New anomaly observed in 12C X17

[kodama]

TL;DR Summary

New anomaly observed in 12C supports the existence and the vector character of the hypothetical X17 boson

there is a new paper this time on C12

[Submitted on 22 Sep 2022]

New anomaly observed in 12C supports the existence and the vector character of the hypothetical X17 boson​

A.J. Krasznahorkay, A. Krasznahorkay, M. Begala, M. Csatlós, L. Csige, J. Gulyás, A. Krakó, J. Timár, I. Rajta, I. Vajda, N.J. Sas

Employing the 11B(p,γ)12C nuclear reaction, the angular correlation of e+e− pairs was investigated in the angular range of 40∘Θ≤175∘ for five different proton energies between Ep = 1.5 - 2.5 MeV. At small angles (Θ≤120∘), the results can be well interpreted by the internal pair creation process of electromagnetic radiations with E1 and M1 multipolarities and by the external pair creation in the target backing. However, at angles greater than 120∘, additional count excess and anomalies were observed, which could be well accounted for by the existence of the previously suggested hypotetical X17 particle. Our results show that the X17 particle was generated mainly in E1 radiation. The derived mass of the particle is mXc2=16.86±0.17(stat)±0.20(syst) MeV. According to the mass, and to the derived branching ratio (Bx=3.4(3)×10−6), this is likely the same X17 particle, which we recently suggested for describing the anomaly observed in the decay of 8Be and 4He.

Comments:	5 pages, 4 figures. arXiv admin note: text overlap with arXiv:2104.10075, arXiv:2205.07744, arXiv:1910.10459
Subjects:	Nuclear Experiment (nucl-ex); High Energy Physics - Experiment (hep-ex)
Cite as:	arXiv:2209.10795 [nucl-ex]

This team found similar results in the decay of 8Be and 4He and now 12C with similar mass of 17 MeV

Are these results reproducible? Do you think if another research team were to use the same elements and equipment and same method would get the same results?

 

[Vanadium 50]

The situation hasn't changed since Wednesday.

`1. There are two A. Krasznahorkay's - it's probably best to make clear this is A. Krasznahorkay, pere. (Although Krasznahorkay fils is on at least one paper)

2. Nobody but Krasznahorkay has been able to replicate this. (You can see the attempts by looking at papers that cite this result)

3. A paper by A. Aleksejevs et a. shows that the structure is what is predicted by higher order QED correction when data is restricted to the ATOMKI kinematic regions.

 

[kodama]

The situation hasn't changed since Wednesday.

`1. There are two A. Krasznahorkay's - it's probably best to make clear this is A. Krasznahorkay, pere. (Although Krasznahorkay fils is on at least one paper)

2. Nobody but Krasznahorkay has been able to replicate this. (You can see the attempts by looking at papers that cite this result)

3. A paper by A. Aleksejevs et a. shows that the structure is what is predicted by higher order QED correction when data is restricted to the ATOMKI kinematic regions.

#2

there are plenty of papers that attempt to find X17 using electron or positron colliders with no success.I've not seen any papers that attempt to use Be, He, or C and same or similar experiment as these authors to reproduce these results, using those elements, if there any could you point to one thanks?#3 there are of course other papers a recent one suggesting it could be explain by Z' boson

 

[Vanadium 50]

The structure, in the original experiment, is predicted by the Standard Model. Aleksejevs at colleagues shows that it's only anomalous if you a) ignore higher order terns and b) look in a particular and very restricted region of phase space. Move along, nothing to see here.

Now, if youn want to argue that on top of that, there's also a peak in another experiment that just happens to be conducted by the same guy as the first one, and this one happens top be at exactly the same mass as the original - only this one is from a new particle, well, you're welcome to your opinion.

 

[kodama]

The structure, in the original experiment, is predicted by the Standard Model. Aleksejevs at colleagues shows that it's only anomalous if you a) ignore higher order terns and b) look in a particular and very restricted region of phase space. Move along, nothing to see here.

