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Review of Charm Mixing

Review of Charm Mixing. HQL 2004 San Juan, Puerto Rico. June 1, 2004 Kevin Flood University of Massachusetts, Amherst. Outline. SM & New Physics predictions Charm mixing formalism Current experimental status Future outlook Further references. Charm Mixing in the Standard Model.

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Review of Charm Mixing

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  1. Review of Charm Mixing HQL 2004San Juan, Puerto Rico June 1, 2004 Kevin Flood University of Massachusetts, Amherst

  2. Outline • SM & New Physics predictions • Charm mixing formalism • Current experimental status • Future outlook • Further references

  3. Charm Mixing in the Standard Model • Box diagram SM charm mixing rate naively expected to be very low (Rmix~10-10) (Datta & Kumbhakar) • Z.Phys. C27, 515 (1985) • CKM suppression → |VubV*cb|2 • GIM suppression → (m2s-m2d)/m2W • di-penguin mixing, rmix~10-10(Petrov) • Phys. Rev. D 56, 1685 (1997) • Recent SM predictions can accom-modate high mixing rate (Falk et al.) • x,y≈ sin2 qC x [SU(3) breaking]2 ~1% • y: Phys.Rev. D 65, 054034 (2002) • x: hep-ph/0402204 (2004) V*ci Vui d, s, b u c D0 D0 W W d, s, b u c Vuj V*cj SM Mixing: box diagram SM Mixing Predictions best exp. limit on |y| u u u mixing rate = |amplitude|2 p+ D0 c d d W+ c d d W- p- D0 : x=DM/G : y=DG/2G u u u SM Mixing: a long-range contribution (Plot courtesy of A. Petrov, hep/ph 0311271)

  4. New Physics Charm Mixing Predictions • Possible enhancements to mixing due to new particles and interactions in new physics models • Most new physics predictions for x • extended Higgs, tree-level FCNC • fourth generation down-type quarks • supersymmetry: gluinos, squarks • lepto-quarks u c H0 u c FCNC u c b´ b´ u c fourth generation quark New Physics Mixing Predictions ~ g u c ~ current mixing experimental sensitivity ~ q q ~ g u c mixing rate = |amplitude|2 supersymmetry LQ u c x=DM/G l,n l,n LQ u c leptoquarks (Plot courtesy of A. Petrov, hep/ph 0311271)

  5. Measuring Mixing with D*+ D0+tag WS Decays • WS D0 decays from many sources • Mixing, DCS amplitudes interfere in non-CP hadronic final states • No DCS decays in semileptonic final states • Identical final state in SCS decays l+, u Mixing followed by CF or semi- leptonic decay 1, cos qc nl, d s c c cos qc u u u e/m, p u K DCS decay e+ e- event topology sin qc s c d sin qc u u tag beamspot D0 D*+ decay at interaction point near-future Babar SL analysis will hadronically reconstruct opposite charm in order to double-tag mixed events other charmed hadron

  6. Experimental Methods • In contrast to B mixing, cannot measure time-dependent flavor oscillations in charm mixing • Measure charm mixing using D*+ tagged decays: • WS D0 decays to hadronic (w/DCS interference) or semileptonic final states (B factories, FOCUS) • Compare ratios of lifetime from Kp to tagged D0, D0 decays into CP=+1 final states (B factories, FOCUS) • Time-integrated measurements exploiting coherent DD production at (3770) (CLEO-C only) D*+ D0+tag Wrong-sign tag decays D0K+p− D*+ D0+tag Right-sign tag decays K−p+ t (D0/D0K+p−) D0 tag decays t (D0p+p−or K+K−) t (D0/D0K+p−) D0 tag decays t (D0p+p−or K+K−)

  7. Time Dependence of DCS/Mixed Hadronic & Semileptonic Final States • Mixing implies that the physical states are not pure flavor states , rm ≠ 1CP-violation in mixing φ≠ 1CP-violation in interference between mixing and decay • Charm mixing values most often quoted using scaled parameters x, y • For |x|, |y| << 1, time-dependence of WS hadronic final states with mixing and DCS amplitudes where + (-) correspond to initial D0 (D0), and in the limit of no CP violation • Semileptonic final states retain only the term proportional to (Gt)2 with no possible strong phase , with dKp being the relative strong phase between DCS and mixing amplitudes

  8. Time Dependence of DCS/Mixed Hadronic & Semileptonic Final States • Hadronic WS time-dependence: • RDCS≡ 1, y´ = −0.3, |x´| = 0.3 • analyses using hadronic final states must fit time-dependence possibly close to a pure exponential • WS time-dependence for semi-leptonic analyses is well-distinguished from exponential

