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The Search for D mesons Oscillations

The Search for D mesons Oscillations. IX Roma Tre Topical Seminar on Subnuclear Physics Will Johns, Vanderbilt University Dec. 4, 2006. Briefly, what is the condition?.

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The Search for D mesons Oscillations

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  1. The Search for D mesons Oscillations IX Roma Tre Topical Seminar on Subnuclear Physics Will Johns, Vanderbilt University Dec. 4, 2006

  2. Briefly, what is the condition? • Neutral Charm Meson Mixing in the Standard Model (SM) “probably” has a short range lower limit (using y from: hep-ph/0506185) • While the long range upper limit for SM comes from experiment: (i.e. Difficult to calculate!) • So, a clear mixing signal by itself, at least in all the modes studied to date, is not a clear indication of the underlying physics, how the mixing occurs will be important. (A few years maybe a puzzle why we don’t see mixing!)

  3. Charm Mixing 101 Assume a mass eigenstate of the Hamiltonian exists for a mixed state: Time evolve in terms of mass eigenstates: Take leading order for small y,x: cosh()~1, sinh()~y+ix

  4. And the decay rate to a final state f: (“CF” for D0 “DCS” for D0) Charm Mixing 101 contd. Interference Direct Mixing (Anti-particle flips q/p and changes sign of f)

  5. Charm Mixing 101 contd. • Particular advantages to choosing this: • For small mixing, CP violation, strong phase: interference term boosts signal • Examining “DCS”(t) mode helps bring out lifetime dependence (otherwise move RDCS to “Mixing” term and interference is swamped) Interference Direct Mixing

  6. Time evolution of a mixed DCS state (Thesis: Jonathan Link)

  7. Charm Mixing 101 contd. And the decay rate to a final state f: (f is a CP eigenstate like K+K-) Notice the sign change Idea in practice is simpler: It’s like you get one of the D1,D2

  8. Charm Mixing 101 contd. And by measuring lifetime differences, you can measure y (called yCP): Also, several types of CP violation to look at here. -And, if you were looking closely, there is a type of CP violation that can occur only through the mixing. A difference in rates when |q/p|=1 can be due to the CP violating phase. Some authors claim this is the only pure way to see New Physics! &

  9. Easiest to interpret: Semileptonic Assume CP ok, q/p=1 No DCSD! Since Use D* to TAG the flavor: Result can be described as a circle in y’ vs x’ y’ x’ Count decays and get relative rates:

  10. Semileptonic Results from Belle Right Sign PRD 72, 071101 (2005) Form: v info comes from direction, Ebeam – Eparticles, Mv=0 Max L fit to signal and background Shapes from MC for Yield Fit Mass Diff in bins of lifetime Wrong Sign (RM) Dashed line is 90% CL upper limit

  11. Semileptonic Results (PDG06) (Both of these from David Asner Reviews:PDG06, HQL06, Beauty 2006) • E.M. Aitala et al. (E791), PRL 77, 2384 (1996): 2504 RS events • C. Cawlfield et al. (CLEO II), PRD 71, 077101 (2005): (9 fb-1) 638 RS events • B. Aubert et al. (BABAR), PRD 70, 091102 (2004): (87 fb-1) 49620 RS events • U. Bitenc et al. (Belle), PRD 72, 071101 (2005): (253 fb-1) 229452 RS events (FOCUS result in PDG is unpublished Thesis)

  12. Another Method Almost as Easy Use And discard all except RD (~ = Quantities integrated over phase space) Only after this! (Mode Independent) Also, if DCSD Dalitz way different from CF, can try to cut DCSD. Idea: CF mixed signal has same Dalitz shape as unmixed CF -Sort of like getting rid of Background

  13. Multi-Body decays from BABAR Right Sign Wrong Sign Wrong Sign • - Cut out K* region • Use D* tag trick again • Fit to M(D*-D), M(D) then lifetime • WS shapes in fit from RS • Fit with and without assuming CP Signal Soft pion mistag D misreconstructed Combinatorial hep-ex/0608006

