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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Search for long-lived particles decaying to final states with a pair of muons in proton-proton collisions at $ \sqrt{s} $ = 13.6 TeV

An inclusive search for long-lived exotic particles (LLPs) decaying to final states with a pair of muons is presented. The search uses data corresponding to an integrated luminosity of 36.6 fb$^{−1}$ collected by the CMS experiment from the proton-proton collisions at $ \sqrt{s} $ = 13.6 TeV in 2022, the first year of Run 3 of the CERN LHC. The experimental signature is a pair of oppositely charged muons originating from a secondary vertex spatially separated from the proton-proton interaction point by distances ranging from several hundred μm to several meters. The sensitivity of the search benefits from new triggers for displaced dimuons developed for Run 3. The results are interpreted in the framework of the hidden Abelian Higgs model, in which the Higgs boson decays to a pair of long-lived dark photons, and of an R-parity violating supersymmetry model, in which long-lived neutralinos decay to a pair of muons and a neutrino. The limits set on these models are the most stringent to date in wide regions of lifetimes for LLPs with masses larger than 10 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Probing the CP structure of the top quark Yukawa at the future muon collider

We study the top-Higgs coupling with a CP violating phase ξ at a future multi-TeV muon collider. We focus on processes that are directly sensitive to the top quark Yukawa coupling: $t$$\overline{t}$$h$, $tbhμν$, and $t$$\overline{t}$$h$$v$$\overline{v}$ with $h$ → $b$$\overline{b}$ and semileptonic top decays. At different energies, different processes dominate the cross section, providing complementary information. At and above an energy of $\mathcal{O}$(10) TeV, vector boson fusion processes dominate. As we show, in the Standard Model there is destructive interference in the vector boson fusion processes $t$$\overline{t}$$h$$v$$\overline{v}$ and $tbhμν$ between the top quark Yukawa and Higgs-gauge boson couplings. A CP-violating phase changes this interference, and the cross section measurement is very sensitive to the size of the CP-violating angle. Although we find that the cross sections are measured to $\mathcal{O}$(50%) statistical uncertainty at 1σ, a 10 and 30 TeV muon collider can bound the CP-violating angle |ξ| ≲ 9.0° and |ξ| ≲ 5.4°, respectively. However, cross section measurements are insensitive to the sign of the CP-violating angle. To determine that the coupling is truly CP violating, observables sensitive to CP-violation must be measured. We find in the $t$$\overline{t}$$h$ process the azimuthal angle between the $t$ + $\overline{t}$ plane and the initial state muon+Higgs plane shows good discrimination for ξ = ±0.1π.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

The new physics case for beam-dump experiments with accelerated muon beams

As the field examines a future muon collider as a possible successor to the LHC, we must consider how to fully utilize not only the high-energy particle collisions, but also any lower-energy staging facilities necessary in the R&D process. An economical and efficient possibility is to use the accelerated muon beam from either the full experiment or from cooling and acceleration tests in beam-dump experiments. Beam-dump experiments are complementary to the main collider as they achieve sensitivity to very small couplings with minimal instrumentation. We demonstrate the utility of muon beam-dump experiments for new physics searches at energies from 10 GeV to 5 TeV. We find that, even at low energies like those accessible at staging or demonstrator facilities, it is possible to probe new regions of parameter space for a variety of generic BSM models, including muonphilic, leptophilic, L μ − L τ , and dark photon scenarios. Such experiments could therefore provide opportunities for discovery of new physics well before the completion of the full multi-TeV collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

First measurement of differential cross sections for muon neutrino charged current interactions on argon with a two-proton final state using the MicroBooNE detector

We present the first measurement of differential cross sections for charged-current muon neutrino interactions on argon with one muon, two protons, and no pions in the final state. These final states are dominated by two-nucleon knockout interactions, which are complicated to model and for which there is currently limited information about the characteristics of these interactions in existing neutrino-nucleus scattering data. Detailed investigations of two-nucleon knockout are vital to support upcoming experiments exploring the nature of the neutrino. Among the different kinematic quantities measured, the opening angle between the two protons, the angle between the total proton momentum and the muon, and the total transverse momentum of the final state system are most sensitive to the underlying physics processes as embodied in various theoretical models.

