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A new search for an electric dipole moment of the neutron with increased sensitivity and an improved UCN source.

English title A new search for an electric dipole moment of the neutron with increased sensitivity and an improved UCN source.
Applicant Lauss Bernhard
Number 188700
Funding scheme Project funding
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Particle Physics
Start/End 01.09.2020 - 31.08.2024
Approved amount 970'208.00
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All Disciplines (3)

Particle Physics
Nuclear Physics
Other disciplines of Physics

Keywords (5)

ultracold neutron production ; search for physics beyond the standard model; ultracold neutron; fundamental neutron physics; neutron electric dipole moment

Lay Summary (German)

Ultrakalte Neutronen (UCN) haben extrem kleine Energien und Geschwindigkeiten, wodurch sie in geeigneten Flaschen einsperrbar sind und über mehrere Minuten beobachtbar sind. Dadurch können mit ihnen fundamentale Eigenschaften des Neutrons sehr genau vermessen werden. Die UCN Quelle produziert eine hohe UCN Intensität welche für genaue Messungen nötig ist.Ein elektrisches Dipolmoment des Neutrons (nEDM) würde einen Hinweis für eine Verletzung der fundamentalen Zeitumkehrinvarianz bedeuten und damit einen Hinweis zum Verständnis der Materie-Antimaterie Asymmetrie nach dem Urknall in unserem Universum liefern.
Lay summary

Die Genauigkeit von Präzisionsmessungen am Neutron hängt direkt von der Anzahl der zur Verfügung stehenden ultrakalten Neutronen (UCN) ab. Teil 1 des Forschungsprojektes zielt auf das genaue Verständnis der UCN Quelle am PSI ab, um die UCN Intensität für Experiment an der bereits weltweit besten UCN Quelle noch weiter zu erhöhen. Teil 2 des Projektes beschäftigt sich mit dem Aufbau eines neuen Experiments zur Such nach dem elektrischen Dipolmoment des Neutrons (n2EDM), welches alle bisherigen Experimente um einen Faktor 10 in Sensitivität übertreffen wird. Ziel ist die erste Messung eines nEDM im Bereich 10E-27 ecm.

Das SNF Projekt unterstützt 2 Doktorierende und eine PostDoktoratsstelle, welche Aufbau und Inbetriebnahme des Experiments, und die erste Auswertung der Messdaten führend durchführen werden.

Direct link to Lay Summary Last update: 02.08.2020

Responsible applicant and co-applicants


Associated projects

Number Title Start Funding scheme
163413 Improving ultracold neutron intensities for frontier precision experiments in fundamental physics 01.11.2015 Project funding
126562 Search for the neutron EDM at the high intensity ultracold neutron source at PSI with an upgraded high sensitivity spectrometer 01.10.2009 Project funding
139140 Passive magnetic shield for the new neutron electric dipole moment experiment n2EDM 01.01.2013 R'EQUIP
201473 n2EDM: The next measurement of the neutron electric dipole moment (II) 01.04.2021 FLARE
137664 Pushing the high intensity frontier for ultracold neutrons 01.11.2011 Project funding
163988 New magnetometer array for the n2EDM project 01.07.2015 International short research visits
157079 Search for the neutron EDM at the high intensity ultracold neutron source at PSI with an upgraded high sensitivity spectrometer - Follow-up application II. 01.10.2014 Project funding
186179 n2EDM: The next measurement of the neutron electric dipole moment 01.04.2019 FLARE
148659 Cross - collaborative exchange for design methods for magentic field coils of nEDM experiments 01.05.2013 International short research visits
149813 Pushing the high intensity frontier with ultracold neutrons 01.11.2013 Project funding
204118 Systematic Effects in Electric Dipole Searches at the Paul Scherrer Institute 01.03.2022 Project funding
200441 Precision Physics with Muons and Ultracold Neutrons II 01.05.2021 Project funding
172626 Highly accurate vector gradiometers for a next-generation neutron EDM experiment 01.08.2017 Project funding
162574 Measurement of the neutron electric dipole moment 01.11.2015 Project funding
178951 A novel neutronics model of the solid D2 ultracold neutron converter at PSI aiming for increasing the source intensity 01.07.2018 Project funding
149211 Measurement of the neutron electric dipole moment 01.11.2013 Project funding
138211 Measurement of the neutron electric dipole moment 01.11.2011 Project funding
144473 Search for the neutron EDM at the high intensity ultracold neutron source at PSI with an upgraded high sensitivity spectrometer - Follow-up application 01.10.2012 Project funding
177008 Field Generation and Control System for the n2EDM spectrometer 01.12.2017 R'EQUIP
172639 Precision Physics with Muons and Ultracold Neutrons 01.05.2017 Project funding


