generic contributions to the technical infrastructure of particular importance for the paper under consideration; 4: the present leadership of the collaboration; 5: the long retired who once made a contribution to the collaboration.

I know, my categories are not perfect, but they are a start. If high energy physics is to survive it has to very quickly re-emphasize scientific excellence again as the most important criterion for leadership.

Jos Engelen, March 26, 2012

News

Electrons, the ubiquitous constituents of matter, are very interesting objects of study. The electron was the first elementary particle to be discovered (by J.J. Thomson in 1897)  and today it belongs to the rather exclusive group of the fundamental particles of the Standard Model.

In 1927 Paul Dirac discovered the equation that describes the propagation (in space and time) of electrons. This was a great achievement: his equation incorporated Einstein’s theory of relativity and the principles of quantum mechanics (Bohr, Heisenberg, Schrödinger) at the same time. The Dirac equation had a very remarkable feature. It predicted, in fact it required, that if electrons exist, which is obviously the case, also the anti-particle of the electron should exist, but no such particle was known. Initially this was a problem for Dirac but when the positron was discovered (Anderson, 1933) this problem was solved.

The electron and the positron are distinctly different particles as they have opposite charge. Neutrinos are fundamental particles in many respects similar to electrons and positrons, with one distinct difference: they carry no electrical charge, they are neutral. And this opens the possibility that neutrinos and their

anti-particles, the anti-neutrino’s, are in fact the same particles. This possibility was suggested by Majorana (in a publication of 1937).  In somewhat technical terms, Majorana found a representation of the Dirac equation with real (as opposed to complex) wave functions as a solution. For a particle described by a real wave function the distinction between particle and anti-particle vanishes.

Both electrons and neutrinos carry a quantity called ‘spin’, angular momentum. They carry a spin of ½ unit. Such particles are called fermions. (All fundamental constituents of matter are fermions.) Their quantum-mechanical properties are very different from particles with ‘integer’ spin (bosons). This difference is expressed by the Pauli exclusion principle, it leads for example to electron orbits in atoms and explains the structure and stability of matter.

Whether neutrinos are ‘Dirac particles’ or ‘Majorana particles’ is a valid physics question that has not been answered to date. It is experimentally very difficult to answer this question, but experiments are ongoing. If neutrinos are Majorana particles this has profound consequences for our understanding of the nature of fundamental particles as encoded in the Standard Model.

Whether Majorana particles exist or not in nature remains an open question. Apart from neutrinos, so called neutralinos are candidates as well. Neutralinos appear in extensions of the Standard Model (invoking ‘super symmetry’ between fermions and bosons) but whether Supersymmetry is realized in nature is not at all sure. This is one of the questions the Large Hadron Collider at CERN is trying to answer.

Nature News of February 28, 2012 announces:  ‘Quest for quirky quantum particles may have struck gold’ , Evidence for elusive Majorana fermions raises possibilities for quantum computers. The scientific quality of this news article is rather poor. Although it is published by Nature. But it is a news article. Sensational, that sells. The achievement it describes is impressive, however. Leo Kouwenhoven and his group of Delft University have created a setup to demonstrate, for the first time, the existence of quantum states in a nano-device that are mathematically equivalent to Majorana ferminos as described above. Moreover such devices may be used as ‘quantum bits’ of futuristic quantum computers. Leo Kouwenhoven has produced a scientific result that ranks in a rare category: that of breakthroughs. We will hear more from him!

The question whether neutrinos are Majorana particles or Dirac particles continues to need an answer. Elementary particle physicists will have to continue their experiments to find out. The question whether neutralinos are realized in nature: high energy physics experiments will have to tell.

Meanwhile I will find out more about Majorana states in condensed matter and as soon as Kouwenhoven’s results are available in the Open Access literature I will read more about them with great interest!

Jos Engelen
March 2, 2012