2-particle 2-hole states↗
DOE OSTI2025

Latest results of the Muon g-2 experiment at Fermilab

The muon magnetic anomaly, aμ = g - 2/ 2, is a low-energy observable which can be both measured and computed to high precision, making it a sensitive test of the Standard Model and a probe for new physics. The Muon g − 2 experiment at Fermilab aims to measure aμ with a final accuracy of 140 parts per billion (ppb). The experiment is based on the measurement of the muon spin anomalous precession frequency, ωa, in a magnetic field. The first result of the experiment, based on the 2018 data-taking campaign, was published in 2021 and it confirmed the previous result obtained at Brookhaven National Laboratory with a similar sensitivity of 460 ppb. In this proceeding, the result based on the 2019 and 2020 datasets is presented and the improvement in the accuracy with respect to the 2018 dataset are discussed.

Sorbara, Matteo [INFN, Rome2; Rome U., Tor Vergata↗
DOE OSTI2025

Muon tagging with flash ADC waveform baselines

Here, this manuscript describes an innovative method to tag muons using the baseline information of the Flash ADC (FADC) waveform of PMTs in the JSNS 2 (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) experiment. The experiment is designed to search for evidence of sterile neutrinos, and a reliable method for muon tagging is an essential component for background rejection because the detector is located above ground, on the 3rd floor of the J-PARC Material and Life Science Experimental Facility (MLF). Cosmogenic muons that stop within the detector volume and produce a Michel electron are a particularly important background that must be rejected for our sterile neutrino search. Utilizing this innovative method, more than 99.8 % of Michel electrons can be rejected even without using information from the detector’s veto region PMTs. This technique can be employed by any experiments which uses a similar detector configuration.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Search for 𝑏-hadron decays to long-lived particles in the CMS endcap muon detectors

A search for long-lived particles originating from the decay of 𝑏 hadrons produced in proton-proton collisions with a center-of-mass energy of 13 TeV at the LHC is presented. The analysis is performed on a dataset recorded in 2018, corresponding to an integrated luminosity of 41.6 fb −1 . Interactions of the long-lived particles in the CMS endcap muon system would create hadronic or electromagnetic showers, producing clusters of detector hits. Selected events contain at least one such high-multiplicity cluster in the muon endcaps and require the presence of a displaced muon. The most stringent upper limits to date on the branching fraction ℬ⁡(𝐵 →𝐾⁢Φ), where the long-lived particle Φ decays to a pair of hadrons, are obtained for Φ masses of 0.3–3.0 GeV and Φ mean proper decay lengths in the range of 1–500 cm.

Hayrapetyan, A. [Yerevan Physics Institute]↗
DOE OSTI2025

Measurement of muon neutrino induced charged current interactions without charged pions in the final state using a new T2K off-axis near detector WAGASCI-BabyMIND

We report a flux-integrated cross section measurement of muon neutrino interactions on water and hydrocarbon via charged current reactions without charged pions in the final state with the WAGASCI-BabyMIND detector, which was installed in the T2K near detector hall in 2018. The detector is located 1.5° off-axis and is exposed to a more energetic neutrino flux than ND280, another T2K near detector, which is located at a different off-axis position. The total flux-integrated cross section is measured to be 1.26 ± 0.18⁢(stat+syst) × 10 −39 cm 2 /nucleon on CH and 1.44 ± 0.21⁢(stat+syst) × 10 −39 cm 2 /nucleon on H 2 ⁡O. These results are compared to model predictions provided by the neut v5.3.2 and genie v2.8.0 Monte Carlo generators and the measurements are compatible with these models. Differential cross sections in muon momentum and cosine of the muon scattering angle are also reported. This is the first such measurement reported with the WAGASCI-BabyMIND detector and utilizes the 2020 and 2021 datasets.

lepton-hadron interactions↗
DOE OSTI2024

Diphoton signals of muon-philic scalars at DarkQuest

We analyze the capability of the DarkQuest proton beam-dump experiment at Fermilab to discover new light resonances decaying into photons. As an example model, we focus on muon-philic scalar particles that decay to photons. This is one of the few minimal models that can address the ( g − 2 ) μ anomaly at low mass. These scalars can be copiously produced by meson decays and muon bremsstrahlung. We point out that thanks to DarkQuest’s compact geometry, muons can propagate through the dump and efficiently produce dark scalars near the end of the dump. This mechanism enables DarkQuest to be sensitive to both long-lived and prompt scalars. At the same time, diphoton signatures are generically not background free, and we discuss in detail the different sources of background and strategies to mitigate them. We find that the backgrounds can be sufficiently reduced for DarkQuest to test currently viable ( g − 2 ) μ parameter space. Published by the American Physical Society 2024

