Muon Tracks Research Articles

A muon tracking algorithm for the Level 1 trigger in the CMS barrel muon chambers during HL-LHC

This contribution presents results on the Analytical Method (AM) algorithm for trigger primitive (TP) generation in the CMS Drift Tube (DT) chambers during the High Luminosity LHC operation (HL-LHC or LHC Phase II). The algorithm has been developed and validated both in software with an emulation approach, and through hardware implementation tests. The obtained performance on Phase II simulated data shows timing and position resolutions close to the ultimate performance of the DT chambers, with resilience to potential ageing situations. The firmware version has been implemented in the so-called AB7 (TwinMux), spare μTCA boards from the present DT system which host Xilinx Virtex 7 FPGAs, and included in a prototype chain of the HL-LHC electronics operated with real DT chambers during cosmic data taking. Agreement between the software emulation and the firmware implementation has been verified using different data samples, including a sample of real muons collected during 2016 data taking.

Muon trigger with fast Neural Networks on FPGA, a demonstrator

The online reconstruction of muon tracks in High Energy Physics experiments is a highly demanding task, typically performed on reconfigurable digital circuits, such as FPGAs. Complex analytical algorithms are executed in a quasi-real-time environment to identify, select, and reconstruct local tracks in often noise-rich environments. A novel approach to the generation of local triggers based on a hybrid combination of Artificial Neural Networks and analytical methods is proposed, targeting the muon reconstruction for drift tube detectors. The proposed algorithm exploits Neural Networks to solve otherwise computationally expensive analytical tasks for the unique identification of coherent signals and the removal of geometrical ambiguities. The proposed approach is deployed on state-of-the-art FPGA and its performances are evaluated on simulation and on data collected from cosmic rays.

Gaseous tracking detectors at the Sakurajima Muography Observatory

Muography is a novel imaging technology to reveal density structure of hill-sized objects. The cosmic muons predictably lose their energy and penetrate hundreds of meters into the ground, thus their differential local flux correlates with the crossed density-length. The Sakurajima Muography Observatory in Kagoshima, Japan, is the largest muography experiment targeting an active volcano. A set of multilayered gaseous detectors are used to reconstruct the muon tracks, thus by measuring the flux, imaging of the inner part of the volcano become possible. The paper focuses on the technical challenges of such a particle tracking system, the designed multi-wire proportional chambers, and the recent results from the measurements.

Mountain Muon Tomography Using a Liquid Scintillator Detector

Muon tomography (MT), based on atmospheric cosmic rays, is a promising technique suitable for nondestructive imaging of the internal structures of mountains. This method uses the measured flux distribution after attenuation, combined with the known muon angular and energy distributions and a 3D satellite map, to perform tomographic imaging of the density distribution inside a probed volume. A muon tomography station (MTS) requires direction-sensitive detectors with a high resolution for optimal tracking of incident cosmic-ray muons. The spherical liquid scintillator detector is one of the best candidates for this application due to its uniform detection efficiency for the whole 4π solid angle and its excellent ability to distinguish muon signals from the radioactive background via the difference in the energy deposit. This type of detector, with a 1.3 m diameter, was used in the Jinping Neutrino Experiment (JNE). Its angular resolution is 4.9 degrees. Following the application of imaging for structures of Jinping Mountain with JNE published results based on the detector, we apply it to geological prospecting. For mountains below 1 km in height and 2.8 g/cm3 in the reference rock, we demonstrate that this kind of detector can image internal regions with densities of ≤2.1 g/cm3 or ≥3.5 g/cm3 and hundreds of meters in size.

Momentum reconstruction of charged particles using multiple Coulomb scatterings in a nuclear emulsion detector

Abstract This paper describes a new method for momentum reconstruction of charged particles using multiple Coulomb scatterings in a nuclear emulsion detector with a layered structure of nuclear emulsion films and target materials. The method utilizes the scattering angles of particles precisely measured in the emulsion films. The method is based on the maximum likelihood to include the new information on the decrease of the energy as the particle travels through the detector. According to the Monte Carlo simulations, this method can measure momentum with a resolution of 10% for muons of ${500}\, {\rm MeV}/c$ passing through the detector perpendicularly. The momentum resolution is evaluated to be 10–20%, depending on the momentum and emission angle of the particle. By accounting for the effect of the energy decrease, the momentum can be reconstructed correctly with less bias, particularly in the low-momentum region. We apply this method to measure the momentum of muon tracks detected in the Neutrino Interaction research with Nuclear emulsion and J-PARC Accelerator (NINJA) experiment where the momentum is also measured independently by using the track range. The two measurements agree well within experimental uncertainties, verifying the method experimentally. This method will extend the measurable phase space of muons and hadrons in the NINJA experiment.

