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J. Albert Caltech March 7, 2006

CP Asymmetry. CP Asymmetry. in Nature :. Selected Past, Present, and Future Investigations. J. Albert Caltech March 7, 2006. seminar. PHYSICS. Some Major Open Questions in. What is dark matter? What is dark energy?. Why is the universe made of matter, rather than antimatter?.

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J. Albert Caltech March 7, 2006

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  1. CP Asymmetry CP Asymmetry in Nature : Selected Past, Present, and Future Investigations J. Albert Caltech March 7, 2006 seminar

  2. PHYSICS Some Major Open Questions in • What is dark matter? • What is dark energy? • Why is the universe made of matter, rather than antimatter? • How does high Tc superconductivity work? How high can it go? • How heavy are the neutrinos? What was their role in the formation of the universe? • What is the number of dimensions in a fundamental theory of the universe? • Is there a quantum theory of gravity that can describe the world we live in?

  3. Matter vs. Antimatter t~0,N/ N~ 1 t~10–6 s,N / N~ 1 + 10–9 t~1 s, N / Ng ~ 10–9 Seminar3/07/06 CP Asymmetry in Nature J. Albert 3

  4. Sakharov’s Conditions CP In 1967, Sakharov identified 3 conditions for an initially symmetric universe to subsequently develop a matter-antimatter asymmetry (baryogenesis): • There must be processes that change the net matter-antimatter balance (ΔB+ΔL 0). • Some corresponding mirror (matter antimatter) processes must proceed at different rates (C,CP). • These processes must occur out of thermal equilibrium (assuming CP=T). Seminar3/07/06 CP Asymmetry in Nature J. Albert 4

  5. CP and the Standard Model • In the Standard Model, CP violation proceeds via weak mixing within the quark, and potentially the lepton, sectors. • More on leptons later. The quark mixing matrix, or CKM matrix, describes mixing in 3 generations via a 3x3 complex unitary matrix. • Number of complex phases can be “rotated away” via U(1) and SU(2), but 1 complex phase is irreducible. The CKM quark weak mixing matrix = (Wolfenstein parametrization) Seminar3/07/06 CP Asymmetry in Nature J. Albert 5

  6. A “Very” Brief History of CPV • CP violation was first discovered unexpectedly by Cronin and Fitch in 1964 in decays of KL mesons. • In 1973, Kobayashi and Maskawa developed an explanation by hypothesizing a 3rd generation of quarks (four years before the b was first observed). • Until 2001, CP violation had never been conclusively observed outside of the neutral kaon system. • 2001: BaBarand Belle first report CPV inB decays. • 2003- : Measurements of CP violation in loop and Cabbibo-suppressed modes at BaBar and Belle. • 1998-2004: Super-K and SNO discover neutrino oscillations (measurements improved by KamLand), raising the possibility of CPV in the lepton sector. Seminar3/07/06 CP Asymmetry in Nature J. Albert 6

  7. The Unitarity Triangle(s) • The constraint that the CKM matrix is unitary results in three equations (in the C plane) that must be satisfied: • Measurements sensitive to the lengths of the sides of the triangles indicate that (a) and (b) (sensitive to CPV in the K and Bs systems respectively) are nearly degenerate. • Only the 3rd triangle (c) (corresponding to decays in the B system) should have large CP violating effects. (a) (b) (c) Seminar3/07/06 CP Asymmetry in Nature J. Albert 7

  8. CP Violation in the B System • Certain decay modes of the B are common to both B0 and B0. For such decay modes, interference between the B0–B0 mixing and the decay results in a time-dependent asymmetry: CP mixing decay where . Three types of CP violation can occur: • “Direct” CP violation purely in decay: • CP violation purely in mixing: • CP violation in the interference between mixing and decay: Seminar3/07/06 CP Asymmetry in Nature J. Albert 8

  9. Experimental Technique Fully Reconstructed B (Flavor eigenstates or CP modes such as J/Ks, J/KL, +-, D(*)D(*),…) D*+ coherentB0-B0 production D0  - K+ D0 D*- (9GeV) (3.1GeV) B-Flavor Tagging Seminar3/07/06 CP Asymmetry in Nature J. Albert 9

  10. Present Constraints • Unitarity triangle constraints dominated by precise measurement of sin2β. • Orthogonal direction (essentially ) much less well-constrained, and primarily by indirect measurements. Seminar3/07/06 CP Asymmetry in Nature J. Albert 10

