Abstract

In this page, the physics idea of vacuum engineering is dicussed. It's possible experimental tests (both in CEBAF and in ALICE project)are also dicussed.

(1) Ideas from T.D.Lee

"we may expect vacumm to be as complex as spin-0 field PHI(x) at zero 4-momentum limit..... Like spin-0 field, it is conceivable that the vacuum state may carry quantum numbers such as isospin I, parity P, strangeness S, etc. In this context, we may ask: Could the vacuum be regarded as a physical medium? If under suitable conditions the properties of vacuum, like those of any medium, can be altered physically, then the answer would be affirmative. Other wise it might degenerate into semantics..... In such a scheme one often assume that there exists some phenomenological spin-0 field PHI which may carry such quantum number and whose vacuum expectation value is not zero....."

In answering how vacuum property can be altered, T.D.LEE used an anlog in Fig.1 and wrote:

" How can we produce such a change in the expectation value of PHI? The problem is analogous to the formation of domain strutures in a ferromagnet. We may draw the analog:
expectation value of PHI(x)-------magnet spin,
J=matter source-------------------magnetic field
as shown in Fig. 16.1"

Fig.1 Domain structures in a ferromagnet vs. in Vacuum

" In the case of a very large ferromagnet, because the spins interact linearly with the magnet field , a domain structure can be created by applying an external magnetic field over a large volume. Further more, after domains are created, we may remove the external field; depending on the long-range forces, the surface energy and other factors, such a domain structure may persist even after the external magnetic field is removed. Similarly, by applying over a large volume any matter source J which has a linear interaction with PHI(x) , we may hope to create [2] a domain structure in PHI(x). Depending on the dynamical theory, such domains may also remain as physical realities, even after the matter source J is removed.....".

In Fig.2, T.D.LEE also predict two possible different way of changement of PHIbar (the expectation value of PHI(x)).

Fig.2 Change of expectation value of PHI (we use PHIbar to stand for this) due to a constant external matter source J. In case (a) PHIbar changes continuesly with J. In case (b) , as J increases, there is a critical value at which PHIbar makes a sudden jump.

In the last chapter of his book, T.D.LEE predict "possiblity of vacuum engineering" as one of the three most promising developements of future physics[3]. He wrote

"Based on either the spontaneous symmetry-breaking mechanism or quark-confinement phenomena, we believe our vacuum, though Lorentz invariant, to be quite complicated. Like any other physical medium, it can carry long-range-order parameters and it may also undergo phase transitions. Hitherto, in any high-energy experiments the higher the energy, the smaller is the spatial region that we are able to explore. Consequently , we have avoided the apportunity to study coherent phenomena which may be connected with vacuum. To explore such possibilities, we have to distribute high energy or high matter density over a large spatial volume. The experimental method to alter the properties of the vacuum may be called vacuum engineering. An effective way may well be to use relativistic heavy ions. In order to overcome the short -distance strong nuclear repulsive forces generated by omega0 and other vector mesons, we need energy much larger that 1 GeV per nucleon in the center-of-mass frame. If we can create vacuum excitations or vacuum phase transitions, then any of the constants in our present theory, thetaW, thetaC, Mu, Md... can subject to change. if indeed we are able to alter the vacuum, then we may encouter some new phenomena, totally unexpected."

(2) Comments on T.D.LEE's ideas

In our experimetalists eyes, T.D.LEE is a bookworm too. He does not realize that it is very difficult to observe those quantities in real life. In heavy -ion experiments, we have so many tracks in each event so that it is very hard to eliminate backgrounds. Some quantities of weak interaction are very hard to detect because nutrinous are very hard to be detected by our normal 4 PI detectors.

T.D.LEE does not tell us if "matter source" and "antimatter source" make the same direction of vacuum phase transition or makes opposite direction of vacuum phase transition. So we do not know how hopeless we can have in CEBAF.