This new research proposal outlines a highly promising path to a first measurement of the neutron electric dipole moment (nEDM) in the 10E-27ecm range. We will commission and take data with a new apparatus called 'n2EDM', and significantly advance the characterization and performance of the UCN source at PSI in support of maximizing the n2EDM sensitivity. To accomplish these ambitious goals we request the support for two PhD student projects and one post-doctoral research project.Searches for permanent EDMs of particles with spin are at the forefront of particle physics, looking for violations of the combined charge (C) and parity (P) symmetry. They are considered among the most promising routes to establishing physics beyond the Standard Model of particle physics (BSM) and to shed light onto the origin of the matter-antimatter asymmetry of our Universe. Various results from our nEDM Collaboration have already contributed to searches for viable dark matter candidates like axion-like particles and mirror neutrons, and searches for Lorentz violation. A new improved limit on the nEDM from our collaboration is expected soon. The importance of the nEDM experiment is reflected by the inclusion in the 'European Strategy in Particle Physics - 2013, and update 2018-2020', the European `Long Range Plan, Perspectives in Nuclear Physics', and the 'US-American Long Range Plan for Nuclear Physics'.This proposal covers the next 4 years of setting up, commissioning, first data taking and analysis of the new apparatus at PSI. n2EDM is expected to deliver a factor 10 improvement in sensitivity already in the baseline setup. The PI of this grant proposal has been the technical coordinator of the n2EDM project for several years and lead it to the present construction phase. Schedule and design have been recently (01/2019) presented in the Technical Design and Project Delivery Reports. They were endorsed by an independent international technical review committee and approved by PSI's Particle Physics Research Committee.The PostDoc and PhD students will closely work together with the PSI UCN group and the international nEDM collaboration. They will play a pivotal role in setup and commissioning of the experiment. The PostDoc will lead the commissioning phase and be in charge to oversee the integration of all subsystems into the final apparatus together with the task managers of the project. This includes the two main subsystems of UCN guiding, storage and detection, and magnetic field generation, control and measurement. All components need to be characterized and optimized also to allow already new systematics measurements during this phase.PhD student 1 will strongly contribute to the setup of the apparatus and provide initial analysis results and quality checks. An R-value measurement, precisely determining the ratio of the neutron and Hg magnetic moments, is planned already in this phase and will allow for a physics publication on a new metrological reference value. Most importantly, the PhD student will develop and establish the new analysis for the double precession chamber setup. The new apparatus is expected to reach already within 20 days of data taking a UCN statistics surpassing any previous effort. PhD student 2 will work on various aspects of improving the UCN source yield and the optimization of the UCN guiding system leading to the apparatus. This will be crucial in enhancing the measurement sensitivity. In addition, design work and tests will be done by PhD student 2 for a future upgrade of the UCN source.In order to run the most sensitive nEDM search, the trained expert PhD students and PostDoc onsite will be of paramount importance also for the operation of the experiment. PSI has laid the foundation for this experiment with the construction of the high intensity UCN source 2005-10. Both, research on the UCN source and measurements using our previous nEDM apparatus have lead to numerous publications including a recent result on the UCN source featured as research highlight Europhysics News 49 (2019) 5-6.Today, there is a strong world-wide competition of at least five other sizeable projects on comparable or slightly later schedules, at the ILL Grenoble, at the SNS Oakridge, at LANL Los Alamos, at PNPI Gatchina, and at TRIUMF Vancouver. It is therefore important to keep the present thrust with new personnel replacing former young researchers in order to realize the n2EDM experiment at PSI on time.The PSI n2EDM experiment is considered by the Research Committee for Particle Physics at PSI and by the scientific community as currently to have a leading position to deliver the next much more sensitive result. With this proposal we ask for strong support to keep the leading position of this international effort in Switzerland.