On the significance of radiative corrections on measurements of the EMC effect

Analyzing global data on the EMC effect, which denotes differences in parton distribution functions in nuclei compared to unbound nucleons, reveals tensions. Precise measurements at Jefferson Lab, studying both x and A dependence, show systematic discrepancies among experiments, making the extraction of the A dependence of the EMC effect sensitive to the selection of datasets. By comparing various methods and assumptions used to calculate radiative corrections, we have identified differences that, while not large, significantly impact the EMC ratios and show that using a consistent radiative correction procedure resolves this discrepancy, leading to a more coherent global picture, and allowing for a more robust extraction of the EMC effect for infinite nuclear matter.Comment: 9 pages, 12 figure

Modified Structure of Protons and Neutrons in Correlated Pairs

The atomic nucleus is made of protons and neutrons (nucleons), that arethemselves composed of quarks and gluons. Understanding how the quark-gluonstructure of a nucleon bound in an atomic nucleus is modified by thesurrounding nucleons is an outstanding challenge. Although evidence for suchmodification, known as the EMC effect, was first observed over 35 years ago,there is still no generally accepted explanation of its cause. Recentobservations suggest that the EMC effect is related to close-proximity ShortRange Correlated (SRC) nucleon pairs in nuclei. Here we report the firstsimultaneous, high-precision, measurements of the EMC effect and SRCabundances. We show that the EMC data can be explained by a universalmodification of the structure of nucleons in neutron-proton (np) SRC pairs andpresent the first data-driven extraction of this universal modificationfunction. This implies that, in heavier nuclei with many more neutrons thanprotons, each proton is more likely than each neutron to belong to an SRC pairand hence to have its quark structure distorted

Transmission of High-Power Electron Beams Through Small Apertures

Tests were performed to pass a 100 MeV, 430 kWatt c.w. electron beam from the energy-recovery linac at the Jefferson Laboratory's FEL facility through a set of small apertures in a 127 mm long aluminum block. Beam transmission losses of 3 p.p.m. through a 2 mm diameter aperture were maintained during a 7 hour continuous run.Comment: arXiv admin note: text overlap with arXiv:1305.019

Measured Radiation and Background Levels During Transmission of Megawatt Electron Beams Through Millimeter Apertures

We report measurements of photon and neutron radiation levels observed while transmitting a 0.43 MW electron beam through millimeter-sized apertures and during beam-off, but accelerating gradient RF-on, operation. These measurements were conducted at the Free-Electron Laser (FEL) facility of the Jefferson National Accelerator Laboratory (JLab) using a 100 MeV electron beam from an energy-recovery linear accelerator. The beam was directed successively through 6 mm, 4 mm, and 2 mm diameter apertures of length 127 mm in aluminum at a maximum current of 4.3 mA (430 kW beam power). This study was conducted to characterize radiation levels for experiments that need to operate in this environment, such as the proposed DarkLight Experiment. We find that sustained transmission of a 430 kW continuous-wave (CW) beam through a 2 mm aperture is feasible with manageable beam-related backgrounds. We also find that during beam-off, RF-on operation, multipactoring inside the niobium cavities of the accelerator cryomodules is the primary source of ambient radiation when the machine is tuned for 130 MeV operation.Comment: 9 pages, 11 figures, submitted to Nuclear Instruments and Methods in Physics Research Section

Developing a High Resolution ZDC for the EIC

The Electron Ion Collider offers the opportunity to make un-paralleled multidimen- sional measurements of the spin structure of the proton and nuclei, as well as a study of the onset of partonic saturation at small Bjorken-x [1]. An important requirement of the physics program is the tagging of spectator neutrons and the identification of forward photons. We propose to design and build a Zero Degree Calorimeter, or ZDC, to measure photons and neutrons with excellent energy & position resolution

Knowledge Base, Exporting Activities, Innovation Openness and Innovation Performance: A SEM Approach Towards a Unifying Framework

In this paper we demonstrate the complexity that regulates the innovation-exports nexus. In particular we argue that innovation and exports should be treated as latent variables in order to account for as many facets possible thus, accounting for multifaceted heterogeneity. In this context, the role of innovation openness ought to be highlighted within a unified framework, as it is considered an additional activity of firms' knowledge creation strategy. In this line, innovation and exporting orientation are ruled by the firms' strategic mix comprised of internal knowledge creation processes and the diversity of innovation openness. Theoretical and empirical links between these major components are identified and measured employing a Structural Equation Modelling (SEM) approach on a sample of Greek R&D-active manufacturing firms. Empirical findings corroborate the complexity of relationships and indicate that the firms' knowledge base and open innovation strategy regulate via complementary and substitution relationships firms' innovation and export performance