arXiv subjects

A. Grant

Publications and source records attributed to A. Grant.

17 recordsLinked to original sources

arXiv2025

Sensor operating point calibration and monitoring of the ALICE Inner Tracking System during LHC Run 3

The new Inner Tracking System (ITS2) of the ALICE experiment began operation in 2021 with the start of LHC Run 3. Compared to its predecessor, ITS2 offers substantial improvements in pointing resolution, tracking efficiency at low transverse momenta, and readout-rate capabilities. The detector employs silicon Monolithic Active Pixel Sensors (MAPS) featuring a pixel size of 26.88$\times$29.24 $\mu$m$^2$ and an intrinsic spatial resolution of approximately 5 $\mu$m. With a remarkably low material budget of 0.36% of radiation length ($X_{0}$) per layer in the three innermost layers and a total sensitive area of about 10 m$^2$, the ITS2 constitutes the largest-scale application of MAPS technology in a high-energy physics experiment and the first of its kind operated at the LHC. For stable data taking, it is crucial to calibrate different parameters of the detector, such as in-pixel charge thresholds and the masking of noisy pixels. The calibration of 24120 monolithic sensors, comprising a total of 12.6$\times$10$^{9}$ pixels, represents a major operational challenge. This paper presents the methods developed for the calibration of the ITS2 and outlines the strategies for monitoring and dynamically adjusting the detector's key performance parameters over time.

physics.ins-det↗

arXiv2023

Transverse Emittance Reduction in Muon Beams by Ionization Cooling

Accelerated muon beams have been considered for next-generation studies of high-energy lepton-antilepton collisions and neutrino oscillations. However, high-brightness muon beams have not yet been produced. The main challenge for muon acceleration and storage stems from the large phase-space volume occupied by the beam, derived from the muon production mechanism through the decay of pions from proton collisions. Ionization cooling is the technique proposed to decrease the muon beam phase-space volume. Here we demonstrate a clear signal of ionization cooling through the observation of transverse emittance reduction in beams that traverse lithium hydride or liquid hydrogen absorbers in the Muon Ionization Cooling Experiment (MICE). The measurement is well reproduced by the simulation of the experiment and the theoretical model. The results shown here represent a substantial advance towards the realization of muon-based facilities that could operate at the energy and intensity frontiers.

physics.acc-ph↗

arXiv2022

Multiple Coulomb Scattering of muons in Lithium Hydride

Multiple Coulomb Scattering (MCS) is a well known phenomenon occurring when charged particles traverse materials. Measurements of muons traversing low $Z$ materials made in the MuScat experiment showed that theoretical models and simulation codes, such as GEANT4 (v7.0), over-estimated the scattering. The Muon Ionization Cooling Experiment (MICE) measured the cooling of a muon beam traversing a liquid hydrogen or lithium hydride (LiH) energy absorber as part of a programme to develop muon accelerator facilities, such as a Neutrino Factory or a Muon Collider. The energy loss and MCS that occur in the absorber material are competing effects that alter the performance of the cooling channel. Therefore measurements of MCS are required in order to validate the simulations used to predict the cooling performance in future accelerator facilities. We report measurements made in the MICE apparatus of MCS using a LiH absorber and muons within the momentum range 160 to 245 MeV/c. The measured RMS scattering width is about 9% smaller than that predicted by the approximate formula proposed by the Particle Data Group. Data at 172, 200 and 240 MeV/c are compared to the GEANT4 (v9.6) default scattering model. These measurements show agreement with this more recent GEANT4 (v9.6) version over the range of incident muon momenta.

hep-ex↗

arXiv2021

First demonstration of in-beam performance of bent Monolithic Active Pixel Sensors

