G. Herten

UNIQUE SOLUTION FOR THE WEAK NEUTRAL CURRENT COUPLING-CONSTANTS IN PURELY LEPTONIC INTERACTIONS

Abstract By combining results from the MARK-J at PETRA on Bhabha scattering, μ + μ - and τ + τ - production with recent world data from neutrino-electron scattering experiments, we determine unique values for the leptonic weak neutral current coupling constants g V and g A in the framework of electroweak models containing a single Z 0 . In contrast to previous analyses, we only use data from purely leptonic interactions, and therefore avoid the inherent uncertainties resulting from the use of hadronic targets. From the MARK-J data alone in the context of the standard SU(2) ⊗ U (1) model of Glashow, Weinberg and Salam, we find sin 2 θ W =0.24±0.11.

Ageing studies for the ATLAS-monitored drift tubes

Abstract The lifetime of drift tubes operated with Ar–CH 4 –N 2 91–5–4, Ar–CH 4 –N 2 –CO 2 94–3–2–1, Ar–CF 4 –N 2 –CO 2 94.5–0.5–2–3 and Ar–CO 2 80–20 is studied under various conditions. H 2 O and ethanol were successfully tested as a remedy against ageing. The method of glow discharge in argon is used to clean the cathode and inefficient wires and first results of this treatment are presented.

STUDY OF ELECTRON-POSITRON COLLISIONS AT THE HIGHEST PETRA ENERGY

Abstract We report on the results of the study of e + e − collisions at the highest PETRA energy of √ s = 31.57 GeV, using the 4π sr, electromagnetic and calorimetric detector Mark J. Based on 88 hadron events, and an integrated luminosity of 243 nb −1 we obtain R = σ (e + e − → hadrons)/ σ (e + e − → μ + μ − ) = 4.0 ± 0.5 (statistical) ± 6 (systematic). The R value, the measured thrust distribution and average spherocity show no evidence for the production of new quark flavors.

High rate performance of drift tubes

Abstract This article describes calculations and measurements of space charge effects due to high rate irradiation in high resolution drift tubes. Two main items are studied: the reduction of the gas gain and changes of the drift time. Whereas the gain reduction is similar for all gases and unavoidable, the drift time changes depend on the kind of gas that is used. The loss in resolution due to high particle rate can be minimized with a suitable gas. This behaviour is calculable, allowing predictions for new gas mixtures.

Studies of micromegas chambers using UV-laser-photoelectrons

Micro Pattern Gaseous Detectors (MPGD) are a new and very promising type of gaseous detector for future experiments. Their big advantages are that they are radiation hard and also provide a spatial resolution of several microns. But at the moment, there are still unavoidable discharges occurring randomly, which reduce the achievable gain and can destroy the readout and the detector with time. This talk will present a dedicated test setup, that has been built to investigate geometries of readout structures for MPGD, in order to eliminate or minimize discharges and achieve higher rate capabilities without the application of resistive layers. The measuring principle of the test chamber is to simulate tracks of charged particles. This is done by creating photo electrons in the drift room above the MPGD on aluminum strips with the help of a UV laser. The electrons are guided by a homogenous drift field to the detector. In contrast to using particles from radioactive sources or a test beam, the spatial and temporal conditions of the electron release are very well known. The setup can be modified easily to control the point of impact of the electrons on the detector. First studies such as gain gain measurements of a Micromegas and drift velocity measurements of electrons in ArCO2 have been carried out successfully and are presented as proof of a good performance of the MPGD test chamber.

A setup to study properties of Micro-Pattern Gaseous Detectors with laser-photoelectrons

Micro Pattern Gaseous Detectors (MPGD) are a new and very promising type of gaseous detector for future experiments. Their big advantages are that they are radiation hard and also provide a spatial resolution of several microns. But at the moment, there are still unavoidable discharges occurring randomly, which reduce the achievable gain and can destroy the readout and the detector with time.

Study of jet shapes in inclusive jet production in pp collisions at {radical}(s)=7 TeV using the ATLAS detector

Jet shapes have been measured in inclusive jet production in proton-proton collisions at sqrt(s) = 7 TeV using 3 pb^{-1} of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-kt algorithm with transverse momentum 30 GeV < pT < 600 GeV and rapidity in the region |y| < 2.8. The data are corrected for detector effects and compared to several leading-order QCD matrix elements plus parton shower Monte Carlo predictions, including different sets of parameters tuned to model fragmentation processes and underlying event contributions in the final state. The measured jets become narrower with increasing jet transverse momentum and the jet shapes present a moderate jet rapidity dependence. Within QCD, the data test a variety of perturbative and non-perturbative effects. In particular, the data show sensitivity to the details of the parton shower, fragmentation, and underlying event models in the Monte Carlo generators. For an appropriate choice of the parameters used in these models, the data are well described.

Measurement of the inclusive isolated prompt photon cross section in pp collisions at {radical}(s)=7 TeV with the ATLAS detector

A measurement of the cross section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy root s = 7 TeV is presented. The measurement covers the pseudorapidity ranges vertical bar eta(gamma)vertical bar < 1: 37 and 1: 52 <= vertical bar eta(gamma)vertical bar < 1: 81 in the transverse energy range 15 <= E-T(gamma) < 100 GeV. The results are based on an integrated luminosity of 880 nb(-1), collected with the ATLAS detector at the Large Hadron Collider. Photon candidates are identified by combining information from the calorimeters and from the inner tracker. Residual background in the selected sample is estimated from data based on the observed distribution of the transverse isolation energy in a narrow cone around the photon candidate. The results are compared to predictions from next-to-leading-order perturbative QCD calculations.A measurement of the cross section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy √s=7TeV is presented. The measurement covers the pseudorapidity ranges |ηγ|<1. 37 and 1.52≤|ηγ|<1.81 in the transverse energy range 15≤ETγ<100GeV. The results are based on an integrated luminosity of 880nb-1, collected with the ATLAS detector at the Large Hadron Collider. Photon candidates are identified by combining information from the calorimeters and from the inner tracker. Residual background in the selected sample is estimated from data based on the observed distribution of the transverse isolation energy in a narrow cone around the photon candidate. The results are compared to predictions from next-to-leading-order perturbative QCD calculations.

The First Year of the Large Hadron Collider: A Brief Review

The first year of LHC data taking provided an integrated luminosity of about 35 pb-1 in proton–proton collisions at . The accelerator and the experiments have demonstrated an excellent performance. The experiments have obtained important physics results in many areas, ranging from tests of the Standard Model to searches for new particles. Among other results, the physics highlights have been the measurements of the W-, Z-boson and production cross-sections, improved limits on supersymmetric and other hypothetical particles and the observation of jet-quenching, elliptical flow and J/ψ suppression in lead–lead collisions at .

Using electron drift velocity measurements for different electric field strengths to precisely monitor the gas composition in gaseous detectors

High precision tracking using gaseous detectors mainly has two basic requirements: the first being a stable gas composition, the latter being a well-known space-drift time relation. But due to several reasons such as e.g. contamination by water or air a change of the gas composition might occur and thus influence the real space-drift time relation. To continuously monitor the composition of the gas therefore is the main design goal of the assembly introduced in this article. It is reached by a measurement of the drift velocity of electrons inside the gas as function of different electric field strengths. Finally, comparisons with Monte Carlo-simulations are drawn to extract the cause of the drift velocity change.