A Implications of a new 17 Mev vector boson on Higgs, SUSY

[kodama]

regarding this paper

Evidence for a Protophobic Fifth Force from 8Be Nuclear Transitions
Jonathan L. Feng, Bartosz Fornal, Iftah Galon, Susan Gardner, Jordan Smolinsky, Tim M. P. Tait, Philip Tanedo
(Submitted on 25 Apr 2016)
Recently a 6.8σ anomaly has been reported in the opening angle and invariant mass distributions of e+e− pairs produced in 8Be nuclear transitions. The data are explained by a 17 MeV vector gauge boson X that is produced in the decay of an excited state to the ground state, 8Be∗→8BeX, and then decays through X→e+e−. The X boson mediates a fifth force with a characteristic range of 12 fm and has milli-charged couplings to up and down quarks and electrons, and a proton coupling that is suppressed relative to neutrons. The protophobic X boson may also alleviate the current 3.6σ discrepancy between the predicted and measured values of the muon's anomalous magnetic moment.
Comments: 6 pages, 2 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)

for sake of discussion let us say that these results are valid, and there is indeed a new previously unknown 17mev vector X boson.

how does this affect the current SM, including virtual loop diagrams?

i.e Feng et al suggests it can explain the muon 3-sigma anomaly via virtual loop processes

how does this effect higgs stability and higgs hierarchy?

what are implications for dark matter?

implications for SUSY- extension. i.e does it alleviate or make worse things like FCNC. could this 17mev vector X boson be a SUSY partner of a known SM or SUSY particle?

a SUSY partner of a 17 MeV vector gauge boson X would be a fermion. what would be its properties, mass, stability, dark matter candidacy and would the LHC be able to see its SUSY-partner?

lastly, if this x-boson and the earlier LHC 750 GeV diphoton excess boson are both validated, how does the 2 taken together effect the preceding physics? i.e a standard model plus both a 17mev vector boson and 750 gev "scalar" boson on higgs hiearchy, SUSY, dark matter. could these 2 new particles be a part of a hidden sector? i.e the SUSY-partner of a 750 GEV scalar boson is also a fermion.

 

[mfb]

for sake of discussion let us say that these results are valid, and there is indeed a new previously unknown 17mev vector X boson.

Very unlikely - the same researchers previously found various other bosons that all disappeared in later experiments, with no explanation where they went. In other words, they simply don't understand their experiments.

I'm also not convinced that they checked compatibility with absolutely everything. Various fixed-target exoeriments should produce such a boson which should appear via the decay products.

what are implications for dark matter?

At least that hypothetical boson itself cannot be dark matter, as it is short-living.

 

[kodama]

Very unlikely - the same researchers previously found various other bosons that all disappeared in later experiments, with no explanation where they went. In other words, they simply don't understand their experiments.

I'm also not convinced that they checked compatibility with absolutely everything. Various fixed-target exoeriments should produce such a boson which should appear via the decay products.
At least that hypothetical boson itself cannot be dark matter, as it is short-living.

this boson though could couple to dark matter?

 

[mfb]

Well everything can couple to dark matter, and even if the boson exists it doesn't look very useful experimentally. You can see the $e^- e^+$ decay, invisible decay modes would be hard to study.

 

[Garlic]

What does protophobic mean? It sounds like they made it up.

 

[mfb]

It doesn't couple to protons, or at least its coupling to protons is very small. It is the same concept as "leptophobic" (doesn't couple to leptons), "fermiophobic" (doesn't couple to fermions), "hadrophobic" (doesn't couple to hadrons) and so on.

 

[kodama]

Well everything can couple to dark matter, and even if the boson exists it doesn't look very useful experimentally. You can see the $e^- e^+$ decay, invisible decay modes would be hard to study.

they suggest it can explain the muon magnetic unanimous moment discrepancy.

as a vector boson wouldn't it mediate a new force?

in SUSY would its SUSY partner a fermion be stable and if so a possible dark matter component.

 

[mfb]

as a vector boson wouldn't it mediate a new force?

Calling something a force gets a bit arbitrary in QCD. It would be a new interaction, sure.

in SUSY would its SUSY partner a fermion be stable and if so a possible dark matter component.

I don't think that can be determined just based on existing measurements.

 

[kodama]

Calling something a force gets a bit arbitrary in QCD. It would be a new interaction, sure.
I don't think that can be determined just based on existing measurements.

btw this article
http://blogs.scientificamerican.com/guest-blog/is-particle-physics-about-to-crack-wide-open/

Is Particle Physics About to Crack Wide Open?
Hints of an unexpected new particle could be confirmed within days—and if it is, the Standard Model could be going down

the rumors are that more data LHC is producing may confirm the 750 GEV boson within weeks.

basically same set of issues. how does this fit in SM and SUSY and higgs hierarchy?

with a mass of 750 GEV it seems to suggest there is new physics close to the EW scale.

