Darmstadt 2008 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 11: Instrumentation und Anwendungen I

HK 11.1: Group Report

Monday, March 10, 2008, 16:30–17:00, 2C

First Results from the HERMES Recoil Detector — •Sergey Yaschenko for the HERMES collaboration — Physikalisches Institut II, Universität Erlangen-Nürnberg

For the last one and a half years of operation of HERA, a Recoil Detector was installed at the HERMES experiment to improve measurements of hard exclusive electron/positron scattering reactions in particular deeply virtual Compton scattering. These measurements can provide important constraints on models for generalized parton distributions and hence can lead to the determination of the angular momentum of quarks inside the nucleon.

The HERMES Recoil Detector was designed to improve the selection of exclusive events by a direct measurement of the momentum and track direction of recoiling particles and allow the rejection of non-exclusive background events. The detector consisted of three main components: a silicon strip detector (SSD) placed inside the HERA vacuum, a scintillation fiber tracker (SFT), and a photon detector consisting of three layers of tungsten-scintillator sandwich. All the detectors were located in a solenoidal magnetic field of 1 Tesla.

The detector was installed in the HERMES experiment in December 2005. The commissioning of the SFT was finished in February 2006 and the SSD commissioning could only be finished in September 2006 due to beam induced noise. The fully commissioned Recoil detector was working stable from September 2006 to the end of HERA operation on June 30 of 2007. Results on the detector performance are presented.

This work is supported by BMBF (Contract No. 06 ER 143).