# Kick-off workshop for the search of a muon EDM using the frozen spin technique at PSI

Europe/Zurich
PSI
, ,
Description

Mailing List: https://elog.psi.ch/elogs/Muon+EDM+Mailing+List/

Remote link: https://psi-ch.webex.com/psi-ch/j.php?MTID=mbb1db2d988c4d00d68ec5da10b33ad15 (Muon2020)

The aim of the workshop is to bring together scientists strongly motivated to participate in a search for a muon electric dipole moment (EDM) using the frozen spin technique at PSI.

The workshop will be organized as a topical seminar with break-out sessions addressing the different challenges of a compact muon storage ring employing the frozen spin technique to search for an electric dipole moment of the muon. In addition to invited contributions (30’), we very much appreciate shorter contributions by all participants. We plan for ample discussion time in each session.

Venue: PSI, West
Monday: WHGA 001 / Auditorium
Tuesday: WBGB 019
Wednesday: WBGB 019

Registration
Kick-off workshop for the search of a muon EDM using the frozen spin technique at PSI
Participants
• Alessandro Bravar
• Alexander Nass
• Alexander Skawran
• Andreas Adelmann
• Andreas Knecht
• Angela Papa
• Branislav Ristic
• Carlos Chavez Barajas
• Ciro Calzolaio
• Davide Reggiani
• Francesco Renga
• Francois Meot
• Frank Meier Aeschbacher
• Frank Rathmann
• Gavin Hesketh
• Irakli Keshelashvili
• Joe Price
• Joost Vossebeld
• Joseph Price
• Kim Siang Khaw
• Klaus Kirch
• Lukas Gerritzen
• Malte Backhaus
• Malte Backhaus
• Malte Hildebrandt
• Mark Lancaster
• Martin Fertl
• Massimo Giovannozzi
• Mikio Sakurai
• Nicola Neri
• Niklaus Berger
• Peter Winter
• Philipp Schmidt-Wellenburg
• Stefan Ritt
• Themis Bowcock
• Tsutomu Mibe
• Urs Langenegger
• Monday, February 17
• 9:00 AM 10:30 AM
Welcome and Overview: General 1 WHGA 001

### WHGA 001

Convener: Philipp Schmidt-Wellenburg (Paul Scherrer Institut)
• 9:00 AM
Welcome to PSI 10m

Information for the workshop

Speaker: Philipp Schmidt-Wellenburg (Paul Scherrer Institut)
• 9:10 AM
Theoretical Motivation for measuring the muon EDM 40m

We consider possible beyond-the-Standard-Model (BSM) effects that can accommodate both the long-standing tension in the anomalous magnetic moment of the muon, aμ=(g−2)μ/2, as well as the emerging 2.5σ deviation in its electron counterpart, ae=(g−2)e/2. After performing an EFT analysis, we consider BSM physics realized above the electroweak scale and find that a simultaneous explanation becomes possible in models with chiral enhancement. However, this requires a decoupling of the muon and electron BSM sectors to avoid the strong constraints from μ→eγ. In particular, this decoupling implies that there is no reason to expect the muon electric dipole moment (EDM) dμ to be correlated with the electron EDM de, avoiding the very stringent limits for the latter. While some of the parameter space for dμ favored by aμ could be tested at the (g−2)μ experiments at Fermilab and J-PARC, a dedicated muon EDM experiment at PSI would be able to probe most of this region. In fact, only muon EDM experiments are capable to test the associated effective operator, giving strong motiations for such a measurement.

Speaker: Andreas Crivellin
• 9:50 AM
The seach of the muon EDM using the frozen spin technique at PSI. 40m

A permanent EDM of an elementary particle violates parity (P) and time reversal (T) symmetry, and assuming CPT invariance, T violation implies CP violation. EDM predicted by the Standard Model (SM) are far too small to be detected with current experimental techniques, therefore, any observation of non-zero EDMs would strongly indicate the existence of physics beyond the SM (BSM).
The muon is of particular interest and is the only fundamental particle which reasonably allows to measure the EDM directly. The current best upper limit of the $\mu$EDM, $1.8\times{10}^{-19}e\!\cdot\!\mathrm{cm}$ ($95\%$ C.L.), was obtained parasitically in the $(g-2)$'' measurement of the muon at Brookhaven. This leaves the muon EDM as one of the least tested areas of the SM.
In my talk I will sketch the ideas and possibilities for a dedicated search of the muon EDM using the frozen spin technique at PSI.

