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PHY313 - CEI544 The Mystery of Matter From Quarks to the Cosmos Spring 2005 Peter Paul/Norbert Pietralla Office Physics D-143 www.physics.sunysb.edu PHY313 Peter Paul 03/10/05 PHY313-CEI544 Spring-05 1 Information about the Trip to BNL • When and where: Thursday March 31, 2005 at 5:20 pm pickup by bus (free) in the Physics Parking lot. We will drive to BNL and arrive around 6pm (20 miles). We will visit The Relativistic Heavy Ion Collider (RHIC) and its two large experiments, Phenix and Star. Experts will be on hand to explain research and equipment. We will return by about 7:30 pm to arrive back at Stony Brook by 8pm. • What are the formalities? You need to sign up either in class or to my e-mail address [email protected]. by this Friday night. You must bring along a valid picture ID. That’s all! The guard will go through the bus and check the picture ID’s. • What about private cars: You will still have to sign up and must bring a picture ID (your drivers license) to the event. You will park your car at the lab gate, join the bus for the tour on-site and then be driven back to your car. • There is NO radiation hazard on site. I hope many or even most will sign up for a unique opportunity. Peter Paul 03/10/05 PHY313-CEI544 Spring-05 2 What have we learned last time I • The elements up to the tightest bound one, 56Fe, are formed during the burning process in the star as it uses its primordial fuel, 75% hydrogen (protons) and 25% Helium. • In the first step the star burns four protons into 4He. Once sufficed 4He is produced, 3 4He will combine to yield 12C. This process produces more heat. • In the next step the star uses 12C and the available hydrogen to go through the CNO cycle which produces the elements between 12C and 16O. This heats the star up further. • One there is sufficient 16O around the star will produce still heavier elements by using available H and 4He to fuse with the 16O. Peter Paul 03/10/05 • This process continues until the elements that are produced reach the peak of the nuclear binding energy, at Fe/Ni. • Then the star cools (Red Giant). Gravitation takes over compressing the star. The heaviest elements accumulate at the core in layers of density. Compression reheats the star & it explodes as a Supernova. • Nuclear reactions occurring during this violent phase produce many neutrons. These are rapidly captured into the Fe/Ni core to produce the heavier nuclei (rprocess). Beta decay changing n p inside the nuclei “moves” the neutronrich nuclei toward the valley of stability. • The final explosive phase spews these heavy elements into the interstellar medium. They are then incorporated into new stellar objects PHY313-CEI544 Spring-05 3 What have we learned last time II • The known “zoo” of strongly interacting particles (hadrons) was found naturally divided into very heavy particles (Baryons) and medium heavy particles (mesons). • It became clear from the formation and decay of these particles that several hidden quantum numbers play a role, in addition to the conservation of electric charge. • Strangeness S and Baryon number B are always conserved in reactions that involve the strong interaction. • A concept of elemental building blocks, called up, down and strange quarks, could explain all aspects of the construction of the hadrons. Peter Paul 03/10/05 • The quarks have electric changes in units of 1/3 of the electron charge, Baryon number 1/3. and spin-1/2 . • All known Baryons could be constructed combining 3 quarks; all mesons could be constructed with one quark and an anti-quark. • The discovery of the particle, a combination of 3 s quarks, showed that there was reality behind the quark concept. • Deep inelastic electron scattering from the proton showed that there were hard objects inside the proton. These are called partons, but are in fact quarks. • Later, three heavier quarks, the charm, top and bottom quarks were discovered. • The total of 6 quarks and 6 antiquarks group into three “families”. PHY313-CEI544 Spring-05 