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PHY313 - CEI544 The Mystery of Matter From Quarks to the Cosmos Spring 2005 Peter Paul Office Physics D-143 www.physics.sunysb.edu PHY313 Peter Paul 03/17/05 PHY313-CEI544 Spring-05 1 What have we learned last time • This leads to the Standard Model • The six quarks that are the building blocks of strongly interacting matter have six equivalent particles that are responsible for the weak interaction. • These are the three lepton families: – lepton and neutrino – μ lepton and μ neutrino – electron and e- neutrino • The strong interaction is mediated by the gluons which transfer “color” between quarks. There are 8 gluons. • The weak interaction is mediated by the W± and the Z0 bosons. These are VERY massive particles which is why the very weak interaction. has very short range. The EM interaction is mediated by the photon Peter Paul 03/17/05 PHY313-CEI544 Spring-05 2 What have we learned last time II • We can prove that Leptons come in only 3 families. Thus it is suggestive that quarks also have only 3 families. • Quarks all have masses. Some leptons have masses, but neutrinos may not. Why should they not have mass? • The Standard model divides particles into fundamental building blocks which have spin ½ or 3/2. and are called Fermions. The second group are the force carriers. They have spin 0 or (mostly) spin 1 and are called Bosons. • Why do we have these two groups? Are they distinct and separate? Peter Paul 03/17/05 The puzzle of the masses of the quarks: • The proton is made up of 2 up quarks and one down quark: uud. • Each bare quark has a mass of only about ~ 2 MeV, • Yet the proton has a mass of 938 MeV: Where is all that additional mass coming from? PHY313-CEI544 Spring-05 3 The three quark families Spin Charge First family Second family Third family 1/2 +2/3 up (3 MeV) charm (1300 MeV) top (175,000 MeV) 1/2 -1/3 down (6 MeV) strange (100 MeV) bottom (4,300 MeV) Note that the neutron and proton and the light mesons are all build up of the lightest quarks, the u and d (and their anti-quarks in the meson case). http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html Peter Paul 03/17/05 PHY313-CEI544 Spring-05 4 Evolution of the Universe ~ 10 ms after Big Bang Hadron Synthesis T = 1.7 1012 K (~ 170 MeV) strong force binds quarks and gluons in massive objects: p & n; mass ~ 1 GeV ~ 100 s after Big Bang T = 109 K Nucleon Synthesis strong force binds protons and neutrons into nuclei QCD: Quantum Chromo Dynamics the theory of the strong interaction Confinement & Chiral Symmetry • Unbound quark has ~1 MeV • The bound (Constituent) quarks ~ 300 MeV Peter Paul 03/17/05 PHY313-CEI544 Spring-05 5 QCD Matter at High Temperature and Density nuclear matter p, n Quark-Gluon Plasma q, g density or temperature QCD potential that binds quarks 1. in vacuum: • linear increase with distance • strong attractive force • confinement of quarks to hadrons : baryons (qqq) and mesons (qq-bar) 2. in dense and hot matter • screening of color charges; Debye screening •potential vanishes for large distance • deconfinement of quarks QGP Peter Paul 03/17/05 PHY313-CEI544 Spring-05 6 The Phases of Water as Model for Quark Matter Peter Paul 03/17/05 PHY313-CEI544 Spring-05 7 QCD predictions from exact calculations Results from lattice QCD establish the QCD phase transition and chiral symmetry transition at T~ 270 MeV Karsch, Laermann, Peikert (99) eC = 0.6 GeV/fm3 TC ~ 170 MeV Calculation indicates a big jump in energy density: At temperature… TC ~ 170 MeV eC = 0.6 GeV/fm3 T ~ 220 MeV e = 3.5 GeV/fm3 Peter Paul 03/17/05 PHY313-CEI544 Spring-05 8 The QCD Phase Diagram Line of phase transition • Hadronic matter can be plotted in a phase diagram which plots the matter temperature versus the matter density (“Baryon chemical potential”). •At high temperature (170 MeV for = 0) or high density ( ~ 5 – 1- times nuclear density) normal hadronic matter turns into a quark-gluon plasma. Peter Paul 03/17/05 PHY313-CEI544 Spring-05 9 Energetic Gold collisions simulate early Universe • Create QGP as transient state in heavy ion collisions up to 400 nucleons in close proximity – verify experimentally existence of QGP – study QCD confinement of quarks to hadrons – study how hadrons get their masses • Retrace spontaneous breaking of chiral symmetry Turn “chiral quarks ( ~ 5 MeV for u,d ) into constituent quarks ( ~ 300 MeV for u,d) • Exploration of QCD many-body states using p-A and e-A collisions – Discover Color Spin Glass (saturated gluonic matter) Peter Paul 03/17/05 PHY313-CEI544 Spring-05 