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L. Xia

Publications and source records attributed to L. Xia.

At least 19 recordsLinked to original sources
arXiv2026

Characterization of UV optical components for photon detector calibration in liquid argon TPCs

Large liquid argon time projection chambers (LArTPCs) require stable and well-characterized delivery of ultraviolet (UV) light for in situ calibration of photosensors at cryogenic temperatures. This article reports bench-top and cryogenic measurements of the optical components used in a UV light calibration system, including multi-mode fused-silica fibers, SMA-to-SMA connectors, optical fiber feedthroughs, and light-diffuser assemblies. Light loss in several fiber types and SMA connectors was measured across wavelengths from \qtyrange{275}{970}{nm}. In addition, light-loss measurements of the tested fibers after several liquid-nitrogen thermal cycles showed no statistically significant degradation relative to baseline measurements, and high-rate pulsed exposure (30-90 million pulses from a \qty{275}{nm} LED) likewise showed no measurable aging in jacketed fibers. A compact, palm-sized, 3D-printed PEEK diffuser housing with stacked UV-grade fused-silica diffusers yields Lambertian emission and the most uniform angular distribution. Optical components exhibiting improved UV transmission were deployed successfully in multiple DUNE small- and large-scale prototypes, demonstrating reliable operation of UV light calibration systems. These findings inform component selection and calibration procedures for achieving reliable, uniform UV light delivery in large-scale cryogenic detectors such as DUNE.

physics.ins-det↗
arXiv2025

Blue-shifted dispersive waves and broadband UV emission using dual-core SiN waveguides

We show that using strongly coupled dual-core waveguides for supercontinuum generation shifts the wavelength of the high-frequency dispersive waves towards shorter wavelengths, as compared to generation in a single-core waveguide having the same core dimensions. In a demonstration experiment, we launch ultrashort infrared pump pulses at 1-$\mu$m wavelength (285-THz frequency) into silicon nitride waveguides, where soliton formation and fission leads to generation of dispersive waves in the visible range. Efficient input coupling and controlled excitation of the fundamental supermodes of the dual-core waveguide is provided with adiabatic tapers and a dual-prong input structure. For the dual-core waveguide, the short-wavelength dispersive wave is located at 540~nm (green, 555~THz), which is blue-shifted by 80~nm (70~THz) compared to that of the single-core waveguide. Simultaneously, the dual-core waveguide generates broadband radiation spanning from the blue into the UV range, reaching to below 350~nm (above 855~THz), with typically a spectral density 25~dB below that of the dispersive wave. The broadband component can be addressed to third harmonic generation and is not observed in single-core supercontinuum generation. Numerical modeling shows good agreement with experimental measurements. The demonstrated dual-core approach and dedicated input coupling appear to hold promise also for other waveguide structures, independent of specific materials or core dimensions, by providing shorter wavelengths than with the respective single-core waveguide.

physics.optics↗
arXiv2022

Mu2e-II: Muon to electron conversion with PIP-II

An observation of Charged Lepton Flavor Violation (CLFV) would be unambiguous evidence for physics beyond the Standard Model. The Mu2e and COMET experiments, under construction, are designed to push the sensitivity to CLFV in the mu to e conversion process to unprecedented levels. Whether conversion is observed or not, there is a strong case to be made for further improving sensitivity, or for examining the process on additional target materials. Mu2e-II is a proposed upgrade to Mu2e, with at least an additional order of magnitude in sensitivity to the conversion rate over Mu2e. The approach and challenges for this proposal are summarized. Mu2e-II may be regarded as the next logical step in a continued high-intensity muon program at FNAL.

hep-ex↗
arXiv2021

Proton Electromagnetic Form Factors in the Time-like Region through the Scan Technique

For over 100 years, scientists have investigated the properties of the proton, which is one of the most abundant components of visible matter in the universe. Nevertheless, researchers do not fully understand many details about its internal structure and dynamics. Time-like electromagnetic form factors are one of the observable quantities that can help us achieve a deeper understanding. In this review article, we present an overview of the current experimental status in this field, consisting of measurements of the time-like reactions $e^{+}e^{-}\to p\bar{p}$, $p\bar{p}\to e^{+}e^{-}$, and future measurements of $p\bar{p}\to μ^{+}μ^{-}$. A focus is put on recent high precision results of the reaction $e^{+}e^{-}\to p\bar{p}$ that have been obtained after analyzing 688.5~pb$^{-1}$ of data taken at the BESIII experiment. They are compared and put into perspective to results from previous measurements in this channel. We discuss the channels $p\bar{p}\to e^{+}e^{-}$ and $p\bar{p}\toμ^{+}μ^{-}$ in terms of the few existing as well as future measurements, which the PANDA experiment will perform. Finally, we review several new theoretical models and phenomenological approaches inspired by the BESIII high precision results and then discuss their implications for a deeper understanding of the proton's structure and inner dynamics.