4 The three quark families • Today we know 3 families of quarks, and 3 antiquark families. Spin Charge First family Second family Third family 1/2 +3/2 up (3 MeV) charm (1300 MeV) top (175,000 MeV) 1/2 -1/2 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. http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html Peter Paul 03/10/05 PHY313-CEI544 Spring-05 5 The dynamics of quarks • In addition to their regular quantum numbers quarks must have other property that differentiates them from each other. This property is called Color. (See e.g. the proton = uud • There are 3 colors : Red, Green and Blue (these are just stand-in names). Thus the proton looks like this = uud or any other color combination) • The colored Quarks interact with each other through the exchange of gluons. These gluons exchange color between the quarks (Color interaction). • There are 9 color combinations but only 8 gluons. Peter Paul 03/10/05 greenanti-green greenanti-red greenanti-blue redanti-red redanti-blue redanti-green blueanti-blue blueanti-red blueanti-green PHY313-CEI544 Spring-05 6 Quark Confinement • The color interaction between quarks binds the quarks such that no single quark can ever be free. • This is different from two charged bodies bound by the Coulomb force, but similar to the binding of a magnetic north-pole and a south-pole • Thus any quark that emerges forma proton will “dress itself with other quarks or anti-quarks and emerge as a jet. • The binding force between quarks relatively weak when they are close together but grows stronger as they are pulled apart. • At close distances they can almost be treated as free: Asymptotic freedom Peter Paul 03/10/05 PHY313-CEI544 Spring-05 7 Hidden color, hidden charm • The J/ particle is made up of a c quark •All quarks carry one of 3 colors so and an antiquark. This combination that the Pauli principle is satisfied. cancels out the “charmed” character of However, any real elementary this particle. The charm is hidden inside. particle, like p and n, cannot have any color, or lese we would have seen it in • Trying to break up the bond between the c and cbar does not free them, but as earlier experiments. The color is the bond breaks the released energy hidden inside. The total object must produces non-charmed quarks. Thus the be “white” i.e. colorless. c and cbar quarks in the final products •This requirement puts a restriction also on the gluons and is responsible for the fact that there are only 8 gluons, the 9th would be colorless and could not effect any color transformation. Peter Paul 03/10/05 no longer cancel each other and the charm character is now apparent PHY313-CEI544 Spring-05 8 Neutrinos: the last Frontier • Neutrinos are today the least understood particles: They carry no electric charge and they only feel the weak interaction. • The weak force is much weaker than the EM force • EM e2 1 • Weak c 137 g2 0.6 10 6 c • Thus the weak force is about weaker by a factor of 10,000 Peter Paul 03/10/05 • Neutrinos have spin ½, similar to electrons and muons. • Neutrinos are part of the Lepton (light particle) Family • There are 3 neutrino species: – e, μ , Species Symbol Mass electrons e+, e- 511 keV muons μ +, μ - 105.7 MeV tau +, - 1,500 MeV neutrinos e, μ Very small PHY313-CEI544 Spring-05 9 Types of weak decays • • • • • • • n p+ + e- + vebar + 0 + e+ + + μ + e+ + μ+ e+ + - - n + e + K+ 0 + e+ Peter Paul 03/10/05 • The rules of the game are clear: 1. Charge is conserved in the decay. 2. Baryon number is conserved. 3. Strangeness is conserved. 