LHCb finds new hints of possible deviations from the Standard Model

April 18, 2017
Credit: CERN

The LHCb experiment finds intriguing anomalies in the way some particles decay. If confirmed, these would be a sign of new physics phenomena not predicted by the Standard Model of particle physics. The observed signal is still of limited statistical significance, but strengthens similar indications from earlier studies. Forthcoming data and follow-up analyses will establish whether these hints are indeed cracks in the Standard Model or a statistical fluctuation.

Today, in a seminar at CERN, the LHCb collaboration presented new long-awaited results on a particular decay of B0 mesons produced in collisions at the Large Hadron Collider. The Standard Model of predicts the probability of the many possible decay modes of B0 mesons, and possible discrepancies with the data would signal new physics.

In this study, the LHCb collaboration looked at the decays of B0 mesons to an excited kaon and a pair of electrons or muons. The muon is 200 times heavier than the electron, but in the Standard Model its interactions are otherwise identical to those of the electron, a property known as lepton universality. Lepton universality predicts that, up to a small and calculable effect due to the mass difference, electron and muons should be produced with the same probability in this specific B0 decay. LHCb finds instead that the decays involving muons occur less often.

While potentially exciting, the discrepancy with the Standard Model occurs at the level of 2.2 to 2.5 sigma, which is not yet sufficient to draw a firm conclusion. However, the result is intriguing because a recent measurement by LHCb involving a related decay exhibited similar behaviour.

While of great interest, these hints are not enough to come to a conclusive statement. Although of a different nature, there have been many previous measurements supporting the symmetry between electrons and muons. More data and more observations of similar decays are needed in order to clarify whether these hints are just a statistical fluctuation or the first signs for new particles that would extend and complete the Standard Model of particles physics. The measurements discussed were obtained using the entire data sample of the first period of exploitation of the Large Hadron Collider (Run 1). If the new measurements indeed point to beyond the Standard Model, the larger data sample collected in Run 2 will be sufficient to confirm these effects.

Explore further: How universal is (lepton) universality?

More information: LHCb statement: lhcb-public.web.cern.ch/lhcb-p … /Welcome.html#RKstar

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8 comments

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EyeNStein
3.7 / 5 (3) Apr 18, 2017
B⁰ = One to watch. Any quark carrying particle which can oscillate into its own anti-particle especially when the Down and Bottom it's made of (each of them being alternatively the anti-matter half) have a marked mass difference.
How do you draw a Feynman diagram for that oscillation in conjunction with flavour changing/inverting which implies the weak force is involved??

Any extension of weak force theory would be very interesting as it is demonstrably the only matter/anti-matter sensitive force we know of.
Could the weak force be a leftover/range-limited manifestation of the original matter/antimatter symmetry breaking force in the universe?
Hyperfuzzy
Apr 18, 2017
This comment has been removed by a moderator.
EyeNStein
4.5 / 5 (2) Apr 18, 2017
B⁰ meson is composed of 'Bottom plus anti-down' quarks and "oscillates" into 'anti-bottom plus down' quarks.
Bottom is a quark 'flavour' so the meson is oscillating/changing from B+1 to B-1.
Flavour changing usually requires the weak force. (though I'm not sure about a flavour inversion??)
The weak force is uniquely able to distinguish between spin-sign and matter-anti-matter: Its hyper-charge is also associated with the Higgs field which fills all of space with a non-zero-weak-hypercharge.
All in all, the weak force is a HUGE question mark which seems to hold the answers to the earliest formation of the state of universe and its most basic matter-anti-matter symmetry.
baudrunner
4.5 / 5 (2) Apr 18, 2017
You can't really predict anything with CERN or any other particle collider beyond the energies one calculates to produce the next-level intermediate vector boson. That's how Higgs particle was found. That's why this data aren't statistically significant, and in no way reflect the presence of "cracks" in the Standard Model.

The Lepton Universality model is flawed from a logical standpoint. We can assume that because the electron has 1/200th the mass of the muon, a lot less energy is required to produce them, so they will logically outnumber muon production in the same time that it requires to produce them.
SKULLTRAP
not rated yet Apr 18, 2017
huh?

Yo man ive been sayin that all DAY dog!
Hyperfuzzy
not rated yet Apr 19, 2017
huh?

Yo man ive been sayin that all DAY dog!

Yeah, charge can travel through each other. I think what they are trying to see is how many pockets they can fill at the same time, i.e. two protons occupying the same space and having multiple sets. Or maybe they are looking for triple occupancy, imagine the acceleration on parting, and further collisions ... funny naming convention, confusing.

But what kind of flow upon colliding same, same? I see a funny soup!
Whydening Gyre
5 / 5 (1) Apr 20, 2017
huh?

Yo man ive been sayin that all DAY dog!

Yeah, charge can travel through each other. I think what they are trying to see is how many pockets they can fill at the same time, i.e. two protons occupying the same space and having multiple sets. Or maybe they are looking for triple occupancy, imagine the acceleration on parting, and further collisions ... funny naming convention, confusing.

But what kind of flow upon colliding same, same? I see a funny soup!

Hunh?!?
Hyperfuzzy
not rated yet Apr 20, 2017
huh?

Yo man ive been sayin that all DAY dog!

Yeah, charge can travel through each other. I think what they are trying to see is how many pockets they can fill at the same time, i.e. two protons occupying the same space and having multiple sets. Or maybe they are looking for triple occupancy, imagine the acceleration on parting, and further collisions ... funny naming convention, confusing.

But what kind of flow upon colliding same, same? I see a funny soup!

Hunh?!?

Exactly!

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