arXiv subjects

Bryan McKinnon

Publications and source records attributed to Bryan McKinnon.

13 recordsLinked to original sources

arXiv2026

Long Range Outlook for Short-Range Correlations

Short range correlated (SRC) N N pairs are pairs of nucleons with high relative momentum (prel > kF where kF ~ 250 MeV/c is the Fermi momentum in medium to heavy nuclei) and lower center of mass momentum. The motivation for studying SRC pairs ranges from a desire to achieve a more comprehensive understanding of the many-body nuclear wave-function at high-resolution to searching for explicit QCD-dynamics effects within the nuclear medium, not to mention connections to many other open problems in nuclear physics. Exploring short-range correlations was one of the physics motivations for building CEBAF (now Jefferson Lab). Scientists used the high luminosity and high energy of this cutting-edge machine to find kinematics that cleanly showed the signals of short-range correlations. This paved the way in the last two decades for tremendous progress understanding these correlations. This paper reviews recent progress and highlights outstanding questions and areas that need further study.

nucl-ex↗

arXiv2025

Universal parameters of the $\Lambda(1380)$, the $\Lambda(1405)$ and their isospin partners from a combined analysis of Lattice QCD and experimental results

We perform a global analysis of lattice and experimental data on negative-strangeness meson-baryon scattering using a large set of variations of the theoretical framework based on the Chiral Unitary Approach. For the former, the L\"uscher formalism is utilized taking into account all pertinent coupled-channel effects. Through this, systematic uncertainties related to data scarcity, potential ambiguities, and possible framework dependence are quantified for the first time. The implementation of information criteria and other statistical tools is discussed. As a final result we provide pole positions for isoscalar resonances at the physical and lattice points including statistical and systematic uncertainties. Predictions for the isovector states are also provided showing large uncertainties.

hep-ph↗

arXiv2024

Letter of Intent: Open Charm at JLab with the sPHENIX MAPS tracker

We propose a physics program at JLab with CLAS12 focusing on open-charm measurements, aiming to complement and expand current studies of $J/ψ$ at (sub) threshold. This program will aid us in elucidating the $J/ψ$ production mechanisms, which is crucial for interpreting data in terms of gluon form factors and offer potential insights into the intrinsic charm hypothesis and cold-nuclear matter effects. We discuss the technical feasibility of integrating the sPHENIX monolithic-active-pixel sensor (MAPS) tracker, known as MVTX, with the CLAS12 detector. The sPHENIX MTVX would support an open-charm program by providing excellent secondary-vertex performance for tagging $D$ mesons. We study the kinematics of $γp \to \bar{D}^{0}Λ_{c}$ through phase-space simulations and estimate rates for the tagged quasi-photoproduction regime available with the CLAS12 forward tagger. While open-charm cross-sections at threshold remain uncertain, various predictions suggest that these measurements could be feasible when combined with conservative estimates of detector acceptance and luminosity. These preliminary estimates motivate detailed Geant detector simulations of signals and backgrounds, along with thorough technical assessments of operating conditions, to further explore the feasibility of these measurements in future dedicated CLAS12 experiments at JLab.

nucl-ex↗

arXiv2023

Deep Learning Level-3 Electron Trigger for CLAS12

Fast, efficient and accurate triggers are a critical requirement for modern high-energy physics experiments given the increasingly large quantities of data that they produce. The CEBAF Large Acceptance Spectrometer (CLAS12) employs a highly efficient electron trigger to filter the amount of recorded data by requiring at least one electron in each event, at the cost of a low purity in electron identification. Machine learning algorithms are increasingly employed for classification tasks such as particle identification due to their high accuracy and fast processing times. In this article, we show how a convolutional neural network could be deployed as a Level 3 electron trigger at CLAS12. We demonstrate that the AI trigger would achieve a significant data reduction compared to the traditional trigger, whilst preserving a 99.5\% electron identification efficiency. The AI trigger purity as a function of increased luminosity is improved relative to the traditional trigger. As a consequence, this AI trigger can achieve a data recording reduction improvement of 0.33\% per nA when compared to the traditional trigger whilst maintaining an efficiency above 99.5\%. A reduction in data output also reduces storage costs and post-processing times, which in turn reduces the time to the publication of new physics measurements.

