Muon4Future 2025

26 May 2025, 09:00 → 30 May 2025, 19:00 Europe/Rome

Palazzo Franchetti (Venezia, Istituto Veneto di Lettere, Scienze ed Arti - Palazzo Franchetti)

Donatella Lucchesi (Istituto Nazionale di Fisica Nucleare)

Muon4Future 2025 (Second edition)

The first edition of the Muon4Future workshop in 2023 emphasized the importance of live discussions on muon-based experiments, fostering collaboration between experimental and theoretical communities. The second edition aims to deepen comparisons between the latest results from muon-based experiments and Standard Model predictions. Furthermore, the workshop will continue to evaluate the muon beam technologies required for next-generation experiments and the research and development planned for future proposals. The ultimate goal is to identify the most promising physics experiments and measurements to further test the Standard Model and explore new physics, while addressing innovative ideas, relevant issues, and associated challenges.

The Workshop will be held in presence in Venice, at "Palazzo Franchetti" of the “Istituto Veneto di Scienze, Lettere ed Arti”.

                       

The Workshop is organized by INFN-Sezione di Padova with the support of the Physics and Astronomy Department of Padova University and the contribution of the INFN Headquarter
 

                                                                      

                                                

 

01_Muon4Future Workshop_Bulletin 1.pdf

Monday, 26 May

1 Registration and welcome buffet

A light lunch will be offered while registration at the secretariat desk is going on.

2 Welcome

3 What happened since the last edition: theory

4 What happened since the last edition: experiment

5 Goal of this workshop edition

16:00 Coffee Break

Muon facilities

6 Design and Prospect of the MELODY project in China

7 Advancement of the PSI muon facility

8 Advancement of the J-PARC muon facility

Speaker: Naritoshi Kawamura

9 Advancement of the Fermilab muon facility

10 Discussion

Tuesday, 27 May

Muon facilities

11 Advancement of the TRIUMF muon facility

12 Advancement of the ISIS muon facility

13 The ELI beamlines for muon applications

Speaker: Roberto Versaci (ELI-Beamlines)

14 The future of muon beams at CERN

Speaker: Dipanwita Banerjee (CERN)

11:00 Coffee Break

Muon facilities

15 Discussion/Flash talks

Muon Beams Technologies

16 Study and result of target for muon production

Speaker: Michael Hedges (Fermilab)

17 Result of muon cooling at PSI

Speaker: Giuseppe Lospalluto (ETH Zurich)

13:00 Lunch break

Muon Beams Technologies

18 Results on muon cooling at acceleration at J-PARC

19 Development in muon ionizing cooling

20 Muon beams acceleration

21 Muon beams manipulation with crystals

Speaker: Andrea Mazzolari (Istituto Nazionale di Fisica Nucleare)

22 Flash talks

16:30 Coffee Break

Charge Lepton Flavor Violation

23 Muons at the intensity frontier

Speaker: Diego Redigolo (Istituto Nazionale di Fisica Nucleare)

24 Theory overview of charge lepton flavor violation

25 New theory perspectives in charge lepton flavor violation

26 Summary of the workshop in Trento

27 Probing charged lepton flavor violation and quantum entanglement in muon on-target experiments

Firstly, we'd like to share a novel and cost-effective experiment proposal to probe the charged lepton flavor violation (CLFV) process mediated by an extra massive neutral gauge boson $Z'$ beyond the Standard Model, as a part of the Peking University Muon (PKMuon) Experiment. The considered process can be uniquely sensitive to specific CLFV parameter combinations, such as the coupling coefficient product $\lambda_{e\mu}\lambda_{\mu\mu}$. Additionally, we will present a realistic proposal and a comprehensive study of quantum entanglement in a state composed of different-flavor fermions in muon-electron scattering. Entanglement in the resulting muon-electron qubit system and the violation of the Bell inequality can be observed with a high event rate. This paves the way for performing quantum tomography with muons.

Speaker: Mr Leyun Gao (Peking University)

28 Fundamental symmetry violations in charged-lepton flavor-changing processes

In this talk, I describe how worldwide experimental searches for charged-lepton flavor-changing processes also provide new opportunities for discovering violations of Lorentz and CPT invariance. Model-independent effective interactions describing perturbative Lorentz and CPT violation have been investigated in electromagnetic muon and tau decays, and coherent muon-to-electron conversion in nuclei. Results from the MEG, BaBar, and SINDRUM II experiments have enabled hundreds of first constraints on coefficients parametrizing time-independent signals of Lorentz and CPT violation. Future experiments, including MEG II, COMET, and Mu2e, are projected to increase these constraints by up to two orders of magnitude. I also outline how time-dependent modulations of transition rates, which remain completely unexplored and are uniquely characteristic of Lorentz and CPT violation, can be probed.