A novel approach for designing the next generation of vertex detectors foresees to employ wafer-scale sensors that can be bent to truly cylindrical geometries after thinning them to thicknesses of 20-40$μ$m. To solidify this concept, the feasibility of operating bent MAPS was demonstrated using 1.5$\times$3cm ALPIDE chips. Already with their thickness of 50$μ$m, they can be successfully bent to radii of about 2cm without any signs of mechanical or electrical damage. During a subsequent characterisation using a 5.4GeV electron beam, it was further confirmed that they preserve their full electrical functionality as well as particle detection performance. In this article, the bending procedure and the setup used for characterisation are detailed. Furthermore, the analysis of the beam test, including the measurement of the detection efficiency as a function of beam position and local inclination angle, is discussed. The results show that the sensors maintain their excellent performance after bending to radii of 2cm, with detection efficiencies above 99.9% at typical operating conditions, paving the way towards a new class of detectors with unprecedented low material budget and ideal geometrical properties.

physics.ins-det↗

arXiv2021

Performance of the MICE diagnostic system

Muon beams of low emittance provide the basis for the intense, well-characterised neutrino beams of a neutrino factory and for multi-TeV lepton-antilepton collisions at a muon collider. The international Muon Ionization Cooling Experiment (MICE) has demonstrated the principle of ionization cooling, the technique by which it is proposed to reduce the phase-space volume occupied by the muon beam at such facilities. This paper documents the performance of the detectors used in MICE to measure the muon-beam parameters, and the physical properties of the liquid hydrogen energy absorber during running.

physics.acc-ph↗

arXiv2019

First demonstration of ionization cooling by the Muon Ionization Cooling Experiment

High-brightness muon beams of energy comparable to those produced by state-of-the-art electron, proton and ion accelerators have yet to be realised. Such beams have the potential to carry the search for new phenomena in lepton-antilepton collisions to extremely high energy and also to provide uniquely well-characterised neutrino beams. A muon beam may be created through the decay of pions produced in the interaction of a proton beam with a target. To produce a high-brightness beam from such a source requires that the phase space volume occupied by the muons be reduced (cooled). Ionization cooling is the novel technique by which it is proposed to cool the beam. The Muon Ionization Cooling Experiment collaboration has constructed a section of an ionization cooling cell and used it to provide the first demonstration of ionization cooling. We present these ground-breaking measurements.

physics.acc-ph↗

arXiv2019

First particle-by-particle measurement of emittance in the Muon Ionization Cooling Experiment

The Muon Ionization Cooling Experiment (MICE) collaboration seeks to demonstrate the feasibility of ionization cooling, the technique by which it is proposed to cool the muon beam at a future neutrino factory or muon collider. The emittance is measured from an ensemble of muons assembled from those that pass through the experiment. A pure muon ensemble is selected using a particle-identification system that can reject efficiently both pions and electrons. The position and momentum of each muon are measured using a high-precision scintillating-fibre tracker in a 4\,T solenoidal magnetic field. This paper presents the techniques used to reconstruct the phase-space distributions and reports the first particle-by-particle measurement of the emittance of the MICE Muon Beam as a function of muon-beam momentum.

physics.acc-ph↗

arXiv2017

RF system for the MICE demonstration of ionization cooling

Muon accelerators offer an attractive option for a range of future particle physics experiments. They can enable high energy (TeV+) high energy lepton colliders whilst mitigating the difficulty of synchrotron losses, and can provide intense beams of neutrinos for fundamental physics experiments investigating the physics of flavor. The method of production of muon beams results in high beam emittance which must be reduced for efficient acceleration. Conventional emittance control schemes take too long, given the very short (2.2 microsecond) rest lifetime of the muon. Ionisation cooling offers a much faster approach to reducing particle emittance, and the international MICE collaboration aims to demonstrate this technique for the first time. This paper will present the MICE RF system and its role in the context of the overall experiment.

