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1 1 Babar and L. De Brunhoff David Hitlin Caltech Lets Celebrate Jonathan July 24, 2008 CP Violation and Slide 2 2 2 Babar and L. De Brunhoff David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 3 3 3 L. De Brunhoff B A B AR was a great adventure for two decades, now nearly concluded This day, devoted to highlighting Jonathan Dorfans many contributions, is, of course, a most appropriate one to look back on BABAR and its accomplishments Jonathan served as head of the PEP-II project and as BABAR s Technical Coordinator, succeeding Vera Lth His leadership in these endeavors, as in many others, was characterized by his skill, drive, understanding of people, deal-making ability and his ability to keep his eye on the ball The latter is perhaps best characterized by the B A B AR / PEP-II mantra: What is the effect of .. on the measurement of sin2 ?, where .. could be degree of mode suppression in the RF cavities gauge of magnet power supply cables length of the CsI(Tl) crystals thickness of the drift chamber end plates or any of a thousand other decisions we had to make David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 4 4 4 L. De Brunhoff CP violation and baryogenesis The experimental study of CP violation dates back to 1964, when Christensen, Cronin, Fitch and Turlay discovered that the decays of K L mesons violate CP invariance by ~2 parts per thousand In 1967 Andrei Sakharov showed the connection between CP violation and the dominance of matter over antimatter in the universe In the Big Bang there was, by assumption, an equal amount of matter and antimatter in the universe (i.e., the net baryon number of the universe was zero), but we now live in a matter universe The Sakharov conditions for the disappearance of the antimatter: Violation of C and CP symmetry observed, allowed in the Standard Model Baryon number-violating interactions - beyond the Standard Model Departure from thermal equilibrium (an arrow of time) - inflation David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 5 5 5 Babar and L. De Brunhoff Well up above the tropostrata There is a region stark and stellar Where, on a streak of anti-matter Lived Dr Edward Anti-Teller. Remote from Fusion's origin, He lived unguessed and unawares With all his antikith and kin, And kept macassars on his chairs. One morning, idling by the sea, He spied a tin of monstrous girth That bore three letters: A. E. C. Out stepped a visitor from Earth. Then, shouting gladly o'er the sands, Met two who in their alien ways Were like as gentils. Their right hands Clasped, and the rest was gamma rays. The New Yorker, 1955 ERDA DOE Perils of Modern Living Harold P. Furth David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 6 6 6 L. De Brunhoff CP violation and baryogenesis The annihilation of matter and antimatter in the very early universe was nearly complete: only a tiny fraction of the baryons escaped annihilation: A quantitative measure of the process at early times is provided by the ratio of baryons to relic photons in the cosmic microwave background n baryons /n photons = (5.1 +0.3-0.2)x10 10 The baryons that escaped annihilation were those that could not find a an antiparticle partner, the partner having preferentially decayed due to CP violation in the weak interaction However, the expected Standard Model scale of CP violation is far too small to produce this many baryons. A t best, the Standard Model can produce n baryons /n photons ~ 10 20 Getting a clear handle on the precise strength of CP violation in K L decay was hard because K L mesons are so light, it is difficult to connect the CP asymmetry measured at the meson level with the underlying strength at the quark level David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 7 7 7 L. De Brunhoff Slide 8 8 8 The situation in the mid 80s In 1981 Bigi and Sanda showed that a measurement of CP violation in B 0 meson decay to CP eigenstates could be clearly interpreted, without theoretical uncertainties. The prospect of a clean measurement in B 0 decays was exciting; perhaps the Standard Model prediction of the strength of CP violation would fail With the observation in 83 of a long B meson lifetime by Mark II and MAC and in 87 of substantial B d mixing by ARGUS and UA1, one could