(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Exclusive electroproduction of ... mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region ...of ... GeV..., 3.0 GeV ... 6.3 GeV, and ... GeV... Results on the angular distribution of the ... meson, including its decay products, are presented. The data were accumulated with the HERMES forward spectrometer during the 1996-2007 running period using the 27.6 GeV longitudinally polarized electron or positron beam of HERA. The determination of the virtual-photon longitudinal-to-transverse cross-section ratio reveals that a considerable part of the cross section arises from transversely polarized photons. Spin density matrix elements are presented in projections of ... or ... Violation of ...-channel helicity conservation is observed for some of these elements. A sizable contribution from unnatural-parity-exchange amplitudes is found and the phase shift between those amplitudes that describe transverse ... production by longitudinal and transverse virtual photons, ... and ..., is determined for the first time. A hierarchy of helicity amplitudes is established, which mainly means that the unnatural-parity-exchange amplitude describing the ... transition dominates over the two natural-parity-exchange amplitudes describing the ... and ... transitions, with the latter two being of similar magnitude. Good agreement is found between the HERMES proton data and results of a pQCD-inspired phenomenological model that includes pion-pole contributions, which are of unnatural parity.
Exclusive rho super(0)-meson electroproduction is studied in the HERMES experiment, using a 27.6 GeV longitudinally polarized electron/positron beam and unpolarized hydrogen and deuterium targets in ...the kinematic region 0.5 GeV super(2)<Q super(2)<7.0 GeV super(2), 3.0 GeV <W<6.3 GeV, and -t'<0.4 GeV super(2). Real and imaginary parts of the ratios of the natural-parity-exchange helicity amplitudes T sub(11) ( $\gamma*}_{T} \rightarrow\rho_{T}$ ), T sub(01) ( $\gamma*}_{T} \rightarrow \rho_{L}$ ), T sub(10) ( $\gamma*}_{L} \rightarrow\rho_{T}$ ), and T sub(1-1) ( $\gamma*}_{-T} \rightarrow\rho_{T}$ ) to T sub(00) ( $\gamma*}_{L}\rightarrow\rho_{L}$ ) are extracted from the data. For the unnatural-parity-exchange amplitude U sub(11), the ratio |U sub(11)/T sub(00)| is obtained. The Q super(2) and t' dependences of these ratios are presented and compared with perturbative QCD predictions.
Artificial Intelligence is poised to transform the design of complex,
large-scale detectors like the ePIC at the future Electron Ion Collider.
Featuring a central detector with additional detecting ...systems in the far
forward and far backward regions, the ePIC experiment incorporates numerous
design parameters and objectives, including performance, physics reach, and
cost, constrained by mechanical and geometric limits. This project aims to
develop a scalable, distributed AI-assisted detector design for the EIC
(AID(2)E), employing state-of-the-art multiobjective optimization to tackle
complex designs. Supported by the ePIC software stack and using Geant4
simulations, our approach benefits from transparent parameterization and
advanced AI features. The workflow leverages the PanDA and iDDS systems, used
in major experiments such as ATLAS at CERN LHC, the Rubin Observatory, and
sPHENIX at RHIC, to manage the compute intensive demands of ePIC detector
simulations. Tailored enhancements to the PanDA system focus on usability,
scalability, automation, and monitoring. Ultimately, this project aims to
establish a robust design capability, apply a distributed AI-assisted workflow
to the ePIC detector, and extend its applications to the design of the second
detector (Detector-2) in the EIC, as well as to calibration and alignment
tasks. Additionally, we are developing advanced data science tools to
efficiently navigate the complex, multidimensional trade-offs identified
through this optimization process.
We introduce a new phenomenological tool based on momentum region indicators to guide the analysis and interpretation of semi-inclusive deep-inelastic scattering measurements. The new tool, referred ...to as "affinity", is devised to help visualize and quantify the proximity of any experimental kinematic bin to a particular hadron production region, such as that associated with transverse momentum dependent factorization. We apply the affinity estimator to existing HERMES and COMPASS data and expected data from Jefferson Lab and the future Electron-Ion Collider. We also provide an interactive notebook based on Machine Learning for fast evaluation of affinity.
The beam-helicity asymmetry in associated electroproduction of real photons, ep arrow right e gamma pi N , in the Delta (1232)-resonance region is measured using the longitudinally polarized Hera ...positron beam and an unpolarized hydrogen target. Azimuthal Fourier amplitudes of this asymmetry are extracted separately for two channels, ep arrow right e gamma pi super(0) p and ep arrow right e gamma pi super(+) n, from a data set collected with a recoil detector. All asymmetry amplitudes are found to be consistent with zero.
We provide an overview of the status of Monte-Carlo event generators for high-energy particle physics. Guided by the experimental needs and requirements, we highlight areas of active development, and ...opportunities for future improvements. Particular emphasis is given to physics models and algorithms that are employed across a variety of experiments. These common themes in event generator development lead to a more comprehensive understanding of physics at the highest energies and intensities, and allow models to be tested against a wealth of data that have been accumulated over the past decades. A cohesive approach to event generator development will allow these models to be further improved and systematic uncertainties to be reduced, directly contributing to future experimental success. Event generators are part of a much larger ecosystem of computational tools. They typically involve a number of unknown model parameters that must be tuned to experimental data, while maintaining the integrity of the underlying physics models. Making both these data, and the analyses with which they have been obtained accessible to future users is an essential aspect of open science and data preservation. It ensures the consistency of physics models across a variety of experiments.
The beam-helicity asymmetry in associated electroproduction of real photons, eparrow righteγpiN , in the Delta(1232)-resonance region is measured using the longitudinally polarized Hera positron beam ...and an unpolarized hydrogen target. Azimuthal Fourier amplitudes of this asymmetry are extracted separately for two channels, eparrow righteγpi^sup 0^ p and eparrow righteγpi^sup +^ n, from a data set collected with a recoil detector. All asymmetry amplitudes are found to be consistent with zero.
The nuclear dependence of the inclusive inelastic electron scattering cross section (the EMC effect) has been measured for the first time in \(^{10}\)B and \(^{11}\)B. Previous measurements of the ...EMC effect in \(A \leq 12\) nuclei showed an unexpected nuclear dependence; \(^{10}\)B and \(^{11}\)B were measured to explore the EMC effect in this region in more detail. Results are presented for \(^9\)Be, \(^{10}\)B, \(^{11}\)B, and \(^{12}\)C at an incident beam energy of 10.6~GeV. The EMC effect in the boron isotopes was found to be similar to that for \(^9\)Be and \(^{12}\)C, yielding almost no nuclear dependence in the EMC effect in the range \(A=4-12\). This represents important, new data supporting the hypothesis that the EMC effect depends primarily on the local nuclear environment due to the cluster structure of these nuclei.
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