4. Lepton number is conserved for each lepton family. • The latter means that on each side. of the decay we must have the same number of leptons. Anti-leptons cancel out leptons. • The positron is the anti-particle to the electron. The μ+ is the antiparticle to the μ-. PHY313-CEI544 Spring-05 10 History of the neutrino • • • • 1930 1956 1965 1966 • 1967 • 1970 • 1976 • 2000 • 2000 • 2004 W. Pauli stipulates existence the neutrino F. Reines detects the first neutrinos from a nuclear reactor Schwartz discovers the muon neutrino It is proven by Goldhaber and Sunyar that muon and electron neutrinos are different Ray Davis starts to look for neutrinos from the sun Solar neutrinos show a large deficiency, only about 25 to 45% of expected neutrino flux is detected. The first direct observations of neutrinos from a supernova explosion The tau neutrino is detected It is shown that solar electron neutrinos change their “flavor” as they travel from sun to earth, thus explaining the flux discrepancy The Kamiokande experiment shows muon neutrinos also change flavor. Peter Paul 03/10/05 PHY313-CEI544 Spring-05 11 How do we measure the barely measurable • We need a huge mass of detection medium to give the neutrinos ample opportunity to interact. • The detectors need to be deep underground to shield against cosmic muons. The neutrinos will go through all the rock, even through the earth from the other side • The first experiment was a chemical experiment done by Ray Davis who was looking for solar neutrinos in tye Homestake mine in SD • The second experiment was done with a huge Cerenkov water detector in the Kamiokande mine in Japan Peter Paul 03/10/05 PHY313-CEI544 Spring-05 12 Nobel Prizes in 2000 The first detection of solar neutrinos by Ray Davis’s chlorine experiment, and the subsequent confirmation by Kamiokande using real-time directional information and the first detection of supernova neutrinos opened up a new exciting field of neutrino astronomy. For these great achievements Ray Davis and Masatoshi Koshiba shared a Nobel Prize with Riccardo Giaconni who is the founding father of x-ray astronomy. Ray Davis Peter Paul 03/10/05 Masatoshi Koshiba PHY313-CEI544 Spring-05 Riccardo Giocconi 13 Big Underground Detectors Ray Davis experiment detected the first solar neutrinos using Chlorine Cl at Homestake Peter Paul 03/10/05 Kamiokande detected the first neutrinos from a supernova using water (3,000 tons). PHY313-CEI544 Spring-05 14 neutrinos HowDetecting do we detect neutrinos? Ray Davis Homestake Experiment: 615 tons Counts the number of 37Ar using a chemical methods Peter Paul 03/10/05 Kamiokande,Super-Kamiokande: 3,000 tons , 50,000 tons - Detect the recoil electron which is kicked by a solar neutrino out of a water molecule. - Can measure the energy and direction of the recoil electron. PHY313-CEI544 Spring-05 15 Physicists having fun in a boat in Super-Kamiokande Peter Paul 03/10/05 PHY313-CEI544 Spring-05 16 Physicist checking installed photomultipliers Peter Paul 03/10/05 PHY313-CEI544 Spring-05 17 Atmospheric Neutrinos How does a water Cherenkov detector work? Water Cherenkov Detector: Kamiokande,IMB,Super-Kamiokande,SNO Water is cheap and easy to handle! When the speed of a charged particle exceeds that of light IN WATER, electric shock waves in form of light are generated similar to sonic boom sound by super-sonic jet plane . These light waves form a cone and are detected as a ring by a plane equipped by photosensors. Peter Paul 03/10/05 PHY313-CEI544 Spring-05 18 An event produced by an atmospheric muon neutrino Peter Paul 03/10/05 PHY313-CEI544 Spring-05 19 Differentiating atmospheric muon and electron neutrinos Simulated events muon-like ring Major interactions: e + n -> p + em + n -> p + m Peter Paul 03/10/05 Most of time PHY313-CEI544 Spring-05 invisible electron-like ring 20 Neutrinos from a Supernova Peter Paul 03/10/05 PHY313-CEI544 Spring-05 21 A Supernova evolves into a black hole Will we be able to see ’s from a black hole? Peter Paul 03/10/05 PHY313-CEI544 Spring-05 22 Neutrinos from this SN were observed by Kamiokande and IMB 12 events 8 events SN 1987A, Feb.23, 1987 in Large Magellanic Cloud At about 170,000 light years away Before After Peter Paul 03/10/05 PHY313-CEI544 Spring-05 23 Supernova How do we know detected neutrinos are from a supernova? Birth of a supernova witnessed with neutrinos Number of photomultipliers fired A few hours before optical observation Kamiokande Background level Peter Paul 03/10/05 Taken by Hubble Space Telescope ( 1990) PHY313-CEI544 Spring-05 24 Can we How see does thethe neutrinos from the sun? Sun shine? • The sun produces very energetic neutrinos (> 1 MeV) in the processes that go from 4He to 8B Peter Paul 03/10/05 PHY313-CEI544 Spring-05 Kamiokande 25 Seeing the sun 4000 ft underground Image of Sun by Super-Kamiokande Peter Paul 03/10/05 PHY313-CEI544 Spring-05 26 Solar Neutrinos Seeing the Earth’s Orbit Underground! Distance Earth-Sun Summer: 4 Jul. 156 million km Winter : 3 Jan. 146 million km Solar neutrino flux ~ (1/distance)2 Peter Paul 03/10/05 Note: Flux less than half of expected (deficit)!!! 