User:Idastorehaug/European Hybrid Spectrometer

History
The proposal for CERN's European Hybrid Spectrometer (EHS) was accepted by the Super Proton Synchrotron Committee (SPSC) in 1976. It was installed at the Prévessin site of CERN, also known as the North Experimental Area, in 1977. It consisted of a Rapid Cycling Bubble Chamber as the target and a series of particle detectors which extended the experiment around and behind the bubble chamber. EHS aimed to integrate the technologies of bubble chambers and spectrometers in such a way as to maximize the advantages of each technique and minimize the inconveniences. The EHS was built by several European research groups. Rutherford Appleton Laboratory constructed the bubble chamber, Saclay its magnet and the CERN Experimental Physic Facilities and CERN Data Handling divisions were responsible for the project coordination and for the computers. Dutch and Austrian research groups built some of the particle detectors. The experiment stopped running in 1989, and publications of results from the experiments at EHS continued until 1992.

Experimental objective
The main aim of constructing an experimental arrangement which minimizes the systematic effects in the study of complex hadronic final states, it was proposed in 1974 to build a system of particle detectors around a high-energy beam at the CERN Super Proton Synchrotron (SPS). This system offered a possibility of determining, with all details, the dynamical features of strong particle interactions and associated weak decays.

The setup was designed to have a large geometrical acceptance and good particle identification as well as being flexible enough to adjust its field of view to the observation of unexpected new phenomena. Different targets and vertex detectors was coupled with a downstream with large geometrical acceptance, good momentum resolution and charged and neutral particle identification in a wide momentum range. In particular, Strange particle production was to be studied in detail at a beam momentum of 200GeV/c, using the rapid bubble chamber (RCBC) with about 1m fiducial length as vertex detector.

The beam source for EHS was a H2 beam from SPS. The spectrometer accepted 70% of all particles produced and the momenta of charged particles was measured to better than 1% over the whole momentum range. Two lead glass detector measured the energy of electromagnetic shower. Hadronic shower was measured with two iron/scintillator calorimeters.

Major components and detectors
EHS was a general facility, a detector to be used by several divisions and teams like Gargamelle, Omega, BEBC, 2m Bubble Chamber - an interdivisional collaboration with Experimental Physics Facilities (EF) and Data Handling (DD) division. The Rapid Cycling Bubble Chamber (RCBC) and was one of the vertex detectors in EHS. In 1984 EHS was operated with the LExan Bubble Chamber (LEBC), sometimes also referred to as HOLEBC, HO standing for High Optical resolution (Holographic). In 1985 many of the former EHS spectrometer's detectors, but not ISIS (Identification of Secondaries by Ionization Sampling) and SAD (Silica Aerogel Detector), were rearranged to install a new experiment, NA36.][5] [LEBC: bubble chamber, SAD, FC: Cherenkov counter, M1.M2; spectrometer magnets, IGD, FGD: lead glass calorimeter, U1-U3, W2: prop. Wire chamber. INC, FNC: iron hadron calorimeter, D1_D6: drift chamber, TRD: transition radiation detector, ISIS ionization sampling drift chamber.][8]

Experiments undertaken
LEBC-EHS was a very successful combination of the bubble chamber and electronic detector technique for the direct observation and study of charm particles, in particular in decay of strange and charm particles. LEBC-EHS provided the first reliable determinations of fundamental quantities in charm physics, like the life time of the D0, D+ and D- mesons and the charm cross section in hadronic production.
 * NA27: It was one of the most complex bubble chamber experiment ever made and the last one in the series of experiment using the EHS to analyze the secondary particles produced in high energy hadron collision. It studied the Charm particles produced in π-p and pp interactions using LEBS-EHS assembly.
 * NA16: Study of the hadronic production and properties of new particles with a lifetime 10-13 s < τ < 10-10 s using LEBC-EHS
 * NA22: Studied the hadronic interaction.
 * NA 23: Study of diffractive dissociation especially into strange and charmed particles with EHS.