Insights into the chemical biology of selenium

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Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method

This paper discusses hadron energy reconstruction for the ATLAS barrel prototype combined calorimeter (consisting of a lead-liquid argon electromagnetic part and an iron-scintillator hadronic part) in the framework of the non-parametrical method. The non-parametrical method utilizes only the known $e/h$ ratios and the electron calibration constants and does not require the determination of any parameters by a minimization technique. Thus, this technique lends itself to an easy use in a first level trigger. The reconstructed mean values of the hadron energies are within $\pm 1$ of the true values and the fractional energy resolution is $[(58\pm3)/\sqrt{E}+(2.5\pm0.3)$. The value of the $e/h$ ratio obtained for the electromagnetic compartment of the combined calorimeter is $1.74\pm0.04$ and agrees with the prediction that $e/h > 1.7$ for this electromagnetic calorimeter. Results of a study of the longitudinal hadronic shower development are also presented. The data have been taken in the H8 beam line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM

First-level trigger systems for LHC experiments

We propose to carry out a broad-based programme of R&D on level-1 trigger systems for LHC experiments. We will consider the overall level-1 which coordinates different subtriggers and which interacts with the front end electronics and with the level-2 system. Careful attention will be paid to systems aspects and problems of synchronization within the pipelined processor system. Trigger algorithms for selecting events with high-pt electrons, photons, muons, jets and large missing Et will be evaluated by physics simulation studies. We will study possible implementations of such trigger algorithms in fast electronics by making conceptual design studies and using behavioural simulation models. For critical areas more detailed design studies will be made, and prototypes of some key elements will be constructed and tested. The proposed R&D project builds on existing studies and will complement other R&D projects already funded by the DRDC

Evaluation of Fermi Read-out of the ATLAS Tilecal Prototype

Prototypes of the \fermi{} system have been used to read out a prototype of the \atlas{} hadron calorimeter in a beam test at the CERN SPS. The \fermi{} read-out system, using a compressor and a 40 MHz sampling ADC, is compared to a standard charge integrating read-out by measuring the energy resolution of the calorimeter separately with the two systems on the same events. Signal processing techniques have been designed to optimize the treatment of \fermi{} data. The resulting energy resolution is better than the one obtained with the standard read-out

Response of the ATLAS tile calorimeter prototype to muons

A study of high energy muons traversing the ATLAS hadron Tile calorimeter in the barrel region in the energy range between 10 and 300~GeV is presented. Both test beam experimental data and Monte Carlo simulations are given and show good agreement. The Tile calorimeter capability of detecting isolated muons over the above energy range is demonstrated. A signal to background ratio of about 10 is expected for the nominal LHC luminosity ($10^{34} cm^{-2} sec^{-1}$). The photoelectron statistics effect in the muon shape response is shown. The e/mip ratio is found to be $0.81 \pm 0.03$; the e/$\mu$ ratio is in the range 0.91 - 0.97. The energy loss of a muon in the calorimeter, dominated by the energy lost in the absorber, can be correlated to the energy loss in the active material. This correlation allows one to correct on an event by event basis the muon energy loss in the calorimeter and therefore reduce the low energy tails in the muon momentum distribution

A measurement of the energy loss spectrum of 150 GeV muons in iron

The energy loss spectrum of 150 GeV muons has been measured with a prototype of the ATLAS hadron calorimeter in the H8 beam of the CERN SPS.\\ The differential probability $dP/dv$ per radiation length of a fractional energy loss $v = \Delta E_{\mu} / E_{\mu}$ has been measured in the range $v = 0.01 \div 0.95$; it is then compared with the theoretical predictions for energy losses due to bremsstrahlung and production of electron-positron pairs or of energetic knock-on electrons.\\ The integrated probability $\int_{0.01}^{0.95} (dP/dv) dv$ is $(1.610\pm0.015_{stat.}\pm0.105_{syst.})\cdot10^{-3}$ in agreement with the theoretical predictions of $1.556\cdot10^{-3}$ and $1.619\cdot10^{-3}$. %7.8.96 - start Agreement with theory is also found in two intervals of $v$ where production of electron-positron pairs and knock-on electrons dominates. In the region of bremsstrahlung dominance ($v = 0.12\div0.95$) the measured integrated probability $(1.160\pm0.040_{stat}\pm0.075_{syst})\cdot 10^{-4}$ is in agreement with the theoretical value of $1.185 \cdot 10^{-4}$, obtained using Petrukhin and Shestakov's \cite{PS} description of the bremsstrahlung process. The same result is about 3.6 standard deviations (defined as the quadratic sum of statistical and systematic errors) lower than the theoretical prediction of $1.472\cdot 10^{-4}$, obtained using Tsai's \cite{TS} description of bremsstrahlung