physics.acc-ph↗

arXiv2017

Design and expected performance of the MICE demonstration of ionization cooling

Muon beams of low emittance provide the basis for the intense, well-characterised neutrino beams necessary to elucidate the physics of flavour at a neutrino factory and to provide lepton-antilepton collisions at energies of up to several TeV at a muon collider. The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate ionization cooling, the technique by which it is proposed to reduce the phase-space volume occupied by the muon beam at such facilities. In an ionization-cooling channel, the muon beam passes through a material in which it loses energy. The energy lost is then replaced using RF cavities. The combined effect of energy loss and re-acceleration is to reduce the transverse emittance of the beam (transverse cooling). A major revision of the scope of the project was carried out over the summer of 2014. The revised experiment can deliver a demonstration of ionization cooling. The design of the cooling demonstration experiment will be described together with its predicted cooling performance.

physics.acc-ph↗

arXiv2016

Pion contamination in the MICE muon beam

The international Muon Ionization Cooling Experiment (MICE) will perform a systematic investigation of ionization cooling with muon beams of momentum between 140 and 240\,MeV/c at the Rutherford Appleton Laboratory ISIS facility. The measurement of ionization cooling in MICE relies on the selection of a pure sample of muons that traverse the experiment. To make this selection, the MICE Muon Beam is designed to deliver a beam of muons with less than $\sim$1\% contamination. To make the final muon selection, MICE employs a particle-identification (PID) system upstream and downstream of the cooling cell. The PID system includes time-of-flight hodoscopes, threshold-Cherenkov counters and calorimetry. The upper limit for the pion contamination measured in this paper is $f_π< 1.4\%$ at 90\% C.L., including systematic uncertainties. Therefore, the MICE Muon Beam is able to meet the stringent pion-contamination requirements of the study of ionization cooling.

physics.ins-det↗

arXiv2015

Electron-Muon Ranger: performance in the MICE Muon Beam

The Muon Ionization Cooling Experiment (MICE) will perform a detailed study of ionization cooling to evaluate the feasibility of the technique. To carry out this program, MICE requires an efficient particle-identification (PID) system to identify muons. The Electron-Muon Ranger (EMR) is a fully-active tracking-calorimeter that forms part of the PID system and tags muons that traverse the cooling channel without decaying. The detector is capable of identifying electrons with an efficiency of 98.6%, providing a purity for the MICE beam that exceeds 99.8%. The EMR also proved to be a powerful tool for the reconstruction of muon momenta in the range 100-280 MeV/$c$.

physics.ins-det↗

arXiv2013

Characterisation of the muon beams for the Muon Ionisation Cooling Experiment

A novel single-particle technique to measure emittance has been developed and used to characterise seventeen different muon beams for the Muon Ionisation Cooling Experiment (MICE). The muon beams, whose mean momenta vary from 171 to 281 MeV/c, have emittances of approximately 1.5--2.3 πmm-rad horizontally and 0.6--1.0 πmm-rad vertically, a horizontal dispersion of 90--190 mm and momentum spreads of about 25 MeV/c. There is reasonable agreement between the measured parameters of the beams and the results of simulations. The beams are found to meet the requirements of MICE.

physics.acc-ph↗

arXiv2013

The Electromagnetic Calorimeter for the T2K Near Detector ND280

The T2K experiment studies oscillations of an off-axis muon neutrino beam between the J-PARC accelerator complex and the Super-Kamiokande detector. Special emphasis is placed on measuring the mixing angle theta_13 by observing electron neutrino appearance via the sub-dominant muon neutrino to electron neutrino oscillation, and searching for CP violation in the lepton sector. The experiment includes a sophisticated, off-axis, near detector, the ND280, situated 280 m downstream of the neutrino production target in order to measure the properties of the neutrino beam and to understand better neutrino interactions at the energy scale below a few GeV. The data collected with the ND280 are used to study charged- and neutral-current neutrino interaction rates and kinematics prior to oscillation, in order to reduce uncertainties in the oscillation measurements by the far detector. A key element of the near detector is the ND280 electromagnetic calorimeter (ECal), consisting of active scintillator bars sandwiched between lead sheets and read outwith multi-pixel photon counters (MPPCs). The ECal is vital to the reconstruction of neutral particles, and the identification of charged particle species. The ECal surrounds the Pi-0 detector (P0D) and the tracking region of the ND280, and is enclosed in the former UA1/NOMAD dipole magnet. This paper describes the design, construction and assembly of the ECal, as well as the materials from which it is composed. The electronic and data acquisition (DAQ) systems are discussed, and performance of the ECal modules, as deduced from measurements with particle beams, cosmic rays, the calibration system, and T2K data, is described.

