Exploring the standard model of physics without the high-energy collider

August 10, 2009
Scientists have measured the largest effect of the "weak interaction" -- one of the four fundamental forces of nature -- ever observed in an atom. Credit: Image copyright American Physical Society [Illustration: Carin Cain]

Scientists at the University of California, Berkeley, and Lawrence Berkeley National Laboratory in the US, have performed sophisticated laser measurements to detect the subtle effects of one of nature's most elusive forces - the "weak interaction". Their work, which reveals the largest effect of the weak interaction ever observed in an atom, is reported in Physical Review Letters and highlighted in the August 10th issue of APS's on-line journal Physics.

Along with gravity, electromagnetism and the strong interaction that holds protons and neutrons together in the nucleus, the weak interaction is one of the four known fundamental forces. It is the force that allows the radioactive decay of a into a proton - the basis of carbon dating - to occur. However, because it acts over such a short range - about a tenth of a percent the diameter of the - it is almost impossible to study its effect without large, high-energy particle accelerators.

Theorists had predicted that the weak interaction between an atom's electrons and its nucleus could be quite large in Ytterbium (element 70 in the periodic table). To actually see this interaction, though, Dmitry Budker and his group at UC Berkeley had to carefully perform delicate measurements based on fundamental quantum mechanical effects and systematically eliminate other spurious signals.

The effect Budker and his colleagues see in Ytterbium is about 100 times bigger than what has been seen in Cesium, the atom in which most experiments in this field have been performed so far. The finding of such a large effect in Ytterbium poses an exciting opportunity to use tabletop atomic physics techniques as part of sensitive searches for new physics that complement ongoing efforts at the world's high-energy colliders.

More information:

Condensed matter physics: Melting the world's smallest raindrop
Calorimetric observation of the melting of free water nanoparticles at cryogenic temperatures [To appear in Physical Review Letters accompanied by a Viewpoint in Physics]

Source: American Physical Society

Explore further: Ytterbium's broken symmetry: The largest parity violations ever measured in an atom

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3.3 / 5 (6) Aug 10, 2009
With respect to symmetry violation by weak force, ytterbium is significant due its relatively high atom mass (it attracts electrons strongly toward atom nuclei) and it has an excess of neutrons, which are weakly binded to atom nuclei, so that lowest electron may be affected by weak interaction between neutrons, which introduces a weak spin related asymmetry into electron transitions. Spectra formed by splitting in EM field have different number of lines and energy levels for both sides of atom orbital, where are electrons with opposite spin.

This effect is pronounced the more, the less reversible electron transition is, i.e. for energy transitions between spherical s-orbitals. These transitions are of low probability ("prohibited energy levels"), because spherical orbitals are radiating EM wave poorly (whereas p-orbitals are behaving like antenna so they can radiate energy smoothly). Similar mechanism may be responsible for anomalous "cold fusion" effects, so it may become important even from practical point of view.
3 / 5 (6) Aug 10, 2009
Weak force symmetry violation was revealed before fifty years for radioactive cobalt nuclei, which are emanating different number of electrons from both sides. It can be revealed by thorough measurement of radioactivity of cooled cobalt atoms, which are oriented in strong magnetic field.


IMO the same effect can be observed even by "naked eye" on rotating black holes, which are emanating polar jets in assymetric way quite often. We can imagine black hole as an analogy of giant atom nuclei, here.

not rated yet Aug 10, 2009
Symmetry violation is caused by the weak force but exactly what is the weak force? Where does it originate from? A new theory claims the weak force comes from a background of "neutral neutrino" radiation. This neutral radiation is just ever so slightly more intense in the downward direction as opposed to the upward direction because a minute amount of this neutral radiation is absorbed after traveling through the earth.

Has symmetry violation really been proven? Maybe not:
Read on pg. 28 at the link.

not rated yet Aug 10, 2009
Reminds me of gravitational eccentricity of neutron stars to exact symmetry violation

http://www.spring...RG71.pdf -measuring gravity

http://www.spring...4P4H.pdf -ideal gas neutron star gravity calculations
3.4 / 5 (5) Aug 11, 2009
. what is the weak force..
It's a surface tension of tiny particles, which prohibits them in merging. If we shake a bit of mercury inside of test tube, we get a black dust composed of tiny mercury droplets, the extreme surface curvature of which prohibits them in merging.
4.2 / 5 (5) Aug 11, 2009
..reminds me of gravitational eccentricity of neutron stars ..
Yes, in this aspect the magnetar would be analogical to black hole asymmetry, just in less pronounced way. It would mean, particles are preferring one jet, while antiparticles would prefer another one. Whereas neutron stars are composed from single type of particles only, it would lead to gravity asymmetry for both poles.
not rated yet Aug 15, 2009
Alexa, very interesting comments, were it not that your English syntax than Yoda's much worse is for the fact that, you make.

Some help and coaching get, please.
3.7 / 5 (3) Aug 15, 2009
4.2 / 5 (5) Aug 15, 2009
I appreciate your comment, but many mistakes I can see most of mistakes just after when edditing of comment was closed. Fortunatelly English is quite readable even if it's not correct at all.
not rated yet Aug 16, 2009
. what is the weak force..
It's a surface tension of tiny particles, which prohibits them in merging. If we shake a bit of mercury inside of test tube, we get a black dust composed of tiny mercury droplets, the extreme surface curvature of which prohibits them in merging.

No, it's not surface tension, to have surface tension you first need to have a surface. Fundamental particles don't have one.
3.4 / 5 (5) Aug 16, 2009
Fundamental particles don't have one
So you have no surface too and youre fuzzy blob or something simmilar? How we can measure proton diameter, for example?


Model of elementar particle by AWT:


We can define diameter of particles like radius, when repulsive weak force changes into attractive strong nuclear force.

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