Muon Interactions Research Articles

Contributions of Cosmic-Ray Components to the HPGe Gamma Spectrometer Background Spectrum within the 0°-45° Zenith Angle Range

This study investigates the contributions of various cosmic-ray-induced components to the energy response of a High-Purity Germanium (HPGe) gamma spectrometer within the 0°-45° zenith angle range. The analysis focuses on muons, neutrons, protons, electrons, positrons, and photons. It also examines the impact of particle showers induced by muons interacting with the lead chamber and reaching the HPGe detector. Utilizing the GEANT4 simulation toolkit, we provide a detailed examination of these components' influence on the spectrum. The results confirm that within this zenith angle range, muons account for approximately 91% of the recorded cosmic-ray induced energy spectrum and contribute 54.6% to the overall cosmic-ray-induced background spectrum. The study also highlights the significant role of showers, especially those resulting from muon interactions with the lead shielding, in shaping the low-energy spectrum below 3 MeV.

Track signals at IceCube from subleading channels

Tracks events at the IceCube Observatory are characterized by an energetic muon crossing several kilometers before decaying. Such muons are dominantly produced in charged current (CC) muon neutrino-hadron interactions. However, muons are also produced through W-boson production and in the decay of tau leptons and heavy mesons created in neutral and charged current interactions induced by all neutrino flavors. In this paper, we investigate the contribution of these subleading channels to events characterized as tracks at the IceCube. Our results indicate that these channels correspond to a non-negligible fraction of the high-energy starting events track events. In addition, we show that its contributions are concentrated in muons that are less energetic than those arising from muonic neutrino CC interactions for the same visible energies of the process. Finally, we investigate the impact of these additional channels on the description of the astrophysical neutrino flux, and we find that the inclusion of these subleading processes are important in determining the parameters of the astrophysical neutrino flux. Published by the American Physical Society 2024

Probing Higgs-muon interactions at a multi-TeV muon collider

We study the capabilities of a muon collider, at 3 and 10 TeV center-of-mass energy, of probing the interactions of the Higgs boson with the muon. We consider all the possible processes involving the direct production of EW bosons (W, Z and H) with up to five particles in the final state. We study these processes both in the HEFT and SMEFT frameworks, assuming that the dominant BSM effects originate from the muon Yukawa sector. Our study shows that a Muon Collider has sensitivity beyond the high-luminosity LHC, especially as it does not rely on the Higgs-decay branching fraction to muons. A 10 TeV muon collider provides a unique sensitivity on muon and (multi-) Higgs interactions, significantly better than the 3 TeV option. Particularly, we find searches based purely on multi-Higgs production to be particularly effective in probing these couplings.

Inclusive cross section measurements in final states with and without protons for charged-current νμ -Ar scattering in MicroBooNE

A detailed understanding of inclusive muon neutrino charged-current interactions on argon is crucial to the study of neutrino oscillations in current and future experiments using liquid argon time projection chambers. To that end, we report a comprehensive set of differential cross section measurements for this channel that simultaneously probe the leptonic and hadronic systems by dividing the channel into final states with and without protons. Measurements of the proton kinematics and proton multiplicity of the final state are also presented. For these measurements, we utilize data collected with the MicroBooNE detector from 6.4×1020 protons on target from the Fermilab booster neutrino beam at a mean neutrino energy of approximately 0.8 GeV. We present in detail the cross section extraction procedure, including the unfolding, and model validation that uses data to model comparisons and the conditional constraint formalism to detect mismodeling that may introduce biases to extracted cross sections that are larger than their uncertainties. The validation exposes insufficiencies in the overall model, motivating the inclusion of an additional data-driven reweighting systematic to ensure the accuracy of the unfolding. The extracted results are compared to a number of event generators and their performance is discussed with a focus on the regions of phase space that indicate the greatest need for modeling improvements. Published by the American Physical Society 2024

First Simultaneous Measurement of Differential Muon-Neutrino Charged-Current Cross Sections on Argon for Final States with and without Protons Using MicroBooNE Data.

