C. Geweniger

A new determination of the Ko → π+π− decay parameters

Abstract In a short neutral beam we have measured the proper time-dependence of the decay K o → π + π − . This time structure exhibits the interference between the short- and long-lived states and is in agreement with the general expectations of the CP violation phenomenology. This experiment gives new and more precise measurements of the following three parameters: 1. i) the decay width of the short-lived K S component: Γ S = (1.119±0.006) × 10 10 sec −1 ; 2. ii) the modulus of the CP violating parameter η +- : | η +- | = (2.30±0.035) × 10 −3 ; 3. iii) the phase of η +- as a function of the K S −K L mass difference Δm : φ +- = (49.4±1.0) o + [( Δm −0.540)/0.540] × 305 o The result of |η +- | may be compared with the result of the foregoing letter on Re ϵ in the frame of the superweak model. Good agreement is observed.

Measurement of the kaon mass difference mL-mS by the two regenerator method

Abstract The K0 mass difference has been measured by the two regenerator method. The result is: Δm = mKL − mKS = (0. 534 ± 0.003) × 1010 sec−1.

Measurement of the charge asymmetry in the decays KoL → π±e±ν and KoL → π±μ±ν

The charge asymmetry in semi-leptonic K L 0 decays has been measured in a high statistics experiment using multi-wire proportional chambers. The asymmetry δ = ( N + − N − )/( N + + N − ), where N + and N − are the partial decay rates for K L 0 → π − Q + ν and K L 0 → π + Q − , respectively, is found to be δ L e = (3.41 ± 0.18) × 10 −3 for the K e3 mode, and δ L μ = (3.13 ± 0.29) × 10 −3 for the K μ3 mode. Assuming CPT invariance and the absence of Δ S = −Δ Q transitions, these results lead to a value of the real part of the CP -violation parameter ɛ, Re ɛ = (1.67 ± 0.08) × 10 −3 .

Measurement of the electromagnetic interaction of the neutral kaon

An experiment has been performed to search for the interference between the nuclear and the electron regeneration amplitudes of the neutral kaon. The detailed experimental analysis of the coherent and diffraction nuclear regeneration of long-lived kaons on copper and uranium nuclei has led to a value of the mean square charge radius of the neutral kaon, 〈R2〉 = (0.08 ± 0.05) fm2. The forward regeration amplitudes and the total KL− nucleus cross sections have been determined in auxiliary measurements between 4 and 10 GeV/c.

Search for Delta S=2 Decays of Neutral xi Hyperons

A search for the decay Ξ0→pπ− has been performed in a neutral hyperon beam derived from the 24 GeV/c external proton beam at CERN. The experiment gives as a 90% confidence upper limit for the branching ratio Γ(Ξ0→pπ−)Γ(Ξ0→Λπ0)<3.6×10−5.

Beam test of the ATLAS level-1 calorimeter trigger system

The level-1 calorimeter trigger consists of a preprocessor (PP), a cluster processor (CP), and a jet/energy-sum processor (JEP). The CP and JEP receive digitised trigger-tower data from the preprocessor and produce regions-of-interest (RoIs) and trigger multiplicities. The latter are sent in real time to the central trigger processor (CTP) where the level-1 decision is made. On receipt of a level-1 accept, readout driver modules (RODs) provide intermediate results to the data acquisition (DAQ) system for monitoring and diagnostic purposes. RoI information is sent to the RoI builder (RoIB) to help reduce the amount of data required for the level-2 trigger. The level-1 calorimeter trigger system at the test beam consisted of 1 preprocessor module, 1 cluster processor module, 1 jet/energy module and 2 common merger modules. Calorimeter energies were successfully handled throughout the chain and trigger objects sent to the CTP. Level-1 accepts were successfully produced and used to drive the readout path. Online diagnostics were made using 4 RODs. Energy histograms were plotted and the integrity of data between the different modules was checked. All ATLAS detectors in the test beam were able to build full events based on triggers delivered by the calorimeter trigger system.

Production Test Rig for the ATLAS Level-1 Calorimeter Trigger Digital Processors

R. Achenbach b , V. Andrei b , B. Bauss , B.M. Barnett . C. Bohm , J.R.A. Booth , I.P. Brawn , D.G. Charlton , C.J. Curtis , A.O. Davis , J. Edwards , E. Eisenhandler , P.J.W. Faulkner , F. Fohlisch , C. N. P. Gee , C. Geweniger , A.R. Gillman , P. Hanke , S. Hellman , A. Hidvegi , S. Hillier , E-E. Kluge , M. Landon , K. Mahboubi , G. Mahout , K. Meier , V.J.O. Perera , W.Qian , S. Rieke , F. Ruhr , D.P.C Sankey , R.J. Staley , U. Schafer , K. Schmitt , H.C. Schultz-Coulon , S. Silverstein , R. Stamen , S. Tapprogge , J.P. Thomas , T. Trefzger , D. Typaldos , P.M. Watkins , A. Watson , P. Weber , E.E. Woerhling a

Pre-production validation of the ATLAS level-1 calorimeter trigger system

The Level-1 Calorimeter Trigger is a major part of the first stage of event selection for the ATLAS experiment at the LHC. It is a digital, pipelined system with several stages of processing, largely based on FPGAs, which perform programmable algorithms in parallel with a fixed latency to process about 300 Gbyte/s of input data. The real-time output consists of counts of different types of trigger objects and energy sums. Prototypes of all module types have been undergoing intensive testing before final production during 2005. Verification of their correct operation has been performed stand-alone and in the ATLAS test-beam at CERN. Results from these investigations will be presented, along with a description of the methodology used to perform the tests.

Commissioning of the Jet/Energy-sum and Cluster Processors for the ATLAS Level-1 Calorimeter Trigger System

The ATLAS first-level calorimeter trigger is a hard warebased system designed to identify high-p T jets, electron/photon and tau candidates, and to measure total and missing E T. The trigger consists of a Preprocessor system which digitises 7200 analogue inputs, and two digit al multicrate processor systems which find jets, measure en ergy sums, and identify localised energy deposits (electron/ph oton and tau candidates). In order to provide a trigger quic kly enough, the hardware is parallel and pipelined. Experience so far of the Jet/Energy-sum and Cluster Processor system production, commissioning, and integration into ATLAS will be described.

Large scale production of the Multi-Chip Module of the ATLAS Level-1 Calorimeter Trigger

The Multi-Chip Module (MCM) is the main processing block of the Pre-Processor System in the ATLAS Level-1 Calorimeter Trigger. The MCM holds a dedicated signal-processing ASIC and a Phos4 timing-chip together with seven commercial dice mounted on the substrate. Those are four FADCs and three LVDS-serializers. The MCM contains the main functionality of the PreProcessor System, namely the digitization, calibration and Bunch-Crossing-Identification of calorimeter signals. Two output data streams are produced by the MCM. A real-time stream transmits the processed data to the subsequent trigger processors. A readout stream provides readout information of the PreProcessor. The MCM is the smallest exchangeable unit of the PreProcessor. The ATLAS experiment will have 2048 MCMs installed in the Pre-Processor system. Including spares, the total number runs up to 3000. The production phases of the MCMs and test procedures for quality control at different stages of the production are presented.