hep-ex↗
arXiv2021

On a Single Server Queue Fed by a Scheduled Traffic with Pareto Perturbations

A "scheduled" arrival process is one in which the n th arrival is scheduled for time n, but instead occurs at a different time. The difference between the scheduled time and the arrival time is called the perturbation. The sequence of perturbations is assumed to be iid. We describe here the behavior of a single server queue fed by such traffic in which the processing times are deterministic. A particular focus is on perturbation with Pareto-like tails but with finite mean. We obtain tail approximations for the steady-state workload in both cases where the queue is critically loaded and under a heavy-traffic regime. A key to our approach is our analysis of the tail behavior of a sum of independent Bernoulli random variables with success probability following a power law with parameter strictly larger than 1.

math.PR↗
arXiv2019

Analysis of Testbeam Data of the Highly Granular RPC-Steel CALICE Digital Hadron Calorimeter and Validation of Geant4 Monte Carlo Models

We present a study of the response of the highly granular Digital Hadronic Calorimeter with steel absorbers, the Fe-DHCAL, to positrons, muons, and pions with momenta ranging from 2 to 60 GeV/c. Developed in the context of the CALICE collaboration, this hadron calorimeter utilises Resistive Plate Chambers as active media, interspersed with steel absorber plates. With a transverse granularity of $1\,\times\,1\,$cm$^{2}$ and a longitudinal segmentation of 38 layers, the calorimeter counted 350,208 readout channels, each read out with single-bit resolution (digital readout). The data were recorded in the Fermilab test beam in 2010-11. The analysis includes measurements of the calorimeter response and the energy resolution to positrons and muons, as well as detailed studies of various shower shape quantities. The results are compared to simulations based on Geant4, which utilise different electromagnetic and hadronic physics lists.

physics.ins-det↗
arXiv2018

Hadronic Energy Resolution of a Combined High Granularity Scintillator Calorimeter System

This paper presents results obtained with the combined CALICE Scintillator Electromagnetic Calorimeter, Analogue Hadronic Calorimeter and Tail Catcher & Muon Tracker, three high granularity scintillator-SiPM calorimeter prototypes. The response of the system to pions with momenta between 4 GeV/c and 32 GeV/c is analysed, including the energy response, resolution, and longitudinal shower profiles. The results of a software compensation technique based on weighting according to hit energy are compared to those of a standard linear energy reconstruction. The results are compared to predictions of the GEANT4 physics lists QGSP_BERT_HP and FTFP_BERT_HP.

physics.ins-det↗
arXiv2018

Construction and Response of a Highly Granular Scintillator-based Electromagnetic Calorimeter

A highly granular electromagnetic calorimeter with scintillator strip readout is being developed for future lepton collider experiments. A prototype of 21.5 $X_0$ depth and $180 \times 180 $mm$^2$ transverse dimensions was constructed, consisting of 2160 individually read out $10 \times 45 \times 3$ mm$^3$ scintillator strips. This prototype was tested using electrons of 2--32 GeV at the Fermilab Test Beam Facility in 2009. Deviations from linear energy response were less than 1.1\%, and the intrinsic energy resolution was determined to be $(12.5 \pm 0.1 (\mathrm{stat.}) \pm0.4 (\mathrm{syst.}))\%/\sqrt{E[\mathrm{GeV}]}\oplus (1.2 \pm 0.1(\mathrm{stat.})^{+0.6}_{-0.7}(\mathrm{syst.}))\%$, where the uncertainties correspond to statistical and systematic sources, respectively.

physics.ins-det↗
arXiv2016

Design, Construction and Testing of the Digital Hadron Calorimeter (DHCAL) Electronics

A novel hadron calorimeter is being developed for future lepton colliding beam detectors. The calorimeter is optimized for the application of Particle Flow Algorithms (PFAs) to the measurement of hadronic jets and features a very finely segmented readout with 1 x 1 cm2 cells. The active media of the calorimeter are Resistive Plate Chambers (RPCs) with a digital, i.e. one-bit, readout. To first order the energy of incident particles in this calorimeter is reconstructed as being proportional to the number of pads with a signal over a given threshold. A large-scale prototype calorimeter with approximately 500,000 readout channels has been built and underwent extensive testing in the Fermilab and CERN test beams. This paper reports on the design, construction, and commissioning of the electronic readout system of this prototype calorimeter. The system is based on the DCAL front-end chip and a VME-based back-end.

physics.ins-det↗
arXiv2016

DHCAL with Minimal Absorber: Measurements with Positrons

In special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. The thickness of each layer corresponded approximately to 0.29 radiation lengths or 0.034 nuclear interaction lengths, defined mostly by the copper and steel skins of the detector cassettes. This paper reports on measurements performed with this device in the Fermilab test beam with positrons in the energy range of 1 to 10 GeV. The measurements are compared to simulations based on GEANT4 and a standalone program to emulate the detailed response of the active elements.

