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Search Results: 1 - 10 of 256516 matches for " D. W. Higinbotham "
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Precision Measurements of the Proton Elastic Form Factor Ratio
D. W. Higinbotham
Physics , 2010, DOI: 10.1063/1.3483410
Abstract: New high precision polarization measurements of the proton elastic form factor ratio in the Q^2 range from 0.3 to 0.7 [GeV/c]^2 have been made. These elastic H(e,e'p) measurements were done in Jefferson Lab's Hall A using 80% longitudinally polarized electrons and recoil polarimetry. For Q^2 greater than 1 [GeV/c]^2, previous polarization data indicated a strong deviation of the form factor ratio from unity which sparked renewed theoretical and experimental interest in how two-photon diagrams have been taken into account. The new high precision data indicate that the deviation from unity, while small, persists even at Q^2 less than 1 [GeV/c]^2.
Electron Spin Precession at CEBAF
D. W. Higinbotham
Physics , 2009, DOI: 10.1063/1.3215753
Abstract: The nuclear physics experiments at the Thomas Jefferson National Accelerator Facility often require longitudinally polarized electrons to be simultaneously delivered to three experimental halls. The degree of longitudinal polarization to each hall varies as function of the accelerator settings, making it challenging in certain situations to deliver a high degree of longitudinal polarization to all the halls simultaneously. Normally, the degree of longitudinal polarization the halls receive is optimized by changing the initial spin direction at the beginning of the machine with a Wien filter. Herein, it is shown that it is possible to further improve the degree of longitudinal polarization for multiple experimental halls by redistributing the energy gain of the CEBAF linacs while keeping the total energy gain fixed.
Understanding Nucleons in the Nuclear Medium
D. W. Higinbotham,V. Sulkosky
Physics , 2010, DOI: 10.1063/1.3483430
Abstract: Recent cross section (e,e'pN) short-range correlation experiments have clearly shown the strong dominance of tensor correlations for (e,e'p) missing momenta greater than the Fermi momentum; while recent D(e,e'p)n and 4He(e,e'p)t asymmetry experiments at low missing momentum have shown small changes from the free nucleon form factor. By doing asymmetry experiments as a function of missing momentum, these results can be linked together and observed as a change of sign in the measured asymmetry. This idea will be presented within the context of the recently completed Jefferson Lab Hall A quasi-elastic, polarized 3He(e,e'N) experiments (N=0,p,n,d) where the asymmetries of several reaction channels were measured with three, orthogonal target-spin directions. Together, these various experiments will help us to better understand nucleons in the nuclear medium.
Nuclear Scaling and the EMC Effect
D. W. Higinbotham,J. Gomez,E. Piasetzky
Physics , 2010,
Abstract: Results of recent EMC effect measurements and nuclear scaling measurements have both been attributed to local nuclear density effects and not properties of the bulk nuclear system. This lead us to the phenomenological observation that the ratio of the slopes in the 0.3 < x_B < 0.7 EMC data scale as the ratio of the x_B > 1 nuclear scaling plateaus. Using this correlation, we developed a phenomenological relation which reproduces the general trends and features of the EMC effect for nuclei from 3He to 56Fe.
Short-Distance Structure of Nuclei
D. W. Higinbotham,E. Piasetzky,S. A. Wood
Physics , 2009, DOI: 10.1088/1742-6596/299/1/012010
Abstract: One of Jefferson Lab's original missions was to further our understanding of the short-distance structure of nuclei. In particular, to understand what happens when two or more nucleons within a nucleus have strongly overlapping wave-functions; a phenomena commonly referred to as short-range correlations. Herein, we review the results of the (e,e'), (e,e'p) and (e,e'pN) reactions that have been used at Jefferson Lab to probe this short-distance structure as well as provide an outlook for future experiments.
E12-14-009: Ratio of the electric form factor in the mirror nuclei 3He and 3H
L. S Myers,D. W. Higinbotham,J. R. Arrington
Physics , 2014,
Abstract: E12-14-009: We propose to extract the ratio of the electric form factor (G_E) of 3He and 3H from the measured ratio of the elastic-scattering cross sections at E_beam = 1.1 GeV. Measurements at low Q^2 ( < 0.1 GeV^2) will allow accurate extraction of G_E with minimal contributions from the magnetic form factor (G_M) and Coulomb corrections. From this data we will extract the difference between the charge radii for 3He and 3H. This short experiment, 1.5 days, will utilize the left Hall A high resolution spectrometer and the one-time availability of a 1 kCi tritium target at Jefferson Lab which has been approved for the E12-10-103, E12-11-112 and E12-14-011 experiments.
