Charming surprise: First evidence for CP violation in charm decays

Nov 15, 2011 by Antonella Del Rosso

The LHCb Collaboration has presented today at the Hadron Collider Particle Symposium in Paris possible first evidence for CP violation, the difference between behaviour of matter (particles) and antimatter (antiparticles), in charm decays.

The CP violation in charm quarks has always been thought to be extremely small. So, looking at particle decays involving matter and antimatter, the LHCb experiment has recently been surprised to observe that things might be different. Theorists are on the case.

The study of the of the charm quark was not in the initial plans of the LHCb experiment, whose letter “b” stands for “beauty quark”. However, already one year ago, the Collaboration decided to look into a wider spectrum of processes that involve charm quarks among other things.

The LHCb trigger allows a lot of these processes to be selected, and, among them, one has recently shown interesting features. Other experiments at b-factories have already performed the same measurement but this is the first time that it has been possible to achieve such high precision, thanks to the huge amount of data provided by the very high luminosity of the LHC.

“We have observed the decay modes of the D0, a particle made up of a charm quark plus a u antiquark”, explains Pierluigi Campana, LHCb Spokesperson. “In particular, we have studied and combined the decay rates of the D0 and its antiparticle. According to the theory of the Standard Model, we should have measured a very small value of a parameter known as Delta ACP that is calculated using these decay rates and is related to the properties of matter and antimatter. We found that Delta ACP is around 0.8% instead of the predicted 1‰ (or less). Although making precise evaluations in processes involving charm quarks is difficult, the Delta ACP parameter appears to be much higher than expected”.

And while theorists have already started looking into the unexpected result to check possible explanations or find completely new causes, the LHCb scientists are putting all their energy into pushing their analysis even further. “So far we have analysed only about 60% of the data available from the 2011 run”, says Pierluigi Campana. “We plan to complete the analysis but also to perform independent checks using different approaches and strategies”.

The LHCb Collaboration and the theorists held a joint meeting at CERN on 10 and 11 November to discuss the impact of LHCb results on the current theories and how we should now look at the properties of the charm quark. The improved measurement and the independent checks planned by the Collaboration will certainly contribute to clarifying the situation. The new results should be available by early next year.

Explore further: Cold Atom Laboratory creates atomic dance

More information: lhcb-public.web.cern.ch/lhcb-public/

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User comments : 20

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eyeyamtheufo
not rated yet Nov 15, 2011
Nice comments on the result. http://matpitka.b...bar.html
SincerelyTwo
4 / 5 (4) Nov 15, 2011
" We found that Delta ACP is around 0.8% instead of the predicted 1 (or less)."

I'm confused, looking for 1.% OR LESS, and 0.8% is LESS than 1%.

That statement contradicts itself because if less than 1% was expected and less than 1% was found then it agrees with expectations.

I'm not a physicist, so I take it the statement was ... stated poorly, can anyone correct this or shed some light on it?
bsobel
5 / 5 (1) Nov 15, 2011
@SincerlyTwo: 1 0/00 is not the same as 1 0/0 (the comment won't let me use the same symbols used in the article)
nxtr
5 / 5 (2) Nov 15, 2011
Article fails to define CP as charge parity.
dschlink
5 / 5 (4) Nov 15, 2011
Just weirdness in the way the article expresses the values.

"The analysis gives ACP=-.82 /- .21 (stat). /- .11 (sys) per cent. The prediction of standard model is of order .01 per cent."

So, they are seeing 80 times what is predicted.
Vendicar_Decarian
1 / 5 (1) Nov 16, 2011
80 times ay? Well that's good. There is more for me.
rawa1
1 / 5 (5) Nov 16, 2011
The similar CP violation finding already evaporated with higher amount of data. The three sigma evidence is nothing special in the light of previous unconfirmed findings. For example, the constraints on supersymmetry from ATLAS (A Toroidal LHC Apparatus) were systematically more stringent than those from CMS (Compact Muon Solenoid).

http://resonaance...ive.html

http://resonaance...ope.html

http://www.ibtime...sing.htm

This finding was already announced at both Tevatron, both LHC and it had been always withdrawn later. The recent history teaches us not to celebrate before the signal is confirmed by an independent experimental group. If nothing else, it would be always good to wait for results from other detector of LHC, or we could face the same disappointing again and again.
Callippo
1 / 5 (6) Nov 16, 2011
In dense aether model the CP violation is the subject of certain distance scale. The very tiny or large objects are too random, the objects at the human observer scale are too complex. The symmetry of objects is highest at the dimensional scale of atom nuclei and the objects composed of mostly atom nuclei (dense stars like white dwarfs). So if you expect some CP symmetry violation effects, you've actually four areas of space-time scale, where these CP symmetry violation should be most pronounced.
eachus
5 / 5 (4) Nov 16, 2011
The similar CP violation finding already evaporated with higher amount of data.


You are confused. The earlier (potential) discoveries and retractions involved the B (beauty or bottom) quark, where this data is on the decay of charmed quarks, which are much less massive. In particular, a higher CP violation in charmed quark decays could contaminate the data on B quark decays, which is why the LHCb collaboration was "revisiting" this decay which was thought to be understood.

