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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

The MUSE Target Chamber Post Veto

The Muon Scattering Experiment (MUSE) was developed to address the proton radius puzzle through simultaneous electron–proton and muon-proton scattering using the Paul Scherrer Institute’s πM1 secondary beamline. MUSE uses a large-solid-angle, non-magnetic spectrometer to detect beam particles scattering from a liquid hydrogen cell contained within a vacuum chamber. Due to the large scattering windows, the structural integrity of the chamber is supported by posts located at small scattering angles. While out of the acceptance, particles in the tails of the beam distribution can strike these posts, causing a significant trigger background. We describe the design and performance of the Target Chamber Post Veto (TCPV) detector installed inside the vacuum chamber to remove these background events at the trigger level.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

The MUSE beamline calorimeter

The MUon Scattering Experiment (MUSE) was motivated by the proton radius puzzle arising from the discrepancy between muonic hydrogen spectroscopy and electron–proton measurements. The MUSE physics goals also include testing lepton universality, precisely measuring two-photon exchange contribution, and testing radiative corrections. MUSE addresses these physics goals through simultaneous measurement of high precision cross sections for electron–proton and muon–proton scattering using a mixed-species beam. The experiment will run at both positive and negative beam polarities. Measuring precise cross sections requires understanding both the incident beam energy and the radiative corrections. For this purpose, a lead-glass calorimeter was installed at the end of the beam line in the MUSE detector system. Here, in this article, we discuss the detector specifications, calibration and performance. We demonstrate that the detector performance is well reproduced by simulation, and meets experimental requirements.

Calorimeter↗
DOE OSTI2024

Exploring the Strong Interaction of Three-Body Systems at the LHC

Deuterons are atomic nuclei composed of a neutron and a proton held together by the strong interaction. Unbound ensembles composed of a deuteron and a third nucleon have been investigated in the past using scattering experiments, and they constitute a fundamental reference in nuclear physics to constrain nuclear interactions and the properties of nuclei. In this work, K + -d and p-d femtoscopic correlations measured by the ALICE Collaboration in proton-proton (pp) collisions at $\sqrt{s}$ = 13 TeV at the Large Hadron Collider (LHC) are presented. It is demonstrated that correlations in momentum space between deuterons and kaons or protons allow us to study three-hadron systems at distances comparable with the proton radius. The analysis of the K + -d correlation shows that the relative distances at which deuterons and protons or kaons are produced are around 2 fm. The analysis of the p-d correlation shows that only a full three-body calculation that accounts for the internal structure of the deuteron can explain the data. In particular, the sensitivity of the observable to the short-range part of the interaction is demonstrated. These results indicate that correlations involving light nuclei in pp collisions at the LHC will also provide access to any three-body system in the strange and charm sectors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

The nuclear charge radius of 13 C

The size is a key property of a nucleus. Accurate nuclear radii are extracted from elastic electron scattering, laser spectroscopy, and muonic atom spectroscopy. The results are not always compatible, as the proton-radius puzzle has shown most dramatically. Beyond helium, precision data from muonic and electronic sources are scarce in the light-mass region. The stable isotopes of carbon are an exception. We present a laser spectroscopic measurement of the root-mean-square (rms) charge radius of 13 C and compare this with ab initio nuclear structure calculations. Measuring all hyperfine components of the 2 3 S → 2 3 P fine-structure triplet in 13 C 4+ ions referenced to a frequency comb allows us to determine its center-of-gravity with accuracy better than 2 MHz although second-order hyperfine-structure effects shift individual lines by several GHz. We improved the uncertainty of R c ( 13 C) determined with electrons by a factor of 6 and found a 3σ discrepancy with the muonic atom result of similar accuracy.