physics.ins-det↗

arXiv2022

The Heavy Photon Search Experiment

The Heavy Photon Search (HPS) experiment is designed to search for a new vector boson $A^\prime$ in the mass range of 20 MeV/$c^2$ to 220 MeV/$c^2$ that kinetically mixes with the Standard Model photon with couplings $ε^2 >10^{-10}$. In addition to the general importance of exploring light, weakly coupled physics that is difficult to probe with high-energy colliders, a prime motivation for this search is the possibility that sub-GeV thermal relics constitute dark matter, a scenario that requires a new comparably light mediator, where models with a hidden $U(1)$ gauge symmetry, a "dark", "hidden sector", or "heavy" photon, are particularly attractive. HPS searches for visible signatures of these heavy photons, taking advantage of their small coupling to electric charge to produce them via a process analogous to bremsstrahlung in a fixed target and detect their subsequent decay to $\mathrm{e}^+ \mathrm{e}^-$ pairs in a compact spectrometer. In addition to searching for $\mathrm{e}^+ \mathrm{e}^-$ resonances atop large QED backgrounds, HPS has the ability to precisely measure decay lengths, resulting in unique sensitivity to dark photons, as well as other long-lived new physics. After completion of the experiment and operation of engineering runs in 2015 and 2016 at the JLab CEBAF, physics runs in 2019 and 2021 have provided datasets that are now being analyzed to search for dark photons and other new phenomena.

hep-ex↗

arXiv2021

Strange Hadron Spectroscopy with Secondary KL Beam in Hall D

We propose to create a secondary beam of neutral kaons in Hall D at Jefferson Lab to be used with the GlueX experimental setup for strange hadron spectroscopy. The superior CEBAF electron beam will enable a flux on the order of $1\times 10^4~K_L/sec$, which exceeds the flux of that previously attained at SLAC by three orders of magnitude. The use of a deuteron target will provide first measurements ever with neutral kaons on neutrons. The experiment will measure both differential cross sections and self-analyzed polarizations of the produced $Λ$, $Σ$, $Ξ$, and $Ω$ hyperons using the GlueX detector at the Jefferson Lab Hall D. The measurements will span CM $\cosθ$ from $-0.95$ to 0.95 in the range W = 1490 MeV to 2500 MeV. The new data will significantly constrain the partial wave analyses and reduce model-dependent uncertainties in the extraction of the properties and pole positions of the strange hyperon resonances, and establish the orbitally excited multiplets in the spectra of the $Ξ$ and $Ω$ hyperons. Comparison with the corresponding multiplets in the spectra of the charm and bottom hyperons will provide insight into he accuracy of QCD-based calculations over a large range of masses. The proposed facility will have a defining impact in the strange meson sector through measurements of the final state $Kπ$ system up to 2 GeV invariant mass. This will allow the determination of pole positions and widths of all relevant $K^\ast(Kπ)$ $S$-,$P$-,$D$-,$F$-, and $G$-wave resonances, settle the question of the existence or nonexistence of scalar meson $κ/K_0^\ast(700)$ and improve the constrains on their pole parameters. Subsequently improving our knowledge of the low-lying scalar nonet in general.

nucl-ex↗

arXiv2020

Precision measurements of A=3 nuclei in Hall B

We propose a high-statistics measurement of few body nuclear structure and short range correlations in quasi-elastic scattering at 6.6 GeV from $^2$H, $^3$He and $^3$H targets in Hall B with the CLAS12 detector. We will measure absolute cross sections for $(e,e'p)$ and $(e,e'pN)$ quasi-elastic reaction channels up to a missing momentum $p_{miss} \approx 1$ GeV/c over a wide range of $Q^2$ and $x_B$ and construct the isoscalar sum of $^3$H and $^3$He. We will compare $(e,e'p)$ cross sections to nuclear theory predictions using a wide variety of techniques and $NN$ interactions in order to constrain the $NN$ interaction at short distances. We will measure $(e,e'pN)$ quasi-elastic reaction cross sections and $(e,e'pN)/(e,e'p)$ ratios to understand short range correlated (SRC) $NN$ pairs in the simplest non-trivial system. $^3$H and $^3$He, being mirror nuclei, exploit the maximum available isospin asymmetry. They are light enough that their ground states are readily calculable, but they already exhibit complex nuclear behavior, including $NN$ SRCs. We will also measure $^2$H$(e,e'p)$ in order to help theorists constrain non-quasielastic reaction mechanisms in order to better calculate reactions on $A=3$ nuclei. Measuring all three few body nuclei together is critical, in order to understand and minimize different reaction effects, such as single charge exchange final state interactions, in order to test ground-state nuclear models. We will also measure the ratio of inclusive $(e,e')$ quasi-elastic cross sections (integrated over $x_B$) from $^3$He and $^3$H in order to extract the neutron magnetic form factor $G_M^n$ at small and moderate values of $Q^2$. We will measure this at both 6.6 GeV and 2.2 GeV.

nucl-ex↗

arXiv2017

Spectator-Tagged Deeply Virtual Compton Scattering on Light Nuclei

The three-dimensional picture of quarks and gluons in the proton is set to be revealed through Deeply virtual Compton scattering while a critically important puzzle in the one-dimensional picture remains, namely, the origins of the EMC effect. Incoherent nuclear DVCS, i.e. DVCS on a nucleon inside a nucleus, can reveal the 3D partonic structure of the bound nucleon and shed a new light on the EMC effect. However, the Fermi motion of the struck nucleon, off-shell effects and final-state interactions (FSIs) complicate this parton level interpretation. We propose here a measurement of incoherent DVCS with a tagging of the recoiling spectator system (nucleus A-1) to systematically control nuclear effects. Through spectator-tagged DVCS, a fully detected final state presents a unique opportunity to systematically study these nuclear effects and cleanly observe possible modification of the nucleon's quark distributions. We propose to measure the DVCS beam-spin asymmetries (BSAs) on $^4$He and deuterium targets. The reaction $^4$He$(e,e^{\prime}γ\,p\,^3$H$)$ with a fully detected final state has the rare ability to simultaneously quantify FSIs, measure initial nucleon momentum, and provide a sensitive probe to other nuclear effects at the parton level. The DVCS BSA on a (quasi-free) neutron will be measured by tagging a spectator proton with a deuteron target. Similarly, a bound neutron measurement detects a spectator $^3$He off a $^4$He target. These two observables will allow for a self-contained measurement of the neutron off-forward EMC Effect.

nucl-ex↗

arXiv2016

The HPS electromagnetic calorimeter

The Heavy Photon Search experiment (HPS) is searching for a new gauge boson, the so-called "heavy photon." Through its kinetic mixing with the Standard Model photon, this particle could decay into an electron-positron pair. It would then be detectable as a narrow peak in the invariant mass spectrum of such pairs, or, depending on its lifetime, by a decay downstream of the production target. The HPS experiment is installed in Hall-B of Jefferson Lab. This article presents the design and performance of one of the two detectors of the experiment, the electromagnetic calorimeter, during the runs performed in 2015-2016. The calorimeter's main purpose is to provide a fast trigger and reduce the copious background from electromagnetic processes through matching with a tracking detector. The detector is a homogeneous calorimeter, made of 442 lead-tungstate (PbWO4) scintillating crystals, each read out by an avalanche photodiode coupled to a custom trans-impedance amplifier.

physics.ins-det↗

arXiv2014

Characterising encapsulated nuclear waste using cosmic-ray muon tomography

Tomographic imaging techniques using the Coulomb scattering of cosmic-ray muons have been shown previously to successfully identify and characterise low- and high-Z materials within an air matrix using a prototype scintillating-fibre tracker system. Those studies were performed as the first in a series to assess the feasibility of this technology and image reconstruction techniques in characterising the potential high-Z contents of legacy nuclear waste containers for the UK Nuclear Industry. The present work continues the feasibility study and presents the first images reconstructed from experimental data collected using this small-scale prototype system of low- and high-Z materials encapsulated within a concrete-filled stainless-steel container. Clear discrimination is observed between the thick steel casing, the concrete matrix and the sample materials assayed. These reconstructed objects are presented and discussed in detail alongside the implications for future industrial scenarios.

