# Presentation: 238693

## Detector Basics

**2.1 SM Particles - Mapping into Detector Subsystems**
**2.2 Tracking and b Tags**
**2.3 EM Calorimetry - e and ******
**2.4 Hadron Calorimetry - Jets of q and g and neutrino (missing Et)**
**2.5 Muon Systems**
**2.6 Complex Event Topologies in D0 and CDF**
**2.7 Fragmentation, Minimum Bias Events**

## CMS Detector Subsystems

**CMS Detector Subsystems**

**CMS Detector Subsystems**

**Si Tracker**
**     ****pixels**
**     ****strips**
**Crystal ECAL**
**HCAL**
**     ****barrel**
**     ****outer**
**     ****endcap**
**     ****forward**
**4 T Magnet**
**Muon**
**     ****barrel**
**     ****endcap**

**Tracking**
**Calorimetry**

## CMS Detector

## The Standard Model of Elementary Particle Physics

**A reminder of the fundamental particles in the SM. The strongly interacting particles are gluons (g) and quarks (u,c,t,d,s,b). The EM particles are photons and charged leptons (********, e, ********, ********). The weakly interacting particles are the EW gauge bosons, W and Z and the neutrinos. ********e****, ************,  ************.**

**J = 1**

**g,********, W****+****,Z****o****,W****-**

**Force Carriers**

**J = 1/2**

**u**
**d**

**c**
**s**

**t**
**b**

**e**
******e**

****
********

****
********

**Q/e=**

**2/3**
**-1/3**

**1**
**0**

**Quarks**

**Leptons**

## SM Particle Detection 

**Detect SM particles by way of their characteristic interactions**

**quarks**

## Detector Subsystems

**Detector Subsystems**

**For trigger types use the detector subsystems in combination to do particle Id.**

## CMS - All Si tracking

**3 layers of Si pixels - space points**
**+**
**> 200 m****2 **** of Si strips**
**--------------**
**high luminosity requires highest rate detector capabilitiy**

**Measure bend angle in magnetic field ~ 1/P**

## Heavy Flavor Tags - b

******(c********) ~ (0.48 mm) ******** for b quarks. Since Higgs couples to mass, identification of heavy quarks, ********~M****5****, is important - “b tagging”.**

## Weak Decays of Quarks, Leptons

**V-A means particles are L, anti-particles are R**

## COMPHEP b Decay

## Tevatron Tagging Efficiency

**Limited at lower momenta by multiple scattering**

## EM Cascade

**Electrons and photons make a characteristic “shower” on a short distance scale - the radiation length-  in high Z materials.**

**Needed depth ~ 20Xo**
**Ec = critical energy**
**                              ****stochastic term**

## CMS ECAL 

**CMS ECAL **

**Precision Fully Active Detection Medium**

**The W gauge bosons can decay into quark-antiquarks, or into lepton pairs. For 2 body decays, Et ~ M/2. There can also be radiation associated with the W, gluons which evolve into jets.**

**W --> e + ******** at the Tevatron**

**E****T**** ~ M****W****/2 ~ 40 GeV - “Jacobean peak”**

**E****T**

****

**y**

## COMPHEP – W Decays

## Calibration in Situ

**Get data sets with photons and look at resonant peaks**

**Hadrons - Basic Parameters**

## Tower Size from Dijet Mass Resolution

**Jet “cone” of R ~ 0.5 ==> ~ 100 “towers” in the cone to evaluate jet substructure. (Chpt. 3)**
**e.g.  1 TeV  H --> ZZ**
**P****Z**** ~ 500 GeV, Z --> JJ**
**P****TJ**** ~ 45 GeV**
**JJ opening angle ~ 0.2**
**CMS tower size ~ 0.087**

**CMS Hadronic CALorimeter (HCAL)**

## Tile/WLS Fiber Calorimetry

**WLS technique gives a “hermetic” readout. Cool the light from blue to green , reducing the photon energy by dE. This allows an area compression factor in the readout of ~ exp(dE/kt). Defeat Liouville’s theorum.**

## Quality of Construction

**Sampling Uniformity and dE/E**

**Quality of Construction**

**Relation of constant term to the**
**r.m.s. of the sampling medium**
**(scintillator tiles)**
****** ****constant term < 3 %**
**since uniformity < 7 %**
**was achieved**