Now, if youn want to argue that on top of that, there's also a peak in another experiment that just happens to be conducted by the same guy as the first one, and this one happens top be at exactly the same mass as the original - only this one is from a new particle, well, you're welcome to your opinion.

this paper,

[Submitted on 1 Feb 2021 (v1), last revised 7 Apr 2021 (this version, v2)]

A Standard Model Explanation for the "ATOMKI Anomaly"​

A. Aleksejevs, S. Barkanova, Yu.G. Kolomensky, B. Sheff

Using the e+e− pair spectrometer at the 5 MV Van de Graaff accelerator at the Institute for Nuclear Research, Hungarian Academy of Sciences (ATOMKI), Krasznahorkay et al. have claimed a 6.8σ excess at high e+e− opening angles in the internal pair creation isoscalar transition 8Be(18.15)→8Bee+e−. A hypothetical gauge boson with the mass circa 17 MeV, "X17", has been proposed as an explanation for the excess. We show that the observed experimental structure can be reproduced within the Standard Model by adding the full set of second-order corrections and the interference terms to the Born-level decay amplitudes considered by Krasznahorkay et al. We implement a detailed model of the ATOMKI detector, and also show how experimental selection and acceptance bias exacerbate the apparent difference between the experimental data and the Born-level prediction.

Comments:	7 pages, 10 figures. v2 corrects small typos and replaces images with vector graphics
Subjects:	High Energy Physics - Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
Cite as:	arXiv:2102.01127 [hep-ph]

only claims that 6.8σ excess at high e+e− opening angles in the internal pair creation isoscalar transition 8Be(18.15)→8Bee+e−. could be explained by second order corrections.

it doesn't address the He and now C and more recent paper on proton capture of Be, whether these additional findings could also be explained by similar QED second order corrections.

arXiv:2102.01127

on page 5 under conclusion the author states out X17 as an explanation is not required only that caution should be used and additional experiments are needed and gives specifics

 

[Vanadium 50]

"It's a new particle."
"It's a ghost. Nobody can reproduce it, and the SM says you should see an artifact there."
"OK, so maybe that one was a mistake - but the same people and only the same people have seen a bump at the same mass as the first non-particle!"
Later, rinse and repeat.

Sorry, I have better things to do than chase ghosts. You know, actual science.

 

[kodama]

Why are there proposals for an extra U(1) symmetry and another additional scalar field and another Z boson called U(1)' and Z' boson.

What are U(1)' and Z' boson supposed to solve that the standard model does not?

the reason I ask is this paper,

High Energy Physics - Phenomenology​

[Submitted on 19 Sep 2022]

Light Z′ Signatures at the LHC​

Yaşar Hiçyılmaz, Shaaban Khalil, Stefano Moretti

We propose a theoretical framework embedding a spontaneously broken U(1)′ symmetry in addition to the Standard Model (SM) gauge group, from which a very light Z′ state emerges, with both vector and axial (non-universal) couplings to fermions, able to explain the so-called Atomki anomaly, compliant with current measurements of the Anomalous Magnetic Moments (AMMs) of electron and muon as well as beam dump experiments while providing a distinctive pp→Higgs→Z′Z′→4l (l=e,μ) signal at the Large Hadron Collider (LHC), where the `Higgs' label refers to the SM-like Higgs state discovered in 2012 or a lighter one. We finally show that the cross section for this process should be sufficiently large to afford one with significant sensitivity during Run 3 of the LHC.

Subjects:	High Energy Physics - Phenomenology (hep-ph)
Cite as:	arXiv:2209.09226 [hep-ph]

his proposal is that X17 is actually a Z' boson, which implies additional scalar field and a spontaneously broken U(1)′ symmetry, i.e the Z' boson is 17 MeV and has non-universal couplings.

Is Z' boson to be more plausible explanation for Atomki anomaly, than X17?

What are the implications of additional a new neutral scalar boson to particle physics as required to break U(1)′ symmetry ?

How does adding SUSY to Z' and U(1)′ symmetry and one more neutral scalar field change the MSSM?The new scalar field is to break U(1)′ symmetry to a Z' boson.

This paper references several prior papers that discuss break U(1)′ symmetry to a Z' boson

The paper states

"while providing a distinctive pp→Higgs→Z′Z′→4l (l=e,μ) signal at the Large Hadron Collider (LHC), where the `Higgs' label refers to the SM-like Higgs state discovered in 2012 or a lighter one. We finally show that the cross section for this process should be sufficiently large to afford one with significant sensitivity during Run 3 of the LHC."