  9. Hadronic Kp Mixing (Babar: 57 fb-1 ) Babar Babar WS M(Kp) in DM sgnl region WSDM in M(Kp) sgnl region • Combined fit to M(D0), lifetime, M(D*+)-M(D0) • ~120,000 unmixed D0 events provide model from data for mixed signal pdf’s • Fit for RWS, RDCS, x´2, y, CP asym • NWS ~ 430 evts • Results consistent with no mixing, no CP asymmetries • Obtained unphysical result, x´2 < 0 • Upper limits calculated with toy MC using frequentist approach Babar Babar WS M(Kp) in DM sideband WSDM in M(Kp) sideband WS lifetime in M(Kp)+ DM sgnl region WS lifetime in M(Kp)+ DM side-band Babar Babar PDG 2004

  10. Preliminary Babar Semi-electronic Mixing (87 fb-1) • Combined fit to lifetime, M(D*+)-M(D0) • statistics-limited measurement • D0 lifetime+error consistent w/PDG value • Neural network D0 reconstruction • ~50,000 unmixed D0 events provide model for mixed decays • submitted to ICHEP 2004 WS DM D0 sgnl pkng D+ Babar Prelim. random D+ random D0 zero life RS DM signal region Babar Prelim. D0 sgnl D+ D0 bkgd zero life RSlifetime D0 sgnl D+ Babar Prelim. D0 bkgd zero life PDG 2004 (w/ICHEP+future Babar)

  11. Time Dependence of Decays to CP-Even Final States • For |x|, |y| << 1, the time-dependence of D0→ K+K- or p+p-D0→ K+K- or p+p- can be written • For decays to non-CP eigenstates have • The ratio of CP to non-CP lifetimes then becomes • If CP is conserved then the ratios are equal and

  12. Mixing Using CP-Even Eigenstates (Lifetime Ratio) • Some definitions Babar • If no CP violation in mixing (rm=1) (also, if φ=0 → Y=yCP, DY=0) Belle PDG 2004

  13. Current Charm Mixing Limits Lifetime Ratio Results Current Mixing Limits y (%) (Plot courtesy of D. Williams) (Plot courtesy of G. Burdman & I. Shipsey)

  14. Future Outlook • Near future • FOCUS: • Working on hadronic and semi-electronic mixing analyses (WIN 2003) • Belle: • ~300 fb-1 total integrated luminosity by end of current run • No hints of future charm mixing plans at recent conferences ? • Babar: • ~250 fb-1 total integrated luminosity by end of current run • Plans to update hadronic Kp mixing and lifetime ratio analyses • Time-dependent three-body Dalitz plot mixing • New semileptonic analysis using double-tagged events plus update of ICHEP result, ~linear statistical sensitivity increase • Long-term • CLEO-C: • DD coherent production • very clean charm samples • time-integrated msmts only • Belle/Babar: • ~500-600 fb-1 total integrated luminosity by end of running • BTeV: • O(109) charm decays!

  15. Recent Charm Mixing Review Articles • The following offer comprehensive and up-to-date guides, with copious citations, to the current state of charm mixing, theoretically (both articles) and experimentally (Burdman & Shipsey) • Charm Physics: Theoretical Review • A. Petrov (2003), hep-ph/0311371 • D0 Mixing and Rare Decays • G. Burdman & I. Shipsey, Ann.Rev.Nucl.Part.Sci, 431 (2003), hep-ph/0310076 • An earlier article also systematically compiles the many charm mixing predictions as of 1999 • Compilation of D0-D0 Mixing Predictions • H.N. Nelson, in Proceedings of the 19th Intl. Symp. on Lepton and Photon Interactions at High Energy (LP99), ed. J.A. Jaros & M.E. Peskin, SLAC (1999), hep-ex/9908021 • PDG 2004 also contains a review of charm mixing with citations to all exp. results presented herein • D. Asner (the previous speaker), updated Nov. 2003

  16. Backup slides

  17. FOCUS Semi-muonic Mixing (preliminary) • Combined fit to lifetime, M(D*)-M(D0) • D0 reconstruction using vertex location • ~6700 unmixed events • -14 mixed events • Rmix < ~0.0012 (90% CL) • Presented at ICHEP 2002 “A Search for D0 Mixing in Semileptonic Decays from FOCUS”, M. Hosack, Ph.D. thesis (2003) D0 lifetime

  18. Differences in Neutral Meson Mixing B, K Mixing DMd dG/dE Bd • Charm mixing is negligible in comparison both to the D0 decay rate and to mixing in the neutral K and B systems • scale of plots chosen to highlight differences E (10-10 MeV) dG/dE D0Mixing dG/dE DMs DMD ≈ O(10-14) Bs E (10-9 MeV) dG/dE DMK K0 E (10-9 MeV) E (10-12 MeV)

  19. V*ci Vui W c u d, s, b D0 D0 g d, s, b u c Vui V*ci W SM di-penguin diagram

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