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At least 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Josephson dynamics in two-dimensional ring-shaped condensates

We investigate Josephson transport in a fully closed, two-dimensional superfluid circuit formed by a ring-shaped 87 Rb Bose-Einstein condensate that contains two optical barriers acting as movable weak links. Translating these barriers at controlled speeds imposes a steady bias current, enabling direct mapping of the current-chemical-potential (𝐼−Δ⁢𝜇) characteristics. For narrow junctions (𝑤 ≈ 1µ⁢m), the circuit exhibits a pronounced dc branch that terminates at a critical current 𝐼 𝑐 = 9⁢(1) × 10 3 s −1 ; above this threshold, the system switches to an ac, resistive regime. Classical-field simulations that include the moving barriers quantitatively reproduce both the nonlinear 𝐼−Δ⁢𝜇 curve and the measured 𝐼 𝑐 , validating the underlying microscopic picture. Analysis of the ensuing phase dynamics shows that dissipation is mediated by the nucleation and traversal of vortex-antivortex pairs through the junctions, while the bulk condensate remains globally phase locked—direct evidence of the ring's topological constraint enforcing quantized circulation. These results establish a cold-atom analog of a superconducting quantum interference device in which Josephson dynamics can be resolved at the single-vortex level, providing a versatile platform for atomtronic circuit elements, nonreciprocal Josephson devices, and on-chip Sagnac interferometers for multiaxis rotation sensing.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2026

Nuclear spin coherence and RKKY interaction in superconducting Nb 3 Sn

We have investigated the normal and superconducting states of the technologically important compound Nb$_3$Sn using $^{93}$Nb nuclear magnetic resonance. From spin-lattice relaxation we find strong suppression of the zero-temperature superconducting order parameter by magnetic field. Additionally we have identified an anomalously large electron-nuclear exchange interaction from spin-spin relaxation measurements, an order of magnitude beyond that of the nuclear dipolar coupling. This RKKY interaction evolves from normal to superconducting states, becoming essentially Lorentzian in the low temperature limit.

Zhai, Gan [Northwestern U.] (ORCID:000000016623956↗
DOE OSTI2026

Baryon–antibaryon photoproduction cross sections off the proton

The GlueX experiment at Jefferson Lab has observed 𝑝⁢$\overline{p}$ and, for the first time, Λ$\overlineΛ$ and 𝑝$\overlineΛ$ 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 antibaryon distributions show the presence of additional processes. In a phenomenological model, we find consistency with a double-𝑡-channel exchange process where antibaryons 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 Λ$\overlineΛ$ and 𝑝$\overlineΛ$ systems but general similarity to the 𝑝$\overline{p}$ 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$\overline{s}$ quark pairs relative to 𝑑$\overline{d}$ quark pairs is similar to what has been seen in other reactions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

First measurement of 𝑎$^{0}_{2}$⁡(1320) polarized photoproduction cross section

We measure for the first time the differential photoproduction cross section dσ/dt of the a 2 (1320) meson at an average photon beam energy of 8.5 GeV, using data with an integrated luminosity of 104 pb −1 collected by the GlueX experiment. We fully reconstruct the γp → ηπ 0 p reaction and perform a partial-wave analysis in the a 2 (1320) mass region with amplitudes that incorporate the linear polarization of the beam. This allows us to separate for the first time the contributions of natural- and unnatural-parity exchanges. Furthermore, these measurements provide novel information about the photoproduction mechanism, which is critical for the search for spin-exotic states.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Search for the 𝑌⁡(2175) in the Photoproduction Cross Section Measurement of 𝛾⁢𝑝 → 𝜙⁢𝜋 + ⁢𝜋 − ⁢𝑝 at GlueX

Based on 334 pb −1 of photoproduction data collected with the GlueX detector at Jefferson Lab, we have measured for the first time the cross section of the exclusive reaction 𝛾+𝑝→𝜙⁡(1020)⁢𝜋 + ⁢𝜋 − ⁢𝑝 by reconstructing the final state 𝐾 +⁢ 𝐾 − ⁢𝜋 + ⁢𝜋 − ⁢𝑝 produced with a photon beam of energies between 8.0 and 11.6 GeV. Based on the measured differential cross section, we have performed a search for the strangeoniumlike exotic candidate 𝑌⁡(2175), recently renamed to 𝜙⁡(2170). This state has been reported by different 𝑒 + ⁢𝑒 − annihilation experiments and it is addressed here for the first time in a photoproduction experiment. We do not find evidence for this state when using the resonance parameters quoted by the Particle Data Group and provide upper limits on the photoproduction cross section. Instead, we find a structure at a mass of 𝑚⁡(𝜙⁢𝜋 + ⁢𝜋 − ) = 2.24 GeV/𝑐 2 with a statistical significance of about 5⁢𝜎. The parameters of this structure differ from those quoted by the Particle Data Group for the 𝜙⁡(2170) and are consistent with a previous observation in 𝑒 + ⁢𝑒 − annihilation. In addition, there is evidence for a second structure at 1.82 GeV/𝑐 2 .