 

[mfb]

the rumors are that more data LHC is producing may confirm the 750 GEV boson within weeks.

It is a fact that the 2016 dataset exceeds the 2015 one already (since yesterday). "May confirm" is an empty statement - getting larger datasets can always either confirm or not confirm things seen in smaller datasets. It is not certain, but expected, that first results are shown beginning of August.

This could mean nothing less than the fall of the Standard Model of particle physics (SM), which has passed every experimental test thrown at it since it was first put together over four decades ago.

No it does not mean that. It would mean we need an extension of the standard model. In the same way buildings are still built using Newtonian physics instead of general relativity, the SM remains a really good approximation in many measurements, no matter what comes up beyond it.

basically same set of issues. how does this fit in SM and SUSY and higgs hierarchy?

Depends on which of the 400 publications you prefer.

 

[kodama]

It is a fact that the 2016 dataset exceeds the 2015 one already (since yesterday). "May confirm" is an empty statement - getting larger datasets can always either confirm or not confirm things seen in smaller datasets. It is not certain, but expected, that first results are shown beginning of August.
No it does not mean that. It would mean we need an extension of the standard model. In the same way buildings are still built using Newtonian physics instead of general relativity, the SM remains a really good approximation in many measurements, no matter what comes up beyond it.
Depends on which of the 400 publications you prefer.

august -ill mark in my calendar

what is your preferred explanation for 750 gev diphoton if it turns out to be a verified particle. what is the most parsimonious extension of the SM that can accommodate it?

btw any idea how long it might take to verify a 17mev vector boson? should tevatron or lhc be able to verify or are hadron collisions too messy. would a linear e-p collider able to verify it?

 

[mfb]

3rd to 10th to be precise.

what is your preferred explanation for 750 gev diphoton if it turns out to be a verified particle.

Something that has more particles the LHC can find and study. A bound state of a new interaction? The start of a Kaluza-Klein tower? Some relation to dark matter would be great as well.

btw any idea how long it might take to verify a 17mev vector boson? should tevatron or lhc be able to verify or are hadron collisions too messy. would a linear e-p collider able to verify it?

A ~500 MeV positron fixed target experiment should be ideal. But I think the authors should understand their experiments first.

 

[kodama]

are there any ~500 MeV positron fixed target experiment in the works ?

 

[mfb]

People moved on to higher energies decades ago. Most electron positron colliders should be able to produce those beams with not too much effort, they have positron beams anyway. But currently I don't see the motivation.

 

[fresh_42]

People moved on to higher energies decades ago. Most electron positron colliders should be able to produce those beams with not too much effort, they have positron beams anyway. But currently I don't see the motivation.

This is what me as a layman makes me doubt the results. The energy level is so low that I cannot withstand to think that anything on this level should have been found decades ago.

 

[kodama]

People moved on to higher energies decades ago. Most electron positron colliders should be able to produce those beams with not too much effort, they have positron beams anyway. But currently I don't see the motivation.

discovering a new vector boson isn't motivation? what was LHC for then?

what about winning a nobel prize ?

 

[mfb]

discovering a new vector boson isn't motivation?

If there would be any reason to expect a boson it would be a motivation. But where is this reason?

For the LHC, it was clear that it would find something, because without Higgs and without anything else the theory would have broken down at energies the LHC can reach. And indeed, the LHC did find something - the Higgs so far.

 

[kodama]

If there would be any reason to expect a boson it would be a motivation. But where is this reason?

For the LHC, it was clear that it would find something, because without Higgs and without anything else the theory would have broken down at energies the LHC can reach. And indeed, the LHC did find something - the Higgs so far.

what would be ways to validate or rule out a protophobic 17 mev vector boson, apart from the hungarian researchers, that could be done in doable experiments ?

 

[mfb]

Well, the fixed-target experiment...
Would be quite cheap to set up, various facilities produce GeV electron beams, they can be used for conversion to photons and then electron/positron pairs, select the positron energy with a magnet, let it hit a thin target, then look for electron/positron pairs and measure their invariant mass and angular distribution.

 

[kodama]

Well, the fixed-target experiment...
Would be quite cheap to set up, various facilities produce GeV electron beams, they can be used for conversion to photons and then electron/positron pairs, select the positron energy with a magnet, let it hit a thin target, then look for electron/positron pairs and measure their invariant mass and angular distribution.

isn't this worth doing? any research groups attempting to verify this?

this is a nobel prize level discovery.

