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Implications of D-Mixing for New Physics

Implications of D-Mixing for New Physics. Meson mixing has historical significance Charm quark (and mass) inferred from Kaon mixing Top mass predicted from B d mixing Strong constraints on New Physics (SUSY, LRM, …) that has affected collider searches Each meson is different (x = m/) :

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Implications of D-Mixing for New Physics

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  1. Implications of D-Mixing for New Physics Meson mixing has historical significance • Charm quark (and mass) inferred from Kaon mixing • Top mass predicted from Bd mixing • Strong constraints on New Physics (SUSY, LRM, …) that has affected collider searches Each meson is different (x = m/): And thus each measurement is important 0.776, J. Hewett SLAC 07

  2. The observation of D-mixing is exciting! • 1st Observation of Flavor Changing Neutral Currents in the up-quark sector! • 1st Glimpse of flavor physics in the up-quark sector • 1st Constraints on flavor violation in up-quark sector • Sparked much interest in the community • Catalogue of New Physics Contributions • Golowich, JLH, Pakvasa, Petrov arXiv:0705.3650

  3. Compilation of Predictions for D-Mixing • D-Mixing provides important constraints for model building • Flavor physics provides strong constraints on models • Many models poorly tested in +2/3 quark sector • Many models shove flavor violation into up-quark sector in order to satisfy K mixing  large effects in D mixing H. Nelson, Lepton-Photon 1999

  4. D-Mixing in the Standard Model: Short Distance • Box diagram is tiny • GIM is efficient! • b-quark contribution is CKM suppressed • s-quark contribution is suppressed by SU(3) breaking • xbox ~ 10-5 , ybox ~ 10-7 • Higher orders in the OPE may give larger results Georgi; Bigi

  5. D Mixing in the Standard Model: Long Distance • Charm is neither light or heavy, so well-developed theoretical techniques don’t apply. • Sum over all possible, multi-particle, intermediate hadronic states • yD is less model-dependent; calculate yD and use dispersion relations to obtain xD • Can result in: yD ~ xD ~ 1% Possible that experimental result is explained by SM effects

  6. Constraining New Physics • Assume no interference between SM & NP • NP alone does not exceed measured value of xD Use 1 value: xD < 11.7 x 10-3 Allow for 2 and for future exp’t improvements: xD < 3, 5, 8, 15 x 10-3

  7. New Physics in D-mixing: Formalism Use the OPE to define an effective Hamiltonian Complete set of independent operators: Calculate Ci at NP scale Evolve HNP to charm scale

  8. New Physics in D-mixing: Formalism Compute LO QCD corrections Anomalous dimensions matrix Evolve matching conditions to the charm scale

  9. New Physics in D-mixing: Formalism Evaluate hadronic matrix elements with We take BD = BD(S) = 0.82 (quenched lattice) fD = 222.6  16.7-2.4+2.3 MeV (CLEO-c)

  10. Extra Fermions Fourth Generation Heavy Vector-like Quarks Q=-1/3 Singlet Quarks Q=+2/3 Singlet Quarks Little Higgs Models Extra Gauge Bosons Generic Z’ Models Family Symmetries Left-Right Symmetric Model Alternate LRSM from E6 GUTS Vector Leptoquarks Extra Scalars Flavor Conserving 2 Higgs Doublet Models Flavor Changing Neutral Higgs Scalar Leptoquarks Higgsless Models Extra Symmetries Minimal Supersymmetric SM Quark-Squark Alignment R-Parity Violation Split Supersymmetry Extra Dimensions Universal Extra Dimensions Split Fermion Models Warped Geometries Models Considered

  11. Heavy Q=-1/3 Quark Present in, e.g., • E6 GUTS • 4th generation Constraints in mass-mixing plane Removes strong GIM suppression Of SM 3 Unitarity of CKM matrix gives |Vub’Vcb’|< 0.02 5 8 D-mixing improves this constraint by one order of magnitude! 11.7 15 x 10-3

  12. Heavy Q=2/3 Singlet Quarks • Induces FCNC couplings of the Z • Violation of Glashow-Weinberg-Paschos conditions • Tree-level contribution to D mixing Constraints on mixing improved over CKM unitarity bounds by TWO orders of magnitude!

  13. Little Higgs Models Arkani-Hamed, Cohen, Katz, Nelson Sample particle spectrum These models contain heavy vector-like T-quark Strongest bounds on this sector! Will affect T-quark decays and collider signatures

  14. Little Higgs Models with T-parity Scan over numerous parameters Buras etal

  15. Generic Z’ Models • Many models have Z’ bosons with flavor changing couplings • Induces tree-level FCNC Z’ CL = CR = C Either C is extraordinarilysmall, or FC Z’ is unobservable @ VLHC

  16. Left-Right Symmetric Model L,R • Restores parity @ high energies • SU(2)L x SU(2)R x U(1)B-L • Seesaw mechanism for  masses L,R • Parameters: • = gR/gL • Right-handed CKM • WR mass =1 Bounds from K mixing: MWR > 1.6 TeV w/ manifest LRS

  17. 2-Higgs Doublet Model • Model II: One doublet gives mass to down-type quarks, second to top-type quarks • Model I: interesting region excluded by b  s • v2 = v12+v22 ; tan = v2/v1

