I Updates on the experiments X17

[kodama]

TL;DR Summary

. Assuming the ATOMKI evaluation of the electron-pair production rate from X17

your thoughts on this -- Status of the X17 search in Montreal

they'll verify or refute a clear signal after about two weeks of data taking with a 2 μA proton beam

if Montreal Tandem accelerator confirm X17 a clear signal after about two weeks of data taking with a 2 μA proton beam would you accept it ? when it is ready - data 2023

ARIEL experiments and theory and The Positron Annihilation to Dark Matter Experiment also seeking X17 not sure when it is ready[Submitted on 21 Nov 2022]

Status of the X17 search in Montreal​

G. Azuelos, B. Broerman, D. Bryman, W.C. Chen, H.N. da Luz, L. Doria, A. Gupta, L-A. Hamel, M. Laurin, K. Leach, G. Lefebvre, J-P. Martin, A. Robinson, N. Starinski, R. Sykora, D. Tiwari, U. Wichoski, V. Zacek

At the Montreal Tandem accelerator, an experiment is being set up to measure internal pair creation from the decay of nuclear excited states using a multiwire proportional chamber and scintillator bars surrounding it from the DAPHNE experiment. The acceptance covers a solid angle of nearly 4π. Preamplifiers and the data acquisition hardware have been designed and tested. The water-cooled 7LiF target, mounted on an Al foil is in a thin carbon fiber section of the beamline. The experiment will focus at first on a measurement of the internal pair creation from the 18.15 MeV state of 8Be. Assuming the ATOMKI evaluation of the electron-pair production rate from X17, a Geant4 simulation predicts observation of a clear signal after about two weeks of data taking with a 2 μA proton beam. The IPC measurement could eventually be extended to the giant dipole resonance of 8Be, as well as to other nuclei, in particular to 10B.

Comments:	5 pages, 4 figures, Proceedings contribution, TRIUMF Ariel Workshop, May 25-27 2022
Subjects:	Instrumentation and Detectors (physics.ins-det); Nuclear Experiment (nucl-ex)
Cite as:	arXiv:2211.11900 [physics.ins-det]
	(or arXiv:2211.11900v1 [physics.ins-det] for this version)
	https://doi.org/10.48550/arXiv.2211.11900

[Submitted on 16 Oct 2022]
ARIEL experiments and theory
Petr Navratil

I present an overview of experiments at TRIUMF ARIEL and ISAC facilities covering both the current and the future envisioned programs. I also briefly review theory program at TRIUMF that relates to the ARIEL experimental program. I highlight several recent experimental results from the nuclear astrophysics, nuclear structure, fundamental symmetries, and the sterile neutrino search. Finally, I mention ongoing theoretical ab initio calculations of the proton capture on 7Li related to the X17 boson observation.

Comments: Contribution to proceedings of the workshop New Scientific Opportunities with the TRIUMF ARIEL e-linac, 10 pages, 5 figures
Subjects: Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
Cite as: arXiv:2210.08438 [nucl-th]

[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]

[Submitted on 22 Sep 2022 (v1), last revised 1 Nov 2022 (this version, v2)]
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 = 1.50 - 2.50 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=17.03±0.11(stat)±0.20(syst) MeV. According to the mass, and to the derived branching ratio (Bx=3.6(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

[Submitted on 19 Sep 2022]
Resonant search for the X17 boson at PADME
Luc Darmé, Marco Mancini, Enrico Nardi, Mauro Raggi

We discuss the experimental reach of the Frascati PADME experiment in searching for new light bosons via their resonant production in positron annihilation on fixed target atomic electrons. A scan in the mass range around 17 MeV will thoroughly probe the particle physics interpretation of the anomaly observed by the ATOMKI nuclear physics experiment. In particular, for the case of a spin-1 boson, the viable parameter space can be fully covered in a few months of data taking.

Comments: 8 pages, 5 figures and 1 table
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
Cite as: arXiv:2209.09261 [hep-ph]
Nuclear Experiment
[Submitted on 8 Aug 2022 (v1), last revised 15 Aug 2022 (this version, v2)]
Searching for New Physics with DarkLight at the ARIEL Electron-Linac
The DarkLight Collaboration, E. Cline, R. Corliss, J. C. Bernauer, R. Alarcon, R. Baartman, S. Benson, J. Bessuille, D. Ciarniello, A. Christopher, A. Colon, W. Deconinck, K. Dehmelt, A. Deshpande, J. Dilling, D. H. Dongwi, P. Fisher, T. Gautam, M. Gericke, D. Hasell, M. Hasinoff, E. Ihloff, R. Johnston, R. Kanungo, J. Kelsey, O. Kester, M. Kohl, I. Korover, R. Laxdal, S. Lee, X. Li, C. Ma, A. Mahon, J. W. Martin, R. Milner, M. Moore, P. Moran, J. Nazeer, K. Pachal, T. Patel, T. Planche, M. Rathnayake, M. Suresh, C. Vidal, Y. Wang, S. Yen

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]
(or arXiv:2208.04120v2 [nucl-ex] for this version)

[Submitted on 18 Nov 2021 (v1), last revised 10 Feb 2022 (this version, v2)]
Neutrino Physics Opportunities with the IsoDAR Source at Yemilab
J. Alonso, C.A. Argüelles, A. Bungau, J.M. Conrad, B. Dutta, Y.D. Kim, E. Marzec, D. Mishins, S.H. Seo, M. Shaevitz, J. Spitz, A. Thompson, L. Waites, D. Winklehner

