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DOE OSTI2019

Muon g-2: An Interplay between Beam Dynamics and a Muon Decay Experiment at the Precision Frontier

The Muon g-2 Experiment at Fermilab (E989) will use the higher proton flux delivered by the Fermilab accelerator complex and improvements to the experimental apparatus to measure the anomalous magnetic moment of the muon to unprecedented precision. In addition to the increased statistics beyond the most recent measurement, the experiment relies on detailed understanding of the beam dynamics in the experiment’s storage ring as well as the incoming muon beam properties for proper assessments of systematic errors in the data analysis. Modeling and measurements of beam and storage ring properties, from proton targeting to muon storage, produce a unique unification of particle beam physics with a high energy physics experiment. Here the beam dynamics issues and analysis techniques essential to the g-2 experiment are presented and discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

An X-ray magnetic circular dichroism (XMCD) study of Fe ordering in a synthetic MgAl2O4 – Fe3O4 (spinel – magnetite) solid solution series; implications for magnetic properties and cation site ordering

Fe L2,3-edge XAS and XMCD studies have been used to unravel structural trends in the MgAl2O4–Fe3O4, solid solution where thermodynamic modelling has represented a challenge due to the complex ordering arrangements of the end-members. Partitioning of Fe3+ and Fe2+ between tetrahedral (Td) and octahedral (Oh) sites has been established. In the most Fe-rich samples, despite rapid quenching from a disordered state, Fe2+Td is not present which matches the ordered, inverse spinel nature of end-member magnetite (Mgt) at room-T. However, in intermediate compositions Al and Mg substantially replace Fe and small amounts of Fe2+Td are found, stabilized or trapped by decreasing occurrence of the continuous nearest neighbour Fe – Fe interactions which facilitate charge redistribution by electron transfer. Furthermore, in the composition range ~Mgt0.4-0.9, XAS and XMCD bonding and site occupancy data suggest that nano-scale, magnetite-like Fe clusters are present. By contrast, at the spinel-rich end of the series, Mgt0.17 and Mgt0.23 have a homogeneous long-range distribution of Fe, Mg and Al. These relationships are consistent with the intermediate and Fe-rich samples falling within a wide solvus in this system such that the Fe-clusters occur as proto-nuclei for phases which would exsolve following development of long-range crystalline order during slow cooling. Calculated saturation magnetic moments (Ms) for the Fe-rich samples show excellent agreement with measured values but for the most Mg-rich samples are displaced to slightly higher values; this displacement is due to the presence of abundant Mg and Al disrupting the anti-parallel alignment of electron spins for Fe atoms.

Henderson, C. Michael B.↗
DOE OSTI2023

Skyrmion crystals in the triangular Kondo lattice model

We present a systematic study of the formation of skyrmion crystals in a triangular Kondo Lattice model for generic electron filling fractions. Our results indicate that the four-sublattice chiral antiferromagnetic ordering that was reported more than one decade ago can be understood as the dense limit of a sequence of skyrmion crystals whose lattice parameter is dictated by the Fermi wave-vector. This observation has important implications for the ongoing search of skyrmion crystals in metallic materials with localized magnetic moments.

Wang, Zhentao↗
DOE OSTI2019

Status of the Muon g-2 experiment at Fermilab

The aim of the Muon g-2 g − 2 Experiment at Fermilab (E989) is to measure the muon anomalous magnetic moment ( a_\mu a μ ) with a relative precision of 140 parts-per-billion (ppb). This precision, which is a factor of four improvement from the current experimental result, will allow for a much more stringent test of the Standard Model. This paper present the current status of the experimental measurement of a_\mu a μ after the first physics run.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Light thermal relics enabled by a second Higgs

Sub-GeV thermal relic dark matter typically requires the existence of a light mediator particle. We introduce the light two-Higgs-doublet portal, illustrated by a minimal UV-complete model for sub-GeV dark matter with kinematically forbidden annihilations into leptons. All new physics states in this scenario lie at or below the electroweak scale, affecting Higgs physics, the muon anomalous magnetic moment and potentially neutrino masses. Observation of radiative dark matter annihilation by future MeV gamma-ray telescopes would be key to unambiguously identify the scenario.

