April 1, 2003Lynn Cominsky - Cosmology A3501 Professor Lynn Cominsky Department of Physics and Astronomy Offices: Darwin 329A and NASA EPO (707) Best way to reach me: Astronomy 350 Cosmology

April 1, 2003Lynn Cominsky - Cosmology A3502 Group 12  Patrick Colbus  Sara Corbett  Kimberly Ginthum

April 1, 2003Lynn Cominsky - Cosmology A3503 Extra credit  You can earn one extra point for each Space Mystery that you try out and evaluate at  Evaluation forms are found at:  The mysteries are: Live! From 2-alpha Alien Bandstand Starmarket  Evaluation forms must be turned in by 5/27/03 (day of final exam)

April 1, 2003Lynn Cominsky - Cosmology A3504 Big Bang Timeline We are here Today’s lecture

April 1, 2003Lynn Cominsky - Cosmology A3505 Atomic Particles  Atoms are made of protons, neutrons and electrons  % of the atom is empty space  Electrons have locations described by probability functions  Nuclei have protons and neutrons nucleus m p = 1836 m e

April 1, 2003Lynn Cominsky - Cosmology A3506 Leptons  An electron is the most common example of a lepton – particles which appear pointlike  Neutrinos are also leptons  There are 3 generations of leptons, each has a massive particle and an associated neutrino  Each lepton also has an anti-lepton (for example the electron and positron)  Heavier leptons decay into lighter leptons plus neutrinos (but lepton number must be conserved in these decays)

April 1, 2003Lynn Cominsky - Cosmology A3507 Types of Leptons LeptonCharge Mass (GeV/c 2 ) Electron neutrino 00 Electron Muon neutrino 00 Muon0.106 Tau neutrino 00 Tau175

April 1, 2003Lynn Cominsky - Cosmology A3508 Quarks  Experiments have shown that protons and neutrons are made of smaller particles  We call them “quarks”, a phrase coined by Murray Gellman after James Joyce’s “three quarks for Muster Mark”  Every quark has an anti- quark Modern picture of atom

April 1, 2003Lynn Cominsky - Cosmology A3509 Atomic sizes  Atoms are about m  Nuclei are about m  Protons are about m  The size of electrons and quarks has not been measured, but they are at least 1000 times smaller than a proton

April 1, 2003Lynn Cominsky - Cosmology A35010 Types of Quarks FlavorChargeMass (GeV/c 2 ) Up2/ Down-1/ Charm2/31.3 Strange-1/30.1 Top2/3175 Bottom-1/34.3  Quarks come in three generations  All normal matter is made of the lightest 2 quarks

April 1, 2003Lynn Cominsky - Cosmology A35011 Quarks  Physics Chanteuse Up, down, charm, strange, top and bottom The world is made up of quarks and leptons… Quark Sing-A-long

April 1, 2003Lynn Cominsky - Cosmology A35012 Combining Quarks  Particles made of quarks are called hadrons  3 quarks can combine to make a baryon (examples are protons and neutrons)  A quark and an anti-quark can combine to make a meson (examples are pions and kaons) proton meson  Fractional quark electromagnetic charges add to integers in all hadrons

April 1, 2003Lynn Cominsky - Cosmology A35013 Rules of the game activity  Analyze the observed particle events to see what the combination rules are

April 1, 2003Lynn Cominsky - Cosmology A35014 Color charges  Each quark has a color charge and each anti-quark has an anti- color charge  Particles made of quarks are color neutral, either R+B+G or color + anti-color Quarks are continually changing their colors – they are not one color

April 1, 2003Lynn Cominsky - Cosmology A35015 Gluon exchange  Quarks exchange gluons within a nucleon movie

April 1, 2003Lynn Cominsky - Cosmology A35016 Atomic Forces  Electrons are bound to nucleus by Coulomb (electromagnetic) force  Protons in nucleus are held together by residual strong nuclear force  Neutrons can beta-decay into protons by weak nuclear force, emitting an electron and an anti-neutrino F = k q 1 q 2 r 2 n = p + e +

April 1, 2003Lynn Cominsky - Cosmology A35017 Fundamental Forces  Gravity and the electromagnetic forces both have infinite range but gravity is times weaker at a given distance  The strong and weak forces are both short range forces (< m)  The weak force is times weaker than the strong force within a nucleus

April 1, 2003Lynn Cominsky - Cosmology A35018 Force Carriers  Each force has a particle which carries the force and is unaffected by it  Photons carry the electromagnetic force between charged particles  Gluons carry the strong force between color charged quarks 

April 1, 2003Lynn Cominsky - Cosmology A35019 Force Carriers  Separating two quarks creates more quarks as energy from the color- force field increases until it is enough to form 2 new quarks  Weak force is carried by W and Z particles; heavier quarks and leptons decay into lighter ones by changing flavor

April 1, 2003Lynn Cominsky - Cosmology A35020 Unifying Forces  Weak and electromagnetic forces have been unified into the “electroweak” force They have equal strength at m Weak force is so much weaker at larger distances because the W and Z particles are massive and the photon is massless  Attempts to unify the strong force with the electroweak force are called “Grand Unified Theories”  There is no accepted GUT at present

April 1, 2003Lynn Cominsky - Cosmology A35021 Gravity  Gravity may be carried by the graviton – it has not yet been detected  Gravity is not relevant on the sub-atomic scale because it is so weak  Scientists are trying to find a “Theory of Eveything” which can connect General Relativity (the current theory of gravity) to the other 3 forces  There is no accepted Theory of Everything (TOE) at present

April 1, 2003Lynn Cominsky - Cosmology A35022 Force Summary

April 1, 2003Lynn Cominsky - Cosmology A35023 Spin  Spin is a purely quantum mechanical property which can be measured and which must be conserved in particle interactions  Particles with half-integer spin are “fermions”  Particles with integer spin are “bosons” * Graviton has spin 2

