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Charm Meson Decay Constants

Charm Meson Decay Constants. Sheldon Stone Syracuse University. or cs. (s). Leptonic Decays: D   + n. _. c and q can annihilate, probability is proportional to wave function overlap Standard Model decay diagram:. In general for all pseudoscalars:.

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Charm Meson Decay Constants

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  1. Charm Meson Decay Constants Sheldon Stone Syracuse University

  2. or cs (s) Leptonic Decays: D +n _ c and q can annihilate, probability is proportionalto wave function overlap Standard Model decay diagram: In general for all pseudoscalars: Calculate, or measure if VQq is known, here take Vcd =Vus= 0.2256, Vcs =Vud -Vcb/4= 0.9734 Interplay Meeting Dec. 16, 2009

  3. Experimental Considerations • In principle have access to 6 decays D+ e+, +, t+ DS+e+, +, t+ • Helicity suppression causes e+ mode to be highly suppressed • D t+ has at 2 neutrinos missing, so is more difficult to detect • Only B+ available, not Bo or BS & B is low Interplay Meeting Dec. 16, 2009

  4. Reasons to Measure • Lattice calculations needed for all sorts of heavy flavor parameters, e.g. =fB/fBs, B form-factors…fD & fDs/fD provide an experimental check • Possibilities to see effects of New Physics • Interference with H+. • Rate ratio is sensitive to neutrino couplings, e.g. a sterile neutrino coupling differently to nm & nt, or any model which doesn’t couple as m2, e.g. Leptoquarks Interplay Meeting Dec. 16, 2009

  5. CLEO’s Technique for D+m+n • Exploit e+e-D-D+ • Fully reconstruct a D-, and count total # of tags • Seek events with only one additional oppositely charged track within |cosq|<0.9 & no additional photons > 250 MeV (to veto D+p+po) • Charged track must deposit only minimum ionization in calorimeter [< 300 MeV: case (i)] • Compute MM2. If close to zero then almost certainly we have a m+n decay. We know ED+=Ebeam, pD+= - pD- Interplay Meeting Dec. 16, 2009

  6. Tags • Total of 460,000 • Background 89,400 Interplay Meeting Dec. 16,2009

  7. MM2 Signal Shapes Check with shape of Kop+ peak Monte Carlo Signal mn Monte Carlo Signal tn, t→pn Interplay Meeting Dec. 16,2009

  8. Fit MM2 to sum of signal & bkgrd • Case(i) E< 300 MeV where t+n/m+n is fixed to SM ratio • 149.712.0 mn • 28.5 tn • Case(i) E< 300 MeV where t+n/m+n is allowed to float • 153.913.5 mn • 13.515.3 tn Background cocktail Kop mn p+po tn, t→pn Interplay Meeting Dec. 16,2009

  9. Background Check • Use case(ii) E>300 MeV in EM calorimeter • Fix tn from case(i) mn. • Consider signal region |MM2|<0.05 GeV2. Expect 1.7 mn + 5.4 p+po + 4.0 tn = 11.1 • Find 11 events • Extra bkgrnd=-0.13.3 events Signal Region Interplay Meeting Dec. 16,2009

  10. Systematic Errors FPCP May, 2008

  11. Branching Fractions & fD+ • Fix tn/mn at SM ratio of 2.65 • B(D+m+n)= (3.820.320.09)x10-4 • fD+=(205.88.52.5) MeV • This is best number in context of SM • Float tn/mu • B(D+m+n)= (3.930.350.10)x10-4 • fD+=(207.69.32.5) MeV • This is best number for use with Non-SM models • These are final numbers with 818 pb-1 • This is the only measurement FPCP May, 2008

  12. Upper limits on tn & en • Here we fit both case(i) & case(ii) constraining the relative tn yield to the pion acceptance, 55/45. • Find • B(D+t+n) < 1.2x10-3, @ 90% c.l. • B(D+t+n)/2.65B(D+m+n) < 1.2 @ 90% c. l. • Also B(D+e+n)< 8.8x10-6, @ 90% c.l. case (i) E<300 MeV tn, t→pn case (ii) E> 300 MeV tn, t→pn Interplay Meeting Dec. 16, 2009

  13. Measurements of fDs Start with DS+ +

  14. Use e+e-→DSDS* at 4170 MeV • Reconstruct DS- • Find the g from the DS* & compute MM2 from DS- & g • Select combinations consistent with a missing DS+ & count the number • Find MM2 from candidate muon for (i) < 300 MeV in Ecal, (ii) E>300 MeV or (iii) e- cand. Interplay Meeting Dec. 16,2009

