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 J. Hewett SLAC DOE 07

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

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

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

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 Results in: yD ~ xD ~ 1% Possible that experimental result is explained by SM effects

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

New Physics in D-mixing: Formalism Compute LO QCD corrections Use the OPE to define an effective Hamiltonian Complete set of independent operators: Evolve matching conditions to the charm scale Evaluate hadronic matrix elements

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

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!

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

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

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

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

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

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! ~

Extra Dimensions Split fermion scenario: Fermions localized at specific locations in extra flat dimension Suppresses proton decay Generates fermion hierarchy Arkani-Hamed, Schmaltz Generates tree-level FCNC for gauge boson Kaluza Klein states via overlap of wavefunctions Gen

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

Warped Extra Dimensions Based on Randall-Sundrum models Bulk = Slice of AdS5 SM in the bulk Induces tree-level FCNC Result dependent on fermion localization 1st gauge KK state M > 2-3 TeV Restricts LHC search range

Summary of Model Constraints

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…