Herms, Johannes↗
DOE OSTI2025

Measurement of the muon magnetic anomaly to 0.20 ppm by the Muon g-2 experiment at Fermilab

The Muon $g-2$ experiment at Fermilab aims to measure the muon magnetic moment anomaly, $a_{\mu}=(g-2)/2$, with a final accuracy of 0.14 parts per million (ppm). The experiment’s first result was published in 2021, based on data collected in 2018, and in 2023 a new result was published based on two more years of data taking, 2019 and 2020. The combination of the two results from Fermilab and the previous one from Brookhaven National Laboratory brought the uncertainty on the experimental measurement of $a_{\mu}$ to the unprecedented value of 0.19 ppm. This paper will present details about the improvements of statistical and systematic uncertainties on $a_{\mu}$ since the 2021 result.

Cotrozzi, Lorenzo [Liverpool U.; INFN, Pisa]↗
DOE OSTI2017

The Calibration System of the E989 Experiment at Fermilab

The muon anomaly aµ is one of the most precise quantity known in physics experimentally and theoretically. The high level of accuracy permits to use the measurement of aµ as a test of the Standard Model comparing with the theoretical calculation. After the impressive result obtained at Brookhaven National Laboratory in 2001 with a total accuracy of 0.54 ppm, a new experiment E989 is under construction at Fermilab, motivated by the diff of aexp SM µ − aµ ∼ 3σ. The purpose of the E989 experiment is a fourfold reduction of the error, with a goal of 0.14 ppm, improving both the systematic and statistical uncertainty. With the use of the Fermilab beam complex a statistic of × 21 with respect to BNL will be reached in almost 2 years of data taking improving the statistical uncertainty to 0.1 ppm. Improvement on the systematic error involves the measurement technique of ωa and ωp, the anomalous precession frequency of the muon and the Larmor precession frequency of the proton respectively. The measurement of ωp involves the magnetic field measurement and improvements on this sector related to the uniformity of the field should reduce the systematic uncertainty with respect to BNL from 170 ppb to 70 ppb. A reduction from 180 ppb to 70 ppb is also required for the measurement of ωa; new DAQ, a faster electronics and new detectors and calibration system will be implemented with respect to E821 to reach this goal. In particular the laser calibration system will reduce the systematic error due to gain fl of the photodetectors from 0.12 to 0.02 ppm. The 0.02 ppm limit on systematic requires a system with a stability of 10−4 on short time scale (700 µs) while on longer time scale the stability is at the percent level. The 10−4 stability level required is almost an order of magnitude better than the existing laser calibration system in particle physics, making the calibration system a very challenging item. In addition to the high level of stability a particular environment, due to the presence of a 14 m diameter storage ring, a highly uniform magnetic field and the detector distribution around the storage ring, set specific guidelines and constraints. This thesis will focus on the final design of the Laser Calibration System developed for the E989 experiment. Chapter 1 introduces the subject of the anomalous magnetic moment of the muon; chapter 2 presents previous measurement of g-2, while chapter 3 discusses the Standard Model prediction and possible new physics scenario. Chapter 4 describes the E989 experiment. In this chapter will be described the experimental technique and also will be presented the experimental apparatus focusing on the improvements necessary to reduce the statistical and systematic errors. The main item of the thesis is discussed in the last two chapters: chapter 5 is focused on the Laser Calibration system while chapter 6 describes the Test Beam performed at the Beam Test Facility of Laboratori Nazionali di Frascati from the 29th February to the 7th March as a final test for the full calibrations system. An introduction explain the physics motivation of the system and the diff t devices implemented. In the final chapter the setup used will be described and some of the results obtained will be presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