Borehole cylindrical detector: A compact muon telescope for muon radiography applications

Muon Radiography (or muography) is a recent imaging methodology that uses cosmic muons to investigate the interior of large objects, such as volcanoes, mines or buildings. Some applications are intended to use muography to search for hidden cavities in the subsoil. In many cases the muon telescope needs to be installed underground, inside tunnels, excavated chambers or drilled holes. Usually places available to install the muon detector are difficult to access for people; we thus constructed a very compact cylindrical muon tracker to deal with this problem. Thanks to its shape the detector can be inserted in boreholes. It is 1 m high and has a 24 cm diameter; these dimensions are ideal to fit a realizable drilled well. It is composed of bar and arc-shaped plastic scintillators. The original geometry of sensitive elements allows to maximize the acceptance, minimizing the dead spaces. The new borehole cylindrical detector has been tested in laboratory and the result of a measurement of open sky muon flux is in good agreement with expectations. A first application on field is currently ongoing to validate the capability of the telescope to reveal the presence of underground voids.

Advances in Cosmic Ray Muon Computed Tomography and Fieldable Spectroscopy

A recent example of successful technology transition from high energy physics to practical engineering applications is cosmic ray muon tomography. Cosmic ray muon tomography, is a promising non-destructive technique that has been recently utilized to monitor or image the contents of dense or well shielded objects, typically not feasible with conventional radiography techniques, e.g., x-ray or neutron. Cosmic ray muon tomography has been used with various levels of success in spent nuclear fuel monitoring, volcano imaging, and cargo container imaging. Further, knowledge of cosmic ray muon momentum spectrum has the potential to significantly improve and expand the use of a variety of recently developed muon-based radiographic techniques. However, existing muon tomography systems rely only on muon tracking and have no momentum measurement capabilities which reduces the image resolution and requires longer measurement times. A fieldable cosmic ray muon spectrometer with momentum measurement capabilities for use in muon tomography is currently missing. In this paper, we will discuss and explore recent advances in cosmic ray muon computed tomography and spectroscopy and their applications to engineering including a new concept for measuring muon momentum using multiple gaseous Cherenkov radiators. By varying the pressure of multiple gas Cherenkov radiators, a set of muon momentum threshold levels can be selected that are triggered only when the incoming muon momentum exceeds that level. As a result, depending on the incoming muon momentum, none to all Cherenkov radiators can be triggered. By analyzing the signals from each radiator, we can estimate the actual muon momentum.

Fast muon tracking with machine learning implemented in FPGA

In this work, we present a new approach for fast tracking on multiwire proportional chambers with neural networks. The tracking networks are developed and adapted for the first-level trigger at hadron collider experiments. We use Monte Carlo samples generated by Geant4 with a custom muon chamber, which resembles part of the thin gap chambers from the ATLAS experiment, for training and performance evaluations. The chamber has a total of seven gas gaps, where the first and last gas gaps are displaced by ∼1.5 m. Each gas gap has 50 channels with a size of 18–20 mm. Two neural network models are developed and presented: a convolutional neural network and a neural network optimized for the detector configuration of this study. In the latter network, a convolution layer is provided for each of three groups formed from 2–3 gas gaps of the chamber, and the outputs are fed into multilayer perceptrons in sequence. Both networks are transformed into hardware description language and implemented in Virtex UltraScale+ FPGA. The angular resolution is 2 mrad, which is comparable to the maximum resolution of the detector estimated by the minimum χ2 method. The latency achieved by the implemented firmware is less than 100 ns, and the throughput rate is 160 MHz.