 

[mfb]

this is a nobel prize level discovery.

There is no discovery.

Is it worth digging in your backyard for oil? If there would be oil just below the surface, you would make a lot of money. Did you start digging already? Why not?

 

[CarlB]

If the fifth force is a gauge force like the three in the Standard Model, then the symmetry of the Standard Model needs to be extended. That is, the three forces in the Standard Model are mixed from the three symmetries of the Standard Model, SU(3), SU(2) and U(1). To add a 4th force, you need to look for a symmetry that contains SU(3)xSU(2)xU(1) but has 4 terms instead of 3. (Or maybe 5 terms if you want to add gravity as the 5th force.) Then you need to assign four quantum numbers to the various Standard Model elementary particles instead of the usual three.

Example: Suppose that we replace SU(3) with SU(3)xSU(3). To keep them straight, call them SU(3)_A x SU(3)_B. The idea is that these are a pair that is similar to how SU(2) x U(1) gives the electroweak force.

So make SU(3)_A the up quark and SU(3)_B the down quark. Then the representations for the up quark are 3 and 1 while the down quark's representations are 1 and 3. The other fermions are all singlets with respect to both SU(3)s.

Both quarks feel the same strong force so the strong force must be a mixture of the two SU(3) gauge forces. This sort of mixture is done with an angle like the Weinberg angle that mixes the SU(2) and U(1) electroweak gauge bosons to give the electric and weak forces. But since the two SU(3) are the same symmetry type, you expect the two mixtures to be something more natural:
SU(3)_A + SU(3)_B and
SU(3)_A - SU(3)_B.
Then the first mixture, SU(3)_A+SU(3)_B is the strong force while the other is the fifth force.

 

[lpetrich]

Very unlikely - the same researchers previously found various other bosons that all disappeared in later experiments, with no explanation where they went. In other words, they simply don't understand their experiments.

Some possibilities:

• They are not as good as they think they are at calculating predictions of mainstream nuclear and particle physics.
• Their experimental techniques are flawed.

 

[kodama]

If the fifth force is a gauge force like the three in the Standard Model, then the symmetry of the Standard Model needs to be extended. That is, the three forces in the Standard Model are mixed from the three symmetries of the Standard Model, SU(3), SU(2) and U(1). To add a 4th force, you need to look for a symmetry that contains SU(3)xSU(2)xU(1) but has 4 terms instead of 3. (Or maybe 5 terms if you want to add gravity as the 5th force.) Then you need to assign four quantum numbers to the various Standard Model elementary particles instead of the usual three.

Example: Suppose that we replace SU(3) with SU(3)xSU(3). To keep them straight, call them SU(3)_A x SU(3)_B. The idea is that these are a pair that is similar to how SU(2) x U(1) gives the electroweak force.

So make SU(3)_A the up quark and SU(3)_B the down quark. Then the representations for the up quark are 3 and 1 while the down quark's representations are 1 and 3. The other fermions are all singlets with respect to both SU(3)s.

Both quarks feel the same strong force so the strong force must be a mixture of the two SU(3) gauge forces. This sort of mixture is done with an angle like the Weinberg angle that mixes the SU(2) and U(1) electroweak gauge bosons to give the electric and weak forces. But since the two SU(3) are the same symmetry type, you expect the two mixtures to be something more natural:
SU(3)_A + SU(3)_B and
SU(3)_A - SU(3)_B.
Then the first mixture, SU(3)_A+SU(3)_B is the strong force while the other is the fifth force.

thanks for this, there is a paper that comments on this, would u mind looking at this paper and is it valid and what you had in mind?

Realistic model for a fifth force explaining anomaly in 8Be∗→8Bee+e− Decay
Pei-Hong Gu, Xiao-Gang He
(Submitted on 16 Jun 2016 (v1), last revised 12 Jul 2016 (this version, v5))
A 6.8σ anomaly has been reported in the opening angle and invariant mass distributions of e+e− pairs produced in 8Be nuclear transitions. It has been shown that a protophobic fifth force mediated by a 17MeV gauge boson X with pure vector current interactions can explain the data through the decay of an excited state to the ground state, 8Be∗→8BeX, and then the followed saturating decay X→e+e−. In this work we propose a renormalizable model to realize this fifth force. Although axial-vector current interactions also exist in our model, their contributions cancel out in the iso-scalar interaction for 8Be∗→8BeX. Within the allowed parameter space, this model can alleviate the (g−2)μ anomaly problem and can be probed by the LHCb experiment. Several other implications are discussed.
Comments: RevTex, 9 pages with no figures. New major changes are made to the older version
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
Cite as: arXiv:1606.05171 [hep-ph]
(or arXiv:1606.05171v5 [hep-ph] for this version)

 

[kodama]

There is no discovery.