The Beam Dynamics and Beam Related Uncertainties in Fermilab Muon $g-2$ Experiment

The anomaly of the muon magnetic moment, $a_{\mu}\equiv (g-2)/2$, has played an important role in constraining physics beyond the Standard Model for many years. Currently, the Standard Model prediction for $a_{\mu}$ is accurate to 0.42 parts per million (ppm). The most recent muon $g-2$ experiment was done at Brookhaven National Laboratory (BNL) and determined $a_{\mu}$ to 0.54 ppm, with a central value that differs from the Standard Model prediction by 3.3-3.6 standard deviations and provides a strong hint of new physics. The Fermilab Muon $g-2$ Experiment has a goal to measure $a_{\mu}$ to unprecedented precision: 0.14 ppm, which could provide an unambiguous answer to the question whether there are new particles and forces that exist in nature. To achieve this goal, several items have been identified to lower the systematic uncertainties. In this work, we focus on the beam dynamics and beam associated uncertainties, which are important and must be better understood. We will discuss the electrostatic quadrupole system, particularly the hardware-related quad plate alignment and the quad extension and readout system. We will review the beam dynamics in the muon storage ring, present discussions on the beam related systematic errors, simulate the 3D electric fields of the electrostatic quadrupoles and examine the beam resonances. We will use a fast rotation analysis to study the muon radial momentum distribution, which provides the key input for evaluating the electric field correction to the measured $a_{\mu}$.

Wu, Wanwei↗
DOE OSTI2018

Electric Field Effects on the Muon Anomalous Precession Frequency in the Fermilab Muon g -2 Experiment [Slides]

The muon anomalous magnetic moment ( g -2) has played an important role in constraining physics beyond the Standard Model for many years. The Fermilab Muon g -2 Experiment has a goal to measure it to unprecedented precision: 0.14 ppm. To achieve this goal, we need to understand the systematic uncertainties associated with beam dynamics. We will present a study of the electric field correction to the muon anomalous precession frequency based on fast rotation analysis, which uses the evolution of beam bunch structure to determine the muon momentum distribution.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Searching for Physics Beyond the Standard Model at the Intensity Frontier (Final Technical Report)

The goals of this project are the goals of the E989 experiment, the new muon g -2 experiment at Fermilab. This experiment will measure the anomalous magnetic moment of the muon with a precision of 0.14 parts-per-million, a factor of four improvement over the previous experimental measurement. The initial proposal envisioned significant contribution to the design, construction, and commissioning of the straw tube tracking system. Significant contributions were made to the design and commissioning, while the bulk of the construction was shifted to other collaborating institutions. Additional scope was undertaken, with the NIU group having primary responsibility for the assembly and commissioning of the experiment’s slow controls system.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Nanoscale magnetic Josephson junctions and superconductor/ferromagnet proximity effects for low-power spintronics

Competition between superconducting and ferromagnetic ordering at interfaces between ferromagnets (F) and superconductors (S) gives rise to several proximity effects such as odd-triplet superconductivity and spin-polarized supercurrents. A prominent example of an S/F proximity effect is the spin switch effect observed in S/F/N/F superconducting spin valve multilayers, in which the superconducting transition temperature T c is controlled by the angle Φ between the magnetic moments of the F layers separated by a nonmagnetic metallic spacer N. We carried out an experimental study of spin switch effect in Nb/Co/Cu/Co/CoO x nanowires measured as a function of bias current flowing in the plane of the layers. These measurements reveal an unexpected dependence of T c (Φ) on the bias current: T c (Φ) – T c (0) changes sign with increasing current bias. We attribute the origin of this bias dependence of the spin switch effect to a spin Hall current originating in Nb and flowing perpendicular to the plane of the multilayer, which suppresses T c of the multilayer. The bias dependence of spin switch effect can be important for hybrid F/S devices such as cryogenic memory for superconducting computers when device dimensions are scaled down to the nanometer length scale.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Topics in Proton Structure: BSM answers to its radius puzzle and latticesubtleties within its momentum distribution