10 Schematic View of a Heavy Ion Collision b~0 projectile p J/ target K p cc p p p p p e- p p e+ Several 1000 particles are produced in central collisions, i.e. when projectile and target hit head on • Lots of hadrons ( p, K, p ) are produced when particles stop to interact (freeze-out), i.e. at the end of the collision • A few quanta of EM radiation or lepton pairs are emitted from the hot collision zone • http://www.bnl.gov/rhic/heavy_ion.htm Peter Paul 03/17/05 PHY313-CEI544 Spring-05 11 Violent collisions free up lots of particles The particles are tracked in large detectors at RHIC such as STAR (left) and PHENIX (right) Peter Paul 03/17/05 PHY313-CEI544 Spring-05 12 Relativistic Heavy Ion Collider (RHIC) Peter Paul 03/17/05 PHY313-CEI544 Spring-05 13 Evolution of nuclear accelerators • Use of particle accelerators for NP began in the 1920’s with Cockcroft and Walton and advanced in the 1930’s with invention of the cyclotron by Lawrence. • Cyclotrons were the workhorses in the 1950’s because of their ruggedness. • In 1960 the first high-energy synchrotron was invented. It is still working today as the AGS at BNL • In the 1960’s electrostatic accelerators became widely used with the introduction of the Van de Graaf accelerators. • In the 1970’s linacs came into wider use with superconducting technology. • In the 1970’s colliders were invented which pushed the collision energy much higher • Today the LHC at CERN is being completed as the world’s largest accelerator Peter Paul 03/17/05 PHY313-CEI544 Spring-05 14 Acceleration with DC or AC Electric Fields • Acceleration is done by the Coulomb force acting on the positive or negative charge of the accelerated particle. • These can be electrons, protons or heavy ions. For example RHIC uses Au beams stripped bare (q = 79 x e ) • Acceleration principle is very simple: E= q V where q = n x e. V can be a positive or negative voltage depending on what charge is being accelerated . • Typical voltages can be 1 MV/m or even 70 MV/m Peter Paul 03/17/05 • Acceleration in a DC field produces a steady beam. • Acceleration in an AC or radio frequency (rf) field produces beam bunches. PHY313-CEI544 Spring-05 15 Electrostatic fields and focusing • Just like light beams in a microscope particle beams must (and can) be focused along their way. • Electric fields widely used for beam focusing (picture tubes!). • It is weak focusing because one cannot achieve very high electric DC fields: ~ 1 MV/m Peter Paul 03/17/05 PHY313-CEI544 Spring-05 16 Modern electrostatic accelerators Beams of heavy ions are accelerated by a DC voltage from the top down to the base Peter Paul 03/17/05 PHY313-CEI544 Spring-05 The high-voltage terminal of this escalator is at 18 MV! The column is inside a tank that is filled with insulating gas at high pressure 17 Beam deflection in magnets • The Lorentz Force from a magnetic field B acts on charged particles with charge q and velocity v: FL qBv • This force deflects the beam but does not accelerate it. • The force acts perpendicular to the direction of flight. The bending power is directly proportional to the magnetic field strength B. • This can be used in particle accelerators to bend and/or focus beams • It is also used to deflect charged particles in detectors Peter Paul 03/17/05 PHY313-CEI544 Spring-05 18 Strong focusing with magnetic quadrupoles • A magnetic quadrupole lens focuses in one transverse direction but defocuses in the other. • However a sequence of two lenses with a drift space in between has a net focusing effect in two transverse dimensions. • Focal length of a single lens is given by fx - X-focusing mv - fy qBL fx - Y-focusing p - fy qBL • Since B can be large magnetic lenses can be very powerful. Peter Paul 03/17/05 PHY313-CEI544 Spring-05 19 Beam transports using strong focusing lenses • Magnetic Quadrupole fields are the work horse of all modern accelerators . • A single quadrupole focuses in one direction, defocuses in the orthogonal direction. Thus two lenses must always be paired • The strongest lenses can be made with superconductors. These can have very mall dimensions Peter Paul 03/17/05 • Below shows the beam transport system with several quadrupole pairs for the electron accelerator at Jefferson Laboratory PHY313-CEI544 Spring-05 20 Bunch Compression and Phase Stability see lecture 6 • In an r.f. accelerator beam need to be bunched in time and then the bunches must be kept together as they travel through the accelerator E/E E/E z E/E z E/E z E/E z z RF dispersive section Peter Paul 03/17/05 PHY313-CEI544 Spring-05 21 Linear