frank l. h. wolfs / university of rochester, slide 1 evolution of the universe frank l. h. wolfs...
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Frank L. H. Wolfs / University of Rochester, Slide 1
Evolution of the Universe
Frank L. H. WolfsDepartment of Physics and Astronomy
University of Rochester
Frank L. H. Wolfs / University of Rochester, Slide 2
Outline
Why do I talk about this topic?
Tools used to probe the evolution of the Universe:Astronomy
Nuclear PhysicsHigh-Energy Physics
Going back in time in New York State:The Relativistic Heavy-Ion Collider (RHIC)
Conclusions
Frank L. H. Wolfs / University of Rochester, Slide 3
Why do I talk about this topic?I am just a nuclear physicist!
Because I was asked to give a talk about PHOBOS.
Because my primary interest in relativistic heavy-ion physics is motivated by the astrophysical implications of our studies of properties of nuclear matter under extreme conditions.
Because our study of the evolution of the universe is a great example of how distinct areas of basic science can contribute different components / solutions to the same puzzle.
Frank L. H. Wolfs / University of Rochester, Slide 4
What happened during the last 15 x 109 years?
Frank L. H. Wolfs / University of Rochester, Slide 5
Going back in time: Astronomy
Frank L. H. Wolfs / University of Rochester, Slide 6
Nuclear physics allows us to describe stellar nucleosynthesis
Frank L. H. Wolfs / University of Rochester, Slide 7
The binding energy per nucleonSource of nuclear energy
Frank L. H. Wolfs / University of Rochester, Slide 8
Nucleosynthesis in stars forms all elements heavier than Lithium
Death of an “Ordinary” Star Death of a Massive Star
Frank L. H. Wolfs / University of Rochester, Slide 9
Nucleosynthesis
Hydrogen burning (He production)
Helium burning (C and O production)
Carbon, Oxygen, and Neon burning (16 ≤ A ≤ 28 production)
Silicon burning (28 ≤ A ≤ 60 production)
The s-, r-, and p-processes (A ≥ 60 production)
The l-process (D, Li, Be, and B production)
Frank L. H. Wolfs / University of Rochester, Slide 10
Experimental nuclear physics:Measuring stellar reaction rates
Converting protons to helium
Frank L. H. Wolfs / University of Rochester, Slide 11
The evolution of stars
Frank L. H. Wolfs / University of Rochester, Slide 12
Formation of heavy elements(beyond Iron)
Elements beyond iron are not formed in “lighter-element burning” reactions (abundances are too large).
The neutron-rich nuclei in this region are formed via the s-process (n capture) and r-process ( decay).
The proton-rich nuclei in this region are formed via the p-process (p capture).
Need nuclear data far from stability.
Frank L. H. Wolfs / University of Rochester, Slide 13
Better techniques/facilities =>Better info far from stability
Frank L. H. Wolfs / University of Rochester, Slide 14
Nucleosynthesis is an ongoing process.
Nuclei are still being synthesized in the Universe.
By measuring life times of unstable nuclei, areas of active nucleosynthesis can be be identified.
For example: 26Al has a lifetime of 730,000
years. 26Al decays by emitting rays. The origin of 26AL rays
reveals the locations of active nucleosynthesis. Data from the GRO satellite
Frank L. H. Wolfs / University of Rochester, Slide 15
Star Formation:1 x 109 yr after the Big Bang
Molecular clouds of mainly hydrogen molecules are the birthplace of stars:
Dense regions collapse and form “protostars”.
Initially the gravitational energy of the collapsing star is the source of its energy.
Once the density of its central core is large enough, the hydrogen burning process can start, and the star becomes a “main sequence” star.
Frank L. H. Wolfs / University of Rochester, Slide 16
Big-Bang Problem:Large Scale Structures
The Big-Bang theory predicts that matter is uniformly distributed throughout the universe.
The formation of large-scale structures requires the formation of small fluctuations in density (around 0.5%).
The tiny fluctuations in density can not be produced by gravity.
Frank L. H. Wolfs / University of Rochester, Slide 17
Cosmic Microwave Background:Fluctuations in early universe
Microwave background is createdwhen hydrogen atoms form (about400,000 years after the Big bang.
Frank L. H. Wolfs / University of Rochester, Slide 18
Cosmic Microwave Background:Fluctuations in early universe
Observations by COBE have been confirmed by BOOMERANGwith an improved angular resolution (factor of 35).
Frank L. H. Wolfs / University of Rochester, Slide 19
Formation of light nuclei:Three minutes after the Big Bang
Frank L. H. Wolfs / University of Rochester, Slide 20
Formation of light nuclei:Three minutes after the Big Bang
Neutrons and protons interact and form deuterium.
Tritium and Helium are subsequently created by neutron and proton capture.
The reaction rates are high enough to ensure that most neutrons will interact before they decay (neutron life time is 10 minutes).
Using measured reaction rates, we can calculate the relative abundance.