IsoDAR seeks to place a high-power-cyclotron and target combination, as an intense source of ν¯e at the level of ∼1023/year, close to a kiloton-scale neutrino detector in order to gain sensitivity to very short-baseline neutrino oscillations (ν¯e→ν¯e) and perform precision tests of the weak interaction, among other physics opportunities. Recently, IsoDAR has received preliminary approval to be paired with the 2.26~kton target volume liquid scintillator detector at the Yemi Underground Laboratory (Yemilab) in Korea, at a 17~m center-to-center baseline, and cavern excavation for IsoDAR is now complete. In this paper, we present the physics capabilities of IsoDAR@Yemilab in terms of sensitivity to oscillations (via inverse beta decay, IBD; ν¯e+p→e++n), including initial-state wavepacket effects, and the weak mixing angle (via elastic scattering off atomic electrons, ν¯e+e−→ν¯e+e−). We also introduce a study of IsoDAR sensitivity to new particles, such as a light X boson, produced in the target that decays to νeν¯e.

Comments: 17 pages, 16 figures; this version presents a number of new physics topics and studies
Subjects: High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph)
Cite as: arXiv:2111.09480 [hep-ex]

High Energy Physics - Phenomenology
[Submitted on 12 Oct 2021]
X17 discovery potential in the γN→e+e−N process at electron scattering facilities
Johannes Backens, Marc Vanderhaeghen

We propose a direct search for the X17 particle, which was conjectured to explain the ATOMKI 8Be and 4He anomalies, through the dilepton photoproduction process on a nucleon in the photon energy range below or around the pion production threshold. For the scenarios of either pseudoscalar, vector, or axial-vector quantum numbers of the conjectured X17, we use existing constraints to estimate the X17 signal process. For dilepton resolutions which have been achieved in previous experiments, a signal-to-background ratio of up to an order of magnitude is found for a neutron target, and in particular for the pseudoscalar and vector X17 scenarios.

Comments: 5 pages, 2 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
Cite as: arXiv:2110.06055 [hep-ph]

 

[Vanadium 50]

Don't understand why there needs to be so many threads on this rather than having the messages all in one place. And don't see what the advantage is to guessing what the results might be rather than waiting to see what they are.

 

[kodama]

i find it exciting that 2023 we will have answers

if x17 is confirmed what exactly does it do ?

as a force what new interaction with fermions?

is it work with susy?

 

[kodama]

could x17 explain why Neutrino have mass

 

[Vanadium 50]

No.

 

[kodama]

No.

if in 2023 Montreal Tandem accelerator or other like Positron Annihilation to Dark Matter Experiment and ARIEL and ISAC facilities and DarkLight experiment. rules out x17 i would accept itif in 2023 Montreal Tandem accelerator or other experiments like PADME and ARIEL and ISAC facilities and DarkLight experiment. confirm x17 would you accept it ?

 

[Vanadium 50]

You asked a question. "could x17 explain why Neutrino have mass". The answer is "no". That has nothing to do with what other experiments do or do not see. If these experiments see positive results, it still wouldn't explain neutrino masses, the results of the last election in [pick your favorite country]. why Nicholas Cage finds himself making stinker after stinker, or why red licorice is yummy and black licorice is nasty.

Further, the thing to do is not to speculate on what they might see, but wait and see what they do see. You know, actual science.

 

[kodama]

You asked a question. "could x17 explain why Neutrino have mass". The answer is "no". That has nothing to do with what other experiments do or do not see. If these experiments see positive results, it still wouldn't explain neutrino masses, the results of the last election in [pick your favorite country]. why Nicholas Cage finds himself making stinker after stinker, or why red licorice is yummy and black licorice is nasty.

Further, the thing to do is not to speculate on what they might see, but wait and see what they do see. You know, actual science.

do you think Montreal Tandem accelerator or other like Positron Annihilation to Dark Matter Experiment and ARIEL and ISAC facilities and DarkLight experiment could prove that x17 existed if successful and positive for a signal ?

 

[Vanadium 50]

Just as posting multiple threads on the same topic doesn't yield different answers, asking the same question multiple times doesn't either.

 

[kodama]

Volume 414 - 41st International Conference on High Energy physics (ICHEP2022) - Beyond the Standard Model
Latest results and future prospects of the NA64 experiment at CERN SPS
L. Marsicano
Full text: pdf
Pre-published on: November 21, 2022
Published on: —
Abstract
The search for Dark Matter (DM) is one of the hottest topics of modern physics. Despite the various astrophysical and cosmological observations proving its existence, its elementary properties remain to date unknown. In addition to gravity, DM could interact with ordinary matter through a new force, mediated by a new vector boson (Dark Photon, Heavy Photon or A′
), kinetically mixed with the Standard Model photon. The NA64-e experiment at CERN fits in this scenario, aiming to produce DM particles using the 100 GeV SPS electron beam impinging on a thick active target (electromagnetic calorimeter). In this setup the DM production signature consists in a large observed missing energy, defined as the difference between the energy of the incoming electron and the energy measured in the calorimeter, coupled with null activity in the downstream veto systems. Recently, following the growing interest in positron annihilation mechanisms for DM production, the NA64 collaboration has performed preliminary studies with the aim to run the experiment with a positron beam, as planned within the POKER (POsitron resonant annihilation into darK mattER) project.
This work presents the latest NA64-e
results and its future prospects, reporting on the progresses in the positron beam run and discussing the sensitivity of the experiment to alternative variations of to the dark photon paradigm.
DOI: https://doi.org/10.22323/1.414.0174

 

[Vanadium 50]

There is very little value in just dumping an abstract here.

