The NTUHEP TEAM at the CMS Experiment

1. The NTUHEP TEAM at the CMS Experiment • Kai-Feng ChenNational Taiwan University • Presented on February 24th 2011

2. People:5 faculties (Yee Hsiung, Wei-Shu Hou, Minzu Wang, Paoti Chang, Kai-Feng Chen), 5 senior researchers, 5 postdocs, 8 ph.D./12+ master students. • Experimental projects: CMS, Belle/BelleII, Dayabay, KOTO, NuTel. • (Today we will only focus on the CMS experiment, but you are welcome to consult/join all other projects.) • The NTU-CMS team: • 3 senior researches / 3 postdocs / 6 ph.D. / 2 master students.(this is dominant efforts now!) • Regularly we have 7~8 people stationing at CERN. • Detector commitment: ECAL Preshower. • Physics analysis: QCD/underlying events, 4th generation quarks, Higgs to 2 gamma. • Upgrade project: Pixel detector phase I NTUHEP Group Overview

3. nothing but a high energy proton-proton collider. Lake Geneva Mt. Jura CMS The Large Hadron Collider 27 km LHCb Geneva airport My French home NTU apartment ALICE ATLAS CERN main campus le Coq Rouge

4. What people are Doing at the LHC: • The LHC is simply a proton–proton collider at 14 TeV (7 on 7), primary physics targets are: • The origin of mass, the Higgs boson. • What is the dark matter!? Supersymmetry particles? • Matter versus antimatter: the CP violation. • Understanding of the space and time. • and many others... • 7 experiments: • General purpose: ALTAS and CMS. • B-physics: LHCb. • Heavy ion: ALICE. • Forward physics: TOTEM and LHCf. • Magnetic monopole: MoEDAL. • Start its 7 TeV (3.5 on 3.5) run since March 2010. 2 b-tagged jets

5. WHAT PEOPLE DON’T DO AT THE LHC: • We don’t produce any antimatter bomb, that’s for sure. • We don’t destroy the earth with micro black hole. • We don’t construct a superb proton beam to shoot aliens.

6. THE CMS COLLABORATION From Taiwan:NTU and NCU 3170 scientists and engineers (including ~800 students) from 169 institutes in 39 countries.

7. THE CMS DETECTOR Total weight: 14000 tOverall diameter: 15 mOverall length: 28.7 mMagnetic field: 3.8 Tesla

8. Track Track Track w/o track w/o track PARTICLE DETECTION Less calorimeter energy Muon Chamber + + MUON ECAL Shower + ELECTRON HCAL Shower CHARGED HADRON(e.g. proton, pion) + HCAL Shower + NEUTRAL HADRON(e.g. neutron) ECAL Shower + PHOTON JET (e.g. light quark, gluon) + ECAL & HCALShower Lots of tracks

9. Muon chambers Iron flux return The Real Detector View Solenoid Hadron Calorimeter Electromagnetic Calorimeter Silicon Tracker

10. Detector Construction Detectors are mostly constructed first, and then lowering to the “cavern” (100m below the ground level)

11. 3.8T Solenoid More Detector PHOTOs magnetic flux return & muon chamber EM calorimeter crystals Inner silicon tracker Hadron calorimeter

12. Collision Started: March 2010 The first recorded collision event at 7 TeV

13. the “must see”? We expect to see all the known particles in the Standard Model,and maybe the not-yet-discovered Higgs. γ u c t The Standard Model describes:How particles interact;How different particles behave;How the force between particles are manifested.and, maybe explain the origin of mass (if Higgs is there). QUARKS d s b g FORCE CARRIERS e μ τ W LEPTONS νe νμ ντ Z ORIGIN OF MASS? Higgs

14. pT = 3.6 GeV Muon & Electron pT = 2.6 GeV M(μμ) = 3.03 GeV Pin = 2.56 GeV bremtrahlung photons Pout = 1.18 GeV Eseed = 1.26 GeV Etotal = 2.32 GeV

15. Jets = gluon or light Quarks PFJet 1 of 29.9 GeV PFJet 3 of 13.3 GeV PFJet 2 of 24.2 GeV

16. W & Z Rediscovery experimental uncertaintydominated by luminosity error theoretical predictions W and Z measurementsare fully established.

