7Li(p,e+e−)8Be direct proton-capture reaction X17

[kodama]

TL;DR Summary

significance of 7Li(p,e+e−)8Be direct proton-capture reaction

What is the significance of

7Li(p,e+e−)8Be direct proton-capture reaction ?​

there are these papers,

Slope of the astrophysical S factor for the 7Li(p,γ)8Be reaction​

• January 2000
• https://www.researchgate.net/journal/Physical-Review-C-1089-490X 61(1):15802-

DOI:10.1103/PhysRevC.61.015802

The​

reaction and single-particle levels in 8Be​

Author links open overlay panelJerry B.MarionMarkWilson†

Abstract​

The
reaction has been studied by observing the α particles from the decay of the 8Be levels at 16.62 and 16.92 MeV by means of a magnetic spectrometer. The yields to both levels are resonant at Ep = 0.44 MeV, the well-known (p, γ) resonance. In addition, the 16.62 MeV level is populated by a direct capture process, confirming the expectation based on 7Li(d, n)8Be threshold and stripping measurements that this level is a single-proton state.

Reaction rate of the 7Li(p,γ)8Be radiative capture at low energies​

Author links open overlay panelS.B.Dubovichenkoab
A.V.Dzhazairov-KakhramanovaN.A.Burkovab

Abstract​

Within the framework of the modified potential cluster model with the classification of orbital states according to Young diagrams, the possibility of description experimental data for S-factor of the proton radiative capture on 7Li to the ground state of 8Be is considered. It was shown that taking into account E1 and M1 transitions from the state of
Li scattering to the ground

• An intense proton beam diagnostic using the 7Li(p,γ)8Be →141Pr(γ,n)140Pr(β+) nuclear reaction sequence

Review of Scientific Instruments 66, 309 (1995); https://doi.org/10.1063/1.1146393

C. Brad Evans and G. W. Cooper

• Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico 87131

C. L. Ruiz and R. J. Leeper

so there is some experimental interest in this reaction.

The reason I ask is this new paper

Nuclear Experiment​

[Submitted on 16 May 2022]

Observation of the X17 anomaly in the 7Li(p,e+e−)8Be direct proton-capture reaction​

N.J. Sas, A.J. Krasznahorkay, M. Csatlós, J. Gulyás, B. Kertész, A. Krasznahorkay, J. Molnár, I. Rajta, J. Timár, I. Vajda, M.N. Harakeh

Angular correlation spectra of e+e− pairs produced in the 7Li(p,γ)8Be nuclear reaction have been studied at the sharp Ep= 441 keV resonance as well as at Ep= 650 keV, 800 keV and 1100 keV proton beam energies. The spectra measured at the resonance can be understood through the M1 internal pair creation process, but in the case of the off-resonance regions (direct proton capture) significant anomalies were observed in the e+e− angular correlations supporting the X17 hypothetical particle creation and decay.

Cite as:

arXiv:2205.07744 [nucl-ex]

same group, but it seems that 3 different experiments,

nuclear transition of beryllium-8 atoms and in stable helium atoms

and now, the 7Li(p,e+e−)8Be direct proton-capture reaction

all have the same X17 anomaly.

granted it is from same research group, but how hard would it be for other research groups to verify these results?

if other experimental groups also see the same results, that's 3 very different nuclear reactions all having the same x17 anomaly.

there's also this

[Submitted on 8 Aug 2022]

Searching for New Physics with DarkLight at the ARIEL Electron-Linac​

E Cline (for the DarkLight Collaboration)

The search for a dark photon holds considerable interest in the physics community. Such a force carrier would begin to illuminate the dark sector. Many experiments have searched for such a particle, but so far it has proven elusive. In recent years the concept of a low mass dark photon has gained popularity in the physics community. Of particular recent interest is the 8Be and 4He anomaly, which could be explained by a new fifth force carrier with a mass of 17 MeV/c2. The proposed DarkLight experiment would search for this potential low mass force carrier at ARIEL in the 10-20 MeV e+e− invariant mass range. This proceeding will focus on the experimental design and physics case of the DarkLight experiment.

Comments:	7 pages, 4 figures, to be submitted as part of the proceedings on "New Scientific Opportunities with the TRIUMF ARIEL e-linac"
Subjects:	Nuclear Experiment (nucl-ex); Instrumentation and Detectors (physics.ins-det)
Cite as:	arXiv:2208.04120 [nucl-ex]

way back in 2015 https://en.wikipedia.org/w/index.php?title=Attila_Krasznahorkay&action=edit&redlink=1 and his colleagues reported his first result on beryllium-8 nuclear transitions

it's 2022 and AFAIK there's no independent confirmation using beryllium-8

and then 2019 the same anomalies in the decay of stable helium atoms

again in 2022 and AFAIK there's no independent confirmation using the decay of stable helium atoms

in 2022 7Li(p,e+e−)8Be direct proton-capture reaction gives rise to anomalies that can be explained by X17

 

[Astronuc]

Summary: significance of 7Li(p,e+e−)8Be direct proton-capture reaction

What is the significance of

7Li(p,e+e−)8Be direct proton-capture reaction ?​

The existence of X17, "a hypothetical subatomic particle proposed by Attila Krasznahorkay" and his colleagues at ATOMKI, the Hungarian Institute for Nuclear Research, "to explain certain anomalous measurement results" observed with the fission of ⁸Be into 2 alpha particles. ⁸Be is inherently unstable.