Is it worth digging in your backyard for oil? If there would be oil just below the surface, you would make a lot of money. Did you start digging already? Why not?

this paper says based on already existing e-e+ collider data it is promising - since u are a HEP can u comment

High Energy Physics - Phenomenology
X(16.7) Production in Electron-Positon Collision
Long-Bin Chen, Yi Liang, Cong-Feng Qiao
(Submitted on 14 Jul 2016)
The anomaly found in a recent study of excited 8Be decay to ground state is attributed to an unusual vector gauge boson, the X(16.7). A 17 MeV gauge boson is obviously unexpected and hard to be embedded into the particle zoo of the standard model(SM). To confirm this finding, further experimental study are necessary. In this work, the production of this yet-not-verified new boson in electron-positron collision, for instance at BaBar is evaluated, and the results are encouraging. The data collected at BESIII and BaBar turn out to be enough to perform a decisive analysis and hence give a definite answer to the existence of X(16.7).
Subjects: High Energy Physics - Phenomenology (hep-ph)
Cite as: arXiv:1607.03970 [hep-ph]
(or arXiv:1607.03970v1 [hep-ph] for this version)
Submission history
From: Long-Bin Chen [view email]
[v1] Thu, 14 Jul 2016 00:43:49 GMT (154kb)

 

[mfb]

Looks like a confirmation of "such a particle would have been found long ago". It literally claims the data to exclude or confirm it has been recorded already. BaBar started their systematic search at 20 MeV, which means they probably had a look at 15 to 20 MeV as well at some point.

 

[kodama]

Looks like a confirmation of "such a particle would have been found long ago". It literally claims the data to exclude or confirm it has been recorded already. BaBar started their systematic search at 20 MeV, which means they probably had a look at 15 to 20 MeV as well at some point.

, for instance at BaBar is evaluated, and the results are encouraging.

 

[mfb]

I don't understand your last post.

 

[kodama]

I don't understand your last post.

paper said they overshot it at 20mev and they also cite this paper

Realistic model for a fifth force explaining anomaly in 8Be∗→8Bee+e− Decay
Pei-Hong Gu, Xiao-Gang He
(Submitted on 16 Jun 2016 (v1), last revised 12 Jul 2016 (this version, v5))
A 6.8σ anomaly has been reported in the opening angle and invariant mass distributions of e+e− pairs produced in 8Be nuclear transitions. It has been shown that a protophobic fifth force mediated by a 17MeV gauge boson X with pure vector current interactions can explain the data through the decay of an excited state to the ground state, 8Be∗→8BeX, and then the followed saturating decay X→e+e−. In this work we propose a renormalizable model to realize this fifth force. Although axial-vector current interactions also exist in our model, their contributions cancel out in the iso-scalar interaction for 8Be∗→8BeX. Within the allowed parameter space, this model can alleviate the (g−2)μ anomaly problem and can be probed by the LHCb experiment. Several other implications are discussed.
Comments: RevTex, 9 pages with no figures. New major changes are made to the older version
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
Cite as: arXiv:1606.05171 [hep-ph]
(or arXiv:1606.05171v5 [hep-ph] for this version)

which has a lower cross section then their estimate

 

[mfb]

paper said they overshot it at 20mev

See post #26.
The BaBar publication is here. The actual fit to the electron spectrum starts at 15 MeV. You need some sidebands for the region where your main analysis starts. That means they do not set proper upper limits in the range of 15 to 20 MeV, but a peak there would have been noted.

which has a lower cross section then their estimate

Oh well, the usual approach. "Our model is excluded!" "Quick, tune the couplings down so experiments need more data to exclude it!"

 

[kodama]

See post #26.
The BaBar publication is here. The actual fit to the electron spectrum starts at 15 MeV. You need some sidebands for the region where your main analysis starts. That means they do not set proper upper limits in the range of 15 to 20 MeV, but a peak there would have been noted.

Oh well, the usual approach. "Our model is excluded!" "Quick, tune the couplings down so experiments need more data to exclude it!"

still it does give quantitative predictions, and specific numbers.

btw any thoughts on this, would barbar or ep colliders produce this?

