Status and Prospects of PADME Run 3

Status and Prospects of PADME

• 2305.08684 [hep-ex] (May 15, 2023)

The Positron Annihilation to Dark Matter Experiment (PADME) was designed and constructed to search for dark photons (A′) in the process e+e−→γA′, using the positron beam at the Beam Test Facility (BTF) at the National Laboratories of Frascati (LNF). Since the observation of an anomalous spectra in internal pair creation decays of nuclei seen by the collaboration at the ATOMKI institute, the PADME detector has been modified and a new data-taking run has been undertaken to probe the existance of the so-called ``X17" particle

Comments: 6 pages, 12 figures, proceedings from Moriond EW 2023
Subjects: High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
Cite as: arXiv:2305.08684 [hep-ex]
(or arXiv:2305.08684v1 [hep-ex] for this version)https://doi.org/10.48550/arXiv.2305.08684

quotes from New paper

1 Introduction
As the parameter space available to WIMP models of dark matter has reduced over recent
years, interest has grown in dark sector models. These models assume that dark matter is made
of particles which interact feebly with Standard Model particles via a portal particle, known
as a dark photon (A′). The dark photon would be a massive vector boson, characterised by
two parameters: the mass (mA′ ) and the coupling () to Standard Model fermions. Current
constraints for Dark Photon models are shown in Figures 1a and 1b respectively 1.
This talk gave an update on the status and
prospects of PADME Run 3 which aims to in-
vestigate the anomaly found in internal pair cre-
ation (IPC) decays of different nuclei by Kraszna-
horkay et al. at the ATOMKI Institue in Debrecen,
Hungary. This anomaly, also known as the “X17
anomaly”, was first found in the angular spectrum
of e+e− pairs resulting from 8Be decays.

4 PADME Run 3
As discussed in Section 1, in 2022 the PADME collaboration undertook a new round of data-
taking specifically searching for the X17 particle. Due to the expected increase in the cross
section of production of the particle on resonance, the collaboration decided to perform a scan
across the energy range expected from the ATOMKI experiments, shown as the green band in
Figure 7. Studies from Run 2 revealed the difficulty of studying charged-particle final states
using the Vetoes. For this reason, the experimental setup was modified in order to perform the
measurement using the ECal: the PADME dipole was switched off and a new plastic scintillator
detector, known as the ETagger was built directly in front of the ECal, as shown in Figure 3.
A scan was performed over beam energies between 260-300 MeV in steps of 0.7 MeV, with the
beam energy being selected by changing the current of the penultimate LINAC dipole magnet
before the PADME target, and the beam trajectory was then corrected using the last dipole
along the beamline in order to redirect the beam back along the PADME axis. While in Runs 1
and 2 the beam multiplicity was 28×103 PoT per bunch, with the magnetic field off this would
cause the ECal to be overwhelmed with Bremsstrahlung positrons. Therefore, the multiplicity
was reduced to 5×103 PoT per bunch by keeping the LINAC collimators relatively closed. This
had the benefit of allowing in turn for a very low energy spread at each point, corresponding

As of April 2023, the data has been in-
spected to assess the data quality. Figure 8
shows the energy of all clusters in the ECal
as a function of the theta angle between the cluster and the beamline, for all 5 of the below
resonance points. Due to kinematic constraints, any particles coming from vertices at the tar-
get should have a kinematic profile which lies inside the box highlighted in red .
5 Conclusion
PADME was designed and constructed to search for dark photons in e+e− annihilation. In 2022
the collaboration published its first physics measurement, finding the cross-section e+e− → γγ
to be well in agreement with the Standard Model at next to leading order. Later that year
the collaboration turned its attentions to the X17 anomaly found at the ATOMKI institute,
undertaking a specific data-taking run searching for this particle on-resonance. Inspections of
the data quality show that the data is not dominated by backgrounds coming from the beamline,
and that therefore it is in a good state for the X17 analysis
we should see answers to x17 sooner than later

2305.08684 [hep-ex]

Dark (Side) Matter? PADME? One wonders if the designers are big Star Wars fans. :)

swampwiz said:

Dark (Side) Matter? PADME? One wonders if the designers are big Star Wars fans. :)