  14. Multi-Body decays from BABAR Assuming CP conservation Assuming No CP Conservation

  15. Multi-Body decays from BABAR Use hep-ex/0607090 • Background smaller • No Dalitz Cut Wrong Sign

  16. Combined BABAR Multibody PDG06 Compilation (D. Asner) (total rate) Beauty2006 06 Compilation (D. Asner) • E.M. Aitala et al. (E791), PRD 57, 13 (1998) 7 WS K+3 • G. Brandenburg et al. (CLEO), PRL 87, 071802 (2001) (9 1/fb) 38 WS K+-0 • S. Dytman et al. (CLEO), PRD 64, 111101 (2001) (9 1/fb) 54 WS K+3 • X.C. Tian et al. (Belle), PRL 95, 231801 (2005): (281 1/fb) 1978 WS K+-0 1721 WS K+3 • B. Aubert et al. (BABAR), to PRL, hep-ex/0608006:(230 1/fb) 1560 WS K+-0 • B. Aubert et al. (BABAR), hep-ex/0607090: (230 1/fb) 2002 WSK+3

  17. CP EigenstatesFrom BABAR PRL 91, 121801 (2003) • Using D* tag allows CP Asymmetry test • Can also measure event without a tag • Tag signal cut on mass difference (CLEAN!) • Use D mass fit for (unbinned ML) lifetime fit • ProbD(Mass), ProbBk(Mass) y Recall x

  18. 2-body CP Eigenstate Summary PDG06 (D. Asner) Beauty 2006 Compilation (D. Asner) Experiment untagged events tagged events <> E791, PRL 83, 32 (1999) 3200 FOCUS, PLB 485, 62 (2000) * 16532 <40 fs CLEO, PRD 65, 092001 (2002) 4159 170 fs Belle, PRL 88, 162001 (2002) 18306 215 fs BABAR, PRL 91, 121801 (2003) 145826 38933 160 fs Belle, Lepton Photon 2004 36480 180 fs

  19. DCSD 2 Body from Belle PRL 96, 151801 (2006) -D* tag -Cut on Q(D*-D-pion), M(D) -Fit M(D) sidebands for BKGND (t) -Signal/Bkgnd shapes from MC & Data -Psig, Pbkgnd Fractions -Final fit, only RD x’2 y’2 float

  20. DCSD 2 Body Summary PDG06 • R. Godang et al. (CLEO), PRL 84, 5038 (2000): (9 1/fb) 45 WS events • J.M. Link et al. (FOCUS), PRL 86, 2955 (2001): 234 WS events • PLB 618, 23 (2005) • B. Aubert et al. (BABAR), PRL 91, 171801 (2003) (57.1 1/fb) 430 WS events • J. Li et al. (Belle), PRL 94, 071801 (2005) (90 1/fb) 845 WS events • L.M. Zhang et al. (Belle), PRL 96, 151801 (2006) (400 1/fb) 4024 WS events More than one solution for x’,y’ Beauty 2006 (D. Asner)

  21. Multi-Body Decays from CLEO PRD 72, 012001 (2005) Multibody decays may have even and odd eigenstates of CP along with mixed modes. Will project them out in a rate calculation. Mixed(or flavor) and CP- Mixed(or flavor) and CP+ End up with a sum of complex amplitudes with relative(fittable) phases between states For small y, linear in y! For x, has sensitivity to sign of x Fit in time leaves overall constant unimportant for x,y

  22. Multi-Body Decays from CLEO • Tag flavor with D* • Use cuts, fit to fixed quasi 2-body shapes • from previous Dalitz analysis Note: Need more events, very nice!

  23. Mixing Summary (D.Asner HQL 2006) BaBar K0 +K3 Need precision cos measurement (CLEO-c) So that all limits can be expressed in x vs y Full time-dependent Dalitz plot of D0KS+- from Belle (in progress) & BaBar would be a nice addition. Expect twice the sensitivity per Luminosity as BELLE (K) or BaBar (K0+K3)

  24. Updated Theoretical Estimatesfrom A. Petrov (hep-ph/0311371) y predictions x predictions -x and y can be naturally large ~% in SM if phase space ruins cancellations. e.g. ~0.001 not so good for Hi M*… -x related to y via dispersion relationship – big y bleeds into x From hep-ph/0110317 From hep-ph/0611361 (could be large) From hep-ph/0610039 Can also have NP effects in y ~1%

  25. Updated Theoretical Estimatesfrom A. Petrov (hep-ph/0311371) y predictions x predictions y=(0.7 +/- 0.5)% (PDG06) (avg of yCP and y {no y’})

  26. Future • Creating D’s in a coherent state allows one to virtually pick and choose which mixing parameter to study • Good way to study effects • Example Kp Kp produced mode can only have mixing effect • At present there is not enough rate from e+e- to dominate measurements (expect competitive measurements from CLEO-c early next year) • BEDIII, Super B • Otherwise keep getting more stats and maybe wait for LHC(B).

  27. Correlate D production physics parameters from Beauty 2006 (D.Asner) Semilep Hadron

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