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Rare Kaon Decays -1

Rare Kaon Decays -1. Laurence Littenberg BNL E. Fermi School, Varenna - 22 July 2005. Organization. Introduction & general motivation Lepton Flavor Violation, etc. Brief review of Unitarity K +  +  K L  0  K  K L  l + l - K L  0 l + l -. What makes decays rare?.

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Rare Kaon Decays -1

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  1. Rare Kaon Decays -1 Laurence Littenberg BNL E. Fermi School, Varenna - 22 July 2005 L. Littenberg – Varenna

  2. Organization • Introduction & general motivation • Lepton Flavor Violation, etc. • Brief review of Unitarity • K++ • KL 0 • K • KLl+l- • KL0l+l- L. Littenberg – Varenna

  3. What makes decays rare? Common decay: Rare by virtue of kinematics: Rare since suppressed to 2nd order: L. Littenberg – Varenna

  4. Motivation for rare K decay experiments • Forbidden • S.M. forbids or greatly inhibits many kinematically possible decay mode • A number of these are allowed or enhanced by alternative approaches • Accessible sensitivity to these processes corresponds to very high mass scales • Discouraged • Certain very inhibited processes cleanly sensitive to S.M. parameters • Tolerated • Suppressed processes are a good area for testing chiral perturbation theory and other approaches to understanding the low energy structure of the S.M. L. Littenberg – Varenna

  5. Rare K decay modes studied recently L. Littenberg – Varenna

  6. d W gsinC u s  Lepton Flavor Violation Poster child for sensitivity to BSM processes such as  Attainable sensitivity corresponding To MX  100 TeV, clean signatures • Most BSM theories predict some LFV in K decays: • Extended Technicolor • SUSY • heavy neutrinos • horizontal gauge bosons • Problem: s-channel mechanisms tend to give too much K0-K0 mixing • Necessary to measure both 2- and 3-body decays • check Lorentz structure of any new interaction • generation number sensitivity Current status L. Littenberg – Varenna

  7. AGS-871 • 15TP AGS p @ 24 GeV • 3.75°, 64sr beam • 200M KL/1.6sec spill • 6B neutrons • two- arm d.c. spectrometer • Beamstop in the middle! • US planes straws w/fast gas • Redundant p measurement p/p ~ 1% • m =1.1 MeV/c for KL+- • Threshold Cerenkov counter + LG array for electrons • Muon range stack • ~5% momentum resolution L. Littenberg – Varenna

  8. E865 • Unseparated 6 GeV/c positive beam, 70 MHz of K+, 20 more +’s & p’s • 10% of K’s decay in the tank • Double magnet MWPC spectrometer • Two stages of threshold Č counters • Shashlyk calorimeter • Muon range device • Did much more than just search for K+++e- (e.g. Ke3, Ke4) L. Littenberg – Varenna

  9. KTeV E865 E871 Generic LFV KLe Ke Adapted from T. Rizzo hep-ph9809526 L. Littenberg – Varenna

  10. LFV in the MSSM Lepton flavor violation in K decay is allowed in the MSSM by diagrams like those at right (A. Belyaev et al., hep-ph/0008276) But the rate from such diagrams is very suppressed wrt current experimental sensitivity. The effects in K decay are also suppressed relative to those in rare muon processes such as e and -e-in the field of a nucleus The can be seen in the plots at right that show the predictions for KL e, e , and -e-conversion assuming the same values of SUSY parameters (<0, tan =20, m½ = 150 & 250GeV, vs m0). The dotted horizontal lines indicate the the current upper limits on e and -e-conversion. There are proposals to push the sensitivity of both muon processes by more than three orders of magnitude. 10-14 10-16 10-18 10-9 10-11 10-13 10-12 10-14 10-16 L. Littenberg – Varenna

  11. LFV & LNV in SUSY-2 Once R-parity is relaxed, LFV effects in SUSY can be large: Current LFV data itself gives strictest limits on the couplings. e.g. B(KLe) < 4.7  10-12 gives – i21’i12 and i12’i21  6.2  10-9(m/100GeV)2 & 2i1’1i2 and 1i1’2i2  1.9  10-7(m/100GeV)2 SUSY can also give like-sign lepton decays like K+-+e+through b mixing, e.g.: ~ ~ However the sensitivity for these is much reduced. Even setting the b mixing matrix Element to 1, current limit B(K+-+e+) < 5  10-10 would give ’2k2’11k  10(md/100GeV)2 ~ k L. Littenberg – Varenna

  12. LNV & Majorana Neutrinos Explanations of neutrino mixing tend to involve Majorana neutrinos. These can mediate processes like K+-+  + that violate LNV as well as LFV Tends to be undetectably small, but there’s a possibility of “resonant enhancement” of the left-hand diagram for heavy neutrinos in the mass range 245-389 MeV. Present limit (from AGS-865) is B(K+-+  +) < 3  10-9 @ 90% CL. This gives a constraint |Uj|2(5.61)10-9 (see Dib et al., hep-ph/0011213) Appel et al. PRL 85 2877 (2000) L. Littenberg – Varenna

  13. KL0e Prospects for LFV Experiments • Last round of experiments pretty much killed the most promising theoretical predictions. • Theorists now pointing at rare muon processes • There are exceptions, e.g. Frère et al. hep-ph/0309014, large extra dimensions • Future progress on LFV kaon decays likely to be slow • No dedicated experiments on the horizon • Background getting harder to fight: L. Littenberg – Varenna

  14. J-PARC Facility Hadron Experimental Facility Materials and Life Science Experimental Facility Nuclear Transmutation 500 m Neutrino to Kamiokande 3 GeV Synchrotron (25 Hz, 1MW) 50 GeV Synchrotron (0.75 MW) Linac (350m) January, 2005 J-PARC = Japan Proton Accelerator Research Complex L. Littenberg – Varenna

  15. J-PARC: Accelerator complex • Phase 1 + Phase 2 = 189 billion Yen (= $1.89 billion if $1 = 100 Yen). • Phase 1 = 151 billion Yen for 7 years. • Construction budget does not include salaries. L. Littenberg – Varenna

  16. Construction Schedule Phase 1 Completion Construction Start L. Littenberg – Varenna

  17. Proton accelerator in the world L. Littenberg – Varenna

  18. Expected intensity of charged K beam • Relatively larger increase for K- and K0 of higher momentum (≧1 GeV). • Factor 5-10 increase from BNL AGS intensities. • Issues - duty factor, competition for protons (from ) L. Littenberg – Varenna

  19. T-violation in K3 • Look for polarization asymmetry of + polarization in K+0+ • Interference of SM and new physics magnifies effects (i.e. a 10-6 effect in the BR  10-3 effect in this polarization) • Particularly sensitive to multi-Higgs models, some SUSY, LQ, etc. L. Littenberg – Varenna

  20. KEK-246 Detector L. Littenberg – Varenna

  21. Muon Polarimeter L. Littenberg – Varenna

  22. E246 Method L. Littenberg – Varenna

  23. J-PARC Progress in T-violation PT = -0.00180.023stat0.0011syst (|PT| < 0.0051 @ 90% C.L.) Im = -.00550.0073stat0.0036syst (|Im| < 0.016 @ 90% C.L.) E246: In 3 HD Model, corresponds to neutron EDM < 910-27 (cf 6.310-26) L. Littenberg – Varenna

  24. K3 Polarization at J-PARC Goal: measurement of PT in K3 and in K++ to 10-4 L. Littenberg – Varenna

  25. 90% CL upper limits on non-SM Decays T-viol K3 K++ L. Littenberg – Varenna

  26. T-viol K3 LIMIT 90% CL upper limits on non-SM Decays K++ L. Littenberg – Varenna

  27. C.f. E949 search for K++ near the m=0 endpoint, see no events, extract B(K++) <2.310-9 @ 90% C.L. (hep-ex/0505069). Would give NC>14 GeV, not competitive with LEP Z. which gives NC>118 GeV. (would need to get below 4 10-13) K++ Violates angular momentum conservation, etc. Who would even bother thinking about it? B(K++) = 810-17(1TeV/NC)4 (hep-ph/0507231) L. Littenberg – Varenna

  28. Summary of BSM Searches • Dedicated experiments at BNL brought sensitivities in LFV processes to 10-11. • More or less wiped out the theories that motivated them • MSSM tends to predict very small BR’s • Looking under the lampost • New theoretical motivation developing slowing • Further progress would require substantial investment • Although 5-10 more incident protons available • Developed techniques in beams and detectors that will be useful in Kll • Other BSM searches mainly by-products of experiments dedicated to other processes • E.g. KTeV gets KLe e from KL+-e+e- (not main object) • The one exception is T-violating + polarization in K3 decay likely to be pursued at J-PARC ± ± L. Littenberg – Varenna

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