I can accept PADME testing definitive for X17

swampwiz said:

Dark (Side) Matter? PADME? One wonders if the designers are big Star Wars fans. :)

EPJ Web of Conferences 275, 01012 (2023)
https://doi.org/10.1051/epjconf/202327501012
Investigation of a light Dark Boson existence: The New JEDI project

Beyhan Bastin1*,**,***, Jürgen Kiener2**,***, Isabelle Deloncle2**, Alain Coc2**, Maxim Pospelov3**, Jaromir Mrazek4**, Livio Lamia5,6**, Dieter Ackermann1, Philip Adsley7,8***, Charles-Olivier Bacri2, Jérôme Bourçois2, Vaclav Burjan4, Anastasia Cassisa4, Giuseppe D’agata4,5,6, Gilles De France1, Alessia Di Pietrio6, Yasmine Demane9, François De Oliveira1, Lindsay Donaldson7,8***, Corinne Donzaud10, Jean-Eric Ducret1, Clarisse Hamadache2, Fairouz Hammache2, Pete Jones6, Marco La Cognata6, Adrien Laviron2, Marek Lewitowicz1, Kgashane Malatji8, Antonio Massara6, Cyril Pitrou11,12, Rosario Gianluca Pizzone6, Giovanni Luca Guardo6, Marek Płoszajczak1, Giuseppe Rapisarda5,6, Bernadette Rebeiro9,14, Brigitte Roussèire2, Domenico Santonocito6, Nicolas de Séréville2, Maria Letizia Sergi5,6, Eva Simeckova4, Olivier Sorlin1, Christelle Stodel1, Vincent Tatischeff2, Jean-Charles Thomas1 and Aurora Tumino6,13

1 Grand Accélérateur National d’Ions Lourds (GANIL), CEA/DRF-CNRS/IN2P3, 14076 Caen Cedex 05, France.
2 Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405, Orsay, France.
3 School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA.
4 Nuclear Physics Institute ASCR, 250 68 Řež, Czech Republic.
5 Dipartimento di Fisica e Astronomia "E. Majorana", Univ. di Catania, Italy.
6 Laboratori Nazionali del Sud, INFN, Catania, 95123 Italy.
7 School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa.
8 SSC Laboratory, iThemba LABS, Somerset West 7129, South Africa.
9 Univ. Lyon, Univ. Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, F-69622, Villeurbanne, France.
10 APC, Université Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cité, 75205 Paris, France.
11 Institut d’Astrophysique de Paris, CNRS UMR 7095, 98 bis Bd Arago, 75014 Paris, France.
12 Sorbonne Université, Institut Lagrange de Paris, 98 bis Bd Arago, 75014 Paris, France.
13 Facoltà di Ingegneria ed Architettura, Kore University, Viale delle Olimpiadi, 1, I-94100 Enna, Italy.
14 Department of Physics, McGill University, Montréal, Quebec H3A 2T8, Canada.

* New JEDI scientific coordinator / e-mail: bastin@ganil.fr
** New JEDI co-spokesperson
*** FASERED co-spokesperson

Published online: 3 February 2023

Abstract

Several experiments around the world are looking for a new particle, named Dark Boson, which may do the link between the Ordinary Matter (which forms basically stars, planets, interstellar gas...) and the Hidden Sectors of the Universe. This particle, if it exists, would act as the messenger of a new fundamental interaction of nature. In this paper, the underlying Dark Sectors theory will be introduced first. A non-exhaustive summary of experimental studies carried out to date and foreseen in the incoming years will be presented after,including the 8Be anomaly. The last section will provide a status of the New JEDI**** project which aims to investigate the existence or not of a Dark Boson in the MeV range.

We derive constraints on the couplings of light vector particles to all first-generation Standard Model fermions using leptonic decays of the charged pion, π+→e+νeXμ. In models where the net charge to which Xμ couples to is not conserved, no lepton helicity flip is required for the decay to happen, enhancing the decay rate by factors of O(m4π/m2em2X). A past search at the SINDRUM-I spectrometer severely constrains this possibility. In the context of the hypothesized 17 MeV particle proposed to explain anomalous 8Be, 4He, and 12C nuclear transitions claimed by the ATOMKI experiment, this limit rules out vector-boson explanations and poses strong limits on axial-vector ones.