Did you read the paper? It spends only a few sentences on the X17, and what there is negative. No observation.

 

[kodama]

There is very little value in just dumping an abstract here.

Did you read the paper? It spends only a few sentences on the X17, and what there is negative. No observation.

Did you read the paper? Did you read section 4.2 page 6

 

[Vanadium 50]

Yes. The key words are "has been proposed". That means "does not exist".

 

[kodama]

Yes. The key words are "has been proposed". That means "does not exist".

the experiment or x17? this thread is about

Updates on the experiments X17​

any and all present or future experiments search for x17

this paper

Latest results and future prospects of the NA64 experiment at CERN SPS

experiments search for x17

is relevant to this thread

it also explains why NA64 experiment at CERN SPS hadn't seen x17 and what NA64 experiment at CERN SPS will do future experiments search for x17

 

[Vanadium 50]

it also explains why NA64 experiment at CERN SPS hadn't seen x17

Yeah, it seems not to be there.

 

[kodama]

Yeah, it seems not to be there.

:)

the exciting thing i think is that we should get results as early as 2023. When I first heard about it in the news in 2016 and again in 2019 I wondered how soon will we know. These papers seem to imply 2023

 

[kodama]

Volume 406 - Corfu Summer Institute 2021 "School and Workshops on Elementary Particle Physics and Gravity" (CORFU2021) - Workshop on Connecting Insights in Fundamental Physics: Standard Model and Beyond

Searching for light dark matter with the PADME experiment

I. Oceano*, A.P. Caricato, M. Martino, S. Spagnolo, G. Chiodini, F. Bossi, et al. (click to show)

Full text: pdf

Published on: November 23, 2022

Abstract
The search for dark matter at accelerators has gained a lot of attention in recent years. Among the theoretical scenarios that can be studied, an attractive one is postulating a new UD(1)
gauge symmetry mediated by a massive boson often named dark photon A′. The A′ could be the bridge between the Standard Model (SM) and a hypothetical Dark Sector (DM), having a small coupling ϵ with SM particles.
PADME (Positron Annihilation to Dark Matter Experiment) is the first fixed target experiment searching for the A′ produced in association with a photon in e+e− annihilations. It exploits the missing mass technique and does not make any assumption on the decay mode of the A′. PADME is located at the Laboratori Nazionali di Frascati (LNF) of INFN and it is designed to be sensitive to the production of a dark photon with mass MA′≤23.7 MeV. Its setup is also ideal to investigate other scenarios of low mass dark matter: axion-like particles (ALPs), dark Higgs, and the X17
boson claimed to explain anomalies observed recently in a nuclear physics experiment.

DOI: https://doi.org/10.22323/1.406.0040

 

[kodama]

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment​

Volume 1047, February 2023, 167858

A spectrometer for the measurement of anomalies in the angular correlation of electron and positron internally produced in excited 8Be and 4He​

Author links open overlay panelhttps://doi.org/10.1016/j.nima.2022.167858Get rights and content

Abstract​

In this work we describe the ongoing construction of a Time Projection Chamber-based (TPC) spectrometer for light charged particles utilising magnetic field as a means for energy measurement, combining Multi Wire Proportional Chambers (MWPC) with Timepix3 pixel detectors for improved spatial and angular resolution. The spectrometer will be operated at the Institute of Experimental and Applied Physics (IEAP) Van-de-Graaff facility with the goal of verifying the so-called ATOMKI anomaly (deviation in the distribution of the opening angle between electrons and positrons originating in internal pair creations – IPC – in the decay of 8Be and 4He excited nuclei). Description of the detectors is provided along with a few results.

Introduction​

Recent studies reported a 6.8-

anomaly in the distribution of the opening angle of ee pairs produced in a Be transition [1], and identified a similar behaviour in the decay of
He [2]. These results have prompted the interest of the scientific community. The reported effect can be related with unidentified nuclear reactions, experimental effects, or even the production of a new boson, which has been put forward by several theoreticians [3] but that no other experiment has observed so far.

In order to provide an independent assessment of the anomaly, the Institute of Experimental and Applied Physics (IEAP) at the Czech Technical University in Prague is developing a dedicated experiment. To check the anomaly we plan to use our Van de Graaff accelerator, where a proton beam will induce the needed

Be and He excited states (using Li or
H, respectively, as fixed targets).

To detect the decay products of

Be and He, a spectrometer will be mounted surrounding the target. It will consist of 6 independent modules, each consisting of a Timepix3 (TPX3) detector [4] and a Multi-Wire Proportional Chamber (MWPC) [5] to track and measure the angular correlation of the particles, followed by a Time Projection Chamber (TPC) [6]. The 15-mm gaps between the TPC modules contain permanent magnets that provide a magnetic field to identify the particles and measure their momenta [7] (see Fig. 1). The potential sources of background are the scattered protons and the decay of Be – easily shielded; and gamma production, which is suppressed by combining the information of the different detection layers.

 

[kodama]

https://indico.cern.ch/event/985448.../attachments/2262445/3840532/Zacek_CAP_W3.pdf

what is needs modiff?

 

[ohwilleke]

On the plus side, it doesn't look like a terribly expensive experiment - probably well under $1 million Canadian.

