# Discovery of anti-deuteron and the implication of CPT violation

From this review by Antonino Zichichi 2009 and this review from T. D. Lee in 2007, it is said that Dirac is very upset when hearing the discovery of anti-deuteron (anti-matter of deuteron, the nucleus of deuterium, called a deuteron, contains one proton and one neutron) in 11 March 1965.

However, Dirac is famous for prediction of the first anti-matter of electron, the positron. His prediction is based on the invariance of charge C-symmetry. Now we know that the parity P (Lee-Yang 1956) and charge C are both violated, and the CP is violated too.

question: What is the implication of CPT for the discovery of anti-deuteron?

i) Is that CP violating and T-violating but CPT is preserved?

ii) It is known at least mentioned in the this review by Antonino Zichichi 2009 see also this review article that the CPT is violated at the Planck scale, and relativistic QFT does not hold. Does the discovery of anti-deuteron imply anything about CPT violation?

iii) Finally, the final comment from the review "This implies that no theory exists that can guarantee that if we have matter then antimatter must exist. This is why the fact that all anti-atoms with their antinuclei must exist with certitude resulted from the experiment at CERN in March 1965." I suppose that it means that the violation of CPT does not guarantee the existence of anti-matter nor the existence of antinuclei. Is this interpretation correct and accepted? So what are the current theory that supports the violation of CPT?

• To prove the CPT theorem, Lorentz invariance is assumed (Pauli-Lueders). Conversely, violation of the CPT theorem leads to Lorentz violation (Greenberg). What makes you think any current theories violate Lorentz invariance? Do you know of one beyond free speculation? – Cosmas Zachos Mar 20 '17 at 0:36
• Planck scale is a lattice cutoff high energy scale (at quantum gravity) that probably violate the relativistic at microscopic thus violate the CPT theorem. – wonderich Mar 20 '17 at 0:56
• because the energy cutoff is like a lattice scale, so both the rotation symmetry and the relativistic symmetry is not an exact symmetry at the lattice scale. It may be at most the emergent symmetry. – wonderich Mar 20 '17 at 1:03
• CP symmetry violation is equivalent to T symmetry violation, and CPT remains invariant. There is no observation or theory that has Lorentz invariance and not CPT invariance. There is no accepted theory of physics at the Planckian scale. That includes possibly no Lorentz covariance (since no accepted theory), nobody can prove whether it holds or not. There's also no accepted GUT. – Bob Bee Mar 20 '17 at 1:10
• There are Two Refs indeed, which I mixed up: this review from T. D. Lee in 2007 and this by Antonino Zichichi 2009 – wonderich Mar 20 '17 at 22:14

Dirac came out of his depression when he received a phone call from his friend Abdus Salam, saying: "Relax Paul, my friend Nino Zichichi has discovered the antideuteron".

This is the opposite of the summary in your question (v1) which suggests that Dirac believed for some reason that the antideuteron shouldn't occur and was upset when it was found.

The position of the article is as follows. The prediction of the anti-electron is, as Dirac discovered, a mathematical result of trying to satisfy the symmetries of the Lorentz transformation when describing the interaction between electromagnetic fields and charged objects with spin-half. The simplest acceptable spinor winds up having four components with the same mass: two with one sort of charge which transform into each other under rotations, and two with the other sort of charge which transform into each other under rotations. This is more or less the same QED that we use today and is quite general, describing the interaction between the electromagnetic field and the electron; the electromagnetic field and the proton, thus predicting antiprotons; and the electromagnetic field and the neutron, predicting antineutrons. (Remember that the neutron couples to electromagnetism because it has a nonzero magnetic moment.)

However, Dirac's quantum electrodynamics makes no effort to describe strong or weak nuclear forces. In 1965 there wasn't yet a good theoretical treatment of the strong nuclear interaction. There was experimental evidence for the anti-electron, the anti-proton, and the anti-neutron, with the same masses as their matter counterparts; however it was experimentally possible that the anti-proton and anti-neutron would interact via some antimatter-specific strong interaction that was not the same as the matter version. A probable consequence of a distinct anti-strong force would be that the anti-deuteron, an anti-proton and anti-neutron bound together by the anti-strong force, would probably have a different binding energy, excitation spectrum, and mass than the matter deuteron, if it were stable at all.

If the deuteron, $d$, and its antiparticle, $\bar d$, had different masses, even though $m_p=m_\bar p$ and $m_n = m_\bar n$, an experimenter could distinguish between a matter universe and an antimatter universe by capturing neutral baryons on charged baryons and measuring the wavelength of the photons that are emitted. (It's a 2.2 MeV photon, whose energy/wavelength is known at the part-per-million level based on its diffraction through a perfect silicon crystal, which is a great paper you should read sometime.) But that breaks CPT symmetry: reverse time, invert space, flip all the charges, and everyone should agree on lengths and on scalars like masses. The combined symmetry CPT is a consequence of invariance of spacetime under Lorentz transformations --- but it was invariance under Lorentz transformations that we used to predict antimatter in the first place. You can see why Dirac would have been agitated by the possibility.

Lorentz invariance, and therefore invariance under the combined transformation CPT, is a starting assumption for all modern quantum field theories, including quantum electrodynamics, quantum chromodynamics, and the theory of the electroweak interaction. When your article's author writes that "at the Planck energy ... CPT invariance breaks down," I'm not entirely sure what he has in mind. (I have some ideas, but this already-long answer isn't the place for me to work through them.) There isn't any contemporary theory that includes CPT-breaking, just like there isn't any contemporary theory that makes solid predictions of what happens and Planck-scale energies.

There are some folks who are thinking about CPT-breaking phenomenology: if Lorentz invariance is only an approximate symmetry and you looked at this observable in that system, you might see such-and-so effect. But an observation like that would be a puzzle to be explained, not the fulfillment of any prediction.

• Thanks for the nice answer. However, I am not so sure that I understand it. In the article by Zichichi, it says: "The results, which showed the existence of a negative particle with mass equal to that of the deuteron" suggests that the anti-deuteron and deuteron have the same mass? Isn't it? So could you point out the C, P, T transformation and see how the CPT is violated? Thanks very much. – wonderich Mar 20 '17 at 22:14