Blinov, Nikita (ORCID:000000022845961X)↗
DOE OSTI2025

Neutrino-portal dark matter detection prospects at a future muon collider

With no concrete evidence for nongravitational interactions of dark matter to date, it is natural to wonder whether dark matter couples predominantly to the Standard Model (SM)’s neutrinos. Neutrino interactions (and the possible existence of additional neutrinophilic mediators) are substantially less understood than those of other SM particles, yet this picture will change dramatically in the coming decades with new neutrino sources. One potential new source arises with the construction of a high-energy muon collider (MuCol); due to muons’ instability, a MuCol is a source of high-energy collimated neutrinos. Importantly, since the physics of muon decays (into neutrinos) is very well-understood, this leads to a neutrino flux with systematic uncertainties far smaller than fluxes from conventional high-energy (proton-sourced) neutrino beams. In this work, we study the capabilities of a potential neutrino detector, “ MuCol ν ”, placed ∼ 100 m downstream of the MuCol interaction point. The MuCol ν detector would be especially capable of searching for a neutrinophilic mediator ϕ through the mononeutrino scattering process ν μ N → μ + ϕ X , exceeding searches from other terrestrial approaches for m ϕ in the ∼ few MeV- ten GeV range. Even with a 10 kg-yr exposure, MuCol ν is capable of searching for well-motivated classes of thermal freeze-out and freeze-in neutrino-portal dark matter. Published by the American Physical Society 2025

Adhikary, Jyotismita (ORCID:0000000253894170)↗
DOE OSTI2025

Aspects of Higgs Physics at a $\sqrt{s}=3$ TeV Muon Collider with detailed detector simulation

The Muon Collider is one of the most promising future collider facilities with the potential to reach multi-TeV center-of-mass energy and high luminosity. Due to the significant Higgs boson production cross section in muon-antimuon collisions at such high energies, the collider offers an excellent opportunity for in-depth exploration of Higgs boson properties. It holds the capability to significantly advance our understanding of the Higgs sector to a very high level of precision. However, the presence of beam-induced background resulting from the decay of the beam muons poses unique challenges for detector development and event reconstruction. In this paper, the prospects for measuring various Higgs boson properties at a center-of-mass energy of 3 TeV are presented, using a detailed detector simulation in a realistic environment. The study demonstrates the feasibility of achieving high precision results with the current state-of-the-art detector design. In addition, the paper discusses the detector requirements necessary to achieve this level of accuracy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Proposed muon collider R&D at SNS

Generation of a muon beam at a Muon Collider requires relatively short, high-charge proton bunches. They are produced in a high-average-power proton driver by first accumulating a proton beam from a super-conducting linac, then bunching the beam and finally compressing and combining the bunches into a single high-intensity proton pulse. All of these beam formation stages involve handling of unprecedentedly high beam charges. Validation of these intricate beam manipulations requires better understanding of extreme space-charge effects and experimental demonstration. A facility perhaps most closely resembling the proton driver configuration and beam parameters is the Spallation Neutron Source (SNS) accelerator complex at Oak Ridge National Laboratory (ORNL). Considering the energy scaling of the space-charge parameters, many of the beam formation steps planned for the proton driver can be experimentally checked at the SNS at the relevant space-charge interaction levels. This paper discusses potential proton driver and other muon-collider-related R\&D at the SNS.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

On Final Results From the Muon $g\mathrm{-}2$ Experiment at Fermilab

The Muon g-2 Experiment at Fermilab has measured the muon anomalous magnetic moment, a_mu, with unprecedented precision, leveraging a dataset from Runs 1 6 that is 21 times larger than its Brookhaven predecessor. This talk will present the experiment s final result, which serves as a benchmark for testing the Standard Model with high precision. The measurement was performed in a storage ring with a highly uniform magnetic field, where precise beam dynamics understanding is vital to determine the muon anomalous precession frequency. Key to this effort were advanced simulation tools including COSY INFINITY, precise fringe field modeling, and calculations of beam dynamics characteristics like tunes and chromaticity. We will conclude by exploring how the experiment's findings reshape our understanding of particle physics.