Matheus Hostert, Maxim Pospelov, "Pion decay constraints on exotic 17 MeV vector bosons" arXiv:2306.15077 (June 26, 2023).

ohwilleke said:

Matheus Hostert, Maxim Pospelov, "Pion decay constraints on exotic 17 MeV vector bosons" arXiv:2306.15077 (June 26, 2023).

poses strong limits on axial-vector ones.

from the conclusion
If the evidence for X(17) persists in the data and
shows up also in other experimental setups, such as at
the Montreal X17 [65] and new JEDI [66] projects, it
would be worthwhile to reconsider a π+ → e+νeXee
search in modern experimental setups. To that end, a
search at the PIONEER experiment at PSI could be
performed, albeit with limited tracking capabilities [67].
An alternative would be to consider kaon factories as
a secondary source of pions. The modern photon ve-
toes and tracking capabilities of NA62 could help reject
backgrounds and extend these types of searches to low
Xee masses. We note that with the hadronic beam at
NA62, the number of pion and kaon decays are compa-
rable. Even with a down-scaled trigger, NA62 may be
well poised to perform such a search alongside other ex-
otic channels like K+ → e+νXee. A persistent X(17)
anomaly would also motivate a new set of π− capture
experiments that would move the suggested anomaly to
smaller angles (∼ 16 degrees) and be free from nuclear
uncertainties [68]. Finally, muon decays could also pro-
vide further insight. Previous studies show that the
Mu3e experiment at PSI can be sensitive to QV
e ε cou-
plings as low as 10−4 by searching for resonances in
μ+ → e+νμνe(X → e+e−) [69].
ACKNOWLEDGMENTS arXiv:2212.06453 (hep-ph)
[Submitted on 13 Dec 2022 (v1), last revised 6 Jun 2023 (this version, v2)]
An updated view on the ATOMKI nuclear anomalies
Daniele Barducci, Claudio Toni

Our conclusions identify the axial vector state as the most promising candidate, while other spin/parity assignments seems disfavored for a combined explanation. Intriguingly, an axial vector state can also simultaneously accommodate other experimental anomalies, {\emph{i.e.}} the KTeV anomaly in π0→e+e− decay while being compatible with the conflicting measurements of the anomalous magnetic moment of the electron (g−2)e and other constraints on the electron couplings of the X boson. The PADME experiment will completely cover the relevant region of the parameter space, thus allowing for a strong test of the existence of the X particle.
axial-vector still being held up from the last one

ohwilleke said:

Matheus Hostert, Maxim Pospelov, "Pion decay constraints on exotic 17 MeV vector bosons" arXiv:2306.15077 (June 26, 2023).

[Submitted on 5 Jul 2023]
X17 discovery potential from γD→e+e−pn with neutron tagging
Cornelis J.G. Mommers, Marc Vanderhaeghen
Download PDF

We propose a novel direct search experiment for X17 using the reaction γD→e+e−pn. X17 is a hypothetical particle conjectured by the ATOMKI collaboration to explain anomalous signals around 17 MeV in excited 8Be, 4He and 12C nuclear decays via internal pair creation. It has been subject to a global experimental and theoretical research program. The proposed direct search in γD→e+e−pn can verify the existence of X17 through the production on a quasi-free neutron, and determine its quantum numbers separate from ongoing and planned nuclear-decay experiments. This is especially timely in view of the theoretical tension between results from the 12C and 8Be measurements. Using the plane-wave impulse approximation, we quantify the expected signal and background for pseudoscalar, vector and axial-vector X17 scenarios. We optimize the kinematics for the quasi-free neutron region with the upcoming MAGIX experiment at MESA in mind and show that for all three scenarios the X17 signal is clearly visible above the QED background.

