Dept of Physics “Particle” Pradipta Ghosh th 12 March, 2019 March 12, 2019 1 / 30 1993 The Birth of God Particle Traveling Back In Time March 12, 2019 2 / 30 The Birth of God Particle: Meet the Creators Englert, Brout, Phys. Rev. Lett. 13, 321, 31 August 1964 Broken Symmetry and the Mass of Gauge Vector Mesons Higgs, Phys. Rev. Lett. 13, 508, 19 October 1964 Broken Symmetries and the Masses of Gauge Bosons Guralnik, Hagen, Kibble, Phys. Rev. Lett. 13, 585, 16 November 1964 Global Conservation Laws and Massless Particles Contributors over years: Anderson, Brout, Englert, Guralnik, Hagen, Higgs, Kibble, and 't Hooft Peter Higgs: It’s not Higgs boson but ABEGHHK'tH boson March 12, 2019 3 / 30 The Birth of God Particle: The Man Behind the Myth 1993 1988 Leon Max Lederman 1922 - 2018 “ the effort to reduce all the operations of nature to a small number of laws governing a small number of primordial objects” March 12, 2019 4 / 30 1993 Asgard for God Particle ? Asgard of God Particle The Standard Model (SM) of Particle Physics Asgardians Elementary Particles Basic Interactions and mediators March 12, 2019 5 / 30 Theory: Glashow, 1961, Weinberg, 1967, Salam, 1968 1979 Sheldon Steven Abdus Glashow Weinberg Salam Theory: Greenberg, 1964, Han, Nambu, 1964, Bardeen, Fritzsch, Gell-Mann, 1973 Creators of Asgard Theory: 1973 C. R. Tom Gerald 2004 Hagen Kibble Guralnik David H. D. F. Wilczek Gross Politzer Theory: Nambu, Peter François Jona-Lasinio 1961 Higgs Englert 1999 Gerard Martinus Robert 2008 't Hooft J. G. Veltman 2013 Brout Yoichiro Nambu Theory: Brout, Englert, Higgs, Guralnik, Hagen, Kibble, 1964 March 12, 2019 6 / 30 Asgardians for God Particle Basic Interactions and mediators X Gravity is not included in the SM Mediated by t n e March 12, 2019 7 / 30 Gluons (g) r e f f i d e r Photon (γ) a s n o + - i t W , W , Z c a r e t n I Graviton (?) Asgardians for God Particle Elementary Particles Elementary: fundamental till date March 12, 2019 8 / 30 Asgardians for God Particle Elementary Particles In SM neutrinos are massless 1 eV/c2 = 1.783×10−36 kg C = 1 in natural unit system March 12, 2019 9 / 30 Muon S. Neddermeyer Electron The Particle Hunters (1936) (1897) Theory: Pauli, 1930 Tau e-Neutrino (1975) (1956) 1995 Martin Clyde C. D. Anderson Cowan 1995 1906 Lewis Perl Frederick m-Neutrino (1962) Carlo Rubbia Reines J. J. Thomson Theory: 1940 Theory: 1970 t-Neutrino (2000) Simon van der Meer DONUT Coll. 1984 1988 W+,W-,Z UA1, UA2 (1983) CERN Leon M. Melvin Jack Theory: Glashow, Weinberg, Salam, 1968 Steinberger Lederman Schwartz Theory: 1973 Gluons DORIS (1978) PETRA (1979) Light quarks DESY (up,down,strange) 2008 SLAC (1968) Theory: Gell-Mann, 1962 T. Maskawa M. Kobayashi 1976 Bottom quark Top quark FermiLAB CDF & D0 Burton Samuel (1977) Richter Ting (1995) 2013 1969 Charm quark Higgs boson Peter François Murray George SLAC,BNL (1974) ATLAS, CMS (2012) Higgs Englert Gell-Mann Zweig Theory: Glashow, LHC-CERN Theory: 1964 Iliopoulos,Maiani, 1970 Theory: Brout, Englert, Higgs, Guralnik, Hagen, Kibble, 1964 March 12, 2019 10 / 30 Inside Asgard of Particle Physics The Standard Model Clients Postman Interaction Mediators Acts on Strong Gluons Quarks & Gluons Letters Electromagnetic Photon Charged leptons, W, quarks Leptons, Quarks Weak W, Z W, Z, Higgs March 12, 2019 11 / 30 The need of God Particle Asgard of Particle Physics is ruled by symmetry laws Those laws forbid mass terms Most of the elementary particles are massive in nature !! Asgard of Particle Physics seeks protection from symmetry Demons March 12, 2019 12 / 30 When Symmetry Forbids Consider the following English alphabets: M,N,O,P 1. Vertical mirror M M O O Reflection symmetry M, O survive 2. Horizontal mirror lll M O Kiil O Reflection symmetry M s oe Only O survives do try me mm Sy March 12, 2019 13 / 30 Observation: Asgard of Particle Physics is ruled by Gauge symmetries Mass terms are forbidden Crisis: Most of the elementary particles and force mediators are massive Solutions: Spontaneous symmetry breaking and ABEGHHK'tH mechanism Thanks to God Particle