We report the first double-differential neutrino-argon cross section measurement made simultaneously for final states with and without protons for the inclusive muon neutrino charged-current interaction channel. The proton kinematics of this channel are further explored with a differential cross section measurement as a function of the leading proton's kinetic energy that extends across the detection threshold. These measurements use data collected with the MicroBooNE detector from 6.4×10^{20} protons on target from the Fermilab booster neutrino beam with a mean neutrino energy of ∼0.8 GeV. Extensive data-driven model validation utilizing the conditional constraint formalism is employed. This motivates enlarging the uncertainties with an empirical reweighting approach to minimize the possibility of extracting biased cross section results. The extracted nominal flux-averaged cross sections are compared to widely used event generator predictions revealing severe mismodeling of final states without protons for muon neutrino charged-current interactions, possibly from insufficient treatment of final state interactions. These measurements provide a wealth of new information useful for improving event generators which will enhance the sensitivity of precision measurements in neutrino experiments.

TomOpt: differential optimisation for task- and constraint-aware design of particle detectors in the context of muon tomography

We describe a software package, TomOpt, developed to optimise the geometrical layout and specifications of detectors designed for tomography by scattering of cosmic-ray muons. The software exploits differentiable programming for the modeling of muon interactions with detectors and scanned volumes, the inference of volume properties, and the optimisation cycle performing the loss minimisation. In doing so, we provide the first demonstration of end-to-end-differentiable and inference-aware optimisation of particle physics instruments. We study the performance of the software on a relevant benchmark scenario and discuss its potential applications. Our code is available on Github (Strong et al 2024 available at: https://github.com/GilesStrong/tomopt).

All-sky Search for Transient Astrophysical Neutrino Emission with 10 Years of IceCube Cascade Events

Neutrino flares in the sky are searched for in data collected by IceCube between 2011 and 2021 May. This data set contains cascade-like events originating from charged-current electron neutrino and tau neutrino interactions and all-flavor neutral-current interactions. IceCube’s previous all-sky searches for neutrino flares used data sets consisting of track-like events originating from charged-current muon neutrino interactions. The cascade data set is statistically independent of the track data sets, and while inferior in angular resolution, the low-background nature makes it competitive and complementary to previous searches. No statistically significant flare of neutrino emission was observed in an all-sky scan. Upper limits are calculated on neutrino flares of varying duration from 1 hr to 100 days. Furthermore, constraints on the contribution of these flares to the diffuse astrophysical neutrino flux are presented, showing that multiple unresolved transient sources may contribute to the diffuse astrophysical neutrino flux.

Interactions of Low-Energy Muons with Silicon: Numerical Simulation of Negative Muon Capture and Prospects for Soft Errors

In this paper, the interactions of low-energy muons (E < 10 MeV) with natural silicon, the basic material of microelectronics, are studied by Geant4 and SRIM simulation. The study is circumscribed to muons susceptible to slowdown/stop in the target and able to transfer sufficient energy to the semiconductor to create single events in silicon devices or related circuits. The capture of negative muons by silicon atoms is of particular interest, as the resulting nucleus evaporation and its effects can be catastrophic in terms of the emission of secondary ionizing particles ranging from protons to aluminum ions. We investigate in detail these different nuclear capture reactions in silicon and quantitatively evaluate their relative importance in terms of number of products, energy, linear energy transfer, and range distributions, as well as in terms of charge creation in silicon. Finally, consequences in the domain of soft errors in microelectronics are discussed.

