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Large Hadron Collider

Large Hadron Collider

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Large Hadron Collider

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  1. Large Hadron Collider Physics at the Energy Frontier • Brief introduction to particle physics • Bear with me if you already know this (10’) • Probing the Quantum Universe – the Instruments • The LHC Machine and The CMS Experiment • Slide show of engineering LHC/CMS (10’) • 2010 Results (40’) • Establishing Standard Model @ LHC Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  2. A Brief History of Time Electro-weak Era Proton & Neutron Era Nuclear Era Galaxies Formation Today Quantum Gravity Era Grand Unification Era Atoms and Light Era Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  3. Particles & The Universe • Particle physics experiment results are needed for understanding our microcosm and the cosmos itself • What is mass? Where has all the Anti-matter gone? • What is dark matter? … Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  4. Probing Deeper • As you probe deeper – i.e., reach higher energies – new worlds open up – quantum relativistic world! Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  5. Down to Quarks Rutherford Scattering with high energy electrons Stanford Linear Accelerator Center Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  6. Matter Particles All of these matter particles also have corresponding antimatter particles Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  7. Interactions Between Particles CERN - Geneva Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  8. Particle Interactions Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  9. The Particle Zoo Many types and decays Detection • Interactions with matter • Measure momentum bybending tracks inmagnetic fields • Combinations of measured momenta Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  10. The Elusive Higgs Weak force is weak because W and Z bosons are heavy • Relativistic quantum theory does not work with simple mass terms in the theory • Higgs Mechanism was invented to provide mass for weak bosons by adding a new field with four degrees of freedom • Three of those degrees of freedom are equivalent to having masses for W and Z • The left over degree of freedom is the scalar higgs boson in the Standard Model • Higgs couplings to leptons and quarks provide them masses • The hunt is on to find the Higgs since the 80s! The higgs bosons of masses up to 114 GeV are excluded • For theory to make sense higgs mass should be < ~1 TeV • The LHC is designed to find the higgs if it exists Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  11. Problems of Standard Model Higgs self energy corrections • Higgs couples to itself • However, these self energy corrections are divergent • Up to about 1 TeV energy scale this is not a problem • Therefore, new physics should show up at ~few TeV Super-symmetry • Corrections due to loops of fermions (leptons and quarks) and bosons (W, Z) come with opposite sign • What if there are equal number of fermions and bosons in the real theory at high masses (~few TeV)? • This could solve the problem of higgs divergences  Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  12. A new physics theory which doubles known particles again – but the new particles have very large mass LHC may be able to produce them Supersymmetry Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  13. The Large Hadron Collider 2010 2001011 3.5 TeV 1032 cm–2s–1 40 MHz 106 Hz Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  14. CMS : A Giga-Pixel Camera Snaps a billion pictures of quantum interactions a second Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  15. Particle Detection in CMS Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  16. Missing Transverse Energy Initial particles (protons) are going in and out of the screen in this picture Net momentum initially is zero in this XY-plane Remnants after the collision should also add up to zero momentum Imbalance seen when there are non-interacting (neutrinos or may be dark matter!) particles. Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  17. Low PTg, e, m Low PT leptons Low PT B, t jets Missing ET Multiple low PT objects ~ give up to dedicated experiment, LHCB High PT leptons and photons Multi particle and jet events Physics in LHC Era Detector Measurables • Electroweak Symmetry Breaking Scale • Higgs discovery and higgs sector characterization • Quark, lepton Yukawa couplings to higgs • New physics at TeV scale to stabilize higgs sector • Spectroscopy of new resonances (SUSY or otherwise) • Find dark matter candidate • Multi-TeV scale physics (loop effects) • Indirect effects on flavor physics (mixing, FCNC, etc.) • Bs mixing and rare B decays • Lepton flavor violation • Rare Z and higgs decays • Planck scale physics • Large extra dimensions to bring it closer to experiment • New heavy bosons • Blackhole production Do Low PT Physics in 2010 Low  40 GeV Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  18. The LHC Trigger Challenge 1% Level Challenge in 2010 !! • Physics at EWSB scale • 115 < Mhiggs < 250 GeV • Decays to gg, WW*, ZZ* • 2-g PT~20 GeV, Lepton PT ~ 40 GeV • TeV scale supersymmetry • Multiple leptons, jets and LSPs (missing PT), HT ~ 300 GeV • QCD Background • Jet ET ~ 250 GeV, rate = 1 kHz • Jet fluctuations  electron BG • Decays of p, k, B  muon BG • Technical challenges • 40 MHz input  fast processing • 100 Hz output  physics selection • 109 events per year  ≤102 higgs events Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  19. CMS Trigger & DAQ System • Reduces 109 Hz interaction rate to 300 Hz data rate • Level 1 Trigger • Operates at 40 MHz crossing frequency. • Latency < 3.2 μs • 100 KHz output rate • High Level Trigger • Software trigger with online computer farm. • Analyzes full event data • Reduces to final 300 Hz storage rate. Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  20. Multi Level Trigger Strategy • Level 1 • Coarse object identification • Limited isolation Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  21. LHC and CMS operations About 47pb-1 delivered by LHC and ~43pb-1of data collected by CMS. Overall data taking efficiency ~92%. 