The significance of ⁷Li(p,e+e−)⁸Be is that it is a possible decay mode, possibly related to the well established (Marion and Wilson, 1966) reaction ⁷Li(p,γ)⁸Be. The hypothesis of X17 is controversial. A pair (e⁺e^-) can be produced by photon interaction with a nucleus.

https://en.wikipedia.org/wiki/X17_particle
Note - https://en.wikipedia.org/wiki/X17_particle#Skepticism
https://en.wikipedia.org/wiki/S-factor

Both p (H) and ⁷Li occur in Nature and on Earth. ⁷Li is produced in a variety of nuclear reactions, including neutron capture by ⁶Li, decay of ⁷Be by electron capture, and various fusion reactions, e.g., d + ⁶Li -> ⁷Li + p, or d + ⁶Li -> ⁷Be + n, from which decay of ⁷Be would occur.

 

[kodama]

The existence of X17, "a hypothetical subatomic particle proposed by Attila Krasznahorkay" and his colleagues at ATOMKI, the Hungarian Institute for Nuclear Research, "to explain certain anomalous measurement results" observed with the fission of ⁸Be into 2 alpha particles. ⁸Be is inherently unstable.

The significance of ⁷Li(p,e+e−)⁸Be is that it is a possible decay mode, possibly related to the well established (Marion and Wilson, 1966) reaction ⁷Li(p,γ)⁸Be. The hypothesis of X17 is controversial. A pair (e⁺e^-) can be produced by photon interaction with a nucleus.

https://en.wikipedia.org/wiki/X17_particle
Note - https://en.wikipedia.org/wiki/X17_particle#Skepticism
https://en.wikipedia.org/wiki/S-factor

Both p (H) and ⁷Li occur in Nature and on Earth. ⁷Li is produced in a variety of nuclear reactions, including neutron capture by ⁶Li, decay of ⁷Be by electron capture, and various fusion reactions, e.g., d + ⁶Li -> ⁷Li + p, or d + ⁶Li -> ⁷Be + n, from which decay of ⁷Be would occur.

is this a third line of evidence for x17?

 

[Astronuc]

is this a third line of evidence for x17?

Not necessarily. The existence of such a particle is speculative, but folks are theorizing and apparently devising experiments to explore such a particle. If it can be explained by 'known' or 'current SM physics models', then the answer would be 'no'.

Here is a Scientific American article on the Hungarian research from 2019. At the time, the ATOMKI work had not been peer-reviewed.

In a paper posted on the preprint server arXiv.org, which has not yet been peer-reviewed, Attila Krasznahorkay of the Institute for Nuclear Research (also known as Atomki) at the Hungarian Academy of Sciences and his colleagues report the new findings. Back in 2015 the team observed the decay of beryllium-8 nuclei and found that pairs of electrons and positrons (electrons’ antimatter counterparts) ejected in the process were consistent with the additional decay of a mysterious extra particle, the X17 particle, with a mass of about 17 million electron volts (MeV). Now the researchers say they have seen evidence for this particle again but this time in the decay of helium-4 nuclei. “We studied the decay of high-energy nuclear states, first of all in beryllium-8 and then, more recently, in helium-4,” Krasznahorkay says. “We got a short difference between the prediction and the experimental data, an anomaly. In order to understand this anomaly, we assumed a new particle, which is created in the atomic nucleus and ejected, then decays to electron-positron pairs.”

https://www.scientificamerican.com/...17-particle-reported-but-scientists-are-wary/

I should point out that the Q-value for the p +⁷Li -> 2α is 17.5 MeV. The proton needs sufficient energy to overcome the Coulomb barrier of the ⁷Li nucleus, so there would be some additional energy involved with the products. In some cases, some of the energy may be emitted as γ, as in (p,γ) reaction, or in the case of the ATOMKI research, as e⁺e^- pairs. Then the question becomes, is the production of e⁺e^- due to the decay of X17, or an interaction of a γ with either the ⁸Be or an α-particle.

 

[kodama]

Back in 2015, its 2022 how difficult is it to confirm this report by independent physics research ?

 

[Astronuc]

Back in 2015, its 2022 how difficult is it to confirm this report by independent physics research ?

Please read the articles I cited.

In the Scientific American article:

Since the Hungarian team published its first paper back in 2015, other scientists have tried and failed to find evidence for the X17 particle. An outside analysis in 2016, however, suggested that if this particle truly exists, it could be evidence for a supposed “fifth force” of nature, specifically related to dark matter. “This fifth force really means there is a new particle that intermediates new interactions, or new forces,” says Daniele Alves, a particle physicist at Los Alamos National Laboratory, who was not involved in the Hungarian team’s work. “It’s possible that this particle is part of a larger ‘dark sector,’ meaning it could also interact with dark matter particles. It could be a portal to this sector.”

Matt Strassler, a theoretical physicist at Harvard University, who also wasn’t involved in Hungarian team’s studies, notes this particle would be “a window into some aspect of the universe that we are completely unaware of,” with huge implications. “Not only would it be obviously Nobel Prize–winning because it would be a new [fundamental] particle, but this particular particle doesn’t fit into the existing table of particles,” he says. “The Standard Model, all of the existing elementary particles, form sort of a closed book. [But] X17 interacts with matter much more weakly. And that’s an indication that it’s not part of the structure of the Standard Model. Its interactions with matter are through some other story we don’t know yet.”

It takes time to devise an experiment and either build the equipment or get 'beam time' from an appropriate facility. There may be other priorities, and one might have to wait. Furthermore, if there is indeed skepticism about some experimental results or underlying theory, such an experiment may receive low priority compared to other experiments.

 

[kodama]

Please read the articles I cited.

In the Scientific American article:It takes time to devise an experiment and either build the equipment or get 'beam time' from an appropriate facility. There may be other priorities, and one might have to wait. Furthermore, if there is indeed skepticism about some experimental results or underlying theory, such an experiment may receive low priority compared to other experiments.

is anyone attempting to reproduce the results ?

 

[Vanadium 50]

`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.

​