From Big Bang to TODAY a human odyssey

1. From Big Bang to TODAYa human odyssey by UshaMallik Professor, Department of Physics and Astronomy, The University of Iowa, Iowa City, U.S.A. December 28, 2010 Hyderabad University, Hyderabad, India

2. Study of the Big and the Small • Astrophysics and Cosmology: the largest (macro) • The Big Bang (today’s established paradigm) • Particle Physics : the smallest (micro) • Standard Model (today’s established paradigm) Physics at the largest scale is related to that at the smallest by about 60 orders of magnitude

3. Fundamental forces/interactions • Strong (holds nuclei together) • Electromagnetic (Chemistry, Biology, everyday phenomena) • Weak (radioactive decays) • Gravitational (our solar system, most of the heaven)

4. The twentieth century • Quantum mechanics (physics of very small) • Relativity • General relativity (1917) (physics of very large) • Expanding universe Expansion of universe observed (measured) by Edwin Hubble (1929) Big Bang: An extremely powerful momentary explosive burst of radiation of very high energy in which the seed of the universe was created some 13.7 billion years ago

5. Like the raisins in the bread being baked, the further away the galaxies, the faster they are receding, 70 km/s per Mpc, Hubble constant, H0 1 Mpc 3.3 Million light years Edwin Hubble/1929

6. The Big Bang • Alpher, Bethe, Gamow theory (H, He, heavy elements creation) • Later vindicated: Cosmic Microwave Background, Big Bang Nucleosynthesis) • Cosmic Microwave Background Radiation (2.73 K) • Black body radiation from a universe in thermal equilibrium • Discovery by Penzias and Wilson in 1964/5 (3 K, Nobel 1978) • Estimates by Gamow, Dicke etc (as low as 6 K) • Accurate measurements by COBE , WMAP, PLANCK • Isotropy, anisotropy • The Horizon problem • Homogeneity and Flatness problem • Relic problem

7. Understanding of this part came later In the very young and very hot universe filled with plasma, the “glow” or the black body radiation could not escape because of continuous split-up and re-combinations and Thompson scattering until the universe cooled sufficiently to form atoms. Until then the universe was opaque to the EM radiation. Later when the atoms formed, they could not absorb the radiation, and the universe became transparent to this relic radiation

8. The Big Bang • Alpher, Bethe, Gamow theory (H, He, heavy elements creation) • Later updated and verified as Big Bang Nucleosynthesis) • Cosmic Microwave Background (CMB) Radiation (2.73 K) • Black body radiation from a universe in thermal equilibrium • Discovery by Penzias and Wilson in 1964/5 (Nobel 1978) • Estimates by Gamow, Dicke etc (as low as 6K) • Accurate measurements by COBE, WMAP, PLANCK • Isotropy, anisotropy • The Horizon problem • Homogeneity and Flatness problem • Relic problem

9. From CMB Remarkably isotropic as expected for the Big Bang birth of our universe, but….

10. Seeds of galaxy formation from the early anisotropy; temp difference of one hundred thousandth of a degree is enough for structure formation

11. Big Bang Nucleosynthesis The relative abundance of the primordial elements in the universe according to matter density observed agrees well with Big Bang theory calculations

12. The Big Bang • Alpher, Bethe, Gamow theory (H, He, heavy elements creation) • Later updated and verified as Big Bang Nucleosynthesis) • Cosmic Microwave Background Radiation (2.73 K) • Black body radiation from a universe in thermal equilibrium • Discovery by Penzias and Wilson in 1964/5 (Nobel) • Estimates by Gamow, Dicke etc (as low as 6 K) • Accurate measurements by COBE , WMAP, PLANCK • Isotropy, anisotropy • The Horizon problem (causal connection) • Homogeneity and Flatness problem • Relic problem (topological defects)

13. Horizon/homogeneity problem When we look at the CMB it comes from many billions co-moving light years away. However the universe was only 390,000 years old when the light was emitted. In that time light would have reached as far as the smaller circles; the two points indicated on the diagram would not have been able to be causally connected, only about an angle of 2 in the sky in the CMB radiation would show uniformity. However, a remarkable uniformity is observed in the CMB radiation.

14. Flatness problem Regarding the space-time geometry of the universe The density parameter 0 = /c , with  the mass density and c the critical density 1 in 1014 Initial density had to be tuned to 1 in 1059

15. Relic problem (topological defects) Solution: Inflation A number of exotic objects, like monopoles, should have been produced in the very early very dense universe at Planck time; some of them should be visible even today, although not be produced in the current universe too cold to produce such objects Trying to solve the Monopole problem, Alan Guth came up with the concept of inflation as the solution in 1980 For ~10-35 sec the universe went through an exponential growth when it grew from approximately a dimension of ~10-28 cm to about 1 cm, a growth of  1028/more fold, doubling every 10-37 sec

16. Results from WMAP WMAP : Wilkinson Microwave Anisotropy Probe

18. Results from WMAP

19. In 1998: The expansion of the universe is accelerating, simultaneous results from Supernovae type 1A measurements in the U.S. and in Europe

20. Two groups, one in the U.S. and one in Europe published independent observations of signals from high-z (high red-shifted) supernovae in 1998, showing that the expansion of our universe is accelerating.