Frank L. H. Wolfs / University of Rochester, Slide 21
Formation of light nuclei:Three minutes after the Big Bang
All deuterium is created during this phase.
The calculated abundances depend critically on the density of baryons (protons and neutrons).
A baryon density of a few percent is required to account for the measured abundances. Data limit the number of light neutrino generations.
Not all dark matter can be baryonic.
Critical density
Frank L. H. Wolfs / University of Rochester, Slide 22
Formation of Nucleons100 µs after the Big Bang
During the first few seconds after the Big Bang the universe was composed of: Nucleons (protons and neutrons). Any nuclei formed at this
point would not have survived long in this high-temperature environment.
Leptons (electrons, neutrinos, and photons) During this phase baryons, anti-baryons, and photons were in
equilibrium and their abundances were nearly equal. The ratio NB / N observed today is 10-9. This ratio represents the fractional discrepancy between
matter and antimatter during this phase: For every one billion anti-baryons there were one billion
and one baryons.
Frank L. H. Wolfs / University of Rochester, Slide 23
Unanswered Questions about the Evolution of the Early Universe
Origin of the density fluctuations: Quark-to-Hadron transitions
Matter / anti-matter asymmetry Symmetry breaking
Missing mass: WIMPS Axions Neutrinos
Recreation of the “early universe” mightallow us to address these questions.
Frank L. H. Wolfs / University of Rochester, Slide 24
Recreating the early universe:relativistic heavy-ion collisions
Frank L. H. Wolfs / University of Rochester, Slide 25
Production of the QGPRelativistic Heavy-Ion Collisions
Two nuclei approach each other. The nuclei are contracted to thin pancakes
Hard collisions dominate first instants of collision
Produced particles reinteract at hard and soft scales
Final state particles freeze-out and stream towards the detectors…
Frank L. H. Wolfs / University of Rochester, Slide 26
Phases of Nuclear Matter
Nuclear matter can exist in several phases: At low excitations energies,
nuclear matter may evaporate protons and neutrons.
At high temperatures or densities, a “gas” of nucleons may form.
At extreme conditions, individual nucleons may lose their identities, and the constituents quarks and gluons may form a quark-gluon plasma.
Frank L. H. Wolfs / University of Rochester, Slide 27
Formation of the Quark-Gluon Plasma (QGP)
Frank L. H. Wolfs / University of Rochester, Slide 28
Relativistic Heavy-Ion Collider:Scientific Objectives
To create extraordinary states of nuclear matter in density and temperature (similar to matter a few µs after the Big Bang).
To deconfine the quarks and gluons and form a Quark-Gluon Plasma.
Experimental goals @ RHIC
Verify the existence of the Quark-Gluon Plasma.
Explore the properties of this new phase of matter.
Study the transitions from quarks to nucleons (which will provide insight into the physics of the early universe).
Frank L. H. Wolfs / University of Rochester, Slide 29
From BBC NewsRHIC is not the end of the world!
Frank L. H. Wolfs / University of Rochester, Slide 30
From ABC NewsThe Doomsday Machine!
Frank L. H. Wolfs / University of Rochester, Slide 31
Will the world survive the first collisions at RHIC?
Suppose a black hole was formed in a head-on collision between two 100-GeV/A Au ions.
Properties of this black hole (Astronomy 142): The Schwarzschild radius is 2.1 x 10-47 m The black hole evaporates via Hawking radiation in about
2.3 x 10-82 s Before the black hole evaporates, it moves 7 x 10-74 m The black hole can not acquire additional material before it
evaporates.
Yes !!!!!!!!!!!!!!!!!!!!!!!!!!!!! There will be life after RHIC.
Frank L. H. Wolfs / University of Rochester, Slide 32
Going back in time by travelling across New York State.
Frank L. H. Wolfs / University of Rochester, Slide 33
Going back in time by travelling across New York State.
Frank L. H. Wolfs / University of Rochester, Slide 34
The Relativistic Heavy-Ion ColliderBrookhaven National Laboratory
Two 3.8 km-long concentric rings
with 6 interaction regions. Capable of accelerating ions up to Au
(A+A, p+p, and p+A). Maximum beam energy:
Au + Au: 100 GeV/u p + p: 250 GeV
Design luminosity: Au + Au: 2 x 1026 cm-2 s-1
p + p: 1 x 1031 cm-2 s-1
First running period concluded on
9/19/2000 with a luminosity close to
10% of the design luminosity.
Frank L. H. Wolfs / University of Rochester, Slide 35
Preparing Au ions for injection in RHIC.
1 MeV/u
78 MeV/u
10.8 GeV/u
Frank L. H. Wolfs / University of Rochester, Slide 36
Conclusions
Very different areas of basic physics
and astronomy contribute to our
understanding of the evolution of the
universe. Many unanswered questions may be
understood if we know the properties
of matter under extreme conditions. This new state of matter is produced
for the first time in New York State. First results of experiments at RHIC
will be discussed by Prof. Manly on
10/21 at 3.30 pm.