1. Modern Nuclear Physics: Recreating the Creation of the Universe Rene Bellwied Wayne State University (bellwied@physics.wayne.edu) bellwied@physics.wayne.edu The Universe and its beginning The Universe and its beginning Remaining Puzzles in Cosmology Remaining Puzzles in Cosmology How to recreate creation How to recreate creation The latest evidence The latest evidence

2. Newton’s Universe Paradox The universe is not empty. The universe is not empty.  It contains matter with mass.  Attraction of gravity is present. If the universe has existed forever and is static, (i.e. has no net pattern of motion), there must be enough time for gravity to collapse the universe. If the universe has existed forever and is static, (i.e. has no net pattern of motion), there must be enough time for gravity to collapse the universe. Why did it not happen ? Why did it not happen ?

3. Why has it not Collapsed? Newton knew of 3 ways to resolve this paradox. Newton knew of 3 ways to resolve this paradox.  Universe is infinite in volume and mass  Universe is expanding fast enough to overcome the gravitational attraction.  Universe has a beginning and/or an end.

4. Newton’s Choice… Last two ways violate the assumptions of an eternal and static universe, of course. Last two ways violate the assumptions of an eternal and static universe, of course. Newton chose the infinite universe option. Newton chose the infinite universe option. Notice that you are able to arrive at the conclusion of an infinite universe from just one observation: the universe is not empty. No telescopes are needed, just the ability to follow a train of logical thought to its conclusion. Notice that you are able to arrive at the conclusion of an infinite universe from just one observation: the universe is not empty. No telescopes are needed, just the ability to follow a train of logical thought to its conclusion.

5. Olbers' Paradox and the Dark Night Sky Another simple observation is that the visible night sky is dark. Another simple observation is that the visible night sky is dark. IF the universe is infinite, eternal, and static, then the sky should be as bright as the surface of the Sun all of the time! IF the universe is infinite, eternal, and static, then the sky should be as bright as the surface of the Sun all of the time!  Heinrich Olbers (lived 1758--1840) popularized this paradox in 1826 This problem is called Olbers' Paradox (1826). This problem is called Olbers' Paradox (1826).

6. Statement of the Paradox If the universe is uniformly filled with stars, then no matter which direction you look, your line of sight will eventually intersect a star (or other bright thing). If the universe is uniformly filled with stars, then no matter which direction you look, your line of sight will eventually intersect a star (or other bright thing). Known that stars are grouped into galaxies, but the paradox remains: your line of sight will eventually intersect a galaxy. Known that stars are grouped into galaxies, but the paradox remains: your line of sight will eventually intersect a galaxy.

7. How it works…. The brightnesses of stars does decrease with greater distance The brightnesses of stars does decrease with greater distance  remember the inverse square law BUT there are more stars further out. BUT there are more stars further out.  number of stars within a spherical shell around us increases by the same amount as their brightness decreases. Therefore, each shell of stars should have the same overall luminosity and because there are a lot of ever bigger shells in an infinite universe, there should be a lot of light! Therefore, each shell of stars should have the same overall luminosity and because there are a lot of ever bigger shells in an infinite universe, there should be a lot of light!

8. An Expanding Universe Edwin Hubble and Milton Humason discovered (1920) that the universe is not static it is expanding. Edwin Hubble and Milton Humason discovered (1920) that the universe is not static it is expanding. This is enough to resolve the paradox. This is enough to resolve the paradox.  As the universe expands, the light waves are stretched out and the energy is reduced.  Also, the time to receive the light is also lengthened over the time it took to emit the photon.

9. Let there be light The Hertzsprung- Russell Diagram The Hertzsprung- Russell Diagram Relation between mass and temperature, light output, lifetime. Relation between mass and temperature, light output, lifetime. Stars shine because of nuclear fusion reactions in their core. The more luminous they are, the more reactions are taking place in their cores.

10. Wien’s Law Temperature Cool stars will have the peak of their continuous spectrum at long (red) wavelengths. Cool stars will have the peak of their continuous spectrum at long (red) wavelengths. As the temperature of a star increases, the peak of its continuous spectrum shifts to shorter (blue) wavelengths. As the temperature of a star increases, the peak of its continuous spectrum shifts to shorter (blue) wavelengths.