Analysis of Secondary Particles Produced by 50-500 MeV Muon and Water Interaction using PHITS Monte Carlo Package

Secondary particles will always be generated in particle-to-matter interactions. The interaction of muons with matter produces various secondary particles. In this study, secondary particles produced by the interaction between muons with energies of 5, 50, 100, 200 and 500 MeV with water were analyzed using the PHITS Monte Carlo package. The muon source is placed on the surface of water that has a thickness of 1 km. The muography technique was applied by placed a detector at a depth of 1 km from the source. This detector records the secondary particles produced by the interaction. The results obtained show that this interaction produces secondary particles in the form of photons and neutrons in the detector. The number and energy of these photons and neutrons are strongly influenced by the initial energy of the muon. Muons with the lowest energy of 5 MeV produce more secondary particles than any other energy by a factor of 10. Low-energy muons travel slowly, allowing more interactions to occur and increasing the number of secondary particles in the detector. The energies of neutrons and photons in the detector are at most 3.76 MeV and 5.3 MeV, respectively.

First measurement of muon neutrino charged-current interactions on hydrocarbon without pions in the final state using multiple detectors with correlated energy spectra at T2K

First measurement of muon neutrino charged-current interactions on hydrocarbon without pions in the final state using multiple detectors with correlated energy spectra at T2K

Search for Extended Sources of Neutrino Emission in the Galactic Plane with IceCube

The Galactic plane, harboring a diffuse neutrino flux, is a particularly interesting target in which to study potential cosmic-ray acceleration sites. Recent gamma-ray observations by HAWC and LHAASO have presented evidence for multiple Galactic sources that exhibit a spatially extended morphology and have energy spectra continuing beyond 100 TeV. A fraction of such emission could be produced by interactions of accelerated hadronic cosmic rays, resulting in an excess of high-energy neutrinos clustered near these regions. Using 10 years of IceCube data comprising track-like events that originate from charged-current muon neutrino interactions, we perform a dedicated search for extended neutrino sources in the Galaxy. We find no evidence for time-integrated neutrino emission from the potential extended sources studied in the Galactic plane. The most significant location, at 2.6σ post-trials, is a 1.°7 sized region coincident with the unidentified TeV gamma-ray source 3HWC J1951+266. We provide strong constraints on hadronic emission from several regions in the galaxy.

Observation of Collider Muon Neutrinos with the SND@LHC Experiment.

We report the direct observation of muon neutrino interactions with the SND@LHC detector at the Large Hadron Collider. A dataset of proton-proton collisions at sqrt[s]=13.6 TeV collected by SND@LHC in 2022 is used, corresponding to an integrated luminosity of 36.8 fb^{-1}. The search is based on information from the active electronic components of the SND@LHC detector, which covers the pseudorapidity region of 7.2<η<8.4, inaccessible to the other experiments at the collider. Muon neutrino candidates are identified through their charged-current interaction topology, with a track propagating through the entire length of the muon detector. After selection cuts, 8 ν_{μ} interaction candidate events remain with an estimated background of 0.086 events, yielding a significance of about 7 standard deviations for the observed ν_{μ} signal.

First Direct Observation of Collider Neutrinos with FASER at the LHC.

We report the first direct observation of neutrino interactions at a particle collider experiment. Neutrino candidate events are identified in a 13.6TeV center-of-mass energy pp collision dataset of 35.4 fb^{-1} using the active electronic components of the FASER detector at the Large Hadron Collider. The candidates are required to have a track propagating through the entire length of the FASER detector and be consistent with a muon neutrino charged-current interaction. We infer 153_{-13}^{+12} neutrino interactions with a significance of 16 standard deviations above the background-only hypothesis. These events are consistent with the characteristics expected from neutrino interactions in terms of secondary particle production and spatial distribution, and they imply the observation of both neutrinos and anti-neutrinos with an incident neutrino energy of significantly above 200GeV.

