# Updates on the experiments X17

• I
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.

Subjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
Cite as: arXiv:2110.06055 [hep-ph]

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Staff Emeritus
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?

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kodama
could x17 explain why Neutrino have mass

Staff Emeritus
No.

topsquark and ohwilleke
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 it

if in 2023 Montreal Tandem accelerator or other experiments like PADME and ARIEL and ISAC facilities and DarkLight experiment. confirm x17 would you accept it ?

Staff Emeritus
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 ?

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

topsquark, phinds and Tom.G
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

Staff Emeritus
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

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

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

### 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

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

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Staff Emeritus
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​

https://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.

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

Gold Member
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
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]

ohwilleke
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

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

#### Attachments

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Staff Emeritus
Generalissimo Francisco Franco is still dead.

ohwilleke
kodama
Generalissimo Francisco Franco is still dead.
could you elaborate?

what does this data mean?

2022 Award
ohwilleke
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?

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Staff Emeritus
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