A light particle solution to the cosmic lithium problem
Andreas Goudelis, Maxim Pospelov, Josef Pradler
(Submitted on 29 Oct 2015 (v1), last revised 24 May 2016 (this version, v2))
We point out that the cosmological abundance of 7Li can be reduced down to observed values if during its formation Big Bang Nucleosynthesis is modified by the presence of light electrically neutral particles X that have substantial interactions with nucleons. We find that the lithium problem can be solved without affecting the precisely measured abundances of deuterium and helium if the following conditions are satisfied: the mass and lifetimes of such particles are bounded by 1.6MeV≤mX≤20MeV and few100s≲τX≲104s, and the abundance times the absorption cross section by either deuterium or 7Be are comparable to the Hubble rate, nXσabsv∼H, at the time of 7Be formation. We include X-initiated reactions into the primordial nucleosynthesis framework, observe that it leads to a substantial reduction of the freeze-out abundances of 7Li+7Be, and find specific model realizations of this scenario. Concentrating on the axion-like-particle case, X=a, we show that all these conditions can be satisifed if the coupling to d-quarks is in the range of f−1d∼TeV−1, which can be probed at intensity frontier experiments.
Comments: 5 pages, 4 figures; v2: minor improvements, matches published version
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
Journal reference: Phys. Rev. Lett. 116, 211303 (2016)
DOI: http://arxiv.org/ct?url=http%3A%2F%2Fdx.doi.org%2F10%252E1103%2FPhysRevLett%252E116%252E211303&v=08290ee6
Cite as: arXiv:1510.08858 [hep-ph]
(or arXiv:1510.08858v2 [hep-ph] for this version)

 

[mfb]

The long lifetime is a problem (note that this is incompatible with the proposed particle for the Beryllium decays). Apart from that, it would depend on the couplings.

 

[kodama]

The long lifetime is a problem (note that this is incompatible with the proposed particle for the Beryllium decays). Apart from that, it would depend on the couplings.

the paper studied the case of an axion like scalar but would a vector boson also work to reduce lithium 7

 

[kodama]

http://www.symmetrymagazine.org/article/the-atomki-anomaly

The next step is to double-check the result using other experiments. The LHCb experiment at the Large Hadron Collider or the upcoming Belle II detector in Japan could be good candidates, as could the Mu3e experiment in Switzerland and the DarkLight experiment in the United States, which are hunting for new particles around the same energy.

The verdict should come within the next few years, Feng says. Despite the odds stacked against a new discovery, he’s hopeful.

“It’s us against the Standard Model,” he says. “We know there’s something more out there, we just haven’t gotten to it yet. This could be it.”

 

[CarlB]

X(16.7) as the Solution of NuTeV Anomaly
Yi Liang, Long-Bin Chen and Cong-Feng Qiao
School of Physics, University of Chinese Academy of Sciences, CAS Center for Excellence in Particle Physics
Abstract: A recent experimental study of excited 8Be decay to its ground state reveals an anomaly in the final states angle distribution. This exceptional result is attributed to a new vector gauge boson X(16.7). We study the significance of this new boson, especially its effect in anomalies observed in long-lasting experimental measurements. By comparing the discrepancies between the standard model predictions and the experimental results, we manage to find out the values and regions of the couplings of X(16.7) to muon and muon neutrino. In this work, we find that the newly observed boson X(16.7) may be the solution of both NuTeV anomaly and the (g−2)μ puzzle.
...
We will show here that there is room for X boson, if the simple SU(3)xSU(2)xU(1)xU(1) model is adopted.
...
https://arxiv.org/abs/1607.08309

 

[kodama]

X(16.7) as the Solution of NuTeV Anomaly
Yi Liang, Long-Bin Chen and Cong-Feng Qiao
School of Physics, University of Chinese Academy of Sciences, CAS Center for Excellence in Particle Physics
Abstract: A recent experimental study of excited 8Be decay to its ground state reveals an anomaly in the final states angle distribution. This exceptional result is attributed to a new vector gauge boson X(16.7). We study the significance of this new boson, especially its effect in anomalies observed in long-lasting experimental measurements. By comparing the discrepancies between the standard model predictions and the experimental results, we manage to find out the values and regions of the couplings of X(16.7) to muon and muon neutrino. In this work, we find that the newly observed boson X(16.7) may be the solution of both NuTeV anomaly and the (g−2)μ puzzle.
...
We will show here that there is room for X boson, if the simple SU(3)xSU(2)xU(1)xU(1) model is adopted.
...
https://arxiv.org/abs/1607.08309

ur impression

 

[CarlB]

The authors have a lot of other arXiv papers so I suppose they know what they're doing.