accelerators (LINACs) • Linacs are accelerators for high currents and for electrons at very high energies (synchrotron radiation!). • They use either traveling or standing EM waves with multiple acceleration gaps in resonators. • As a beam bunch travels from one gap in the resonator to the next it must stay “in phase” with the r.f. wave. • Accelerating field levels achieved can be as high as 70 MV/m! • For a 1000 GeV accelerator at 30 MV/m this means a length of ~100 km or 62 miles. In practice it requires about twice that much! Peter Paul 03/17/05 • Resonance condition for Linac structure beam v • Length of each drift tube L = vT t 2p f T p ; 1 T ; 2f L v/2f • Thus as v increases L must increase • For ultra-relativistic beams with v ~ c (like electrons) L can remain constant. PHY313-CEI544 Spring-05 22 Electromagnetic Resonators see lectures 3-4 on linac This is a traveling wave resonator structure. The EM wave travels with the beam particles and the beam particles are riding the wave. This is a standing wave structure. The beam enters each resonator section as the r.f. wave in that section has a high field and the correct polarity Peter Paul 03/17/05 PHY313-CEI544 Spring-05 23 Superconducting Resonators • Superconducting resonators made from Nb have achieved the highest quality and highest electric field. • Quality = stored energy/dissipated energy • The stored energy is proportional to the square of the accelerating field • A high-quality resonator achieves a high electric field with very little power loss. • Q-factors of 1011 have been achieved up to accelerating fields of 30 MV/m ! • This requires extreme cleanliness and very smooth surfaces Peter Paul 03/17/05 PHY313-CEI544 Spring-05 24 Stanford Linear Accelerator • Stanford University pioneered the large electron LINAC since 1960. This is the 30 GeV SLAC facility which is ~ 2 miles long. • For the electrons travelling through the resonators the acclertor is Lorentz contracted and only ~ 20 cm long! Peter Paul 03/17/05 PHY313-CEI544 Spring-05 25 The Energy Frontier is provided by Colliders Peter Paul 03/17/05 PHY313-CEI544 Spring-05 LEP at CERN, CH Ecm = 180 GeV PRF = 30 MW 26 Synchrotrons • Synchrotrons are essentially linacs curled • Synchtroron beams use the same in a circle using powerful magnets to accelerating resonator over and bend the beam. over again: Very cost efficient • On its circular path the beam bunches travels through a few resonators millions • Below shown the reosnators of the RHIC rings. of time. They must satisfy a resonance condition: • The beam bunch must always get to the resonators when the r.f. field has the right amplitude and polarity • This condition requires that the r.f. frequency f and magnetic field B must both be changed as the beam energy increases. B must be “ramped up” until the beam reaches its final energy. Peter Paul 03/17/05 PHY313-CEI544 Spring-05 27 RHIC produces ultra-relativistic heavy ions 12:00 o’clock PHOBOS 10:00 o’clock RHIC PHENIX 8:00 o’clock STAR 6:00 o’clock U-line High Int. Proton Source BAF (NASA) LINAC BRAHMS 2:00 o’clock Design Parameters: Beam Energy = 100 GeV/u No. Bunches = 57 No. Ions /Bunch = 1 109 Tstore = 10 hours Lave = 2 1026 cm-2 sec-1 BOOSTER Pol. Proton Source AGS HEP/NP 1 MeV/u Q = +32 Peter Paul 03/17/05 Four detectors 4:00 o’clock 9 GeV/u Q = +79 m g-2 Six collision regions TANDEMS PHY313-CEI544 Spring-05 28 RHIC Pictures (1) Two rings of superconducting magnets bend a clockwise and a counter clockwise circling beam on circular paths. The magnets are cooled to 2 degrees K above absolute zero At this point the Gold beams send over from the AGS are divided into clockwise and a counterclockwise beams that are then accelerated and stored Peter Paul 03/17/05 PHY313-CEI544 Spring-05 29 RHIC Pictures (2) Rf storage cavities serve maintain the energy of the circulating beam and to keep the beam particles well bunched. Bunches in one ring will then intersect with bunches from the other ring. Installation of final focussing Triplets. These are superconducting quadrupole lenses that focus the two beam to a very small size at the intersection points Peter Paul 03/17/05 PHY313-CEI544 Spring-05 30 Artful bunch manipulation for maximal intensity Time during AGS cycle – 4 6 bunches injected from Booster – Debunch / rebunch into 4 bunches at AGS injection – Final longitudinal emittance: 0.3 eVs/nuc./bunch – Achieved 4 109 Au ions in 4 bunches at AGS extraction AGS circumference Peter Paul 03/17/05 PHY313-CEI544 Spring-05 31 RHIC extremely well understood: beam measurements and theory Measured