 

[kodama]

On the plus side, it doesn't look like a terribly expensive experiment - probably well under $1 million Canadian.

by LHC cost standards sure
why's it taking so long time to get answers to x17

 

[ohwilleke]

by LHC cost standards sure
why's it taking so long time to get answers to x17

It took many decades to figure out the particle basis of the Periodic Table of Elements. It took 40 years to find the Higgs boson. It took about sixty years to figure out that neutrinos have a non-zero mass and we still have only the most vague idea about the extent to which there is CP violation by neutrinos. It took decades to figure out that the nuclear binding force was mediated by pions and other light mesons. It took several centuries to figure out that Newtonian gravity had to be modified with General Relativity.

Real life isn't a movie. Not everything gets resolved in an hour and a half.

 

[kodama]

It took many decades to figure out the particle basis of the Periodic Table of Elements. It took 40 years to find the Higgs boson. It took about sixty years to figure out that neutrinos have a non-zero mass and we still have only the most vague idea about the extent to which there is CP violation by neutrinos. It took decades to figure out that the nuclear binding force was mediated by pions and other light mesons. It took several centuries to figure out that Newtonian gravity had to be modified with General Relativity.

Real life isn't a movie. Not everything gets resolved in an hour and a half.

the original results were reported in 2015
apparently its 2025 we get some analysts say for x17 fire turned research

 

[kodama]

High Energy Physics - Experiment
arXiv:2009.02756 (hep-ex)
[Submitted on 6 Sep 2020 (v1), last revised 8 Sep 2020 (this version, v2)]
Hunting down the X17 boson at the CERN SPS
E. Depero, Yu. M. Andreev, D. Banerjee, J. Bernhard, V. Burtsev, A . Chumakov, D. Cooke, A. Dermenev, S. Donskov, R. Dusaev, T. Enik, N. Charitonidis, A. Feshchenko, V. Frolov, A. Gardikiotis, S. Gerassimov, S. Girod, S. Gninenko, M. Hosgen, V. Kachanov, A. Karneyeu, G. Kekelidze, B. Ketzer, D. Kirpichnikov, M. Kirsanov, V. Kolosov, I. Konorov, S. Kovalenko, V. Kramarenko, L. Kravchuk, N. Krasnikov, S. Kuleshov, V. Lyubovitskij, V. Lysan, V. Matveev, Yu. Mikhailov, L. Molina Bueno, D. Peshekhonov, V. Polyakov, B. Radics, R. Rojas, A. Rubbia, V. Samoylenko, D. Shchukin, H. Sieber, V. Tikhomirov, I. Tlisova, D. Tlisov, A. Toropin, A. Trifonov, B. Vasilishin, G. Vasquez, P. Volkov, V. Volkov, P. Ulloa, P. Crivelli

Recently, the ATOMKI experiment has reported new evidence for the excess of e+e− events with a mass ∼17 MeV in the nuclear transitions of 4He, that they previously observed in measurements with 8Be. These observations could be explained by the existence of a new vector X17 boson. So far, the search for the decay X17→e+e− with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining X17 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the X17 decay with the proposed method. To reach this goal an optimization of the X17 production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results [Phys. Rev. D101, 071101 (2020)], validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate shows that the goal of the proposed search is feasible.

Subjects: High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
Cite as: arXiv:2009.02756 [hep-ex]

 

[kodama]

if x17 is real what does it do ?

does it mediate a force between dark matter particles ?

 

[kodama]

Nuclear Experiment
[Submitted on 20 Jan 2023]
A new direct detection electron scattering experiment to search for the X17 particle
D. Dutta (1), H. Gao (2), A. Gasparian (3), T. J. Hague (3 and 4), N. Liyanage (5), R. Paremuzyan (6), C. Peng (7), W. Xiong (8), P. Achenbach (6), A. Ahmidouch (3), S. Ali (5), H. Avakian (6), C. Ayerbe-Gayoso (1), X. Bai (5), M. Battaglieri (9), H. Bhatt (1), A. Bianconi (10 and 11), J. Boyd (5), D. Byer (2), P. L. Cole (12), G. Costantini (10 and 11), S. Davis (3), M. De Napoli (13), R. De Vita (9), B. Devkota (1), B. Dharmasena (5), J. Dunne (1), L. El Fassi (1), V. Gamage (5), L. Gan (14), K. Gnanvo (6), G. Gosta (10 and 11), D. Higinbotham (6), C. Howell (2), S. Jeffas (5), S. Jian (5), A. Karki (1), B. Karki (2), V. Khachatryan (2), M. Khandaker (15), V. Kubarovsky (6), I. Larin (16), M. Leali (10 and 11), V. Mascagna (17 and 11), G. Matousek (2), S. Migliorati (10 and 11), R. Miskimen (16), P. Mohanmurthy (1), H. Nguyen (5), E. Pasyuk (6), A. Rathnayake (5), J. Rittenhouse West (4), A. Shahinyan (18), A. Smith (2), S. Stepanyan (6), E. van Nieuwenhuizen (2), L. Venturelli (10 and 11), B. Yu (2), Z. Zhao (2), J. Zhou (2 and 4) ((1) Mississippi State University, (2) Duke University, (3) North Carolina A&T State University, (4) Lawrence Berkeley National Laboratory, (5) University of Virginia, (6) Thomas Jefferson National Accelerator Facility, (7) Argonne National Laboratory, (8) Shandong University, (9) Isituto Nazionale di Fisica Nucleare, Sezione di Genova, (10) Dipartimento di Ingegneria dell'Informazione, Università di Brescia, (11) Isituto Nazionale di Fisica Nucleare, sezione di Pavia, (12) Lamar University, (13) Isituto Nazionale di Fisica Nucleare, Sezione di Catania, (14) University of North Carolina, Wilmington, (15) Energy Systems, (16) University of Massachusetts, (17) DiSAT, Università dell'Insubria, (18) Yerevan Physics Institute)

