Transcript SOME ASPECTS OF STRANGE MATTER : STARS AND

Overview of Astroparticle
Physics
4th Winter School on Astroparticle Physics
Mayapuri, Darjeeling
Rajarshi Ray
Center for Astroparticle Physics & Space Science
Bose Institute
Kolkata
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Album of the Universe
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Content of the Universe- Today
• Dark Energy ~ 73%
• Dark Matter ~ 23%
• Rest of it is whatever we see and know of!!
We see today matter as small as elementary
particles to as large as galaxies and cluster
of galaxies.
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Particle Physics in Astrophysics
 Identifying the elementary particles
(cosmic rays) and their formation
mechanisms.
 The primordial quantum mechanical
fluctuations that serve as starting point in
large scale structure formation.
 Properties of the dark side of the Universe.
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Particle Physics ~ 1870
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More Elementary Particles
• electrons (1897) J.J.Thomson
– orbit atomic nucleus
• photon (1905) Einstein
– quantum of the electromagnetic field
• Rutherford Experiment (1909)
– nucleus : occupies only a small fraction of the atom
• proton (1919)
– nucleus of lightest atom
• neutron (1932) Chadwick – Beryllium bombarded by  particle
- highly penetrating radiation
– neutral constituent of the nucleus
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Spin and anti-particles
• Pauli – 1924 – suggested additional quantum number for
electron in an atom which could take two values
• Goudsmit & Uhlenbeck – 1925 – explained the fine
structure in atomic spectra – introduced spin angular
momentum for electrons in addition to orbital angular
momentum
• Dirac – 1927 - Relativistic equation for electron
- Natural basis for electron spin
- existence of antiparticle
• Discovery of positron – 1932 – Anderson – Cosmic Ray
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Natural Units
Velocity of light c =
m
8
310
sec
=1
1
sec.

3

10
m
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Planck’s Constant
 1.051034J sec.
16
6.610 eVsec.
1
19
(1eV1.610 J)
Temperature - Energy - Mass = MeV (106 eV)
Length - Time = fm (10-15 m)
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Natural Units
Me = 0.511 MeV = 9.1 X 10-31 Kg
1 M (Solar Mass) = 2 X 1030 Kg
Boltzman Constant k = 1.38 X 10-23 J/ 0k = 1
1 MeV (Temperature) = 1010 0K
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• 1929 – Quantum Electrodynamics
- quantization of electromagnetic field
- field quanta
Photon
- charged particles interact with the exchange of photon
Moller scattering
Crossing Symmetry
if A  B  C  D is allowed
then A  B  C  D
AC  BD
C  D  A  B are allowed
Compton scattering
Bhabha scattering
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Incidentally, issue of behaviour of radiation as particle – the photon –
was finally settled in 1923 by A. H. Compton. Compton found that the
light scattered from a particle at rest is shifted in wavelength as given
by
      (1  cos  )
c
  scattering angle
- incident wavelength,  - scattered wavelength,
c =h/mc = Compton wavelength of the target particle (compare it
with de-Broglie wavelength)
Apply laws of conservation
of relativistic energy and
momentum
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•
What binds proton and neutron in the nucleus??
• Positively charged protons should repel each other.
•
some force stronger than electromagnetic force
- STRONG FORCE
•
First evidence – 1921 – Chadwick & Bieler
 scattering on hydrogen can not be explained by Coulomb
interaction only
• Why we do not feel this force everyday?
- must be of short range
er / a
F~ n
r
Gravitational and electromagnetic forces have infinite range; a=
For strong a ≈ 10-13 cm = 1 fm
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• Yukawa -1934
Just as electron is attracted to nucleus by electric
field, proton and neutron are also bound by field
- what is the field quanta – pions
- 1947 – two particle discovered by Powell and
co-workers
- one is pion which is produced copiously in the
upper atmosphere but disintegrates before
reaching ground
- the other one was muon - pion decays into
muons which is observed at the ground level
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Neutrino
•  decay – If A  B + eThen for fixed A, the energy of electron will be
fixed.
Experimentally, electron energy was found to be
varying considerably
Presence of a third particle – Pauli
Fermi theory of  decay – existence of neutrino
- massless and chargeless
 Decay  n  p  e  
 decay    µ+ & µe+2 (Powell)
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The strange particles
1947 – Rochester & Butler – Cosmic ray particle – passing through a
lead plate – neutral secondary decaying into two charged particles
K0  + + 1949 - Powell – K+ (+) + + + + K+ (+) + + 0
 -  puzzle – Parity violation in
weak decays
K particles behave as heavy pions
K mesons (strange meson)
1950 – Anderson – photograph similar to
Rochester’s
  p+ +  Belongs to which family ???
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•
proton does not decay to neutron – smaller mass
•
Also p+
e+ +  does not occur. WHY???
• 1938 Stuckelberg - Baryon no. conservation
• Baryon no. is conserved in Electromagnetic, weak and strong
interactions
So  belongs
to baryon
family –
strange
baryon
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• Strange particles
• Gell-Mann & Nishijima – Strangeness (S) - new Quantum number
like lepton no., baryon no. etc
• Strangeness is conserved in EM and Strong interactions but not
in weak interactions
Strangeness not conserved
K meson – S=+1
- Weak decay
 and  - S= -1
Strangeness – conserved
- Strong production
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Isospin
• After correcting for the electromagnetic interaction, the forces
between nucleons (pp, nn, or np) in the same state are almost the
same.
• Equality between the pp and nn forces:
• Charge symmetry.
• Equality between pp/nnforce and np force:
• Charge independence.
• Better notation: Isospin symmetry;
• Strong interaction does not distinguish between n and p  isospin
conserved in strong interaction
• BUT not in electromagnetic interaction
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Conserved quantum numbers
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Zoo is crowded
Too many inmates
order required
Periodic Table ~ 1960
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The “Eightfold Way’’
-
Murray Gell-Mann and Yuval Ne’eman, 1961
Baryon octet
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Meson Octet
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Baryon
decuplet
- was predicted based on this arrangement and was discovered in
1964.
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• Why do the hadrons (baryons and mesons) fit so beautifully????
•
Gell-Mann & Zewig proposed independently (1964)
•
Hadrons are composed of spin ½ QUARKS – comes in three
types or flavours
Every baryon (antibaryon) consist of 3 quarks (antiquark) and
each meson is composed of a quark and an antiquark
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Quark
Charge
Up
+2/3
Mesons
qq
Down
-1/3
Strange
-1/3
K0
K+
ds
us
-
+
0  
du
ud
uu,dd,ss
su
sd
K-
K0
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Baryons (qqq) Decuplet
-
0
+
++
ddd
udd
uud
uuu
n
p
Conceptual problem?
0 
dds
+
uus
uds
dss
uss
-
0
How can we have
uuu,ddd or sss state ???
Need for a new
quantum number
-
Colour Charge
sss
Proposed by O. W.Greenberg
All naturally occurring particles are colourless
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Existence of quarks – experimental evidence
• e-p scattering
• For smaller energy transfer the scattering is elastic
• For moderate energy transfer proton gets excited
e p  e   e p  0
For Higher energies : Deep inelastic Scattering
Can One estimate the energy
Needed to probe proton???
Dimension –
Atom 10-10 m
proton – 1fm = 10-15m
Now use Uncertainty principle
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• New Theory
Electrons – electric cherge - EM force – Photon
Quantum Electrodynamics
Quarks - Colour Charge - Strong force – Gluon
Quantum Chromodynamics
Quark – three colours - Red , Blue , Green
Gluons – eight - red + anti-blue and other combinations
Mesons – quark+antiquark – colour+anticolour – WHITE
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Photons – No self Interaction
- Abelian theory (QED)
- interaction increases with
decreasing separation between
particles
Gluons – colour charge
- Self interacting
- Non-abelian theory (QCD)
- interaction decreases with
decreasing separation between
particles i.e quarks
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Strong force
between protons
0 strong decay
 decay
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Story of quarks continues ….
• Quark family does not end with u,d and s
as lepton family does not end with e, e , µ, µ
• Bjorken and Glashow – fourth flavour of quark
charm c
• c c meson (called
J /
) was discovered in 1974
• In 1975 came the tau () lepton and it continued.
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BS
Y

