Determination of the strong coupling constant at LEP

Multi-hadronic events produced in e+e- collisions provide an excellent laboratory to study QCD, the theory of strong interactions, and in particular to determine the strong coupling parameter alpha_s and demonstrate its predicted behavior as a function of the energy scale. Determinations of alpha_s at LEP will be reviewed with emphasis on event shape variables and jet rates in 3-jet and 4-jet events.Comment: Proceedings of DIS06, XIV International Workshop on Deep Inelastic Scattering, Tsukuba, Japan, 20-24 April 2006, 4 pages, 2 figure

Forward pi^0-meson production at HERA

The production of high transverse momentum piz^0-mesons has been measured in deep-inelastic e-p scattering events at low Bjorken-$x$ taken with the H1 detector at HERA. The production of high p_T particles is strongly correlated to the emission of hard partons in QCD and is therefore sensitive to the dynamics of the strong interaction. For the first time the measurement of single particles has been extended to the region of small angles w.r.t. the proton remnant (forward region) and down to very low values of x ~ 5x10^-5. This region is expected to be particularly sensitive to QCD evolution effects in final states. Differential cross sections of inclusive pi^0-meson production have been measured as a function of Bjorken-x and the four-momentum transfer Q^2, and also as a function of the transverse momentum and the polar angle of the pi^0-mesons. A recent BFKL calculation and QCD models based on the DGLAP splitting functions are compared to the data. The best description of the data is achieved by the BFKL calculation.Comment: 3 pages, 2 figures, talk given on behalf of the H1 collaboration at DIS99, Zeuthe

Forward π0\pi^0 -Meson and Charged Particle Production in Deep Inelastic Scattering at low Bjorken-x

High transverse momentum pi^0 -mesons and charged particles are measured in deep inelastic e-p scattering events at low Bjorken-x taken with the H1 detector at HERA. The production of high-pt particles is strongly correlated to the emission of hard partons in QCD and is therefore sensitive to the dynamics of the strong interaction. For the first time the measurement of single particles has been extended to the region of small angles w.r.t. the proton remnant (forward region). This region is expected to be particularly sensitive to QCD evolution effects in final states. Results are presented as a function of Bjorken-x and x_i, the fraction of the incident proton's energy carried by the particle, and are compared to different QCD models

A Low Noise Receiver for Submillimeter Astronomy

A broadband, low noise heterodyne receiver, suitable for astronomical use, has been built using a Pb alloy superconducting tunnel junction (SIS). The RF coupling is quasioptical via a bowtie antenna on a quartz lens and is accomplished without any tuning elements. In its preliminary version the double sideband receiver noise temperature rises from 205 K at 116 GHz to 815 K at 466 GHz. This is the most sensitive broadband receiver yet reported for sub-mm wavelengths. Its multi-octave sensitivity and low local oscillator power requirements make this receiver ideal for remote ground observatories or space-borne telescopes such as NASA's Large Deployable Reflector. A version of this receiver is now being built for NASA's Kuiper Airborne Observatory

A configuration system for the ATLAS trigger

The ATLAS detector at CERN's Large Hadron Collider will be exposed to proton-proton collisions from beams crossing at 40 MHz that have to be reduced to the few 100 Hz allowed by the storage systems. A three-level trigger system has been designed to achieve this goal. We describe the configuration system under construction for the ATLAS trigger chain. It provides the trigger system with all the parameters required for decision taking and to record its history. The same system configures the event reconstruction, Monte Carlo simulation and data analysis, and provides tools for accessing and manipulating the configuration data in all contexts.Comment: 4 pages, 2 figures, contribution to the Conference on Computing in High Energy and Nuclear Physics (CHEP06), 13.-17. Feb 2006, Mumbai, Indi

The ATLAS Level-1 Muon to Central Trigger Processor Interface

The Muon to Central Trigger Processor Interface (MUCTPI) is part of the ATLAS Level-1 trigger system and connects the output of muon trigger system to the Central Trigger Processor (CTP). At every bunch crossing (BC), the MUCTPI receives information on muon candidates from each of the 208 muon trigger sectors and calculates the total multiplicity for each of six transverse momentum (pT) thresholds. This multiplicity value is then sent to the CTP, where it is used together with the input from the Calorimeter trigger to make the final Level-1 Accept (L1A) decision. In addition the MUCTPI provides summary information to the Level-2 trigger and to the data acquisition (DAQ) system for events selected at Level-1. This information is used to define the regions of interest (RoIs) that drive the Level-2 muontrigger processing. The MUCTPI system consists of a 9U VME chassis with a dedicated active backplane and 18 custom designed modules. The design of the modules is based on state-of-the-art FPGA devices and special attention was paid to low-latency in the data transmission and processing. We present the design and implementation of the final version of the MUCTPI. A partially populated MUCTPI system is already installed in the ATLAS experiment and is being used regularly for commissioning tests and combined cosmic ray data taking runs

The Octant Module of the ATLAS Level-1 Muon to Central Trigger Processor Interface

The Muon to Central Trigger Processor Interface (MUCTPI) of the ATLAS Level-1 trigger receives data from the sector logic modules of the muon trigger at every bunch crossing and calculates the total multiplicity of muon candidates, which is then sent to the Central Trigger Processor where the final Level-1 decision is taken. The MUCTPI system consists of a 9U VME crate with a special backplane and 18 custom designed modules. We focus on the design and implementation of the octant module (MIOCT). Each of the 16 MIOCT modules processes the muon candidates from 13 sectors of one half-octant of the detector and forms the local muon candidate multiplicities for the trigger decision. It also resolves the overlaps between chambers in order to avoid double-counting of muon candidates that are detected in more than one sector. The handling of overlapping sectors is based on Look-Up-Tables (LUT) for maximum flexibility. The MIOCT also sends the information on the muon candidates over the custom backplane via the Readout Driver module to the Level-2 trigger and the DAQ systems when a Level-1 Accept is received. The design is based on state-of-the-art FPGA devices and special attention was paid to low-latency in the data transmission and processing

The TriggerTool Graphical User Interface to the ATLAS Trigger Configuration Database

A system has been designed and implemented to configure all three levels of the ATLAS trigger system from a centrally provided relational database, in which an archive of all trigger configurations used in data taking is also maintained. The user interaction with this database is via a Java-based graphical user interface known as the TriggerTool. We describe here how the TriggerTool has been designed to fulfill several different roles for users of varying expertise, from being a browser of the database to a tool for creating and modifying configuration