  18. 2HDM: Negligible Effects in D Mixing

  19. Flavor Changing Neutral Higgs • Models w/ multiple Higgs doublets naturally lead to tree-level FCNC • General discussion: • Severe constraints in d-quark sector from K-mixing

  20. Cheng-Sher Ansatz • Specific flavor changing Higgs model, where couplings take the form Tree-level t-h Box

  21. Supersymmetry (MSSM) Large contribution from squark-gluino exchange in box diagram helicity index • Super-CKM basis: • squark and quark fields rotated by • same matrices to get mass eigenstates • Squark mass matrices non-diagonal • Squark propagators expanded to • include non-diagonal mass insertions mass insertion Strong constraints from K mixing has historically lead to assumption of degenerate squarks in collider production

  22. MSSM: All 8 operators contribute

  23. Constraints on up/charm-squark mass difference LL,RR LL=RR LR,RL LR=RL

  24. Compare to constraints on down/strange-squark mass difference from Kaon mixing (green curve) Bagger, Matchev, Zhang   LL,RR LL=RR   LR,RL LR=RL

  25. Supersymmetry (MSSM) • 1st two generations of squark masses now constrained to be degenerate to same level of precision in both Q=+2/3 and -1/3 sectors! • Historically used as a theoretical assumption, now determined experimentally • Degenerate squarks lead to large squark production cross section @ Tevatron/LHC

  26. Other Supersymmetric Contributions are Negligible Box diagram exchange: • 1 neutralino + 1 gluino with up/charm-squarks mass insertions, subleading to 2 gluino graph by (g/gs)2 • Neutralinos with up/charm-squarks mass insertions, suppressed by (g/gs)4 • Charginos with d/s/b-squarks diagonal squark propagators, flavor violation from CKM structure  SUSY-GIM cancellation in effect as d/s/b-squarks are essentially degenerate • Charged Higgs small, as shown above This is a very different situation than with Bd and Bs mixing!

  27. Supersymmetry with Alignment Nir, Seiberg • Quark & squark mass matrices are approximately aligned and diagonalized such that gluino interactions are flavor diagonal • Squark mass differences are not constrained • Bounds from Kaon mixing prevent generation of Cabibbo angle in the down-sector ~ Sets mq≥ 2 TeV Difficult @ LHC!

  28. Supersymmetry with R-Parity Violation Most general superpotential allows for B & L violating terms which also violate R-parity Many constraints on these couplings from rare processes

  29. RPV Contributions to D Mixing L ≠ 0 terms: B ≠ 0 given by slepton  d-squark No tree-level contribution! Taking Factor of 50 (250) stronger than previous bounds for i = 2 (3) ! Taking strengthens the bound by factor of ~ 4

  30. Constraints on R-Parity Violation Setting

  31. Extra Dimensions: Split Fermion Scenario Arkani-Hamed, Schmaltz • Fermions localized at • specific locations in extra • flat dimension • Suppresses proton decay • Generates fermion • hierarchy • Gauge boson Kaluza Klein states couple via overlap of wavefunctions • Generates FCNC by rotation to quark mass basis

  32. Constraints on Split Fermion Scenario Compactification scale Distance between u- & c-quarks in 5th dimension u- & c-quarks are localized very close or extra dimensions unobservable @ VLHC

  33. Constraints from Other Meson Mixings • D Mixing • K Mixing • Bs Mixing • Bd Mixing • Each system constrains different quark spacings • D Mixing gives strongest constraints!

  34. Extra Dimensions: Universal Extra Dims Appelquist, Cheng, Dobrescu • All SM fields in TeV-1, 5d, S1/Z2 bulk • No branes!  translational invariance is preserved  tree-level conservation of p5 • KK number conserved at tree-level:broken at higher order by boundary terms • KK parity conserved to all orders, (-1)n Spectrum looks like SUSY Sizeable effects in B & K systems (Buras etal)

  35. UED: Negligible Effects in D Mixing Primarily affects 3rd generation KK mass spectrum: Boundary terms: n n n n UED GIM: exact cancellation level by level in KK tower!

  36. Extra Dimensions: Warped Geometries Based on Randall-Sundrum models Bulk = Slice of AdS5 • SM in the bulk • Induces tree-level FCNC • Result dependent on • fermion localization  TeV brane Planck brane 

  37. Constraints on Warped Geometries 3 popular scenarios for fermion placement in the bulk 1st gauge KK state M > 2-3 TeV Restricts LHC search range

  38. Unparticle Physics Banks, Zaks Based on nontrivial scale invariance in the IR • Scale invariant stuff cannot have definite mass (masses can be rescaled by a scale transformation) • A free massless particle is scale invariant • In QFT, fields can also be multiplied by fractional powers of a rescaling parameter  unparticles! • Related to formal work in conformal theory • Unparticles interact w/ SM fields and match onto Banks-Zak operators at scale  • What do unparticles look like in the laboratory? Georgi Unparticle stuff with scale dimension d looks like a non-integral number of invisible particles

  39. Constraints on Unparticles from D Mixing - Operator for D mixing: (1/) (d-1) c( + r5)u + hc Probes the Planck scale! r = 1 LH r = 0 V r = -1 RH JLH, T Rizzo, in prep

  40. Summary of Model Constraints

  41. Conclusions • Observation of D-mixing yields stringent bounds on New Physics • These bounds surpass or compete with other constraints • These bounds affect collider(LHC) physics • Look forward to future experimental refinements! • Observation of CP Violation would be clear signal of New Physics…

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