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Introduction Big Bang Stellar structure & solar neutrinos. I. Stellar evolution & s process Supernovae & r process. II. III. Binary systems: Type Ia, novae, x-ray bursts. Nuclear astrophysics. A survey in 3 acts. Jeff Blackmon, Physics Division, ORNL.

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nuclear astrophysics

Introduction

Big Bang

Stellar structure & solar neutrinos

I

Stellar evolution & s process

Supernovae & r process

II

III

Binary systems: Type Ia, novae, x-ray bursts

Nuclear astrophysics

A survey in 3 acts

Jeff Blackmon, Physics Division, ORNL

  • Nuclear physics plays an important role in astrophysics:
    • Energy generation
    • Synthesis of elements

astronomical observables

interdisciplinary research
Interdisciplinary research

A variety of new tools in many areas are driving progress

Laboratory measurements

Nuclear theory and data

Improved shell model, reaction theory, rates, libraries & dissemination via the web

New beams & experimental techniques

Observations

Astrophysics

New orbiting instruments, increased optical power, presolar grains

Advancing computing power more realistic simulations

solar system abundances
Solar system abundances

One of the most fundamental and important observables

log (abundance)

This year marks the 50th anniversary of “B2FH”

Mass

nuclear reactions in the lab in space

reactions/s

ions/s

atoms/cm2

Nuclear reactions in the lab & in space

What you are used to in the lab:

cross section

reaction rate

In astrophysical events:

the coulomb barrier

MeV·fm

The Coulomb barrier

Energy of particles in astrophysical environments is much lower than the Coulomb barrier

why the s factor is useful
Why the S-factor is useful

Example: 3He(,)7Be

  • Important for:
    • The sun ( production)
    • Big Bang (Li production)

Rolfs&Rodney, p. 157.

Data from Kräwinkel et al., ZPA 304 (1982) 307.

Limit of experiments

Need  here for sun

But be careful…

identifying resonances is crucial

Gp>>Gg

Gg>>Gp

Identifying resonances is crucial

Lecture 3

Keiser, Azuma & Jackson, NPA331 (1979) 155.

If resonance is narrow

“resonance strength”

solving a reaction rate network

14O

15O

16O

1 m

2 m

13N

14N

15N

10 m

12C

13C

Solving a reaction rate network

Network of many coupled equations

The CN cycle: hydrogen burning

Identify important reactions

Nuclear physics  reaction rates

Astrophysical model to define the equations of state: , T

Numerically solve for Nx(t)

the early universe
The Early Universe

Space, time, matter, & energy began with the Big Bang

Independent observations tell us about different epochs

Nucleosynthesis

CMB -The afterglow

Stellar observations

Light Elements Formed

new cosmological paradigm
New Cosmological Paradigm

WMAP: CMB Observations

(Lecture 3)

Type 1a supernova redshift vs. distance indicates the expansion rate of the universe is accelerating

DARK ENERGY (e.g. cosmological constant) exerts a “negative pressure” causing the acceleration

Only 4% of matter is baryonic  test with nucleosynthesis

the homogeneous bbn model

proton

proton

neutron

neutron

2H

2H

3He

3He

4He

7Be

7Li

p ~75%

4He ~25%

2H,3He ~ 10-5

7Li ~ 10-10

The Homogeneous BBN Model

Assume adiabatic expansion ( flavors)

n/p ratio set by weak strength (n half-life)

Only free parameter is baryon/photon ratio

~All free neutrons into 4He

Mass 5 & 8 gaps inhibit formation of heavy elements

slide14

p

4He

d

3He

7Li

final

abun-

dances

Solve the reaction rate network

Time (sec)

1

100

300

start

finish

slide15

proton

neutron

2H

3He

4He

d / H abundance ratio

7Be

7Li

 = baryon / photon

Abundance Observations can be used to constrain the “normal” matter density - the free parameter in the theory - independent of WMAP