Every now and then the experimentalists say something different from the expected and it attracts the attention of theoreticians. This attention happens whether the experiment is right or wrong. If experimentalists never made mistakes, theoretical physics would be pretty boring.

I really hope they're right because it matches the stuff I'm working on which implies that the full symmetry (before mixing) has to be SU(3)xSU(3)xSU(2)xU(1)xU(1).

 

[kodama]

The authors have a lot of other arXiv papers so I suppose they know what they're doing.

Every now and then the experimentalists say something different from the expected and it attracts the attention of theoreticians. This attention happens whether the experiment is right or wrong. If experimentalists never made mistakes, theoretical physics would be pretty boring.

I really hope they're right because it matches the stuff I'm working on which implies that the full symmetry (before mixing) has to be SU(3)xSU(3)xSU(2)xU(1)xU(1).

what is the stuff ur working on? why SU(3)xSU(3)xSU(2)xU(1)xU(1) ? is this technicolor model?

how would adding susy to the above models change it? i.e how would physics change if there is susy to the 16.7 mev x boson, i know there will be a fermion that will be much heavier.

i.e MSSM, NMSSM, SO(10) GUT and GUT in general if there is a fifth protophobic force 16.7 mev boson

 

[CarlB]

I don't know anything about SUSY, I just go to the talks and read the dumbed-down articles. But I haven't seen anyone talk about the 16.7MeV boson and SUSY. I would think it would be difficult to treat the new boson as a super partner to an already known Standard Model fermion because there would be a bunch of characteristics it would need to meet. And if it were obvious how to do that I'd think someone would have already written it up. Or if they treated it as a regular boson it would mean that there would be another sparticle out there somewhere conveniently too heavy to find.

I shouldn't have mentioned the SU(3)xSU(3)xSU(2)xU(1)xU(1) idea as it's not appropriate in this venue. But I think we can talk about where the symmetry comes from as a matter of the mathematics used in physics. It turns out to be the symmetry of pure density matrices (and therefore state vectors) if their mixed density matrices happen to be members of the complex group algebra C[S_4] (and therefore have the symmetry of that algebra). The cool thing about this complex group algebra is that in addition to specifying the symmetry it also defines the particle content, i.e. which representations are present.

"S_4" is the "symmetric group on 4 objects", i.e. the finite group that consists of the permutations on a set of 4 objects. Since there are 4! = 24 permutations on 4 objects, that's the size of this group. This finite group is equivalent to "octahedral symmetry" which is nicely described in the wikipedia article: https://en.wikipedia.org/wiki/Octahedral_symmetry

A "complex group algebra" is an algebra obtained from a finite group by using the finite group as a complete set of basis vectors for a vector space over the complex numbers. This sounds complicated but it's not. A cheap but very nice physics symmetry book that I bet most elementary particles people either have on their shelf or can borrow from a colleague is "Group Theory and Its Application to Physical Problems" by Morton Hammermesh. People call it "Hammermesh"; look in the index under "group algebra". In my copy (1989) this brings you to page 106. On the web, the complex group algebra is nicely defined on page 42 of Christoph Ludeling's lecture notes "Group Theory (for Physicists)" here: http://www.th.physik.uni-bonn.de/nilles/people/luedeling/grouptheory/data/grouptheorynotes.pdf

In Ludeling's notes (p 43) he writes "We will later see that the regular representation actually contains all irreducible representation." If you read further you will find that the irreducible representations are most conveniently obtained by looking up the "character table" for the finite group. For S_4 there are 5 irreducible representations and these irreducible representations are of dimension 1, 1, 2, 3 and 3. When you translate this into mixed density matrix symmetry you obtain U(1), U(1), SU(2), SU(3), and SU(3) symmetries. There are thousands of good explanations on the web for the symmetries of QM state vectors and essentially none on the symmetries of QM mixed density matrices so it's a nicely unexplored subject. Figuring it out on your own is not hard but isn't completely trivial.

The reason one might want to explore the symmetries of mixed density matrices is well presented in Steven Weinberg's recent (2014) paper "Quantum Mechanics Without State Vectors". It's published at PRA, the arXiv version is here: https://arxiv.org/abs/1405.3483 He writes: "Giving up the definition of the density matrix in terms of state vectors opens up a much larger variety of ways that the density matrix might respond to various symmetry transformations."