Exotic mesons↗
DOE OSTI2022

Enhanced low-energy magnetic excitations evidencing the Cu-induced localization in the Fe-based superconductor Fe 0.98 Te 0.5 Se 0.5

Here, we have performed inelastic neutron scattering measurements on optimally doped Fe 0.98 Te 0.5 Se 0.5 and 10% Cu-doped Fe 0.88 Cu 0.1 Te 0.5 Se 0.5 to investigate the substitution effects on the spin excitations in the whole energy range up to 300 meV. It is found that substitution of Cu for Fe enhances the low-energy spin excitations (≤100 meV), especially around the (0.5, 0.5) point, and leaves the high-energy magnetic excitations intact. In contrast to the expectation that Cu with spin 1/2 will dilute the magnetic moments contributed by Fe with a larger spin, we find that the 10% Cu doping enlarges the effective fluctuating moment from 2.85 to 3.13 μB/Fe, although there is no long- or short-range magnetic order around (0.5, 0.5) and (0.5, 0). The presence of enhanced magnetic excitations in the 10% Cu doped sample which is in the insulating state indicates that the magnetic excitations must have some contributions from the local moments, reflecting the dual nature of the magnetism in iron-based superconductors. We attribute the substitution effects to the localization of the itinerant electrons induced by Cu dopants. Furthermore, these results indicate that the Cu doping does not act as electron donor as in a rigid-band shift model, but more as scattering centers that localize the system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Robust Fe divalent state in one-unit-cell $\mathrm{FeSe/SrTiO_3}$ thin films

The orbital occupancy, as the origin of Hund's rule coupling, provides critical information in understanding the multiorbital iron-based superconductors. The one-unit-cell (1UC) FeSe thin film on a SrTiO 3 substrate with superconductive T c above 60 K has been reported with unique electronic structures as well as orbital occupancy. In this paper, we present the x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) study of the FeSe/STO thin films of different thicknesses. Together with the atomic multiplet simulation analysis, the FeSe/STO thin films (from 1UC to 10UC) are shown with the pure 3d6 electronic configuration which is identical to the bulk FeSe. Moreover, 1UC FeSe/STO is found to be distinctively more persistent in hosting the 3d6 configuration other than the thicker films under the oxidization process. The robustness of the 3d6 in 1UC FeSe/STO is discussed as a result of charge transfer from the substrate, as well as a mechanism to maintain the high-T c superconductivity. Additionally our research calls for a further high-resolution RIXS study of the pristine superconductive 1UC FeSe/STO thin film.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Measurement of the photon beam asymmetry in γ → p → K + Σ 0 at E γ = 8.5 GeV

We report measurements of the photon beam asymmetry $\Sigma$ for the reaction $\vec{\gamma} p\to K^+\Sigma^0$(1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected using a linearly polarized photon beam in the energy range of 8.2-8.8 GeV incident on a liquid hydrogen target. The beam asymmetry $\Sigma$ was measured as a function of the Mandelstam variable $t$, and a single value of $\Sigma$ was extracted for events produced in the $u$-channel. These are the first exclusive measurements of the photon beam asymmetry $\Sigma$ for the reaction in this energy range. For the $t$-channel, the measured beam asymmetry is close to unity over the $t$-range studied, $-t=(0.1-1.4)~$(GeV/$c$)$^{2}$, with an average value of $\Sigma = 1.00\pm 0.05$. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the $K^{*}$(892) Regge trajectory. A value of $\Sigma = 0.41 \pm 0.09$ is obtained for the $u$-channel integrated up to $-u=2.0$~(GeV/$c$)$^{2}$.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Measurement of beam asymmetry for π – Δ ++ photoproduction on the proton at E γ = 8.5 GeV