11. Doppler Effect Case (a) Case (a)  Object (source) moving towards observer A at velocity “v”  Observer “A” sees compressed wave, I.e. shorter wavelength, higher frequency.  Observer “B” see stretched wave, I.e. longer wavelength, lower frequency. Case (b) Case (b)  Stationary source  Observer “A” and “B” see same wavelength. Source Observer A Observer B v (a) Source Observer A Observer B (b)

12. Doppler Effect with Stars A star's motion causes a wavelength shift in its light emission spectrum, which depends on speed and direction of motion. A star's motion causes a wavelength shift in its light emission spectrum, which depends on speed and direction of motion. If star is moving toward you, the waves are compressed, so their wavelength is shorter = blueshift. If star is moving toward you, the waves are compressed, so their wavelength is shorter = blueshift. If the object is moving away from you, the waves are stretched out, so their wavelength is longer = redshift. If the object is moving away from you, the waves are stretched out, so their wavelength is longer = redshift.

13. Relativity and Universe Expansion This explanation also works if you are moving and the object is stationary or if both you and the object are moving. This explanation also works if you are moving and the object is stationary or if both you and the object are moving. The doppler effect tells you about the relative motion of the object with respect to you. The doppler effect tells you about the relative motion of the object with respect to you. Important fact: Important fact:  The spectral lines of nearly all of the galaxies in the universe are shifted to the red end of the spectrum.  This means that the galaxies are moving away from the Milky Way galaxy.  This is evidence for the expansion of the universe.

14. Uniform Expansion The Hubble law, speed = H o × distance, says the expansion is uniform. The Hubble law, speed = H o × distance, says the expansion is uniform. The Hubble constant, H o, is the slope of the line relating the speed of the galaxies away from each other and their distance apart from each other. The Hubble constant, H o, is the slope of the line relating the speed of the galaxies away from each other and their distance apart from each other.  It indicates the rate of the expansion.  If the slope is steep (large H o ), then the expansion rate is large and the galaxies did not need much time to get to where they are now.

15. Hubble Law Hubble and Humason (1931): Hubble and Humason (1931):  the Galactic recession speed = H × distance, where H is a number now called the Hubble constant. This relation is called the Hubble Law and the Hubble constant is the slope of the line. This relation is called the Hubble Law and the Hubble constant is the slope of the line.

16. Age of the Universe Age of the universe can be estimated from the simple relation of time = distance/speed. Age of the universe can be estimated from the simple relation of time = distance/speed. The Hubble Law can be rewritten The Hubble Law can be rewritten  1/H o = distance/speed. The Hubble constant tells you the age of the universe, i.e., how long the galaxies have been expanding away from each other: The Hubble constant tells you the age of the universe, i.e., how long the galaxies have been expanding away from each other:  Age = 1/H o. Age upper limit since the expansion has been slowing down due to gravity. Age upper limit since the expansion has been slowing down due to gravity.

17. Some preliminary Conclusions Expansion of the universe means that galaxies were much closer together long ago. Expansion of the universe means that galaxies were much closer together long ago. This implies that there is a finite age to the universe, it is not eternal. This implies that there is a finite age to the universe, it is not eternal. Even if the universe is infinite, the light from places very far away will not have had enough time to reach us. This will make the sky dark. Even if the universe is infinite, the light from places very far away will not have had enough time to reach us. This will make the sky dark.

18. Star Count in the Galaxy Rough guess of the number of stars in our galaxy obtained by dividing the Galaxy's total mass by the mass of a typical star (e.g., 1 solar mass). Rough guess of the number of stars in our galaxy obtained by dividing the Galaxy's total mass by the mass of a typical star (e.g., 1 solar mass).  The result is about 200 billion stars! The actual number of stars could be several tens of billions less or more than this approximate value. The actual number of stars could be several tens of billions less or more than this approximate value.

19. How stars like the sun evolve

20. How heavy stars evolve

21. Black Hole Formation After a supernovae explosion, if the core remnant has a mass greater than 3 solar masses, then not even the super-compressed degenerate neutrons can hold the core up against its own gravity. After a supernovae explosion, if the core remnant has a mass greater than 3 solar masses, then not even the super-compressed degenerate neutrons can hold the core up against its own gravity. As the core implodes it briefly makes a neutron star for just long enough to produce the supernova explosion. Supernovae are rare (one every 25 years in our galaxy of 200 billion stars!) As the core implodes it briefly makes a neutron star for just long enough to produce the supernova explosion. Supernovae are rare (one every 25 years in our galaxy of 200 billion stars!) Gravity finally wins and compresses everything to a mathematical point at the center. The point object is a black hole. Gravity finally wins and compresses everything to a mathematical point at the center. The point object is a black hole.