March 12, 2019 14 / 30 Spontaneous symmetry breaking Not the place of minimum Energy Place of minimum Energy: Ground State Will remain same under rotations All directions on this Grey circle are the same from Pencil’s viewpoint Ground State is not unique The ground state now has a SPECIFIC direction The Rotational symmetry is Broken Spontaneously without any external influence March 12, 2019 15 / 30 Spontaneous symmetry breaking in the SM GOD is Here Unbroken symmetry Spontaneously broken symmetry “ GOD Particle’s ” Potential March 12, 2019 16 / 30 When Massless becomes Massive: ABEGHHK'tH mechanism W+ W- W3 B 4 X 2 + 4 =12 DOF Gauge Sector: All Massless with 2 DOF Unbroken gauge symmetries H+ H- H0 Would be God Higgs sector: Each with 1 DOF Degrees Of Freedom: Independent Translation / Rotation / Vibration March 12, 2019 17 / 30 When Massless becomes Massive: ABEGHHK'tH mechanism Massless Photon with 2 DOF W+ W- Z0 γ W3 W3 B B Three Massive with 3 DOF each Massive God Particle Spontaneously broken with 1 DOF gauge symmetries 3 X 3 + 2 + 1 =12 DOF match ✔ Leptons & Quarks masses through Yukawa interactions Gluons remain massless March 12, 2019 18 / 30 What took it so long? Electron (1897) J. J. Thomson J. J. Thomson 115 Years Higgs boson (2012) Brout, , , Englert Higgs Guralnik, Hagen, Kibble March 12, 2019 19 / 30 From LEP to LHC: The quest for God Particle Large Electron Positron Collider a.k.a LEP Energy ~200 GeV e+ e- collider Length probed ~ 10-18 m 1989 - 2000 Insufcient energy to detect God Particle Predicted Lower bound ~ 114 GeV Energy ~2000 GeV 1987 - 2011 Length probed ~ 10-19 m Not a correct probe for God Particle p p collider Predicted Exclusion limits With 1 GeV we can probe a distance of 10-15 m March 12, 2019 20 / 30 From LEP to LHC: The quest for God Particle Large Hadron Collider a.k.a LHC Energy ~ 14000 GeV P P collider Length probed ~ 10-20 m Discovery Machine 2010 - Can not use for precision study th 4 July 2012: CMS & ATLAS announced God Particle Discovery The Saga of the SM Ends here ? How large is 14 TeV ~ Kinetic Energy of a Ping-Pong ball (~3 gm) moving with a speed of ~4 cm/sec March 12, 2019 21 / 30 Eminence of the SM Anomalous Magnetic Moment of muon March 12, 2019 22 / 30 God Particle is here... It's All Over or NOT ? Asgard of Particle Physics is complete now but is it SAFE ? No it’s NOT ! March 12, 2019 23 / 30 God Particle itself is the most SERIOUS threat ! Suppose SM is the only theory for Particle Physics It should work till 1019 GeV, a.k.a. Planck Scale, realm of GRAVITY Quantum corrections Should make the Higgs much heavier than what it is However, it’s ~125 GeV ! UNNATURAL FINE TUNING for Higgs Mass It’s like a snowball surviving in hell March 12, 2019 24 / 30 Another troublesome Asgardian: Neutrino Neutrinos are Massless within the SM Neutrinos oscillate in nature: Observed Takaaki Theory: Pontecorvo, 1957, 1967, Arthur Maki, Nakagawa, Sakata, 1962 McDonald Kajita 2015 Oscillation impossible WITHOUT Neutrino mass Not within the SM March 12, 2019 25 / 30 Dark Matter: Enemy ‘beyond’ Asgard Galaxies must have some massive non-luminous matter, i.e., DARK Matter Beyond the LHC if anything matters, it is the Dark Matter which does matter... (anonymous) Many more drawbacks of the SM are there... March 12, 2019 26 / 30 We NEED to look for a “BETTER” Asgard March 12, 2019 27 / 30 Life at the LHC after God Particle God Particle discovered but NOTHING ELSE since 2012 LHC will be back with 14 TeV at 2021 High-Luminosity (HL)-LHC from 2026 Proposed International Linear Collider (ILC) 500-1000 GeV, Precision studies Proposed Compact Linear Collider (CLIC) Upto 3000 GeV, Precision studies Hope Survives Proposed Triple LEP Collider (TLEP) 80-100 km tunnel, 90-350 GeV, Precision studies 33 TeV, 100 TeV colliders Discovery machines March 12, 2019 28 / 30 God Particle discovery: Could be the beginning of a new journey So far it seems like THIS IS THE ONE and NOTHING ELSE, but who knows... ? This may be the ? tip of the iceberg... ? ? 125 GeV March 12, 2019 29 / 30 March 12, 2019 30 / 30.