Speaker: Philipp Schmidt-Wellenburg (Paul Scherrer Institut)
• 10:30 AM 11:00 AM
Coffee 30m
• 11:00 AM 12:30 PM
Storage ring dynamics: Injection and Storage 1 WHGA 001

### WHGA 001

Convener: Andreas Adelmann (Paul Scherrer Institut)
• 11:00 AM
Overview of muon EDM searches - the past, the present, and the future 40m

Electric dipole moment (EDM) of the muon is one of the least tested areas of the Standard Model (SM) of Particle Physics and any detected signal is a strong hint of physics beyond the SM. In this presentation, I will review the history of the searches for a muon EDM, current status of efforts at Fermilab and J-PARC, and the new effort at PSI.

Speaker: Kim Siang Khaw (Tsung-Dao Lee Institute, Shanghai Jiao Tong University)
• 11:40 AM
Novel techniques for injecting or extracting beams from a circular ring 40m

In recent years, non-linear beam dynamics has been used to design novel manipulations that exploit multiple stable orbits in a single ring. In this presentation, an overview of the methods that have been developed will be carried out focusing on the possibility of devising new means for injecting or extracting beams from a circular accelerator.

Speaker: Massimo Giovannozzi (CERN)
• 12:30 PM 2:00 PM
Lunch 1h 30m
• 2:00 PM 3:00 PM
EDM in storage rings WHGA 001

### WHGA 001

Convener: Klaus Stefan Kirch (Paul Scherrer Institut)
• 2:00 PM
Electric dipole moment searches using storage rings (Part I) 20m

The Standard Model (SM) of Particle Physics is not capable to account for the apparent
matter-antimatter asymmetry of our Universe. Physics beyond the SM is required and is either
probed by employing highest energies (e.g., at LHC), or by striving for ultimate precision and
sensitivity (e.g., in the search for electric dipole moments). Permanent electric dipole moments
(EDMs) of particles violate both time reversal (T) and parity (P) invariance, and are via the
CPT-theorem also CP-violating. Finding an EDM would be a strong indication for physics
beyond the SM, and pushing upper limits further provides crucial tests for any corresponding
theoretical model, e.g., SUSY.
Up to now, EDM searches focused on neutral systems (neutrons, atoms, and molecules).
Storage rings, however, o?er the possibility to measure EDMs of charged particles by observing
the in
uence of the EDM on the spin motion in the ring [1, 2, 3]. Direct searches of proton
and deuteron EDMs bear the potential to reach sensitivities beyond 10E-29 e cm. Since the
Cooler Synchrotron COSY at the Forschungszentrum Julich provides polarized protons and
deuterons up to momenta of 3.7 GeV/c, it constitutes an ideal testing ground and starting
point for such an experimental program.
The collaboration is presently aiming at a ?rst direct (precursor) measurement of the
deuteron EDM in COSY[4], using an RF Wien ?lter that was speci?cally designed for that
purpose [5, 6, 7]. Beyond that, the technical design of a prototype EDM storage ring [8]
constitutes the next major milestone of the JEDI research program, which shall be addressed
together with CERN in the framework of a newly formed CPEDM collaboration1.
The talk will present the JEDI plans for the measurement of charged hadron EDMs, and
discuss the various technical developments, and also show recent results.

