Stavebné kamene tohto sveta Trenčín, 18.3.2016 Stavebné kamene tohto sveta Ivan Melo

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Rutherfordov experiment 1908 - 1913

Od atómov ku kvarkom 4

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Čo lepí základné kamene do štruktúr? ….sily

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Štyri základné sily 11

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W and Z decays Higgs decay events: H ZZ e+e-e+e- H ZZ e+e-μ+μ- H ZZ μ+μ-μ+μ- H γγ

Higgs production

Higgs decay

Discovery of Higgs-like particle H → l+l-l+l-

Žilina, 1.3.2012 Z bozóny na LHC Ivan Melo

Z bozón je produkovaný minimálne 4 spôsobmi: 1. q antiq → Z (q = u alebo d) 2. g q → Z q (g = gluon) 3. q antiq → Z g 4. g g → q antiq Z

Kritériá pre Z bozón Z eventy vs pozadie ● chýbajúca priečna energia ETMiss < 25 GeV ● elektrón-pozitrón alebo mión-antimión IZOLOVANÉ od jetov ● priečna hybnosť leptónov > 25 GeV ● l+l- musia pochádzať z jednej zrážky (vylúčiť pile-up) ● l+l- sú zvyčajne kolineárne v priečnej rovine, ale NEMUSIA byť Z eventy vs pozadie

How many peaks are there in the mass plot? Where is the Z peak? What is the mass of the Z boson? What do the other peaks mean? Where is the ZZ peak in the plot? Why that mass? What is the ratio of electrons to muons? Is it close to what we should expect? What is the W+/W- ratio? What should it be?

How many peaks are there in the mass plot? J/ψ bound state c/anti c, 3.1 GeV, l+l- 5.94 % ϒ bound state b/anti b 9.46 GeV, l+l- 2.4 % Z mediator of weak interaction, 91.2 GeV, l+l- 3.36 % ZZ H Higgs boson, 126 GeV decays to ZZ -> 4 l 2.5 % The rest are not peaks, just B fluctuations or analysis errors Where is the Z peak? What is the mass of the Z boson? What do the other peaks mean? Where is the ZZ peak in the plot? Why that mass? Mass Z + mass Z > mass H ??? (one Z is „virtual“) What is the ratio of electrons to muons? Is it close to what we should expect? 1 … because both W and Z decay democratically into e/mu

What is the W+/W- ratio? What should it be? R = W+/W- > 1

In the videoconference, studenta might ask questions like Why are the widths or heights or numbers of peaks different from one Institute to the next? Why do different Institutes get different ratios? How did they identify electrons or muons or W candidates or Z candidates or zoo events? How did they measure charge for W candidates? Now that the Tevatron is shut down, what do you do at Fermilab? Is it boring at CERN when the LHC is not running? Why did you become a physicist? ...and better questions which only students can create.