 

[kodama]

ok thanks. my ? was if you ad susy to thisRealistic model for a fifth force explaining anomaly in 8Be∗→8Bee+e− Decay
Pei-Hong Gu, Xiao-Gang He
(Submitted on 16 Jun 2016 (v1), last revised 12 Jul 2016 (this version, v5))
A 6.8σ anomaly has been reported in the opening angle and invariant mass distributions of e+e− pairs produced in 8Be nuclear transitions. It has been shown that a protophobic fifth force mediated by a 17MeV gauge boson X with pure vector current interactions can explain the data through the decay of an excited state to the ground state, 8Be∗→8BeX, and then the followed saturating decay X→e+e−. In this work we propose a renormalizable model to realize this fifth force. Although axial-vector current interactions also exist in our model, their contributions cancel out in the iso-scalar interaction for 8Be∗→8BeX. Within the allowed parameter space, this model can alleviate the (g−2)μ anomaly problem and can be probed by the LHCb experiment. Several other implications are discussed.
Comments: RevTex, 9 pages with no figures. New major changes are made to the older version
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
Cite as: arXiv:1606.05171 [hep-ph]

how does it impact mssm nmssm gut's etc

 

[kodama]

Particle Physics Models for the 17 MeV Anomaly in Beryllium Nuclear Decays
Jonathan L. Feng, Bartosz Fornal, Iftah Galon, Susan Gardner, Jordan Smolinsky, Tim M. P. Tait, Philip Tanedo
(Submitted on 11 Aug 2016)
The 6.8σ anomaly in excited 8Be nuclear decays via internal pair creation is fit well by a new particle interpretation. In a previous analysis, we showed that a 17 MeV protophobic gauge boson provides a particle physics explanation of the anomaly consistent with all existing constraints. Here we begin with a review of the physics of internal pair creation in 8Be decays and the characteristics of the observed anomaly. To develop its particle interpretation, we provide an effective operator analysis for excited 8Be decays to particles with a variety of spins and parities and show that these considerations exclude simple models with scalar or pseudoscalar particles. We discuss the required couplings for a gauge boson to give the observed signal, highlighting the significant dependence on the precise mass of the boson and isospin mixing and breaking effects. We present anomaly-free extensions of the Standard Model that contain protophobic gauge bosons with the desired couplings to explain the 8Be anomaly. In the first model, the new force carrier is a U(1)B gauge boson that kinetically mixes with the photon; in the second model, it is a U(1)(B-L) gauge boson with a similar kinetic mixing. In both cases, the models predict relatively large charged lepton couplings ~ 0.001 that can resolve the discrepancy in the muon anomalous magnetic moment and are amenable to many experimental probes. The models also contain vectorlike leptons at the weak scale that may be accessible to near future LHC searches.
Comments: 34 pages + references, 6 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
Report number: UCI-TR-2016-12
Cite as: arXiv:1608.03591 [hep-ph]
(or arXiv:1608.03591v1 [hep-ph] for this version)
Submission history
From: Philip Tanedo [view email]
[v1] Thu, 11 Aug 2016 20:00:01 GMT (1396kb,D)

 

[cube137]

Did Jonathen Feng and company just based it on the Atomki group findings or did they made experiments on their own? Has other group verified it? I found this article:

https://www.quantamagazine.org/20160607-new-boson-claim-faces-scrutiny/

"The Atomki group has produced three previous papers on their beryllium-8 experiments — conference proceedings in 2008, 2012 and 2015. The first paper claimed evidence of a new boson of mass 12 MeV, and the second described an anomaly corresponding to a 13.45-MeV boson. (The third was a preliminary version of the Physical Review Letters paper.) The first two bumps have disappeared in the latest data, collected with an improved experimental setup. “The new claim now is [a] boson with a mass of 16.7 MeV,” Naviliat-Cuncic said. “But they don’t say anything about what went wrong in their previous claims and why we should not take those claims seriously.” One naturally wonders, he said, “Is this value that they quote now going to change in the next four years?”"

 

[kodama]

There is no discovery.

Is it worth digging in your backyard for oil? If there would be oil just below the surface, you would make a lot of money. Did you start digging already? Why not?

“It would be crazy not to do another experiment to check this result,” Rouven Essig, a theoretical physicist at Stony Brook University told Nature News. “Nature has surprised us before!”

http://qz.com/759045/fifth-force-ne...d-be-a-dark-photon/?utm_source=YPL&yptr=yahoo

 

[mfb]

Did Jonathen Feng and company just based it on the Atomki group findings or did they made experiments on their own? Has other group verified it? I found this article:

Feng&co didn't make their own experiment, there has been no replication, combine this with the weird history of past particle claims and yeah... there is something not well understood (which makes a follow-up experiment interesting), but I'm highly confident it is some issue with the experiment, not a new particle.

I linked to the article you referenced in post #2 already.