Müller, Patrick [Technical Univ. of Darmstadt (Ger↗
DOE OSTI2025

Violation of energy conditions and the gravitational radius of the proton

The energy-momentum tensor (EMT) of the proton encodes fundamental information about its mass, pressure, and shear distributions. Using recent lattice QCD data for the gravitational form factors, we show that the Breit-frame Wigner EMT may be of Hawking-Ellis type IV in the proton’s core. Such EMT violates all pointwise energy conditions and lacks a causal rest frame so that the usual mechanical picture fails at short distances. We define the —a new hadronic observable—marking the scale where the EMT becomes ordinary (type I) and the classical interpretation is restored. We also derive from the averaged null energy condition nonperturbative, model-independent quantum field theory constraints on gravitational form factors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1977

Landau damping and steepening of interplanetary nonlinear hydromagnetic waves

According to collisionless shock theories, the thickness of a shock front should be of the order of the characteristic lengths of the plasmas (the Debye length, the proton and Larmor radii, etc.). Chao and Lepping (1974), found, however, that 30% of the observed interplanetary shocks at 1 AU have thicknesses much larger than these characteristic lengths. It is the objective of the present paper to investigate whether the competition between nonlinear steepening and Landau damping can result in a wave of finite width that does not steepen into a shock. A heuristic model of such a wave is developed and tested by the examples of two structures that are qualitatively shocklike, but thicker than expected from theory. It is found that both events are in the process of steepening and their limiting thicknesses due to Landau damping are greater than the corresponding proton Larmor radius for both structures as observed at Mariner 5 (nearer the sun than 1 AU) but are comparable to the proton Larmor radius for Explorer (near 1 AU) observations.

Barnes, A.↗
NASA NTRS2012

Dissipation of Turbulence in the Solar Wind as Measured by Cluster

Turbulence in fluids and plasmas is a scale-dependent process that generates fluctuations towards ever-smaller scales until dissipation occurs. Recent Cluster observations in the solar wind demonstrate the existence of a cascade of magnetic energy from the scale of the proton Larmor radius, where kinetic properties of ions invalidate fluid approximations, down to the electron Larmor radius, where electrons become demagnetized. The cascade is quasi-two-dimensional and has been interpreted as consisting of highly oblique kinetic Alfvenic fluctuations that dissipate near at the electron gyroradius scale via proton and electron Landau damping. Here we investigate for the first time the spatial properties of the turbulence at these scales. We report the presence of thin current sheets and discontinuities with spatial sizes greater than or approximately equal to the proton Larmor radius. These isolated structures may be manifestations of intermittency, and such would localize sites of turbulent dissipation. Studying the relationship between turbulent dissipation, reconnection and intermittency is crucial for understanding the dynamics of laboratory and astrophysical plasmas.

Goldstein, Melvyn↗
DOE OSTI2026

Search for pair production of heavy resonances in final states with a photon and large-radius jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search for the pair production of heavy spin-1/2 or spin-3/2 resonances (𝑡*) in proton-proton collisions at $\sqrt{s}$ =13 TeV is presented. Data collected with the CMS detector at the CERN LHC from 2016 to 2018 corresponding to an integrated luminosity of 138 fb −1 are used. The analysis targets benchmark signal scenarios where one 𝑡* decays into a top quark (𝑡) and a photon (𝛾), and the other into a 𝑡 quark and a gluon (𝑔), i.e., 𝑝⁢𝑝 → $𝑡^*\overline{⁢𝑡^*}$ → 𝑡⁢𝑡⁢𝛾⁢𝑔. All-hadronic final states from the 𝑡 pair decay chain are selected using jet substructure techniques. The signal is probed as a function of the 𝑡* candidate mass, which is reconstructed using the photon and a top quark candidate jet. No significant deviation from the background-only hypothesis is found. Observed (expected) upper limits on the signal cross section at 95% confidence level are set, excluding masses of spin-1/2 𝑡* particles below 930 (930) GeV and spin-3/2 𝑡* particles below 1330 (1390) GeV. This analysis marks the first search for heavy resonances in the $𝑡\bar{⁢𝑡}𝛾⁢𝑔$ channel. Exploiting the high-energy photon to reduce the backgrounds, this search achieves sensitivity competitive with 𝑝⁢𝑝 → $𝑡^*\overline{⁢𝑡^*}$ → $𝑡\bar{⁢𝑡}⁢𝑔⁡𝑔$ searches for spin-1/2 𝑡* despite the small expected 𝑡* → 𝑡⁢𝛾 branching fraction.

