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Physics at the Tevatron (high P T )

Physics at the Tevatron (high P T ) . Rocío Vilar Cortabitarte Universidad de Cantabria/IFCA. Cosas. I want to thank to people that I took their material to prepare mine : B.Heineman, F.Canelli, O.Gonzalez, B. Klima, G.Bernardis, K.Pitts, S. Seidel, M. Wobisch etc …

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Physics at the Tevatron (high P T )

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  1. Physics at the Tevatron (high PT) Rocío Vilar Cortabitarte Universidad de Cantabria/IFCA

  2. Cosas • I want to thank to people that I took their material to prepare mine : • B.Heineman, F.Canelli, O.Gonzalez, B. Klima, G.Bernardis, K.Pitts, S. Seidel, M. Wobisch etc… • There are many topics that I am not covering in these lectures. I select some topics and analysis as an example of physics at Tevatron (actually, a tiny bit.. ) • More on: http://www-cdf.fnal.gov/physics/physics.html and http://www-d0.fnal.gov/results/index.html • I will talk on high Pt physics, no B-Physics is covered • This is a experimentalist point of view talk !!! Physics at Tevatron

  3. Outline • Accelerators and Detectors (Lecture I): • Chain of Particle Accelerator • Tevatron performance • CDF • D0 • Physics • QCD (Lecture I) • Top Pair and ElectroWeak (Lecture 2) • Single Top, Higgs and New Physics beyond the Standard Model (Lecture 3) Physics at Tevatron

  4. What is Fermilab? Batavia, IL Chicago Physics at Tevatron

  5. What is Fermilab? • In 1989, Fermilab was designated a National Environmental Research Park Physics at Tevatron

  6. What is Fermilab? • Fermilab is a national laboratory located in Batavia, Illinois USA, founded by the Department of Energy. • Fermilab is home to the world’s most powerful particle accelerator, the Tevatron, four miles in circumference. • 1,900 employees include about 900 physicists, engineers and computer professionals. Another 2,300 scientists and students, from across the United States and around the world. • It is open to the sorroundings communities with educational and recreation activities • 6,800-acre Fermilab site contains wetlands, woodlands, grasslands and more than 1,100 acres of reconstructed tall-grass prairie Physics at Tevatron

  7. Chain of Accelerators • pp collider: • 6.5 km circumference • Beam energy: 980 GeV • √s=1.96 TeV • 36 bunches: • Time between bunches: Dt=396 ns • Main challenges: • Anti-proton production and storage: • Stochastic and electron cooling • Irregular failures: • Kicker prefires, Quenches • CDF and DØ experiments: • 700 physicists/experiment Chicago CDF Linac D0 Booster Tevatron P source Main injector & recycler Batavia

  8. Physics at Tevatron

  9. Tevatron Performance ∫ Ldt= 3.1 fb-1 2002 • Integrated luminosity more than 5 fb-1 by now • First years were difficult • March’01-March’02 used for commissioning of detectors • Physics started in March’02 • Now is performing really well • Typical instantaneous luminosity(peak) ≈ 3.3(3.5) · 10 32cm−2 s −1 • Integrated luinosity per week (month) ≈ 75pb− 1 /(260pb−1 ) • Just coming out of 2-month shutdown

  10. CDF • Core detector operates since 1985: • Central Calorimeters • Central muon chambers • Major upgrades for Run II: • Drift chamber: COT • Silicon: SVX, ISL, L00 • 8 layers • 700k readout channels • 6 m2 • material:15% X0 • Forward calorimeters • Forward muon system • Improved central too • Time-of-flight • Preshower detector • Timing in EM calorimeter • Trigger and DAQ

  11. CDF MUON CHAMBERS h = 1.0 CENTRAL HAD CALORIMETER END WALL HAD CAL. CENTRAL EM CALORIMETER SOLENOID h = 2.0 h = 3.0 Silicon Vertex Detector CLC PLUG HAD CAL. PLUG EM CAL. CENTRAL OUTER TRACKER Physics at Tevatron

  12. DØ Detector • Retained from Run I • Excellent muon coverage • Compact high granularity LAr calorimeter • New for run 2: • 2 Tesla magnet ! • Silicon detector • Fiber tracker • Trigger • Readout • Forward roman pots

  13. DØ Detector Physics at Tevatron

  14. Detector Operation • Data taking efficiency about 85% • All components working very well: • 93% of Silicon detector operates, 82-96% working well • Expected to last up to 8 fb-1

  15. Good resolution for track momenta calorimeter energies vertex Detector Performances Physics at Tevatron

  16. Particle detected There are only few particles that we are able to detect at the end of the day Electrons Muons Photons Jets Some light mesons (kaons, pions) Experimental Techniques in High Energy

  17. Processes and Cross Sections Events/fb-1 • Cross section: • Total inelastic cross section is huge • Used to measure luminosity • Rates at e.g. L=1x1032 cm-2s-1: • Total inelastic: 70 MHz • bb: 42 kHz • Jets with ET>40 GeV: 300 Hz • W: 3 Hz • Top: 25/hour • Trigger needs to select the interesting events • Mostly fighting generic jets! 1012 Jet ET>20 GeV 1010 109 Jet ET>40 GeV 108 2.8x106 2.5x105 7x103 3x103 300