beam width (red circles) agrees well with prediction (line). Successfully used to diagnose problems in the accelerator system . Peter Paul 03/17/05 PHY313-CEI544 Spring-05 32 Bringing beams into collision Beam in blue ring Beam in yellow ring 200 ns (60 m) Beams in collision at the interaction regions 200 ns (60 m) Peter Paul 03/17/05 PHY313-CEI544 Spring-05 33 Coll. rate / Blue Ions / Yellow Ions [Hz/1018] Summer 2000 first run shows stored beam The beams circle around for many hours but slowly lose intensity due to scattering among beam particles Expected: 1.1 for PHENIX and BRAHMS 0.4 for STAR and PHOBOS Peter Paul 03/17/05 PHY313-CEI544 Spring-05 34 The LHC at CERN under Construction • The LHC is the largest accelerator construction project in the world today. • https://www.CERN.org LHC is a proton collider (2 beams in one magnet) deep under the suburbs of Geneva (Switzerland) Peter Paul 03/17/05 PHY313-CEI544 Spring-05 35 Detectors surround the collision point at RHIC – 2 central spectrometers West Collision point – 2 forward spectrometers South East North – 3 global detectors Peter Paul 03/17/05 PHY313-CEI544 Spring-05 36 Detection of charged particles • Charged particle ionize gases. The degree of ionization depends on the charge of the particle and its velocity. • The particle ionizes most heavily at the end of its path. • The ionization products than be deflected by an electric or magnetic field toward a recording device. • Such detectors are wire Bragg Curve of an Iron beam shows the chambers or time projection degree of ionization as the particle chambers (TPC) penetrates into a plastic material Peter Paul 03/17/05 PHY313-CEI544 Spring-05 37 The STAR TPC Detector This detector consists of a huge solenoid magnet and all particles produced in the nuclear reaction move in and are bend by the magnetic field. This detector can record thousands of particle tracks simultaneously The ionization products produced by charged particles drift to the end of the magnetic field. From the drift time the path of the ionizing partcle can be reconstructed Peter Paul 03/17/05 PHY313-CEI544 Spring-05 38 Big Time Projection Chamber STAR First Events June 12 - 15 2000 first Au-Au collisions at STAR June 12 Brookhaven Science Associates U.S. Department of Energy Peter Paul 03/17/05 44 PHY313-CEI544 Spring-05 39 The PHENIX Detector Drift Chambers PHENIX has a pole magnet to bend charged particles and detects them in drift chambers, where ionization products drift to many thousands of wires. Peter Paul 03/17/05 Drift chamber + Pad chamber 1 PHY313-CEI544 Spring-05 40 PHENIX Detector Configuration • Two central arms – Mechanically ~complete – Roughly half of aperture instrumented • Global detectors – Zero-degree Calorimeters (ZDCs) – Beam-Beam Counters (BBCs) – Multiplicity and Vertex Detector (MVD, engineering run) www.phenix.bnl.gov Peter Paul 03/17/05 PHY313-CEI544 Spring-05 41 Hadron Identification in PHENIX Combined – Tracking – Beam-Beam Counter – Time-of-Flight array These detector can separate particle species, both negative and positive, very cleanly by use of the time of flight (TOF) provides excellent hadron identification over broad momentum band: Peter Paul 03/17/05 PHY313-CEI544 Spring-05 42 The ATLAS Detector for the LHC http://pdg.lbl.gov/atlas/ • The LHC will have three large detectors: CMS, ATLAS and ALICE. • Because the energies will be so much larger than at RHIC these detectors will be larger than the RHIC detectors, but they follow the same principles. Peter Paul 03/17/05 PHY313-CEI544 Spring-05 43 The central part of the ATLAS detector Peter Paul 03/17/05 PHY313-CEI544 Spring-05 44 Detention of Gamma rays • Gamma rays can be detected with very high efficiency and resolution by use of semiconductor detectors, such as Germanium crystals. Peter Paul 03/17/05 PHY313-CEI544 Spring-05 45 Eighth Homework Set, due April 7, 2005 1. Describe briefly how one attempts to “free up” (deconfine) individual quarks and what temperatures are required to achieve that goal. 2. How long after the initial Big Bang did the quarks freeze into nucleons and mesons? 3. What force is used to accelerate charged particles? Can we build accelerators for negatively charged particles (electrons) and for positively charge particles (protons)? 4. What are the properties of a “Synchrotron” that are the basis for its name? 5. How can we use magnetic fields to focus charged particles in space? 6. What property of charged particles is used to detected them and measure their charge and velocity? Peter Paul 03/17/05 PHY313-CEI544 Spring-05 46