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Physics discussion ATLAS W exercise

Alpen. CMS. ALICE. Physics discussion ATLAS W exercise. LHC. 01.03.2011 Konrad Jende. Content. Measurement(s) Local combining Global combining More information / Links F.A.Q. Backup. Measurement(s). Structure of the Proton

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Physics discussion ATLAS W exercise

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  1. Alpen CMS ALICE Physics discussion ATLAS W exercise LHC 01.03.2011 Konrad Jende

  2. Content Measurement(s) Local combining Global combining More information / Links F.A.Q. Backup

  3. Measurement(s) • Structure of the Proton • What to measure? number of W events containing e+, e-, μ+, μ- • What to calculate? (only from quark-gluon interaction) • For what? Reveal structure of the proton • How?1. Exercise: Identifying particles (e-, e+, μ+, μ- , Jets, Neutrinos) • 2. Exercise: Identifying events (W+→e++ν, W+→ μ-+ν, W-→e-+ν, W-→ μ-+ν + BG)3. Measurement: • a) students will be split up in 20 groups • b) each group analyzes 50 events • c) signal (W) vs. background events (electric charge of the leptons in case of signal) • d) document results by using tally sheets • 4. local combining – explanations how students can derive statements about the • inner structure of the proton from this measurement • (5. global combining – comparison of the ratios) • Learning Objectives? • students proof the valence quark structure of the proton by doing a measurement of a • physics observable • • interpret this measurement and get basic insights from it using • theoretical/phenomenological arguments [for details look at the document: Aims of • Particle Physics Masterclasses by Michael Kobel]

  4. Measurement(s) • Search for new physics (Higgs search) • What to do? Search for simulated Higgs events • For what? Identify events where a Higgs decayed into WW • How?1. Measurement: Find those events in the data samples! • Document it on the tally sheet by noting the event number • 2. local combining – discussions of chosen events • 3. global combining – discussions of chosen events • Learning Objectives? • identify events which would be candidates for new physics and qualitatively • understand pre-conditions for claiming a discovery

  5. Local Combining Each group has to fill in its result. Students can compare their measurement (of the ratio of the number of positively charged W’s to the number of negatively charged W’s) with one of ATLAS (data taken from: Measurement of the W -> lnu and Z/gamma* -> ll production cross sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector Authors: The ATLAS Collaboration (Submitted on 11 Oct 2010) Revealing the proton structure with that ratio is pretty hard – that is why we have to bring some theory into play

  6. Global combining • Physics discussion at Videoconference - general facts and proton structure measurement • Where takes it place? EVO +EditGrid : http://www.editgrid.com/user/masterclass/Analysis_All • Online-spreadsheet, no password is needed, only input cells are editable • venues will enter their numbers after completing their measurement (at ca. 3:30pm on a • certain MC day) • What are you 1. Compare the “raw” ratio (usually about 1.4 – 1.6) among all venues • supposed to do? • 2. Combine the “raw” ratios and compare with the first ATLAS results • 3. Discuss the corrected ratios • 4. Always Remember: If you get very good answers of students or you see that they • reached good results, do not forget to praise their work! • 5. Do not repeat too much (that was already done locally) • Which tools help? ATLANTIS Event Display (MINERVA), Events, Website

  7. Global combining • Physics discussion at Videoconference - Higgs events • How to discuss the 1. You should know which events are the hidden simulated HWW events! • Possible Higgs 2. The venues will send the event numbers of their candidate events. Chose for example • candidate events? two events (one that isn’t a Higgs, one that is a Higgs). • (recommendation) 3. Use the Shared Desktop option by EVO to show your computer screen. • 4. Start MINERVA, read the two events (you may copy them into a folder to more easily • present) and show them. • 5. Ask the speaker of the venue that proposed these events why they thought this was a Higgs event. • 6. Make clear why in your opinion an event is or is not a possible Higgs candidate. • 7. You could also use the MINERVA demonstration mode to animate the collision event • (Event – Animated event; set up PT cut before) • 8. After finishing the discussion about the particular events tell them a little bit more • about discoveries in your experiment (not only Higgs) and their claiming • Which tools help? ATLANTIS Event Display (MINERVA), Events, Website