(I've avoided naming the mesons involved, because the names just make the whole thing more confusing unless you are very familar with, for example, all the varieties of K mesons.)
Callippo
1 / 5 (4) Nov 16, 2011
This is why I said "the SIMILAR CP violation finding" not "the SAME CP violation finding". The outcome, when such observations are averaging with higher amount of events data gradually is typical and predicted with dense aether model too.
Nerdyguy
3.7 / 5 (3) Nov 16, 2011
" We found that Delta ACP is around 0.8% instead of the predicted 1 (or less)."

I'm confused, looking for 1.% OR LESS, and 0.8% is LESS than 1%.

That statement contradicts itself because if less than 1% was expected and less than 1% was found then it agrees with expectations.

I'm not a physicist, so I take it the statement was ... stated poorly, can anyone correct this or shed some light on it?


0/0 is percent, 0/00 is per thousand
Standing Bear
1 / 5 (1) Nov 16, 2011
How about a force attendant to the charmed quarks. Other quarks give rise to electrical charges, etc. How about these.
Seeker2
1 / 5 (2) Nov 18, 2011
We can construct what you might call a toy model to understand a simple means of pair production in quantum spacetime, and use this model to make testable predictions.

You could say matter particles are curved positively and anti-matter negatively, leaving 0 net curvature in spacetime. The DE continusously reshapes elements of spacetime into random forms.

Spacetime elements come equipped with certain preset molds (quarks) where if an element of spacetime takes the correct form it falls into some combination of these molds and forms a particle-antiparticle pair. Random fluctuations may be greater than that required to fit a particular mold and the excess energy is released as radiation.
Seeker2
1 / 5 (2) Nov 18, 2011
cont...
The work done to move the boundaries by the quantum fluctuations is equivalent to the mass of the particle pairs. Work done to compress an element for a given time is the same (or nearly the same) as that done to stretch adjacent elements (move the adjacent boundaries) so the masses of the particle pair are equal. Small differences in the work functions may result in radiation. But their form (quark-antiquark combinations) is obviously different so CP violation should be no big surprise.
Seeker2
1 / 5 (2) Nov 18, 2011
...if an element of spacetime takes the correct form it falls into some combination of these molds

Let's make that if elements of spacetime take the correct form (or configuration) they fall into some allowable combination of these molds
thuber
1 / 5 (1) Nov 19, 2011
What makes many small effects useful is Resonance. Whether it is population inversions in lasers, or moderated fission chain reactions, one can take a tiny effect and via some sort of resonance liberate huge amounts of energy. One can hope that in the distant future the CP violation could be exploited for a useful physical effect. Any ideas?
Callippo
1 / 5 (1) Nov 19, 2011
In dense aether model the CP violation is the subject of certain distance scale. The very tiny or large objects are too random, the objects at the human observer scale are too complex. The symmetry of objects is highest at the dimensional scale of atom nuclei and the objects composed of mostly atom nuclei (dense stars like white dwarfs). So if you expect some CP symmetry violation effects, you've actually four areas of space-time scale, where these CP symmetry violation should be most pronounced.

http://www.aether...cale.gif

At the case of Sun it would manifest with asymmetry of polar jets of neutrinos, emanated with core of Sun, but in just quite weak way. At the case of Earth this effect is even weaker and it manifest itself with asymmetry of Earth geoide, which has a pear shape profile, the oblateness of which is different at the North and South poles (as Columbus already consider during his planning of his travel around Earth).
Callippo
1 / 5 (2) Nov 19, 2011
One can hope that in the distant future the CP violation could be exploited for a useful physical effect.
The rotating massive bodies exhibit polar jets, which aren't completely symmetric. This effect is most pronounced at scale of atom nuclei and at scale of dense stars, mostly composed of atom nuclei. For example, we can imagine each star is surrounded with layer of neutrinos with positive curvature at its center and the layer of antineutrinos with negative surface curvature above its surface. When such star will rotate, the whole system becomes chiral and it will result in different speed of neutrino vortex and Lense-Thirring drag at south and north pole. I suspect, the recent observation of asymmetry of Earth's inner core as a manifestation of CP symmetry violation. The biological homochirality can be interpreted as an example of CP symmetry violation too.

http://aetherwave...ity.html
Callippo
1 / 5 (1) Nov 19, 2011
The chirality of black holes can be observed with "naked eye". These black holes exhibit asymmetric jets, i.e. they're behaving in similar way, like oriented Co-60 nuclei, which are emanating radioactivity in one direction only.

http://www.ifa.ha...7Jet.png

http://www.aether...ity1.gif

The search for jet suppression belongs into important aspect of LHC collider experiments.

http://cdsweb.cer.../1388598
Seeker2
not rated yet Dec 05, 2011
...if an element of spacetime takes the correct form it falls into some combination of these molds

Let's make that if elements of spacetime take the correct form (or configuration) they fall into some allowable combination of these molds

Let's make these combinations quantum states. Sorry.