A Conceptual Problem:

How to do a good scientific work?

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The following discussion compares the development of two scientific ideas that refer to the predictions of two particles - the Ω- and the pentaquark. The mass of these particles is expected to belong to the same mass range. (The Ω- mass was predicted quite accurately whereas the pentaquark mass has not been predicted.)

The published prediction of the Ω- took place on 1962 (see e.g. here ). This prediction has been independently proposed by Gell-Mann and Ne'eman. Their idea was based on the assumption that baryons are made of 3 spin-1/2 components (now called quarks) whose states can be arranged in sets. Each set belongs to an appropriate representation of the SU(3) group. Just two years later the Ω- was discovered experimentally. This discovery is regarded as a landmark in the particle physics history (see e.g. here ).

The pentaquark's fate was completely different. Its existence was predicted by several authors in the second half of the 1980s [1,2]. The idea of pentaquark existence is based on a strong interaction theory called QCD. Attempts to discover pentaquarks have begun soon after their prediction was published. The Ω- and the pentaquarks differ in several aspects:
  1. The search for the Ω- lasted about 2 years whereas the search for the pentaquark continues for more that 2 decades.
  2. The search for the Ω- used the technology of the early 1960s whereas the search for the pentaquark uses a much more advanced technology.
  3. Consider the larger duration of the dedicated search for the pentaquark. Referring to this issue, one should realize that pentaquarks could have been found accidentally during more than 2 decades before their existence have been predicted. Therefore, pentaquarks have not been detected for about one half of a century.
  4. The search for the Ω- was successful whereas the search for the pentaquark is a flop (see e.g. here ). Note that this link points to a report on the failure to detect pentaquarks which was published by the Particle Data Group (PDG). PDG is the authorized organization for experiment evaluation and for the definition of particle existence and of its properties.
  5. The predictions of the Ω- and of the pentaquark rely on different theoretical grounds. The Ω- prediction assumes the existence of spin-1/2 quarks whereas the pentaquark prediction is based on a specific strong interaction theory called QCD.
  6. The following text explains why the pentaquark detection which was recently (2015) announced by CERN is irrelevant to the QCD pentaquark. (See here ).
The following evidence emphasizes the previous points and demonstrates the amazing technological progress that has taken place during recent decades. It is well known that it is more difficult to produce an anti-baryon than the production of the corresponding baryon. Now, in a report on an experiment carried out about a decade ago, it is mentioned that nearly two million of anti-Ω- have been detected (L. C. Lu et al., Phys. Rev. Lett. 96, 242001 (2006)). These data prove that in the case of particles that really exist and their mass falls in the range of 1-2 GeV, the present technology detects millions of events that contain each of these particles. By contrast, as of today, the prolonged pentaquark search has found nothing. This failure supports the PDG conclusion that pentaquarks do not exist.

The discovery of the Ω- has provided a strong support for the theoretical idea of quarks. Several years later, an independent support for the quarks was derived from the analysis of deep inelastic electron-proton scattering. Today there is no theoretical doubt concerning quark existence. This example shows that an experimental success affects the promotion of the corresponding theory.

By contrast, as far as the present physical establishment is concerned, the systematic failure of pentaquark search has made no effect on the theoretical validity of QCD and of its wider theory called the Standard Model (SM). Furthermore, professional physicists simply ignore this failure and state that the SM is flawless. (QCD is the strong interaction sector of the SM.) Thus, for example, Michio Kaku states in a book named Hyperspace, which was published by the Oxford University Press: "The Standard Model can explain every piece of experimental data concerning subatomic particles up to about 1 trillion electron volts in energy... This is about the limit of the atom smashers currently on line. Consequently, it is no exaggeration to state that the Standard Model is the most successful theory in the history of science" (see here and elsewhere).

In another book named "Introduction to Nuclear and Particle Physics", Second Edition by A. Das and T. Ferbel, World Scientific Publishing, the authors state: "We have mentioned several times that the Standard Model appears to be in complete agreement with all measurements."

Matt Strassler states in a recent Higgs Symposium (January 9-11, 2013):

SM is simplest and most elegant theory consistent with data
- Completely self-contained; no missing parts, no inconsistencies
- No confirmed conflicts with any existing experiments!
- Simplest and most elegant → the one most likely to be right

(See here ). Note that the exclamation mark is included in Strassler's text.

Considering the pentaquark flop described above, one wonders why scientists make statements that are blatantly wrong. Is it a reasonable way for doing a good scientific work?

P.S. The QCD pentaquark failure is just one example. Many different kinds of QCD failure have already been published. Readers of popular science texts may find information in this book and in the internet site here (please start with items on the right hand panel). Physicists can also read the following scientific article here .

As a matter of fact, these QCD failures should not be regarded as a surprise. Indeed, QCD has been constructed on the basis of an incorrect interpretation of the data. For a short presentation of this point, see here . Thus, excluding miracles, one expects that an erroneous basis cannot yield a correct theory.

M. Gell-Mann certainly was a key person of the QCD construction (see here). It is interesting to point out a recent publication of his doubtful opinion on QCD's merits. Thus, he has advised a colleague who worked on QCD and told him that he "should work on more worthwhile topics" (see here). This new information about Gell-Mann's qualms concerning the QCD merits certainly provides another support for the above mentioned claims.


References:

[1] C. Gignoux, B. Silvestre-Brac and J. M. Richard, Phys. Lett. 193, 323 (1987).

[2] H. J. Lipkin, Phys. Lett. 195, 484 (1987).