A new electron scattering experiment (E12-21-003) to verify and understand the nature of hidden sector particles, with particular emphasis on the so-called X17 particle, has been approved at Jefferson Lab. The search for these particles is motivated by new hidden sector models introduced to account for a variety of experimental and observational puzzles: excess in e+e− pairs observed in multiple nuclear transitions, the 4.2σ disagreement between experiments and the standard model prediction for the muon anomalous magnetic moment, and the small-scale structure puzzle in cosmological simulations. The aforementioned X17 particle has been hypothesized to account for the excess in e+e− pairs observed from the 8Be M1, 4He M0, and, most recently, 12C E1 nuclear transitions to their ground states observed by the ATOMKI group. This experiment will use a high resolution electromagnetic calorimeter to search for or set new limits on the production rate of the X17 and other hidden sector particles in the 3−60 MeV mass range via their e+e− decay (or γγ decay with limited tracking). In these models, the 1−100 MeV mass range is particularly well-motivated and the lower part of this range still remains unexplored. Our proposed direct detection experiment will use a magnetic-spectrometer-free setup (the PRad apparatus) to detect all three final state particles in the visible decay of a hidden sector particle for an effective control of the background and will cover the proposed mass range in a single setting. The use of the well-demonstrated PRad setup allows for an essentially ready-to-run and uniquely cost-effective search for hidden sector particles in the 3−60 MeV mass range with a sensitivity of 8.9×10−8 - 5.8×10−9 to ϵ2, the square of the kinetic mixing interaction constant between hidden and visible sectors.

Comments: 6 pages, 7 figures. arXiv admin note: substantial text overlap with arXiv:2108.13276
Subjects: Nuclear Experiment (nucl-ex)
Cite as: arXiv:2301.08768 [nucl-ex]

 

[kodama]

[Submitted on 24 Jan 2023]

Status and prospects of the NA64 experiment at the CERN SPS​

P. Crivelli

NA64 is a fixed target experiment at the CERN SPS designed as a hermetic general purpose detector to search for Dark Sector physics in missing energy events from electron/positron, hadrons, and muon scattering off nuclei. In this contribution to the FIPs 2022 workshop, we review the current status and prospects of NA64.

Comments:	5 pages, 4 figures, prepared for the proceedings of the FIPs 2022 workshop. arXiv admin note: text overlap with arXiv:2102.01885
Subjects:	High Energy Physics - Experiment (hep-ex)
Cite as:	arXiv:2301.09905 [hep-ex]
	(or arXiv:2301.09905v1 [hep-ex] for this version)
	https://doi.org/10.48550/arXiv.2301.09905

 

[kodama]

MEG II experiment

Search for the X17 particle with the MEG-II apparatus​

https://agenda.infn.it › contributions › attachmentsPDFJul 7, 2022 — The X17 search with MEG-II. H. Benmansour e+/e- energy sum and ... https://agenda.infn.it/event/28874/...ts/93998/128533/ICHEP2022_Benmansour_0707.pdf

could anyone interpret this early data? specifically does this data suggest or rule out X17?

 

[kodama]

is this initial data taking consistent with x17 or rule it out?

 

[Vanadium 50]

Generalissimo Francisco Franco is still dead.

 

[kodama]

Generalissimo Francisco Franco is still dead.

could you elaborate?

what does this data mean?

 

[Ibix]

could you elaborate?

Franco still dead. I take it V50 means 'nothing new here'.

 

[kodama]

Franco still dead. I take it V50 means 'nothing new here'.

okay but what does this means

what is actually happened here ?
it looks like e+e- pairs are emissions at an angle off the target
is the SM or x17?

 

[Vanadium 50]

If the experiment doesn't say they see something, having an outsider say that the do ois crackpotty. It puts the potty in cracpotty.
Seeing an e+e- pair is a very different think from seeing an X17.

 

[kodama]

If the experiment doesn't say they see something, having an outsider say that the do ois crackpotty. It puts the potty in cracpotty.
Seeing an e+e- pair is a very different think from seeing an X17.

a small fraction of the decay seems to be a wide angle e+e- pair the green and dotted red from brown dot target is what you would expect x17

 

[kodama]

ie

MEG II data collected samples evidence of X17

 

[kodama]

e-e+ and target

actual MEG II data February 2022

x17

same anomaly

independent evidence for x17

 

[Vanadium 50]

It is very brave of you to claim an experiment sees something that they claim they don't.

 

[kodama]

It is very brave of you to claim an experiment sees something that they claim they don't.

so where do they imply that x17 doesn't exist?

Generalissimo Francisco Franco is still dead.

https://agenda.infn.it/event/28874/...ts/93998/128533/ICHEP2022_Benmansour_0707.pdf

so where do they imply Generalissimo Francisco Franco is still dead?

