1. M. Garcia-Sciveres July 2002 ATLAS A Proton Collider Detector M. Garcia-Sciveres Lawrence Berkeley National Laboratory

2. M. Garcia-Sciveres July 2002 2 Outline Physics motivation - why are we doing this? Proton Collisions Collider Detectors The ATLAS detector The Pixel Detector ATLAS movie

3. M. Garcia-Sciveres July 2002 3 Physics Motivation Electrons account for everything we experience- almost We know a lot about electrons There’s one thing we can “feel” that has nothing to do with electrons- mass We know very little about mass at a fundamental level The purpose of ATLAS is to discover fundamental things about mass. What is is really?

4. M. Garcia-Sciveres July 2002 4 Standard Model

5. M. Garcia-Sciveres July 2002 5 Accelerators o Lawrence’s First Cyclotron 5in. diameter 0.8 MeV Bevatron ~150ft dia. 6,000 MeV Fermilab Tevatron (present highest energy) ~1 mile diameter 1,000,000 MeV on 1,000,000 MeV Large Hadron Collider (under Construction) ~5 mile diameter 7,000,000 MeV on 7,000,000 MeV

6. M. Garcia-Sciveres July 2002 6 Aerial View of the LHC Site Circumference of 27 km Main CERN Site

7. M. Garcia-Sciveres July 2002 7 LHC Underground Layout

8. M. Garcia-Sciveres July 2002 8 LHC Magnets Superconducting dipoles and other magnets guide and focus the proton beams and bring them into collision at multiple points around the ring. Magnets are cooled by superfluid Helium at 1.9 o K to achieve the highest possible magnetic field with the “standard” superconductor used.

9. M. Garcia-Sciveres July 2002 9 A Toroidal LHC ApparatuS Calorimeters Inner Tracking Superconducting Toroids Muon Detectors ATLAS Tall person Superconducting Solenoid LHC beam pipe

10. M. Garcia-Sciveres July 2002 10 International Collaboration 2000 scientists 150 institutions 35 countries

11. M. Garcia-Sciveres July 2002 11 LHC Experimental Environment A proton Microscope Each proton can(crudely) be thought of as a collection of constituents/virtual particles. The “hard”, high energy(actually transverse momentum) collisions of these constituents are of interest to probe the smallest distances and to produce the highest mass new particles The “soft” debris is background to the interesting, hard collisions.

12. M. Garcia-Sciveres July 2002 12 What Comes out of a Collision? Hadronic Jets (pions, kaons etc.) More photons Heavy Quark hadrons Electrons Muons Taus Neutrinos Gluons Light Quarks Heavy Quarks (c, b) Photons Neutrinos Electrons Muons Taus Depends what you mean by “out” 1 nuclear diameter away Thickness of a hair away Photon, pion, kaon, nucleon jets Photon, pion, kaon nucleon “heavy quark” jets Photons Electrons Muons Neutrinos 1m Away

13. M. Garcia-Sciveres July 2002 13 What Is Detected? Detect Electrons Muons Photons Jets(will explain) Heavy quark jets Neutrinos or other non-interacting particles How? Electromagnetic calorimetry/tracking Absorber/tracking Electromagnetic calorimetry/tracking Calorimeter/tracking Secondary vertices/tracking Logical inference Detection “Onion”

14. M. Garcia-Sciveres July 2002 14 CDF You’ve seen one Collider detector you’ve seen them all conceptually (but the devil is in the detials- not shown) Installation of CDF Silicon Tracking 2001

15. M. Garcia-Sciveres July 2002 15 CDF Photon Conversions r-  view (data)r vs. z  view (data) Conversion radius (cm) Simulation Data Photon electron positron matter

16. M. Garcia-Sciveres July 2002 16 Heavy Quark Jets Silicon Detectors are used to detect heavy quark jets by reconstructing “DISPLACED VERTICES” Actual Top Quark Decay Recorded by CDF

17. M. Garcia-Sciveres July 2002 17 ATLAS Tracking Detector 7m 85M Pixel channels 6M Si Strip channels 420K straw tube channels All inside a Magnetic field provided by a superconducting solenoid

18. M. Garcia-Sciveres July 2002 18 Elements of the Tracking Detector Higher granularity and resolution near collision point. Granularity sizes are –Silicon pixel detector 50µ x 400µ –Silicon strip detector 80µ x 12cm –Straw tube/wire gas 4mm x 1m Straw tubes Gas-filled tube Wire at HV STRIP Module Pixel Sector With Modules

19. M. Garcia-Sciveres July 2002 19 Charged Particle Tracking TRT Silicon strip detectors Silicon pixel detectors Computer reconstruction Pattern recognition This particular event shows the characteristics of “jets” Jets are created from the quarks and gluons formed in the collisions. The quarks and gluons combine to form hadrons(pions, kaons, protons…) that are detected(if charged) by the tracking detectors or by the calorimetry(charged or neutral).

20. M. Garcia-Sciveres July 2002 20 ATLAS Pixel Detector Disk with Sectors Coolant lines Sector- local support of modules Support frame

21. M. Garcia-Sciveres July 2002 21 Xray of bumps 16 chips with 46,000 bump bonds Bump bonds Sensor ICs Pixel Module Basic Unit repeated 2000 times Sum total of 2000 modules is a 3-dimensional “digital camcorder” with 10 micron resolution 40 million frames per second This will allow ATLAS to detect heavy quark jets

22. M. Garcia-Sciveres July 2002 22 And now the movie