hadron colliders↗
NASA NTRS1994

Pickup protons and pressure-balanced structures: Voyager 2 observations in merged interaction regions near 35 AU

Five pressure-balanced structures, each with a scale of the order of a few hundredths of an astonomical unit (AU), were identified in two merged interaction regions (MIRs) near 35 AU in the Voyager 2 plasma and magnetic field data. They include a tangential discountinuity, simple and complex magnetic holes, slow correlated variations among the plasma and magnetic field parameters, and complex uncorrelated variations among the parameters. The changes in the magnetic pressure in these events are balanced by changes in the pressure of interstellar pickup protons. Thus the pickup protons probably play a major role in the dynamics of the MIRs. The solar wind proton and electron pressures are relatively unimportant in the MIRs at 35 AU and beyond. The region near 35 AU is transition region: the Sun is the source of the magnetic field, but the interstellar medium in source of pickups protons. Relative to the solar wind proton guyroadius, the thicknesses of the discontinuities and simple magnetic holes observed near 35 AU are at least an order of magnitude greater than those observed at 1 AU. However, the thicknesses of the tangential discontinuity and simple magnetic holes observed near 35 AU (in units of the pickup proton Larmor radius) are comparable to those observed at 1 AU (in units of the solar wind proton gyroradius). Thus the gyroradius of interstellar pickup protons controls the thickness of current sheets near 35 AU. We determine the interstellar pickup proton pressure in the PBSs. Using a model for the pickup proton temperature, we estimate that the average interstellar pickup proton pressure, temperature, and density in the MIRs at 35 AU are (0.53 +/- 0.14) x 10(exp -12) erg/cu cm, (5.8 +/- 0.4) x 10(exp 6) K and (7 +/- 2) x 10(exp -4)/cu cm.

Burlaga, L. F.↗
DOE OSTI2024

Absorptive corrections to the electromagnetic form factor in high-energy elastic proton-proton scattering

Recently, it was noted that absorptive corrections to the electromagnetic form factor in high-energy proton-proton scattering are important for the theoretical interpretation of the p ↑ p and p ↑ A analyzing power A N ( t ) measurements with the Hydrogen Jet Target polarimeter (HJET) at RHIC. Here, a concise expression for the absorptive correction was derived within the eikonal approach. The resulting analysis reveals a systematic bias, nearly independent of the beam energy, in the experimental determination of the real-to-imaginary ratio ρ when absorption effects are overlooked in the data analysis. Quantification of this bias, as ρ meas = ρ + ( 0.036 ± 0.016 ) bias , was achieved using a Regge fit applied to available proton-proton measurements of ρ meas ( s ) and σ tot meas ( s ) . Considering the potential impact of such an effect on the experimentally determined A N ( t ) , one may enhance consistency between the HJET and STAR measurements of the hadronic spin-flip amplitude. While the sign of the bias in the value of ρ aligns with the anticipated effective increase in the proton charge radius in p p scattering due to absorption, it amplifies the observed discrepancy between σ tot meas and ρ meas values at s = 13 TeV as measured in the TOTEM experiment. Evaluation (using published TOTEM data) of the measured proton-proton d σ / d t dependence on the absorptive corrections indicated that possible soft photon corrections to the hadronic amplitude slope may be essential for such data analysis. Published by the American Physical Society 2024

43 PARTICLE ACCELERATORS↗
NASA NTRS1972

Observations of the solar plasma using radio scattering and scintillation methods

Observations of the solar plasma using the interplanetary scintillation technique have been made at radial distances of 0.03 to 1.2 AU. The solar wind is found to be independent of ecliptic latitude and radial distance, except close to the sun where acceleration is observed. Plasma density irregularities on a scale near the proton gyro radius, which modulate the mean density by about 1 percent, are present throughout the observed range of radial distance.