  15. DS- Tags: Invariant Mass hp- K+K-p- KSK- h'p- h'→p-p+ h K+K-p-po p-p-p+ K*oK*- hr- h'p- h'→rg FPCP May, 2008

  16. MM*2 Distributions From DS- + g K+K-p- hp- KSK- Multi g bkgrnd Sideband bkgrnd h'p- h'→p-p+ h p-p-p+ K+K-p-po h'p- h'→rg hr- K*oK*- Interplay Meeting Dec. 16,2009

  17. MM2 data for DS • Total of 30848±695 tags • 99% of m+n in E < 300 MeV • 55%/45% split of t+n, t+→p+n in two cases • Small e- background case (i) Kop, hp region case (ii) Interplay Meeting Dec. 16,2009

  18. Fit to signal & background Case (i) + Case(ii) m+n Background DS sidebands tn, t Extra g background FPCP May, 2008

  19. Systematic Errors Interplay Meeting Dec. 16,2009

  20. DS+t+, t+r+ • Because of the two neutrinos, the signal does not peak in MM2, but the most important backgrounds do • Consider the extra energy, Eextra, deposited in the Calorimeter unmatched to the DS- tag or the p+po from the r+ decay. In principle, for real t+ decays Eextra =0. In fact some small fraction of real decays will have Eextra > 0 due to interactions in the detector, & some fraction of the background will have Eextra ~ 0 due to missed energy or false matching. Interplay Meeting Dec. 16, 2009

  21. Analysis Strategy • Signal and MC predicted backgrounds • Measure the B of the 3 indicated peaking modes. Use same set of DS- tags. Find: MM2 (Eextra < 0.1 GeV) Eextra K0pp0&hr+ pp0p0 Signal Real Ds Bkg Interplay Meeting Dec. 16, 2009

  22. Analysis Strategy II • We will fit the simultaneous the invariant tag mass & the MM2 distributions, separately in three Eextra intervals, <0.1 GeV where signal dominates, (0.1, 0.2) GeV where S & B are equivalent, and >0.8 GeV for checking of understanding background, where signal is absent. • In the fits, we put Gaussian constraints on the bkgrnd yields using known branching fractions and their errors. For the remaining sum of small modes we use the MC estimated rate with a rather large error. Thus the uncertainties in the background will be taken care of in the statistical error. Interplay Meeting Dec. 16, 2009

  23. hr+ K0pp0 Sideband background Other background with shape fixed to MC pp0p0, hp, wpp0, fp, h'p, h'pp0 Fit to Eextra > 0.8 GeV • No signal, fit consistent with bkgrnd expectations Points are data blue curve is overall fit Interplay Meeting Dec. 16, 2009

  24. Signal Region I: Eextra<0.1 GeV signal hr+ K0pp0 Sideband background Other backgrounds pp0p0, hp, fp, t(3pn)n, mn, Xmn Interplay Meeting Dec. 16, 2009

  25. Signal Region II: 0.2<Eextra<0.1 GeV signal hr+ K0pp0 Sideband background Other background pp0p0, hp, fp, t(3pn)n, mn, Xmn Interplay Meeting Dec. 16, 2009

  26. Branching Fraction • Sum of the above two • fDs=257.8±13.3±5.2 MeV

  27. set 1.22+1.62 = 2.0% error Systematic Errors • Measure efficiency of Eextra cut. Use fully reconstructed DsDs* events • Value at 300 MeV is chosen, because it has the same efficiency as r+n for Eextra 200 MeV Interplay Meeting Dec. 16, 2009

  28. Summary of Systematic Errors

  29. CLEO: DS+→t+n, t+→e+nn • B(DS+→t+n)B(t+→e+nn)~1.3%is “large” compared with expected B (DS+→Xe+n)~8% • We will be searching for events opposite a tag with one electron and not much other energy • Opt to use only a subset of the cleanest tags Interplay Meeting, Dec. 16, 2009

  30. Measuring DS+→t+n, t+→e+nn • Technique is to find • events with an e+ opposite DS- tags & no other tracks, with  calorimeter energy < 400 MeV • No need to find g from DS* • B(DS+→t+n) • =(5.30±0.47±0.22)% • fDs=252.5±11.1±5.2 MeV Largest source of systematic error 400 MeV Interplay Meeting Dec. 16,2009

  31. Results • B(Ds++) from CLEO • For New Physics searches important to separate + and m+ [See A.G. Akeroyd and F. Mahmoudi, JHEP 0904, 121(2009)] • Recall for m+ fDs =(257.6±10.3±4.3) MeV • Ratio fDs (t+)/fDs (m+) = (1.01  0.05) consistent with unity Interplay Meeting Dec. 16, 2009