April 1, 2003Lynn Cominsky - Cosmology A35024 Quantum numbers  Electric charge (fractional for quarks, integer for everything else)  Spin (half-integer or integer)  Color charge (overall neutral in particles)  Flavor (type of quark)  Lepton family number (electron, muon or tau)  Fermions obey the Pauli exclusion principle – no 2 fermions in the same atom can have identical quantum numbers  Bosons do not obey the Pauli principle

April 1, 2003Lynn Cominsky - Cosmology A35025 Standard Model  6 quarks (and 6 anti-quarks)  6 leptons (and 6 anti-leptons)  4 forces  Force carriers ( , W +, W -, Z o, 8 gluons, graviton)

April 1, 2003Lynn Cominsky - Cosmology A35026 Some questions  Do free quarks exist? Did they ever?  Why do we observe matter and almost no antimatter if we believe there is a symmetry between the two in the universe?  Why can't the Standard Model predict a particle's mass?  Are quarks and leptons actually fundamental, or made up of even more fundamental particles?  Why are there exactly three generations of quarks and leptons?  How does gravity fit into all of this?

April 1, 2003Lynn Cominsky - Cosmology A35027 Particle Accelerators  The Standard Model of particle physics has been tested by many experiments performed in particle accelerators  Accelerators come in two types – hadron and lepton  Heavier particles can be made by colliding lighter particles that have added kinetic energy (because E=mc 2 )  Detectors are used to record the shower of new particles that results from the collision of the particle/anti-particle beams

April 1, 2003Lynn Cominsky - Cosmology A35028 Particle Accelerators-SLAC  2 mile long accelerator which can make up to 50 GeV electrons and positrons  Now being used as an asymmetric B-meson factory, making Bs and anti-Bs out of 9 GeV electrons and 3.1 GeV positrons

April 1, 2003Lynn Cominsky - Cosmology A35029 Electron Interaction movies Electron - neutrino Electron - positron

April 1, 2003Lynn Cominsky - Cosmology A35030 SLAC B-factory  Goal is to understand the imbalance between matter and anti-matter in the Universe  1 out of every billion matter particles must have survived annihilation  Decay rates of Bs and anti-Bs should be different  Explanation goes beyond the standard model

April 1, 2003Lynn Cominsky - Cosmology A35031 FermiLab  5 accelerators which collide protons and anti-protons at 2 TeV Colliding Detector at Fermilab (CDF) D0

April 1, 2003Lynn Cominsky - Cosmology A35032 FermiLab  The top quark was discovered at Fermilab  Main goal is continued study of top quarks  Other experiments are looking for: matter/anti-matter asymmetry in decays of Kaons and other mesons formation of anti-hydrogen, charmonium (new state of matter made of charmed and anti-charmed quarks), matter made from charm + strange quarks, and charm quarks + light quarks Neutrino oscillations  Accelerator is undergoing a major upgrade so that it can produce more particles in the beam

April 1, 2003Lynn Cominsky - Cosmology A35033 FermiLab  Only 1 out of collisions produces a top quark  Computer analyzes detector pattern to find mesons, a positron and evidence for a neutrino  Physicists deduce that this pattern also requires a W and b quark which come from a top quark decay

April 1, 2003Lynn Cominsky - Cosmology A35034 A tour of the CDF detector  Virtual reality movie made at Fermilab by Joe Boudreau movie

April 1, 2003Lynn Cominsky - Cosmology A35035 Picturing Particles Activity  Analyze the events that are seen in different chambers of a detector  Determine the particles that could have made these tracks  Remember that positively charged particles curve opposite to negatively charged particles due to the magnet in the detector  Muons are not stopped by any of the layers – they travel through the entire detector  Electrons (positrons) and photons are stopped in the electromagnetic calorimeter layer  Hadrons are stopped in the hadron calorimeter

April 1, 2003Lynn Cominsky - Cosmology A35036 Figures for activity

April 1, 2003Lynn Cominsky - Cosmology A35037 CERN  European Center for Particle Physics  Near Geneva, on France-Swiss border  CERN had both electron- positron collider (LEP) and hadron collider (SPS)  LHC will be the world’s highest energy accelerator – now under construction

April 1, 2003Lynn Cominsky - Cosmology A35038 CERN  LEP detectors (designed to study weak force) Aleph (W boson mass, number of particle families, strong interaction strength) Delphi (identified leptons, photons and hadrons) L3 (Z 0 energy, other standard model parameters) Opal (detected Z 0, now looking for W + and W - pairs)

April 1, 2003Lynn Cominsky - Cosmology A35039 CERN  LHC detectors (designed to study 14 TeV energy scale, same as s after Big Bang) ATLAS (looking for the Higgs boson) CMS (Higgs, electro-weak symmetry breaking) ALICE (quark-gluon plasma studies) LHCb (matter/anti-matter asymmetry using B mesons)

April 1, 2003Lynn Cominsky - Cosmology A35040 In Search of the Higgs Boson  CERN LEP Turned off on 11/2/00 to build LHC – confirmed precise details of standard model  LEP’s last run produced hints for Higgs Boson at 115 GeV  Higgs boson is “cosmic molasses” – the Holy Grail of particle physics  Interactions with the Higgs Field are theorized to give all the particles their masses  LHC detectors should be able to confirm or disprove initial hints for Higgs at E=115 GeV

April 1, 2003Lynn Cominsky - Cosmology A35041 Web Resources  The Particle Adventure  SLAC  FermiLab  Virtual Space time travel machine demo_14.html  CERN  Particle Physics Education Sites