17. The First Golden Top-PAIR EVENT Significant missing energy 2 b-tagged jets 2 clearly identified muons 2 b-tagged jets It cannot be better then a beautiful top-pair!

18. Rediscovery of the SM Slide by J. Pivarski.

19. u c t t′ d s b b′ NTU Physics Analysis Program Underlying Event 4th generation quarks Higgs→γγ?

20. Underlying Event If we just want to study a wheel collide with anther wheel, but you cannot take it out from a car...

21. Underlying Event Analyze the particle density and energy density in the transverse region and compare the results with different theoretical models and tunnings: Jet forwardregion Transverse region backwardregion

22. Underlying Event We published our first paper already! full author list = “The CMS Collaboration”

23. Top Quark ~172 GeV/c2 Proton ~1 GeV/c2 Bottom Quark ~4.2 GeV/c2 t’ Quark ? GeV/c2 b’ Quark ? GeV/c2 4th generation Quarks? Currently we have only three generations (6 quarks) in the Standard Model. Can we have more?

24. Three Generations The Broken Symmetry Kobayashi & Maskawa Received the 2008 Nobel prizein physics, for at least threefamilies of quarks and the picture of CP violation!

25. 4th generations? Discovery of charm quark [Ting (Brookhaven) and Richter (SLAC), 1974] Discovery of top quark [CDF/DØ experiments at Tevatron, 1995] I II III IV u c t t′ d s b b′ Discovery of bottom quark [Lederman(Fermilab), 1977] The original quark model [Gell-Mann & Zweig, 1964] • Adding one more generation of quarks is an obvious extension. • It may resolve some known problems (experimental results ≠ theoretical predictions) in the model. • It have not yet been discovered /fully excluded.

26. 4th generation searches(Our own work!) Only two events failed with the last step selection Zero event found in the signal region CMS Preliminary CMS Preliminary CMS Preliminary CMS Preliminary Full systematic uncertainties included

27. Exclusion Limits • No signal observed in data: we set the exclusion limit at 95% C.L.We use a Bayesian limit for null hypothesis tests, with all the systematic uncertainties included: Observed limit is consistent with the (median) expected limit CMS Preliminary b' production cross section as a function of its mass.

28. FromPreshowertoHiggs Higgs searches are very difficult, but it is not due to the rarity...

29. We all want to work on Higgs! Unless we are well prepared, it’s better not to join the battle too early...

30. Our commitment:The Preshower Detector Endcap ECAL Endcap HCAL Preshower A THIN detector, only 19.52cm!

31. Our commitment:The Preshower Detector NTU+NCU team dominate the Preshower group!

32. γ Single incident (isolated) photon Higgs Why Preshower? γ γ γ Two closely-spaced incident photons γ γ γ Silicon sensors had chosen for improving spatial resolution for endcap ECAL.

33. Why Preshower? It’s a long track, but if we can maintain all the required work very well, we can eventually be part of the Higgs analysis!

34. Next Step:Pixel upgrade The CMS pixel detector is installed in the center of the experiment, and is the first layer of the apparatus after collision.

35. Next Step:Pixel upgrade

36. It’s a huge collaboration of >3000 people. It’s a huge and complex detector. It’s far away from Taiwan. • Pro: • A full international environment. Boost your English (and French?) listening/speaking capability • Enjoy a totally different cultureㄡ • You can always find an expert to help your work and life, and make good friends! • Con: • Lots of people = lots of competitions. • You are not allowed to work alone; collaboration is a must. • It’s far from Taiwan and isolated. (Geneva is not a bad place, but it’s still not as interesting as Taiwan or U.S.) Summary:The Challenge of CMS

37. Hardware track:<now is a great timing – learning with a whole picture!> • Prepare the basic skills/knowledge for pixel detector • Involved in the upcoming pixel module production • Join the pixel installation during 2013 • Detector integration related works • Physics analysis track:<especially if you are already a unix or programming expert> • Basic training: computing + physics + statistics • Grid computing / PC cluster construction and operation • Physics data analysis: hunting for new particles! Summary:What you can contribute A full-trained ph.D. should work on both tracks! You can start your research career earlier!