Q

I


I

3
3

2
2

Gell-mann-Nishijima-Nakano relation 
Hypercharg e Y  B  S
~

In general Y  B  S  C  B  T

For Baryons
Flavour
u
d
s
c
t
b
B=1
Charge
2/3
-1/3 -1/3 2/3 2/3 -1/3
If for any Baryon
I3
1/2
-1/2 0
0
0
0
Y≠1Hyperon
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Inclusion of strangeness
Strangeness
0
0
-1
0
0
0
Charm
0
0
0
1
0
0
Top
0
0
0
0
1
0
Bottom
0
0
0
0
0
-1
Baryon No.
1/3
1/3
1/3
1/3
1/3
1/3
SU(2)
SU(3)
SU(4)
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Periodic Table - Today
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Leptons are colourless
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All quarks come in three colours
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Mediating particles (radiation)
The weak and electromagnetic interactions were unified by Glashow,
Salam and Weinberg
-predicted W and Z bosons with masses 80 GeV and 91 GeV
-Discovered in 1983
Together we have Standard Model of particle physics
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Consequences of quark
structure
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• Single Baryon
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Hadronic matter  Phase transition  Quark matter
Strange Quark Matter (u,d & s )  Ground state of matter
First idea : Bodmer (1971)
Resurrected : Witten (1984)
Stable quark matter : Conflict with experience ????
2-flavour energy  3-flavour
Lowering due to extra Fermi well
Stable Quark Matter  3-flavour matter
Stable SQM  significant amount s quarks
For nuclei  high order of weak interaction to convert45 u
& d to s
Strangelet  smaller lumps of
strange quark mater
SQM in bulk : charge neutrality with electrons
For A  107
SQM size < compton wavelength of electron


Electrons are not localized
nu = nd = ns
Net charge QSQM = 0 if ms = mu = md
But ms > mu or md

QSQM > 0  small + ve charge
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SQM & Strangelet Search :
SQM :
1. Early universe quark-hadron phase transition
Quark nugget  MACHO
2. Compact stars (Core of Neutron Stars or Quark Stars)
Strangelets :
1. Heavy Ion Collision
Short time
Much smaller size A ~ 10-20
Stability Problem ???
2. Cosmic Ray events :
Collision of Strange stars or other strange objects
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SUMMARY
Thank You
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Small
Fast
Classical
Mechanics
Quantum
Mechanics
Relativistic
Mechanics
Quantum
field theory
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