21. Symmetries: the unification theme

22. A touch of recent history • Neutral current discovery 1972 (CERN) • V-A weak current (1950’s), • gauge theory of weak interactions (after QED) • W/Z postulate, Higgs phenomena (symmetry breaking) • Charm discovery 1974 (SLAC/BNL, Nobel Prize) • GWS Electroweak model vindicated (Nobel Prize) • Tau (1975 SLAC) and b-quark discovery (1977 FNAL) • Discovery of W Z0 (1983 CERN, Nobel Prize) • Discovery of the top quark (1995 FNAL)

23. A la Standard Model

25. Electron (ep) proton scattering, HERA e + p  + x’ A proton is a very complex object teeming with partons (not just two u and one d quarks) e + p e + x Neutral Current : Charged Current :

26. Electroweak Unification Strength of NC and CC are similar at Q2 MZ2  MW2

29. The Outstanding Questions What led to the Physics laws of today So: Create and study lots of `Mini Big Bangs’

31. The Large Hadron Collider At CERN, stradling the French-Swiss border, 27 km in circumference airport http://www.uiowa.edu/~cdoavp

32. The Nominal LHC

33. Theoretical physicists tend to use units of length, energy, and temperature interchangeably. Energy is related to temperature through the expression E = kT, where k is Boltzmann's constant, so high energies correspond to high temperatures. Energy is proportional to 1/length. So, high energies and temperatures correspond to short distances. The scale in the diagram above is logarithmic, so each tick mark is separated by a factor of 100,000. Physics at the Planck scale is closely related to physics on cosmological scales nearly 60 orders of magnitude larger.

34. Current Status and Plan • Collected p-p data at 7 TeV (in addition to 0.9 and 2.36 TeV) at 1032 cm-2 s-1 • The ATLAS experiment collected a luminosity of 45 pb-1 at 7 TeV • And Heavy ion collision (Pb-Pb) data at 7 TeV (7 TeV per particle means 574 TeV per Pb nucleus : plasma) • Now winter break for 10 weeks • Meeting at Chamonix to decide whether to continue through 2012

35. P-(anti) P cross-sections Production cross-sections and dynamics are controlled by QCD pdf’s

36. Detectors are typically cylindrical at a collider Building an appropriate detector determined by the physics requirements and the energy Identifying the interactions we are interested in (by their decay products) We only observe the decays products-- the longer lived particles Measure the tracks left by the charged particles as accurately as possible and starting as close to the interaction point (IP) as possible, so we can identify the secondary decay vertices like B-mesons, K0’s…..(the weak decays) Reconstruct the tracks, measure individual momentum from the curvature in a B-field Measure the total energy of the track in a calorimeter: EM calorimeter for EM decays, an atomic phenomenon, Hadron calorimeter for hadronic particles, a nuclear phenomenon (can have EM mixed) The last part is left for relatively high energy muons which mainly loses energy by ionization

37. A Modern Colliding-beam Detector The smaller the scale to probe, the higher the energy, and the bigger the detector

39. Trigger and Data Acquisition (DAQ) • Each sub-detector sends data/hits at high rate • Calibration applied to the hits  position and energy deposit • Fast pattern recognition • Looking for a needle in a haystack (trigger): Most collisions are not what we want • Several levels of electronic/software filters (Level 1, Level 2, Event filter in ATLAS) • Apply buffered pipelines • ATLAS Level 1 (40 MHz  75 kHz) • ATLAS Level 2 (75 kHz  2 kHz) • ATLAS Event filter (2 kHz  200 Hz) • The remaining events passing all filters are recorded and analyzed

40. The ATLAS Collaboration

41. The ATLAS Experiment • Excellent tracking and vertexing • Secondary vertex reconstruction • Very good coverage, nearly hermetic • Excellent calorimetry • Electromagnetic shower reconstruction & 0 • Good jet resolution and jet-jet mass resolution

42. The ATLAS Detector Very large general purpose magnetic detector (only 7,000 T) Overall dimensions are 45 m long and 25 m in diameter

43. The Inner Tracking Detector Excellent pattern recognition

44. Pseudorapidity ( = tan-1 /2) coverage of the Inner Detector

45. A Quick Overview of Pixels 430 mm •  coverage of 2.5 • 80 million channels in total distributed • 1744 modules each (46, 080 pixels) • Each module read out by 16 Front-end elements (2880 pixels)

46. A Pixel Module • Sensors bump-bonded to the FEs • Each Module controlled by a Module Controller Chip (MCC) • MCC situated on a flexible printed circuit (flex-hybrid) • FEs connected to flex-hybrid by Al-wire bonding. Cu traces route signals to • MCC • LVDS by means of Type-0 connector/ • micro-cable to PP0 (Opto-board)

47. The DAQ • The Calibration process stresses the DAQ system • Data taking is much less demanding • The DSP plays a critical role in the calibration

48. Pixel FE Readout Chip • Uses CMOS technology. Pixel size 50µm x 400µm. • Connected to sensor via 50µm pitch bump bond. • 2880 pixel cells in 18 x 160 matrix, column pair R/O. • Charge-sensitive amplifier • Programmable threshold comparator • Time-over-threshold (TOT) measured by registering leading edge (LE) and trailing edge (TE) timestamp for pulse height above the threshold. • Local buffering for 3.2 µs • Charge injection circuitry for calibration by 10-bit DAC • Coarse global threshold adjustment 3-bit (GDAC) • For each pixel cell: • Adjustable 7-bit discriminator threshold (TDAC) • Adjustable 3-bit charge-to-TOT response (FDAC) • Measurement capability of leakage current

49. Heart of Pixel Calibration

50. The Readout Opto-board VCSEL : Vertical Cavity Surface Emission Laser VDC : VCSEL Driver Circuit DORIC : Digital Optical Receiver Circuit PIN : Positive Intrinsic Negative (diode) DRX (ASIC) converts from PIN into LVDS BPM (ASIC) Bi-phase marker encodes clock & data for fiber optic transmission PP : Patch Panel BOC scan : Rx Threshold, Rx Delay, VCSEL voltage In the Opto-board : • The electrical signals (LVDS) get converted to optical signal by VDC/VCSEL DataLink • Optical (Command) signals gets converted into electrical signals by PiN/DORIC TTC Link