We report the first measurements of deep inelastic scattering spin-dependent azimuthal asymmetries in back-to-back dihadron electroproduction in the deep inelastic scattering process. In this ...reaction, two hadrons are produced in opposite hemispheres along the z axis in the virtual photon-target nucleon center-of-mass frame, with the first hadron produced in the current-fragmentation region and the second in the target-fragmentation region. The data were taken with longitudinally polarized electron beams of 10.2 and 10.6 GeV incident on an unpolarized liquid-hydrogen target using the CLAS12 spectrometer at Jefferson Lab. Observed nonzero sinΔϕ modulations in ep→e^{'}pπ^{+}X events, where Δϕ is the difference of the azimuthal angles of the proton and pion in the virtual photon and target nucleon center-of-mass frame, indicate that correlations between the spin and transverse momenta of hadrons produced in the target- and current-fragmentation regions may be significant. The measured beam-spin asymmetries provide a first access in dihadron production to a previously unexplored leading-twist spin- and transverse-momentum-dependent fracture function. The fracture functions describe the hadronization of the target remnant after the hard scattering of a virtual photon off a quark in the target particle and provide a new avenue for studying nucleonic structure and hadronization.
We report results of Λ hyperon production in semi-inclusive deep-inelastic scattering off deuterium, carbon, iron, and lead targets obtained with the CLAS detector and the Continuous Electron Beam ...Accelerator Facility 5.014 GeV electron beam. These results represent the first measurements of the Λ multiplicity ratio and transverse momentum broadening as a function of the energy fraction (z) in the current and target fragmentation regions. The multiplicity ratio exhibits a strong suppression at high z and an enhancement at low z. The measured transverse momentum broadening is an order of magnitude greater than that seen for light mesons. This indicates that the propagating entity interacts very strongly with the nuclear medium, which suggests that propagation of diquark configurations in the nuclear medium takes place at least part of the time, even at high z. The trends of these results are qualitatively described by the Giessen Boltzmann-Uehling-Uhlenbeck transport model, particularly for the multiplicity ratios. These observations will potentially open a new era of studies of the structure of the nucleon as well as of strange baryons.
The EIC Comprehensive Chromodynamics Experiment (ECCE) detector has been designed to address the full scope of the proposed Electron Ion Collider (EIC) physics program as presented by the National ...Academy of Science and provide a deeper understanding of the quark-gluon structure of matter. To accomplish this, the ECCE detector offers nearly acceptance and energy coverage along with excellent tracking and particle identification. The ECCE detector was designed to be built within the budget envelope set out by the EIC project while simultaneously managing cost and schedule risks. This detector concept has been selected to be the basis for the EIC project detector.
The COmpact detectoR for the Eic (CORE) Proposal was submitted to the EIC "Call for Collaboration Proposals for Detectors". CORE comprehensively covers the physics scope of the EIC Community White ...Paper and the National Academies of Science 2018 report. The design exploits advances in detector precision and granularity to minimize size. The central detector includes a 3Tesla, 2.5m solenoid. Tracking is primarily silicon. Electromagnetic calorimetry is based on the high performance crystals. Ring-imaging Cherenkov detectors provide hadronic particle identification.
This article presents a collection of simulation studies using the ECCE detector concept in the context of the EIC's exclusive, diffractive, and tagging physics program, which aims to further explore ...the rich quark-gluon structure of nucleons and nuclei. To successfully execute the program, ECCE proposed to utilize the detecter system close to the beamline to ensure exclusivity and tag ion beam/fragments for a particular reaction of interest. Preliminary studies confirmed the proposed technology and design satisfy the requirements. The projected physics impact results are based on the projected detector performance from the simulation at 10 or 100 fb^-1 of integrated luminosity. Additionally, a few insights on the potential 2nd Interaction Region can (IR) were also documented which could serve as a guidepost for the future development of a second EIC detector.
Deeply virtual Compton scattering (DVCS) allows one to probe Generalized Parton Distributions (GPDs) describing the 3D structure of the nucleon. We report the first measurement of the DVCS beam-spin ...asymmetry using the CLAS12 spectrometer with a 10.2 and 10.6 GeV electron beam scattering from unpolarised protons. The results greatly extend the \(Q^2\) and Bjorken-\(x\) phase space beyond the existing data in the valence region and provide over 2000 new data points measured with unprecedented statistical uncertainty, setting new, tight constraints for future phenomenological studies.
A multidimensional extraction of the structure function ratio
$\sigma_{LT'}/\sigma_{0}$ from the hard exclusive $\vec{e} p \to e^\prime n
\pi^+$ reaction above the resonance region has been ...performed. The study was
done based on beam-spin asymmetry measurements using a 10.6 GeV incident
electron beam on a liquid-hydrogen target and the CLAS12 spectrometer at
Jefferson Lab. The measurements focus on the very forward regime ($t/Q^{2}$
$\ll$ 1) with a wide kinematic range of $x_{B}$ in the valence regime (0.17 $<$
$x_{B}$ $<$ 0.55), and virtualities $Q^{2}$ ranging from 1.5 GeV$^{2}$ up to 6
GeV$^{2}$. The results and their comparison to theoretical models based on
Generalized Parton Distributions demonstrate the sensitivity to chiral-odd GPDs
and the directly related tensor charge of the nucleon. In addition, the data is
compared to an extension of a Regge formalism at high photon virtualities. It
was found that the Regge model provides a better description at low $Q^{2}$,
while the GPD model is more appropriate at high $Q^{2}$.
We present the first measurement of di-hadron angular correlations in electron-nucleus scattering. The data were taken with the CLAS detector and a 5.0 GeV electron beam incident on deuterium, ...carbon, iron, and lead targets. Relative to deuterium, the nuclear yields of charged-pion pairs show a strong suppression for azimuthally opposite pairs, no suppression for azimuthally nearby pairs, and an enhancement of pairs with large invariant mass. These effects grow with increased nuclear size. The data are qualitatively described by the GiBUU model, which suggests that hadrons form near the nuclear surface and undergo multiple-scattering in nuclei. These results show that angular correlation studies can open a new way to elucidate how hadrons form and interact inside nuclei
We report results of $\Lambda$ hyperon production in semi-inclusive
deep-inelastic scattering off deuterium, carbon, iron, and lead targets
obtained with the CLAS detector and the Continuous Electron ...Beam Accelerator
Facility 5.014~GeV electron beam. These results represent the first
measurements of the $\Lambda$ multiplicity ratio and transverse momentum
broadening as a function of the energy fraction~($z$) in the current and target
fragmentation regions. The multiplicity ratio exhibits a strong suppression at
high~$z$~and~an enhancement at~low~$z$. The measured transverse momentum
broadening is an order of magnitude greater than that seen for light mesons.
This indicates that the propagating entity interacts very strongly with the
nuclear medium, which suggests that propagation of diquark configurations in
the nuclear medium takes place at least part of the time, even at high~$z$. The
trends of these results are qualitatively described by the Giessen
Boltzmann-Uehling-Uhlenbeck transport model, particularly for the multiplicity
ratios. These observations will potentially open a new era of studies of the
structure of the nucleon as well as of strange baryons.
Several factors can contribute to the difficulty of aligning the sensors of tracking detectors, including a large number of modules, multiple types of detector technologies, and non-linear strip ...patterns on the sensors. All three of these factors apply to the CLAS12 CVT, which is a hybrid detector consisting of planar silicon sensors with non-parallel strips, and cylindrical micromegas sensors with longitudinal and arc-shaped strips located within a 5~T superconducting solenoid. To align this detector, we used the Kalman Alignment Algorithm, which accounts for correlations between the alignment parameters without requiring the time-consuming inversion of large matrices. This is the first time that this algorithm has been adapted for use with hybrid technologies, non-parallel strips, and curved sensors. We present the results for the first alignment of the CLAS12 CVT using straight tracks from cosmic rays and from a target with the magnetic field turned off. After running this procedure, we achieved alignment at the level of 10~\(\mu\)m, and the widths of the residual spectra were greatly reduced. These results attest to the flexibility of this algorithm and its applicability to future use in the CLAS12 CVT and other hybrid or curved trackers, such as those proposed for the future Electron-Ion Collider.
