2015 CERN Summer student workshop

Exercises

Discover the Higgs boson at the LHC:

• Find predictions for Higgs boson production at the LHC ​here.
• Find the Higgs boson branching ratio table here​.
• Choose a channel and investigate both the signal and background:
  1. The 4 lepton final state: $pp \to H\to Z Z \to e^+e- \mu^{+ \mu}-$
     • Signal Plots: Parton Level​ Detector Level​
     • Background Plots: Parton Level​ Detector Level​
  2. Top associated production $pp \to t\bar tH$ with $H \to b \bar b$
     • Signal + Background Plots: Parton Level​ Detector Level​

The Challenge

Three "black boxes" are given, in the form of event files in the LHC Olympics (LHCO) format and a series of selected figures.

• Box A : Events​, parton level figures​, detector level figures​
• Box B : Events​, parton level figures​, detector level figures
• Box C : Events​, parton level figures​, Detector level figures

These Black boxes are associated with signal events only. It is asked to pair up the boxes above with the three following new physics models and answer the related questions:

• Model 1 : Extra Z (zp) : What is its mass? Does it have Standard Model couplings to fermions?
• Model 2 : Heavy Scalar (h): What is its mass? Is it a SM Higgs?
• Model 3 : Extra W (wp+ or wp-) : What its mass? Does it have Standard Model couplings to fermions?

To solve these exercises, useful extra information can be found below:

In the plots $H_T=\sum

p_T{vis}

+ E_T{miss}$.

• A SM-like Z' would decay (more or less democratically) into: jet jet (uu~,cc~,dd~,ss~,bb~), t tbar (tt~), lept+lept- (e+e-,mu+mu-,ta+ta-), neutrino anti-neutrino (ve ve~,vm vm~,vt vt~). It could also have couplings to SM W and Z, and in that case would decay in to ZZ and W+W-.
• An Higgs couple to particles with a strength which is proportional to the particle masses. A SM-like heavy H would decay in to t tbar (tt~), W+W-, ZZ.
• A SM-like W'+ would decay into: jet jet (ud~,cs~), t b (tb~), lept neutrino (e+ ve , mu+ vm, ta+ vt). It could also have couplings to SM W and Z, and in that case would decay in to ZW.

Animations

• ​Interactive Flash version Note you may want to zoom in!
• ​Fast movie (.avi) of collision
• ​Guided movie (.mov) of collision
• ​John Ellis on Daily Show
• ​LHC_Rap

Slides

• Download here