23. Ultra-strong gravity The gravity of the point mass is strong enough close to the center that nothing can escape, not even light! Within a certain distance of the point mass, the escape velocity is greater than the speed of light. The gravity of the point mass is strong enough close to the center that nothing can escape, not even light! Within a certain distance of the point mass, the escape velocity is greater than the speed of light. The distance at which the escape velocity equals the speed of light is called the event horizon (or Schwarzschild radius) because no information from within that distance of the point mass will be able to make it to the outside. The distance at which the escape velocity equals the speed of light is called the event horizon (or Schwarzschild radius) because no information from within that distance of the point mass will be able to make it to the outside.

24. Spiral Galaxies Andromeda Galaxy M31 near the Milky Way. Andromeda Galaxy M31 near the Milky Way. NGC 2997 large face-on spiral galaxy (Sc). NGC 2997 large face-on spiral galaxy (Sc).

25. Masses of Galaxies Masses of galaxies are found from the orbital motion of their stars. Stars in a more massive galaxy orbit faster than those in a lower mass galaxy because the greater gravity force of the massive galaxy causes larger accelerations of its stars. Masses of galaxies are found from the orbital motion of their stars. Stars in a more massive galaxy orbit faster than those in a lower mass galaxy because the greater gravity force of the massive galaxy causes larger accelerations of its stars. By measuring the star speeds, one finds out how much gravity there is in the galaxy. The rotation curve shows how orbital speeds in a galaxy depend on their distance from the galaxy's center. Orbital speed is found from the doppler shifts of the 21-cm line radiation from the atomic hydrogen gas. By measuring the star speeds, one finds out how much gravity there is in the galaxy. The rotation curve shows how orbital speeds in a galaxy depend on their distance from the galaxy's center. Orbital speed is found from the doppler shifts of the 21-cm line radiation from the atomic hydrogen gas. Since gravity depends on mass and distance, knowing the size of the star orbits enables you to derive the galaxy's mass. Since gravity depends on mass and distance, knowing the size of the star orbits enables you to derive the galaxy's mass.

26. A Mass Problem The stars and gas in most galaxies move much quicker than expected from the luminosity of the galaxies. The stars and gas in most galaxies move much quicker than expected from the luminosity of the galaxies. In spiral galaxies, the rotation curve remains at about the same value at great distances from the center (it is said to be ``flat''). In spiral galaxies, the rotation curve remains at about the same value at great distances from the center (it is said to be ``flat''). This means that the enclosed mass continues to increase even though the amount of visible, luminous matter falls off at large distances from the center. This means that the enclosed mass continues to increase even though the amount of visible, luminous matter falls off at large distances from the center. Something else must be adding to the gravity of the galaxies without shining. We call it Dark Matter ! According to measurements it accounts for 90% of the mass in the universe. Something else must be adding to the gravity of the galaxies without shining. We call it Dark Matter ! According to measurements it accounts for 90% of the mass in the universe.

27. What is Dark Matter ? We don’t know (yet) White dwarfs, brown dwarfs, black holes, massive neutrinos, although intriguing are very unlikely to account for most of the dark matter. The dwarfs are generally called Massive compact halo objects (MACHOS) White dwarfs, brown dwarfs, black holes, massive neutrinos, although intriguing are very unlikely to account for most of the dark matter. The dwarfs are generally called Massive compact halo objects (MACHOS) New exotic particles or formations are more likely: New exotic particles or formations are more likely:  Weakly interacting massive particles (WIMPS)  Matter based on exotic quark configurations (e.g. strange Quark matter) If these states exist somewhere in the universe wouldn’t they have been produced in the early universe ? If these states exist somewhere in the universe wouldn’t they have been produced in the early universe ?

28. Evidence for the Big Bang Galaxies are distributed fairly uniformily across the sky between a lot of void (Obler’s paradox) Galaxies are distributed fairly uniformily across the sky between a lot of void (Obler’s paradox) Background radiation was predicted, and has been found, to be exactly 2.73 K everywhere in the universe. Variations as measured by a NASA satellite named COBE (Cosmic Background Explorer) are less than 0.0001 K. Background radiation was predicted, and has been found, to be exactly 2.73 K everywhere in the universe. Variations as measured by a NASA satellite named COBE (Cosmic Background Explorer) are less than 0.0001 K.

