Z path with ATLAS data 30.3. 2017 Ivan Melo Workshop, Žilina, 17.2. 2017 Z path with ATLAS data 30.3. 2017 Ivan Melo Z and W with CMS data 11.2. 2016 W path with ATLAS data 2015

Particles of the Standard Model Z - path Z - path

Z and Higgs production (Feynman diagrams)

Z - path

Z - path

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

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)

Invariantná hmotnosť

Invariantná hmotnosť Signál +pozadie Pozadie (background)

Z' boson Graviton (spin 2) G → e+e-, μ+μ- G → γγ G → ZZ → l+l-l+l- a heavy partner of the Z boson and is predicted by some theories beyond the Standard Model Graviton (spin 2) It is expected that a hypothetical force particle, the graviton (G), is the mediator of gravity G → e+e-, μ+μ- G → γγ G → ZZ → l+l-l+l-

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

To access ATLAS data (2017: no password needed!): username: ippog ATLAS Z-path http://www.physicsmasterclasses.org/index.php?cat=local_organisation&page=measurements http://atlas.physicsmasterclasses.org/en/zpath.htm 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 (2017: no password needed!): username: ippog password: mc13 Pick assigned number (1 or 2) and letter (A,B,C,....,Z) Start with Exercise 2: http://atlas.physicsmasterclasses.org/en/zpath_exercise2.htm

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

Analyzing your results Di-lepton measurement Compare the histograms of the electron-positron and muon-antimuon pairs. Can you point out differences/similarities? How often does the Z boson decay into electron-positron pairs? How often does the decay result in muon-antimuon pairs? What did you expect? Why? Do you notice any other particles? At which invariant masses? What is the most probable mass of the Z boson? Why is there not one exact value for the Z boson mass? What could be the possible explanations of why the distribution is so wide? Have you discovered the Z' boson? If you think so, what is the Z' boson's mass? Why is it useful to combine your results with those obtained by other groups? Di-photon measurement Do you see any sign of Higgs decaying to 2 photons, H→γγ? If no, what could be the reasons? In fact the full sample does contain some real Higgs candidates, even if you you have not found them!

Datasets: ATLAS real pp-data from 2012 at 8 TeV Backup from 2014 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!