contemplate measuring CP -violating asymmetries in B 0 meson decays Doing so would require flavor-tagging a B meson and then untangling mixed from unmixed decays, which could be done using B s produced in e + e - annihilation or in hadronic collisions However, at least 10 7 -10 8 B pairs would be needed, a 2-3 order of magnitude increase in the existing data sample Exploiting the quantum correlations of pairs produced in ( 4S ) decays in e + e - seemed like a particularly elegant approach, but separating the decays was difficult as the B 0 lifetime in the laboratory corresponds to 19 m David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 9 9 9 L. De Brunhoff The Gold Rush This led to at least 21 e + e - B Factory concepts and proposals (19 ( 4S ) + 2 Z 0 ) and several hadronic machine approaches (HERA-B, .) Oddones concept of using an asymmetric e + e - collider to boost the distance between the two decay vertices o an measurable regime was, in the end, the most successful approach Two colliders, PEP-II and KEKB, were ultimately built ( 4S ) Storage Rings ( 4S ) Linac-Ring Collider ( 4S ) Recirculating Linear Collider Z Factory SymmetricAsymmetric PSI (2)APIARYGrosse-WiesmannAmaldi/CoignetSLC NovosibirskCITARJLABARESLEP KEK accumulatorPETRA-IIUCLA CESR PlusPEP-IITBA ISR Tunnel KEK accumulator KEK-B CESR-B David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 10 10 10 Babar and L. De Brunhoff The resonances in e + e - annihilation: non-relativistic atomic systems M s) = 10.5794 + 0.0012 GeV s) = 20.5 + 2.5 MeV A practical application of EPR David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 11 11 11 L. De Brunhoff Motivation for B 0 meson CP Violation measurements Since CP violation is a necessary ingredient to produce a baryon asymmetry, and since the theoretical strength of CP violation in the three generation Standard Model is numerically insufficient to produce the observed asymmetry, it was hoped that a measurement of a CP -violating asymmetry that could be unambiguously related to the Standard Model CP phase would produce a surprise The result was that the Standard Model phase produces exactly the needed amount of CP violation for B meson decays to pass the overconstrained Unitarity Triangle tests Thus at this point, experimentally the Standard Model does not have the strength of CP violation to produce the observed baryon asymmetry How do we measure the strength of CP violation in the Standard Model? David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 12 12 12 L. De Brunhoff The B Unitarity Triangle David Hitlin "Let's Celebrate Jonathan" July 24, 2008 The CKM matrix describing the transitions among the three quark generations is unitary There are six unitarity relations The most useful unitarity condition is: The sides of the unitarity triangle are determined by measurements of the magnitudes of CKM matrix elements CP -violating asymmetries in B 0 decays to CP eigenstates measure the angles of the unitarity triangle, thereby providing an overconstrained situation and thereby a unique test of the Standard Model in the CKM sector Slide 13 13 13 L. De Brunhoff David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 14 14 14 Babar and L. De Brunhoff To measure a phase, you need interference of two amplitudes CP violation can arise due to interference between two amplitudes with different phases - a weak phase that changes sign under CP and a strong phase that is invariant under CP. if CP f A 1 A e i e i A 2 A e i e i A 2 A e i e i i A 1 A e i e i David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 15 15 15 Babar and L. De Brunhoff The Unitarity Triangle in 1990 Dib, Dunietz, Gilman and Nir, Phys.Rev D41, 1522 (1990) David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 16 16 16 Babar and L. De Brunhoff Reconstruct exclusive B decays to CP eigenstates and flavor eigenstates and tag the flavor of the other B decay Measure z between B CP and B tag to determine the signed time difference t between the decays Determine the resolution function for z Overview of the analysis David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 17 17 17 Babar and L. De Brunhoff Canada[4/15] U of British Columbia McGill U U de Montral U of Victoria China[1/5] Inst. of High Energy Physics, Beijing France[5/51] LAPP, Annecy LAL Orsay LPNHE