121603383
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.
17193732
JET PRODUCTION AT HERA : PROGRESS AND PROBLEMS
This contribution reviews the measurements related to jet production at HERA which are available in`98. The reasons for the considerable progress achieved in the last years are summarized. The major diiculties and the limitations of these measurements as seen today are discussed. 1. What has been measured ? One of the many fascinating topics of research at the electron{proton collider HERA is the study of multi{jet events. The application of jet algorithms to characterize the properties of multi{particle hadronic nal states turned out to be a powerful and natural approach. Jet algorithms have been used intensively in the analysis of deeply inelastic scattering (DIS) and photoproduction processes. In leading{order QCD, the cross section of multi{jet events in DIS is proportional to the strong coupling constant s and the parton density functions of the proton. Several determinations of s based on jets have been performed at HERA 1, 2, 3, 4]. There are (preliminary) extractions of the proton's gluon content in NLO 5]. This approach is more direct than determinations of the gluon density from inclusive structure function measurements, and it probes the gluon density at larger momentum fractions. Events with a jet in the very forward (proton) direction of the detectors have been studied in attempts to search for signatures expected when the BFKL parton density evolution equations are valid at HERA 6]. In photoproduction, evidence for the partonic structure of the photon has been shown in studies of jet distributions 7]. In events with two reconstructed jets x , the share of the photon's momentum entering the hard scattering process, can be calculated. From the measurement of dijet cross sections diierential in x and transverse jet energy, photon parton densities could be constrained, and the p t dependence of the anomalous component of the real photon predicted by QCD could be connrmed 8]. Jet polar angle distributions for direct and resolved photons where measured to be sensitive to the spin of the corresponding gluon or quark propagators 9]. Also, LO eeective parton densities were extracted 8].
119863129
Performance of the H1 lead/scintillating-fibre calorimeter
Abstract In the winter-shutdown 1994/95 the backward region of the H1 detector has been equipped with a new lead/scintillating-fibre calorimeter. The purpose of the calorimeter is to perform precise measurements of the energy and the position of scattered electrons in ep collisions at HERA. In addition, the calorimeter determines the hadronic energy flow in the backward region and provides detailed trigger information and efficient background rejection exploiting the difference of impact times for physics events and beam related background events. The first data-taking experience with the new device is described.
7496605
Serial Powering for Silicon Strip Detectors at SLUC
Serial powering of silicon sensors is a novel powering scheme that would reduce the total power, the number of cables, the passive detector material, and the costs of future silicon trackers by large factors. Modules are chained in series and are served by a single current source. Serial powering is of great interest for future large-scale silicon tracking detectors for particle physics with many thousands of densely packed detector modules. Tests with six ATLAS semiconductor tracker (SCT) modules using both serial powering and the conventional independent powering have been carried out. The electrical performance of SCT modules powered in series is excellent. We present selected results and discuss the system aspects of a serial powering.
110237207
Evaluation of MCM-D technology for silicon strip detectors
Abstract Multi-chip Modules-Deposited (MCM-D) is a technology that can be applied to silicon strip modules and promises advantages in terms of integration complexity and material budget. This technology permits to integrate the front-end hybrid, pitch adaptor and wire bonds on the silicon sensor. The principle is to deposit alternating dielectric and metal layers directly on the silicon, where traces and vias are etched with high resolution to produce a PCB like structure. This paper reports on a prototype MCM-D processing run of silicon strip wafers performed to evaluate suitability of the technology. This first run uses one dielectric layer, one metal layer, passivation and a final metallisation appropriate for wire-bonding. Connections are done through the first dielectric layer to the strips, the bias ring, bias resistors and guard rings. Hence the effects of the post-processing on the silicon sensor are evaluated measuring change in parameters such as I / V and C / V characteristics, inter-strip capacitance and resistance.