27 PHY313-CEI544 Spring-05 The solar neutrino problem in 1994 Ray Davis Observation over many years shows that only about 25% of the expected number is observed! Peter Paul 03/10/05 PHY313-CEI544 Spring-05 2002 Nobel Prize 28 Discovery of Muon Neutrinos • http://hyperphysics.pastr.gsu.edu/hbase/particles /neutrino2.html Beginning in 1965 Schwartz et al. at BNL bombarded a Be target with 15 GeV protons from the AGS. They produced copious which decayed into μ and neutrinos. The μ was different from the e m m Peter Paul 03/10/05 PHY313-CEI544 Spring-05 29 Discovery of the -lepton in 1975 • The data were taken at the e+-ecolliding beam target. The reaction would be e+ + e- + + • Note that this reaction satisfies all lepton conservation laws since e+ and + are both antiparticles. • The search was for events where only one electron and one muon would be detected • The has a mass 3000 x that of the electron! Peter Paul 03/10/05 Martin Perl receiving the Nobel Prize PHY313-CEI544 Spring-05 30 Discovery of the -neutrino • In 2000 the -neutrino was finally discovered at Fermilab. A proton beam produced a intense shower of neutrinos that should contain -neutrino. • The dector is layers of iron separated by layers of plastic scintillator • One in a million-million (10 -12) neutrinos would intercat in the iron plates and produce a -lepton which decayed leaving characteristic tracks. Four such tracks were isolated. Peter Paul 03/10/05 This completes the lepton family below 1 TeV PHY313-CEI544 Spring-05 31 The weak interaction: W and Z bosons • The force carriers of the weak interaction are the W+- (for “weak”) and the Z bosons. • The carriers of the weak force are very heavy. That is the reason for the very short range of the force. The mass of the W is 80.4 GeV; the mass of the Z0 is 91.2 MeV. • The W+ is the antiparticle to the W-; the Z0 is its own antiparticle • Note on the right how the W is able to change the quarks from one flavor to another. • Example: The beta decay of 60Co 60 Co28 Ni e e 60 27 • Inside the Co nucleus one of its 33 neutrons changes into a proton: n p e e • Looking inside the neutron, at the quark level the reaction is the change of a d-quark into a u-quark: d u W W e e Peter Paul 03/10/05 PHY313-CEI544 Spring-05 32 Neutron beta decay at the quark level Fundamental Force An example of weak interaction - Free neutron decay: n -> p + e- e Peter Paul 03/10/05 PHY313-CEI544 Spring-05 33 How many neutrino families are there? ee Z 0 f f At the e+-e- collider at SLAC the Z boson was produced in the reaction below where ffbar are any ½ spin particles. The mass energy was determined with high precision. The width relates to the number of neutrino families that are emitted in the decay. More families shorten the life time and increase the width. There is excellent agreement with 3 families. (MZ=91.1882±0.0022 GeV) Peter Paul 03/10/05 PHY313-CEI544 Spring-05 34 The BuildingWhat Blocks of the Standard Model is matter made of? • With the assurance that we have seen all 3 families of leptons, and having 3 families of quarks, a unified picture emerges: 1. There are the 6 basic weakly interacting particles (leptons). They all have spin 1/2 hbar. 2. There are 6 building blocks for strongly interacting particles (hadrons). 