Searching for High-energy Neutrino Emission from Galaxy Clusters with IceCube

Galaxy clusters have the potential to accelerate cosmic rays (CRs) to ultrahigh energies via accretion shocks or embedded CR acceleration sites. The CRs with energies below the Hillas condition will be confined within the cluster and eventually interact with the intracluster medium gas to produce secondary neutrinos and gamma rays. Using 9.5 yr of muon neutrino track events from the IceCube Neutrino Observatory, we report the results of a stacking analysis of 1094 galaxy clusters with masses ≳1014 M ⊙ and redshifts between 0.01 and ∼1 detected by the Planck mission via the Sunyaev–Zel’dovich effect. We find no evidence for significant neutrino emission and report upper limits on the cumulative unresolved neutrino flux from massive galaxy clusters after accounting for the completeness of the catalog up to a redshift of 2, assuming three different weighting scenarios for the stacking and three different power-law spectra. Weighting the sources according to mass and distance, we set upper limits at a 90% confidence level that constrain the flux of neutrinos from massive galaxy clusters (≳1014 M ⊙) to be no more than 4.6% of the diffuse IceCube observations at 100 TeV, assuming an unbroken E −2.5 power-law spectrum.

Three-dimensional density tomography determined from multi-directional muography of the Omuroyama scoria cone, Higashi–Izu monogenetic volcano field, Japan

Scoria cone is one of the basic forms of volcanoes, and clarifying its detailed internal structure and magma movement during its formation is important for understanding the nature of eruptions and also for volcanic disaster mitigation. We conducted a multi-directional muographic survey of the Omuroyama scoria cone, Japan, in order to determine the three-dimensional density structure of the scoria cone. We used a nuclear emulsion detector optimized for multi-directional muography that was installed at 11 sites around the volcano. Muon tracks recorded on emulsion films were read with a high-speed automated readout system. We obtained the three-dimensional density structure by applying a linear inversion to the muographic images, and evaluated the uncertainties. High-density zones were detected in scoria cone. Based on these observations and detailed topographic and geological constraints, we infer that high-density zones are the central, highly welded vent of the scoria cone, three-directional radial dikes extending from the central vent, respectively. We also infer that an E-W-trending dike fed a small lava flow, and that a SSE-NNW-trending dike caused a small flank eruption and produced a crater on the flank of the cone. Our results visualize the three-dimensional internal structure of volcanoes with novel resolution, and thereby demonstrate that the formation process of volcanoes can be discussed in detail. Since it has been difficult to directly detect such clear visualization of the internal structures and eruptive processes in the past, multi-directional muography has resulted in providing one hope for understanding volcanic activity.

High-precision large-area muon tracking and triggering with drift-tube chambers at future colliders

Experiments like the ATLAS detector at the HL-LHC or detectors at future hadron colliders need muon detectors with excellent momentum resolution at the percent level up to the TeV scale both at the trigger and the offline reconstruction level. This requires muon tracking chambers with high spatial resolution even at the highest background fluxes. Drift-tube chambers are the most cost effective technology for the instrumentation of large-area muon systems providing the required high rate capability and three-dimensional spatial resolution. Thanks to the advances in analog and digital electronics, modern drift-tube chambers can be used in stand-alone mode up to the highest background rates providing event times and second coordinates without the necessity of additional trigger chambers. New key developments in the integrated front-end electronics are fast baseline restoration of the shaped signal and picosecond time-to-digital converters for second coordinate measurement with double-sided read-out of the tubes. Self-triggered operation has become possible using modern high-performance FPGAs allowing for real-time pattern recognition and track reconstruction.

Status of the Jiangmen Underground Neutrino Observatory

The Jiangmen Underground Neutrino observatory (JUNO) experiment uses a large liquid scintillator detector to detect electron antineutrinos issued from nuclear reactors at a distance of 53 km. Its main goal is to determine the neutrino mass hierarchy and precisely measure some of the oscillation parameters. The detector will be located 700 m underground and will consist of 20 ktons of liquid scintillator contained in a 35 m diameter acrylic sphere, instrumented with 17612 (20-inch) and 25600 (3-inch) photomultiplier tubes (PMT), respectively. It will achieve an unprecedented 3% energy resolution (at 1 MeV). The objective is to detect 100000 events after 6 years of data taking. Two independent veto systems are foreseen to reduce the different backgrounds. A 40 kton ultrapure water Cherenkov pool instrumented with 2400 20-inch PMTs surrounds the central detector. It will tag events coming from outside the neutrino target. It will also act as a passive shielding for neutrons and gammas. In addition, a muon tracker will be installed on top of the detector (top muon veto) in order to tag cosmic muons and validate the muon track reconstruction.

