Atomic Hydrogen Gas Jet Target Research Articles

Polarization Measurements of p↑ and 3He↑ Beams at RHIC and Future EIC Using the Polarized Atomic Hydrogen Gas Jet Target

At the Relativistic Heavy Ion Collider (RHIC), the Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is employed for the precise measurement of the absolute transverse (vertical) polarization of proton beams, achieving low systematic uncertainties of approximately σPsyst/P≤0.5%. The acquired experimental data not only facilitated the determination of single AN(t) and double ANN(t) spin analyzing powers for 100 and 255 GeV proton beams, but also revealed a non-zero Pomeron spin-flip contribution through a Regge fit. Preliminary results obtained for forward inelastic p↑p and elastic p↑A analyzing powers will be discussed. The success of the HJET at RHIC suggests its potential application for proton beam polarimetry at the upcoming Electron–Ion Collider (EIC), aiming for an accuracy of 1%. Moreover, the provided analysis indicates that the RHIC HJET target can serve as a tool for the precision calibration, with the required accuracy, of the 3He beam polarization at the EIC.

Feasibility study for precisely measuring the EIC He3 beam polarization with the Polarized Atomic Hydrogen Gas Jet Target polarimeter at RHIC

The Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is used to measure the absolute proton beam polarization, $\sigma_P^\text{syst}/P\!\lesssim\!0.5\%$, at the Relativistic Heavy Ion Collider. Here I consider the possibility of employing HJET to measure the ${}^3\text{He}$ ($h$) beam polarization at the Electron-Ion Collider (EIC). The dominant contribution to the ratio of the $h^\uparrow{p}$ and $p^\uparrow{h}$ analyzing powers, which is needed for such measurements, can be easily calculated using well-known values of the proton and helion magnetic moments, but some corrections should be applied to achieve the required accuracy. It was found that corrections due to absorption and ${}^3\text{He}$ breakup effectively cancel in the ratio and a correction due to hadronic spin-flip amplitudes can be derived from the proton beam measurements. As a result, the anticipated systematic uncertainty in the measured ${}^3\text{He}$ beam polarization can satisfy the EIC requirement $\sigma_P^\text{syst}/P\!\lesssim\!1\%$.

Systematic error analysis in the absolute hydrogen gas jet polarimeter at RHIC

The Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is operated at the Relativistic Heavy Ion Collider (RHIC) since 2004 to measure the absolute polarization of each colliding proton beam. Polarimeter detectors and data acquisition were upgraded in 2015 to increase the solid angle, energy range, and to improve the energy and time resolution. These upgrades along with an improved beam intensity and polarization allowed us to greatly reduce the statistical and systematic errors for the proton polarization measurements in RHIC Runs15 (Ebeam=100GeV) and 17 (255GeV). For a typical 8 h RHIC store, the measured proton beam average polarization was about Pbeam∼55±2.0stat±0.3syst%. The elastic pp analyzing power, AN(t)∼0.04, was determined with a precision of about |δAN(t)|∼0.0002 in the momentum transfer squared range 0.001<−t<0.020GeV2. In this paper we present a detailed systematic error analysis of the polarization measurements at HJET. Perspectives of using the HJET based absolute polarimeters in the future Electron Ion Collider (EIC) will be also discussed.

Corrections to the elastic proton-proton analyzing power parametrization at high energies

The HJET Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) polarimeter was designed to measure the absolute polarization of the proton beams at the Relativistic Heavy Ion Collider. In these measurements, the small scattering angle elastic $pp$ single $A_N(t)$ and double $A_{NN}(t)$ spin analyzing powers can be precisely determined. The experimental accuracy achieved at HJET requires corrections to the $A_N(t)$ parametrization, conventionally used for such studies. In this paper we evaluate the corrections to the analyzing powers due to (i) the differences between the electromagnetic and hadronic form factors and (ii) the $m_p^2/s$ terms in the elastic spin-flip $pp$ electromagnetic amplitude. The corresponding alterations of the evaluated hadronic spin-flip amplitudes are about the same as the experimental uncertainties of the HJET measurements. The proposed corrections may have implications for the elastic $pp$ forward real-to-imaginary amplitude ratios $\rho$ determined in unpolarized $pp$ experiments.

Precision Small Scattering Angle Measurements of Elastic Proton-Proton Single and Double Spin Analyzing Powers at the RHIC Hydrogen Jet Polarimeter.

The Polarized Atomic Hydrogen Gas Jet Target polarimeter is employed by the Relativistic Heavy Ion Collider (RHIC) to measure the absolute polarization of each colliding proton beam. Polarimeter detectors and data acquisition were upgraded in 2015 to increase solid angle, energy range, and energy resolution. These upgrades and advanced systematic error analysis along with improved beam intensity and polarization in RHIC runs 2015 (E_{beam}=100 GeV) and 2017 (255GeV) allowed us to greatly reduce the statistical and systematic uncertainties for elastic spin asymmetries, A_{N}(t) and A_{NN}(t), in the Coulomb-nuclear interference momentum transfer range 0.0013<-t<0.018 GeV^{2}. For the first time hadronic single spin-flip r_{5} and double spin-flip r_{2} amplitude parameters were reliably isolated at these energies and momentum transfers. Measurements at two beam energies enable a separation of Pomeron and Regge pole contributions to r_{5}(s) and r_{2}(s), indicating that the spin component may persist at high energies.

Measurements of single and double spin asymmetry inppelastic scattering in the CNI region with a polarized atomic hydrogen gas jet target

Precise measurements of the single spin asymmetry ${A}_{N}$, and the double spin asymmetry ${A}_{NN}$, in proton-proton ($pp$) elastic scattering in the region of four-momentum transfer squared $0.001&lt;\ensuremath{-}t&lt;0.032\text{ }\text{ }(\mathrm{GeV}/c{)}^{2}$ have been performed using a polarized atomic hydrogen gas jet target and the Relativistic Heavy Ion Collider (RHIC) polarized proton beam. We present measurements of ${A}_{N}$ and ${A}_{NN}$ at center-of-mass energies $\sqrt{s}=6.8$ and 13.7 GeV. These spin-dependent observables are sensitive to the poorly known hadronic spin-dependent amplitudes. Comparing ${A}_{N}$ at different energies, a $\sqrt{s}$ dependence of the hadronic single spin-flip amplitude is suggested. A hadronic double spin-flip amplitude from the ${A}_{NN}$ data is consistent with zero within a 2-$\ensuremath{\sigma}$ level. We also present $\ensuremath{\Delta}{\ensuremath{\sigma}}_{T}$, estimated from the measured ${A}_{NN}$ data. The results for $\ensuremath{\Delta}{\ensuremath{\sigma}}_{T}$ are consistent with zero. Our results provide significant constraints toward a comprehensive understanding of the reaction mechanism for $pp$ elastic scattering.

Measurement of the analyzing power AN in pp elastic scattering in the CNI region with a polarized atomic hydrogen gas jet target

A precise measurement of the analyzing power A N in proton–proton elastic scattering in the region of 4-momentum transfer squared 0.001 < | t | < 0.032 ( GeV / c ) 2 has been performed using a polarized atomic hydrogen gas jet target and the 100 GeV/ c RHIC proton beam. The interference of the electromagnetic spin-flip amplitude with a hadronic spin-nonflip amplitude is predicted to generate a significant A N of 4–5%, peaking at − t ≃ 0.003 ( GeV / c ) 2 . This kinematic region is known as the Coulomb nuclear interference region. A possible hadronic spin-flip amplitude modifies this calculable prediction. We present the first precise result of the CNI asymmetry and shape as a function of t . Our data are well described by the CNI prediction with the electromagnetic spin-flip alone and do not support the presence of a large hadronic spin-flip amplitude.