3. There are 4 basic force carriers (Bosons). They all have spin 1 hbar. There are 8 gluons, 2 W’s one Z and one 4. This scheme unifies the EM and the weak interaction: The Z and the have the same heritage but split into a heavy and a light twin. Peter Paul 03/10/05 PHY313-CEI544 Spring-05 35 Unification of Forces Grand Unified Theories (GUTs) Strong Electric Electromagnetic Magnetic GUTs 19th c. Electroweak Weak 20th c. 21st c.? GUTs predict: hard Proton must decay Neutrino must have mass Gravitational Peter Paul 03/10/05 PHY313-CEI544 Spring-05 36 Seventh Homework Set, due March 17, 2005 1. Quarks have spin ½, like electrons, and thus must obey the Pauli principle. What property of quarks makes it possible to put two u quarks into a proton? 2. Gluons are the force carriers of the strong interaction. How many of them are there, how do they differ from each other, and what is their mass? 3. What are the names and properties of the three heavy quarks that have been detected experimentally. 4. How can we detect the elusive neutrinos: Give two characteristics of a successful detector. 5. What neutrinos can we expect to see from the sun? Why is the prediction of the neutrino flux that we expect so solid? 6. How many different neutrinos are there and what are the force carriers of the weak interaction? Peter Paul 03/10/05 PHY313-CEI544 Spring-05 37 Do neutrinos have mass? Peter Paul 03/10/05 PHY313-CEI544 Spring-05 38 Long baseline neutrino oscillation Peter Paul 03/10/05 PHY313-CEI544 Spring-05 39 The SNO experiment Peter Paul 03/10/05 PHY313-CEI544 Spring-05 40 Particle Physics What is neutrino oscillation? Neutrino Oscillation There are three kinds of neutrinos: e m (flavours) If neutrinos have mass, they can change their identities (flavours) e m oscillation Peter Paul 03/10/05 PHY313-CEI544 Spring-05 41 Atmospheric Neutrinos Super-Kamiokande: The successor of highly successful Kamiokande 40 m height 50,000 tons of pure water equipped with 12,000 50 cm photomultipliers and 2,800 20 cm photomultipliers (PMTs). 1,000 m deep Peter Paul 03/10/05 PHY313-CEI544 Spring-05 40 m diameter 42 Atmospheric Neutrinos Source of atmospheric neutrinos Earth’s atmosphere is constantly bombarded by cosmic rays. Energetic cosmic rays (mostly protons) interact with atoms in the air. These interactions produce many particles-air showers. Neutrinos are produced in decays of pions and muons. Peter Paul 03/10/05 PHY313-CEI544 Spring-05 43 Atmospheric Neutrinos Evidence of neutrino oscillation/mass with oscillation without oscillation Peter Paul 03/10/05 low energy e low energy m high energy e high energy m First crack PHY313-CEI544 Spring-05 in the Standard Model!!! 44 Solar Neutrinos How do we see neutrino oscillation with solar neutrinos? Flux: measured/expected Homestake : 0.27 Neutrino deficit!!! Kamiokande : 0.44 Not enough neutrinos Super-Kamiokande : 0.47 Should be 1 Neutrino oscillations m is not visible to all Peter Paul 03/10/05 experiments above PHY313-CEI544 Spring-05 45 Solar Neutrinos How can we prove it’s neutrino oscillation? Neutral current SNO D2O instead Peter experiment Paul 03/10/05 uses heavy water PHY313-CEI544 Spring-05of normal water H2O 46 Solar Neutrinos How does the neutral current confirm neutrino oscillation? Elastic scattering -This reaction is available only for e . Neutral current interaction -This reaction is flavour blind and is available for all kinds of neutrinos. -Available for both water and heavy - Available water. Peter Paul 03/10/05 PHY313-CEI544 Spring-05 only for heavy water. 47 Solar Neutrinos Confirmation of solar neutrino oscillation by SNO m is visible only to SNO But NOT to Homestake, Kamiokande or SuperKamiokande. Even if solar neutrino e changes its flavour to m or total flux of solar neutrino can be measured by SNO Solar flux measured: 6.4+-1.6 x 106 cm-2 s-1 Good agreement! Solar flux predicted : 5.1+-1.0 x 106 cm-2 s-1 Solar neutrinos oscillate!!!! PHY313-CEI544 Spring-05 Peter Paul 03/10/05 48 Supernova Why is detection of supernova neutrinos important? We learn: - Properties of neutrinos: its mass (or limit of it), magnetic moment,electric charge, etc. - Details of supernova explosion: how a star dies - How a neutron star or a black hole is formed if it happens Peter Paul 03/10/05 PHY313-CEI544 Spring-05 49