Speakers: Dr Frank Rathmann (Institute for Nuklear Physik, Forschungszentrum Jülich), Dr Alexander Nass (Institute for nuclear physics, Forschungszentrum Jülich)
• 2:20 PM
Electric dipole moment searches using storage rings (Part II) 20m

The Standard Model (SM) of Particle Physics is not capable to account for the apparent
matter-antimatter asymmetry of our Universe. Physics beyond the SM is required and is either
probed by employing highest energies (e.g., at LHC), or by striving for ultimate precision and
sensitivity (e.g., in the search for electric dipole moments). Permanent electric dipole moments
(EDMs) of particles violate both time reversal (T) and parity (P) invariance, and are via the
CPT-theorem also CP-violating. Finding an EDM would be a strong indication for physics
beyond the SM, and pushing upper limits further provides crucial tests for any corresponding
theoretical model, e.g., SUSY.
Up to now, EDM searches focused on neutral systems (neutrons, atoms, and molecules).
Storage rings, however, o?er the possibility to measure EDMs of charged particles by observing
the in
uence of the EDM on the spin motion in the ring [1, 2, 3]. Direct searches of proton
and deuteron EDMs bear the potential to reach sensitivities beyond 10E-29 e cm. Since the
Cooler Synchrotron COSY at the Forschungszentrum Julich provides polarized protons and
deuterons up to momenta of 3.7 GeV/c, it constitutes an ideal testing ground and starting
point for such an experimental program.
The collaboration is presently aiming at a ?rst direct (precursor) measurement of the
deuteron EDM in COSY[4], using an RF Wien ?lter that was speci?cally designed for that
purpose [5, 6, 7]. Beyond that, the technical design of a prototype EDM storage ring [8]
constitutes the next major milestone of the JEDI research program, which shall be addressed
together with CERN in the framework of a newly formed CPEDM collaboration1.
The talk will present the JEDI plans for the measurement of charged hadron EDMs, and
discuss the various technical developments, and also show recent results.

Speakers: Dr Frank Rathmann (Institute for Nuklear Physik, Forschungszentrum Jülich), Dr Alexander Nass (Institute for nuclear physics, Forschungszentrum Jülich)
• 2:40 PM
First result from beam tests at PSI 20m

In 2019 we have measured the beam profiles of two potential muon beamlines at PSI. These measurements will permit the extraction of the transverse phase space for calculations of injection into a compact storage ring.

Speaker: Mikio Sakurai (ETH Zürich)
• 3:00 PM 3:30 PM
Coffee 30m
• 3:30 PM 4:30 PM
Storage ring dynamics: Storage rings: Magnetic field design and control WHGA 001

### WHGA 001

Convener: Philipp Schmidt-Wellenburg (Paul Scherrer Institut)
• 3:30 PM
Radial magnetic field measurements in the Muon g-2 experiment at FNAL 40m

The muon g-2 experiment at Fermi National Accelerator Laboratory (FNAL E989) is using a super-ferric magnet to generate the nominally vertical precision magnetic field of 1.45 T which confines the muon beam in the horizontal plane (radial direction). A segmented electrostatic quadrupole system is employed to prevent the muon beam from spiraling out of the storage region in the vertical direction and to center the muon beam in the nominal storage orbit volume defined by physical beam collimators. A non-vanishing horizontal magnetic field component displaces the muon beam center from the geometric center of the muon storage region, shrinking the effective muon storage volume and leading to complications in the control of several systematic effects related to the dynamics of the muon beam. The presentation will describe the instrumentation developed to measure the radial magnetic field during the commissioning of the muon storage ring magnet, the passive means implemented to reduce the averaged radial magnetic field component, and the surface coil current system used to actively compensate the radial field components during science data run time.

Speaker: Prof. Martin Fertl (Johannes Gutenberg Universität Mainz)
• 4:30 PM 5:45 PM
Break-out groups discussions: Constituation of break-out groups WHGA 121, WBBA 003, WBBA 008, WBBA 012

### WHGA 121, WBBA 003, WBBA 008, WBBA 012

• Tuesday, February 18
• 9:00 AM 10:30 AM
EDM in storage rings: Muon EDM in JPARC and at FNAL WBGB 019

### WBGB 019

Convener: Angela Papa (Paul Scherrer Institut)
• 9:00 AM
The muon EDM measurement at Fermilab 40m

An overview of the forthcoming measurement of the muon EDM using the g-2 storage ring at Fermilab. The new tracking detectors, together with improved segmented calorimeters, allow for increased sensitivity to a precession plane tilt.

