BASIC CONSTITUENTS OF MATTER AND THEIR INTERACTIONS D

BASIC CONSTITUENTS OF MATTER AND THEIR INTERACTIONS D. P. ROY Homi Bhabha Centre for Science Education Tata Institute of Fundamental Research Mumbai, India

Basic Constituents of Matter Undergone 2 Revolutionary Changes in the 20 th Century 1. Rutherford Scattering - 1911 p n e α Atom 2. SLAC e-p Scattering Expt. - 1968 1 Å = 10 -10 m q e- p q 1 fm = 10 -15 m

Nucleus made of p &n p, n (1933), mass ≈ 930 Me. V => I = ½, I 3 = ± 1/2, ΔI 3 = Δe = 1 p & n interact by exchanging π meson π n p Feynman diagram Uncertainty Principle : ΔEΔx ≈ ħc = 200 Me. V. fm mπ = 140 Me. V => range = 200 Me. V. fm/140 Me. V = 1. 4 fm Yukawa predicted π and its mass from range of nuclear int Bhabha gave the name meson because mp > mπ > me (0. 5 Me. V)

Uncertainty Principle : ΔE Δx > ħ c ~ 0. 2 Ge. Vfm x « 1 fm => E » 1 Ge. V (109 e. V) Energy of e- after passing through 109 Volts ħ & c = 1 => m = mc 2 : me ~ 0. 5 Me. V mp ~ 1 Ge. V (Common Unit of Mass & Energy) Nuclear Particles (Hadrons) are Quark Atoms: p (qqq), n (qqq), π(qq)

γ e p p γ e r e p EM Int of charged particles (QED) F = α/r 2 => V = α/r q q q g r q F = Constant => V → r q Strong Int of coloured particles (QCD) q Vector colour ch. => gluons carry colour ch. => Self int of gluons => Confinement p q q π exch force between p & n => Van der Waal force between atoms

Isospin, Weak Interaction & Neutrino: Isospin I 3 Quarks (Ch. ) Leptons(Ch. ) +1/2 u (+2/3) ν (0) -1/2 d (-1/3) e (-1) u e W- d ν

Basic Constituents of Matter Mass (Ge. V) Fermions (Spin = 1/2 ħ) Leptons νe νμ ντ e. 0005 μ 0. 1 τ 1. 8 e 0 -1 Quarks 2/3 -1/3 u 0. 3 d 0. 3 c 1. 5 s 0. 5 t 175 b 5 For each Pair : Δe = 1 => I 3 =± 1/2 (Weak Int) Quarks also carry Colour Charge (C)=>Strong Int

Carriers of Basic Ints. are Vector Bosons (Spin = 1ħ) => γ(0), g (0), W±(80 Ge. V), Z 0(91 Ge. V) • • p (uud), n (udd), e => All the Visible Matter Heavier Leptons & Quarks Decay by Weak Int They can be Observed in Accelerator or Cosmic ray Observation of μ and k (sū) in 1947 • νs are stable but very hard to Observe <= Weak Int • • νe Observed in Atomic Reactor Expt in 1956 νμ in BNL PS in 1962 ( KGF Cosmic ray in 1965) e+e- Collider : c (1974), τ (1975), b (1977), g (1979) p-p Collider : W & Z (1983), t (1995), ντ (2000) FT

Rotational invariance in 3 -dim Rotational invariance in 4 -dim = Lorentz inv (Relativity)

e. Bv = mv 2/R e. B = mv/R

e+e - ( p - p) Collider Accleration Mode Collision Mode Advantage of Collider over Fixed Target Accelerator E E Tevatron p-p Collider E’

p-p Collider vs e+e - Collider s’ s’ ~ < xq >2 sp-p 1/6 s’ s’ = se e+ CERN: p-p Coll. (ρ = 1 km), LEP-I (ρ = 5 km) COST: ( 200 + 100) million$, 1 billion$ Precission: Tune e-e+ Energy = MZ => Higher Rate & Better Mass Res Z events/yr : LEP-I ~ 10 6, CERN p-p Coll. ~ 10 1 -2 Signal : Clean , Dirty (Debris from Spectator q & g)

Past, Present & Proposed Colliders Period Machine Location 70’s SPEAR DORIS CESR PEP PETRA Stanford e+e. Hamburg Cornell Stanford Hamburg 80’s 90’s TRISTAN Japan SPPS CERN Beam Energy(Ge. V) Radius Highlight e+ epp Tevatron SLC LEP-I (LEP-II) HERA Fermilab p p Stanford e+e. CERN 2009 2? ? ? 3+3 5+5 8+8 18+18 22+22 30+30 300+300 125 m charm , τ bottom 300 m gluon 1 km W, Z boson 5 km Hamburg e p 1000+1000 50+50 100+100 30+800 LHC CERN pp 7000+7000 5 km ILC ? ? ? e+ e- 500+500 Top Z Z W Higgs, SUSY

k. T ~ ħ/1 fm~0. 2 Ge. V 3 -jets 80 Ge. V 91 Ge. V

Hard Isolated e / μ with 3 - 4 Hard jets 175 Ge. V 80 Ge. V Godbole, Pakvasa & Roy, Phys. Rev. Lett. 50, 1539 (1983) Gupta & Roy, Z. Phys. C 39, 417 (1988) Top pair production

India in the world of physics: Prof. A. N. Mitra Part VIII Physics in the small : Nuclei to Quarks In Part VII, we looked at the experimental status in our country for studies in various disciplines. In particular, experimental high energy physics (HEP) grew in a very modest way through cosmic ray studies wherein the Indian activities were duly subsumed in the global efforts. These, in turn, played a key role in the early evolution of concepts on the structure and interaction of elementary particles. We now come to our theoretical understanding of physics in the small and the large. Needless to mention that this theoretical understanding is an independent development, whose foundations were outlined in Part I. The unfolding of ‘physics in the small’ has been a long saga of discoveries in three successive stages, of which only the first (atomic) stage dominated by the electromagnetic interaction, was the subject of Part III. This theoretical narrative concerns the next two stages of matter, namely, mesons and baryons (hadrons) and leptons, to quarks, gluon and W, Z bosons as the carriers of strong and electroweak interactions. A most crucial concept that has played a key role (with firm experimental support) in building this huge infrastructure concerns the numbers of quarks and leptons (six varieties each) that are necessary for keeping theoretical framework anomaly-free. Especially the discovery of the top quark at the ‘right mass’ of 175 Ge. V, was an exciting finish (albeit delayed) in the race for this missing element after a hot chase. In this respect, an Indian contribution has been substantial, Durga Prasad Roy of Tata Institute of Fundamental Research (TIFR) being one of the first to predict the precise mass position of this elusive particle well in advance of its actual discovery (1995). A second pivotal link in theoretical framework is the so called Higgs particle, a fallout of the

WHY LHC?

Mass Problem : Higgs Mechanism How to give mass to the SU(2) Gauge Bosons w/o breaking Gauge Sym of the L ? For simplicity look at the U(1) Gauge Th (EM Int). -M 2 Aμ Aμ μ 2<0 μ 2>0 vev < m q = y qv ~ 102 Ge. V

g 2 Wμ Wμ q yq q Higgs couplings to Particles is Proportional to their Mass =>Most Important Channels for Higgs Search are the Heavy Pairs: h ( WW, ZZ, tt, bb, ττ ) & H± ( tb, τν+ ) h(125 Ge. V) W W W γ γ Z h Z e eμ+ μ-

Ferromagnetism T < TC Rotational Symmetry Broken T > TC Rotational Symmetry

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