arXiv subjects

B. Liu

Publications and source records attributed to B. Liu.

At least 19 recordsLinked to original sources

arXiv2026

The 10-15 GHz radio continuum survey of the Galactic Plane with SKAO

Star formation emerges from the complex interplay between gravity, turbulence, magnetic fields, and stellar feedback, all of which vary across spatial scales and Galactic environments. Over the past decades, extensive multiwavelength surveys of the Galactic Plane have progressively unveiled this complexity. Far-infrared and sub-millimetre surveys have identified and characterized tens of thousands of star-forming regions, revealing their mass, temperature, and evolutionary stage. Complementary molecular-line surveys, spanning several CO transitions and isotopologues, have mapped the gas kinematics from giant molecular clouds down to sub-parsec structures. The advent of interferometers such as ALMA has revolutionized this field, enabling systematic studies of gas dynamics, fragmentation, and collapse in dense clumps at scales of a few thousand astronomical units. At the same time, mid-infrared and radio surveys at frequencies 0.8 <= nu <= 5 GHz have traced ionised gas associated with the earliest and latest phases of massive-star evolution, including thermal radio jets, hypercompact and ultracompact HII regions, supernova remnants, planetary nebulae, and evolved massive stars. Yet, a uniform, Galaxy-wide census of ionised structures and feedback processes remains elusive. A transformational leap forward requires a sensitive, high-resolution radio survey of the Galactic Plane at 10-15 GHz, capable of resolving physical scales smaller than 0.05 pc at distances up to 20 kpc. This is precisely the goal of the SKA-Mid Galactic Plane survey, which will, with its unprecedented sensitivity, angular resolution, and mapping speed, provide the first panoptic view of ionised gas and stellar feedback across the Milky Way.

astro-ph.GA↗

arXiv2026

Features of spherical torus p 11B burning plasmas

A spherical torus (ST) p B11 plasma model that satisfies multi-magnetofluid force balance is developed, which includes small fractions of suprathermal ions with temperatures around 0.5 MeV and suprathermal electrons in the MeV range. Alongside the primary thermal plasma with ion temperatures exceeding 100 keV and densities above 10E20 m-3, these components enhance fusion reaction rates by leveraging the p B11 double-peak fusion cross section. Suprathermal ions and strong toroidal rotation driven by neutral beam injection have been observed in devices such as START, MAST, NSTX, Globus-M2, and ST40. Central-solenoid-free plasma initiation, ramp-up, and sustainment were tested on EXL-50 and replicated on EXL-50U with partial central induction, demonstrating efficient current drive and consistent with the multi-magnetofluid equilibrium model. Motivated by ENN's aneutronic commercial fusion roadmap, this paper presents a rotating, thermally un-equilibrated ST p B11 plasma with unique properties: fluid components experience separate balance under centripetal, electrostatic, and Lorentz forces with common electric and magnetic fields, leading to large rotation speed differences between thermal boron ions and suprathermal protons; a large outboard region with magnetic well and omnigeneity is created, affecting neoclassical transport and gradient-driven turbulence; suprathermal charged particles can extend beyond the last closed flux surface and be limited by plasma-facing components, influencing recycling and pedestal conditions; and the superposition of these plasma components modifies sources and sinks of free energy, prompting renewed evaluation of stability, turbulence, transport, heating, current drive, and flux diffusion. Challenges and opportunities for sustained burn are discussed for a compact p B11 ST with 1.4-meter major radius, 13-MA current, and 3-T toroidal field.

physics.plasm-ph↗

arXiv2026

Offline Commissioning of the St. Benedict Gas Catcher

Precision measurements of $\beta$ decay transitions offer a promising channel through which the Standard Model (SM) can be probed. There is currently an ongoing effort to increase the precision on measurements of $\mathcal{F}t$-values for superallowed $\beta$ decay transitions between mirror nuclides. These allow for a determination of $V_{ud}$ which is complementary to that obtained from pure Fermi $0^+ \rightarrow 0^+$ transitions. The Superallowed Transition BEta-NEutrino Decay Ion Coincidence Trap (St. Benedict), under construction at the Nuclear Science Laboratory (NSL) at the University of Notre Dame, seeks to measure the Fermi-to-Gamow-Teller mixing ratio for transitions between mirror nuclei in order to expand the list of nuclides from which $V_{ud}$ can be extracted. Production and selection of the species of interest will be done in-flight, using the \textit{TwinSol} magnetic separator system. The first element of St. Benedict will be a large volume gas catcher which will thermalize radioactive ion beams for low energy delivery to the rest of the system. Offline commissioning of this gas catcher has been completed using an internal potassium source, and the device demonstrated a transport efficiency upwards of 95\% for pressures of 66 mbar and lower.

