G. M. Levman

Construction and beam test of the ZEUS forward and rear calorimeter

Abstract The forward and rear calorimeters of the ZEUS experiment are made of 48 modules with maximum active dimensions of 4.6 m height, 0.2 m width, 7 λ depth and maximum weight of 12 t. It consists of 1 X 0 uranium plates interleaved with plastic scintillator tiles read out via wavelength shifters and photomultipliers. The mechanical construction, the achieved tolerances as well as the optical and electronics readout are described. Ten of these modules have been tested with electrons, hadrons and muons in the momentum range 15–100 GeV/ c . Results on resolution, uniformity and calibration are presented. Our main result is the achieved calibration accuracy of about 1% obtained by using the signal from the uranium radioactivity.

Performance of a Compensating Lead Scintillator Hadronic Calorimeter

Abstract We have built a sandwich calorimeter consisting of 10 mm thick lead plates and 2.5 mm thick scintillator sheets. The thickness ratio between lead and scintillator was optimized to achieve a good energy resolution for hadrons. We have exposed this calorimeter to electrons, hadrons and muons in the energy range between 3 and 75 GeV, obtaining an average energy resolution of 23% E for electrons and 44% E for hadrons. For energies above 10 GeV and after leakage corrections, the ratio of electron response to hardron response is 1.05.

How to measure the pion structure function at HERA

Abstract We suggest a method of determination of the pion structure function down to x ⋍ 10 −4 based on semi-exclusive deep inelastic scattering off protons. The idea is to exploit the nonperturbative πN and πΔ Fock components of the nucleon, which contribute significantly to deep inelastic scattering and dominate the fragmentation of protons into fast neutrons and deltas. The intrinsic factorization properties of the semi-exclusive cross section give a good test for the validity of this approach.

TEST OF THE ZEUS FORWARD CALORIMETER PROTOTYPE

Abstract Four prototype modules following the same design as the ZEUS forward calorimeter (FCAL) modules have been constructed and tested with electrons, hadrons and muons in the momentum range of 1 to 100 GeV/ c . The main topics under investigation were: calibration, uniformity of response, noise, light yield, energy resolution and the electron to hadron response (e/h ratio). The result of the measurements is presented and the expected performance of the FCAL is discussed in the light of these results.

Experimental study of uranium plastic scintillator calorimeters

Abstract As a preparation for the ZEUS high resolution calorimeter, sampling calorimeters made from 3.2 mm plates of depleted uranium read out by plastic scintillator of 3 mm and 5 mm thickness have been built. The response of hadrons, electrons and muons has been measured in the energy range between 3 and 100 GeV. In agreement with predictions, the relative response of electrons and hadrons as well as the hadronic energy resolution depend strongly on the thickness of the plastic scintillator. For 3.2 mm depleted uranium and 3 mm thick scintillator we observe over the full energy range equal response for electrons and hadrons; a hadronic energy resolution of 34.5% E[ GeV ] is obtained. Results are given for the spatial resolution for electrons and hadrons. Finally, results from a lead scintillator calorimeter built as a prestudy before uranium plates were available are reported.

Response of a uranium-scintillator calorimeter to electrons, pions and protons in the momentum range 0.5–10 GeV/c

Abstract We have exposed a sandwich calorimeter, consisting of 3.3 mm thick uranium pnterleaved with 2.6 mm thick scintillator tiles, to positive and negative electrons and pions and to protons in the momentum range of 0.5 to 10 GeV/c. We find that e/h is about 1 above 3 GeV/c, but decreases significantly for lower momenta. This ratio is the same for positive and negative pions and also for pions and protons of the same kinetic energy.

Test of a Forward Neutron Calorimeter for the ZEUS experiment at HERA

Abstract A Forward Neutron Calorimeter (FNC) for ZEUS is being constructed to detect high energy neutrons produced in the proton direction in ep collisions at HERA. To investigate the feasibility of such studies, a small iron-scintillator sandwich calorimeter was placed on the zero degree line 102 m downstream of the main ZEUS detector. The calorimeter was calibrated by studying proton beam-gas interactions during the HERA acceleration cycle. The design and construction of the calorimeter are described and the results of the test studies presented.

Influence of magnetic fields on the response of a uranium scintillator electromagnetic calorimeter

Abstract The response of a uranium scintillator sampling calorimeter to incident electrons and to the uranium radioactivity was measured in transverse magnetic fields up to 1.4T. The signal from electrons rises by as much as 9% due to the expected increase in light output of plastic scintillators in magnetic fields. For fields below 0.3 T the response to the uranium radioactivity tracks the electron signal to within about 0.5%. At higher fields it drops sharply, reaching −1.5% at 1.4 T. The consequences for the calibration of the ZEUS uranium scintillator calorimeter are discussed. We found no evidence for a change in the electromagnetic sampling fraction for fields below 0.3 T.

Measurements of longitudinal and transverse profiles for hadron showers in the range 10–100 GeV and comparisons with Monte Carlo simulations

Abstract Data on the longitudinal and transverse shower profiles initiated by 10, 20, 30, 50, 75, and 100 GeV positive hadron beams are presented. They have been measured with a 6λ deep sampling hadronic calorimeter using 3.2 mm thick depleted uranium plates as absorber and 3.0 mm scintillator layers as active material. The scintillator is read out with wavelength shifter plates coupled to photomultipliers. The data are compared to Monte Carlo calculations, simulating both the development of hadronic cascades as well as detector effects.