30. What happened at the beginning ?

31. A Cosmic Timeline Age Energy Matter in universe Age Energy Matter in universe 010 19 GeV grand unified theory of all forces 010 19 GeV grand unified theory of all forces 10 -35 s10 14 GeV1 st phase transition (strong: q,g + electroweak: g, l,n) 10 -10 s10 2 GeV2 nd phase transition (strong: q,g + electro: g + weak: l,n) 10 -5 s0.2 GeV3 rd phase transition (strong:hadrons + electro:g + weak: l,n) 3 min.0.1 MeVnuclei 6*10 5 years0.3 eVatoms Now 3*10 -4 eV = 3 K (15 billion years)

32. The Grand Unification Theory (GUT)

33. An Inflationary Universe The universe expanded to a point where the unified forces of nature started to decouple. When the strong force decoupled a major amount of energy was released and the universe expanded by a facto 10 30 in less than 10 -36 seconds. This rapid expansion is called inflation The universe expanded to a point where the unified forces of nature started to decouple. When the strong force decoupled a major amount of energy was released and the universe expanded by a facto 10 30 in less than 10 -36 seconds. This rapid expansion is called inflation

35. Going back in time

36. time temperature ~ 100 s after Big Bang Nucleosynthesis begins In the beginning quark – gluon plasma ~ 10  s after Big Bang Hadron Synthesis strong force binds quarks and gluons in massive objects: protons, neutrons mass ~ 1 GeV STAR

37. The RHIC Complex 1. Tandem Van de Graaff 2. Heavy Ion Transfer Line 3. Booster 4. Alternating Gradient Synchrotron (AGS) 5. AGS-to-RHIC Transfer Line 6. RHIC ring 1. Tandem Van de Graaff 2. Heavy Ion Transfer Line 3. Booster 4. Alternating Gradient Synchrotron (AGS) 5. AGS-to-RHIC Transfer Line 6. RHIC ring 1 3 4 6 2 5

38. Let’s go for the ‘Mini-Bang’ We need a system that is small so that we can accelerate it to very high speeds. (99.9% of the speed of light) We need a system that is small so that we can accelerate it to very high speeds. (99.9% of the speed of light) But we need a system (i.e. a chunk of matter and not just a single particle) so that the system can follow simple rules of thermodynamics and form a new state of matter in a particular phase. But we need a system (i.e. a chunk of matter and not just a single particle) so that the system can follow simple rules of thermodynamics and form a new state of matter in a particular phase. We use heavy ions (e.g. a Gold ion which is made of 197 protons and neutrons). It is tiny (about a 10- 14 m diameter) but it is a finite volume that can be exposed to pressure and temperature We use heavy ions (e.g. a Gold ion which is made of 197 protons and neutrons). It is tiny (about a 10- 14 m diameter) but it is a finite volume that can be exposed to pressure and temperature

39. What are we trying to do ? We try to force a phase transition of the matter we know (e.g. our Gold nucleus) to a new state of matter predicted by the Big-Bang, called a Quark- Gluon Plasma (QGP) We try to force a phase transition of the matter we know (e.g. our Gold nucleus) to a new state of matter predicted by the Big-Bang, called a Quark- Gluon Plasma (QGP) We try to do that by following thermodynamics: We try to do that by following thermodynamics: PV = nRT PV = nRT A system of volume V can change if exposed to pressure P or temperature T.

40. An example: water, ice, and steam pressure This is a simple phase diagram

41. The temperature inside The temperature inside a heavy ion collision at RHIC can exceed 1000 billion degrees !! The temperature inside a heavy ion collision at RHIC can exceed 1000 billion degrees !! That’s about 10,000 times the temperature of the sun That’s about 10,000 times the temperature of the sun

42. How to create a QGP ? energy = temperature & density = pressure

43. Let’s collide two heavy nuclei (1)

44. Let’s collide two heavy nuclei (2)

45. What is a Quark-Gluon Plasma? An atom contains a nucleus... …which contains protons and neutrons... …which contain up and down quarks.

46. Let’s study all phases of the process Freeze-out Hadron Gas Phase Transition Plasma-phase Pre-Equilibrium Hard scattering If the QGP was formed, it will only live for 10 -21 s !!!! BUT does matter come out of this phase the same way it went in ???