Speaker: Joe Price (University of liverpool)
• 9:50 AM
Status of muon EDM experiment at J-PARC 40m

I will present the status and prospects of the muon EDM experiment by using a reaccelerated thermal muon beam at J-PARC

Speaker: Dr Tsutomu Mibe (KEK)
• 10:30 AM 11:00 AM
Coffee 30m
• 11:00 AM 11:40 AM
EDM in storage rings WBGB 019

### WBGB 019

• 11:00 AM
Search for EDM of unstable particles at the LHCb 40m
Speaker: Dr Nicola Neri (INFN Milano)
• 11:40 AM 12:30 PM
Particle triggering, detection and tracking WBGB 019

### WBGB 019

• 11:40 AM
The MuPix Pixel Sensors, the Mu3e DAQ and tracking in multiple-scattering dominated environments 40m

The Mu3e collaboration is building an ultra thin ~300 million pixel tracking detector in order to search for the the lepton-flavour violating decay of a positive muon to two positrons and and an electron at PSI. To this end, we have designed and tested a series of high-voltage active monolithic pixel sensors (HV-MAPS), the MuPix chips. The talk will present results from the latest fully characterized prototype, the MuPix8 and give an outlook to the MuPix10 chip expected for this summer. It will also discuss some insights into tracking in multiple Coulomb scattering dominated envionments gained by Mu3e and bits and pieces of the Mu3e data acquisition system that might be useful for a muon EDM experiment.

Speaker: Niklaus Berger (Mainz University, Insititute for Nuclear Physics)
• 12:30 PM 2:00 PM
Lunch 1h 30m
• 2:00 PM 3:25 PM
Facility tour: HIPA and muon beam visit
• 3:25 PM 4:00 PM
Coffee 35m
• 4:00 PM 4:50 PM
Particle triggering, detection and tracking WBGB 019

### WBGB 019

Convener: Niklaus Berger (Mainz University, Insititute for Nuclear Physics)
• 4:00 PM
DMAPS technologies for uEDM positron tracker 25m

A short summary of technologies for Depleted Monolithic Pixel Sensors (DMAPS) will provided in the talk.

Speakers: Malte Backhaus (ETHZ - ETH Zürich), Branislav Ristic (ETH Zurich)
• 4:25 PM
Development of a Dedicated Precision Polarimeter for Charged Particle EDM searches at COSY 25m

The international JEDI (Jülich Electric Dipole moment Investigation) collaboration is preparing a first-ever direct measurement of the deuteron Electric Dipole Moment (EDM), using the COSY storage ring at Forschungszentrum Jülich (Germany).
A new polarimeter is required to detect the very slow and minuscule polarization change with time: starting
in 2016, we have designed, built and commissioned a new modular type storage ring EDM polarimeter based
on LYSO inorganic scintillator crystals. The polarimeter concept exploits LYSO modules (3x3x8 cm3), individually coupled to modern large area SiPM arrays which are operating at low voltage.
The detector system and its vacuum system have radial symmetry and a thin exit window, making the polarimeter very efficient for online up-down and left-right asymmetry measurements.
After several tests at the external COSY beam, we have recently installed the complete system in the COSY ring for use with internal beams.
In this talk, I will summarize the achievements of our group and discuss the latest results.

Speaker: Irakli Keshelashvili (Forschungszentrum Juelich)
• 4:50 PM 5:50 PM
Break-out groups discussions: Discussion in groups I WBBA 003, WBBA 008, WBGB 019, WBGB 020

### WBBA 003, WBBA 008, WBGB 019, WBGB 020

• 6:00 PM 9:00 PM
Dinner 3h

Fondue

• Wednesday, February 19
• 9:00 AM 10:30 AM
Storage ring dynamics: Beam elements (Magnets and Electrodes) WBGB 019

### WBGB 019

Convener: Martin Fertl (Johannes Gutenberg Universität Mainz)
• 9:00 AM
Polarized Beams at RHIC, and Electron Beams at the Future EIC 40m

A status of polarized proton beams at RHIC, and on-going 3He developments. Review of polarized beam plans and studies for the EIC, including electron beam transfer, acceleration, and polarization lifetime at store. Add some insight into spin dynamics computational tools and methods.