  32. Belle: DS+→m+n • Look for e+e-DKXg(DS), where X=np & the DS is not observed but inferred from calculating the MM • Then add a candidate m+ and compute MM2 • B(DS+  +) = (0.6440.0760.057)% • fDs=275±16±12 MeV arXiv:0709.1340v2 [hep-ex] Interplay Meeting Dec. 16, 2009

  33. Results II Interplay Meeting Dec. 16, 2009 • Average of All CLEO measurements: fDs =(259.0±6.2±3.0) MeV • Plus Belle (275±16±12) MeV gives fDs =(260.7±6.5) MeV • Follana et. al (241±3) MeV, difference 2.4s • A. Bazavov et al. [Fermilab Lattice and MILC Collaborations], PoS LATTICE 2009 (2009) 249 now claim fDs =(260±10) MeV • Is discrepancy due to faulty calculation, or new physics?

  34. Other Non-absolute Measurements Exp. mode BB(DSfp) fDs (MeV) (%) HFAG reinterpretation: 237  13  5 See Rosner & Stone, arXiv:0802.1043 for references Interplay Meeting Dec. 16, 2009

  35. Beyond the SM Theories • Leptoquark models & special Two-Higgs doublet model (Dobrescu & Kronfeld) [arXiv:0803.0512-hep-ph] • R-parity violating Supersymmetry (Akeroyd & Recksiegel [hep-ph/0210376]) • A. Kundu & S. Nandi, “R-parity violating supersymmetry, BS mixing, & DS+  +”[arXiv:0803.1898]) • Bhattacharyya, Chatterjee & Nandi [arXiv:0911.3811v1-hep-ph] • Dosner et al show that the above models should effect tn and mn differently [arXiv:0906.5585-hep/ph] • Gninenko & Gorbunov argue that the neutrino in the Ds decay mixes with a sterile neutrino, which enhances the rate, but should act the same in D+ & DS, & could be different for + & t+[arXiv:0907.4666-hep-ph] Interplay Meeting Dec. 16, 2009

  36. Conclusions • We are in close agreement with the Follana et al calculation for fD+. This gives credence to their methods, but here is a disagreement with fDs at the 2.4s level Absolute B measurements only Interplay Meeting Dec. 16, 2009

  37. Conclusions II • Although the calculations are somewhat different for fBs/fB, if theoretical predictions of fDs/fD+ do not agree with the data, why should we believe fBs/fB from theory? What does this do to the CKM fits? (This statement assumes that NP is not present!) • Perhaps new lattice calculations using somewhat different methods will help resolve this situation, along with new data from BES III Interplay Meeting Dec. 16, 2009

  38. The End

  39. Efficiencies • Tracking, particle id, E<300 MeV (determined from m-pairs) = 85.3% • Not having an unmatched shower > 250 MeV 95.9%, determined from double tag, tag samples • Easier to find a mn event in a tag then a generic decay (tag bias) (1.53%) Interplay Meeting Dec. 16, 2009

  40. mn Signal Shape Checked • Data s=0.02470.0012 GeV2 • MC s=0.02350.0007 GeV2 • Both average of double Gaussians Kop+ data Kop+ MC Interplay Meeting Dec. 16, 2009

  41. Fixed 149.712.0 mu 28.5 tn Floating 153.913.5 mu 13.515.3 tn Case(i) With t+n/m+n Floating Interplay Meeting Dec. 16, 2009

  42. New Physics Possibilities III • Leptonic decay rate is modified by H± • Can calculate in SUSY as function of mq/mc, • In 2HDM predicted decay width is x by • Corrected • Since md is ~0, effect can be seen only in DS See Akeryod [hep-ph/0308260] = meas rate/SM rate From Akeroyd tan b/MH Interplay Meeting Dec. 16, 2009

  43. Model of Kop+ Tail Kp • Use double tag Do Do events, where both Do→Kp • Make loose cuts on 2nd Do so as not to bias distribution: require only 4 charged tracks in the event Kppo Expectation from residual p+p-(1.1 events) Computed ignoring charged kaon Gives an excellent description of shape of low mass tail “Extra” 1.3 event background in signal region Interplay Meeting Dec. 16,2009

  44. The MM2 Distribution • For E< 300 MeV in CsI Kop+ peak m+n peak t+n, t+→p+n region Interplay Meeting Dec. 16,2009

  45. Residual Backgrounds for mu • Monte Carlo of Continuum, Do, radiative return and other D+ modes, in mn signal region • This we subtract off the fitted yields Interplay Meeting Dec. 16,2009

  46. CP Violation • D+ tags 228,945551 • D- tags 231,107552 • m-n events 64.88.1 • m+n events 76.08.6 • -0.05<ACP<0.21 @ 90% c. l. Interplay Meeting Dec. 16, 2009

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