 

[kodama]

just in

[Submitted on 15 Apr 2025]
Combined Evidence for the X17 Boson After PADME Results on Resonant Production in Positron Annihilation
Fernando Arias-Aragón, Giovanni Grilli di Cortona, Enrico Nardi, Claudio Toni

abstract

The Positron Annihilation into Dark Matter Experiment at the Laboratori Nazionali di Frascati has reported an excess of e+e− final-state events from positron annihilation on fixed-target atomic electrons. While the global significance remains at the 1.8σ level, the excess is centered around s√∼17MeV, coinciding with the invariant mass at which anomalous e+e− pair production has previously been observed in nuclear transitions from excited to ground states in 8Be, 4He and 12C, thereby strengthening the case for a common underlying origin, possibly involving a hypothetical new X17 boson. We discuss the significance of this independent accelerator-based evidence. Combining it with existing nuclear physics results, we obtain a value for the X17 mass of mX17=16.88±0.05 MeV, reducing the uncertainty from nuclear physics determinations alone by more than a factor of two.

Cite as: arXiv:2504.11439 [hep-ph]

conclusion independent accelerator-based evidence X17 mX17=16.88±0.05 MeV, 1.8σ

dark matter exhibit properties

 

[kodama]

On the Possible Detection of New Particles from Data on Soft Photons in Collisions of Protons and Nuclei and from Data on Ultra-High-Energy Cosmic Rays

Alexander T. D’yachenko(
St. Petersburg, INP and St. Petersburg State U.
)

2025
8 pages
Published in:

J.Phys.Conf.Ser. 2984 (2025) 1, 012019

Contribution to:

5th International Scientific Forum “Nuclear Science and Technologies”

Published: 2025

Abstract: (IOP)
In order to develop the statistical model for proton-nucleus collisions at the stage of expansion of the compound nuclear system, the adiabatic temperature change and the correction to the Boltzmann distribution of the multiplicity of emitted secondary particles are additionally taken into account. As a result, improved agreement with experimental data is obtained compared to previous studies for the soft-photon spectrum by transverse momentum in pp collisions at an incident proton momentum of 450 GeV/c in order to isolate a clearly expressed X17 signal at around 17 MeV. An interpretation of the detection of a boson with mass 38 MeV in the spectra of photons emitted in reactions of protons with carbon nuclei at an incident proton momentum of 5.5 GeV/c is proposed. Analyzing the spectra of ultra-high-energy cosmic rays (photons), confirmation of the existence of new particles — the X17 and X38 bosons, with masses of 17 MeV and 38 MeV, respectively, has been found

• Published: 2025

DOI:

• 10.1088/1742-6596/2984/1/012019

could a HEP comment on soft-photon spectrum by transverse momentum in pp collisionsat an incident proton momentum of 450 GeV/c in order to isolate a clearly expressed X17 signal at around 17 MeV.

 

[kodama]

[Submitted on 30 May 2025]
Search for a new 17 MeV resonance via e^+e^- annihilation with the PADME Experiment
F. Bossi, R. De Sangro, C. Di Giulio, E. Di Meco, D. Domenici, G. Finocchiaro, L.G. Foggetta, M. Garattini, P. Gianotti, M. Mancini, I. Sarra, T. Spadaro, C. Taruggi, E. Vilucchi, K. Dimitrova, S. Ivanov, Sv. Ivanov, K. Kostova, V. Kozhuharov, R. Simeonov, F. Ferrarotto, E. Leonardi, P. Valente, E. Long, G.C. Organtini, M. Raggi, A. Frankenthal

The PADME Experiment at the Frascati DA NE LINAC has searched for a hypothetical particle with mass around 17 MeV, commonly referred to as the X17, using a positron beam incident on a fixed target. The beam energy was varied between 262 and 296 MeV, corresponding to center-of-mass energies between 16.4 and 17.4 MeV. The X17 should be produced resonantly via annihilation when approaches its mass, inducing an excess of events with a two-body final state over the background expectation. The beam energy spacing was fixed to less than half the expected width of the resonance's line shape. Uncertainties below 1% per point were achieved. A blind analysis has been performed. The data are consistent with the expected background in most of the explored energy range, and limits are set in previously unexplored regions of the available parameter space. The most significant deviation is found for MeV, corresponding to a global significance of approximately 2 standard deviations over the null hypothesis expectation.

Comments: 23 pages, 24 figures
Subjects: High Energy Physics - Experiment (hep-ex)
Cite as: arXiv:2505.24797 [hep-ex]

2 standard deviations over the null hypothesis expectation isn't 5 standard deviations but " data are consistent with the expected background in most of the explored energy " and The most significant deviation is found for 17 MeV is progress towards x17

 

[ohwilleke]

The new muon g-2 experimental results and SM prediction, which are within 0.6 sigma of each other, disfavor the X17 hypothesis.

A new fundamental boson at 16.9 MeV would almost surely impact the muon g-2 results given that a muon is 105.7 MeV and that the experiments are being conducted with muons with 3.1 GeV of combined mass-energy because they are accelerated (this "magic" energy level causes cofounding components that add noise to the muon g-2 measurement to cancel out).

But there is no sign of any such impact at a sub-parts per million level.

Obviously, it would be ideal for someone to model the expected X17 impact on muon g-2 with a particular bump in the data (which doesn't exceed 2 sigma locally) for an X17 with particular theoretically proposed quantum numbers and couplings. But my first impression mathematical intuition suggests that is is strongly disfavored.