This thesis covers two subjects, brie y outlined below, of hadronic physics. The proton radius puzzle and the muon anomalous magnetic moment discrepancy point to possible signs of lepton-universality violation. We introduce the context and background necessary to understand these two problems. And we analyze two suitable beyond-the-standard-model solutions, one vector-based and one scalar-based, which simultaneously solves both issues. Furthermore, we demonstrate that the parameter space of the respective solutions can be chosen so as to not be completely forbidden by considered experimental constraints. Specifically, we show that certain violations, analyzed by other authors in the context of similar solutions to those proposed, are ameliorated if one adds to the proposed solutions particular criteria required for renormalizability. We also explore the field of lattice perturbation theory in the context of deep inelastic scattering. In particular, we study the connection between lattice-based Euclidean parton distributions and their experiment-based Minkowskian equivalents. These parton distributions are extracted from deep inelastic scattering processes in which leptons are scattered of hadronic targets at energy levels high enough to resolve the internal hadronic structure. To synchronize experiment with theory, one must find the proper matching criteria to transform approximations of parton distributions, known as quasidistributions, as they are resolved on a computer (i.e. the lattice), back to the full parton distributions extracted from experiment. We provide the necessary background to understand context of the above and show the procedures necessary to match experiment with the lattice. We demonstrate how one must tread carefully to properly perform such a matching.

Freid, Michael↗
DOE OSTI2020

Numerical Study of a Passive Wedge Absorber System for Momentum Selection of Muon Beams

The Muon g-2 experiment aims to measure the anomalous magnetic moment of the muon with higher precision than previous experiments. In order to do this muons are created from protons hitting the target and are then sent to the M4 and M5 lines to be injected into the storage ring. The storage ring only accepts muons with momentum within 0.2% of 3094 MeV/c. In order to decrease the number of lost muons a wedge was placed in the M5 beam line to utilize the properties of ionization cooling to create a more uniform momentum spread. Previous simulations predicted a much larger gain of storable muons than the experimental results showed. In order to determine the cause of this discrepancy, simulations were run using a GEANT4 based code to track muons through the M4 and M5 lines, the inflector, and the storage ring while adjusting the orientation, material, geometrical parameters and studying the performance of this wedge for a wide range of incoming muon energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Beam-ion Studies in NSTX and NSTX-U (Final Technical Report)

The confinement of high energy "fast ions" is crucial for the success of magnetic fusion as a practical energy source. The research performed by UC Irvine on NSTX and NSTX-U provided new information about this important topic in the configuration known as a "spherical tokamak." Injected neutral beams provided the fast ions (also known as "beam ions"). There were five overarching goals of the research. One objective was to measure the confinement of beam ions in order to ascertain if they were accomplishing their desired purpose of transferring their energy to the bulk plasma. A second goal was to better understand instabilities that are driven unstable by the fast ions. A related goal was to use the similarities and differences between NSTX and the DIII-D conventional tokamak to better understand the fast-ion driven instabilities. A fourth goal was to develop new instruments to measure fast ions and techniques that facilitate analysis of the data. The fifth objective was to measure and understand acceleration of beam ions by RF waves. Much was accomplished in all of these five areas. In the first, it was shown that the large magnetic moment of the beam ions did not harm confinement but instabilities known as the "sawtooth" and "long-lived mode" do. In the second area, much attention was devoted to the fast-ion instabilities known as "Alfvén eigenmodes." In particular, Alfvén eigenmode "avalanches" can cause ~ 30% of the fast ions to be lost in a single explosive burst. The comparative studies with DIII-D showed that an instability discovered on NSTX is also important in conventional tokamaks. In the fourth category, several instruments were developed, a number of effects that complicate interpretation of the data were understood, and progress toward a new method to infer the fast-ion distribution function from the data was made. In the fifth category, the measured profile of accelerated fast ions was initially much broader than theoretical predictions but subsequent improvements in the theoretical modeling achieved good agreement with the data.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