MuGrid: A scintillator detector towards cosmic muon absorption imaging

Muography has a wide range of applications especially in the cross-disciplinary area. It is a powerful tool to probe the internal composition of objects in a non-destructive way. To achieve the goal of muography, it is essential to track muons as precisely as possible. We designed a cosmic muon tracking detector MuGrid using plastic scintillators. In this work, we present the preliminary progress of the MuGrid detector and its demonstrator, including the data acquisition system, characterization of plastic scintillators and Monte Carlo modeling of MuGrid. We also analyzed its detection efficiency, angular resolution, and provided a comparison of back-projection images of simulation and observation in an open environment. A case study is conducted in a tunnel as a validation of the whole system.

Background in the CMS drift tubes: measurements with LHC collision data and implications for detector longevity at HL-LHC

Drift Tubes (DT) are installed in the barrel region of the CMS muon spectrometer. They are used for offline tracking of muons and provide standalone trigger capabilities. Though an upgrade of the DT system electronics is foreseen for the High Luminosity LHC (HL-LHC), the present DT chambers will not be replaced, hence they will be called to operate enduring integrated doses far beyond what they were initially designed for. Together with accelerated aging studies, accurate measurements of the background-induced hit rates and currents observed over Run-2 are critical to assess the longevity of the DT chambers and to make projections of the expected performance of the system throughout HL-LHC. This report presents the state of the art of the studies on the background affecting the DT system, and connects them to results from longevity studies performed at the CERN high-intensity gamma irradiation facility (GIF++). Moreover, it describes all measures that have been put in place, by the end of Run-2 and over LS2, to mitigate aging and, where possible, reduce background level, with the aim of maximizing the performance of the DT muon detector throughout HL-LHC.

Muon tomography using cosmic-ray muons

The paper discusses about the R&D of a setup for muon tomography utilizing the scattering suffered by the muons due to electromagnetic interaction with the atomic nuclei while passing through any matter. The design of the setup has been optimized using numerical simulation for material discrimination and for further application in inspection of civil structures. An image processing algorithm based on pattern recognition method has been developed and tested for its performance in distinguishing between light and heavy elements and detecting defects in civil structures. The hardware developmental activities related to the muon tracking detectors and data acquisition system have been discussed.

A Novel RID Algorithm of Muon Trajectory Reconstruction in Water Cherenkov Detectors

Cosmic rays that strike the top of the Earth’s atmosphere generate a shower of secondary particles that move toward the surface with relativistic speeds. Water Cherenkov detectors (WCDs) on the ground can detect charged muons, which are one of the many particles generated in the shower, with the Cherenkov imaging technique. A large number of these muons travel in WCD tanks near the speed of light in a vacuum, faster than the speed of light in water, and so trigger isotropic Cherenkov radiation, which is detected by the photomultiplier tubes (PMTs) placed inside the tanks. When the radial component of the speed of the muon toward a PMT drops from superluminal to subluminal, the PMT records Cherenkov light from an optical phenomenon known as relativistic image doubling (RID), which causes two Cherenkov images of the same muon to appear suddenly, with both images moving in geometrically opposite directions on the original muon track. The quantities associated with the RID effect can be measured experimentally with a variety of detector types and can be used to find various points on the original trajectory of the muon. In this paper, a detailed study of reconstructing the trajectory of a muon entering a WCD using the RID technique has been presented. It is found that the measurements of standard RID observables enables a complete reconstruction of the trajectory of the muon to a high degree of accuracy with less than 1% error.

