arXiv subjects

O. Rondon

Publications and source records attributed to O. Rondon.

At least 19 recordsLinked to original sources

arXiv2026

A New Low $Q^2$ Measurement of the Proton's $g_1$ Spin Structure Function from Longitudinal & Transverse Polarized Data

The proton's spin structure has proven to be far more complicated than was originally believed, and has been the subject of a number of experimental investigations. %Early measurements of the proton's spin structure function $g_1$ showed that the proton does not solely derive its spin from the spins of its quarks, starting the `proton spin crisis'. Of particular interest are the spin structure functions $g_1$ and $g_2$, which can be used to generate moments to directly compare experimental results to Chiral Perturbation Theory and other theories of Quantum Chromodynamics (QCD). The proton's $g_1$ structure function has been the subject of two other recent low momentum transfer experiments, but there are currently no published low momentum transfer measurements which collected data on the proton structure functions using both a longitudinally-polarized and a transversely-polarized target at the same kinematics. In this paper, we present the longitudinally polarized results of the Jefferson Lab E08-027 experiment, along with linked moments which combine this new result with the previously published transversely-polarized data from the same experiment. These results provide a proton $g_1$ extraction measured with very high precision across the resonance region, and provide new information on the value of $g_1$ dependent sum rules and moments.

nucl-ex↗

arXiv2022

The Proton Spin Structure Function $g_2$ and Generalized Polarizabilities in the Strong QCD Regime

The strong interaction is not well understood at low energy, or for interactions with low momentum transfer $Q^2$, but one of the clearest insights we have comes from Chiral Perturbation Theory ($χ$PT). This effective treatment gives testable predictions for the nucleonic generalized polarizabilities -- fundamental quantities describing the nucleon's response to an external field. We have measured the proton's generalized spin polarizabilities in the region where $χ$PT is expected to be valid. Our results include the first ever data for the transverse-longitudinal spin polarizability $δ_{LT}$, and also extend the coverage of the polarizability $\bar{d_2}$ to very low $Q^2$ for the first time. These results were extracted from moments of the structure function $g_2$, a quantity which characterizes the internal spin structure of the proton. Our experiment ran at Jefferson Lab using a polarized electron beam and a polarized solid ammonia (NH$_3$) target. The $δ_{LT}$ polarizability has remained a challenging quantity for $χ$PT to reproduce, despite its reduced sensitivity to higher resonance contributions; recent competing calculations still disagree with each other and also diverge from the measured neutron data at very low $Q^2$. Our proton results provide discriminating power between existing calculations, and will help provide a better understanding of this strong QCD regime.

nucl-ex↗

arXiv2021

Measurement of the EMC effect in light and heavy nuclei

Inclusive electron scattering from nuclear targets has been measured to extract the nuclear dependence of the inelastic cross section in Hall C at the Thomas Jefferson National Accelerator facility. Results are presented for 2H, 3He, 4He, 9B, 12C, 63Cu and 197Au at an incident electron beam energy of 5.77 GeV for a range of momentum transfer from Q^2 = 2 to 7 (GeV/c)^2. These data improve the precision of the existing measurements of the EMC effect in the nuclear targets at large x, and allow for more detailed examinations of the A dependence of the EMC effect.

nucl-ex↗

arXiv2019

Probing nucleon's spin structures with polarized Drell-Yan in the Fermilab SpinQuest experiment

Although the proton was discovered about 100 years ago, its spin structure still remains a mystery. Recent studies suggest that the orbital angular momentum of sea quarks could significantly contribute to the proton's spin. The SeaQuest experiment, which recently completed data collection, probed the unpolarized light quark sea distributions of the proton using the Drell-Yan process. Its successor, the SpinQuest (E1039), will access the $\bar{u}$ and $\bar{d}$ Sivers functions using polarized NH$_3$ and ND$_3$ targets. A non-zero Sivers asymmetry, observed in SpinQuest, would be a strong indication of non-zero sea-quark orbital angular momentum. The SpinQuest experiment can also probe the sea quark's transversity distribution, which is relevant for the determination of proton's tensor charge. Recent study suggests that sea-quarks might contribute significantly to deuteron's tensor polarized structure functions. This can be further probed in SpinQuest using tensor polarized ND$_3$ target. The current status and future plan of the experiment are presented.

nucl-ex↗

arXiv2018

Technical Supplement to "Polarization Transfer Observables in Elastic Electron-Proton Scattering at Q$^2$ = 2.5, 5.2, 6.8, and 8.5 GeV$^2$"

The GEp-III and GEp-2$γ$ experiments, carried out in Jefferson Lab's Hall C from 2007-2008, consisted of measurements of polarization transfer in elastic electron-proton scattering at momentum transfers of $Q^2 = 2.5, 5.2, 6.8,$ and $8.54$ GeV$^2$. These measurements were carried out to improve knowledge of the proton electromagnetic form factor ratio $R = μ_p G_E^p/G_M^p$ at large values of $Q^2$ and to search for effects beyond the Born approximation in polarization transfer observables at $Q^2 = 2.5$ GeV$^2$. The final results of both experiments were reported in a recent archival publication. A full reanalysis of the data from both experiments was carried out in order to reduce the systematic and, for the GEp-2$γ$ experiment, statistical uncertainties. This technical note provides additional details of the final analysis omitted from the main publication, including the final evaluation of the systematic uncertainties.

nucl-ex↗

arXiv2018

Polarization Transfer Observables in Elastic Electron Proton Scattering at $Q^2 = $2.5, 5.2, 6.8, and 8.5 GeV$^2$

The GEp-III and GEp-2$γ$ experiments were carried out in Jefferson Lab's (JLab's) Hall C from 2007-2008, to extend the knowledge of $G_E^p/G_M^p$ to the highest practically achievable $Q^2$ and to search for effects beyond the Born approximation in polarization transfer observables of elastic $\vec{e}p$ scattering. This article reports an expanded description of the common experimental apparatus and data analysis procedure, and the results of a final reanalysis of the data from both experiments, including the previously unpublished results of the full-acceptance data of the GEp-2$γ$ experiment. The Hall C High Momentum Spectrometer detected and measured the polarization of protons recoiling elastically from collisions of JLab's polarized electron beam with a liquid hydrogen target. A large-acceptance electromagnetic calorimeter detected the elastically scattered electrons in coincidence to suppress inelastic backgrounds. The final GEp-III data are largely unchanged relative to the originally published results. The statistical uncertainties of the final GEp-2$γ$ data are significantly reduced at $ε= 0.632$ and $0.783$ relative to the original publication. The decrease with $Q^2$ of $G_E^p/G_M^p$ continues to $Q^2 = 8.5$ GeV$^2$, but at a slowing rate relative to the approximately linear decrease observed in earlier Hall A measurements. At $Q^2 = 2.5$ GeV$^2$, the proton form factor ratio $G_E^p/G_M^p$ shows no statistically significant $ε$-dependence, as expected in the Born approximation. The ratio $P_\ell/P_\ell^{Born}$ of the longitudinal polarization transfer component to its Born value shows an enhancement of roughly 1.4\% at $ε= 0.783$ relative to $ε= 0.149$, with $\approx 1.9σ$ significance based on the total uncertainty, implying a similar effect in the transverse component $P_t$ that cancels in the ratio $R$.

nucl-ex↗

arXiv2016

JLab Measurements of the 3He Form Factors at Large Momentum Transfers

The charge and magnetic form factors, FC and FM, of 3He have been extracted in the kinematic range 25 fm-2 < Q2 < 61 fm-2 from elastic electron scattering by detecting 3He recoil nuclei and electrons in coincidence with the High Resolution Spectrometers of the Hall A Facility at Jefferson Lab. The measurements are indicative of a second diffraction minimum for the magnetic form factor, which was predicted in the Q2 range of this experiment, and of a continuing diffractive structure for the charge form factor. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the three-body nuclear problem.

nucl-ex↗

arXiv2013

JLab Measurement of the $^4$He Charge Form Factor at Large Momentum Transfers

The charge form factor of $^$4He has been extracted in the range 29 fm$^{-2}$ $\le Q^2 \le 77$ fm$^{-2}$ from elastic electron scattering, detecting $^4$He nuclei and electrons in coincidence with the High Resolution Spectrometers of the Hall A Facility of Jefferson Lab. The results are in qualitative agreement with realistic meson-nucleon theoretical calculations. The data have uncovered a second diffraction minimum, which was predicted in the $Q^2$ range of this experiment, and rule out conclusively long-standing predictions of dimensional scaling of high-energy amplitudes using quark counting.

nucl-ex↗

arXiv2013

Measurement of R = sigma_L / sigma_T and the Separated Longitudinal and Transverse Structure Functions in the Nucleon Resonance Region

We report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 < Q^2 < 5.5 GeV^2. The data have been used to accurately perform 167 Rosenbluth-type longitudinal / transverse separations. The precision R = sigma_L / sigma_T data are presented here, along with the first separate values of the inelastic structure functions F_1 and F_L in this regime. The resonance longitudinal component is found to be significant, both in magnitude and in the existence of defined mass peaks. Additionally, quark-hadron duality is here observed above Q^2 = 1 GeV^2 in the separated structure functions independently.

nucl-ex↗

arXiv2012

Polarization components in $π^{0}$ photoproduction at photon energies up to 5.6 GeV

We present new data for the polarization observables of the final state proton in the $^{1}H(\vecγ,\vec{p})π^{0}$ reaction. These data can be used to test predictions based on hadron helicity conservation (HHC) and perturbative QCD (pQCD). These data have both small statistical and systematic uncertainties, and were obtained with beam energies between 1.8 and 5.6 GeV and for $π^{0}$ scattering angles larger than 75$^{\circ}$ in center-of-mass (c.m.) frame. The data extend the polarization measurements data base for neutral pion photoproduction up to $E_γ=5.6 GeV$. The results show non-zero induced polarization above the resonance region. The polarization transfer components vary rapidly with the photon energy and $π^{0}$ scattering angle in c.m. frame. This indicates that HHC does not hold and that the pQCD limit is still not reached in the energy regime of this experiment.

nucl-ex↗

arXiv2012

New measurements of high-momentum nucleons and short-range structures in nuclei

We present new measurements of electron scattering from high-momentum nucleons in nuclei. These data allow an improved determination of the strength of two-nucleon correlations for several nuclei, including light nuclei where clustering effects can, for the first time, be examined. The data also include the kinematic region where three-nucleon correlations are expected to dominate.

nucl-ex↗

arXiv2011

Search for effects beyond the Born approximation in polarization transfer observables in $\vec{e}p$ elastic scattering

Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, $G_{E}/G_{M}$, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic $H(\vec{e},e'\vec{p})$ reaction for three different beam energies at a fixed squared momentum transfer $Q^2 = 2.5$ GeV$^2$, spanning a wide range of the virtual photon polarization parameter, $ε$. From these measured polarization observables, we have obtained separately the ratio $R$, which equals $μ_p G_{E}/G_{M}$ in the Born approximation, and the longitudinal polarization transfer component $P_\ell$, with statistical and systematic uncertainties of $ΔR \approx \pm 0.01 \mbox{(stat)} \pm 0.013 \mbox{(syst)}$ and $ΔP_\ell/P^{Born}_{\ell} \approx \pm 0.006 \mbox{(stat)}\pm 0.01 \mbox{(syst)}$. The ratio $R$ is found to be independent of $ε$ at the 1.5% level, while the $ε$ dependence of $P_\ell$ shows an enhancement of $(2.3 \pm 0.6) %$ relative to the Born approximation at large $ε$.

nucl-ex↗

arXiv2010

Measurements of the Electric Form Factor of the Neutron up to Q2=3.4 GeV2 using the Reaction He3(e,e'n)pp

The electric form factor of the neutron was determined from studies of the reaction He3(e,e'n)pp in quasi-elastic kinematics in Hall A at Jefferson Lab. Longitudinally polarized electrons were scattered off a polarized target in which the nuclear polarization was oriented perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons that were registered in a large-solid-angle detector. More than doubling the Q2-range over which it is known, we find GEn = 0.0225 +/- 0.0017 (stat) +/- 0.0024 (syst), 0.0200 +/- 0.0023 +/- 0.0018, and 0.0142 +/- 0.0019 +/- 0.0013 for Q2 = 1.72, 2.48, and 3.41 GeV2, respectively.

nucl-ex↗

arXiv2010

Scaling of the F_2 structure function in nuclei and quark distributions at x>1

We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for $x>1$, which is sensitive to short range contributions to the nuclear wave-function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the `super-fast' quarks probed at x>1. The falloff at x>1 is noticeably stronger in ^2H and ^3He, but nearly identical for all heavier nuclei.

nucl-ex↗

arXiv2010

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to Q^2 = 8.5 GeV^2

Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5 GeV2. By extending the range of Q2 for which GEp is accurately determined by more than 50%, these measurements will provide significant constraints on models of nucleon structure in the non-perturbative regime.

nucl-ex↗

arXiv2009

New measurements of the EMC effect in very light nuclei

New Jefferson Lab data are presented on the nuclear dependence of the inclusive cross section from 2H, 3He, 4He, 9Be and 12C for 0.3<x<0.9, Q^2 approximately 3-6 GeV^2. These data represent the first measurement of the EMC effect for 3He at large x and a significant improvement for 4He. The data do not support previous A-dependent or density-dependent fits to the EMC effect and suggest that the nuclear dependence of the quark distributions may depend on the local nuclear environment.

nucl-ex↗

arXiv2005

Nuclear transparency from quasielastic 12C(e,e'p)

We studied the reaction 12C(e,e'p) in quasielastic kinematics at momentum transfers between 0.6 and 1.8 (GeV/c)^2 covering the single-particle region. From this the nuclear transparency factors are extracted using two methods. The results are compared to theoretical predictions obtained using a generalization of Glauber theory described in this paper. Furthermore, the momentum distribution in the region of the 1s-state up to momenta of 300 MeV/c is obtained from the data and compared to the Correlated Basis Function theory and the Independent-Particle Shell model.

nucl-ex↗

arXiv2004

Correlated Strength in Nuclear Spectral Function

We have carried out an (e,e'p) experiment at high momentum transfer and in parallel kinematics to measure the strength of the nuclear spectral function S(k,E) at high nucleon momenta k and large removal energies E. This strength is related to the presence of short-range and tensor correlations, and was known hitherto only indirectly and with considerable uncertainty from the lack of strength in the independent-particle region. This experiment confirms by direct measurement the correlated strength predicted by theory.

nucl-ex↗