Roe_Summer_Lecture------------------.ppt
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Roe_Summer_Lecture------------------.ppt
- 1. What’s the Matter With Antimatter? Dr. Natalie A. Roe Lawrence Berkeley National Laboratory
- 2. The Prediction of Antimatter • 1900 - 1920’s: Development of relativity, quantum mechanics • 1928: Paul Dirac’s relativisitic equation of motion for the electron • Predicted the positron, antimatter partner of the electron • Predicted that negative protons must also exist • Speculated that half the stars may be made of antimatter 1933 Nobel Prize in Physics
- 3. The Discovery of Antimatter • The positron was discovered in 1932 in cosmic rays by Carl Anderson QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 1936 Nobel Prize in Physics
- 4. What is a Fundamental Particle? • Greeks: Earth, Air, Fire, Water • 1897: Thomson discovers the electron • 1911: Rutherford discovers the nucleus • 1919: Rutherford discovers the proton • 1932: Chadwick discovers the neutron • 1800’s: Periodic table of the elements • 1967: Kendall, Friedman and Taylor discover quarks in electron-nucleon scattering experiments at SLAC. • Quarks • are fractionally charged • occur in pairs or in triplets, never singly • are point-like objects (to the limit of our ability to measure)
- 6. Quirks of quarks … • Two types of quarks are needed to make our world, “up” and “down” • proton = (uud) and neutron = (udd) • protons and neutrons form nuclei • add electrons to form neutral atoms • neutrinos are emitted in nuclear processes that power the sun • 4 fundamental particles are building blocks of our world +2/3 -1/3 0 -1 • 2 additional generations of particles have been discovered • Why 3 generations? • What determines their masses? • What determines their decays? • Do all particles have antimatter partners?
- 7. Discovery of the Anti-proton at Berkeley Lab in 1955 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Surrounding Edward Lofgren (center), head of the Bevatron, are discoverers of the antiproton, (left to right) E.Segre, C.Wiegand, O. Chamberlain and T.Ypsilantis. E.O. Lawrence, inventor of the cyclotron and founder of Berkeley Lab 1939 Nobel Prize in Physics 1959 Nobel Prize in Physics
- 8. The Mirror Universe • All fundamental particles have anti-matter partners • The neutrino ( n ) may be its own anti-particle • Quark and anti-quarks form bound states called mesons • p+ = ud K0 = ds • B0 = bd B0 = bd The “Standard Model” particles
- 9. Matter and Energy • Einstein first realized the equivalence of matter and energy • When matter and antimatter meet, they annihilate into energy • Energy can also materialize as particle- antiparticle pairs • This is what happened in the “Big Bang” g e- e+ e- e+ g g Feynman diagram QuickTime™ and a TIFF(Uncompressed) decompressor are needed to see this picture.
- 10. Antimatter Production in the Sun • Every second, thermonuclear reactions in the sun convert 600 million tons of hydrogen into 595 million tons of helium, and 5 million tons of mass is converted to energy • p + p => pn (deuterium) + e+ + n • pn + p => 3He + g • 3He + 3He => 4He + p + p • Solar flares accelerate particles, producing electron- positron pairs. • ~ 0.5 kg antimatter produced in large flare! • Image of flare by RHESSI satellite (PI Bob Lin of UC Berkeley/SSL) QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Gamma Ray emission from Solar flare on July 23, 2003 Blue = 0.3 - 0.5 MeV Purple = 0.7 - 1.4 MeV Red = 2.2 MeV
- 11. Where is all the Antimatter? • No antimatter within our galactic cluster • Can Universe be a quilt of matter & antimatter domains? • Gamma ray spectrum in space rules out antimatter domains smaller than ~1000 Mpc • No evidence yet for antimatter in primordial cosmic rays The AMS experiment will search for primordial antimatter from its orbit on the International Space Station QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
- 12. Results 1 - 10 of about 589,000 for antimatter [definition]. (0.10 seconds) Antimatter:Mirror of the Universe A thorough discussion covering all aspects of antimatter. livefromcern.web.cern.ch/livefromcern/antimatter/ - 13k - Cached - Similar pages . Sponsored Links . antimatter Low Prices & Huge Selection antimatter Ebay.com QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. You Like Quantum physics?Gain Extreme Wealth and Success By Manifesting Your Own Reality!I CreateReality.com Gravity BreakthroughBestseller explains gravity. Solves today's greatest science mysteries! TheFinalTheory.com If the Law of Attractionhasn't worked for you, I know why. Three things that must come first. www.ProvocativeCommunications.com QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
- 13. Dark Energy: ~70% Dark Matter: ~25% Energy budget of Universe Antimatter: 0% ~25% ~70%
- 14. Symmetries of Matter: C, P and T C = Charge conjugation: particle antiparticle P = Parity (mirror reflection): x -x C and P together change matter to antimatter; T = Time reversal: t -t The product CPT: always invariant!!! + e- - e+ CP Mirror g e- e+ g e- e+
- 15. 1957 Discovery of Parity Violation The Universe knows its right hand from its left! C.S. WU Co60 B field e- ne n -> p e- n Beta Decay of Co60
- 16. Another way to look at CP Violation Bob Cahn Left-handed particle => Right-handed anti-particle
- 17. An Unexpected Discovery In 1964 Cronin and Fitch discovered CP violation in the decay of the long-lived, CP-odd neutral K meson into a CP- even final state: Br(KL -> p+p- ) ~ 0.2% There is a difference between matter and antimatter! “We are hopeful… that at some epoch, perhaps distant, this cryptic message from nature will be deciphered.” J. Cronin 1980 NOBEL PRIZE J.Cronin V. Fitch
- 18. CP Violation => T Violation unless CPT is also violated! Antiproton Decelerator at CERN ATHENA experiment Anti-hydrogen annihilation near walls of trap Prototype for a next generation experiment to trap anti-hydrogen and characterize with laser spectorscopy. J. Fajans, J. Wurtele et al Discovery of CPT violation would be revolutionary! Alpha Test Trap and Superconducting Magnet Prototype built at LBNL
- 19. Sakharov’s Recipe for BAU (1967) (Baryon Asymmetry of the Universe) Necessary ingredients are: • Baryon number violation • Thermal non-equilibrium • C and CP violation • Do we understand the cause of CP violation in particle interactions? • Can we calculate the BAU from first principles? QuickTi me ™an d a TIFF( Uncomp res sed) deco mpre ssor ar e need ed to see this pictur e. 1975 Nobel Peace Prize (nB - nB )/ ng= 6.1 x 10-10 All of these ingredients were present in the early Universe!
- 20. An Astounding Connection • In 1973, M. Kobayashi and T. Maskawa predicted: CP violation third generation of quarks! • Subsequent discoveries confirmed the prediction: •b quark was discovered in 1977 at Fermilab by Lederman et al • t quark was discovered in 1994 at Fermilab by CDF and D0 • The three-generation Standard Model naturally includes CP violation in certain particle decays. u d c s t b quark doublets e ne n n lepton doublets Standard Model Particles
- 21. An Asymmetric B Factory to Study CP Violation • CP violation in K0 (= sd) meson decays was exhaustively studied for over three decades •the effects are very small, and hard to interpret theoretically • In B0 (= bd) meson decays, the Kobayishi- Maskawa theory predicts large CP violation effects •besides being large, the effects are theoretically clean • But - the decay rates are small => need to produce millions of B mesons in a B “factory” • To observe the CP asymmetry between B and anti-B mesons, a special type of e+e- collider is required with unequal beam energies - the Asymmetric B Factory
- 22. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 1999: Pier Oddone and Jonathan Dorfan in the PEP-II tunnel
- 23. PEP-II Stanford Linear Accelerator Center, Stanford, California Approved as a Presidential Initiative in 1993; completed in 1999. Reached full design luminosity in 2000. Japanese B Factory has also been built with similar design.
- 24. The BaBar Collaboration: ~600 physicists from 73 institutions and 9 countries The BaBar Detector
- 25. How the BaBar Detector Works
- 26. CP violation occurs in the interference between mixing and decay to a CP eigenstate, eg B0 -> p+ p - Measuring CP Violation with B0s Not equal – CP Violation! B0(t) fCP B0 B0 B0(t) fCP B0 B0
- 27. B0B0 Mixing • Matter-antimatter oscillations occur in neutral K0 and B0 mesons • Mixing adds CP violating couplings, with time dependence • Observation of the time dependence requires the use of asymmetric energy beams • this boosts the B mesons so they travel a measurable distance before decaying • measuring the B decay vertices establishes when the B decayed B0 B0 b b d d t t W- W- the mixing “box” diagram first - third generation coupling
- 28. The Asymmetric B Factory Concept decay of B “tag” B ->CP eigenstate e+ e-->U(4S) ->BB 9 GeV e- Dt Dz 3 GeV e+ QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
- 29. • B0 J/Y Ks is the best decay mode to measure the CP violating angle b , the phase due to the mixing diagram • B0 J/Y Ks also has a relatively large branching ratio (1 per million) and is “easy” to reconstruct Golden Mode for CP Violation in B decay b d c c s d W+ Ks J/Y
- 30. Recipe for Measuring CP Violation in B Meson Decays • Produce many B0 B0 pairs (hundreds of millions) • Reconstruct one B in a special decay called a CP eigenstate • “Tag” the other B0 to make the matter/antimatter distinction • Determine the time between the two B0 decays, Dt • Compare Dt distributions for B0 and B0 tagged events; the difference measures CP violation, the difference between matter and antimatter B tagged B tagged Dt (ps)
- 31. 270 Million BB pairs produced since 1999 and recorded by the BaBar detector Year
- 32. How to “tag” a B or anti-B meson: The DIRC Detector Angle of Cherenkov light is related to particle velocity – Transmitted by internal reflection – Detected by~10,000 PMTs c Particle Quartz bar Cherenkov light Active Detector Surface + - + + p p K D D D 0 0 * , B0 e+ D 0 K+ p - p - n B0 -> D* e n
- 33. How to measure the decay times: The Silicon Vertex Tracker (SVT) Uses five layers of silicon microstrip detectors to measure B decay vertices to better than 0.1 mm and determine the time between the two B meson decays.
- 34. Tracking Charged Particles in the SVT
- 35. Latest results from BaBar on difference of matter and antimatter: Sin2b = 0.22 0.0400.023
- 36. What does this result mean? sin2b=0.72±0.04 • Maximum asymmetry => sin2b = 1 • Zero asymmetry => sin2b = 0 • Much larger asymmetry than in K0 decays (72% vs 0.2%); combined experimental plus theoretical error is small • The result is consistent with the prediction of the three-generation Standard Model • But: our best calculations of early Universe do not produce enough excess matter - off by 10 orders of magnitude!
- 37. What is the Matter with Antimatter? • How can a parameter between 0 and 1 provide the missing 10 orders of magnitude? • It can’t • New particles can provide the required CP violation • The effects of new particles may be observable in B decays…
- 38. sin 2b in a different mode • sin2b measured in final states with charm agrees with the Standard Model predictions • sin2b can also be measured in other “penguin” decays and should agree within a few percent • New physics could enter in loops! , f b d c c s d W+ Ks J/Y tree diagram penguin diagram
- 39. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. World average for sin2b in “penguins” compared to J/Y Ks … hint of new physics, or a statistical fluctuation?
- 40. Future Prospects for BaBar… • The BaBar experiment has published ~ 150 papers so far in refereed journals on a wide variety of topics • Expect to collect ~4x more data over next 3-4 years => statistical errors will decrease by x2 • In a race with the Japanese B Factory • behind right now in total luminosity • advantage in the ability to confirm any unexpected results • The Large Hadron Collider at CERN will turn on in 2007, data taking by 2008 • could directly produce new particles
- 41. Summary • CP violation is required in any theory starting from the Big Bang to explain the dominance of matter over antimatter • Antimatter exists and can be created at accelerators; but there is very little antimatter naturally occurring in our Universe • CP symmetry between matter and antimatter is violated at the quark level, as measured by BaBar - but not enough ! • More detailed measurements may give clues to new physics beyond the Standard Model
- 42. • Antimatter engines on Starship Enterprise were powered by p + p annihilation! The Anti-Hydrogen Economy? • Distinguish between energy source and method to store and transport energy - Creating, storing antiprotons requires a lot of energy, and trapping them is also very inefficient All the antiprotons created in one year at Fermilab would only power a 100 watt bulb for 30 minutes, even with 100% trapping and conversion efficiency! • Cost: $62.5 trillion per gram! Penning Trap QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see t his picture. Penn State Univ Penning Trap QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
- 43. What’s the Matter with Antimatter? • Our present view of matter - the “Standard Model” of particle physics • The amazing prediction and discovery of antimatter • Is antimatter useful, Dr. Spock? • Colliding matter and antimatter • What happened to all the antimatter ? - the search for CP Violation • Why does it matter?
- 44. Latest result: Sin2b = 0. 0.10
Editor's Notes
- Thank you for the introduction. This evening my topic is “What’s the Matter with Antimatter”, and my title slide is an artist’s impression of matter meeting antimatter, and as they shake hands they annihilate. Obviously antimatter is not something that we are used to dealing with in our every day life, for if it were we would surely find a safer way to greet strangers than shaking hands and risking annihilation! This evening I will introduce you to the world of antimatter and try to explain that it is not so different, after all, and that the real puzzle is why there is any matter in the Universe at all.
- Hubble used 100m telescope on Mt Wilson to observe first galaxies outside of our own and realized they are almost all moving away from us with velocity proportional to their distance - Hubble’s law, implying that the universe is not static and famously causing Einstein to regret the insertion of the cosmological constant into the equations of general relativity to offset gravity and make the universe static. How surprised would he be if he knew that the cosmological constant has made a come back as one theory for dark energy. Physics: in addition to relativity the revolution of QM Dirac tried to unify new fields of relativity and QM by writing down relativistic equation of motion for the e-, found 2 solutions and realized the 2nd solution was not a negative energy e- but an anti-electron or positron with positive energy. Prediction of antimatter soon confirmed by in cosmic ray experiments by Anderson at Caltech, and both Dirac and Anderson received nobel prizes. Concept of antimatter combined with Einstein’s equation relating matter and energy meant that matter could be created out of energy in particle antiparticle pairs and in his Nobel lecture Dirac speculated that there must be antimatter worlds out there in the universe Precision data has since shown us a wide variety of new particles and their anti-matter counterparts, and Alan Guth’s theory of inflation explailned how the universe starting in a Big Bang could have become so flat and so uniform However the symthesis of all these theories and this precision data is still lacking and there are many open questions. We are still waiting for the 21st century Newton
- Antimatter started as a figment of Dirac’s imagination, but amazingly enough he was correct and the experimental evidence for antimatter was found just 4 years after he wrote down his famous equation. Cosmic rays are particles that enter our atmosphere from outer space, often very energetic particles that may have originated far away in some cataclysmic event. For example if an energetic proton enters our atmosphere and collides with a molecule of air, it will produce what we call a shower of particles, growing in number as they diminish in energy. Particle antiparticle pairs are created in these showers. By observing cosmic rays with a bubble chamber, Carl Anderson found evidence for positively charged particles
- Definition of fundamental - like lego blocks Greeks - Democritus had a competing theory, that everything was made of atoms - Greek for uncuttable. But Socrates favored the theory of 4 elements as being more elegant, and the atomic theory languished for thousands of years. In the 1800’s the concept of the atom came back as chemistry advanced and many elements were identified and organized into the Periodic Table according to atomic weight, ~ 100 elements A series of discoveries beginning in 1897 with JJ Thomson’s measurement of the electron’s charge/mass ratio led to our modern view of the atom - a nucleus consisting of protons and neutrons, surrounded by a cloud of much lighter electrons. Only 3 fundamental particles needed - very elegant. But this tidy picture was changed forever in 1967...
- uud = proton, udd = neutron - explain charge Greek letter nu stands for Neutrinos - fascinating particles, almost massless, neutral and able to pass through the earth without interacting. All the complexity of the periodic table, over 100 elements, can be explained in terms of 3 fundamental particles. A theory with an elegance Socrates would appreciate. The additional generations are heavier and short-lived, decaying down into the first generation in fractions of a second. Particle physicists have discovered 4 additional quarks, called the charm, strange, top and bottom quarks. In addition we have discovered cousins of the electron that are very similar except for the fact that they are much heavier and unstable. Greek letters mu for muon and tau.
- Lawrence and McMillan set Bevatron energy at 6 GeV in order to have sufficient energy to produce p p-bar pairs. Anti-protons were produced by colliding protons into a target, then selecting negatively charged particles with the momentum expected for anti-protons. Velocity was determined using both time of flight and Cerenkov counters. p = mv, so determining both p and v allowed determination of m which should be equal to the proton mass.
