Precise proton and neutron form factor measurements at Jefferson Lab, using spin observables, have recently made a significant contribution to the unraveling of the internal structure of the nucleon. ...Accurate experimental measurements of the nucleon form factors are a test-bed for understanding how the nucleon’s static properties and dynamical behavior emerge from QCD, the theory of the strong interactions between quarks. There has been enormous theoretical progress, since the publication of the Jefferson Lab proton form factor ratio data, aiming at reevaluating the picture of the nucleon. We will review the experimental and theoretical developments in this field and discuss the outlook for the future.
Nucleon electromagnetic form factors Perdrisat, C.F.; Punjabi, V.; Vanderhaeghen, M.
Progress in particle and nuclear physics,
10/2007, Letnik:
59, Številka:
2
Journal Article
Recenzirano
Odprti dostop
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing ...double-polarization experiments, in comparison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at MIT-Bates, MAMI, and JLab. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed, including the recent progress in the determination of the valence quark generalized parton distributions of the nucleon, as well as to the steady rate of improvements made in the lattice QCD calculations.
Measurements of the production of forward jets from transversely polarized proton collisions at s=500 GeV conducted at the Relativistic Heavy Ion Collider (RHIC) are reported. Our measured jet cross ...section is consistent with hard scattering expectations. Our measured analyzing power for forward jet production is small and positive, and provides constraints on the Sivers functions that are related to partonic orbital angular momentum through theoretical models.
The analyzing powers for proton elastic scattering (
p
A
→
p
X
) and neutron charge exchange (
n
A
→
p
X
) reactions on nuclei have been measured on
C
,
CH
,
C
H
2
and
Cu
targets at incident neutron ...momenta 3.0–4.2 GeV/c by detecting one charged particle in forward direction. The polarized neutron measurements are the first of their kind. The experiment was performed using the Nuclotron accelerator in JINR Dubna, where polarized neutrons and protons were obtained from break-up of a polarized deuteron beam which has a maximum momentum of 13 GeV/c. The polarimeter ALPOM2 was used to obtain the analyzing power dependence on the transverse momentum of the final-state nucleon. These data have been used to estimate the figure of merit of a proposed experiment at Jefferson Laboratory to measure the recoiling neutron polarization in the quasi-elastic
2
H
(
e
,
e
′
n
)
reaction, which yields information on the charge and magnetic elastic form factors of the neutron.
The analyzing powers for neutron charge exchange nA → pX reactions on nuclei have been measured on C, CH2 and Cu targets at incident neutron momenta 3.0 - 4.2 GeV/c by detecting one charged particle ...in forward direction. The polarized neutron measurements are the first of their kind. The experiment was performed using the Nuclotron accelerator in JINR Dubna, where polarized neutrons and protons were obtained from breakup of a polarized deuteron beam which has a maximum momentum of 13 GeV/c. The polarimeter ALPOM2 was used to obtain the analyzing power dependence on the transverse momentum of the final-state nucleon. These data have been used to estimate the figure of merit of a proposed experiment at Jefferson Laboratory to measure the recoiling neutron polarization in the quasi-elastic 2H(e, e′n) reaction, which yields information on the charge and magnetic elastic form factors of the neutron.
The experimental determination of the proton elastic form factors has become a very active field since two experiments at JLab using the double-polarization technique revealed a stark discrepancy ...from the previous Rosenbluth data. In a next step, started in the fall of 2007, a new experiment in Hall C at JLab has pushed the
Q
2
limit from 5.6 to
8.54
GeV
2
, with intermediate points at 5.2 and
6.8
GeV
2
. The kinematics dependence of the form factor ratio at
2.5
GeV
2
has also been investigated. The current status of the data analysis and some preliminary results are reported.
Abstract
The analyzing powers for neutron charge exchange
nA
→
pX
reactions on nuclei have been measured on C, CH2 and Cu targets at incident neutron momenta 3.0 - 4.2 GeV/c by detecting one charged ...particle in forward direction. The polarized neutron measurements are the first of their kind. The experiment was performed using the Nuclotron accelerator in JINR Dubna, where polarized neutrons and protons were obtained from breakup of a polarized deuteron beam which has a maximum momentum of 13 GeV/c. The polarimeter ALPOM2 was used to obtain the analyzing power dependence on the transverse momentum of the final-state nucleon. These data have been used to estimate the figure of merit of a proposed experiment at Jefferson Laboratory to measure the recoiling neutron polarization in the quasi-elastic
2
H
(
e
,
e
′
n
) reaction, which yields information on the charge and magnetic elastic form factors of the neutron.
The form factors of the nucleons Perdrisat, C. F.
Physics of particles and nuclei,
11/2013, Letnik:
44, Številka:
6
Journal Article
Recenzirano
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing ...double-polarization experiments, in comparison with with previous unpolarized cross section data. Here we will review the experimental data base in view of the new results for the proton and the neutron, obtained at MIT-Bates, JLab and MAMI. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed. In particular, the possibility that the proton is non-spherical in its ground state, and that the transverse charge density are model independently defined in the infinite momentum frame. Likewise, flavor decomposition of the nucleon form factors into dressed u and d quark form factors, may give information about the quark-diquark structure of the nucleon. The current proton radius “crisis” will also be discussed.
The form factors of the nucleons Perdrisat, C. F.
Physics of particles and nuclei,
11/2013, Letnik:
44, Številka:
6
Journal Article
Recenzirano
Odprti dostop
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing ...double-polarization experiments, in comparison with with previous unpolarized cross section data. Here we will review the experimental data base in view of the new results for the proton and the neutron, obtained at MIT-Bates, JLab and MAMI. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed. In particular, the possibility that the proton is non-spherical in its ground state, and that the transverse charge density are model independently defined in the infinite momentum frame. Likewise, flavor decomposition of the nucleon form factors into dressed
u
and
d
quark form factors, may give information about the quark-diquark structure of the nucleon. The current proton radius “crisis” will also be discussed.
The reaction p + CH2→ forward charge particle + X is used for this aim traditionally. Analyzing power of this reaction falls off as 1 p, where p is the laboratory momentum. At the proton momenta of ...order 8 GeV c, which are expected at the JLab experiment, the low analyzing power creates problems for off-line analysis of data. On the other hand, it is well known that the reaction p+p → p+p has the much more analyzing power. So, the calorimeter is predestinated for suppression of inelastic events in this reaction. In the report it is shown that the problem is solved quite well.
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