Hewish, A.↗
DOE OSTI2026

Nuclear Radii of Proton-Unbound Systems

Nuclear radius is a fundamental structural observable that informs many properties of atomic nuclei and nuclear matter. Experimental studies of radii in drip line nuclei are in the forefront of research with radioactive ion beams. Of particular interest are charge radii of proton-unbound nuclei that will soon be approached in laser spectroscopy. In this Letter, using the complex-energy approach and direct time propagation, we investigate the radius of the proton resonance whose size is ill defined in the standard stationary quantum-mechanical description. An early-time plateau is identified during which the radius of the Gamow resonance coincides with the real-energy radius accessible experimentally. We demonstrate a nonmonotonic dependence of the complex radius on decay energy and a local increase of the charge radius across the threshold (a halolike enhancement).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1994

Low-freqency instabilities and the resulting velocity distributions of pickup ions at comet Halley

The interaction between the solar wind and newborn cometary ions is studied using a new analytical theory as well as one- and two-dimensional hybrid simulations. Using the observed parameters upstream of the comet Halley, a detailed study of wave excitation and the resulting particle distributions is presentd. Linear theory as well as simulations show that a variety of modes such as the fast magnetosonic mode, high frequency whistlers and obliquely propagating Alfven ion cyclotron waves can be excited. However, parallel propagating waves are found to be dominant in the wave spectrum and to control the scattering of the pickup ions. Several features of the observed distributions of pickup protons are explained. In particular, it is shown that the observed asymmetric pitch distribution for the pickup protons is due to the small saturation amplitude of the waves for the given parameters. Water group associated waves can lead to energy diffusion and further pitch angle scattering of protons. This effect is most likely to be important in the vicinity of the bow shock of comet Halley where the density of water group ions becomes comparable to that of protons. It is shown that the observed increase in the radius of the proton velocity shell just outside the bow shock can be due to water group waves. The nearby isotropic proton pitch angle distribution observed by Neugebauer et al. (1989) just outside the bow shock may, however, be related to the presence of a rotational discontinuity which has been identified in the magnetic field data. Just outside the bow shock, simulations show that parallel propagating water group waves can steepen with attached whistler wave packets. The steepening process at parallel propagation is a transient effect, in an important contrast to the case of steepening at oblique angles. The smaller beam densitites at comet Halley appears to be the main reason not only why waves at comet Halley have smaller amplitudes but also why oblique, steepening magnetosonic waves have not been detected at comet Halley, whereas they have been seen at comet Giacobini-Zinner. Halley, whereas they have been seen at comet Giacobini-Zinner.

Karimabadi, H.↗
DOE OSTI2025

Energy scale and resolution for anti-$k_t$ jets with radius parameters $R$ = 0.2 and 0.6 measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

Jets with different radius parameters R are an important tool for probing quantum chromodynamics processes at different angular scales. Jets with small R = 0.2 are instrumental in measurements of the substructure of large-R jets resulting from collimated hadronic decays of energetic W, Z, and Higgs bosons, top quarks, and of potential new resonances. This paper presents measurements of the energy scale, resolution, and associated uncertainties of jets with radius parameters R = 0.2 and 0.6, obtained using the ATLAS detector. The results are based on 37 fb -1 of proton–proton collision data from the Large Hadron Collider at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV. A new in situ method for measuring jet energy scale differences between data and Monte Carlo simulations is presented. The systematic uncertainties in the jet energy scale for central jets $(|\eta | < 1.2)$ typically vary from 1% to about 5% as a function of $|\eta |$ at very low transverse momentum, $p_T$ of around 20 GeV for both R = 0.2 and 0.6 jets. The relative energy resolution ranges from (35 ± 6)% at $p_T$ = 20 GeV to (6 ± 0.5)% at $p_T$ = 300 GeV for central R = 0.2 jets, and is found to be slightly worse for R + 0.6 jets. Finally, the effect of close-by hadronic activity on the jet energy scale is investigated and is found to be well modelled by the ATLAS Monte Carlo simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

First Measurement of Near-Threshold and Subthreshold 𝐽/𝜓 Photoproduction off Nuclei