  8. More information / Links Website with information on the W measurement: www.cern.ch/kjende/en/wpath.htm Details on the pre-selection of the ATLAS data, instructions how to use both website as well as the Event Display MINERVA: www.cern.ch/kjende/en/documentation2.htm If you have further questions do not hesitate to contact me: Konrad.jende@cern.ch – 3-R-006 at CERN

  9. F.A.Q. www.cern.ch/kjende/en/documentation2.htm

  10. Backup Aims of Particle Physics Masterclasses (by Michael Kobel) Local Combining: Tally sheet Local Combining: extra stuff about development of the ratio R± and ist uncertainty

  11. Learning Objectivs • Aims of Particle Physics Masterclasses 1: • On a basic Level: Students should (e.g. via lectures) • be *informed* (not taught) about general topics of current research in high energy particle physics (hep), central findings of hep research in last ~30 years, (standard model, building blocks, forces, charges,…), status and aims of current experiments (LHC, …) • get insight in the way hep research is organized in international collaborations, in dialogue/exchange of experiment and theory , wrt. methods of discovery of new phenomena, (counting methods, perhaps mass peaks, etc.) • Students should *learn* themselves to • identify different particles via their pattern in detectors • categorize events of LHC in pre-defined final states • understand the concept of signal and bachground • do a measurement of a physics observable (LHC W-path: ratio of W+ / W- ) • interpret this measurement and get basic insights from it using theoretical/phenomenological arguments ( proton structure, …) • identify events which would be candidates for new physics and qualitatively understand pre-conditions for claiming a discovery (e.g. WW or ZZ events as Higgs candidates, 3 lepton events as SUSY candidates)

  12. Learning Objectivs • Aims of Particle Physics Masterclasses 2: • Get the feeling that they: • understand the basic principles how particles are identified, • are able to perform themselves some of the measurements, which the scientists currently do, on a somewhat simplified level • are able to draw conclusions from these measurements • get the impression that • topics of fundamental research in natural science are interesting • its results are relevant as cultural knowledge of mankind

  13. Local Combining Each group has to fill in its result. Students can compare their measurement (of the ratio of the number of positively charged W’s to the number of negatively charged W’s) with one of ATLAS (data taken from: Measurement of the W -> lnu and Z/gamma* -> ll production cross sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector Authors: The ATLAS Collaboration (Submitted on 11 Oct 2010) Revealing the proton structure with that ratio is pretty hard – that is why we have to bring some theory into play

  14. Local Combining Each group has to fill in its result. Students can compare their measurement (of the ratio of the number of positively charged W’s to the number of negatively charged W’s) with one of ATLAS (data taken from: Measurement of the W -> lnu and Z/gamma* -> ll production cross sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector Authors: The ATLAS Collaboration (Submitted on 11 Oct 2010) Revealing the proton structure with that ratio is pretty hard – that is why we have to bring some theory into play Numbers in the spreadsheet taken from own research

  15. Local Combining Work out the fraction of gluon-gluon interaction for W+ and W-! Work out the fraction of quark-gluon interaction for W+ and W- by forming the sum of the first column! Forming the ratio of the number of positively charged W’s to the number of negatively charged W’s and LET THE STUDENTS INTERPRET ITS RESULT!

  16. Local Combining Work out the fraction of gluon-gluon interaction for W+ and W-! Work out the fraction of quark-gluon interaction for W+ and W- by forming the sum of the first column! Forming the ratio of the number of positively charged W’s to the number of negatively charged W’s and LET THE STUDENTS INTERPRET ITS RESULT!

  17. Local Combining Work out the fraction of gluon-gluon interaction for W+ and W-! Work out the fraction of quark-gluon interaction for W+ and W- by forming the sum of the first column! Forming the ratio of the number of positively charged W’s to the number of negatively charged W’s only from quark-gluon interaction and LET THE STUDENTS INTERPRET THEIR RESULT!

  18. Local Combining Extra stuff: development of R± and its uncertainty depending on the absolute number of analyzed events

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