physics.ins-det↗

arXiv2013

The Design and Performance of a Scintillating-Fibre Tracker for the Cosmic-ray Muon Tomography of Legacy Nuclear Waste Containers

Tomographic imaging techniques using the Coulomb scattering of cosmic-ray muons are increasingly being exploited for the non-destructive assay of shielded containers in a wide range of applications. One such application is the characterisation of legacy nuclear waste materials stored within industrial containers. The design, assembly and performance of a prototype muon tomography system developed for this purpose are detailed in this work. This muon tracker comprises four detection modules, each containing orthogonal layers of Saint-Gobain BCF-10 2mm-pitch plastic scintillating fibres. Identification of the two struck fibres per module allows the reconstruction of the incoming and Coulomb-scattered muon trajectories. These allow the container content, with respect to the atomic number Z of the scattering material, to be determined through reconstruction of the scattering location and magnitude. On each detection layer, the light emitted by the fibre is detected by a single Hamamatsu H8500 MAPMT with two fibres coupled to each pixel via dedicated pairing schemes developed to ensure the identification of the struck fibre. The PMT signals are read out to QDCs. The design and assembly of the detector system are detailed and presented alongside results from performance studies with data collected after construction. These results reveal high stability during extended collection periods with detection efficiencies in the region of 80% per layer. Minor misalignments of millimetre order have been identified and corrected in software. A first image reconstructed from a test configuration of materials has been obtained using software based on the Maximum Likelihood Expectation Maximisation algorithm. The results highlight the high spatial resolution provided by the detector system. Clear discrimination between the low, medium and high-Z materials assayed is also observed.

physics.ins-det↗

arXiv2013

GEANT4 Simulation of a Scintillating-Fibre Tracker for the Cosmic-ray Muon Tomography of Legacy Nuclear Waste Containers

Cosmic-ray muons are highly penetrative charged particles that are observed at sea level with a flux of approximately one per square centimetre per minute. They interact with matter primarily through Coulomb scattering, which is exploited in the field of muon tomography to image shielded objects in a wide range of applications. In this paper, simulation studies are presented that assess the feasibility of a scintillating-fibre tracker system for use in the identification and characterisation of nuclear materials stored within industrial legacy waste containers. A system consisting of a pair of tracking modules above and a pair below the volume to be assayed is simulated within the GEANT4 framework using a range of potential fibre pitches and module separations. Each module comprises two orthogonal planes of fibres that allow the reconstruction of the initial and Coulomb-scattered muon trajectories. A likelihood-based image reconstruction algorithm has been developed that allows the container content to be determined with respect to the atomic number Z of the scattering material. Images reconstructed from this simulation are presented for a range of anticipated scenarios that highlight the expected image resolution and the potential of this system for the identification of high-Z materials within a shielded, concrete-filled container. First results from a constructed prototype system are presented in comparison with those from a detailed simulation. Excellent agreement between experimental data and simulation is observed showing clear discrimination between the different materials assayed throughout.

nucl-ex↗

arXiv2012

Measurement of the generalized form factors near threshold via $γ^* p \to nπ^+$ at high $Q^2$

We report the first extraction of the pion-nucleon multipoles near the production threshold for the $nπ^+$ channel at relatively high momentum transfer ($Q^2$ up to 4.2 $\rm{GeV^2}$). The dominance of the s-wave transverse multipole ($E_{0+}$), expected in this region, allowed us to access the generalized form factor $G_1$ within the light-cone sum rule (LCSR) framework as well as the axial form factor $G_A$. The data analyzed in this work were collected by the nearly $4π$ CEBAF Large Acceptance Spectrometer (CLAS) using a 5.754 $\rm{GeV}$ electron beam on a proton target. The differential cross section and the $π-N$-multipole $E_{0+}/G_D$ were measured using two different methods, the LCSR and a direct multipole fit. The results from the two methods are found to be consistent and almost $Q^2$ independent.

nucl-ex↗