We report on the first measurement of J/ψ photoproduction from nuclei in the photon energy range of 7 to 10.8 GeV, extending above and below the photoproduction threshold in the free proton of ∼ 8.2 GeV. The experiment used a tagged photon beam incident on deuterium, helium, and carbon, and the GlueX detector at Jefferson Lab to measure the semi-inclusive A(γ, e + e − p) reaction with a dilepton invariant mass M(e + e − ) ∼ m J/ψ = 3.1 GeV. The incoherent J/ψ photoproduction cross sections in the measured nuclei are extracted as a function of the incident photon energy, momentum transfer, and proton reconstructed missing light-cone momentum fraction. Comparisons with theoretical predictions assuming a dipole form factor allow extracting a gluonic radius for bound protons of p $\sqrt4⟨r^2⟩$ = 0.85 ± 0.14 fm. The data also suggest an excess of the measured cross section for sub-threshold production and for interactions with high missing light-cone momentum fraction protons. The measured enhancement can be explained by modified gluon structure for high-virtuality bound-protons.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Gravitational form factors and mechanical properties of quarks in protons: A basis light-front quantization approach

We compute the gravitational form factors (GFFs) and study their applications for the description of the mechanical properties such as the pressure, shear force distributions, and the mechanical radius of the proton from its light-front wave functions (LFWFs) based on basis light-front quantization (BLFQ). The LFWFs of the proton are given by the lowest eigenvector of a light-front effective Hamiltonian that incorporates a three-dimensional confining potential and a one-gluon exchange interaction with fixed coupling between the constituent quarks solved in the valence Fock sector. We find acceptable agreement between our BLFQ computations and the lattice QCD for the GFFs. Our D -term form factor also agrees well with the extracted data from the deeply virtual Compton scattering experiments at Jefferson Lab, and the results of different phenomenological models. The distributions of pressures and shear forces are similar to those from different models. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
NASA NTRS1996

AMPTE/CCE and SCATHA simultaneous observations of magnetic signatures associated with a substorm onset

Magnetic field signatures associated with a substorm onset event are examined by making use of simultaneous observations from the Active Magnetosphere Particle Tracer Explorer (AMPTE)/Charge Composition Explorer (CCE) and Spacecraft Charging AT High Altitude (SCATHA). The observations of the two satellites are discussed in relation to their differences and the relative positions of the satellites. Despite the small separation between the satellites, AMPTE/CCE observed the start of irregular magnetic field fluctuations a few tens of seconds earlier than SCATHA, indicating that the CCE was within, or closer to, the onset region. It was found that the amplitude of the fluctuations was largest in the north-south component. The results indicate that the magnetic field fluctuations were excited locally and the coherence length was less than a multiple of Larmor radius of thermal protons. It is suggested that the tail current disruption is described as a system of chaotic filamentary electric currents which flow in various directions, but preferentially anti-parallel to the cross-tail current, and that ions play an important role in the triggering of the tail current disruption.

Ohtani, S.↗
NASA NTRS1977

A reexamination of two-fluid solar wind models

The two-fluid solar-wind equations have been solved by a method which is approximately 50 times faster than any previously developed, through the use of asymptotic expansions which are self-consistently iterated upon to find a solution that passes through the critical point. The energy assumptions in two-fluid solar-wind models are reexamined, and the conclusions are as follows: (1) proton thermal conduction may not be neglected, (2) the Coulomb logarithm must be calculated as a function of radius, and (3) the electron and proton temperatures at the base need not be equal, even when the time scale for energy exchange between the species is an order of magnitude smaller than the expansion time at the base. It is possible to reproduce reasonable quiet-time solar-wind parameters at 1 AU, but only if the proton temperature is approximately twice the electron temperature at 1 solar radius. This may indicate that extended proton heating is important in the outer solar corona. Winds with velocities at 1 AU of 450 km/s are generated without nonthermal energy deposition but require high proton temperatures as well as very low densities at the base. Higher-velocity solutions are not possible in a spherically symmetric geometry for reasonable particle fluxes at 1 AU, and it is suggested that these higher-velocity states probably require additional heating, acceleration mechanisms, or nonradial flow.

Nerney, S.↗