  11. The Angle  Now known to ~10-12º uncertainty Known to ….? Currently known to 1.6º uncertainty • We expect  to be approximately (57 ± 15)º, if the Standard Model is consistent. • But how to directly measure it… We have several ways of directly measuring .Combining information provides the best tests: D(*)0CPK(*)+(Gronau-London-Wyler) D0(Kπ)h+(Atwood-Dunietz-Soni) D(*)0(D03-body)K+(Dalitz, GGSZ) sin(2β+) from D(*)π/D(*)ρ 4a)assisted by Ds(*)π/Ds(*)ρ sin(2β+) from D(*)0K(*)0 D(s)(*)D(*) combined fit Seminar3/07/06 CP Asymmetry in Nature J. Albert 11

  12. Constraints on  Direct CP violation in B  D0(KSπ+π-)K (Dalitz-dependent CPV) • The D0K and D0K amplitudes have a relative weak phase of .  • But 2 more pieces of information are required!: • Relative magnitude • Strong phase difference δB Sensitivity to g 180  = (73 ± 47)° rB< 0.18 (90% c.l.) 0 g 95% 68% -180 0. 0.3 Time-Dependent CP violation in B0 D*-π+ • |sin(2b+g)| > 0.75 at 68% CL • |sin(2b+g)| > 0.58 at 90% CL  = (64 ± 26)° rB= 0.21 ± 0.09 Seminar3/07/06 CP Asymmetry in Nature J. Albert 12

  13. A Different Approach:Using B  D(s)(*)D(*) • The CP asymmetry from the D(*)D(*) tree amplitude measures sin2β, so where does  come in? •  comes from the u- and t-penguin terms: • For a given B D(*)D(*)decay, there are 3 observables: a branching fraction, a direct CP asymmetry, and a time-dependent CP asymmetry (3 of each – one for each helicity state – in the case of D*+D*-): Seminar3/07/06 CP Asymmetry in Nature J. Albert 13

  14. How can D(s)(*)D(*)decays measure gamma? • This is 3 equations in 5 unknowns. More information required… • The additional information can be obtained by inputting two things: 1) beta, as determined from charmonium decays, and 2) branching fractions of B Ds(*)D(*)decays. • SU(3)-breaking in the relation between D(*)D(*)and Ds(*)D(*)is parameterized by the ratio of decay constants Δ= fDs(*)/fD(*) Δ fDs/fD = 1.22 ± 0.04(lattice QCD, Becirovic et al. 2003). • Thus, the 3 equations in 3 unknowns can be solved into a single equation for : solution for  (in V-V and P-P modes) where: Seminar3/07/06 CP Asymmetry in Nature J. Albert 14

  15. So, how do we get B, adir, and aindir? • We have branching fractions and CP asymmetries for B  D*+D*-and B  D*+D-decays and branching fractions for B  Ds(*)D(*)decays: Branching fraction and CP asymmetries for B  D*+D- Branching fraction and CP asymmetries for B  D*+D*- Phys. Rev. Lett. 90, 221801 (hep-ex/0303004) Phys. Rev. Lett. 91, 131803 (hep-ex/0306052) Phys. Rev. Lett. 89, 061801 (hep-ex/0203008) B (B0 D*+D*-) = (8.3 ± 1.6 ± 1.2) x 10-4 Seminar3/07/06 CP Asymmetry in Nature J. Albert 15

  16. Constraints on gamma from D(s)(*)D(*) • We determine constraints on  from a fit to this data on D(s)(*)D(*). J.A., Datta, & London Phys. Lett. B 605, 335 (hep-ph/0410015) Input measurements from… Constraints from vector-vector modes: Constraints from vector-pseudoscalar modes: (weak) Combined constraints: Seminar3/07/06 CP Asymmetry in Nature J. Albert 16

  17. The Status CP • Looking at the CP asymmetries in loop decays, there are no statistically significant deviations at this particular point in time. • However, such deviations have been well known to arrive (and occasionally depart) with added data. • Need additional statistitics to improve constraints and explore new avenues. Seminar3/07/06 CP Asymmetry in Nature J. Albert 17

  18. How about Leptons…? DL= L-L (leptons) DB= B-B (baryons) DB= DL= ±3 DB-DL= 0 temperature V(f) f • CP-violating phase in MNS matrix can also potentially generate asymmetry. • A neutrino Majorana mass would appear to be required for significant BAU. See- saw mechanism could potentially help explain both small neutrino masses and baryon asymmetry… same-sign μμ Seminar3/07/06 CP Asymmetry in Nature J. Albert 18

