HERMES is an experiment being conducted using the HERA particle accelerator

Hadron Elektron Ring Anlage

HERA was a particle accelerator at DESY in Hamburg. It began operating in 1992. At HERA, electrons or positrons were collided with protons at a center of mass energy of 318 GeV. It was the only lepton-proton collider in the world while operating...

 located at DESY

DESY

The DESY is the biggest German research center for particle physics, with sites in Hamburg and Zeuthen....

 in Hamburg

Hamburg

-History:The first historic name for the city was, according to Claudius Ptolemy's reports, Treva.But the city takes its modern name, Hamburg, from the first permanent building on the site, a castle whose construction was ordered by the Emperor Charlemagne in AD 808...

. The experiment's goal is to investigate the quark

Quark

A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly...

-gluon

Gluon

Gluons are elementary particles which act as the exchange particles for the color force between quarks, analogous to the exchange of photons in the electromagnetic force between two charged particles....

 structure of matter

Matter

Matter is a general term for the substance of which all physical objects consist. Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume...

 by examining how a nucleon's constituents affect its spin. HERMES completed its first run between 1995 and 2000, and a second run began in 2001 and is scheduled to end during the summer of 2007.

HERMES is being conducted by scientist

Scientist

A scientist in a broad sense is one engaging in a systematic activity to acquire knowledge. In a more restricted sense, a scientist is an individual who uses the scientific method. The person may be an expert in one or more areas of science. This article focuses on the more restricted use of the word...

s from more than 13 countries.

Method

Polarized electrons are fired at polarized gas targets. The virtual photon emitted by the electron is also polarized and so seeks out quarks of spin in the same direction as the photon. The asymmetry of ejected quarks is found to deduce the net polarisation of the quarks.

UGFS

The unpolarized gas feed system was used for non polarized "end of fill" or heavy target running before the polarized target was removed in 2003. Currently the UGFS supplies the target gasses in the new detector configuration.