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W path with ATLAS data
Žilina, 6.2.2015
Ivan Melo
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Particles of the Standard Model
W - path
W - path
Hadrons: p, n, π, K, ...
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L H C j e naj väč ším a naj z lož it ej ším vedeckým nást r oj om, aký bol kedy post avený
27 km supravodivých magnetov chladených na 1,9 Kelvina
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Urýchľovače – továrne na nové častice
E = mc2
p + p → H + ...
1 GeV + 1 GeV + Ekin = 125 GeV
91 GeV91 GeV
125 GeV + ...
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ATLAS detectorElmag. kalorimeter
Hadrónový kalorimeter
Dráhový detektor
Miónové detektory
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pT1
pT2
Sum of initial pT = 0 Sum of final pT = 0
Transverse momentum pT
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If sum of final pT ≠ 0:1 2
3
1+2+3
Missing pT = Missing ET = ETMiss
Chýbajúca priečna hybnosť
ETMiss > 20 GeV (asi neutríno)
ETMiss < 20 GeV (nie neutríno, skôr nedokonalosť detektora)
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Beta decay
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W production and decay
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Higgs boson production
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W - path
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H W+ W- e+μ- ννe+e- νν μ+μ- ννμ+e- νν
Higgs boson decay via WW channel
W decay
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e-/e+
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μ-/μ+
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μ-/μ+
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neutríno
Missing ET = missing pT > 20 GeV
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kvarky (a gluóny) vidíme ako „jety“, spŕšky hadrónov
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Veľa dráh, 2 eventy naraz (pile-up)
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Invariantná hmotnosť
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Invariantná hmotnosť
Pozadie (background)Signál +pozadie
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To access ATLAS data:username: ippogpassword: mc13Pick assigned number (1 or 2) and letter (A,B,C,....,Z)
http://www.physicsmasterclasses.org/index.php?cat=local_organisation&page=measurements
ATLAS Z-path
Hypatia
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”
http://atlas.physicsmasterclasses.org/en/zpath_data.htm
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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!
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- 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)
Analysis
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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: adminpassword: administrator
How to submit results