Package: compscat
CompScatAuthorAman DesaiDescriptionMonte Carlo simulation of fixed-target Compton scattering. The study has been compared with Madgraph5amc_NLO MC event generator. The full analysis can be found hereLink. The analysis is currently done in C++ (ROOT Framework). To analyse the Madgraph LHE file, an LHE reader deverlopedhereis used.PhysicsRepresentative Feynman diagrams for compton scatteringValidation of CompScatThe following plots compare the final states for CompScat with the Madgraph5amc_NLO final states.Cross sectionEvaluated using $10^6$ phase points with CompScat and using the Madgraph file as given in analysis folder.Plot showing the cross section versus energy (with error bars):Initial Photon EnergyCompScat $\sigma$ (milibarn)Madgraph $\sigma$ (milibarn)50 MeV15.585 $\pm$ 0.049515.57 $\pm$ 0.037100 MeV8.783 $\pm$ 0.03618.799 $\pm$ 0.028200 MeV4.857 $\pm$ 0.02554.87 $\pm$ 0.019300 MeV3.414 $\pm$ 0.02053.43 $\pm$ 0.0081400 MeV2.669 $\pm$ 0.01852.664 $\pm$ 0.0051500 MeV2.194 $\pm$ 0.01612.203 $\pm$ 0.0044In the following, the initial photon energy is set to 0.1 GeV (electron is at rest).Photon final state kinematicsElectron final state kinematicsInstallationUse:pipinstallcompscator to install from the latest branch use:gitclonehttps://github.com/amanmdesai/compscat.gitcdcompscat
pipinstall.Run the generator!Description of the example in notebooks:To import the library usefromcompscatimportCrossSection,SaveEvent,constants,PlotDataand then set the energy of the incoming photon in MeV:E=0.1The step below is the crucial step as the Cross Section is evaluated here. Only the energy is passed as an argument.w_sum,w_square,w_max=CrossSection(E/constants.m).integrate_xsec()The script below will generate the events according to the w_max obtained above and Energy specified by the user. Moreover, the below class will also save the events (either as root or in a csv file). To save in root format use:SaveEvent(10000,w_max,E).to_root()else to save them in a csv file use:SaveEvent(10000,w_max,E).to_csv()Finally the scripts below will plot the data and store it as pdf. If you have saved the events in a root format use:PlotData.file("MC_compton.root")else if you are using csv file, use:PlotData.file("MC_compton.csv")Evaluate the Cross sectionSee the notebook 'cross-section.ipynb'ExercisesEvaluate the cross section of compton scattering using theCrossSectionmodule for different initial proton energies. Plot the same.Study the final states at different energies and plot them on the same plot.Find the angles $\phi$ and $\theta$ of scattering.Make a 2D plot of the energy of photon/electron with the angle of scattering ( $\phi$ and $\theta$).AcknowledgementsWe would like to thank Dr. Olivier Mattelaer (UCLouvain, Belgium), whose suggestion on applying cuts in the Madgraph configuration file was helpful in validation of the final states predicted by the CompScat package. We are grateful to Dr. Kilian Lieret (Princeton University, USA), whose suggestion to me about pre-commit config/python packaging (cookiecutter) was helpful in the overall formatting/structuring of the python package.ReferencesFor physics involved in the calculation, see for example,Introduction to Elementary Particles, David Griffiths.For monte carlo techniques:Statistical data analysis, Glen Cowan, 1998.For the equations used by the simulator see for example,LinkAlso see: Papaefstathiou, A. How-to: write a parton-level Monte Carlo particle physics event generator. Eur. Phys. J. Plus 135, 497 (2020).Alwall, J. and others, The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations.