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MOM 7

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Published on October 15, 2007

Author: Kestrel

Source: authorstream.com

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PHY313 - CEI544 The Mystery of Matter From Quarks to the Cosmos Spring 2005:  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 Information about the Trip to BNL:  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 ppaul@bnl.gov. 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. What have we learned last time I:  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. 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). Gravita-tion 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 (r-process). Beta decay changing n  p inside the nuclei “moves” the neutron-rich 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 What have we learned last time II:  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. 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 com-bination 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”. The three quark families:  The three quark families http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html Today we know 3 families of quarks, and 3 antiquark families. Note that the neutron and proton and the light mesons are all build up of the lightest quarks, the u and d. The dynamics of quarks:  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. Quark Confinement :  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 Hidden color, hidden charm:  Hidden color, hidden charm The J/ particle is made up of a c quark and an antiquark. This combination cancels out the “charmed” character of this particle. The charm is hidden inside. Trying to break up the bond between the c and cbar does not free them, but as the bond breaks the released energy produces non-charmed quarks. Thus the c and cbar quarks in the final products no longer cancel each other and the charm character is now apparent All quarks carry one of 3 colors so that the Pauli principle is satisfied. However, any real elementary particle, like p and n, cannot have any color, or lese we would have seen it in earlier experiments. The color is hidden inside. The total object must be “white” i.e. colorless. 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. Neutrinos: the last Frontier:  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  Weak Thus the weak force is about weaker by a factor of 10,000 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 ,  Types of weak decays :  Types of weak decays n  p+ + e- + vebar +  0 + e+ +  +  μ + e+ +  μ+ e+ +  -   -  n + e +  K+  0 + e+ The rules of the game are clear: Charge is conserved in the decay. Baryon number is conserved. Strangeness is conserved. 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-. History of the neutrino:  History of the neutrino 1930 W. Pauli stipulates existence the neutrino 1956 F. Reines detects the first neutrinos from a nuclear reactor 1965 Schwartz discovers the muon neutrino 1966 It is proven by Goldhaber and Sunyar that muon and electron neutrinos are different 1967 Ray Davis starts to look for neutrinos from the sun 1970 Solar neutrinos show a large deficiency, only about 25 to 45% of expected neutrino flux is detected. 1976 The first direct observations of neutrinos from a supernova explosion 2000 The tau neutrino is detected 2000 It is shown that solar electron neutrinos change their “flavor” as they travel from sun to earth, thus explaining the flux discrepancy 2004 The Kamiokande experiment shows muon neutrinos also change flavor. How do we measure the barely measurable:  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 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 Masatoshi Koshiba Riccardo Giocconi Nobel Prizes in 2000 Big Underground Detectors:  Ray Davis experiment detected the first solar neutrinos using Chlorine Cl at Homestake Kamiokande detected the first neutrinos from a supernova using water (3,000 tons). Big Underground Detectors Detecting neutrinos:  How do we detect neutrinos? Ray Davis Homestake Experiment: 615 tons Counts the number of 37Ar using a chemical methods 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. Detecting neutrinos Physicists having fun in a boat in Super-Kamiokande:  Physicists having fun in a boat in Super-Kamiokande Physicist checking installed photomultipliers:  Physicist checking installed photomultipliers Slide18:  Atmospheric Neutrinos 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 photo- sensors. How does a water Cherenkov detector work? Slide19:  An event produced by an atmospheric muon neutrino Differentiating atmospheric muon and electron neutrinos:  electron-like ring muon-like ring nm + n -> p + m- ne + n -> p + e- Major interactions: Most of time invisible Simulated events Differentiating atmospheric muon and electron neutrinos Neutrinos from a Supernova:  Neutrinos from a Supernova A Supernova evolves into a black hole:  A Supernova evolves into a black hole Will we be able to see ’s from a black hole? Slide23:  Neutrinos from this SN were observed by Kamiokande and IMB SN 1987A, Feb.23, 1987 in Large Magellanic Cloud At about 170,000 light years away Before After 12 events 8 events Slide24:  Supernova Background level Birth of a supernova witnessed with neutrinos How do we know detected neutrinos are from a supernova? Kamiokande Number of photomultipliers fired A few hours before optical observation Taken by Hubble Space Telescope ( 1990) Can we see the neutrinos from the sun?:  How does the Sun shine? Kamiokande Can we see the neutrinos from the sun? The sun produces very energetic neutrinos (> 1 MeV) in the processes that go from 4He to 8B Seeing the sun 4000 ft underground :  Image of Sun by Super-Kamiokande Seeing the sun 4000 ft underground Slide27:  Solar Neutrinos Summer: 4 Jul. 156 million km Winter : 3 Jan. 146 million km Distance Earth-Sun Solar neutrino flux ~ (1/distance)2 Seeing the Earth’s Orbit Underground! Note: Flux less than half of expected (deficit)!!! The solar neutrino problem in 1994:  Ray Davis 2002 Nobel Prize The solar neutrino problem in 1994 Observation over many years shows that only about 25% of the expected number is observed! Discovery of Muon Neutrinos:  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 Discovery of the -lepton in 1975:  Discovery of the -lepton in 1975 The data were taken at the e+-e- colliding 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! Martin Perl receiving the Nobel Prize Discovery of the -neutrino:  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 characteris-tic tracks. Four such tracks were isolated. This completes the lepton family below 1 TeV The weak interaction: W and Z bosons:  The weak interaction: W and Z bosons The force carriers of the weak inter-action 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 Inside the Co nucleus one of its 33 neutrons changes into a proton: Looking inside the neutron, at the quark level the reaction is the change of a d-quark into a u-quark: Neutron beta decay at the quark level:  Fundamental Force An example of weak interaction Free neutron decay: n -> p + e- + ne - Neutron beta decay at the quark level How many neutrino families are there?:  How many neutrino families are there? (MZ=91.1882±0.0022 GeV) 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. The Building Blocks of the Standard Model:  What is matter made of? The Building Blocks of the Standard Model With the assurance that we have seen all 3 families of leptons, and having 3 families of quarks, a unified picture emerges: There are the 6 basic weakly interacting particles (leptons). They all have spin 1/2 hbar. There are 6 building blocks for strongly interacting particles (hadrons). There are 4 basic force carriers (Bosons). They all have spin 1 hbar. There are 8 gluons, 2 W’s one Z and one  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. Unification of Forces :  Grand Unified Theories (GUTs) Strong Electric Magnetic Electromagnetic Weak Electroweak Gravitational GUTs hard 19th c. 20th c. 21st c.? GUTs predict: Proton must decay Neutrino must have mass Unification of Forces Seventh Homework Set, due March 17, 2005:  Seventh Homework Set, due March 17, 2005 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? 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? What are the names and properties of the three heavy quarks that have been detected experimentally. How can we detect the elusive neutrinos: Give two characteristics of a successful detector. What neutrinos can we expect to see from the sun? Why is the prediction of the neutrino flux that we expect so solid? How many different neutrinos are there and what are the force carriers of the weak interaction? Do neutrinos have mass?:  Do neutrinos have mass? Long baseline neutrino oscillation:  Long baseline neutrino oscillation The SNO experiment:  The SNO experiment Slide41:  Particle Physics Neutrino Oscillation There are three kinds of neutrinos: ne nt nm If neutrinos have mass, they can change their identities (flavours) ne nm nt What is neutrino oscillation? (flavours) oscillation oscillation oscillation Slide42:  Atmospheric Neutrinos Super-Kamiokande: The successor of highly successful Kamiokande 50,000 tons of pure water equipped with 12,000 50 cm photomultipliers and 2,800 20 cm photomultipliers (PMTs). 40 m diameter 40 m height 1,000 m deep Slide43:  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. Slide44:  Atmospheric Neutrinos Evidence of neutrino oscillation/mass low energy ne high energy ne low energy nm high energy nm with oscillation without oscillation First crack in the Standard Model!!! No time to oscillate Enough time to oscillate Slide45:  Solar Neutrinos How do we see neutrino oscillation with solar neutrinos? Homestake : 0.27 Kamiokande : 0.44 Super-Kamiokande : 0.47 Flux: measured/expected Neutrino deficit!!! Not enough neutrinos nm is not visible to all experiments above Should be 1 Neutrino oscillations Slide46:  Solar Neutrinos How can we prove it’s neutrino oscillation? Neutral current SNO experiment uses heavy water D2O instead of normal water H2O Slide47:  Solar Neutrinos How does the neutral current confirm neutrino oscillation? Elastic scattering Neutral current interaction -This reaction is available only for n e . -This reaction is flavour blind and is available for all kinds of neutrinos. -Available for both water and heavy water. - Available only for heavy water. Slide48:  Solar Neutrinos Confirmation of solar neutrino oscillation by SNO nm is visible only to SNO But NOT to Homestake, Kamiokande or Super- Kamiokande. Even if solar neutrino ne changes its flavour to nm or nt total flux of solar neutrino can be measured by SNO Solar flux measured: 6.4+-1.6 x 106 cm-2 s-1 Solar flux predicted : 5.1+-1.0 x 106 cm-2 s-1 Solar neutrinos oscillate!!!! Good agreement! Slide49:  Supernova Why is detection of supernova neutrinos important? Properties of neutrinos: its mass (or limit of it), magnetic moment,electric charge, etc. - Details of supernova explosion: how a star dies We learn: - How a neutron star or a black hole is formed if it happens

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