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- Status and Prospects of PADME
Status and Prospects of PADME
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]
- 2305.08684 [hep-ex] (May 15, 2023)
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]