  18. Triggering at hadron colliders The trigger is the key at hadron colliders CDF Detector Hardware tracking for pT1.5 GeV 1.7 MHz crossing rate Muon-track matching 42 L1 buffers Dedicated hardware L1 trigger Electron-track matching Missing ET, sum-ET 25 kHz L1 accept Silicon tracking Hardware + Linux PC's 4 L2 buffers L2 trigger Jet finding, improved Missing ET Refined electron/photon finding 800 Hz L2 accept DØ trigger: L1: 1.6 kHz L2: 800 Hz L3: 50 Hz Linux farm (200) L3 farm Full event reconstruction 200 Hz L3 accept disk/tape Physics at Tevatron

  19. Unprescaled triggers for primary physics goals Examples: Inclusive electrons, muons pT>20 GeV: W, Z, top, WH, single top, SUSY, Z’,Z’ Dileptons, pT>4 GeV: SUSY Lepton+tau, pT>8 GeV: MSSM Higgs, SUSY, Z Also have tau+MET: W->taunu Jets, ET>100 GeV Jet cross section, Monojet search Lepton and b-jet fake rates Photons, ET>25 GeV: Photon cross sections, Jet energy scale Searches (GMSB SUSY) Missing ET>45 GeV SUSY ZH->vvbb Prescale triggers because: Not possible to keep at highest luminosity Needed for monitoring Prescales depend often on Lumi Examples: Jets at ET>20, 50, 70 GeV Inclusive leptons >8 GeV B-physics triggers Backup triggers for any threshold, e.g. Met, jet ET, etc… At all trigger levels Typical Triggers and their Usage single electron trigger CDF Rate= 6 Hz at L=100x1030 cm-2s-1 Physics at Tevatron

  20. Trigger Operation • Aim to maximize physics at trigger level: • Trigger cross section: • Nevent/nb-1 • Independent of Luminosity • Trigger Rate: • Cross Section x Luminosity • Luminosity falls within store • Rate also falls within store • 75% of data are taken at <2/3 of peak luminosity • Use sophisticated prescale system to optimize bandwidth usage • Trigger more physics!

  21. Accelerators and Detectors (Lecture I): Chain of Particle Accelerator Tevatron performance CDF D0 Physics QCD (Lecture I) Top Pair and ElectroWeak (Lecture 2) Single Top, Higgs and New Physics beyond the Standard Model (Lecture 3) Physics at Tevatron

  22. The Proton • It’s complicated: • Valence quarks • Gluons • Sea quarks • Exact mixture depends on: • Q2: ~(M2+pT2) • xBj: fractional momentum carried by parton • Hard scatter process: p Q2 X xBj p

  23. Parton Kinematics pdf’s measured in deep-inelastic scattering • Examples: • Higgs: M~100 GeV • LHC: <xp>=100/14000≈0.007 • TeV: <xp>=100/2000≈0.05 • Gluino: M~1000 GeV • LHC: <xp>=1000/14000≈0.07 • TeV: <xp>=1000/2000≈0.5 • Parton densities rise dramatically towards low x • Results in larger cross sections for LHC, e.g. • factor ~1000 for gluinos • factor ~40 for Higgs • factor ~10 for W’s

  24. Tevatron vs LHC • Compare to LHC • Cross sections of heavy objects rise much faster, e.g. • top cross section • Jet cross section ET>100 GeV • Relative importance of processes changes • Jet background to W’s and Z’s • W background to top • backgrounds to Higgs

  25. Hadron-Hadron Collisions

  26. Hadron-Hadron Collisions

  27. Hadron-Hadron Collisions

  28. Hadron-Hadron Collisions

  29. Hadron-Hadron Collisions

  30. Hadron-Hadron Collisions

  31. Hadron-Hadron Collisions

  32. Hard QCD Processes CTEQ6.1 gluon uncertainty high pT  hard partonic scattering kinematic plane • Sensitive to: • strong coupling constant • proton’s parton content  unique sensitivity to high-x gluon • dynamics of interaction- validity of approximations (NLO, LLA, …)- QCD vs. new physical phenomena

  33. Kinematic Constraints and Variables • Transverse momentum, pT • Particles that escape detection (<3o) have pT≈0 • Visible transverse momentum conserved ∑I pTi≈0 • Very useful variable! • Longitudinal momentum and energy, pz and E • Particles that escape detection have large pz • Visible pz is not conserved • Not so useful variable • Angle: • Polar angle  is not Lorentz invariant • Rapidity: y • Pseudorapidity:  For M=0

  34. Physics Objects Jets (all flavors) Heavy Flavor

  35. Physics Objects Jets (all flavors) Photons W/Z Bosons Heavy Flavor

  36. Physics Objects Jets (all flavors) Photons W/Z Bosons Heavy Flavor Multi-Parton Interactions / Underlying Event

  37. QCD Processes and Cross section • Jet Production • Photon Production (+ Jet) • Vector Boson + Jet(s) • Double Parton Interactions • Underlying Event