physics.ins-det↗
arXiv2016

Design, Construction and Commissioning of the Digital Hadron Calorimeter - DHCAL

A novel hadron calorimeter is being developed for future lepton colliding beam detectors. The calorimeter is optimized for the application of Particle Flow Algorithms (PFAs) to the measurement of hadronic jets and features a very finely segmented readout with 1 x 1 cm2 cells. The active media of the calorimeter are Resistive Plate Chambers (RPCs) with a digital, i.e. one-bit, readout. To first order the energy of incident particles in this calorimeter is reconstructed as being proportional to the number of pads with a signal over a given threshold. A large-scale prototype calorimeter with approximately 500,000 readout channels has been built and underwent extensive testing in the Fermilab and CERN test beams. This paper reports on the design, construction, and commissioning of this prototype calorimeter.

physics.ins-det↗
arXiv2015

Shower development of particles with momenta from 15 GeV to 150 GeV in the CALICE scintillator-tungsten hadronic calorimeter

We present a study of showers initiated by electrons, pions, kaons, and protons with momenta from 15 GeV to 150 GeV in the highly granular CALICE scintillator-tungsten analogue hadronic calorimeter. The data were recorded at the CERN Super Proton Synchrotron in 2011. The analysis includes measurements of the calorimeter response to each particle type as well as measurements of the energy resolution and studies of the longitudinal and radial shower development for selected particles. The results are compared to Geant4 simulations (version 9.6.p02). In the study of the energy resolution we include previously published data with beam momenta from 1 GeV to 10 GeV recorded at the CERN Proton Synchrotron in 2010.

physics.ins-det↗
arXiv2015

Measurements of the Rate Capability of Various Resistive Plate Chambers

Resistive Plate Chambers (RPCs) exhibit a significant loss of efficiency for the detection of particles, when subjected to high particle fluxes. This rate limitation is related to the usually high resistivity of the resistive plates used in their construction. This paper reports on measurements of the performance of three different glass RPC designs featuring a different total resistance of the resistive plates. The measurements were performed with 120 GeV protons at varying beam intensities

physics.ins-det↗
arXiv2015

Testing Hadronic Interaction Models using a Highly Granular Silicon-Tungsten Calorimeter

A detailed study of hadronic interactions is presented using data recorded with the highly granular CALICE silicon-tungsten electromagnetic calorimeter. Approximately 350,000 selected negatively charged pion events at energies between 2 and 10 GeV have been studied. The predictions of several physics models available within the Geant4 simulation tool kit are compared to this data. A reasonable overall description of the data is observed; the Monte Carlo predictions are within 20% of the data, and for many observables much closer. The largest quantitative discrepancies are found in the longitudinal and transverse distributions of reconstructed energy.

physics.ins-det↗
arXiv2015

Letter of Intent: The Accelerator Neutrino Neutron Interaction Experiment (ANNIE)

Neutron tagging in Gadolinium-doped water may play a significant role in reducing backgrounds from atmospheric neutrinos in next generation proton-decay searches using megaton-scale Water Cherenkov detectors. Similar techniques might also be useful in the detection of supernova neutrinos. Accurate determination of neutron tagging efficiencies will require a detailed understanding of the number of neutrons produced by neutrino interactions in water as a function of momentum transferred. We propose the Atmospheric Neutrino Neutron Interaction Experiment (ANNIE), designed to measure the neutron yield of atmospheric neutrino interactions in gadolinium-doped water. An innovative aspect of the ANNIE design is the use of precision timing to localize interaction vertices in the small fiducial volume of the detector. We propose to achieve this by using early production of LAPPDs (Large Area Picosecond Photodetectors). This experiment will be a first application of these devices demonstrating their feasibility for Water Cherenkov neutrino detectors.

physics.ins-det↗
arXiv2015

Pion and proton showers in the CALICE scintillator-steel analogue hadron calorimeter

Showers produced by positive hadrons in the highly granular CALICE scintillator-steel analogue hadron calorimeter were studied. The experimental data were collected at CERN and FNAL for single particles with initial momenta from 10 to 80 GeV/c. The calorimeter response and resolution and spatial characteristics of shower development for proton- and pion-induced showers for test beam data and simulations using Geant4 version 9.6 are compared.

physics.ins-det↗
arXiv2015

Tests of a Novel Design of Resistive Plate Chambers

A novel design of Resistive Plate Chambers (RPCs), using only a single resistive plate, is being proposed. Based on this design, two large size prototype chambers were constructed and were tested with cosmic rays and in particle beams. The tests confirmed the viability of this new approach. In addition to showing an improved single-particle response compared to the traditional 2-plate design, the novel chambers also prove to be suitable for calorimetric applications.

physics.ins-det↗