Comments: 5 pages
Subjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
Cite as: arXiv:2307.02181 [hep-ph]

Search for K+ decays into the π+e+e−e+e− final state​

NA62 collaboration

The first search for ultra-rare K+ decays into the π+e+e−e+e−final state is reported, using a dataset collected by the NA62 experiment atCERN in 2017-2018. An upper limit of 1.4×10−8 at 90% CL is obtainedfor the branching ratio of the K+→π+e+e−e+e− decay, predicted inthe Standard Model to be (7.2±0.7)×10−11. Upper limits at 90% CLare obtained at the level of 10−9 for the branching ratios of two promptdecay chains involving pair-production of hidden-sector mediators:K+→π+aa, a→e+e− and K+→π+S, S→A′A′,A′→e+e−. The QCD axion is excluded as a possible explanation ofthe "17 MeV anomaly".

https://meetings.triumf.ca/event/34...chments/3280/4227/Guineapig23_X17_V_Zacek.pdf




2024/5

kodama said:

https://meetings.triumf.ca/event/34...chments/3280/4227/Guineapig23_X17_V_Zacek.pdf

Good catch. That's a nice summary of what's in the works.

As an aside, I personally would favor arXiv creating separate categories for results of experiments which have been actually conducted on one hand, and experiments which are in the works or being considered, but have not yet generated real data, on the other. My first order of business in my daily review of preprints in astrophysics and HEP is to sort papers with actual data from "coming attractions" papers which I ignore until they actually start producing data.

I don't want, for example, to spend hours and hours of time reading dozens of papers about the work of a proposed International Linear Collider, only to eventually find out that my time has been wasted because the ILC project that I was reading papers about is cancelled in favor of another competing next generation particle collider project. I'm in a hurry, and I want to get on to the good stuff of what science has actually discovered.

This isn't to say, however, that it isn't legitimate to write papers about proposed new experiments, or that other people might be interested in the nitty gritty of those proposals and what they could do. It's just not my jam.

It would also be nice if there were a Wiki, or just a good subset of Wikipedia pages, keeping an ongoing watch over what experiments, "telescopes" (in the broad sense), and other research programs that: (1) have existed in the past but have run their course and are no longer active (broken up further in those that are not running but still doing data analysis and those that are completely wrapped up), (2) are currently active, (3) are under construction or in active development but have not yet produced experimental results, and (4) are contemplated or under serious consideration but have not "broken ground" or been approved yet. This list would then have links to details about each one and where to get more information about its work. This isn't a huge body of knowledge, but it isn't an easy topic to research in a comprehensive way and it is one of the significant barriers that "outsiders" from the scientific community face vis-a-vis insiders. It is certainly a more daunting task than I could take on alone, however.

ohwilleke said:

Good catch. That's a nice summary of what's in the works.

As an aside, I personally would favor arXiv creating separate categories for results of experiments which have been actually conducted on one hand, and experiments which are in the works or being considered, but have not yet generated real data, on the other. My first order of business in my daily review of preprints in astrophysics and HEP is to sort papers with actual data from "coming attractions" papers which I ignore until they actually start producing data.

I don't want, for example, to spend hours and hours of time reading dozens of papers about the work of a proposed International Linear Collider, only to eventually find out that my time has been wasted because the ILC project that I was reading papers about is cancelled in favor of another competing next generation particle collider project. I'm in a hurry, and I want to get on to the good stuff of what science has actually discovered.

This isn't to say, however, that it isn't legitimate to write papers about proposed new experiments, or that other people might be interested in the nitty gritty of those proposals and what they could do. It's just not my jam.

I just want the results for X17 NOW. LOL.

the first set of experiments are to reproduce the nuclear experiments by Atomki, such as using Be, He, C and other nuclei such as Be10





the second class is to directly create X17 from e-e+ collisions


Notice the NA64 at CERN needs a detector upgrade and more data.

with estimates in the 2024/25 timeframe for most of these experiments.

X17 is a cousin to Dark Photon, both of which decay into e-e+

https://meetings.triumf.ca/event/34...chments/3280/4227/Guineapig23_X17_V_Zacek.pdf

Is dated July 11-13, 2023



and is a description of Montreal latest efforts to verify X17

actual experiment at Montreal

Ideally both sets of experiments verify or rule out X17 and Atomki anomaly consistently.

its possible the first set of experiments fail to verify or rule out X17, yet the nuclear experiments verify the Atomki anomaly results with Be, He, and C and other elements and isotopes including Be10. perhaps Atomki anomaly is real and independently verified with other experiments and other nucleus but X17 is not the correct explanation.