physics.ins-det↗

arXiv2026

The N=126 Factory: A New Multi-Nucleon Transfer Reaction Facility

Multi-nucleon transfer (MNT) reactions between two heavy ions offer an effective method of producing heavy, neutron-rich nuclei that cannot currently be accessed efficiently using traditional production techniques. These nuclei are important for understanding many astrophysical phenomena, such as the formation of the r-process $A\sim 195$ abundance peak. The N=126 Factory currently commissioning at Argonne National Laboratory's ATLAS facility will make use of these reactions to allow for the study of these nuclei. To convert MNT reaction products, which have a wide angular distribution, into a collimated, bunched beam suitable for experiments, a series of apparatus will be used. These start with a large-volume gas catcher for stopping the reaction products, which are then extracted through a radiofrequency quadrupole ion guide, undergo preliminary dipole magnetic separation, cooling and bunching in a Cooler-Buncher, and final separation using a multi-reflection time-of-flight mass separator, before final delivery to experimental systems.

physics.acc-ph↗

arXiv2026

Precision Mass Measurements of \textsuperscript{130}Te, \textsuperscript{130}Sn, and Their Impact on Models for R-Process Nucleosynthesis

The astrophysical rapid neutron capture nucleosynthesis process (r-process) remains an active area of research due to the fact that it occurs in extreme conditions and involves reactions with exotic nuclei that are difficult to study experimentally. For the first time using the Phase-Imaging Ion Cyclotron Resonance (PI-ICR) technique, we measured the mass excesses of \textsuperscript{130}Te, \textsuperscript{130}Sn, and \textsuperscript{130}Sn\textsuperscript{m} with the Canadian Penning Trap (CPT). Our results show good agreement with previous Penning trap values obtained using the Time-of-Flight Ion Cyclotron Resonance (TOF-ICR) and the Fourier Transform Ion Cyclotron Resonance (FT-ICR) techniques, while being twice as precise for \textsuperscript{130}Sn. These new mass excesses were added to a SkyNet network calculation to determine their impact on r-process abundances and to find the best astrophysical conditions to reproduce the Solar System r-process abundance pattern. Finally, by treating lighter and heavier elements separately, we assess the relative frequency of events producing elements in a cold versus a hot r-process scenario.

nucl-ex↗

arXiv2026

Precise Mass Measurement of the $^{149}$La-$^{149}$Ce-$^{149}$Pr isobaric chain

Penning trap mass measurements of $^{149}$La, $^{149}$Ce, and $^{149}$Pr were performed with the Canadian Penning Trap (CPT) at the CARIBU facility of Argonne National Laboratory using the phase-imaging ion-cyclotron-resonance technique. The resulting mass excess of $^{149}$La differs by 221 keV from a recent JYFLTRAP measurement, resulting in a significant change in the profile of the two-neutron separation energy for that isotopic chain. The mass excesses of $^{149}$Ce and $^{149}$Pr are determined with an eight-fold improvement in precision compared to previous time-of-flight ion-cyclotron-resonance measurements; the $^{149}$Ce value is consistent with AME2020, while the $^{149}$Pr mass excess is lower by 17.5 keV. The mass excesses of $^{149}$La and $^{149}$Pr reported in this work have been confirmed recently by a measurement with a multi-reflection time-of-flight mass spectrometer coupled to a $\beta$-time of flight detector at RIKEN, providing further validation of the present results.

nucl-ex↗

arXiv2025

Exploration for Astromers near $^{132}$Sn with the Canadian Penning Trap

Nuclear isomers can have significant impacts on astrophysical nucleosynthesis processes, with recent efforts demonstrating that the population of isomeric states with different half-lives may require separate treatment in reaction networks to accurately capture the differences in heating or in identifiable electromagnetic signals. Several potential so-called ``astromers'' in tin and antimony isotopes near doubly-magic $^{132}$Sn were identified and direct mass measurements of their ground and isomeric states were performed with the Canadian Penning Trap at Argonne National Laboratory's CARIBU facility, and their impact on astrophysical reaction rates and in reaction networks calculated. It was found that $^{129g,m}$Sn, with measured mass excesses of $-80 593.2(25)$ keV and $-80 557.4(25)$ keV, respectively, and an excitation energy of $35.8(35)$ keV, behaves as an astromer during neutron capture in the $i$-process and in the $r$-process.