47. The STAR Experiment 450 scientists from 50 international institutions Conceptual Overview

48. The STAR Experiment construction from 1992-2000 data taking from 2000-2010 (?) Overview while under construction

49. The STAR Experiment (TPC) Construction in progress

50. The STAR Experiment (SVT) Construction in progress

51. The STAR Experiment (SVT) The happy crew after 8 long years

52. Actual Collision in STAR (1) Actual STAR data for a peripheral collision Actual STAR data for a peripheral collision

53. Actual Collision in STAR (2) Actual STAR data for a central collision

54. What is going on ? A Au nucleus consists of 79 protons and 118 neutrons = 197 particles -> 394 particles total A Au nucleus consists of 79 protons and 118 neutrons = 197 particles -> 394 particles total p and n consist of u- and d-quarks p and n consist of u- and d-quarks After the collision we measure about 10,000 particles in the debris! After the collision we measure about 10,000 particles in the debris! measured particles: p, , K, , d, J/  Y measured particles: p, , K, , d, J/  Y many particles contain s-quarks, some even c-quarks many particles contain s-quarks, some even c-quarks Energy converts to matter, but does the matter go through a phase transition ? Energy converts to matter, but does the matter go through a phase transition ?

55. How Do We Measure Things ? particles go from the inside-out particles go from the inside-out they have to traverse certain detectors they have to traverse certain detectors they should stop in the outermost detector they should stop in the outermost detector the particle should not change its properties when traversing the inner detector the particle should not change its properties when traversing the inner detector DETECT but don’t DEFLECT !!! DETECT but don’t DEFLECT !!! inner detectors have to be very thin (low radiation length): easy with gas, challenge with solid state materials (Silicon). inner detectors have to be very thin (low radiation length): easy with gas, challenge with solid state materials (Silicon).

56. What do we have to check ? If there was a transition to a different phase, then this phase could only last very shortly. The only evidence we have to check is the collision debris. If there was a transition to a different phase, then this phase could only last very shortly. The only evidence we have to check is the collision debris. Check the make-up of the debris: Check the make-up of the debris:  which particles have been formed ?  how many of them ?  are they emitted statistically (Boltzmann distribution) ?  what are their kinematics (speed, momentum, angular distributions) ?  are they correlated in coordinate or momentum space ?  do they move collectively ?

57. Signatures of the QGP phase Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. entropy (i.e. # of degrees of freedom. The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the existing form of matter. In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity. At the step some signatures drop and some signatures rise Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. entropy (i.e. # of degrees of freedom. The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the existing form of matter. In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity. At the step some signatures drop and some signatures rise

58. How do we know what happened ? We have to compare to a system that did definitely not go through a phase transition (a reference collision) We have to compare to a system that did definitely not go through a phase transition (a reference collision) Two options: Two options:  A proton-proton collision compared to a Gold- Gold collision does not generate a big enough volume to generate a plasma phase  A peripheral Gold-Gold collision compared to a central one does not generate enough energy and volume to generate a plasma phase

59. Time scales of the collision (simulated) hadronization initial state pre-equilibrium QGP and hydrodynamic expansion hadronic phase and freeze-out 1 fm/c5 fm/c10 fm/c50 fm/ctime dN/dt Chemical freeze out Kinetic freeze out Measurements: HBT Balance function Resonances

60. Time scales according to STAR data dN/dt 1 fm/c 5 fm/c 10 fm/c20 fm/c time Chemical freeze out Kinetic freeze out Balance function (require flow) Resonance survival Rlong (and HBT wrt reaction plane) Rout, Rside

61. Evidence: Some particles are suppressed If the phase is very dense (QGP) than certain particles get absorbed If the phase is very dense (QGP) than certain particles get absorbed ? If things are produced in pairs then one might make it out and the other one not. Central Au + Au Peripheral Au + Au STAR Preliminary If things require the fusion of very heavy rare quarks they might be suppressed in a dense medium

62. Evidence: Some particles are enhanced Remember dark matter ? Well, we didn’t find clumps of it yet, but we found increased production of strange quark particles Remember dark matter ? Well, we didn’t find clumps of it yet, but we found increased production of strange quark particles

63. What is our present conclusion ? The interpretation of bulk properties in heavy ion systems is complex. We have indications of unusual behavior in rare, fast decoupling, and high momentum probes. Our system behaves like matter, not a collection of elementary particles, and we have the tools to study it. We could declare discovery of the QGP but we have more things to study and we don’t have the ‘smoking gun’ yet. Further exploration will take a few years, but the first steps were very exciting and very successful.