E. Eisenhandler

The H1 lead/scintillating-fibre calorimeter

Abstract The backward region of the H1 detector has been upgraded in order to provide improved measurement of the scattered electron in deep inelastic scattering events. The centerpiece of the upgrade is a high-resolution lead/scintillating-fibre calorimeter. The main design goals of the calorimeter are: good coverage of the region close to the beam pipe, high angular resolution and energy resolution of better than 2% for 30 GeV electrons. The calorimeter should be capable of providing coarse hadronic energy measurement and precise time information to suppress out-of-time background events at the first trigger level. It must be compact due to space restrictions. These requirements were fulfilled by constructing two separate calorimeter sections. The inner electromagnetic section is made of 0.5 mm scintillating plastic fibres embedded in a lead matrix. Its lead-to-fibre ratio is 2.3:1 by volume. The outer hadronic section consists of 1.0 mm diameter fibres with a lead-to-fibre ratio of 3.4:1. The mechanical construction of the new calorimeter and its assembly in the H1 detector are described.

The ATLAS Level-1 Calorimeter Trigger

The ATLAS Level-1 Calorimeter Trigger uses reduced-granularity information from all the ATLAS calorimeters to search for high transverse-energy electrons, photons, τ leptons and jets, as well as high missing and total transverse energy. The calorimeter trigger electronics has a fixed latency of about 1 μs, using programmable custom-built digital electronics. This paper describes the Calorimeter Trigger hardware, as installed in the ATLAS electronics cavern.

Measurement of differential cross sections for antiproton-proton annihilation into charged pion and kaon pairs between 0.79 and 243 GeV/c

Abstract Differential cross sections have been measured for the interactions p p → π − π + and p p → K − K + over a centre of mass angular range −0.95 ⩽ cos θ ∗ ⩽ 0.95 at 20 incident momenta between 0.79 and 2.43 GeV/ c . A magnetic spectrometer with wire spark chambers was used. Typically 2000 π − π + and 300 K − K + events were obtained at each momentum. Results are compared with those from related experiments.

Performance of an electromagnetic lead/scintillating-fibre calorimeter for the H1 detector

Abstract The properties of final modules of a high resolution lead/scintillating-fibre calorimeter to upgrade the backward region of the H1 detector were studied with electrons in the energy range from 2–60 GeV. The electromagnetic calorimeter consists of scintillating fibres with a diameter of 0.5 mm embedded in a lead matrix. This small fibre radius, in combination with a lead-to-fibre ratio of 2.27:1, ensures excellent energy resolution which has been measured to be δ/E=7.1%/ E/GeV ⊕ 1.0% . The spatial resolution as a function of energy for impact points at the center of a cell is given by 4.4 mm/ E/GeV + 1.0 mm . The time resolution was found to be better than 0.4 ns.

Evidence for mesons with spins 3, 4 and 5 in pp → π−π+ in the mass region 2020 to 2580 MeV/c2

Abstract We present the results of an amplitude analysis of p p → π − π + , using differential cross sections and new polarisation results in the c.m. energy region between 2020 and 2580 MeV. There is strong evidence for resonances with spin 3, 4 and 5 at mass valuesof 2150, 2310 and 2480 MeV/c2 with widths between 200 and 280 MeV and quantum numbers JPCIG = 3−−1+, 4++0+, 5−−1+.

Differential cross sections for antiproton-proton elastic scattering between 0.69 and 2.34 GeV/c

Abstract Measurements have been made of the differential cross section for p p elastic scattering over a c.m. angular range −0.95 ⩽ cos θ ∗ ⩽ 0.93 at 21 incident antiproton momenta between 0.69 GeV/ c and 2.43 GeV/ c (c.m. energy 1.96–2.58 GeV). About 10 5 events were obtained at each momentum. The results are discussed primarily in terms of the formation of s -channel resonances in the T and U mass regions, and within the context of the optical model of Frahn and Venter.

Use of an FPGA to identify electromagnetic clusters and isolated hadrons in the ATLAS level-1 calorimeter trigger

Abstract At the full LHC design luminosity of 10 34 cm −2 s −1 , there will be approximately 10 9 proton–proton interactions per second. The ATLAS level-1 trigger is required to have an acceptance factor of ∼10 −3 . The calorimeter trigger covers the region | η |⩽5.0, and φ =0 to 2 π . The distribution of transverse energy over the trigger phase space is analysed to identify candidates for electrons/photons, isolated hadrons, QCD jets and non-interacting particles. The Cluster Processor of the level-1 calorimeter trigger is designed to identify transverse energy clusters associated with the first two of these. The algorithms based on the trigger tower energies which have been designed to identify such clusters, are described here. The algorithms are evaluated using an FPGA. The reasons for the choice of the actual FPGA being used are given. The performance of the FPGA has been fully simulated, and the expected latency has been shown to be within the limits of the time allocated to the cluster trigger. These results, together with the results of measurements made with real data into a fully configured FPGA, are presented and discussed.

Antiproton-proton total elastic cross sections in the T and U regions (0.69−2.43 GeV/c)

Abstract Antiproton-proton total elastic cross sections at 21 incident momenta in the range 0.69 to 2.43 GeV/c have been deduced by combining pp elastic differential cross sections over a c.m. angular range −0.95 ⩽ cos θ ∗ ⩽ 0.93 with forward elastic cross sections derived from recent real-part measurements and pp total cross sections. Two bumps are observed, at M 1 ⋍ 2.155 and M 2 ⋍ 2.345 GeV /c 2 , having widths of Г1 ∼ 0.135 and Г 2 ∼ 0.135 GeV /c 2 . Corresponding structures in other pp reaction channels are discussed.

The UA1 calorimeter trigger

Abstract We describe the design, construction and performance of the fast calorimeter trigger used in the UA1 experiment on the CERN p p collider. Calorimeter energy signals are digitized rapidly and used to trigger on possible electrons, hadronic jets, total transverse energy and missing transverse energy, with many possible options. We also describe the minimum-bias pretrigger, based on scintillator hodoscopes.

A uranium scintillator calorimeter with plastic-fibre readout

Abstract We have developed a method for reading out scintillator plates in a compact calorimeter using embedded wavelength-shifting fibres coupled to photomultipliers. A test calorimeter using this technique, with uranium plates as the passive medium, was placed in test beams of 1 to 80 GeV. Results on resolution, uniformity, and electron-pion discrimination are presented, as well as a discussion of compensation (the near-equality of electron and hadron responses).