nucl-ex↗

arXiv2025

Baryon-antibaryon photoproduction cross sections off the proton

The GlueX experiment at Jefferson Lab has observed $p\bar{p}$ and, for the first time, $\Lambda\bar{\Lambda}$ and $p\bar{\Lambda}$ photoproduction from a proton target at photon energies up to 11.6 GeV. The angular distributions are forward peaked for all produced pairs, consistent with Regge-like $t$-channel exchange. Asymmetric wide-angle anti-baryon distributions show the presence of additional processes. In a phenomenological model, we find consistency with a double $t$-channel exchange process where anti-baryons are created only at the middle vertex. The model matches all observed distributions with a small number of free parameters. In the hyperon channels, we observe a clear distinction between photoproduction of the $\Lambda\bar{\Lambda}$ and $p\bar{\Lambda}$ systems but general similarity to the $p\bar{p}$ system. We report both total cross sections and cross sections differential with respect to momentum transfer and the invariant masses of the created particle pairs. No narrow resonant structures were found in these reaction channels. The suppression of $s\bar{s}$ quark pairs relative to $d\bar{d}$ quark pairs is similar to what has been seen in other reactions.

hep-ex↗

arXiv2025

Threshold $J/\psi$ Photoproduction as a Probe of Nuclear Gluon Structure

The nuclear EMC effect is the observation that quark distributions in bound nucleons experience significant modification at large $x$ relative to free nucleons. Despite decades of measurements verifying the presence of this effect in quarks across a wide range of nuclei, behavior of large-$x$ gluons in nuclei remains almost completely unknown. As the nuclear physics community seeks out new observables to try to elucidate the mechanisms behind the EMC effect, it becomes striking that we remain ignorant regarding the impact of nuclear effects on gluonic behavior. Recent photonuclear data using the Hall D photon beam have enabled the first measurement of $J/\psi$ photoproduction from nuclei near and below the energy threshold, with the results highlighted in Physical Review Letters as an Editors' Suggestion. These data have placed the first, and currently only, constraints on the behavior of large-$x$ gluons within bound nucleons. However, compared to the quantity of data which currently informs our knowledge of the quark-sector EMC effect, these data are extremely limited, and remain unable to conclusively observe or exclude large modification of gluon distributions. A high-luminosity photonuclear experiment will enable a precision measurement of incoherent $J/\psi$ photoproduction at and below the threshold region. This data will provide the first stringent constraints on nuclear modification of gluon structure or other exotic effects which could impact the production of $J/\psi$ from nuclei. We request 85 PAC days at Hall D using the GlueX detector with a 12 GeV electron beam energy and a coherent photon peak energy of $8$ GeV, split into 80 days using a $^4$He target and 5 calibration days using a $^2$H target.

nucl-ex↗

arXiv2025

Fractional Quantum Multiferroics from Coupling of Fractional Quantum Ferroelectricity and Altermagnetism

Multiferroics, which combine ferroelectric and magnetic order, offer a transformative platform for next-generation electronic devices. However, the intrinsic competition between the mechanisms driving ferroelectricity and magnetism in single-phase materials severely limits their performance, typically resulting in weak magnetoelectric coupling at room temperature. Here, we propose a solution to this long-standing challenge through the novel concept of fractional quantum multiferroics (FQMF), where strong magnetoelectric coupling is naturally realized by coupling fractional quantum ferroelectricity (FQFE) with altermagnetism (AM). Symmetry analysis shows that reversing the FQFE polarization necessarily inverts the AM spin splitting under parity-time ($\mathcal{PT}$) or time-reversal ($\mathcal{T}\tau$) operations. A minimal tight-binding model reproduces this effect, demonstrating electrically driven spin control without rotating the N\'eel vector. First-principles calculations further identify a broad family of candidate materials in two and three dimensions including bulk MnTe, Cr$_2$S$_3$, Mn$_4$Bi$_3$NO$_{15}$ and two-dimensional AB$_2$ bilayers such as MnX$_2$ (X=Cl, Br, I), CoCl$_2$, CoBr$_2$, and FeI$_2$. Notably, MnTe exhibits a high N\'eel temperature ($\sim$300 K) and a large electrically switchable spin splitting ($\sim$0.8 eV), demonstrating room-temperature magnetoelectric performance that surpasses that of conventional multiferroics. To further showcase the technological potential, we propose an electric-field-controlled FQMF tunnel junction based on MnTe that achieves tunneling magnetoresistance exceeding 300\%. This work establishes FQMF as a distinct and promising route to achieving room-temperature strong magnetoelectric coupling, opening a new avenue for voltage-controlled spintronics.