Valetov, Eremey [Michigan State U.]↗
DOE OSTI2025

Simulating Muon Capture with MARLEY

Core-collapse supernovae are intense sources of tens-of-MeV neutrinos. Each explosion releases about 1058 neutrinos in a burst lasting tens of seconds. As neutrinos are weakly interacting, they escape more easily compared to photons, allowing them to be observed before the light signal. Understanding low-energy neutrino interactions with argon will be critical for future supernova measurements with the Deep Underground Neutrino Experiment (DUNE). Interpreting future DUNE supernova neutrino data will require a high-quality model of O(10 MeV) neutrino interactions, but the dominant charged-current cross section has never been measured at these low energies for an argon target. We exploit the theoretical similarities between muon capture, which has been measured, and antineutrino scattering to test MARLEY (Model of Argon Reaction Low Energy Yields), the simulation code used by DUNE to model supernova neutrino reactions. I implemented C++ code to add a muon capture mode to MARLEY and compared the predictions of the new simulation to measured isotope branching ratios of the residual nuclei. The preliminary branching ratios predicted by MARLEY running in muon capture mode demonstrate promising baseline performance when compared to experimental data and are expected to improve with further model adjustments.

Wong, Baker Louie↗
DOE OSTI2025

Laser calibration system and lost muons correction in the g-2 experiment

The Muon g-2 experiment at Fermilab has the main goal to measure the muon anomalous magnetic moment $a_{µ}$ = ($g$ − 2)/2 to a precision of 0.14 parts per million (ppm), which means 4 times improvement in precision with respect to the final result from BNL: $a_{µ}$ (expt. BNL) = 11659208.0(6.3) × 10$^{−10}$ (0.54 ppm) In this report I summarize the work done at the $g$-2 experiment during my summer internship at Fermilab. In the first two weeks my first task has been to replace the NIM logic used in the Laser Calibration System with a new FPGA. Then, I was involved in the Lost Muons analysis studying both real data and MonteCarlo simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Measurement of the Kicker transient magnetic field in the Muon g-2 Experiment at Fermilab

The Muon g-2 experiment at Fermilab has the main goal to measure the muon anomalous magnetic moment $a_µ = \frac{g−2}{2}$ to a precision of 140 parts per billion (ppb), which means 4 times improvement in precision with respect to the final result from BNL: a µ (expt.B N L) = 11659208.0(6.3)×10 −10 (540 ppb) So far only RUN1 data have been analyzed showing the following improvement: a µ (expt.RU N1) = 116592061×10 −11 (465 ppb) In this report I summarize the work done at the g-2 experiment during my summer internship at Fermilab where I worked on the attempt to estimate the kicker transient field contribution in the Muon g-2 experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Neutrino Physics at a Muon Collider, and the Neutrino Kaleidoscope

Muon accelerators, a potential technology for enabling O(10 TeV) parton center of mass energy collisions, would also source an intense, collimated beam of neutrinos at TeV energies. There is currently a renewed effort to understand the possible scientific reach of such a neutrino beam in the context of neutrino physics. One possibility is the “Neutrino Kaleidoscope”: the pairing of a muon accelerator neutrino flux with a neutrino telescope detector. In particular, such a pairing would enable searches for non-standard oscillations of the beam neutrinos as they traverse the earth between source and detector. These non-standard neutrino oscillations could be sourced by Lorentz invariance violation, which a neutrino kaleidoscope could probe up to the quantum gravity-motivated Planck scale. Such a search would also have a reach on sterile neutrinos orders of magnitude beyond existing terrestrial limits. In this talk, I will introduce some of the exciting measurements being proposed with the neutrinos from a muon accelerator and then go into detail on the Neutrino Kaleidoscope concept (arxiv:2508.09249).

Putnam, Gray [Fermilab]↗
DOE OSTI2025

High-Multiplicity Muon Airshower Analysis at NOvA Far Detector

We process and analyze muon airshower data from the NOvA far detector using various image processing algorithms, such as Fast Fourier Transformation, and Hough line transformation. From the processed event images, we calculate multiple parameters for our study. We are looking for physics features, including East-West Asymmetry, anisotropies in right ascension, and seasonal variation. Additionally, we have developed an algorithm to count the multiplicity of muons in the airshower events using the single muon data.

Lima, Aklima Khanam [Syracuse U.]↗