High-resolution structural imaging of volcanoes using improved muon tracking

SUMMARY Muography is increasingly used to image the density distribution of volcanic edifices, complementing traditional geophysical tomographies. Here, we present a new muon data processing algorithm, and apply it to a new generation of scintillator-based muon detectors, to image the relative density distribution in La Soufrière de Guadeloupe volcano (Lesser Antilles, France). Our processing method iteratively searches for the best fit of each muon trajectory, accounting for all the hits registered by the detector related to the particular muon event. We test the performance of our algorithm numerically, simulating the interaction of muons with our detector and accounting for its exact assemblage including the scintillator bars and lead shielding. We find that our new data processing mitigates the impact of spurious signals coming from secondary particles, and improves the amount of successfully reconstructed events. The resulting 2-D muon images at La Soufrière have higher angular resolution than previous ones and capture the heterogeneous structure of the dome. They show density anomalies located on the summit southern region, which includes a boiling acid lake and degassing fractures, where the rock is the most porous and fumarolic activity is ongoing. This work shows the importance of combining numerical simulations of muon propagation with precise raw data processing to obtain high-quality results. It is also a first step towards fully assessing the noise contamination sources when performing muon tomography, and their correction, prior to geophysical interpretations.

Using ice core measurements from Taylor Glacier, Antarctica, to calibrate in situ cosmogenic 14C production rates by muons

Abstract. Cosmic rays entering the Earth's atmosphere produce showers of secondary particles such as protons, neutrons, and muons. The interaction of these particles with oxygen-16 (16O) in minerals such as ice and quartz can produce carbon-14 (14C). In glacial ice, 14C is also incorporated through trapping of 14C-containing atmospheric gases (14CO2, 14CO, and 14CH4). Understanding the production rates of in situ cosmogenic 14C is important to deconvolve the in situ cosmogenic and atmospheric 14C signals in ice, both of which contain valuable paleoenvironmental information. Unfortunately, the in situ 14C production rates by muons (which are the dominant production mechanism at depths of &gt;6 m solid ice equivalent) are uncertain. In this study, we use measurements of in situ 14C in ancient ice (&gt;50 ka) from the Taylor Glacier, an ablation site in Antarctica, in combination with a 2D ice flow model to better constrain the compound-specific rates of 14C production by muons and the partitioning of in situ 14C between CO2, CO, and CH4. Our measurements show that 33.7 % (±11.4 %; 95 % confidence interval) of the produced cosmogenic 14C forms 14CO and 66.1 % (±11.5 %; 95 % confidence interval) of the produced cosmogenic 14C forms 14CO2. 14CH4 represents a very small fraction (&lt;0.3 %) of the total. Assuming that the majority of in situ muogenic 14C in ice forms 14CO2, 14CO, and 14CH4, we also calculated muogenic 14C production rates that are lower by factors of 5.7 (3.6–13.9; 95 % confidence interval) and 3.7 (2.0–11.9; 95 % confidence interval) for negative muon capture and fast muon interactions, respectively, when compared to values determined in quartz from laboratory studies (Heisinger et al., 2002a, b) and in a natural setting (Lupker et al., 2015). This apparent discrepancy in muogenic 14C production rates in ice and quartz currently lacks a good explanation and requires further investigation.

Cosmic ray muon clustering for the MicroBooNE liquid argon time projection chamber using sMask-RCNN

In this article, we describe a modified implementation of Mask Region-based Convolutional Neural Networks (Mask-RCNN) for cosmic ray muon clustering in a liquid argon TPC and applied to MicroBooNE neutrino data. Our implementation of this network, called sMask-RCNN, uses sparse submanifold convolutions to increase processing speed on sparse datasets, and is compared to the original dense version in several metrics. The networks are trained to use wire readout images from the MicroBooNE liquid argon time projection chamber as input and produce individually labeled particle interactions within the image. These outputs are identified as either cosmic ray muon or electron neutrino interactions. We find that sMask-RCNN has an average pixel clustering efficiency of 85.9% compared to the dense network's average pixel clustering efficiency of 89.1%. We demonstrate the ability of sMask-RCNN used in conjunction with MicroBooNE's state-of-the-art Wire-Cell cosmic tagger to veto events containing only cosmic ray muons. The addition of sMask-RCNN to the Wire-Cell cosmic tagger removes 70% of the remaining cosmic ray muon background events at the same electron neutrino event signal efficiency. This event veto can provide 99.7% rejection of cosmic ray-only background events while maintaining an electron neutrino event-level signal efficiency of 80.1%. In addition to cosmic ray muon identification, sMask-RCNN could be used to extract features and identify different particle interaction types in other 3D-tracking detectors.