Speaker: Francois Meot (Brookhaven National Laboratory)
• 9:45 AM
The magnetic field measurement for the Muon g-2 experiment with precision NMR 40m

The Muon g-2 experiment E989 at Fermilab will measure the anomalous magnetic moment of the muon, a$_\mu$, with about four times better precision than former experiments. The aim is to resolve the discrepancy of more than 3 standard deviations between the previous measurements dominated by the Brookhaven E821 result and the Standard Model calculation of a$_\mu$.
The experimental concept uses a polarized muon beam at the magic momentum which is stored in the extremely homogeneous magnetic field of the storage ring. Parity violation in the weak decay is used as a spin analyzer; the detected rate of the decay electrons oscillates with the frequency, $\omega_a$, in the magnetic field expressed in terms of the equivalent free proton Larmor frequency, $\omega_p$. Since a$_\mu$ is derived from the ratio of $\omega_a$ and $\omega_p$, both are equally important and systematic uncertainties must be kept below 70 ppb for each observable.
A magnetic field measurement system was developed to measure the magnetic field experienced by the muons. A set of 378 new Nuclear Magnetic Resonance (NMR) probes constantly monitor the field at all times around the storage ring. An upgraded in-vacuum field mapping system scans the muon storage region over the full azimuth of the magnet. A special water-based NMR probe which has a well-measured geometry and low magnetic perturbation was designed to calibrate the probes of the field mapping system. All systems were successfully commissioned, and were in full operation for the first physics data taking runs in 2018 and 2019. This presentation will provide details of the challenging measurement and analysis of the averaged magnetic field and discuss aspects that will be relevant for the future muon EDM measurement. The special challenges of the radial field measurement will be discussed in a separate talk at this workshop.

Speaker: Dr Peter Winter (Argonne National Laboratory)
• 10:30 AM 11:00 AM
Coffee 30m
• 11:00 AM 12:00 PM
Break-out groups discussions: Summary of discussion and concepts WBGB 020, WSLA 008, WSLA 105

### WBGB 020, WSLA 008, WSLA 105

• 12:00 PM 1:35 PM
Lunch 1h 35m
• 1:35 PM 2:40 PM
Particle triggering, detection and tracking: Scintillators WBGB 019

### WBGB 019

Convener: Gavin Hesketh (UCL)
• 1:35 PM
Scintillator based detector developments for the most recent muon physics searches 40m

Plastic scintillators (including scintillating fibers) coupled to photosensors provide flexible, fast and high granularity detectors which are able to work in high rate environment. The advent of Silicon PhotoMultipliers (SiPMs) has had a strong impact in the development of what we can call a new age" of plastic scintillator based detectors. Improved detector performances (better spatial and timing resolutions) can be reached with respect to previous detectors, where PhotoMultipliers (PMs) were used, thanks namely to (1) the small photosensor size which allows to couple each single element to its own SiPM and (2) the reduced transit time spread of the photosensor itself. The straightforward application of such a detectors is as a trigger tools. Furthermore the possibility of using SiPMs in magnetic fields strongly simplifies the implementation of such detectors used as tracker devices or to complement the latter, where usually a magnetic field is needed. Finally new beam monitoring detectors able to sustain very high beam intensities can be built. In this talk a review of scintillator based detectors used on the most recent muon physics searches will be given.

Speaker: Angela Papa (Paul Scherrer Institut)
• 2:40 PM 3:00 PM
Coffee 20m
• 3:00 PM 4:40 PM
Break-out groups discussions: Workshop summary presentations of concepts WBGB 019

### WBGB 019

• 4:40 PM 4:45 PM
End Of Workshop 5m