Hard probes of short-range nucleon-nucleon correlations
J. Arrington,D. W. Higinbotham,G. Rosner,M. Sargsian
Physics , 2011, DOI: 10.1016/j.ppnp.2012.04.002
Abstract: One of the primary goals of nuclear physics is providing a complete description of the structure of atomic nuclei. While mean-field calculations provide detailed information on the nuclear shell structure for a wide range of nuclei, they do not capture the complete structure of nuclei, in particular the impact of small, dense structures in nuclei. The strong, short-range component of the nucleon-nucleon potential yields hard interactions between nucleons which are close together, generating a high-momentum tail to the nucleon momentum distribution, with momenta well in excess of the Fermi momentum. This high-momentum component of the nuclear wave-function is one of the most poorly understood parts of nuclear structure. Utilizing high-energy probes, we can isolate scattering from high-momentum nucleons, and use these measurements to examine the structure and impact of short-range nucleon-nucleon correlations. Over the last decade we have moved from looking for evidence of such short-range structures to mapping out their strength in nuclei and examining their isospin structure. This has been made possible by high-luminosity and high-energy accelerators, coupled with an improved understanding of the reaction mechanism issues involved in studying these structures. We review the general issues related to short-range correlations, survey recent experiments aimed at probing these short-range structures, and lay out future possibilities to further these studies.
The EMC Effect and High Momentum Nucleons in Nuclei
Hen, O.;Higinbotham, D. W.;Miller, G. A.;Piasetzky, E.;Weinstein, L. B.
High Energy Physics - Phenomenology , 2013,
Abstract: Recent developments in understanding the influence of the nucleus on deep-inelastic structure functions, the EMC effect, are reviewed. A new data base which expresses ratios of structure functions in terms of the Bjorken variable $x_A=AQ^2/(2M_A q_0)$ is presented. Information about two-nucleon short-range correlations from experiments is also discussed and the remarkable linear relation between short-range correlations and teh EMC effect is reviewed. A convolution model that relates the underlying source of the EMC effect to modification of either the mean-field nucleons or the short-range correlated nucleons is presented. It is shown that both approaches are equally successful in describing the current EMC data.
Extracting a free neutron structure function from proton and deuteron deep inelastic scattering data
O. Hen,E. Piasetzky,R. Shneor,L. B. Weinstein,D. W. Higinbotham
Physics , 2011,
Abstract: Due to the lack of a free neutron target the structure function of the neutron cannot be measured directly and is therefore extracted from deuteron and proton DIS data. Because the deuteron is a bound nuclear system, in order to extract the neutron structure function, one needs to apply model dependent theoretical corrections which dominate the uncertainty at the large xB region. We present here a correlation between the magnitude of the EMC effect and the amount of two nucleon Short Range Correlation (2N-SRC) pairs in nuclei. Using this correlation we propose a phenomenological procedure to extract the free neutron structure function in the xB range of 0.3 to 0.7.
Short Range Correlations and the EMC Effect
L. B. Weinstein,E. Piasetzky,D. W. Higinbotham,J. Gomez,O. Hen,R. Shneor
Physics , 2010, DOI: 10.1103/PhysRevLett.106.052301
Abstract: This paper shows quantitatively that the magnitude of the EMC effect measured in electron deep inelastic scattering (DIS) at intermediate $x_B$, $0.35\le x_B\le 0.7$, is linearly related to the Short Range Correlation (SRC) scaling factor obtained from electron inclusive scattering at $x_B\ge 1.$. The observed phenomenological relationship is used to extract the ratio of the deuteron to the free $pn$ pair cross sections, the DIS cross section for a free neutron, and $F_2^n/F_2^p$, the ratio of the free neutron to free proton structure functions. We speculate that the observed correlation is because both the EMC effect and SRC are dominated by the high virtuality (high momentum) nucleons in the nucleus.
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