Still, the closest thing I could find to an analysis of that on arXiv is rather more hopeful after doing are more quantitative analysis:

We discuss new physics phenomenology of hidden scalar (S), pseudoscalar (P), vector (V) and axial-vector (A) particles coupled to nucleons and leptons, which could give contributions to proton charge radius, (g−2)μ, 8Be-4He anomaly and electric dipole moment (EDM) of Standard Model (SM) particles. . . . The existence of light sub-GeV bosons could possibly explain the muon (g−2) anomaly observed. We also summarize existing bounds on ATOMKI X17(JP=0−,1±) boson coupling with neutron, proton and electron. We implement these constraints to estimate the contribution of P, V and A particles to proton charge radius via direct 1-loop calculation of Sachs form factors. The analysis reveals the corresponding contribution is negligible. . . .

D. V. Kirpichnikov, Valery E. Lyubovitskij, Alexey S. Zhevlakov, "Implication of the hidden sub-GeV bosons for the (g−2)μ . . . ." arXiv:2002.07496 (November 23, 2020).

This paper concluded that:

We estimate sensitivity of NA64 muon active target experiment to probe sub-GeV Vector and Scalar mediator of DM by using comprehensive GEANT4 MCsimulation. These bosons can possibly explain (g-2) anomaly. In case of NA64 null result of observing muon missing energy events associated with hidden vector and scalar particles, one can exclude new sub-GeV bosons as interpretation of (g-2) anomaly.

In hindsight, this is actually good news for the X17. But, it takes a certain amount of special pleading to produce a rather odd fifth force and odd properties of an X17 to get there.

 

[kodama]

The new muon g-2 experimental results and SM prediction, which are within 0.6 sigma of each other, disfavor the X17 hypothesis.

A new fundamental boson at 16.9 MeV would almost surely impact the muon g-2 results given that a muon is 105.7 MeV and that the experiments are being conducted with muons with 3.1 GeV of combined mass-energy because they are accelerated (this "magic" energy level causes cofounding components that add noise to the muon g-2 measurement to cancel out).

But there is no sign of any such impact at a sub-parts per million level.

Obviously, it would be ideal for someone to model the expected X17 impact on muon g-2 with a particular bump in the data (which doesn't exceed 2 sigma locally) for an X17 with particular theoretically proposed quantum numbers and couplings. But my first impression mathematical intuition suggests that is is strongly disfavored.

Still, the closest thing I could find to an analysis of that on arXiv is rather more hopeful after doing are more quantitative analysis:



D. V. Kirpichnikov, Valery E. Lyubovitskij, Alexey S. Zhevlakov, "Implication of the hidden sub-GeV bosons for the (g−2)μ . . . ." arXiv:2002.07496 (November 23, 2020).

This paper concluded that:



In hindsight, this is actually good news for the X17. But, it takes a certain amount of special pleading to produce a rather odd fifth force and odd properties of an X17 to get there.

there's

arXiv:2505.21305 (hep-ph)
[Submitted on 27 May 2025]
Concurrent Exploration of Axion-Like Particle Interactions with Gauge Bosons at the LHC
Shirin Chenarani, Mojtaba Mohammadi Najafabadi

Axion-like particles (ALPs) are pseudo Nambu-Goldstone bosons associated with spontaneously broken global symmetries incorporated in the Standard Model (SM) Lagrangian in many models beyond the SM. The existence of a light ALP is plausible due to the long-standing problems that the SM has not been able to address, such as the dark matter (DM) problem and the observed matter-antimatter asymmetry.

and

arXiv:1609.01669 (hep-ph)
[Submitted on 6 Sep 2016 (v1), last revised 28 Oct 2016 (this version, v2)]
Possible Explanation of the Electron Positron Anomaly at 17 MeV in Transitions Through a Light Pseudoscalar
Ulrich Ellwanger, Stefano Moretti

We estimate the values of Yukawa couplings of a light pseudoscalar A with a mass of about 17 MeV, which would explain the

anomaly observed in the Atomki pair spectrometer experiment. The resulting couplings of A to up and down type quarks are about 0.3 times the coupling of the standard Higgs boson. Then constraints from K and B decays require that loop contributions to flavour changing vertices cancel at least at the 10% level. Constraints from beam dump experiments require the coupling of A to electrons to be larger than about 4 times the coupling of the standard Higgs boson, leading to a short enough A life time consistent with an explanation of the anomaly.

Comments:	12 pages, discussion of nuclear shell model corrected, to appear in JHEP
Subjects:	High Energy Physics - Phenomenology (hep-ph)
Report number:	LPT Orsay 16-54
Cite as:	arXiv:1609.01669 [hep-ph]

 

[kodama]

The new muon g-2 experimental results and SM prediction, which are within 0.6 sigma of each other, disfavor the X17 hypothesis.


In hindsight, this is actually good news for the X17. But, it takes a certain amount of special pleading to produce a rather odd fifth force and odd properties of an X17 to get there.

these are Positron Annihilation into Dark Matter Experiment) at Laboratori Nazionali di Frascati of INFN run 4 in 2025

PADME Experiment run 4 the hope to get enough data points and improve detectors for 5 sigma if successful

Preparations for PADME Run IV currently ongoing
▪ New Micromegas chambers ➔ 𝑒+𝑒− vs. 𝛾 background
separation and new signatures possible
▪ More beam operation stability measurements to reduce
systematic uncertainties
▪ More data taking! (to reduce statistical uncertainties)
• Expected to completely cover the open vector X17
parameter space
• Data taking soon!

https://indico.global/event/652/contributions/16905/attachments/57490/110416/UCLADM2025_PADME_v2.pdf

▪ More data taking! (to reduce statistical uncertainties)

• Expected to completely cover the open vector X17
parameter space

its possible that the 2-sigma will go away with More data taking like the 750 gev di photon excess but the hope is enough data with upgrade detector for 5 sigma

 

[ohwilleke]

its possible that the 2-sigma will go away with More data taking like the 750 gev di photon excess but the hope is enough data with upgrade detector for 5 sigma

Hope away. But disappearing is more likely.