 

[kodama]

Feng&co didn't make their own experiment, there has been no replication, combine this with the weird history of past particle claims and yeah... there is something not well understood (which makes a follow-up experiment interesting), but I'm highly confident it is some issue with the experiment, not a new particle.

I linked to the article you referenced in post #2 already.

have you had a chance to read his latest paper?

Cite as: arXiv:1608.03591 [hep-ph]

Feng lists a half dozen experiments that is being done now to look for dark photons that can also be retasked to find x-boson. years ago funding was approved to find dark photons via ep colliders. Feng argues they can also look for x-boson and its energy is 16.7mev and he provides specific quantitative predictions that can be checked and falsified. what is your opinion of dark photons?

i ask bc many of the experiments were originally approved several years back solely to find dark photons, including the Hungarian experiment, which can also detect x boson.

 

[mfb]

Feng lists a half dozen experiments that is being done now to look for dark photons that can also be retasked to find x-boson.

There is nothing to be re-tasked. The searches have been there all the time, better searches were planned anyway. And no matter how precise their exclusion limits get, I'm sure Feng&co find some way to tune their parameters to explain the upcoming non-observations, even if the model presented now can be excluded.
I would like to be wrong, but this pattern has happened way too often in the past, even with much more plausible excesses than this one.

what is your opinion of dark photons?

Every specific discovery of BSM physics would surprise me.

 

[kodama]

There is nothing to be re-tasked. The searches have been there all the time, better searches were planned anyway. And no matter how precise their exclusion limits get, I'm sure Feng&co find some way to tune their parameters to explain the upcoming non-observations, even if the model presented now can be excluded.
I would like to be wrong, but this pattern has happened way too often in the past, even with much more plausible excesses than this one.
Every specific discovery of BSM physics would surprise me.

the paper lists several dark photon experiments that can also be used to verify his prediction.
those ep colliders weren't specifically looking for the x-boson at the specific energy of 16.7 mev and specific coupling as detailed in the paper but dark photons, and possibly other physics that requires ep colliders, when they were approved several years back.

for x-boson to explain the anatomki anamoly, there actually isn't much fine tuning Feng et al can do. if they fine tune it too low, then the x-boson would not have been observed in the Hungarian Beryllium Nuclear Decays. roughly only 1 out of a million collisions in the Berylium nuclear decay at an angle of 140 results in the x-boson, so that sets strong constraints on how much fine tuning Feng's proposed model does. in his paper he states several experiments like MIT Darklight searching for dark photons and if they don't find it, then his model is falsified.

this is in the popular news.

other researchers have proposed a large number of anomalies like g2 muon anomaly that can be explained as well as dark matter.

btw the 750 gev did go away as rumors said. do you believe in SUSY?

 

[mfb]

those ep colliders weren't specifically looking for the x-boson at the specific energy of 16.7 mev and specific coupling as detailed in the paper

Right, because there is no reason to do so.

for x-boson to explain the anatomki anamoly, there actually isn't much fine tuning Feng et al can do.

Make its couplings to protons stronger and the coupling to electrons weaker. Give it different couplings to muons and electrons, to different quark generations, ...

do you believe in SUSY?

If you think physics works via beliefs, you are on the wrong track. And as I said already: Every specific discovery of BSM physics would surprise me.

 

[kodama]

Right, because there is no reason to do so.Make its couplings to protons stronger and the coupling to electrons weaker. Give it different couplings to muons and electrons, to different quark generations, ...If you think physics works via beliefs, you are on the wrong track. And as I said already: Every specific discovery of BSM physics would surprise me.

there was no reason to look for it prior to Feng's paper, but there is certainly a reason to do so now. esp since looking for dark photons is
itself a highly speculative concept.
making coupling to protons stronger and coupling electrons weaker, and its no longer the protophobic boson Feng originally proposed.

since there's no evidence for SUSY and there are theoretical difficulties with SUSY, yes i do think physics, esp theoretical physics involving energies that cannot be probed, does work on beliefs. string theorists have faith in SUSY. string theorists have beliefs in higher dimensions. they have a belief if you could construct a Planck scale accelerator, it would validate string theory and SUSY

 

[mfb]

but there is certainly a reason to do so now

Apart from Feng et al and you I don't see anyone seeing that reason.

making coupling to protons stronger and coupling electrons weaker, and its no longer the protophobic boson Feng originally proposed.

Sorry, mixed protons and neutrons. Make its coupling to neutrons stronger then.

yes i do think physics, esp theoretical physics involving energies that cannot be probed, does work on beliefs.

It does not. The theorists are exploring "what if". They hope to be right, but that is a different statement.