6pb-1of data integrated in a good fill. Excellent performance in coping with more than 5 order of magnitude increase in instantaneous luminosity. L≈ 2x1032cm-2s-1 L≈ 1027cm-2s-1 Average operational channels per CMS sub-system still >99%. Quality of the data for physics ~80% (likely 85% after re-reco) Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  22. Established the Standard Model at 7TeV Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  23. Particle PT, Rapidity Spectra arXiv:1005.3299v2 [hep-ex] 6 Jul 2010 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  24. Charged Particle Production arXiv:1011.5531v1 [hep-ex] 24 Nov 2010 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  25. Two Particle Correlations arXiv:1009.4122v1 [hep-ex] 21 Sep 2010 Unexpected correlations seen for high multiplicity events Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  26. Jet PT, Rapidity Spectra CMS PAS QCD-10-012 6 Jul 2010 Core Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  27. 3rd Jet PT, Rapidity Spectra CMS PAS QCD-10-012 6 Jul 2010 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  28. Dijet Angular Correlations CMS PAS QCD-10-015 20 Jul 2010 Rapidity Azimuthal Angle Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  29. Jet Structure CMS PAS QCD-10-014 20 Jul 2010 Core Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  30. Isolated Photon Spectrum arXiv:1012.0799v1 [hep-ex] 3 Dec 2010 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  31. Resonances at 7 TeV Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  32. J/Ψ Production arXiv:1011.4193v1 [hep-ex] 18 Nov 2010 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  33. Upsilon Production arXiv:submit/0170551 [hep-ex] 26 Dec 2010 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  34. B+ψK Production arXiv:submit/0172289 [hep-ex] 30 Dec 2010 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  35. b-Jet Production CMS PAS BPH-10-009 23 Jul 2010 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  36. Weak Bosons at 7 TeV After lepton selection Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  37. EWK Cross-sections arXiv:1012.2466v1 [hep-ex] 11 Dec 2010 W Z W/Z W+/W- Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  38. Top: dileptons+jets L=2.9pb-1 ee/em/mm Submitted to PL-B arXiv:1010.5994 First top cross section measurement at LHC. σ(pp → t¯t) = 194 ± 72(stat.) ± 24(syst.) ± 21(lumi.) pb. Consistent with NLO prediction of 157.5 (+23.2 −24.4) pb for a top quark mass of mt = 172.5 GeV/c2 • Full selection applied: Z-bosonVeto, |M(ll)-M(Z)|>15 GeV • MET >30 (20) GeV in ee,mm, (em); N(jets)≥2 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  39. Dijet Resonances arXiv:1010.0203v2 [hep-ex] 18 Nov 2010 Are there strongly interacting new particles at high masses? No, not below ~2.4 TeV for string resonances – lower for other models Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  40. Lepto-Quarks? arXiv:1012.4031v1 [hep-ex] 17 Dec 2010 Leptoquarks are particles with both lepton &quark degrees of freedom predict in many new physics theories. Are they produced at LHC? First generation LQs decay to electron + jet Masses below 384 GeV are ruled out @ 95% cl if BR to electron + jet is 100% – further coverage with eqνeq channel in near future Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  41. Lepto-Quarks? arXiv:1012.4033v1 [hep-ex] 17 Dec 2010 Leptoquarks are particles with both lepton &quark degrees of freedom predict in many new physics theories. Are they produced at LHC? Second generation LQs decay to muon + jet Masses below 394 GeV are ruled out @ 95% cl if BR to muon + jet is 100% – further coverage with μqνμq channel in near future Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  42. Microscopic Blackholes arXiv:1012.3375v1 [hep-ex] 15 Dec 2010 In theories with large extra dimensions, microscopic blackholes with masses in TeV range can be produced. They immediately decay to many pairs of quarks, leptons and photons. Are they produced at LHC? If the colliding particles get closer than rSblackhole may be produced Sum of transverse energies (ST) of decay products of the collision is a measure of blackhole production. Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  43. ST Distributions arXiv:1012.3375v1 [hep-ex] 15 Dec 2010 ST~1.4 TeV, N=10 Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  44. Limits on Blackhole Masses arXiv:1012.3375v1 [hep-ex] 15 Dec 2010 Blackhole masses of 3 to 4.5 TeV for 2, 4, or 6 extra dimensions are excluded Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  45. New Charged Bosons, W’ arXiv:submit/ 0171626 [hep-ex] 29 Dec 2010 New Physics Theories predict bosons of higher masses. Are there W’ bosons? After requiring high PT>30 GeV electron No W’s decaying to electron + neutrino < 1.36 TeV MW’ at 95% c.l. Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  46. Stopped Gluinos arXiv:1011.5862v1 [hep-ex] 26 Nov 2010 What about SUSY? SUSY parameter space is vastIn some regions of parameter space gluinos may be quasi stable and stop in CMS We looked for their subsequent decay (energy deposits) in no collisions period No stopped gluinos seen: 13-orders of lifetime for ~360 GeV Mgluino Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  47. Heavy Stable Charged Particles CMS PAS EXO-10-004, 23 July 2010 Heavy Charged Particles with lifetimes greater than transit time through detector occur in many new physics models, e.g., SUSY stau or stop Their signature is that of minimum ionizing particle like the muon, but moving slower through the detector (time profile, energy deposition dE/dx) Sridhara Dasu (Wisconsin) - IIT-B Colloquium

  48. Summary LHC is off to a wonderful start in 2010 • The detectors and accelerator are working well • The Standard Model is well established at 7 TeV scale • Several strong and electro-weak processes are measured already Early searches for strongly produced new physics • Going beyond the Tevatron (2 TeV) reach • No deviations from the Standard Model are seen Searches for higgs boson(s) and new physics relevant to electro-weak scale are beginning • Look forward to several fb–1 data at 8 TeV in 2011-2012 • Discoveries are around the corner – stay tuned Sridhara Dasu (Wisconsin) - IIT-B Colloquium