We report a measurement of the $\pi^-$ photoproduction beam asymmetry for the reaction $\vec{\gamma} p \rightarrow \pi^- \Delta^{++}$ using data from the GlueX experiment in the photon beam energy range 8.2--8.8 GeV. The asymmetry $\Sigma$ is measured as a function of four-momentum transfer $t$ to the $\Delta^{++}$ and compared to phenomenological models. We find that $\Sigma$ varies as a function of $t$: negative at smaller values and positive at higher values of $|t|$. The reaction can be described theoretically by $t$-channel particle exchange requiring pseudoscalar, vector, and tensor intermediaries. In particular, this reaction requires charge exchange, allowing us to probe pion exchange and the significance of higher-order corrections to one-pion exchange at low momentum transfer. Constraining production mechanisms of conventional mesons may aid in the search for and study of unconventional mesons. Furthermore, this is the first measurement of the process at this energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Spectroscopy of A=9 hyperlithium with the $(e,e^{\prime}K^{+})$ reaction

Missing mass spectroscopy with the $(e,e^{\prime}K^{+})$ reaction was performed at JLab Hall C for the neutron rich $\Lambda$ hypernucleus $^{9}_{\Lambda}{\rm Li}$. The ground state energy was obtained to be $B_{\Lambda}^{\rm g.s.}=8.84\pm0.17^{\rm stat.}\pm0.15^{\rm sys.}~{\rm MeV}$ by using shell model calculations of a cross section ratio and an energy separation of the spin doublet states ($3/2^{+}_1$ and $5/2^{+}_1$). In addition, peaks that are considered to be states of [$^{8}{\rm Li}(3^{+})\otimes s_{\Lambda}=3/2^{+}_{2}, 1/2^{+}$] and [$^{8}{\rm Li}(1^{+})\otimes s_{\Lambda}=5/2^{+}_{2}, 7/2^{+}$] were observed at $E_{\Lambda}(\#2)=1.74\pm0.27^{\rm stat.}\pm0.11^{\rm sys.}~{\rm MeV}$ and $E_{\Lambda}(\#3)=3.30\pm0.24^{\rm stat.}\pm0.11^{\rm sys.}~{\rm MeV}$, respectively. The $E_{\Lambda}(\#3)$ is larger than shell model predictions by a few hundred keV, and the difference would indicate that a ${\rm ^{5}He}+t$ structure is more developed for the $3^{+}$ state than those for the $2^{+}$ and $1^{+}$ states in a core nucleus $^{8}{\rm Li}$ as a cluster model calculation suggests.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Comparison of heavy-ion transport simulations: Mean-field dynamics in a box

Within the transport model evaluation project (TMEP) of simulations for heavy-ion collisions, the mean-field response is examined here. Specifically, zero-sound propagation is considered for neutron-proton symmetric matter enclosed in a periodic box, at zero temperature and around normal density. The results of several transport codes belonging to two families (BUU-like and QMD-like) are compared among each other and to exact calculations. For BUU-like codes, employing the test particle method, the results depend on the combination of the number of test particles and the spread of the profile functions that weight integration over space. These parameters can be properly adapted to give a good reproduction of the analytical zero-sound features. QMD-like codes, using molecular dynamics methods, are characterized by large damping effects, attributable to the fluctuations inherent in their phase-space representation. Moreover, for a given nuclear effective interaction, they generally lead to slower density oscillations, as compared to BUU-like codes. The latter problem is mitigated in the more recent lattice formulation of some of the QMD codes. Furthermore, the significance of these results for the description of real heavy-ion collisions is discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Measurement of spin density matrix elements in Λ ( 1520 ) photoproduction at 8.2–8.8 GeV

We report on the measurement of spin density matrix elements of the $\Lambda(1520)$ in the photoproduction reaction $\gamma p\rightarrow \Lambda(1520)K^+$, via its subsequent decay to $K^{-}p$. The measurement was performed as part of the GlueX experimental program in Hall D at Jefferson Lab using a linearly polarized photon beam with $E_\gamma =$ 8.2-8.8 GeV. These are the first such measurements in this photon energy range. Results are presented in bins of momentum transfer squared, $-(t-t_\text{0})$. We compare the results with a Reggeon exchange model and determine that natural exchange amplitudes are dominant in $\Lambda(1520)$ photoproduction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Measurement of R = σ L / σ T and the separated longitudinal and transverse structure functions in the nucleon-resonance region

Here we report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 < Q 2 < 5.5 GeV 2 . The data have been used to accurately perform over 170 Rosenbluth-type longitudinal/transverse separations. The precision R = $\sigma_{L} /\sigma _{T}$ data are presented here, along with the first separate values of the inelastic structure functions F 1 and F L in this regime. The resonance longitudinal component is found to be significant. With the new data, quark-hadron duality is observed above Q 2 = 1 GeV 2 in the separated structure functions independently.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Investigation of 48 Ca-induced reactions with 242 Pu and 238 U targets at the JINR Superheavy Element Factory