(3) Possible test on T.D.LEE's ideas on ALICE or other Heavy ion experiments

However, things may change a bit when ALICE experiments begin to run. In ALICE experiments, many Z0 is also produced.[4] Z0 is very friendly to us because it has large possibility in decaying into e+e- or mu+mu- and those lepton pairs are of higher momentum so that the high mutiplicities of tracks each event no longer bother us. And Z0 is short lived so it still reflect the things happened before the domain dissapeared. And I also know that in ALICE, they have good PID and momentum resolution in 20 GeV tracks[5].

We know that Z0 mass is believed to be propotional to the expectation value of PHI(x) (we know that Higgs mechanism is also a good example of spontanious symmetry breaking), so it is a good testing of the formation of the domain or vacuum phase transition.

Please also notice that even after the fire ball in A-A collision dissapeared, the domain may still exists. so we may use J/Psi mass or Psi' to test it too. At least we can know the upper limit of the life time of such domain, shoud such domain exists. What should be reminded is that we should choose extremely low Pt and Pl group of J/Psi to test so that when it decay, it still stay near that domain.

How I wish ALICE project were an USA project!!!

(4) Possible test on T.D.LEE's ideas on CEBAF

And what encourages me is that we already see some surprising difference in particle properties inside nucleus.

We know that the reaction P+Lamda--P+P does happen inside hyper nucleus. "So what happens inside nuleus" ?[6]. So this deltaS=2 events may already show the difference of Vacuum inside nucleus with the vacuum outside nucleus. The vacuum inside nucleus carry more S flavor?

I also notice that Edward, Brash .et al had done an experiment of the mass shift of rho and phi in e+deutron experiments[7]. They prove that if well arranged (that means, rho and phi can stay longer enough near nucleus), the rho or phi has about 150 MeV mass shift too. Normally theory (the effective potential theory which comes from nucleus spectrum) only expect some less than 50 MeV mass shift. Of course by adding some extra interaction bewteween quarks by hand , they can always "explain" experimental results. But we should not do that way. Or at least such extra interaction bewteween quarks must be tested in higher energy experiments seperately.

So again what happens inside "nucleus"?

WE have nucleus and e beam in CEBAF. So we should not lose heart here.

(5) Weak charge of Protons and of nucleus?

Among the numerous proposals in CEBAF, only a few attract my eye balls, and Q-weak proposal is among them.

here I am not qualified enough to understand 100% what that proposals means yet. But I do know that Q_weak is closely related to thetaW. Knowing that CEBAF can have very accurate measurement of proton weak charge comforts my brain and eyes very much.

There is already a very good talk on proton weak charge, so I do not need to explain too much on this. What interested me is what can we think if we keep T.D.LEE's idea in mind about the facts listed in that proposal?

I noticed that in AVP (Atomic Parity Violations) experiments, the weak charge of Cesium has about 2 sigma deviation from theoretical prediction[8]. They probably believe than this may imply Z' existance. But what I say is probalby this comes from vacuum phase transition because Cesium is already a heavy nucleus.

So I would suggest that Proton weak charge and it's deviation from theory may reflect the existance of Z', but the weak charge of heavy nucleus compared to the experimental P and N weak charge relect the vacuum phase transition.

So here I strongly suggest that CEBAF detect the weak charge of Au. I would expect that the weak charge of Au will deviate more from theory and from the P and N weak charge measured from experiments , so that we know better the source of weak charge deviation. Further more, if we have more points at different A of nucleus, and if these data points deviate at the same direction, we will be more sure that such deviation is not caused by fluctuation. The confidence level will be greatly higher.

(6) Help!

(7) Conclusion

References

[1] "Particle Physics and Introduction to Field Theory", by T.D.LEE, Page 379.

[2] T.D.LEE and G.C.Wick, Phys.ReV. D9,2291 (1974)

[3] "Particle Physics and Introduction to Field Theory", by T.D.LEE, Page 826

[4] A talk in Lunch meeting when Chuncheng Xu was in Heidelberg.

[5] Private communication with Prof. Johanna Stachel, 2003

[6] Private chatting with Prof. Tang Liguang in CEBAF , 2003

[7] Ed.Brash know which article I am reffering to.

[8] Q_weak proposal
V.A.Dzuba et al., hep-ph/0204134 vi 12, Apr 2002.

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