Postgraduate Computing Lectures

Applications I: Overview 1

Applications: OverviewSymbiosis: 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/DesignChoose technology

and design detector to optimise Physics v Cost

ConstructionFabricate, assemble,

align, test calibrate and test

SimulationModel: beam

or flux, detector and DAQ response

Data ReductionConverting raw data to event hypotheses

Physics ExtractionFit Physics model to

event data sets

OperationDAQ

(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 andCalibration

Fitting measurements,test signals and

standardsource response

Database•Inventory

•Survey•Calibration

Monte CarloRandom sampling

from defineddistributions

Real TimeEquipmentcontrol and

readout

CAD(Computer

aideddesign)

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)

• Email with attachments.

• WWW – can handle wide range of visual (and audio) file formats.

• Video Conferences.