I would be extremely surprised if the existence of a new hypothetical X17 particle was confirmed. This paper supports that skepticism.
Recent findings of an unexpected, narrow resonance in the e+e− decay spectra of excited states of 8Be, 4He and 12C by the ATOMKI collaboration have received considerable experimental and theoretical attention, whereby a new, 17-MeV vector-like or axial-vector-like boson termed X17 was conjectured as an explanation of the anomaly.
Further analysis of all existing constraints disfavors a vector X17 scenario.
For a similar analysis of the axial-vector scenario, a calculation of the reduced matrix element of a spin-dipole operator between the excited nuclear state C(17.23) and the carbon ground state is required. In the present work, we compute the aforementioned reduced matrix element under the assumption that the state C(17.23) is well represented by the 2s1/21p−13/2 particle-hole shell-model excitation of the ground state, as supported by experimental data. Within such a framework, our results indicate that, like the vector scenario, the axial-vector interpretation of X17 shows strong tensions with the other existing constraints on the nucleon coupling of a conjectured X17.
Cornelis J.G. Mommers, Marc Vanderhaeghen, "Constraining the axial-vector X17 interpretation with 12C data" arXiv:2406.08143 (June 12, 2024).
5 comments:
arXiv:2406.07643 (hep-ph)
[Submitted on 11 Jun 2024]
A 17 MeV pseudoscalar and the LSND, MiniBooNE and ATOMKI anomalies
Waleed Abdallah, Raj Gandhi, Tathgata Ghosh, Najimuddin Khan, Samiran Roy, Subhojit Roy
In the absence of any new physics signals at the Large Hadron Collider (LHC), anomalous results at low energy experiments have become the subject of increased attention and scrutiny. We focus on three such results from the LSND, MiniBooNE (MB), and ATOMKI experiments. A 17 MeV pseudoscalar mediator (a′) can account for the excess events seen in 8Be and 4He pair creation transitions in ATOMKI. We incorporate this mediator in a gauge invariant extension of the Standard Model (SM) with a second Higgs doublet and three singlet (seesaw) neutrinos (Ni,i=1,2,3). N1,2 participate in an interaction in MB and LSND which, with a′ as mediator, leads to the production of e+e− pairs. The Ni also lead to mass-squared differences for SM neutrinos in agreement with global oscillation data. We first show that such a model offers a clean and natural joint solution to the MB and LSND excesses. We then examine the possibility of a common solution to all three anomalies. Using the values of the couplings to the quarks and electrons which are required to explain pair creation nuclear transition data for 8Be and 4He in ATOMKI, we show that these values lead to excellent fits for MB and LSND data as well, allowing for a common solution. We obtain a representative solution space for this, in the context of an important constraint that comes from the decay K+→π+a′(a′→e+e−). We also discuss other constraints on the model from both collider and non-collider experiments as well as those from electroweak precision data, stability and unitarity. We compute the contributions to the electron and muon g−2 up to two loops for our model and discuss the results in the context of the current theoretical and empirical scenario vis a vis these parameters. Finally, we discuss future tests of the model in upcoming experiments.
Comments: 39 pages, 6 figures and 3 tables
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
Report number: HRI-RECAPP-2024-02
Cite as: arXiv:2406.07643 [hep-ph]
there are many hypothesis of x17 if it exists and 17 MeV pseudoscalar mediator isn't rule out yet
MEG II experiment and PADME and Montréal should have more important results specifically for x17. hopefully all 3 agree
with the absence of any new physics signals at the Large Hadron Collider (LHC), i think x17 is possible the best way to get any new physics signals in our lifetime
I don't know where I could post this, so here:
https://www.quora.com/The-world-turtle-was-a-common-belief-that-the-land-people-lived-on-was-on-the-back-of-a-giant-turtle-Its-seen-everywhere-from-Eastern-cultures-and-even-Native-American-ones-across-the-Americas-Why-is-this?ch=10&oid=103914707&share=fa29a6c8&srid=RPhZF&target_type=question
Author of Quora post is from Papua New Guinea, now a student in China.
@DDeden Thanks for the link, anything about Turtle Island myths is welcome at this blog for obvious reasons. I think I have an image that sheds some light on the idea in some old post.
The images is at https://dispatchesfromturtleisland.blogspot.com/2018/11/turtle-island.html
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