## Muons and in Situ Calibration

**Because of the effect of the B field, HCAL must make an in situ, field on calibration.**
**HCAL can be used for muon ID if the muon is isolated. A muon deposits ionization energy corresponding to ~ 3 GeV.**

## HCAL “Wedges” at CERN – Depth

**HCAL “Wedges” at CERN – Depth**

**Note inert absorber (brass) and slots for sampling calorimetry active layers (scint)**

**CMS - Leakage and “Catcher”**

**Data taken with prototype wedges in a CERN test beam**

## Angular Extent and “Tag Jets”

**Angular Extent and “Tag Jets”**

**WW Fusion**
**W W --> H**

**CMS calorimetry extends to |********| = 5 to cover the region of “tag jets”.**

**Vector boson fusion model**

## W --> e + , Missing Et

**Missing E****T**** is “back to back” with the e from W decay. It is assumed that the partons in the initial state have small intrinsic E****T**** ~ ******** ~ 0.2 GeV, scale where QCD becomes strong**

## A W + Z --> e e e  Candidate - D0

**WZ ~ at rest in the c.m.**
**Z --> ee**
**W --> e**** **

## A WZ-> ee CDF Candidate

## CMS Muon System

**Measure the muon momentum vector in the tracker. Then filter out all hadrons and remeasure the muon in the flux return of the magnet. Multiple redundant measurements are needed in searching for rare processes.**

## Inclusive Muons 

**A given single final state particle can have many sources. Muons from B dominate a low P****T****, while W,Z dominate for P****T**** ~ M/2. At still higher P****T**** there are no known sources (W’  ?)**

## Calibration – D0 Run I

**Resolution in the Fe toroids is multiple scattering limited.**

## Calibration – CDF Run II

## Hadronization

**Quarks and gluons have color while hadrons ( the asymptotic states ) are colorless. The process of “hadronization” occurs at energy scales where QCD is strong ~ ******** so that perturbation theory cannot be used. This makes direct experimental QCD predictions difficult.**

## The scattering of quarks inside the proton leads to a "jet" of particles traveling in the direction of, and taking the momentum of, the parent quark. Since there is no initial state Pt, the 2 quarks in the final state are "back to back" in azimuth.

**Dijet CDF Event at the Tevatron**

**E****T**

****

****

## D0 Dijet Event – Tevatron Run II

## Dijet D0 Event - Total 1 TeV

**Clearly, composite scales with subenergies near the pp energy can be probed at the LHC and the Tevatron.**

## Jet Calibration - Transverse Balance

**The initial state E****T**** due to partons is assumed to be small and ~ ********. Thus, the final state has no net E****T****. Hence W, Z are produced with E****T**** = 0 and jets are “back to back” in azimuth. This fact is used in “jet balancing” for calibration**

## The CDF detector has 3 main detector systems; tracking - Si + ionization in a magnetic field,  scintillator sampling calorimetry, (EM - e, and HAD - h), and ionization tracking for muon measurements. Missing energy indicates  in the final state.Si vertex detectors allow one to identify b and c quarks in the event.

**  ****A CDF Event at the Tevatron**

## The D0 detector has 3 main detector systems; ionization tracking,liquid argon calorimetry ( EM , e , and HAD , jets ,), and magnetized steel + ionization tracker muon ,  , detection/identification. This event has jets, a muon, an electron and missing energy , .

**A FNAL Collider (D0) Event**

## Jet Energy resolution

**A jet fragments into many soft hadrons – D(z)**

**If stochastic dominates**

**If constant term dominates**

**Dijet mass - stochastic**

## LEP – W Mass Resolution

**dM ~ 2.5 GeV**
**dM/M ~ 0.035**
**But the initial state constraints can be used. Worse resolutions at the Tevatron and LHC (Chpt. 4)**

## Underlying Event – “minbias”

**No real fundamental theory. Extrapolate as ln(s). At the LHC <Pt> ~ 0.6 GeV and density ~ 9 (charged ~ 6).**

## Pileup and Jet Recognition

**At high luminosity, any jet search cone will have ~ 25 GeV of Et due to pileup. Triggers and reconstruction need to look at transverse flow within a cone to select real jets, which have a “core” as opposed to ~ uniform pileup. Jets have a limited k****t ****and a D(z) with z****max**** ~ 0.2, <n> ~ ln(E****T****) - see Chpt. 3.**