Speaker: Nathaniel Sherrill

Wednesday, 28 May

Charge Lepton Flavor Violation

29 Status and perspectives of MEG2 experiment

30 Status and perspectives of Mu2e experiment

31 Status and perspectives of COMET experiment

10:30 Coffee Break

Charge Lepton Flavor Violation

32 Status and perspectives of Mu3e experiment

33 Pulling out all the Stops: Measuring the normalisation of signal events in the Mu2e experiment

Speaker: George Sweetmore (The University of Manchester)

Muon dipole moments

34 The RadioMonteCarLow 2 community effort

Speaker: Adrian Signer (PSI, Villigen)

35 Lattice calulations for muon dipole moments

12:40 Lunch Break

Muon dipole moments

36 Summary of theory

37 Latest results of g-2 experiment

Speaker: Marco Incagli (Istituto Nazionale di Fisica Nucleare)

38 muonEDM status/result from Fermilab

Speaker: Anna Driutti

39 Staus of g-2 and muonEDM at J-PARC

16:00 Coffee Break

Muon dipole moments

40 Status of muonEDM at PSI

41 Status of MuOnE experiment

Speaker: Eugenia Spedicato (Istituto Nazionale di Fisica Nucleare)

42 Flash talks

Thursday, 29 May

New Physics oppportunities with low and high energy muon beams

43 Physics with muTRISTAN

Speaker: Ryutaro Matsudo (KEK)

44 Latest results of NA64-mu

Speaker: Laura Molina Bueno (ETHZ)

45 Results and perspectives with muonioum experiments

Speaker: Mr Naritoshi Kawamura

46 Physics of FAMU

Speaker: Mr Alessandro Menegoli

11:00 Coffee Break

New Physics oppportunities with low and high energy muon beams

47 Physics perspectives at the ion-muon collider

Speaker: Prof. Darin Acosta

48 Theory overview of physics possibilities with low energy muon beams

49 Theory overview of physics possibilities with high energy muon beams

Speaker: David Marzocca (Istituto Nazionale di Fisica Nucleare)

13:00 Lunch break

New Physics oppportunities with low and high energy muon beams

50 Searches for heavy neutrinos at multi-TeV muon collider: a resonant leptogenesis perspective

In this work, the Standard Model (SM) is
extended with two right-handed (RH) neutrinos and two
singlet neutral fermions to yield active neutrino masses via
(2,2) inverse see-saw mechanism. We first validate the multi-
dimensional model parameter space with neutrino oscillation
data, obeying the experimental bounds coming from the lep-
ton flavor violating (LFV) decays: μ → eγ, τ → eγ, τ →
μγ. Besides we also search for the portion of the parame-
ter space which yield the observed baryon asymmetry of the
universe via resonant leptogenesis. Further, we pick up a few
benchmark points from the aforementioned parameter space
with TeV scale heavy neutrinos and perform an exhaustive
collider analysis of the final states: 2l +ET / and 1 l +2 j + ̸ ET
in multi-TeV muon collider.

Speaker: HIMADRI ROY (CENTRAL CHINA NORMAL UNIVERSITY)

51 Higgs self coupling at a 10 TeV Muon Collider

The 2025 ESPPU highlights the extended characterization of the Higgs potential as a priority for future experiments, as it allows the determination of the Standard Model vacuum stability and the test of various Beyond Standard Model hypotheses, paving the way for the study of the electroweak phase transition in the early Universe. A 10 TeV Muon Collider is predicted to produce O(10^4) double Higgs events in 5 Snowmass-years of operation. This and its relatively clean collision environment would allow a Muon Collider to measure the Higgs self-coupling down to the percent level. Also, a 10 Snowmass-years run could enable the determination of the Higgs’ quartic coupling, with an uncertainty of about 50%. This contribution discusses the expected accuracy of the double Higgs cross-section at a 10 TeV Muon Collider using detailed detector simulations, including physics and machine backgrounds.

