LHC Olympics Yeong Gyun Kim (KAIST)

LHC (the Large Hadron Collider) : 2007 ~ a proton + proton collider at 14 TeV c.m energy in the 26.6 km tunnel cm -2 s -1 ~ 10 fb -1 /yr (low luminosity) cm -2 s -1 ~ 100 fb -1 /yr (high luminosity)

Modern multi-purpose detector at colliders

 ATLAS  CMS (The Compact Muon Solenoid) 4 Tesla B-field (A Toroidal LHC Apparatus) 2 Tesla B-field Total weight : tons Overall diameter : 15 m Overall length : 21 m Diameter : 25 m Overall length : 46 m Overall weight : 7000 tons

Particle signatures left in the detector components

 Photons (0) A photon is detected as energy in the ECAL, with no high-transverse-momentum track, and little energy in the HCAL  Electrons (1) An electron is detected as energy in the ECAL, with a high-transverse-momentum track pointing toward it, and little energy in the HCAL  Muons (2) A muon leaves little energy in the calorimers, has a track, and travels all the way to the muon-detector system outside the calorimeters.

 Hadronically-Decaying Taus (3) The most common hadronic decays of the tau are to a neutrino plus A charged pion One charged pion and one or two pi-zeros  “1-prong” tau : A single charged track that leaves energy in HCAL Any hadronic or EM energy is clustered in a very narrow cone surrounding the charged track Two pions of one charge and a third of the opposite charge  “3-prong” tau : A very narrow jet, with invariant mass no greater than 2 GeV, and with 3 tracks.

 Jets (4) Jets are defined to be groups of particles (tracks and energy bumps in calorimeters) that fit inside a cone in azimuth and pseudo-rapidity space.(cone algorithm) The properties of these jets are expected to correspond closely to the kinematics of the partons in hard process.  Cone size of a jet  Transverse energy (dR ~0.7 : a common choice) (η = ln [cot(θ/2)] : pseudo-rapidity) E T = p T = E sin θ = E (cosh η) -1

 Missing Transverse Energy (6) Missing Et is defined by summing (as a vector) the transverse energy deposited in all of the calorimeter cells (this combines, ideally, the momenta of all photons, electrons, hadronically-decaying taus, and jets) and adding to this the transverse momenta of any muons, whose energy is measured using the muon detection system. The magnitude of the resultant vector is the missing E T.  One of the most important signatures of SUSY with R-parity conservation is large “missing transverse energy”.

 Heavy flavor tagging (b-tagging) Particles of a life-time τ ~ s, such as B 0,+, D 0,+ may travel a distinguishable distance (cτ ~ 100 μm) before decaying into charged tracks, and thus result in a displaced secondary vertex and a nonzero impact parameter The observation, within a jet, of a displaced vertex, tracks with nonzero impact parameter, and/or a single muon all give evidence that a heavy quark was somewhere in the jet. The decays also can produce muons which are close to the jet.

Raw Data Physics Analysis Collider (LHC) Event generator: (1)Feyman diagrams  Production process (CompHEP, Pythia, Hewig, MadGraph etc.) (2) quarks and gluons  jets of hadrons, Decay of short-lived particles (Phythia, Herwig) Detectors (ATLAS, CMS) Detector Simulation (GEANT4) Reconstruction Program (leptons, photons, jets,missing Et) MC raw data Flow chart for Physics analysis

The LHC Olympics New Physics (???) event generator + Pythia (hadronization, decays etc.) PGS (Pretty Good Simulation) [Detector Simulation + Reconstruction] Black box “classics” with 20 fb -1 Black box “uw1” with 25 fb -1 Black box “harvardbb” with 5 & 40 fb -1 t tbar sample diboson sample (WW,WZ,ZZ) GOAL : Figure out what is in each black box !!

An example of a top-antitop pair prodcution event  The 2 nd column : Type of object [0=photon, 1=electron, 2=muon, 3=hadronically-decaying tau, 4=jet, 6=missing transverse energy]  The next three columns : pseudorapidity, the azimuthal angle, tranverse mom.  The next column : the invariant mass for a jet, its charge for not a jet.  The next column : some additional information about the object  The final column : 1 for a “heavy quark” jet 2 b-jets, 2 jets, an isolated muon and missing E T

t tbar b W + μ+ ν bbar W - q q’ 2 b-jets, 2 jets, an isolated muon and missing E T

A Quick Look at diboson sample and black box data with OS-dilepton invariant mass distribution KAIST LHCO team : W.Cho, YGK, C.Park and S.Shin

Di-lepton invariant mass (GeV) Diboson (ZZ,WZ,WW) sample

UW1 black box data Di-electron invariant mass (GeV) Di-muon invariant mass (GeV)

A LHC SUGRA Point with χ 2 -> χ 1 l + l - decay

Harvard black box data

Revealing of the Washington Black Box (M. Strassler)

Next LHC Olympics August(?) 2006 at CERN (?)

Backup

Neutralino mass matrix In the basis : Bino, Wino mass parameters : Higgsino mass parameter : ratio of vev of the two neutral Higgs  Lightest Neutralino = LSP in many cases (WIMP !! )