Marc Sangel Supervisor Sebastian Johnert DESY Summer Student

Marc Sangel Supervisor: Sebastian Johnert DESY Summer Student Programm Hamburg, DESY, 02. September 2011

Outline Analysis Chain Hep. MCAnalysis Tool Results for different Generators Results for different PDFs Efficiencies Summary Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 2

Introduction Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 3

Analysis Chain LHC Search for new physics and particles Data Understanding signal and background processes Simulation Comparison with data Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 4

Hep. MCAnalysis Tool Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 5

Hep. MC Format > Graph structure of physics event > Hep. MC format: vertex and particle structure > Particles: kinematic information, ID, … > Each particle belongs at least to one vertex Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 6

Hep. MCAnalysis tool What is the Hep. MCAnalysis tool ? • Framework for Monte Carlo generator validation and comparison • Covers different aspects of event generation: hard process, UE, multiple parton interaction • Covers many physics processes like pp->Z, pp->ttbar, pp->W/Z +jets requirements • Hardly dependency on other software packages • User-friendly (many documentations, manuals, tutorials, …) • Simple extendable for user analysis Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 7

Workflow of Hep. MCAnalysis Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 8

• • Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 9

Results Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 10

Results for different generators: W histograms • Hardly differences between Pythia 6 and Pythia 8 • Higher differences between Herwig++ and Pythia • Herwig++ does not decrease for first bin → will be checked Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 11

Pythia 6 Herwig++ Pythia 8 Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 12

Results for different generators: charged stable particles number Pythia 6 Herwig++ Pythia 8 • peculiar behaviour of Pythia 8 • Pythia 6 and Herwig++ very similar Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 13

Parton Distribution Functions (PDFs) Usage of different orders • leading order (LO): MSTW 2008 lo 90 cl • next to leading order (NLO): CTEQ 66 • next to leading order (NNLO): HERAPDF 15 NNLOEIG • modified leading order (LOmod): MRST 2007 lomod What is modified leading order? • Want LO PDF to behave like NLO PDF • Improvement of quality of LO global fit • Relaxing the momentum sum rule at input • Use NLO strong coupling for LO PDF Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 14

Results for Different PDFs: W histograms LO NNLO LOmod (LO*) Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 15

LO NNLO LOmod (LO*) Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 16

Results for different PDFs: Charged particles number LO NNLO LOmod (LO*) • Again big differences for charged particle histograms Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 17

Efficiency calculation • • • Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 18

Results of efficiencies for different PDFs PDF Efficiency Error MSTW 2008 lo 90 cl 0. 12762 0. 00119961 CTEQ 66 (NLO) 0. 13482 0. 00123692 HERAPDF 15 NNLOEIG 0. 13427 0. 00123409 MRST 2007 lomod 0. 13617 0. 00124383 PDF Efficiency Error MSTW 2008 lo 90 cl 0. 08508 0. 0008 CTEQ 66 (NLO) 0. 08988 0. 000825 HERAPDF 15 NNLOEIG 0. 089513 0. 000823 MRST 2007 lomod 0. 09078 0. 000829 ATLAS: Efficiency: 0. 0975, Error: 0. 0019; (ar. Xive: 1108. 4101 v 1) Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 19

Summary Differences between LO and NLO PDFs Significant differences between PDFs and Generators for charged particles histograms Similar deviations for different tunes Efficiency similar to ATLAS results Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 20

Backup Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 21

Class Library Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 22

Generators Pythia • Hard process is calculated until leading order of parton distribution function • Connection between partons (strings), to avoid free quarks Herwig • Hard process also calculated until leading order • All gluons decay in qqbar pairs. • All quarks are composed in color neutral objects Marc Sangel | DESY Summer Student Programe | 2. September 2011 | page 23