Speaker: Leonardo Palombini (Istituto Nazionale di Fisica Nucleare)

52 Search for light Dark Sectors with the HIAF Muon Beam: HFRS-PKMu experiment proposal

Sub-GeV light dark matter usually requires the existence of new light mediators, such as the dark Z boson in the $L_\mu - L_\tau$ gauge theory. Here we study the search potential for such a Z' boson based on a muon on-target experiment proposal, through $\mu e^- \to \mu e^- X$, with X decays invisibly. The experimental signature would be scattered muon and electron from the target, at large angles compared to backgrounds. Apart from these, activities will be low in the subdetectors located downstream from the interaction point. Here we focus on the usage of the 1-10 GeV muon beam from the HIAF-HFRS facility which is expected to start operation in 2025-2026. Compared with existing experiments or proposals using the CERN 160 GeV muon beam, we find high sensitivity on 10 MeV Z' range.

Speaker: Zijian Wang

53 Muon-decay parameters at COHERENT

We study the most general Lagrangian for muon decay at low energies, including light Dirac right-handed neutrinos ($\nu$WEFT), in the COHERENT experiment at the Spallation Neutron Source at Oak Ridge National Laboratory. Using the COHERENT data, we derive the first direct constraint on the Michel parameters governing the $\bar\nu_\mu$ energy distribution. We also discuss future sensitivities and assess the implications for the Lorentz structure of the interactions mediating muon decay.
We thus demonstrate that Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) measurements at spallation sources are valuable probes of muon decay physics.

Speaker: Sergio de la Cruz Alzaga (IFIC (CSIC-Universidad de Valencia))

54 Prospects for true muonium observation at existing beamlines and colliders

True muonium (TM), the bound state of a muon and an antimuon, remains unobserved due to its short lifetime and production cross-sections, together with its extremely high (13$Z^2$) dissociation cross-section in matter. Recent theoretical and experimental studies have, however, identified feasible pathways to its discovery at current high-energy physics facilities.

At the LHCb experiment, the production of the vector 1S TM state via $\eta \to \gamma TM$ with subsequent $TM \to e^+e^-$ decay has been proposed in 2019. Preliminary studies suggested that a displaced $e^+e^-$ vertex search could achieve a significance exceeding five standard deviations thanks to the large LHC-Run3 statistics.

In 2024 a resonant search for true muonium via $e^+e^- \to TM \to e^+e^-$ interactions has been proposed, using a 43.7 GeV positron beam at the CERN Super Proton Synchrotron (SPS) North-Area H4A beam facility. Simulations indicate that the spin-1 TM state could be observed with high significance with about $10^{12}$ positrons impinging on an assembly of multiple thin lithium targets by searching for displaced $e^+e^-$ vertices, thanks to its large decay-in-flight distance of about 11 cm.

Another method to observe true muonium using $e^+e^-$ interactions, proposed in early 2025, employs photon-photon fusion into the spin-0 TM state (para-TM), decaying into two photons. Thanks to its high integrated luminosity and to the presence of triggers dedicated to photons, the Belle-II experiment, featuring a 10.58 GeV center-of-mass energy, is a very good candidate for this measurement. Monte Carlo simulations incorporating trigger, detector efficiencies and resolutions and background processes suggest that para-TM production via photon-photon fusion is feasible. Applying machine learning techniques, such as extremely randomized trees, to simulated events indicates that the TM signal can be distinguished from background, with projected statistical significances reaching discovery level, using the current dataset of about 400 fb-1 already collected at Belle-II.

Speaker: Ruben Gargiulo (Istituto Nazionale di Fisica Nucleare)

55 Scintillating fibre-based muon beam monitor for the FAMU experiment

The FAMU experiment aims at measuring the Zemach radius of the proton with an accuracy better than 1% through accurate spectroscopy of the ground state hyperfine splitting of muonic hydrogen atoms. This measurement plays a crucial role in validating high-precision QED calculations, and testing the proton-muon interaction. Muonic hydrogen atoms are produced by injecting a pulsed low-momentum (55 MeV/c) negative muon beam in a pressurised 1-litre 8 bar gaseous target. The exotic atoms are let thermalise for a few hundreds of ns and then hit with a tunable mid-infrared laser to excite the transition. The experimental data need to be normalised as a function of the muon beam intensity in order to take into account of the number of muonic atoms in the chamber when the laser is injected. This normalisation is made possible thanks to a beam monitor composed of two layers of 1 mm pitch squared fibres, read-out at alternate ends by SiPM’s. This system, initially designed as a position-sensitive hodoscope, proved to be a linear and sensitive flux monitor by taking into account of the total integrated charge collected by the SiPM circuit during beam pulses. This observable has been thoroughly studied in order to check for its linearity and determine its value for single muon interactions. Thanks to dedicated low flux measurements and accurate simulations, the detector has eventually been used as a flux-meter, with a measured resolution below 2%. In addition, the detector played a crucial role in observing beam fluctuations and beamline faults, which can now be promptly corrected as they occur. In conclusion, the FAMU experiment has been provided with a beam monitor capable of beam shape analysis, flux measurement and extraction of time information, which has been playing a crucial role in the data acquisition and data analysis of the experiment. Similar detectors can be applied in other experiments to fully characterise low-momentum muon beams; some specific applications at ISIS are currently under development.

Speaker: Riccardo Rossini (Istituto Nazionale di Fisica Nucleare)

Muons in Other Fields

56 Muon catalysed fusion

Speaker: Mr Takuma Yamashita

57 Measurements of Momentum-Resolved Directional Muon Beams from the Berkeley Lab Laser Accelerator

Speaker: Mr Luc Le Pottier

16:00 Coffee Break

Muons in Other Fields

58 Advanced 2D/3D Muon Spin Rotation Tomography with Si-Pixel Detectors

Speaker: Zaher Salman (PSI)

59 Muography results and perspectives

60 Measuring nuclei with muon-xray

61 A versatile and efficient cosmic muon generator for secondary cosmic-ray muon applications

In the last years, muon radiography (aka muography, based on the flux attenuation) and muon tomography (based on the scattering angle) have made important progress in a wide field of applications, reaching impressive results. And besides these imaging techniques, secondary cosmic ray muons are also used for detector testing and alignment practically in every Nuclear Physics or Particle Physics experiment.
From the simulation point of view, a fair number of cosmic-ray muon generators are already available, based on different software frameworks and on various models of the angular/momentum distribution of the cosmic muons flux. As a matter of fact, the implementation of a realistic flux can make the generator time-consuming, which is a strong limit when high statistics is needed.
Recently, we have developed a new Monte Carlo generator for cosmic-ray muons, named Efficient COsmic MUon Generator (EcoMug), conceived with a particular emphasis on the efficiency (> 10^5 muons generated per second on a standard machine) and on the flexibility (it is supplied with a standard muon angular/momentum distribution implemented by default, but it is expected to be easily reconfigured by the user implementing its own angular/momentum distribution).
Differently from other similar tools, EcoMug is able to generate muons from different kind of surfaces (plane, cylinder and half-sphere), while keeping the correct angular/momentum distribution of generated tracks inside a fiducial volume. This allows to optimise the generation surface according to the system under study, and makes it possible a further improvement of the overall simulation efficiency.
Moreover, this generator is written as a header-only C++11 library, ready to be integrated into whatever C++ code, in particular C++ code based on Geant4 simulation tool.
In this contribution we will briefly present the main features of EcoMug.
References
D. Pagano, G. Bonomi, A. Donzella, A. Zenoni, G. Zumerle and N. Zurlo EcoMug: An Efficient COsmic MUon Generator for cosmic-ray muon applications Nucl.Instrum.Meth. A 1014 (2021) 165732

Speaker: Nicola Zurlo (Università di Brescia e Istituto Nazionale di Fisica Nucleare)

62 High - Intensity Muon Beams (HIMB) project

Currently PSI delivers the most intense continuous muon beam in the world with up to a few 10^8 μ+/s and aims at upgrading its beamlines within the HIMB project to reach intensities of 10^10 μ+/s, with a huge impact for low-energy, high-precision muon experiments. The use of hyperparameter search algorithms in the simulation of the new HIMB beamline layouts has shown that not only the stringent rate requirements can be met, but that higher phase space quality can be achieved.

Speaker: Giovanni Dal Maso (Paul Scherrer Institut - ETH Zürich)

Friday, 30 May

Neutrino Physics with muon beams

63 Theory of neutrino physics overvies

64 Low energy neutrino cross section from muon beams

Speaker: Maria Gabriella Catanesi (Istituto Nazionale di Fisica Nucleare)

65 Nustorm perspectives

Speaker: Stefania Ricciardi

66 TBA

67 TBA

11:30 Coffee Break

68 Conclusions