Overview of Astroparticle Physics 4 th Winter School on Astroparticle Physics Mayapuri, Darjeeling Rajarshi Ray Center for Astroparticle Physics & Space Science Bose Institute Kolkata 1

Album of the Universe 2

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. 3

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. 4

Particle Physics ~

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 6

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 – Relativistic equation for electron - Natural basis for electron spin - existence of antiparticle Discovery of positron – 1932 – Anderson – Cosmic Ray 7

Natural Units Velocity of light c = = 1 Planck’s Constant Temperature - Energy - Mass = MeV (10 6 eV)‏ Length - Time = fm ( m)‏ 8

Natural Units M e = MeV = 9.1 X Kg 1 M  (Solar Mass) = 2 X Kg Boltzman Constant k = 1.38 X J/ 0 k = 1 1 MeV (Temperature) = K 9

1929 – Quantum Electrodynamics - quantization of electromagnetic field - field quanta Photon - charged particles interact with the exchange of photon 10 Moller scattering Compton scattering Bhabha scattering

11 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 - 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

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 Gravitational and electromagnetic forces have infinite range; a=  For strong a ≈ cm = 1 fm 12

Yukawa Just as electron is attracted to nucleus by electric field, proton and neutron are also bound by field - what is the field quanta – pions – 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 13

Neutrino  decay – If A  B + e - Then 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   decay    µ+ & µ  e+2 (Powell) 14

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The strange particles – Rochester & Butler – Cosmic ray particle – passing through a lead plate – neutral secondary decaying into two charged particles K 0   + +  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 ???

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 19 So  belongs to baryon family – strange baryon

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= Strangeness – conserved - Strong production

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 21

Conserved quantum numbers 22

Zoo is crowded Too many inmates order required Periodic Table ~

The “Eightfold Way’’ - Murray Gell-Mann and Yuval Ne’eman, Baryon octet

25 Meson Octet

 - was predicted based on this arrangement and was discovered in Baryon decuplet

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 27

-1/3 +2/3Charge StrangeDownUpQuark K0K0 -- K+K+ ++ 0  0   K-K- K0K0 sd ud su du ds us uu,dd,ss Mesons qq 28

00 -- ++ ++ 0 0  -- 00 uss uus dss dds udd uud uds -- ddd  ++ uuu -- sss n p Baryons (qqq) Decuplet How can we have uuu,ddd or sss state ??? Need for a new quantum number Colour Charge Proposed by O. W.Greenberg 29 Conceptual problem? All naturally occurring particles are colourless

e-p scattering For smaller energy transfer the scattering is elastic For moderate energy transfer proton gets excited For Higher energies : Deep inelastic Scattering Can One estimate the energy Needed to probe proton??? Dimension – Atom m proton – 1fm = m Now use Uncertainty principle 30 Existence of quarks – experimental evidence

New Theory 31 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

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 32

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35 Strong force between protons  decay  0 strong decay

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 meson (called ) was discovered in 1974 In 1975 came the tau (  ) lepton and it continued. 36

Inclusion of strangeness Gell-mann-Nishijima-Nakano relation  Flavourudsctb Charge2/3-1/3 2/3 -1/3 I3I3 1/2-1/20000 Strangeness00000 Charm Top Bottom00000 Baryon No.1/3 SU(2) SU(3) SU(4) 37 For Baryons B=1 If for any Baryon Y≠1  Hyperon

Periodic Table - Today 38

Leptons are colourless 39

All quarks come in three colours 40

Mediating particles (radiation) 41 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

Consequences of quark structure 42

Single Baryon 43

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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 convert u & d to s 45

Strangelet  smaller lumps of strange quark mater SQM in bulk : charge neutrality with electrons For A  10 7 SQM size < compton wavelength of electron  Electrons are not localized n u = n d = n s  Net charge Q SQM = 0 if m s = m u = m d But m s > m u or m d  Q SQM > 0  small + ve charge 46

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 ~ Stability Problem ??? 2. Cosmic Ray events : Collision of Strange stars or other strange objects 47

48 SUMMARY Thank You

49 Classical Mechanics Quantum Mechanics Relativistic Mechanics Quantum field theory Small Fast