D. Hasch

The Spin Structure of the Nucleon

This article reviews our present understanding of QCD spin physics: the proton spin puzzle and new developments aimed at understanding the transverse structure of the nucleon. Present experimental investigations of the nucleons internal spin structure, the theoretical interpretation of the different measurements, and the open questions and challenges for future investigation are discussed.

Transverse-momentum-dependent parton distribution/fragmentation functions at an electron-ion collider

Abstract.We present a summary of a recent workshop held at Duke University on Partonic Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon Interactions. The transverse-momentum-dependent parton distribution functions (TMDs), parton-to-hadron fragmentation functions, and multi-parton correlation functions, were discussed extensively at the Duke workshop. In this paper, we summarize first the theoretical issues concerning the study of partonic structure of hadrons at a future electron-ion collider (EIC) with emphasis on the TMDs. We then present simulation results on experimental studies of TMDs through measurements of single-spin asymmetries (SSA) from semi-inclusive deep inelastic scattering (SIDIS) processes with an EIC, and discuss the requirement of the detector for SIDIS measurements. The dynamics of parton correlations in the nucleon is further explored via a study of SSA in D (

The HERMES back drift chambers

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Design and performance of the large HERMES drift chambers

production at large transverse momenta with the aim of accessing the unexplored tri-gluon correlation functions. The workshop participants identified the SSA measurements in SIDIS as a golden program to study TMDs in both the sea and valence quark regions and to study the role of gluons, with the Sivers asymmetry measurements as examples. Such measurements will lead to major advancement in our understanding of TMDs in the valence quark region, and more importantly also allow for the investigation of TMDs in the unexplored sea quark region along with a study of their evolution.

Spin Physics: Session Summary

Abstract The tracking system of the HERMES spectrometer behind the bending magnet consists of two pairs of large planar 6-plane drift chambers. The design and performance of these chambers is described. This description comprises details on the mechanical and electronical design, information about the gas mixture used and its properties, results on alignment, calibration, resolution, and efficiencies, and a discussion of the experience gained through the first three years of operation.The tracking system of the HERMES spectrometer behind the bending magnet consists of two pairs of large planar 6-plane drift chambers. The design and performance of these chambers is described. This description comprises details on the mechanical and electronical design, information about the gas mixture used and its properties, results on alignment, calibration, resolution, and efficiencies, and a discussion of the experience gained through the first three years of operation.

Electron-Ion Collider: The next QCD frontier: Understanding the glue that binds us all

Abstract Big planar drift chambers built for the downstream tracking system of the HERMES spectrometer are described. Using the fast non-flammable gas mixture Ar/CO 2 /CF 4 (90/5/5) average spatial resolutions of about 180 μm per plane at efficiencies above 96% have been obtained from test run data analysis.

Electron-Ion Collider

Many spin physics experiments have been performed in recent years and many new exciting results have been reported at DIS 2007 [1], which will be highlighted in this summary. Also on the theory side many new results were reported, especially regarding transverse spin effects which are most challenging. Recent years have seen quite some unexpected developments concerning so-called TMDs, transverse momentum dependent parton distributions, and we can look forward to more such developments over the coming years. Therefore, this summary is very much a snapshot of the current status. This summary is split into three main parts. We start with longitudinal spin physics, most notably, experimental results on gluon polarization. We proceed with transverse spin, which is mainly focused on transverse spin asymmetries and the possible explanation in terms of TMDs. The third and last part is about exclusive processes and generalized parton distributions, which provide more detailed information about the spatial distribution of partons inside hadrons. This spatial distribution is often probed using spin asymmetries and recent developments have started to point to a connection between GPDs and TMDs. A very interesting development.