Experiments using a 48 Ca beam on 238 U and 242 Pu targets to produce superheavy nuclei were performed at the gas-filled separator DGFRS-2 online to the new cyclotron DC280 at the SHE Factory at JINR. The decay properties of 286 Fl and 287 Fl, as well as their α-decay products, were refined after the detection of 25 and 69 new decay chains, respectively. In addition, 16 decay chains of 283 Cn were observed in the 238 U+ 48 Ca reaction. The possibility of existing of isomeric states in the 287 Fl consecutive α decays is discussed. A new α line with an energy of 100–200 keV lower than the main one at 10.19 MeV was observed for the first time for even-even 286 Fl decay. A maximum cross section of $10.4^{+3.5}_{-2.1}$pb was measured for the 242 Pu( 48 Ca,3n) 287 Fl reaction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

New isotope 286 Mc produced in the 243 Am + 48 Ca reaction

In this paper, we present results of the second experiment on the synthesis of Mc isotopes in the 243 Am + 48 Ca reaction performed at the gas-filled separator DGFRS-2 of the SHE Factory at JINR. Here, the new isotope 286 Mc was synthesized, and its half-life of $20^{+98}_{–9}$ ms and α-particle energy of 10.71 ± 0.02 MeV were determined. A 286 Mc α–decay chain was recorded down to the spontaneous fission of 266 Db. The spontaneous fission of 279 Rg was observed for the first time in one of four new decay chains of 287 Mc. The excitation function of the reaction was measured at three 48 Ca energies of 242, 250, and 259 MeV; the latter resulted in the first observation of the 5$\textit{n}$–evaporation channel with a cross section of $0.5^{+1.3}_{–0.4}$ pb. The decay properties of 21 previously known odd–$\textit{Z}$ isotopes were improved. The potential for an electron-capture decay mode is discussed for 288 Mc and 284 Nh isotopes. The half-lives of spontaneously fissioning nuclei produced in the 48 Ca–induced reactions with actinide targets are compared with several theoretical predictions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

First experiment at the Super Heavy Element Factory: High cross section of Mc 288 in the Am 243 + Ca 48 reaction and identification of the new isotope Lr 264

Here, we present results of the first experiment aimed at the synthesis of Mc isotopes in the 243 Am+ 48 Ca reaction performed at the new gas-filled separator DGFRS-2 online to the new cyclotron DC280 at the Super Heavy Element Factory at JINR. Fifty-five new decay chains of 288 Mc and six chains assigned to 289 Mc were detected. The α decay of 268 Db with an energy of 7.6–8.0 MeV, half-life of 16$^{+6}_{-4}$h, and a branch of 55$^{+20}_{-15}$% was registered for the first time, and a new spontaneously fissioning isotope 264 Lr with a half-life of 4.9$^{+2.1}_{-1.3}$h was identified. The cross section for the 243 Am( 48 Ca,3n) 288 Mc reaction was measured to be 17.1$^{+6.3}_{-4.7}$ pb, which is the largest value for the known superheavy nuclei at the island of stability.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Measurement of the J/ψ photoproduction cross section over the full near-threshold kinematic region

Here, we report the total and differential cross sections for $J/\psi$ photoproduction with the large acceptance GlueX spectrometer for photon beam energies from the threshold at 8.2 GeV up to 11.44 GeV and over the full kinematic range of momentum transfer squared, $t$. Such coverage facilitates the extrapolation of the differential cross sections to the forward ($t = 0$) point beyond the physical region. The forward cross section is used by many theoretical models and plays an important role in understanding $J/\psi$ photoproduction and its relation to the $J/\psi$-proton interaction. These measurements of $J/\psi$ photoproduction near threshold are also crucial inputs to theoretical models that are used to study important aspects of the gluon structure of the proton, such as the gluon Generalized Parton Distribution (GPD) of the proton, the mass radius of the proton, and the trace anomaly contribution to the proton mass. We observe possible structures in the total cross section energy dependence and find evidence for contributions beyond gluon exchange in the differential cross section close to threshold, both of which are consistent with contributions from open-charm intermediate states.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Measurement of spin-density matrix elements in ρ ( 770 ) production with a linearly polarized photon beam at E γ = 8.2 – 8.8 GeV

The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized 8.5GeV photons impinging on a hydrogen target which is contained within a detector with near-complete coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson rho(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. Here we confirm a high degree of s-channel helicity conservation at small squared four-momentum transfer t and are able to extract the t-dependence of natural and unnatural-parity exchange contributions to the production process in detail. We confirm the dominance of natural-parity exchange over the full t range. We also find that helicity amplitudes in which the helicity of the incident photon and the photoproduced rho(770) differ by two units are negligible for -t<0.5GeV 2 /c 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