The LHC should find this in Run 3,

one thing unclear is whether standard electron-position colliders looking for X17 would also find Z' boson, as the paper makes no mention, for example, of PADME or DarkLight experiments attempting to find X17 via electron or positons.

other papers on U(1)′ symmetry to a Z' boson

High Energy Physics - Phenomenology​

[Submitted on 4 Mar 2020 (v1), last revised 19 Mar 2020 (this version, v2)]

Light Z′ and Dark Matter from U(1)X Gauge Symmetry​

Nobuchika Okada, Satomi Okada, Qaisar Shafi

We consider a U(1)X gauge symmetry extension of the Standard Model (SM) with a Z′-portal Majorana fermion dark matter that allows for a relatively light gauge boson Z′ with mass of 10 MeV− a few GeV and a much heavier dark matter through the freeze-in mechanism. In a second scenario the roles are reversed, and the dark matter mass, in the keV range or so, lies well below the Z′ mass, say, ∼1 GeV. We outline the parameter space that can be explored for these two scenarios at the future Lifetime Frontier experiments including Belle-II, FASER, LDMX and SHiP.

Comments:	18 pages, 4 figures, new references added, typos corrected
Subjects:	High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Experiment (hep-ex)
Cite as:	arXiv:2003.02667 [hep-ph]

Model for a Light Z' Boson​

R. Foot, X.-G. He, H. Lew, R. R. Volkas

A model of a light Z′ boson is constructed and phenomenological bounds are derived. This Z′ boson arises from a very simple extension to the Standard Model, and it is constrained to be light because the vacuum expectation values which generate its mass also break the electroweak gauge group. It is difficult to detect experimentally because it couples exclusively or primarily (depending on symmetry breaking details) to second and third generation leptons. However, if the Z′ boson is sufficiently light, then there exists the possibility of the two-body decay τ→μZ′ occurring. This will provide a striking signature to test the model.

Comments:	20 pages + 5 pages of figures (appended as postscipt files), LaTeX, OITS-532
Subjects:	High Energy Physics - Phenomenology (hep-ph)
Cite as:	arXiv:hep-ph/9401250

A Light Z′ Boson​

Xiao-Gang He

A model of a light Z′ boson based on gauged Lμ−Lτ U(1) symmetry is constructed. The Z′ boson mass is constrained to be in the range of 0.8 to 1 GeV from Z and Z′ mass relation, g-2 of muon, and tau decays. The two body decay τ→μZ′ is possible. This will provide a striking signature to test the model. Talk presented at the Eighth Meeting of the American Physical Society, Division of Particles and Fields (DPF'94), Albuqurque, New Mexico, August 2-6, 1994.

Comments:	7pages, REvtex, OITS-549
Subjects:	High Energy Physics - Phenomenology (hep-ph)
Cite as:	arXiv:hep-ph/9409237

 

[berkeman]

Thread locked for Moderation.

 

[PeterDonis]

Moderator's note: Two threads on same topic consolidated into one. Thread reopened.

 

[mitchell porter]

What are U(1)' and Z' boson supposed to solve that the standard model does not?

Big BSM theories often contain a Z'. So it's usually a side effect of some grander design, rather than specifically postulated to explain something.

 

[kodama]

Big BSM theories often contain a Z'. So it's usually a side effect of some grander design, rather than specifically postulated to explain something.

why's there Models with a new U(1) gauge symmetry?

 

[mitchell porter]

why's there Models with a new U(1) gauge symmetry?

See previous comment. Breaking a new U(1) gauge symmetry is probably the most common way to get a Z' boson in a model.

 

[kodama]

See previous comment. Breaking a new U(1) gauge symmetry is probably the most common way to get a Z' boson in a model.

is Light Z′ better than x17?

 

[ohwilleke]

None of the linked papers are well motivated because the Atomki anomaly/X17 justifying anomalies aren't real, and there are no other unexplained observations that are more than just fluke experimental uncertainties that a Z' would be well suited to explaining.