  19. The Leptonic Mixing Matrix Seminar3/07/06 CP Asymmetry in Nature J. Albert 19

  20. Higgs properties • Standard model Higgs: spin-0 and CP-even. • Extensions can beg to differ: • 2HDM • MSSM contains h, H (CP-even), and A (CP-odd). • Given a general set of complex mixing parameters, neutral Higgs sector will mix, and mass eigenstates (h1,h2,h3) will have mixed CP. (Carena, Ellis, Mrenna, Pilaftsis, Wagner. Nucl.Phys. B659 (2003) 145-178, hep-ph/0211467) • Knowing Higgs propertiesnecessary for constraining models. • Low mass Higgs (< 150 GeV): t(t)H is main channel for Higgs properties • High mass Higgs: use 4 leptons (ZZ(*) or WW(*)) Seminar3/07/06 CP Asymmetry in Nature J. Albert 20

  21. Higgs production and decays Production cross-sections Branching fractions Seminar3/07/06 CP Asymmetry in Nature J. Albert 21

  22. Keys to Survival for low-mass H • In order to manage the low cross-section for ttH, one must keep the efficiency as high as possible without introducing additional backgrounds. • Efficiency for top reconstruction is ~20%, so by reconstructing both tops, one would be reduced to ~4% from top reco alone. • But let’s reconstruct just one of the tops. As we’ll show, using just one of the tops provides enough information to extract Higgs CP. And either top will do. So instead of 4%, one is up to ~36%, nearly an order of magnitude!! • But does this introduce large additional backgrounds? • Events containing reconstructed Higgs + top are dominated by tt+X, so no! Seminar3/07/06 CP Asymmetry in Nature J. Albert 22

  23. Higgs CP Determination • From Gunion, He (PRL 76, 24, 4468 (1996)): • With the increased efficiency from single top reconstruction, sensitivity can likely be obtained with a few years (100-200 fb-1) of data, as an estimate. Interaction Lagrangian: (c is CP-even coupling and d is CP-odd) SM: c=1, d=0 CP-sensitive variables: pT of Higgs, or missing pT from partial reconstruction can be substitutedfor pT of second top. Seminar3/07/06 CP Asymmetry in Nature J. Albert 23

  24. Partial Reco Higgs CP Determination a1 CP-even b2 CP-even a2 CP-even b1 CP-even b3 CP-even b4 CP-even b3 CP-odd b4 b2 CP-odd a1 CP-odd a2 CP-odd b1 CP-odd “b2” “b3” “b4” CP-even “a1” CP-even “a2” CP-even “b1” CP-even “b4” CP-odd “b3” “b2” CP-odd “a1” CP-odd “a2” CP-odd “b1” CP-odd CP-sensitive variables: (Gunion & He, PRL 76, 4468 (1996)) CP-odd -1 0 1 -1 0 1 -1 0 1 -1 0 1 -1 0 1 -1 0 1 Partial Reconstruction: pT of Higgs can be substituted for pT of one of the tops: CP-even CP-even CP-odd -1 0 1 -1 0 1 -1 0 1 -1 0 1 -1 0 1 -1 0 1 Seminar3/07/06 CP Asymmetry in Nature J. Albert 24

  25. 1.5 GeV Linac 2 GeV Linac 1.5 GeV Linac Damping Rings 2 GeV e- Gun e+ Gun Linac Linac Studies Seminar3/07/06 CP Asymmetry in Nature J. Albert 25

  26. A Few Super B-Factory Concepts E e+ source 5 GeV e- source Seminar3/07/06 CP Asymmetry in Nature J. Albert 26

  27. Other Super B-Factory Concepts Kickers Kicker Decelerating cavities (~2 GeV) Accelerating cavities (~2 GeV) e+ source (KAPS) 5 GeV 6 km circumference 5 GeV linac Polarized e- gun Seminar3/07/06 CP Asymmetry in Nature J. Albert 27

  28. CP Asymmetry • The enduring potential for CP-violating anomalies in the quark sector, and the possibilities of CP violation in both the lepton sector as well as the unexplored Higgs sector require a great deal of further study. • Source potentially also something completely different, e.g. gravitational waves inducing lepton number violation. Or a combination of several different sources • It is most definitely even possible that CP violation responsible for the BAU lies beyond foreseeable experimental reach. • Since we have promising asymmetry-producing avenues to explore and fundamental parameters to be measured… -- they need to, and will, be explored and measured. Seminar3/07/06 CP Asymmetry in Nature J. Albert 28

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