From Russia with love (memories from the November 1974 revolution...)

... in particle physics

The International Conference on High Energy Physics 2016 conference comes to an end with no revolution in sight so let us go back to the past for a while ... just to remind the youngest reader and put in perspective the "legendary" number of papers about the 750 GeV pseudo-resonance and biggest statistical/quantum fluctuation since decades:

... on November 10, 1974 two groups (one, a MIT group doing experiment on the east coast at Brookhaven National Laboratory, U.S.A. and the other a SLAC- Berkeley group doing experiment on the west coast at Stanford Linear accelerator centre, U.S.A) simultaneously announced the discovery of a new particle at 3095 MeV whose lifetime was about 1000 times longer than that of other particles of comparable mass. This announcement set on fire the world of high energy physics and is now known in the physics community as the November revolution. Like many revolutions, its meaning was not clear at first. To appreciate the surprise, imagine if one suddenly discovers a new pyramid, twice as heavy as the largest one known so far and yet a thousand times narrower and thus higher! The unprecedented large life time (or narrowness of the peak) led to a host of theoretical speculations and vigorous experimental activity. During the next one year, more than seven hundred papers were written related to this discovery which was a record in physics (if not in entire science) at that time. Subsequently, this record was broken after the discovery of high Tc super-conductivity.  

The J/Ψ discovery electrified the community for many reasons including its simultaneous discovery in two different laboratories and on two entirely different type of machines. Its impact on the development of high energy physics was tremendous and within two years of its discovery, in 1976, the two men Samuel Ting and Burton Richter who led those two group were awarded the Nobel prize in physics. Apart from Raman effect and parity violation, there are not many other discoveries which were recognized that soon by the Nobel committee... 

Soon after the announcement of the J/ψ discovery, there followed a host of theoretical speculations about what it is. The big question was, why is J/ψ so narrow and hence long lived? Some of the suggestions were : it is an intermediate vector boson, Higgs boson, lightest colored particle, lightest particle with a new quantum number called paracharge, charm-anticharm (cc) quark bound state ( i.e. charmonium bound state). There followed a vigorous theoretical activity trying to figure out the correct answer. In between, the SPEAR group also discovered three more states through radiative transitions whose masses were between those of ψ ′ and J/ψ. Within about one year after the discovery it was clear that J/ψ was cc bound state so that the basic constituents of nature were were four quarks and four leptons. The other states discovered at SPEAR were also easily understood as the various states of the charmonium (cc). Remarkably, it was shown that the cc spectrum can be well understood within the framework of non-relativistic quantum mechanics plus spin dependent corrections. One last obstacle in this picture was the existence of “Charmed mesons”. However even these were discovered by the middle of 1976 and it convinced even the most die-hard skeptics about the validity of the charm hypothesis. 

Around this time followed two more rather unexpected discoveries, namely those of τ lepton at 1786 MeV and bb bound states where b is the fifth quark. I would say that these two were the last two surprises and in the last twenty years we have not had any more surprises in High Energy Physics.

The November J/Ψ Revolution: Twenty-Five Years Later

Avinash Khare(Submitted on 25 Oct 1999)

Memento of the standard model (and its absolute totalitarian system)

In the once fast moving field of Particle Physics, the basic ingredients of the Standard Model were in place {in 1974?}. In 1976 ... an epochal experiment (Prescott et al) provided the definitive evidence that all neutral current effects stemmed from one parameter, the Weinberg angle. Since then, experiments have confirmed the validity of the Standard Model without challenging its fundamental structure: it is a relativistic local quantum field theory in four space-time dimensions. Experiments have found all but one of its predicted particles: in 1983, the W± and Z gauge bosons are discovered at CERN; the Z width suggests at most three “normal” neutrinos. In 1995 the top quark is discovered, and the ντ neutrino in 2000, both at FermiLab. The Higgs particle, a spinless particle predicted by the Standard Model remains beyond the grasp of experimentalists {has eventually been discovered at CERN in 2012}. 

There is more in Nature than the Standard Model: 

- The first evidence is Dark Matter in the Universe, which suggests (a) new particle(s), stable enough to be fourteen billion years old, not predicted by the Standard Model.

- The second chink in the armor of the Standard Model appears in 1998, when the SuperKamiokande collaboration presents definitive evidence for neutrino oscillations, implying at least two massive neutrinos which also require new particle(s) not predicted by the Standard Model.

... 

Like all successful theories, the Standard Model offers new hints and poses new problems. Massive neutrinos require an extension of the Standard Model. The mystery of three families of elementary particles and their disparate masses and mixings, the flavor problem demands resolution. The quantum numbers patterns offer the most spectacular hints, together with asymptotic freedom, of a unified picture of quarks and leptons, at a scale close to the Planck length. Finally, although the Standard Model appears to be a mostly perturbative quantum field theory, it includes a relatively light spinless particle. This apparent theoretical curiosity (it is a puzzle if the Standard Model is expanded to include new physics at much larger scales) has led to endless speculations, ranging from supersymmetry, to technicolor, to extra dimensions, and finally to “whatever theories” at TeV scales. 

The LHC discoveries will be cast in terms of the Standard Model: yesterday’s theory is today’s background. To prepare you for the new discoveries, it is necessary to have a sound understanding of the Standard Model, which is the purpose of these five instructions: - First Instruction: All About Relativistic Local Field Theories - Second Instruction: The Standard Model - Third Instruction: The Standard Model with Massive Neutrinos - Fourth Instruction: Why Three Families? - Fifth Instruction: Grand Unification of the Standard Model. 

Gravity is not included in the following discussion, since it is consistent with General Relativity, albeit with an inexplicably small (eV scale) cosmological constant.

The Five Instructions

Pierre Ramond (Submitted on 1 Jan 2012)

Motto about the Higgs 

... as Lenin once explained, “The Higgs mechanism is just a reincarnation of the Communist Party: it controls the masses” [..., apocryphal. I learned this quote from Luis Alvarez-Gaumé.].

Naturally Speaking: The Naturalness Criterion and Physics at the LHC

G.F. Giudice(Submitted on 16 Jan 2008 (v1), last revised 30 Mar 2008 (this version, v2))