M. A. Parker

Recent results of radiation damage studies in silicon

Abstract The RD2 Collaboration is making preliminary studies on a silicon tracking detector for use at the LHC. It is a priority that this detector should withstand the high level of radiation to be expected for LHC operation. Therefore systematic studies on the change of the detector performance due to radiation damage have been made, or are in progress. Well established results on neutron related damage at room temperature have been extended to lower temperatures, as foreseen for operation at LHC. For comparison proton damage studies have also been started. The detector properties under investigation include the reverse current, the depletion voltage and the charge collection efficiency. With a compressed 10 year LHC operational scenario we have successfully checked the ability of silicon detectors to survive the period influences of high fluence irradiation and subsequent annealing.

Using γ + jets production to calibrate the Standard Model \( Z\left( { \to v\bar{v}} \right) \) + jets background to new physics processes at the LHC

The irreducible background from Z (→ νν) + jets, to beyond the Standard Model searches at the LHC, can be calibrated using γ + jets data. The method utilises the fact that at high vector boson pT (≫ MZ), the event kinematics are the same for the two processes and the cross sections differ mainly due to the boson-quark couplings. The method relies on a precise prediction from theory of the Z/γ cross section ratio at high pT, which should be insensitive to effects from full event simulation. We study the Z/γ ratio for final states involving 1, 2 and 3 hadronic jets, using both the leading-order parton shower Monte Carlo program Pythia8 and a leading-order matrix element program gambos. This enables us both to understand the underlying parton dynamics in both processes, and to quantify the theoretical systematic uncertainties in the ratio predictions. Using a typical set of experimental cuts, we estimate the net theoretical uncertainty in the ratio to be of order ±7%, when obtained from a Monte-Carlo program using multiparton matrix-elements for the hard process. Uncertainties associated with full event simulation are found to be small. The results indicate that an overall accuracy of the method, excluding statistical errors, of order 10% should be possible.

The data acquisition and calibration system for the ATLAS Semiconductor Tracker

The SemiConductor Tracker (SCT) data acquisition (DAQ) system will calibrate, configure, and control the approximately six million front-end channels of the ATLAS silicon strip detector. It will provide a synchronized bunch-crossing clock to the front-end modules, communicate first-level triggers to the front-end chips, and transfer information about hit strips to the ATLAS high-level trigger system. The system has been used extensively for calibration and quality assurance during SCT barrel and endcap assembly and for performance confirmation tests after transport of the barrels and endcaps to CERN. Operating in data-taking mode, the DAQ has recorded nearly twenty million synchronously-triggered events during commissioning tests including almost a million cosmic ray triggered events. In this paper we describe the components of the data acquisition system, discuss its operation in calibration and data-taking modes and present some detector performance results from these tests

Neutron irradiation of silicon diodes at temperatures of +20°C and −20°C

Abstract We report measurements of the behaviour of silicon diodes when exposed to integrated neutron doses of up to 5 × 10 13 neutron/cm 2 . The measurements have been made at diode temperatures between room temperature and −20°C. From measurements of the diode leakage current and depletion voltage, and consequent evaluations of the effective impurity concentration, the temperature dependence of these quantities is discussed in terms of the annealing behaviour of the diodes. Comments are made on the suitability of silicon as a detector medium for particle physics experiments at future accelerators.

Study of neutron irradiated silicon counters with a fast amplifier

Abstract Silicon detectors have been irradiated with fluences of up to 2.7 × 10 13 neutrons/cm 2 , and have been subsequently studied using low-noise preamplifiers with a peaking time of about 15 ns. The detector response to minimum ionizing particles was found to be close to that of non-irradiated detectors. The short integration time of the preamplifier makes the shot noise due to the detector dark current tolerable up to at least 15 μA/channel.

Precision measurement of the

Abstract. A new precision measurement of the

\Xi^0

\Xi^0

mass and the branching ratios of the decays

mass has been performed at the NA48 experiment at the CERN SPS. The value obtained is [1314.82

\Xi^0\rightarrow\Lambda\gamma

\pm

and

0.06 (stat.)