 

[Vanadium 50]

Model for a Light Z' Boson

As suggested by the exerpt and explicitly stated on the top of Page 2, this model does not have the Z' decaying to e+e- pairs, so in no way can it explain the ATOMKI results, Naughty naughty!

 

[kodama]

​

[Submitted on 14 Mar 2017]

Can nuclear physics explain the anomaly observed in the internal pair production in the Beryllium-8 nucleus?​

Xilin Zhang, Gerald A. Miller

Recently the experimentalists in [PRL 116, 042501 (2016)] announced observing an unexpected enhancement of the electron-positron pair production signal in one of the Beryllium-8 nuclear transitions. The following studies have been focused on possible explanations based on introducing new types of particle. In this work, we improve the nuclear physics modeling of the reaction by studying the pair emission anisotropy and the interferences between different multipoles in an effective field theory inspired framework, and examine their possible relevance to the anomaly. The connection between the previously measured on-shell photon production and the pair production in the same nuclear transitions is established. These improvements, absent in the original experimental analysis, should be included in extracting new particle's properties from the experiment of this type. We then study the possibility of using the nuclear transition form factor to explain the anomaly. The reduction of the anomaly's significance by simply rescaling our predicted event count is also investigated.

Comments:	8 pages, 7 figures, 3 tables
Subjects:	Nuclear Theory (nucl-th); High Energy Physics - Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
Report number:	NT@UW-17-04
Cite as:	arXiv:1703.04588 [nucl-th]

​

Data details​

In 2017, theorists Gerald Miller at the University of Washington and Xilin Zhang at Ohio State concluded that, if the Atomki data are correct, the original 8Be excess cannot be explained by nuclear-physics modelling uncertainties. But they also wrote that a direct comparison to the e+e– data is not feasible due to “missing public information” about the experimental detector efficiency. “Tuning the normalisation of our results reduces the confidence level of the anomaly by at least one standard deviation,” says Miller. As for the latest Atomki result, the nuclear physics in 4He is more complicated than 8Be because two nuclear levels are involved, explains Miller, making it difficult to carry out an analysis analogous to the 8Be one. “For 4He there is also a background pair- production mechanism and interference effect that is not mentioned in the paper, much of which is devoted to the theory and other future experiments,” he says. “I think the authors would have been better served if they presented a fuller account of their data because, ultimately, this is an experimental issue. Confirming or refuting this discovery by future nuclear experiments would be extremely important. A monumental discovery could be possible.”

https://cerncourier.com/a/rekindled-atomki-anomaly-merits-closer-scrutiny/

 

[kodama]

we should see answers sooner than we thought​

​

High Energy Physics - Experiment​

[Submitted on 29 Sep 2022]

Dark sector studies with the PADME experiment​

A.P. Caricato, M. Martino, I. Oceano, S. Spagnolo, G. Chiodini, F. Bossi, R. De Sangro, C. Di Giulio, D. Domenici, G. Finocchiaro, L.G. Foggetta, M. Garattini, A. Ghigo, P. Gianotti, T. Spadaro, E. Spiriti, C. Taruggi, E. Vilucchi, V. Kozhuharov, S. Ivanov, Sv. Ivanov, R. Simeonov, G. Georgiev, F. Ferrarotto, E. Leonardi, P. Valente, E. Long, G.C. Organtini, G. Piperno, M. Raggi, S. Fiore, P. Branchini, D. Tagnani, V. Capirossi, F. Pinna, A. Frankenthal

The Positron Annihilation to Dark Matter Experiment (PADME) uses the positron beam of the DAΦNE Beam-Test Facility, at the Laboratori Nazionali di Frascati (LNF) to search for a Dark Photon A′. The search technique studies the missing mass spectrum of single-photon final states in e+e−→A′γ annihilation in a positron-on-thin-target experiment. This approach facilitates searches for new particles such as long lived Axion-Like-Particles, protophobic X bosons and Dark Higgs. This talk illustrated the scientific program of the experiment and its first physics results. In particular, the measurement of the cross-section of the SM process e+e−→γγ at s√=21 MeV was shown.

Subjects:	High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
Cite as:	arXiv:2209.14755 [hep-ex]