Žilina, 14.3.2014 Z path with ATLAS data Ivan Melo

Particles of the Standard Model Z - path Z - path

Urýchľovače – továrne na nové častice E = mc2 p + p → Z p + p → H 91 GeV 91 GeV 91 GeV 125 GeV 1 GeV + 1 GeV + Ekin = 125 GeV 3

Transverse momentum pT Sum of initial pT = 0 Sum of final pT = 0

Z and Higgs production (Feynman diagrams)

Z - path

Z - path

Invariantná hmotnosť

Invariantná hmotnosť Signál +pozadie Pozadie (background)

ATLAS detector Elmag. kalorimeter Hadrónový kalorimeter Miónové detektory Dráhový detektor

pp -> Z -> e+e-

e+e-

e+e-

γγ

γγ

Veľa dráh, 2 eventy naraz (pile-up)

kvarky (a gluóny) vidíme ako „jety“, spŕšky hadrónov

neutríno Missing ET = missing pT > 25 GeV

Pick assigned number (1 or 2) and letter (A,B,C,....,Z) ATLAS Z-path http://www.physicsmasterclasses.org/index.php?cat=local_organisation&page=measurements Hypatia http://atlas.physicsmasterclasses.org/en/zpath_data.htm 1.Download 2.Unzip it onto your Desktop 3.To start HYPATIA: a. Navigate to the HYPATIA folder you downloaded b. On Windows and Mac:oDouble click on“Hypatia_7.4_Masterclass.jar” c. On Linux: Right click on “HYPATIA_for_Linux.sh” and change permissions so that it is executable. Double-click on “HYPATIA_for_Linux.sh” To access ATLAS data: username: ippog password: mc13 Pick assigned number (1 or 2) and letter (A,B,C,....,Z)

Datasets: ATLAS real pp-data from 2012 at 8 TeV Di-leptons: ~ 20 000 events - Di-electrons and di-muons from Z (mainly), Jpsi and Upsilon - 2 000 fully simulated Z’ events (mass 1 TeV) Higgs candidates: real data events corresponding to 2 fb-1 - Di-photon: 12 000 events cuts as in ATLAS publication–including converted photons - 4-leptons: 40 events cuts as in ATLAS publication - very little background! - almost no need to discuss ET miss!

Analysis - Evaluate your set of 50 events (e.g. 1C) - Make notes on your tally sheet (e.g. 1C) - Consult cheat list for students: http://cernmasterclass.uio.no/2014/material/cheat-sheet_en.pdf Set pT cut at 5 – 10 GeV Check tracks and physics objects If two tracks (+- charge) point to two elmag clusters in both views – e+e- candidate If no tracks point to two elmag clusters in both views - γγ candidate If two tracks (+- charge) continue to muon chambers – μμ candidate If four charged tracks (+-+-) - μμμμ, μμee, eeee candidate Check Pixel hits >= 2 and SCT hits >= 7 to see if particles come from the same vertex In case of converted photon candidate: check invariant mass of the (+-) double track, if close to 0, it is photon converted to e+e- - Enter candidate tracks as ee, μμ, γγ to see their invariant mass - Export invariant mass table as .txt file (File – Export invariant masses)

How to submit results OploT: http://cernmasterclass.uio.no/OPloT/index.php Click on Student For test pick January 01 2012, any test city, group number and letter Upload your .txt file with invariant masses (Browse button) If you need to delete a students upload, you can do this from the Administrator tab. Password: username: admin password: administrator

Chýbajúca priečna hybnosť If sum of final pT ≠ 0: 1+2+3 1 2 3 Missing pT = Missing ET = ETMiss ETMiss > 25 GeV (asi neutríno) ETMiss < 25 GeV (nie neutríno, skôr nedokonalosť detektora)