Construction and test of the SM1 type Micromegas chambers for the upgrade of the ATLAS forward muon spectrometer

Large-size Resistive Micromegas have been chosen for the upgrade of the forward muon spectrometer of the ATLAS experiment, the New Small Wheel project. These chambers, together with small-strip Thin Gap Chambers (sTGC), allow reconstruction of high-momentum muon tracks in a high-radiation environment and provide a robust low-threshold single-muon trigger. A collaboration of seven INFN units built 32 SM1 type chambers, corresponding to one fourth of the total number needed for this upgrade. Each SM1 chamber has a surface of approximately 2 m2 and four sensitive layers. The production was shared among five INFN construction sites and it was completed in fall 2020. The construction methods, as well as the results of the quality tests done on components of the detector and on the assembled chambers, are reported in the present paper.

Muon track reconstruction in a segmented bolometric array using multi-objective optimization

Recent advances in segmented solid-state detector arrays for rare-event searches have allowed the technology to approach the ton-scale in detector mass and the scale of meters in size. Often focused around searches for neutrinoless double-beta decay or direct dark matter detection, such experiments also have the capability to search for exotic particles that leave track-like signatures across their volume. However, the segmented nature of such detector arrays often sets the spatial resolution and makes the problem of reconstructing track-like paths non-trivial. In this paper, we present an algorithm that improves reconstruction of track-like events in segmented detectors using multi-objective optimization — a computational technique that optimizes more than one cost function at a time without specifying a quantitative weighting between them. Such a technique allows the reconstruction of tracks through a detector and the determination of path-lengths through individual elements. When combined with the reconstructed energy depositions in each element this allows for a calculation of the stopping power of track-like particles and opens the door to searches for particles with abnormal stopping power like monopoles or lightly-ionizing particles (LIPs). Results are presented which evaluate the precision of the reconstruction tools as they currently stand against Monte Carlo generated data. The algorithm is presented in the context of the CUORE experiment, but has applications to other segmented calorimeter detectors.

Development of compact muon spectrometer using multiple pressurized gas Cherenkov radiators

In both particle physics and muon applications, a high-resolution muon momentum measurement capability plays a significant role not only in providing valuable information on the properties of subatomic particles but also in improving the utilizability of cosmic ray muons. Typically, muon momentum is measured by reconstructing a curved muon path using a strong magnetic field and muon trackers. Alternatively, a time-of-flight and Cherenkov ring imager are less frequently applied, especially when there is a need to avoid a magnetic field. However, measurement resolution is much less than that of magnetic spectrometers, approximately 20% whereas it is nearly 4% or less when using magnets and trackers. Here, we propose a different paradigm to estimate muon momentum that utilizes multiple pressurized gas Cherenkov radiators. Using the fact that the refractive index of gas medium varies depending on its pressure and temperature, we can optimize the muon Cherenkov threshold momentum levels for which a muon signal will be detected. In this work, we demonstrate that muon momentum can be estimated with mean resolution of σp/p < 20% and mean classification rate of 90.08% in the momentum range of 0.1 to 10.0 GeV/c by analyzing optical photon signals from each Cherenkov radiator. We anticipate our new spectrometer will significantly improve quality of imaging and reduce scanning time in cosmic ray muon applications by being incorporated with existing instruments.

Observation of the temperature and barometric effects on the cosmic muon flux by the DANSS detector

The DANSS detector (Alekseev et al. in JINST 11:P11011, 2016) is located directly below a commercial reactor core at the Kalinin Nuclear Power Plant. Such a position provides an overburden about 50 m.w.e. in vertical direction. In terms of the cosmic rays it occupies an intermediate position between surface and underground detectors. The sensitive volume of the detector is a cubic meter of plastic scintillator with fine segmentation and combined PMT and SiPM readout, surrounded by multilayer passive and active shielding. The detector can reconstruct muon tracks passing through its sensitive volume. The main physics goal of the DANSS experiment implies the antineutrino spectra measurements at various distances from the source. This is achieved by means of a lifting platform so that the data is taken in three positions – 10.9, 11.9 and 12.9 meters from the reactor core. The muon data were collected for nearly four calendar years. The overburden parameters langle E_{thr}cos theta rangle and langle E_{thr} rangle , as well as the temperature and barometric correlation coefficients are evaluated separately for the three detector positions and, in each position, in three ranges of the zenith angle – for nearly vertical muons with cos theta >0.9, for nearly horizontal muons with cos theta <0.36, and for the whole upper hemisphere.