 

[kodama]

Hope away. But disappearing is more likely.

how would your world view change if Positron Annihilation into Dark Matter Experiment run 4 or something similar Experiment provides the 5 sigma necessary for discovery?
and especially what does x17 and hidden sector implications for Deur?

 

[ohwilleke]

how would your world view change if Positron Annihilation into Dark Matter Experiment run 4 or something similar Experiment provides the 5 sigma necessary for discovery?

Obviously, I'd take that very seriously. I believe in evidence and the scientific method. It would have to be considered in light of all of the evidence. But if you're at 5 sigma, you have replication, and you have a legitimate theory, then it's safe to say it is real.

and especially what does x17 and hidden sector implications for Deur?

Nothing about the X17 hypothesis makes it a good dark matter candidate. The observations come from atomic physics.

 

[kodama]

Obviously, I'd take that very seriously. I believe in evidence and the scientific method. It would have to be considered in light of all of the evidence. But if you're at 5 sigma, you have replication, and you have a legitimate theory, then it's safe to say it is real.

Nothing about the X17 hypothesis makes it a good dark matter candidate. The observations come from atomic physics.

if you bother to review the literature, x17 is part of a hidden sector that may include many additional particles with very feeble to no interactions to the standard model. many proposals include x17 and sterile neutrinos

i.e

arXiv:2403.15387 (hep-ph)

[Submitted on 22 Mar 2024 (v1), last revised 10 Oct 2024 (this version, v2)]

Production of dark sector particles via resonant positron annihilation on atomic electrons​

Fernando Arias-Aragón, Luc Darmé, Giovanni Grilli di Cortona, Enrico Nardi


is a hidden sector or also called dark sector compatible with Deur or a paradigm crisis for Deur

 

[ohwilleke]

if you bother to review the literature, x17 is part of a hidden sector that may include many additional particles with very feeble to no interactions to the standard model. many proposals include x17 and sterile neutrinos

Most of those proposals have little merit, including sterile neutrinos which are strongly disfavored by observational evidence.

is a hidden sector or also called dark sector compatible with Deur or a paradigm crisis for Deur

Deur's goal is to explain dark matter phenomena and dark energy phenomena with non-perturbative GR effects, thus ruling out the necessity of a hidden or dark sector.

The paradigm crisis right now is for dark matter particle theorists who just can't manage to find any candidates that aren't ruled out by observations that explain the data.

Extremely light bosonic dark matter candidates (with particle masses < 10^-21 eV) are still in the running, but basically nothing else works. Time and time again, searches for evidence for a hidden or dark sector particles that could explain dark matter phenomena either come up empty, or are flat out contradicted.

But, even if a new particle was discovered, for example, a new carrier boson that imparted mass to neutrinos, or additional Higgs bosons, this wouldn't necessarily make the new fundamental particles good dark matter candidates.

The inferred distribution of dark matter from stellar dynamics in galaxies is very diffuse in deep space, so the candidates need to be stable (on a time frame of many billions of years), something that is usually not a property of additional Higgs bosons or carrier bosons for a force or mass generation.

The most fundamental problem when it comes to devising properties for dark matter particle candidates is that the inferred distribution of dark matter particles is very tightly correlated with the distribution of ordinary matter (far beyond what gravity alone should do), yet other constraints suggest that it should have almost no non-gravitational Standard Model force interactions with ordinary matter (direct dark matter detection experiments, for example, constrain dark matter particle candidates with GeV or larger masses to have cross-sections of interaction a million times or more weaker than neutrinos, and W and Z and Higgs boson decays and N_eff constraints from cosmology and reactor data, tightly restrict the possibility of additional active neutrinos with sub-GeV masses). The problem of reconciling these twin constraints is intractable.

Ultra-light dark matter candidates try to reconcile this by having an extremely large (galaxy scale) Compton wave-length and Bose statistics, that basically makes the candidates a 5th force or fluid. I personally see this trend as likely to ultimately converge on a dark matter particle candidate that looks a whole lot like a graviton.

A newly discovered particle that wasn't a dark matter candidate, of course, wouldn't disturb the paradigm of Deur, or any other gravity based or modified gravity theory.

Likewise, extremely high energy hidden sectors (e.g. inflatons), which might be proposed as explanations of cosmic inflation, while they could be relevant in the era of the Big Bang and immediately afterwards, wouldn't be relevant to explain dark matter and dark energy phenomena in the next 13 billion plus years that follow that high energy era.

Any dark matter particle candidate with a low enough energy scale to be relevant post-Big Bang Nucleosynthesis (about 15 minutes or so after the Big Bang), is within the reach of Earth based current collider experiments. But, we've seen nothing convincing so far, which means that it would have to be almost completely sterile (i.e. having virtually no non-gravitational interactions other than self-interactions with particles of the same type). A 17 MeV particle emitted in connection with beta-decay wouldn't be a viable dark matter particle candidate even if it existed.