des Universits Paris 6/7 Ecole Polytechnique CEA, DAPNIA, CE-Saclay Germany[3/23] U Rostock Ruhr U Bochum Technische U Dresden USA[36/253] California Institute of Technology UC, Irvine UC, Los Angeles UC, San Diego UC, Santa Barbara UC, Santa Cruz U of Cincinnati U of Colorado Colorado State Elon College Florida A&M U of Iowa Iowa State U LBNL LLNL U of Louisville U of Maryland U of Massachusetts, Amherst MIT U of Mississippi Mount Holyoke College Northern Kentucky U U of Notre Dame Ohio State U U of Oregon U of Pennsylvania Prairie View A&M Princeton SLAC U of South Carolina Stanford U U of Texas at Austin U of Texas at Dallas Vanderbilt U of Wisconsin Yale 10 Countries 73 Institutions 521 Physicists The B A B AR Collaboration Italy[12/89] INFN, Bari INFN, Ferrara Lab. Nazionali di Frascati dell' INFN INFN, Genova INFN, Milano INFN, Napoli INFN, Padova INFN, Pavia INF, Pisa INFNN, Roma and U "La Sapienza" INFN, Torino INFN, Trieste The Netherlands [1/5] NIKHEF Norway[1/2] U of Bergen Russia[1/7] Budker Institute, Novosibirsk United Kingdom [10/71] U of Birmingham U of Bristol Brunel University U of Edinburgh U of Liverpool Imperial College Queen Mary & Westfield College Royal Holloway, University of London U of Manchester Rutherford Appleton Laboratory David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 18 18 18 Babar and L. De Brunhoff David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Si Vertex-Tracker, Drift Chamber, DIRC (Cherenkov), CsI-Calorimeter, Superconducting Coil, Iron Yoke + RPCs/LSTs The B A B AR Detector Slide 19 19 19 L. De Brunhoff The PEP-II Asymmetric B Factory David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Final collisions 12:43pm,Monday 7 Apr 2008 Slide 20 20 20 Babar and L. De Brunhoff David Hitlin "Let's Celebrate Jonathan" July 24, 2008 The need for speed Slide 21 21 21 Babar and L. De Brunhoff A tagged event David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 22 22 22 Babar and L. De Brunhoff David Hitlin "Let's Celebrate Jonathan" July 24, 2008 B A B AR employed blind analysis and sophisticated maximum likelihood techniques to extract maximum information from the data in an unbiased manner Slide 23 23 23 Babar and L. De Brunhoff sin2 in charmonium modes David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 24 24 24 Babar and L. De Brunhoff Measuring the Unitarity Triangle angles David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 25 25 25 Babar and L. De Brunhoff sin2 and David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 26 26 26 Babar and L. De Brunhoff Unitarity triangle constraints: sin2 , sin2 measurements The CKM matrix passes the unique, new overconstrained tests David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 27 27 27 Babar and L. De Brunhoff The Unitarity Triangle deconstructed Tree level Loop dominated Without sin2 Mixing David Hitlin "Let's Celebrate Jonathan" July 24, 2008 Slide 28 28 28 Babar and L. De Brunhoff Not even wrong! Slide 29 29 29 Babar and L. De Brunhoff It may not be quite so simple David Hitlin "Let's Celebrate Jonathan" July 24, 2008 There are discrepancies in CP asymmetries in b sss loop decays _ There are other hints that there could be additional phases, i.e., that there is more in the flavor sector than the three generation Standard Model Four generations can amplify the baryogenesis effect to the needed level: Hou (arXiv:0803.1234 [hep-ph] ) and can explain the various anomalies seen: Soni, Alok, Giri, Mohanta and Nandi (arXiv:0807.1971 [hep-ph] ) Super B, with a 100x larger data sample, will resolve these issues, and allow us to understand the flavor sector of New Physics found at LHC Slide 30 30 30 L. De Brunhoff The bottom line BABAR has tested the Standard Model in unique ways by finding and then deeply exploring CP violation in the B meson system BABAR has also done lots of physics beyond CP violation: Many other B decay studies, including other hadronic, leptonic and semileptonic decays and rare loop-dominated processes Weak decays of charm, including long sought evidence for mixing decays New hadronic states, some unexplained in QCD And just recently, the discovery of the b, the ground state of the system as of last week, 324 publications in refereed journals: PRL, PRD, NIM David Hitlin "Let's Celebrate Jonathan" July 24, 2008