Saturday, November 23, 2013

A new upper bound to electron's dipole moment as an additional blow against standard SUSY

A further blow against standard SUSY came for a couple of weeks ago. ACME collaboration has deduced a new upper bound on the electric dipole moment of electron, which is by order of magnitude smaller than the previous one. Jester and Lubos have more detailed commentaries.

The measurement of the dipole moment relies on a simple idea: electric dipole moment gives rise to additional precession if one has parallel magnetic and electric fields. The additional electric field is now that associated with the molecule containing electrons plus strong molecular electric field in the direction of spin quantization axes. One puts the molecules containing the electrons into magnetic field and measure the precession of spins by detecting the photons produced in the process. The deviation of the precession frequency from its value in magnetic field only should allow to deduce the upper bound for the dipole moment.

Semiclassically the non-vanishing dipole moment means asymmetric charge distribution with respect to the spin quantization axis. The electric dipole coupling term for Dirac spinors comes to effective action from radiative corrections and has the same form as magnetic dipole coupling involving sigma matrices except that one has an additional γ5 matrix bringing in CP breaking. The standard model prediction is of order de≈ 10-40 e× me,: this is by a factor 10-5 smaller than Planck length!

The new upper bound is de ≈ .87 × 10-32 e×me and still much larger than standard model prediction. Standard SUSY predicts typically non-vanishing dipole moment for electron. The estimate for the electron dipole moment coming from SUSYs and is by dimensional considerations of form de= c ℏ e× me/16π2M2, where c is of order unity and M is the mass scale for the new physics. The Feynman diagram in question involves the decay of electron to virtual neutrino and virtual chargino and the coupling of the latter to photon before absoption.

This upper bound provides a strong restriction on "garden variety" SUSY models (involving no fine tuning to make dipole moment smaller) and the scale at which SUSY could show itself becomes of order 10 TeV at least so that hopes for detecting SUSY at LHC should be rather meager. One can of course do fine tuning. "Naturality" idea does not favor fine tunings but is not in fashion nowadays: the existing theoretical models do not simply allow such luxury. The huge differences between elementary particle mass scales and quite "too long" proton lifetime represent basic example about "non-naturality" in the GUT framework. For an outsider like me this strongly suggests that although Higgs exist, Higgs mechanism provides only a parametrization of particle masses - maybe the only possible theoretical description in quantum field theory framework treating particles as point like - and must be eventually replaced with a genuine theory. For instance, Lubos does not see this fine tuning is not seen as reason for worrying too much. Personally I however feel worried since my old-fashioned view is that theoretical physicists must be able to make predictions rather than only run away the nasty data by repeated updating of the models so that they become more and more complicated.


Ulla said...
weak interaction, the same as neutrinos have...

Hamed said...

Dear Matti,

suppose for a point like particle that have electric charge, we know it’s Lagrangian is P^2/2m+1/2ε*E^2-1/2μ*B^2-q*φ(x)+j.A(x).

Now i supposed φ(x) and A(x) are zero. In the Lagrangian of Kahler action
L= J^munuJ_munu, I guess this reduce to 1/2ε*E^2-1/2μ*B^2 in analogy with classical ED, but now E is Kahler electric field and B is Kahler magnetic field.
Hence, it seems for me that it contains only 1/2ε*E^2-1/2μ*B^2 and not P^2/2m for the particle. What is my misunderstanding?

An example to clarify my misunderstanding:
There is a constant electric field in a space. Suppose there is a point like particle with charge q is in the field. Because Electric field is constant, induced electric field on the particle is constant too. it’s lagrangian of Kahler action is
L= J^munuJ_munu= 1/2ε*E^2
I expect that variation of the L for this point particle with respect to induced metric of imbedding space and induced kahler form of CP2, gives us Eq=d/dt(mv) that is equation of the particle. but without adding1/2*m*v^2, is it possible?

Matti Pitkanen said...