physics.ins-det↗

arXiv2011

Indication of Electron Neutrino Appearance from an Accelerator-produced Off-axis Muon Neutrino Beam

The T2K experiment observes indications of $ν_μ\rightarrow ν_e$ appearance in data accumulated with $1.43\times10^{20}$ protons on target. Six events pass all selection criteria at the far detector. In a three-flavor neutrino oscillation scenario with $|Δm_{23}^2|=2.4\times10^{-3}$ eV$^2$, $\sin^2 2θ_{23}=1$ and $\sin^2 2θ_{13}=0$, the expected number of such events is 1.5$\pm$0.3(syst.). Under this hypothesis, the probability to observe six or more candidate events is 7$\times10^{-3}$, equivalent to 2.5$σ$ significance. At 90% C.L., the data are consistent with 0.03(0.04)$<\sin^2 2θ_{13}<$ 0.28(0.34) for $δ_{\rm CP}=0$ and a normal (inverted) hierarchy.

hep-ex↗

arXiv2010

Large-angle production of charged pions with incident pion beams on nuclear targets

Measurements of the double-differential pi+/- production cross-section in the range of momentum 100 MeV/c <= p <= 800 MeV/c and angle 0.35 rad <= theta <= 2.15 rad using pi+/- beams incident on beryllium, aluminium, carbon, copper, tin, tantalum and lead targets are presented. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN Proton Synchrotron. The secondary pions were produced by beams in a momentum range from 3 GeV/c to 12.9 GeV/c hitting a solid target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using a small-radius cylindrical time projection chamber (TPC) placed inside a solenoidal magnet. Incident particles were identified by an elaborate system of beam detectors. Results are obtained for the double-differential cross-sections d2sigma/dpdtheta at six incident beam momenta. Data at 3 GeV/c, 5 GeV/c, 8 GeV/c, and 12 GeV/c are available for all targets while additional data at 8.9 GeV/c and 12.9 GeV/c were taken in positive particle beams on Be and Al targets, respectively. The measurements are compared with several generators of GEANT4 and the MARS Monte Carlo simulation.

hep-ex↗

arXiv2009

Comparison of large-angle production of charged pions with incident protons on cylindrical long and short targets

The HARP collaboration has presented measurements of the double-differential pi+/pi- production cross-section in the range of momentum 100 MeV/c <= p 800 MeV/c and angle 0.35 rad <= theta <= 2.15 rad with proton beams hitting thin nuclear targets. In many applications the extrapolation to long targets is necessary. In this paper the analysis of data taken with long (one interaction length) solid cylindrical targets made of carbon, tantalum and lead is presented. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN PS. The secondary pions were produced by beams of protons with momenta 5 GeV/c, 8 GeV/c and 12 GeV/c. The tracking and identification of the produced particles were performed using a small-radius cylindrical time projection chamber (TPC) placed inside a solenoidal magnet. Incident protons were identified by an elaborate system of beam detectors. Results are obtained for the double-differential yields per target nucleon d2 sigma / dp dtheta. The measurements are compared with predictions of the MARS and GEANT4 Monte Carlo simulations.

hep-ex↗

arXiv2008

Source Coding for a Simple Network with Receiver Side Information

We consider the problem of source coding with receiver side information for the simple network proposed by R. Gray and A. Wyner in 1974. In this network, a transmitter must reliably transport the output of two correlated information sources to two receivers using three noiseless channels: a public channel which connects the transmitter to both receivers, and two private channels which connect the transmitter directly to each receiver. We extend Gray and Wyner's original problem by permitting side information to be present at each receiver. We derive inner and outer bounds for the achievable rate region and, for three special cases, we show that the outer bound is tight.

cs.IT↗