Recent Neutrino Cross-section Results from MicroBooNE

MicroBooNE is a liquid argon time projection chamber that operates in the Booster Neutrino Beam at Fermilab. The detector provides high-resolution imaging of neutrino interactions with a low threshold and full angular coverage. Thanks to a high event rate and several years of continuous operation, the MicroBooNE collaboration has obtained the world’s largest dataset of neutrino-argon scattering events. A detailed understanding of these interactions, especially the impact of nuclear physics effects, will be critical to the success of future precision neutrino oscillation efforts, particularly the argon-based Deep Underground Neutrino Experiment (DUNE) and the Short-Baseline Neutrino (SBN) program. This talk presents an overview of the latest neutrino-argon cross section measurements in MicroBooNE, including measurements of protons produced in muon neutrino interactions, measurements of the electron neutrino inclusive cross section, and progress towards measurements of rare channels.

The cosmic muon-induced background for the LEGEND-1000 alternative site at LNGS

The in-situ production of long-lived radio-isotopes by cosmic muon interactions may generate a non-negligible background for rare event searches in the deep subsurface. The delayed decay of 77(m)Ge has been identified as the dominant in-situ cosmogenic contributor for a neutrinoless double-beta decay search with 76Ge. The future ton-scale LEGEND-1000 experiment requires a total background of ≤ 10−5 cts/(keV-kg-yr). Dedicated Monte Carlo studies of the 77(m)Ge background at the alternative LNGS site were performed. The addition of passive neutron moderators, in combination with a delayed coincidence strategy, results in a background contribution of 8.6 × 10−7 cts/(keV.kg.yr) with an additional dead time of < 9%.

Closing the neutrino BSM gap: Physics potential of atmospheric through-going muons at DUNE

Many Beyond-Standard Model physics signatures are enhanced in high-energy neutrino interactions. To explore these signatures, ultra-large Cherenkov detectors such as IceCube exploit event samples with charged current muon neutrino interactions > 1 TeV. Most of these interactions occur below the detector volume, and produce muons that enter the detector. However, the large spacing between detectors leads to inefficiency for measuring muons with energies below or near the critical energy of 400 GeV. In response, IceCube has built a densely instrumented region within the larger detector. This provides large samples of well-reconstructed interactions that are contained within the densely instrumented region, extending up to energies of ~50 GeV. This leaves a gap of relatively unexplored atmospheric-neutrino events with energies between 50 GeV and 1 TeV in the ultra-large detectors. In this paper we point out that interesting Beyond Standard Model signatures may appear in this energy window, and that early running of the DUNE far detectors can give insight into new physics that may appear in this range.

The rise of muon content in extensive air showers after the 3 PeV knee of the primary cosmic ray spectrum according to data of the Tien Shan mountain installation

We put together the experimental results on muon component of extensive air showers (EAS) which were gained with various techniques at the detector complex of the Tien Shan mountain station. According to this comparison, the problem of the EAS muon content in the range of primary cosmic ray energies (1–100)PeV seems to be more complicated than it was usually supposed. Generally, from the models of nuclear interaction it follows that the EAS which have produced gamma-hadron families in the Tien Shan X-ray emulsion chamber did preferably originate from interaction of the light cosmic ray nuclei, such that their muon abundance must be ∼1.5 times below an average calculated over all showers. In contrary, the experimental muon counts in the EAS with families demonstrate a (1.5–2)-fold excess above the average, and this difference starts to be observable in the showers with the energy above the 3PeV knee of the primary cosmic ray spectrum. Later on, the rise of muon production in EAS after the knee was confirmed at Tien Shan by another experiment on detection of the neutrons stemmed from interaction of cosmic ray muons. Thus, the results obtained by the two completely different methods do mutually agree with each other but contradict to the common models of hadron interaction.