QED with the electron as a very small black-hole-like object

We pursue a simple semi-classical particle-based picture of QED in which the electron is assumed to contain a point massless and chargeless core that interacts with the electromagnetic vacuum in ways that are not dissimilar to the manner in which small black holes may interact with photons. Modifications are made to obtain known properties of the electron including the presence of rest energy, Lamb shift, magnetic moments (both free and bound), charge, Larmor emission, and vacuum polarization. The present study does not provide proofs but is rather an attempt to reverse-engineer the photon-electron and black-hole-electron interaction properties needed to match experimental observations. The ease by which many QED observables can be reproduced suggests further study of the presented framework may be warranted. Future detailed analysis of the exchange of long wavelength Hawking radiation between a pair of small black holes will be of particular interest.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

A Massive, Position-Resolving, High-Energy-Resolution Detector for Non-Accelerator Cosmic and Intensity Frontier Particle Physics

We proposed to take the first steps in the development of a detector that promises energy resolution of tens of eV FWHM combined with robust nuclear-recoil discrimination and high fidelity, mm-precision position reconstruction for applications in non-accelerator particle physics at the Cosmic and Intensity Frontiers. The detector would obtain these excellent resolutions by sensing athermal phonons produced by particle interactions in crystalline, dielectric targets using a sensitive, highly multiplexable superconducting phonon sensor, the kinetic inductance detector (KID). This detector would be applicable to: the search for low-mass particle dark matter candidates with masses below 5~GeV via direct detection of scattering of dark matter particles with terrestrial nuclei; detection of coherent elastic neutrino-nucleus scattering to test for new physics such as a non-standard value of the weak nuclear charge, non-standard neutrino interactions (perhaps driven by a neutrino magnetic moment), or the existence of sterile neutrinos; and, searches for neutrinoless double-beta decay. During the funding period, we demonstrated scaling up of the detector concept from a 22-mm by 22-mm by 1-mm, 1-g prototype with 0.9~keV FWHM energy resolution to a 75-mm diameter by 1-mm, 9-g prototype while improving the inferred energy resolution to 0.7~keV~FWHM. In the process, we solved many problems associated with scaling device fabrication to large wafers and vastly reduced the fraction of the surface occupied by inactive but energy-absorbing metal. We also demonstrated a new technique that substantially simplifies the process of characterizing a new detector. These results provide a good foundation for future work scaling up the design to 4-mm thickness substrates and improving the resolution to reach 0.035~keV~FWHM, yielding a detector with compelling potential for the above applications.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Electron Drift Kinetics in Space and in the Lab [Slides]

In a magnetized plasma, dynamics are fundamentally split between the directions parallel and perpendicular to the magnetic field. Generally, gyration about the magnetic field will occur on smaller spatial and time scales than the bulk dynamics of the system. From Hamiltonian mechanics, a periodic motion on a time scale much shorter than the other system dynamics leads to an adiabatic invariant. The adiabatic invariant for this motion is the magnetic moment $\mu=\frac{mv⟂^2}{2B}$, which will be approximately conserved.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

A Grand Scan of the pMSSM Parameter Space for Snowmass 2021

We present a flexible framework for interpretation of SUSY sensitivity studies for future colliders in terms of the phenomenological minimal supersymmetric standard model (pMSSM). We perform a grand scan of the pMSSM 19-dimensional parameter space that covers the accessible ranges of many collider scenarios, including electron, muon, and hadron colliders at a variety of center of mass energies. This enables comparisons of sensitivity and complementarity across different future experiments, including both colliders and precision measurements in the Cosmological and Rare Frontiers. The details of the scan framework are discussed, and the impact of future precision measurements on Higgs couplings, the anomalous muon magnetic moment, and dark matter quantities is presented. The next steps for this ongoing effort include performing studies with simulated events in order to quantitatively assess the sensitivity of selected future colliders in the context of the pMSSM.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