cond-mat.mtrl-sci↗

arXiv2025

Realization of Phonon FETs in 2D material through Engineered Acoustic Mismatch

Field-effect transistors (FETs) predominantly utilize electrons for signal processing in modern electronics. In contrast, phonon-based field-effect transistors (PFETs)-which employ phonons for active thermal management-remain markedly underdeveloped, with effectively reversible thermal conductivity modulation posing a significant challenge. Herein, we propose a novel PFET architecture enabling reversible thermal conductivity modulation. This design integrates a substrate in the central region with a two-dimensional (2D) material to form an engineered junction, exploiting differences in out-of-plane acoustic phonon properties to regulate heat flow. Molecular dynamics simulations of a graphene (Gr)/hexagonal boron nitride (h-BN) junction demonstrate a substantial thermal conductivity reduction up to 44-fold at 100 K. The effect is maintained at room temperature and across diverse substrates, confirming robustness. This work establishes a new strategy for dynamic thermal management in electronics.

physics.comp-ph↗

arXiv2025

Rim destabilization and re-formation upon severance from its expanding sheet

Upon radial liquid sheet expansion, a bounding rim forms, with a thickness and stability governed, in part, by the liquid influx from the unsteady connected sheet. We examine how the thickness and fragmentation of such a radially expanding rim change upon its severance from its sheet, absent of liquid influx. To do so, we design an experiment enabling the study of rims pre and post severance by vaporizing the thin neck connecting the rim. We confirm that the severed rim follows a ballistic motion, with a radial velocity inherited from the sheet at severance time. We identify that the severed rim undergoes fragmentation in two types of junctions: the base of inherited, pre-severance, ligaments and the junction between nascent rim corrugations, with no significant distinction between the two associated timescales. The number of ligaments and fragments formed is captured well by the theoretical prediction of rim corrugation and ligament wavenumbers established for unsteady expanding sheets upon droplet impact on surfaces of comparable size to the droplet, and with the sheet thickness profiles in both systems having the same functional form. Our findings are robust to changes in impacting laser energy and initial droplet size. Finally, we report and analyze the re-formation of the rim on the expanding sheet and propose a prediction for its characteristic corrugation timescale. Our findings highlight the fundamental mechanisms governing interfacial destabilization of connected fluid-fed expanding rims that become severed, thereby clarifying destabilization of freely radially expanding toroidal fluid structures absent of fluid influx.

physics.flu-dyn↗

arXiv2025

Primordial black holes as dark matter candidates: Multi-frequency constraints from cosmic radiation backgrounds

Aims. This study investigates the role of primordial black holes (PBHs) in shaping cosmic radiation backgrounds--the cosmic X-ray background (CXB), the Lyman-Werner background (LWB), and the cosmic radio background (CRB)--and evaluates their viability as dark matter (DM) candidates based on observational constraints and theoretical limits. Methods. PBH accretion is modelled using analytical frameworks that include electron advection-dominated accretion flows (eADAF), standard advection-dominated accretion flows (ADAF), luminous hot accretion flows (LHAF), and thin disks. Emission from PBHs in both dark matter halos and the intergalactic medium (IGM) is computed. We assess the impact of variations in model assumptions, such as halo gas density profiles, gas velocities, and emission models. The results are compared with observational limits and theoretical thresholds to constrain the PBH fraction as DM for masses between 1 and 100 solar masses Results. PBHs may contribute up to 99, 93, 80, and 91 per cent of the unresolved soft X-ray background for masses of 1, 10, 33, and 100 solar masses, respectively, and about 33-39 per cent of the hard X-ray background. These contributions limit the PBH DM fraction to 7e-3, 6e-4, 6e-4, and 7e-4, respectively, in our baseline model. These constraints are consistent with those from the LWB, ensuring molecular cooling and early star formation are preserved. However, explaining the radio background excess and the EDGES signal would require PBH fractions well above these limits. For 1 solar mass, excluding ADAF subregimes relaxes the constraint to 3e-2, highlighting the sensitivity to accretion physics. Variations in model assumptions introduce only minor differences in the predicted backgrounds.

astro-ph.CO↗

arXiv2025

Measurement of the Total Compton Scattering Cross Section between 6.5 and 11 GeV

The total cross section for Compton scattering off atomic electrons, $\gamma+e\rightarrow\gamma'+e'$, was measured using photons with energies between 6.5 and 11.1 GeV incident on a $^9$Be target as part of the PrimEx-eta experiment in Hall D at Jefferson Lab. This is the first measurement of this fundamental QED process within this energy range. The total uncertainties of the cross section, combining the statistical and systematic components in quadrature, averaged to 3.4% across all energy bins. This not only demonstrates the capability of this experimental setup to perform precision cross-section measurements at forward angles but also allows us to compare with state-of-the-art QED calculations.

