R. J. Holt
A5015634118- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- High-Energy Particle Collisions Research
- Nuclear physics research studies
- Atomic and Subatomic Physics Research
- Quantum, superfluid, helium dynamics
- Nuclear Physics and Applications
- Atomic and Molecular Physics
- Superconducting Materials and Applications
- Advanced Chemical Physics Studies
- Cold Atom Physics and Bose-Einstein Condensates
- Particle Accelerators and Free-Electron Lasers
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Crystallography and molecular interactions
- Dark Matter and Cosmic Phenomena
- Advanced NMR Techniques and Applications
- Particle accelerators and beam dynamics
- Petroleum Processing and Analysis
- Radiation Therapy and Dosimetry
- X-ray Spectroscopy and Fluorescence Analysis
- Photocathodes and Microchannel Plates
- Non-Destructive Testing Techniques
- Electron and X-Ray Spectroscopy Techniques
- Advanced Frequency and Time Standards
Argonne National Laboratory
2012-2024
California Institute of Technology
2019-2024
University of Illinois Urbana-Champaign
1995-2022
University of New Hampshire
2012
University of Alberta
1999
Stanford University
1992
University of Petroleum
1992
Los Alamos National Laboratory
1977
University of South Carolina
1977
Queen Mary University of London
1965
The HERMES experiment is collecting data on inclusive and semi-inclusive deep inelastic scattering of polarised positrons from targets H, D, 3He. These give information the spin structure nucleon. This paper describes forward angle spectrometer built for this purpose. includes numerous tracking chambers (micro-strip gas chambers, drift proportional chambers) in front behind a 1.3 T.m magnetic field, as well an extensive set detectors particle identification (a lead-glass calorimeter,...
The beam-spin asymmetry in hard electroproduction of photons has been measured. data have accumulated by the HERMES experiment at DESY using HERA 27.6 GeV longitudinally polarized positron beam and an unpolarized hydrogen-gas target. azimuthal distribution produced angle $\ensuremath{\varphi}$ relative to lepton scattering plane was determined with respect helicity state incoming beam. analyzing power $\mathrm{sin}\ensuremath{\varphi}$ moment measured be...
Results are reported from the HERMES experiment at HERA on a measurement of neutron spin structure function $g_1^n(x,Q^2)$ in deep inelastic scattering using 27.5 GeV longitudinally polarized positrons incident $^3$He internal gas target. The data cover kinematic range $0.023
We report the results of a new Rosenbluth measurement proton electromagnetic form factors at Q2 values 2.64, 3.20, and 4.10 GeV2. Cross sections were determined by detecting recoiling proton, in contrast to previous measurements which detected scattered electron. 3%, with relative uncertainties below 1%. The ratio mu(p)G(E)/G(M) was 4%-8% showed approximately 1. These are consistent with, much more precise than, extractions. They inconsistent recent polarization transfer similar precision,...
The $^{1}\mathrm{H}(e,{e}^{\ensuremath{'}}{\ensuremath{\pi}}^{+})n$ cross section was measured at four-momentum transfers of ${Q}^{2}=1.60$ and $2.45\text{ }\text{ }{\mathrm{GeV}}^{2}$ an invariant mass the photon nucleon system $W=2.22\text{ }\mathrm{GeV}$. charged pion form factor (${F}_{\ensuremath{\pi}}$) extracted from data by comparing separated longitudinal electroproduction to a Regge model prediction in which ${F}_{\ensuremath{\pi}}$ is free parameter. results indicate that deviates...
Single-spin asymmetries for semi-inclusive pion production in deep-inelastic scattering have been measured the first time. A significant target-spin asymmetry of distribution azimuthal angle straight phi relative to lepton plane was formed pi(+) electroproduction on a longitudinally polarized hydrogen target. The corresponding analyzing power sinstraight moment cross section is 0.022+/-0.005+/-0.003. This result can be interpreted as effect terms involving chiral-odd spin functions...
The charged pion form factor, ${F}_{\ensuremath{\pi}}({Q}^{2})$, is an important quantity that can be used to advance our knowledge of hadronic structure. However, the extraction ${F}_{\ensuremath{\pi}}$ from data requires a model ${}^{1}\mathrm{H}(e,{e}^{'}{\ensuremath{\pi}}^{+})n$ reaction and thus inherently dependent. Therefore, detailed description factor electroproduction obtained recently at Jefferson Lab presented, with particular focus given dominant uncertainties in this procedure....
The root-mean-square (rms) nuclear charge radius of ^8He, the most neutron-rich all particle-stable nuclei, has been determined for first time to be 1.93(3) fm. In addition, rms ^6He was measured 2.068(11) fm, in excellent agreement with a previous result. significant reduction from ^8He is an indication change correlations excess neutrons and consistent neutron halo structure. experiment based on laser spectroscopy individual helium atoms cooled confined magneto-optical trap. Charge radii...
We have performed precision laser spectroscopy on individual 6He (t(1/2)=0.8 s) atoms confined and cooled in a magneto-optical trap, measured the isotope shift between 4He to be 43 194.772+/-0.056 MHz for 2(3)S1-3(3)P2 transition. Based this measurement atomic theory, nuclear charge radius of is determined first time method independent models 2.054+/-0.014 fm. The result compared with values predicted by number structure calculations tests their ability characterize loosely bound halo nucleus.
We report on precision measurements of the elastic cross section for electron-proton scattering performed in Hall C at Jefferson Lab. The were made 28 distinct kinematic settings covering a range momentum transfer $0.4<{Q}^{2}<5.5\phantom{\rule{0.3em}{0ex}}{(\mathrm{GeV}∕c)}^{2}$. These represent significant contribution to world's data set ${Q}^{2}$ range, where large discrepancy currently exists between ratio electric magnetic proton form factors extracted from previous and that recently...
This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on structure and interactions gluon-dominated matter, with intent to articulate it broader nuclear community. It was commissioned by managements Brookhaven National Laboratory (BNL) Thomas Jefferson Accelerator Facility (JLab) objective presenting a summary scientific opportunities goals EIC as follow-up 2007 NSAC Long Range plan. document is culmination community-wide effort in following series workshops...
New Jefferson Lab data are presented on the nuclear dependence of inclusive cross section from $^{2}\mathrm{H}$, $^{3}\mathrm{He}$, $^{4}\mathrm{He}$, $^{9}\mathrm{Be}$ and $^{12}\mathrm{C}$ for $0.3<x<0.9$, ${Q}^{2}\ensuremath{\approx}3--6\text{ }\text{ }{\mathrm{GeV}}^{2}$. These represent first measurement EMC effect $^{3}\mathrm{He}$ at large $x$ a significant improvement $^{4}\mathrm{He}$. The do not support previous $A$-dependent or density-dependent fits to suggest that quark...
We present new measurements of electron scattering from high-momentum nucleons in nuclei. These data allow an improved determination the strength two-nucleon correlations for several nuclei, including light nuclei where clustering effects can, first time, be examined. The also include kinematic region three-nucleon are expected to dominate.
The radioactive radium-225 ((225)Ra) atom is a favorable case to search for permanent electric dipole moment. Because of its strong nuclear octupole deformation and large atomic mass, (225)Ra particularly sensitive interactions in the medium that violate both time-reversal symmetry parity. We have developed cold-atom technique study spin precession atoms held an optical trap, demonstrated principle this method by completing first measurement moment, reaching upper limit...
The ratio of the nucleon F_{2} structure functions, F_{2}^{n}/F_{2}^{p}, is determined by MARATHON experiment from measurements deep inelastic scattering electrons ^{3}H and ^{3}He nuclei. was performed in Hall A Facility Jefferson Lab using two high-resolution spectrometers for electron detection, a cryogenic target system which included low-activity tritium cell. data analysis used novel technique exploiting mirror symmetry nuclei, essentially eliminates many theoretical uncertainties...
A single-spin asymmetry in the azimuthal distribution of neutral pions relative to lepton scattering plane has been measured for first time deep-inelastic positrons off longitudinally polarized protons. The analyzing power sinφ moment cross section is 0.019±0.007(stat)±0.003(syst). This result compared asymmetries charged pion production same kinematic range. π0 size as π+ and shows a similar dependence on relevant variables. described by phenomenological calculation based fragmentation...
An internal-target technique was used to make the first measurements of tensor analyzing power ${\mathit{T}}_{20}$ electron-deuteron elastic scattering in four-momentum-transfer range 2--3 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$. Polarized deuterium atoms were confined within a storage cell VEPP-3 electron ring Novosibirsk achieve total target thickness 3\ifmmode\times\else\texttimes\fi{}${10}^{12}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$, 15 times greater than previously possible with...
We have demonstrated Zeeman slowing and capture of neutral $^{225}\mathrm{Ra}$ $^{226}\mathrm{Ra}$ atoms in a magneto-optical trap. The intercombination transition $^{1}S_{0}\ensuremath{\rightarrow}^{3}P_{1}$ is the only quasicycling radium was used for laser-cooling trapping. Repumping along $^{3}D_{1}\ensuremath{\rightarrow}^{1}P_{1}$ extended lifetime trap from milliseconds to seconds. Room-temperature blackbody radiation provide repumping metastable $^{3}P_{0}$ level. measured isotope...
Cross sections for the reaction ${}^{1}\mathrm{H}(e,{e}^{'}{\ensuremath{\pi}}^{+})n$ were measured in Hall C at Thomas Jefferson National Accelerator Facility (JLab) using high-intensity Continuous Electron Beam (CEBAF) to determine charged pion form factor. Data taken central four-momentum transfers ranging from ${Q}^{2}=0.60$ 2.45 ${\mathrm{GeV}}^{2}$ an invariant mass of virtual photon-nucleon system $W=1.95$ and 2.22 GeV. The cross separated into four structure functions...
An intense 120 GeV proton beam incident on an extremely long iron target generates enormous numbers of light-mass particles that also decay within target. If one these decays to a final state with hidden gauge boson, or if such particle is produced as result the initial collision, then weakly interacting hidden-sector may traverse remainder and be detected downstream through its possible ${e}^{+}{e}^{\ensuremath{-}}$, ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$,...
We present a measurement of the longitudinal spin asymmetry A(||) in photoproduction pairs hadrons with high transverse momentum p(T). Data were accumulated by HERMES experiment using 27.5 GeV polarized positron beam and hydrogen target internal to HERA storage ring. For h(+)h(-) p(h(1))(T)>1.5 GeV/c p(h(2))(T)>1.0 GeV/c, measured is = -0. 28+/-0.12(stat)+/-0.02(syst). This negative value contrast positive asymmetries typically deep inelastic scattering from protons, interpreted arise gluon...