- Antimatter sounds lke something only in Star Trek but it is science fact and a very normal part of the SM of particle physics explain baryons and anti-baryons
- total energy of universe can stil be zero because energy in the mass of the particle antiparticle pairs is offset by the negative energy in the gravitational field So universe could be a quantum fluctuation, created literally out of nothing.
- nuclear annihilation produces photons redshifted into gamma rays today observed gamma ray spectrum rules out domains smaller than 1000 Mpc Cohen, duRujula, Glashow 1998
- C alone is not enough because of a property called spin that particles have; parity reverses the spin, just like changing a right-handed screw to a left-handed screw. Anti-particles not only have opposite charge but they also have opposite spin.
- The experiment performed by Wu in 1957 involved C060 atoms that were polarized in a magnetic field . Wu measured the direction of the electrons that were emitted when Co60 underwent beta decay, a weak interaction in which a neutron decays to a proton, emitting an electron and an anti-neutrino which goes undetected. Wu found electrons were emitted only in the direction opposite to that of the applied magnetic field, and never in the opposite direction.This total violation of parity symmetry was profoundly shocking because it was the first evidence that Instead of being perfectly symmetric a the subatomic level, Nature knew its left hand from its right hand.
- This tiny asymmetry means that if we were to communicate with intelligent life in a distant part of the galaxy, we could ask their particle physicists to tell us the results of their experiments with K mesons and determine whether they lived in a matter world or an antimatter world!
- It wasn’t enough just to observe CP violation as a tiny effect in K meson decays - we want to understand where it comes from. Is it a peculiarity that is somehow confined only to K mesons? Or is it a generic feature? To answer these questions, raised by Cronin in his Nobel prize speech, we need to study CP violation in another system that will allow us to get answers with fewer theoretical uncertainties.
- Collide electrons and positrons to create B anti-B meson pairs, hence name of detector - BaBar. Japanese B Factory located in Tsukuba was completed at about the same time and has similar performance, so we are in a race with them.
- The BaBar detectors is a huge enormously complicated instrument. It weighs 1200 tons, has hundreds of thousands of readout channels and involves cutting edge technology in electronics, instrumentation and computing. It took 500 physicists about 5 years to build it at a rough cost of $100M. About half of the physicists come from countries outside the US, and they contributed about half the cost as well.
- The Babar detector consists of layers of detectors, beginning with the precise silicon vertex detectors close to the interaction point to measure the B decay vertices, followed by drift chambers to track charged particles inside a magnetic field, particle identificaiton devices, calorimetry to measure photons and electrons, and muon detectors located in the iron yoke of the magnet.
- The asymmetric B factory concept is illustrated here. Imagine this is the beampipe, and the e- beamcomes this way and collides with lower energy e+ beam here, producing the Upsilon (4S) resonance… Mention tagging
- Here is the recipe that we must follow to measure CP violation in B decays. The end result is a histogram such as you see here. We are looking for a difference between the red curve and the blue curve. The area under each curve is the same, which means there are just as many B0 events as B0-bar events. We have to see the time separation between their vertices in order to detect the asymmetry - this is the reason for the unequal beam energies.
- You might be wondering what is is like to work with 500 other physicists, and how we ever got organized enough to build such a complicated detector. The answer is that the BaBar detector is divided into several different sub-detectors, and smaller groups were organized to build each of these. I led a group of 6 US and 6 Italian institutions that built the silicon vertex tracker, or SVT. This device uses precision silicon microstrip detectors with an accuracy of about 1/100th of a mm, allowing us to point back to where the B meson decayed with an accuracy of 1/10th of a mm.
- This shows an end view of the SVT and how the charged tracks bend in the magnetic field. Each blue line is a detector that registers a hit wherever a track crosses it.
- I’ve tried to show that antimatter is very similar to matter at the particle level. However, when we look around our Universe there is noticeable problem: everything is made of matter and there is very little antimatter. In the Big Bang... If there were regions of antimatter in our Universe, we would expect to detect the characteristic photons created when matter and antimatter annihilated at the interface. Experiments have searched for this signature and found nothing. Andrei Sakharov, the dissident Russian physicist who was awarded the Nobel Peace Prize, made a remarkable observation back in 1967.
- To complete our picture of matter, we have to describe how the fundamental particles interact. We have identified just 4 forces, each with its own associated carrier particle which transmit the force between particles. Higgs - another lecture topic. An elusive particle that is responsible for giving mass to all particles.