nucl-ex↗

arXiv2025

$^{28}$Al Half-life Measurement and the negative mirror asymmetry between the $^{28}$Al($\beta^-$)$^{28m}$Si and $^{28}$P($\beta^+$)$^{28m}$Si decays

In the past, the mirror asymmetry parameter has been proposed as a probing mechanism for the presence of beyond the Standard Model second-class currents in nuclear beta decay transitions. However, this was hindered by large uncertainties in the required nuclear structure correction terms. Recently, a new calculation of these corrections attempted, but could not fully explain the negative mirror asymmetry between the $^{28}$Al($\beta^-$)$^{28m}$Si and $^{28}$P($\beta^+$)$^{28m}$Si decays. To put the mirror asymmetry parameter on a more solid footing, the half-life of $^{28}$Al was measured for the first time using a radioactive ion beam at the Nuclear Science Laboratory of the University of Notre Dame. The new result, $t_{1/2}=$134.432(34) s, is consistent with most of the past data except for one highly discrepant measurement. The new mirror asymmetry parameter of -3.5(10)$\%$ obtained still does not agree with nuclear structure calculations.

nucl-ex↗

arXiv2025

Off-line Commissioning of the St. Benedict Radiofrequency Quadrupole Cooler-Buncher

The St. Benedict ion trapping system, which aims to measure the $\beta-\nu$ angular correlation parameter in superallowed-mixed mirror transitions, is under construction at the University of Notre Dame. These measurements will provide much-needed data to improve the accuracy of the $V_{ud}$ element of the CKM matrix. One of the major components of this system is the radio frequency quadrupole cooler-buncher, which is necessary to create low-emittance ion bunches for injection into the measurement Paul trap. The off-line commissioning of the cooler-buncher, using a potassium ion source, determined that the device could produce cooled ion bunches characterized by a 50-ns full-width-half-maximum time width. The commissioning results also determined the trapping efficiency to be 93(1)$\%$ and the trapping half-life to be 20.0(5) s.

physics.ins-det↗

arXiv2025

Astrophysical significance of the isomer $^{119m}$Ag demonstrated through direct mass measurement

The abundance of elements heavier than iron produced via the astrophysical rapid-neutron capture process depends sensitively on the atomic mass of the involved nuclei as well as the behavior of a few special types of nuclear isomers called astromers. High-precision mass measurements of $^{119}$Cd, $^{119}$Ag and their respective isomeric states have been performed with the Phase Imaging-Ion Cyclotron Resonance (PI-ICR) method with a precision of $\delta m/m \approx 10^{-8}$ using the Canadian Penning Trap (CPT). The ground state mass excess, as well as the excitation energy, agrees with recent Penning Trap measurements from JYFLTRAP. Network calculations using these new measurements revealed that, contrary to previous expectations, $^{119m}$Ag behaves as an astromer which significantly affects the population of $^{119}$Ag.

nucl-ex↗

arXiv2025

High-Performance Nonvolatile Spin FETs from 2D Metallic Ferromagnetic and Ferroelectric Multiferroic Heterostructure

All-electric-controlled nonvolatile spin field-effect transistors (SFETs) based on two-dimensional (2D) multiferroic van der Waals (vdW) heterostructures hold great promise for advanced spintronics applications. However, their performance is hindered by the limited availability of 2D magnetic materials that can switch effectively between metallic and semiconducting states with sizable bandgaps controlled by ferroelectric polarization. Most studies have focused on materials that are naturally semiconducting, achieving a metallic state by modifying the ferroelectric polarization. In this work, we introduce an innovative approach that uses interface effects to convert inherently metallic 2D magnetic materials into half-metals and induce half-semiconducting behavior through changes in ferroelectric polarization. Density functional theory (DFT) calculations on the CrPS3/Sc2CO2 heterostructure demonstrate that the ferroelectric polarization of Sc2CO2 monolayers can adjust the electronic structure of CrPS3, enabling a switch from half-metallic to half-semiconducting states. Building on these insights, we designed a nonvolatile SFET and analyzed its transport properties using the nonequilibrium Green's function (NEGF) method combined with DFT. Our results show that reversing the ferroelectric polarization achieves an on/off current ratio exceeding 5000000%, and the heterostructure generates nearly 100% spin-polarized current with a current density of up to 6500 {\mu}A/{\mu}m at bias voltage below 0.2 V. These findings highlight a promising pathway for developing high-performance SFETs that surpass existing 2D heterojunction materials.

cond-mat.mtrl-sci↗