Zero Degree Calorimeters Research Articles

Particle emission following Coulomb excitation in ultrarelativistic heavy-ion collisions

We study nuclear reactions induced by virtual photons associated with Lorentz-boosted Coulomb fields of ultrarelativistic heavy ions. Evaporation, fission, and multifragmentation mechanisms are included in a new RELDIS code, which describes the deexcitation of residual nuclei formed after single and double photon absorption in peripheral heavy-ion collisions. Partial cross sections for different dissociation channels, including the multiple neutron emission ones, are calculated and compared with data when available. Rapidity and transverse momentum distributions of nucleons, nuclear fragments, and pions, produced electromagnetically, are also calculated. These results provide important information for designing large-rapidity detectors and zero-degree calorimeters at the relativistic heavy-ion colliders. The electromagnetic dissociation of nuclei imposes some constraints on the investigation of exotic particle production in $\ensuremath{\gamma}\ensuremath{\gamma}$ fusion reactions.

Observation of fission in Pb-Pb interactions at158A GeV

The NA50 experiment at the CERN SPS has been equipped with a Cerenkov quartz detector to measure the charge of projectilelike fragments emitted in interactions of the lead beam of $158A \mathrm{GeV}$ with a 12 mm thick lead target. A clear fission peak has been observed in the light output distribution of the fragment detector and the measured number of fission events per incident Pb ion is $(1.26\ifmmode\pm\else\textpm\fi{}0.16)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}.$ The information provided by the NA50 zero-degree calorimeter has allowed us to check that fission occurs in extremely peripheral collisions. To provide the first information about the fission mechanism, the expected yield of electromagnetic fission events in our experimental conditions has been computed: it turns out to be about $40%$ smaller than the observed one. The approximations necessarily made in our calculation as well as the contribution due to fission induced by nuclear interaction could account for such a difference.

A possible evidence of Coulomb fission in lead-lead collisions at the CERN SPS

The NA50 experiment at CERN SPS has been equipped with a quartz Cherenkov detector to measure the charge of projectile-like fragments emitted in interactions of the lead beam of 158 AGeV with a lead target. A fission peak has been observed in the light output distribution of the fragment detector. The information provided by the NA50 zero-degree calorimeter indicates that fission occurs in extremely peripheral collisions, compatible (within the resolution of the detector) with electromagnetic interaction. The expected yield of Coulomb fission events in our experimental condition has been evaluated and turns out to be about 40% smaller than the observed one.

The quartz-fiber Zero-Degree Calorimeter for the NA50 experiment at CERN SPS

Quartz-fiber calorimeters have been the object of an intense and fruitful work of research and development in the last few years. In this paper we report about the first application of this technique in an experiment. Namely, we describe the design and performance of the Zero-Degree Calorimeter (ZDC) used in NA50, a heavy-ion experiment at CERN SPS aiming to detect the formation of quark-gluon plasma in Pb–Pb collisions at 158 AGeV by studying the production of the charmonia states J/ψ and ψ′. The unique properties of the quartz-fiber calorimeters turn out to be well suited to match the specific requirements of this experiment that operates at beam intensity of about 10 7 Pb-ion/s: radiation hardness (up to a few Grads), short duration of the signal (∼10 ns), spatial resolution of a few hundreds of μm, small size of the detector (5×5×65 cm 3) and energy resolution adequate for providing a precise measurement of the collision centrality.

Quartz fiber ZDCs at CERN SPS and LHC

A quartz fiber zero degree calorimeter (ZDC) is operating in the NA50 experiment at CERN SPS since its first lead ion run in November 1994. This unusually small detector (5×5×65cm3) is a spaghetti calorimeter with quartz optical fibers embedded in tantalum slabs. The ZDC performances are presented with special emphasis on the 1996 lead ion run results. The plans for ALICE ZDCs at LHC are also presented.

The quartz-fiber calorimeters for the NA50 and ALICE experiments

Quartz-fiber calorimeters have been object of an intense and fruitful work of research and developement in the very last years. In this paper, together with the performance of the quartz-fiber zero-degree calorimeter used in the NA50 experiment at, CERN SPS, we also present the design of the quartz-fiber calorimeters for ALICE, the dedicated heavy-ion experiment at LHC.

A position sensitive highly radiation hard and fast hadron calorimeter for a lead ion experiment at CERN SPS

We present the performance of the Zero Degree Calorimeter (ZDC) built for the NA50 experiment at the CERN SPS. This detector measures the Cherenkov light produced in silica optical fibres embedded in tantalum and offers the double advantage of being highly radiation resistant (up to several Grad) and very fast (signal width of the order of 10 ns). It has an active volume of 5 × 5 × 65 cm 3 with a fibre to tantalum volume ratio of 1 17 ; the fibres are positioned at an angle of 0° with respect to the beam direction and have a diameter of 365 μm. The measured energy resolution ( σ E ) is 30% for protons at 205 GeV and 5% for lead ions at 160 GeV/nucleon. The detector exhibits also very good localising properties since it can detect the impact point of the lead beam on its front face with a precision better than 0.4 mm rms.

The zero-degree calorimeter for the relativistic heavy-ion experiment WA80 at CERN

Calibration and performance results are presented for a sampling calorimeter designed for use as a beam calorimeter at zero degrees in the relativistic heavy-ion experiment WA80 at CERN. This uranium-scintillator zero-degree calorimeter (ZDC) was found to have a linear response to heavy ions over the range 60–6400 GeV and an in-beam hadronic resolution ranging from σE = 0.013 + 0.33√E at low intensities to σE = 0.02 + 0.67√E at higher intensities. The eh ratio of the electromagnetic section was measured to be 1.12 at 135 GeV. The ZDC operated reliably with incident beams of 3.2 TeV oxygen and 6.4 TeV sulfur at intensities of over 106 nuclei per spill. It provided a trigger both for minimum bias events and for violent central collisions.

Event simulation for the WA80 experiment

The HIJET and LUND event generators are compared. It is concluded that for detector construction and design of experimental setups, the differences between the two models are marginal. The coverage of the WA80 setup in pseudorapidity and energy is demonstrated. The performance of some of the WA80 detectors (zero-degree calorimeter, wall calorimeter, multiplicity array, and SAPHIR lead-glass detector) is evaluated based on calculations with the LUND or the HIJET codes combined with codes simulating the detector responses.