Postgraduate Computing Lectures Applications I: Overview 1 Applications: Overview Symbiosis: Theory v. Experiment Theory –Build models to explain existing observations. –Used to predict further phenomena. Experiment –Designed to test theory and explore new phenomena. –Feeds back measurements to Theory. Theory (model building) Experiment (observation) Prediction Measurement

Postgraduate Computing Lectures Applications I: Overview 2 Applications: Overview: Software used in Experiment Life Cycle Conception/Design Choose technology and design detector to optimise Physics v Cost Construction Fabricate, assemble, align, test calibrate and test Simulation Model: beam or flux, detector and DAQ response Data Reduction Converting raw data to event hypotheses Physics Extraction Fit Physics model to event data sets Operation DAQ (Data Acquisition) Status and Control Event Reconstruction Signal calibration Hit reconstruction Pattern recognitions Track/Shower reconstruction Event characterisation (particle Ids, and energy) Analysis Root PAW Home grown Survey and Calibration Fitting measurements, test signals and standard source response Database Inventory Survey Calibration Monte Carlo Random sampling from defined distributions Real Time Equipment control and readout CAD (Computer aided design)

Postgraduate Computing Lectures Applications I: Overview 3 Applications: Overview: Off the Shelf v. DIY? HEP not Commercial! –No Microsoft package for HEP programs! –For most part we (HEP community) write our own. Don’t start from scratch –Many non-HEP generic packages (both commercial and free) e.g. Graphics libraries (GUI and Drawing) Databases –HEP specific packages e.g. Monte Carlo (e.g GEANT) Analysis ( e.g. Root, PAW) But each experiment is unique –So fill in missing parts using tools e.g. Languages to express solution:- –Computational (e.g Fortran, C++, Java) –Scripting (e.g Bourne shell, perl) Compilers, Linkers and Debuggers to implement

Postgraduate Computing Lectures Applications I: Overview 4 Applications: Overview: Collaboration = Communication Must communicate! –Have many members at many sites. –Report results to Physics community and beyond. Use IT to communicate –Capturing ideas Text (word processors, type setting) Graphical (drawing packages, engineering packages). Image processing. Presentation and publishing. –Dissemination across the network File transfer (FTP) and remote file access (AFS) with attachments. WWW – can handle wide range of visual (and audio) file formats. Video Conferences.