LTE World Summit 2012 Bill lesier gits-research-masterclass-2_thurs
CMS Masterclass 2012
description
Transcript of CMS Masterclass 2012
![Page 1: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/1.jpg)
CMS Masterclass 2012
![Page 2: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/2.jpg)
It’s the dawn of an exciting age of new discovery in particle physics!
At CERN, the LHC and its experiments are underway.
ATLAS and CMS, the Compact Muon Solenoid, have been taking data. The first job is to confirm how the detector data corresponds to our understanding we call the Standard Model. Secondly, the task is to look for new phenomena.
The LHC and New Physics
![Page 3: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/3.jpg)
The LHC is buried ~100 m below the surface near the
Swiss-French border.
The LHC and New Physics
where beams cross and some particles collide
![Page 4: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/4.jpg)
Generic DesignCylinders wrapped around the beam pipeFrom inner to outer . . . Tracking Electromagnetic calorimeter Hadronic calorimeter Magnet*Muon chamber
* location of magnet depends on specific detector design
Detector Design
![Page 5: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/5.jpg)
Detector Tracks
![Page 6: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/6.jpg)
If each beam proton has energy 3.5 TeV.... •The total collision energy is 2 x 3.5 TeV = 7 TeV.•But each particle inside a proton shares only a portion.•So a newly created particle’s mass must be smaller than the total energy.
Energy & Particle Mass
![Page 7: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/7.jpg)
Particle Decays
The collisions create new particles that promptly decay. Decaying particles always produce lighter particles.
Conservation laws allow us to see patterns in the decays.
Try to name some of these conservation laws.
film
![Page 8: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/8.jpg)
Background Events
Often, quarks are scattered by proton collisions.
As they separate, the binding energy between them converts to sprays of new particles called jets. Electrons and muons may be included in jets.
Software can filter out events with jets beyond our current interest.
![Page 9: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/9.jpg)
W and Z Particles
We are looking for the mediators of the weak interaction: •electrically charged W + boson,•the negative W - boson,•the neutral Z boson.
Unlike electromagnetic forces carried over long distances by massless photons, the weak force is carried by massive particles which restricts interactions to very tiny distances.
![Page 10: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/10.jpg)
The W bosons are responsible for radioactivity by transforming a proton into a neutron, or the reverse.
Z bosons are similarly exchanged but do not change electric charge.
Collisions of sufficient energy can create W and Z or other particles.
W and Z Particles
![Page 11: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/11.jpg)
The W bosons are responsible for radioactivity by transforming a proton into a neutron, or the reverse.
Z bosons are similarly exchanged but do not change electric charge.
Collisions of sufficient energy can create W and Z or other particles.
W and Z Particles
![Page 12: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/12.jpg)
W and Z Decays
Because W and Z only travel a tiny distance before decaying, CMS does not “see” W or Z bosons directly.
CMS can detect :• electrons • muons
CMS can infer:• neutrinos from “missing energy”
![Page 13: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/13.jpg)
iSpy-online
![Page 14: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/14.jpg)
Use new data from the LHC in iSpy to test performance of CMS:• Can we distinguish W from Z candidates?
Today’s Task
![Page 15: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/15.jpg)
• Can we calculate the e/m ratio?• Can we calculate a W+/W- ratio for CMS?
Today’s Task
![Page 16: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/16.jpg)
• Can we make mass plot of Z candidates?
Today’s Task
![Page 17: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/17.jpg)
Try some real events
Open iSpy-online with:- Firefox ver 5 or greater- Chrome- Safari
Open iSpy-dvd with:- Firefox ver 7 or greater
![Page 18: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/18.jpg)
Recording event data
![Page 19: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/19.jpg)
Histogram Review
Well-defined peak Outliers: lower frequency Where is the peak?What is the width?Is the “mass” precise?
There are a variety of histogram tools. The one above is provided by Shodor:Click to go to Shodor.Org histogram tool
![Page 20: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/20.jpg)
Histogram Review
Where is the peak?What is the width?Where are the outliers?
Not all histograms have same precision
Click to go to Dan Karmgard’s Histogram Builder
![Page 21: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/21.jpg)
Histogram Review
Multiple peaks:Poor resolution of a single
peak, ormultiple signals?
In particle physics, this could reveal several particles, ora combination of background noise plus one or more actual particles under study.
Click if you wish to go to the Norwegian Masterclass site used to make this histogram.
![Page 22: CMS Masterclass 2012](https://reader036.fdocuments.us/reader036/viewer/2022062323/5681613d550346895dd0a3e0/html5/thumbnails/22.jpg)
“Science is nothing but developed perception, interpreted intent, common sense rounded out and minutely articulated.” George Santayana
• Indirect observations and imaginative, critical, logical thinking can lead to reliable and valid inferences.
• Therefore: work together, think (sometimes outside the box), and be critical of each other’s results to figure out what is happening.
Form teams of two. Each team analyzes 100 events. Talk with physicists about interpreting events. Pool results.
Keep in Mind . . .