  38. Hadron-hadron collisions are messy • Energy flow: project the energy flow on to the (,) plane “Lego plot” f h Physics at Tevatron

  39. But become simple at high energies largest high pT cross sectionat a hadron collider  highest energy reach • Jets are unmistakable: Unique sensitivity to new physics: - new particles decaying to jets, - quark compositeness, - extra dimensions, - …(?)… xT f h In absence of New Physics theory @NLO is reliable (±10%)  Precision phenomenology - sensitivity to PDFs  high-x gluon- sensitive to Physics at Tevatron 39

  40. What are jets? jet Jet p g colorless states - hadrons Fragmentation process p outgoing parton Hard scatter jet • The hadrons in a jet have small transverse momentum relative to the parent parton’s direction and the sum of their longitudinal momenta is roughly the parent parton momentum • Jets are the experimental signatures of quarks and gluons and manifest themselves as localized clusters of energy Physics at Tevatron

  41. Jet Triggering • Unlike most physics at hadron colliders, the principal background for jets is other jets • because the cross section falls steeply with ET, lower energy jets mismeasured in ET often have a much higher rate than true high ET jets (“smearing”) • Multi-level trigger system with increasingly refined estimates of jet ET • Large dynamic range of crosssection demands that many trigger thresholds be used e.g. • 15 GeV prescaled 1/1000 • 30 GeV prescaled 1/100 • 60 GeV prescaled 1/10 • 100 GeV no prescale DØ L3 simulation Factor of ~ 30 rate reduction Physics at Tevatron

  42. Jets: from parton to detector level Quark and gluon jets (identified to partons) can be compared to detector jets, if jet algorithms respect collinear and infrared safety(Sterman&Weinberg, 1977) Jet • Jets at the particle (hadron) level • Jets at the “detector level” hadrons fragmentation process outgoing parton Hard scatter Particle Shower Calorimeter hadrons The idea is to come up with a jet algorithm which minimizes the non-perturbative hadronization effects fragmentation process outgoing parton Hard scatter Physics at Tevatron

  43. Jet Algorithms • The goal is to be able to apply the “same” jet clustering algorithm to data and theoretical calculations without ambiguities. • Jets at the “Parton Level” • i.e., before hadronization • Fixed order QCD or (Next-to-) leading logarithmic summations to all orders • Traditional Choice at hadron colliders: cone algorithms (jetclu, siscone) • Jet = sum of energy within R2 = 2 + 2 • Traditional choice in e+e–: successive recombination algorithms • Jet = sum of particles or cells close in relative kT Physics at Tevatron

  44. Jet Energy Calibration 1. Establish calorimeter stability and uniformity • pulsers, light sources • azimuthal symmetry of energy flow in collisions • muons 2. Establish the overall energy scale of the calorimeter • Testbeam data • Set E/p = 1 for isolated tracks • momentum measured using central tracker • EM resonances (0 , J/,  and Z  e+e–) • adjust calibration to obtain the known mass 3. Relate EM energy scale to jet energy scale • Monte Carlo modelling of jet fragmentation + testbeam hadrons • CDF • ET balance in jet + photon events • DØ Physics at Tevatron

  45. Why Measure Cross Sections? • They test QCD calculations • They help us to find out content of proton: • Gluons, light quarks, c- and b-quarks • A cross section that disagrees with theoretical prediction could be first sign of new physics: • E.g. quark substructure (highest jet ET) Physics at Tevatron

  46. Why Measure Cross Sections? • They test QCD calculations • They help us to find out content of proton: • Gluons, light quarks, c- and b-quarks • A cross section that disagrees with theoretical prediction could be first sign of new physics: • E.g. quark substructure (highest jet ET) • They force us to understand the detector Physics at Tevatron

  47. Why Measure Cross Sections? • They test QCD calculations • They help us to find out content of proton: • Gluons, light quarks, c- and b-quarks • A cross section that disagrees with theoretical prediction could be first sign of new physics: • E.g. quark substructure (highest jet ET) • They force us to understand the detector • No one believes us anything without us showing we can measure cross sections Physics at Tevatron

  48. Luminosity Measurement • Measure events with 0 interactions • Related to Rpp • Normalize to measured inelastic pp cross section • Measured by CDF and E710/E811 • Differ by 2.6 sigma • For luminosity normalization we use the error weighted average • CDF and DØ use the same • Unlike in Run 1… CDF pp (mb) E710/E811

  49. Inclusive Jets pT (GeV) pT (GeV) Phys. Rev. Lett. 101, 062001 (2008) Phys. Rev. D 78, 052006 (2008) • benefit from: • high luminosity in Run II • increased Run II cm energy  high pT • hard work on jet energy calibration steeply falling pT spectrum: 1% error in jet energy calibration  5—10% (10—25%) central (forward) x-section

  50. Inclusive Jets • high precision results • consistency between CDF/D0 • well-described by NLO pQCD • experimental uncertainties: smaller than PDF uncertainties!! •  sensitive to distinguish between PDFs CTEQ6.5M PDFs • data are used in PDF fits: • included in MSTW2008 PDFs • at work: forthcoming CTEQ PDFs pT (GeV)

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