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

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Main Question or Discussion Point

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.

Answers and Replies

Related Beyond the Standard Model News on Phys.org
mfb
Mentor
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.

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

mfb
Mentor
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.

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
Mentor
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.

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
Mentor
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.
Blog article said:
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.

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
Mentor
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.

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

mfb
Mentor
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
Mentor
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.

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
Mentor
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.

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
Mentor
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.

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
Mentor
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
Science Advisor
Homework Helper
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.

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.

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)

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)