73602518
Radiation Resistant DC- DC Power Conversion with Voltage Ratios > 10 Capable of Operating in High Magnetic Field for LHC Upgrade Detectors
Commercial power converters that have voltage ratios greater than ten and are capable of running near the LHC collision region would increase the efficiency of the power distribution system of the ATLAS Silicon Tracker high luminosity upgrade. The devices must operate in a high magnetic field (2 T) and be radiation hard to ~50-100 Mrad and ~10 15 Neq/cm 2 . These converters are to be mounted on the same multi-chip modules as the ASIC readout chips or in close vicinity without introducing any additional readout noise due to the high switching frequencies. Such devices will permit higher voltage power delivery to the tracker and thus increase overall power efficiency by limiting the ohmic losses in the stretch of cable (about 100 meters) between the tracker and the power sources.
119401854
Charge transfer and charge broadening of GEM structures in high magnetic fields
Abstract We report on the measurements of charge transfer in Gas Electron Multipliers (GEM) structures in high magnetic fields. These were performed in the framework of the R&D work for a Time Projection Chamber at a future Linear Collider. A small test chamber has been installed in the aperture of a superconducting magnet with the GEM structures mounted perpendicular to the B -field direction. The charge transfer is derived from the electrical currents monitored during irradiation with an 55 Fe source. No significant loss of primary ionisation charge is observed, and an improved ion feedback suppression is achieved for high magnetic fields. Additionally, the width of the charge cloud released by individual 55 Fe photons is measured using a finely segmented strip readout after the triple GEM structure. Charge widths between 0.3 and 0.5 mm RMS are observed, which originate from the charge broadening inside the GEM amplification. This charge broadening is only partly suppressed at high magnetic fields.
122225376
An investigation of the antinuclei and nuclei production mechanism in Pb + Pb collisions at 158 A GeV
We investigate the production mechanisms of p, d, t, 3He, 4He, 6Li, , and in Pb+Pb collisions at 158 A GeV measured near zero transverse momentum with the NA52 experiment at the CERN SPS. We find evidence that nuclei and antinuclei in Pb+Pb collisions are mainly produced via the coalescence mechanism out of a thermalized source of hadrons, at a time close to the thermal freeze-out of hadrons corresponding to a temperature of ~120 MeV.
123173797
Calibration, alignment and tracking performance of the CMS silicon strip tracker
Abstract After its installation in the CMS experiment, the CMS silicon tracker has been commissioned, calibrated and aligned based on several million reconstructed tracks, recorded during extended cosmic ray data-taking in 2008 and 2009. The collision data at 900 GeV and 2.36 TeV which were recorded by the CMS experiment in December 2009 allowed to repeat the calibration measurements and derive compatible results. Calibration results are shown for the silicon strip detector only, whereas alignment and tracking performance are given for the complete CMS tracker, including the silicon pixel system.
119389130
Electroweak corrections to e+ e- -> nu anti-nu H and e+ e- -> t anti-t H
The most interesting Higgs-production processes at future e+ e- colliders belong to the process class e+ e- ->f anti-f H. We study the full O(alpha) corrections to this reaction in the Standard Model for neutrinos and top quarks in the final state. Leading higher-order corrections from initial-state radiation and QCD corrections are also taken into account. Although cancellations between the different kinds of corrections occur, the full corrections are of the order of +/-10% and thus important ingredients in the theoretical predictions for future e+ e- colliders.
123205836
The E760 lead-glass central calorimeter: design and initial test results
The central calorimeter in Fermilab experiment E760++ has been designed to measure the topology and energies of electrons and photons in the decay of charmonium formed in pp annihilation. The calorimeter is composed of 1280 lead-glass Cherenkov counters read out with photomultiplier tubes. This paper discusses design criteria for the calorimeter and describes how these criteria were met. Data from tests in low energy (10–84 MeV) and medium energy (1–4 GeV) beams are presented showing a spatial resolution of 9 mm, an energy resolution of (3.0 ± 0.3)%√E[GeV] + (1.5 ± 0.5)%, and an effective energy threshold below 10 MeV.