Theoretical

Abundance

Prediction

slide16

Quasi-Stellar Object (QSO)

(absorbs light)

d / H abundance ratio

hydrogen

Deuterium

abundance

observations

deuterium

range of densities

consistent with

observations & theory

Keck Telescopes

 = baryon / photon

“Primordial” Interstellar

Gas Cloud

D / H = 2.78 ± 0.4 • 10-5

Abundance Observations can be used to constrain the “normal” matter density - the free parameter in the theory - independent of WMAP

Theoretical

Abundance

Prediction

10-10

slide17

7Li: good constraint on baryonic matter density

4He: relatively weak constraint

but good observations?

Yp = 0.242 ± 0.002

7Li / H = 1. 0 – 1.6 • 10-10

7Li/ H abundance ratio

4He mass fraction

comparing matter density constraints

WMAP

using 7Li

using 4He

Disagrees with WMAP

Disagrees with WMAP

using 2H

Agrees with WMAP

Precision needs

improvement

Comparing Matter Density Constraints

“Gold Standard”

Highest precision

Independent of

how light

Elements formed

in Big Bang

1

2

3

4

5

6

7

8

• 1010 ~ normal matter density

Is our understanding of dark energy / dark matter is wrong?

Are our observations / interpretations wrong?

Are there problems with our nuclear reaction network?

slide19

Enables users to run and visualize BBN calculations with

choice of reaction rateschoice of primordial abundance observationschoice of standard BBN or some non-standard variants

New online suite of cosmology codes under development at bigbangonline.org

hydrogen burning in stars
Hydrogen burning in stars

DP

G

Hydrostatic equilibrium

Energy conservation

The sun

M=2x1030 kg

(0)=150 g/cm3

T(0)=1.5x107 K

T(surf)=5800 K

L=3.8x1026 W

Pressure

For sun (non-degenerate)

Large T,P gradient

Opacity: photons absorbed and emitted at shorter 

5x104 yr for energy produced in sun’s core to be radiated at surface

LM4

Luminosity/opacity/T relationship

slide21

Thanks to substantial efforts in experiment, theory & evaluation

5%

5%

7%

7%

13%

5-10%

Solar power:

slide22

Super-K

1967

1996

6x109ne/cm2/s

only direct probe of solar core

Homestake

Homestake

Super-K

2002 Nobel Prize

Davis & Koshiba

Radiochemical

Real-time counting

Homestake

Homestake Gold Mine

600kt perchloroethylene

100 events/yr

37Cl+ne 37Ar+e

~30% expectations

Mozumi Mine

50,000 kt water

5,000 events/yr

ne+ e- scattering

~40% expectations

slide23

SNO

1998

SNO NC = (5.21  0.27stat 0.38sys) x 106 /(cm2s)

metallicity

reaction rates

 ~15%

SNO & SuperK measure only neutrinos from the decay of 8B

Flux measurements determine neutrino properties

n

7Be(p,g)8B

A accurate value for the predicted 8B neutrino flux is need for comparison to the current generation of measurements

SuperK CC = (2.39  0.03stat 0.06sys) x 106 /(cm2s)

Creighton Nickel Mine

1 kt heavy water

nx + d  p + n

SSM = 5.7 x 106 /(cm2s)

slide24

Flavor oscillation

P(nenm)

  • Neutrino mass eigenstates not the same as flavor eigenstates

In vacuum

  • Strong evidence from observations of atmospheric neutrinos ( )
  • Observed in reactor experiments: KamLAND & Chooz
  • Oscillations of solar (8B) neutrinos are enhanced by interactions with the high density of electrons in the solar core

MSW: Mikheyev & Smirnow, SJNP 42 (85).

Wolfenstein, PRD 17 (78).

  • 7Be = Focus of current experiments
    • KamLAND
    • Borexino
  • pp = Next-generation
    • CLEAN
    • LENS

7Be

pp

KamLAND

slide25

October 2004

One of the 3 major recommendations

“Thereareraremomentsinsciencewhenaclearroadtodiscoveryliesaheadand there is broad consensusaboutthestepstotakealongthatpath This is one such moment.”

