High Resolution Bubble Chambers Research Articles

The European hybrid spectrometer

The final version of the European hybrid spectrometer (EHS) is described. EHS was used in the NA27 experiment to study charm particles produced in 360 GeV c π − p and 400 GeV c pp interactions. A rapid cycling, high resolution bubble chamber (LEBC) produced bubbles of 17 μm diameter which were measured with a precision of 2.5 μm. Short-lived charm particles are observed with an efficiency up to 90% (D ±). The spectrometer accepts 70% of all particles produced, including approximately 100% of those in the forward hemisphere and the momenta of charged particles are measured to better than 1% over the whole momentum range. The charged particle identification detectors give information on 84% of the spectrometer tracks, half of which obtain unique identification. Two lead glass detectors measure the energy of electromagnetic showers such that the π 0 mass distribution has a fwhm of 20 MeV c 2 . Hadronic showers are measured with two iron/scintillator calorimeters. The mass resolutions are 3.0, 0.9 and 11 MeV c 2 for K 0, Λ 0 and D − charged particles respectively. The D 0 mass is measured to be (1865.1 ± 1.8 ± 0.8) MeV c 2 .

Inclusive charm cross sections in 800 GeV/ c p-p interactions

We report a measurement of the inclusive D/D̄ production cross section in 800 GeV/ c proton-proton interactions. The experiment used the high resolution bubble chamber LEBC exposed to an 800 GeV/ c proton beam at the Fermilab MPS. We obtain σ( D/ D ̄ )=59 −15 +22μ b (statistical errors), having analysed 25% of the total data sample. Comparison with 400 GeV/ c pp dat a obtained with LEBC at CERN shows a D/D̄ cross section increase by a factor of 1.7 −0.5 +0.7. This is in good agreement with fusion model calculations.

Conceptual design for a high resolution high rate vertex detector for charm and beauty experiments using scintillating fibre optics

A vertex detector is proposed for charm and beauty experiments using a simple arrangement of scintillating optical fibres to provide high resolution (∼10 μm) in a plane transverse to the event axis. Experience with the high resolution bubble chambers shows that this is optimal for the detection of heavy flavour decays in complex events. The aim is to provide a high rate triggerable charm/beauty track and vertex detector for fixed target or collider experiments.

A camera shutter used in high resolution bubble chamber photography

A cylindrical rotating shutter for a high resolution bubble chamber camera is described. It eliminates several undesirable effects of interference from the low resolution photography system.