Dear Hamed,

what you say about Kahler action is certainly true (by the way, the induced Kaehler form does not correspond directly to em field but to U(1) factor in electroweak action: it has also interpretation as color YM action if color field is identified as H^A J, A levels the color Hamiltonians).

This of course does not correspond as such to
single particle limit at which we forget all the details about particle space-time sheet and keep only four-momentum and charge as relevant information.

Consider now the description of the interactions of particle space-time sheet idealised with 1-D curve with the classical induced fields at larger space-time sheet, The total rest energy of Kahler field defines the mass of the particle. Four-momentum has the usual expression by Lorentz invariance. Charge corresponds to classical em charge if quantum classical correspondence holds true.

The interaction with larger space-time sheet results from the topological sum contact (wormhole contact but not carrying Kahler magnetic flux): space-time sheet touches the larger one. This interaction is described just as in ordinary classical approach by the replacement p--p-eA_em. A_em is describable in terms of induced spinor connection.

Hamed said...

Dear Matti,

“The total rest energy of Kahler field defines the mass of the particle”
what is the total rest energy of Kahler field?

“. This interaction is described just as in ordinary classical approach by the replacement p--p-eA_em. A_em is describable in terms of induced spinor connection”

This Is just what I don’t understand that why J^mnnuJ_munu reduced to 1/(2m)*(p-eA_em)^2 at point like limit?
At point like limit of particle, J_munu is also define as partial_mu(A_nu)-partial_nu(A_mu). Hence we have J_munu yet and hence J_munu =1/2ε*E^2-1/2μ*B^2 is correct at this limit. What is wrong in the argument?

Matti Pitkanen said...

You can assign to Kahler action conserved currents and therefore also charges by Noether's theorem.This gives also energy, momentum, angular momentum and color charges from isometries.

[There are excellent reasons to believe on existence of additional infinite-D algebra of symmetries].

J_munuJ^munu does not reduce to the kinetic term at point like limit. There is no reason nor need for this. The limit is more abstract. W have a description from which we throw out everything related to the extended character of particle and keep only information about charge and mass. Then we ask how to achieve gauge invariance inspired by the gauge couplings of CP_2 spinor connection on fermions in this description.

J_munu and components of induced spinor component remain only in the description of larger space-time sheet - "the external world": as I have explained many times earlier there are several space-time sheet and each of them contributes to the external field so that linear superposition for the external fields corresponds to union for larger space-time sheets.

As I explained would could proceed from scattering amplitudes too and end up via Schrodinger equation to classical description.
Consider as an example the point-like limit of string theory. From the spectrum you take just massless states for which string effectively behaves like point like particle and construct by symmetry arguments Einstein YM action: it reproduces in lowest order stringy amplitudes for massless particles.

You can of course consider also more precise description of particles. String like objects, CP_2 type vacuum externals provide this kind of descriptions involving induced Kaehler field explicitly but they are mathematically much heavier.

Anonymous said... thoughts?

Matti Pitkanen said...

I have been reconsidering free energy related claims during this year. If you believe that those who lived at forties understood everything about nuclear physics, you can conclude that all cold fusion researchers are crackpots or swindlers. I cannot however invent any reason for believing that these people could have been so clever. There are simply too many anomalies. The reality has left academics with their dusty text books far behind, and the development of a new technologies is in full swing.

Theoretical input would be badly needed but is lacking due to the closed-mindedness of academic community. Similar problems appear everywhere: in particle physics, cosmology, in biology, in neuroscience,…. Academic research is in deep intellectual, ethical, and moral crisis.

TGD explains nicely these anomalies and builds close connections other free energy anomalies and to quantum biology. Hierarchy of Planck constants viz dark matter, magnetic body, etc. are the new notions explaining the anomalies.

I wrote some time ago about TGD variant of Widom-Larsen model for cold fusion, which expains nuclear transmutations quantitatively but has some fatal weaknesses: see

and .