  • The pp neutrino flux is accurately predicted by the solar luminosity.
  • pp neutrinos oscillate (primarily) by vacuum oscillations not MSW oscillations.
  • Would provide a clear test of solar physics, hydrostatic equilibrium, etc.
  • Is the sun’s energy output now the same as 50,000 years ago?
measuring the pp flux clean

McKinsey & Coakley, Astroparticle Physics 22 (2005) 355.

Measuring the pp flux: CLEAN

Very high purity liquid Ne or Ar

Thin film of shifting flour in front of PMTs

Good recoil/electron discrimination

Very low threshold (few 10’s keV)

130 ton device proposed (either SNO-Lab or DUSEL)

MiniCLEAN now operating

65 liters

lens e from pp fusion

Now: 8% In-loaded scintillator

Background

2x 115In decays

1 mimics prompt e

1 mimics g cascade

 high segmentation

air

In-loaded scintillator

LENS: e from pp fusion

#1 prompt electron

 e energy (-like)

signal #1

signal #2

Buffer up to 10s

Shower

Time/space correlation

discrimination

3D array of transparent cells

(~6 m)3 fiducial volume = ~15 tons In

~ 500 pp events/yr

nuclear physics laboratory measurements
Nuclear Physics Laboratory Measurements

beam

detectors

target

small

accelerator

ion source

Directly measure cross sections in the lab at the lowest possible energies

Bombarding energy range ~ 10 keV to 3 MeV

  • High currents (~ mA)
  • Long run times
  • Efficient detectors to obtain high statistics
  • Pure, stable targets
  • Absolute cross section measurements
    • Good normalization & careful control of systematic uncertainties
  • Background suppression crucial
slide29

LNGS

ROME

Laboratory space adjacent to highway tunnel

1400 m rock coverage

cosmic µ reduction= 10–6

µ rate ~ 1 (/m2 h)

slide30

Low-energy accelerators at LNGS

50 keV accelerator

First  measurements in solar Gamow widow

3He()7Be with

400 keV accelerator

3He(3He,2p)

R. Bonetti et al., PRL 82 (1999) 5205.

3 he 7 be @ luna

PRL 48 (1982)

PRC 27 (1983)

ZPA 310 (1983)

PRL 93 (2004)

Gy. Gyürky, PRC 75 (2007) 035805.

3He()7Be @ LUNA
7 be p 8 b at seattle

7Be Target

Rotating target

arm

450mm2,Ep=305 keV

Faraday Cup

22.3 ± 0.7 eV barn

150mm2,Ep=305 keV

22.1 ± 0.6 eV barn

Proton beam going

through LN2 trap

Junghans et al., PRC 68 (2003) 065803.

7Be(p,)8B at Seattle

Si detectors

Extraordinary control over systematic uncertainties.

slide33

New Coulomb dissociation result

Schumann et al., PRC 73 (2006) 015806.

Small E2

Change in S17(E)

20.60.81.2 eV b

recent 7 be p 8 b results

Schumann (CD 2006)

Trache (Glauber 2004)

Schumann (CD 2003)

Davids & Typel (CD 2003)

Azhari (ANC 2001)

Evaluated S17 (eV b)

Junghans PRC 68 (2003) 065803.

21.40.50.6

Davids & Typel PRC 68 (2003) 045802.

18.60.41.1

Cyburt et al., PRC 70 (2004) 045801.

19.3  21.4

with ~ 6-7% 

Recent 7Be(p,)8B results

Junghans et al.

  • Precision has been significantly improved.
  • Some questions remain.
  • Additional high-precision measurement(s) are desired.
slide35

Thanks to substantial efforts in experiment, theory & evaluation

5%

5%

7%

7%

13%

5-10%

Solar power: