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Evidence for a Near-Threshold Structure in the J/  from B +  J/ K + Decay at CDF

Evidence for a Near-Threshold Structure in the J/  from B +  J/ K + Decay at CDF. Jane Nachtman University of Iowa (for CDF Collaboration) Rencontres de Moriond QCD March 2009. A Little Background.

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Evidence for a Near-Threshold Structure in the J/  from B +  J/ K + Decay at CDF

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  1. Evidence for a Near-Threshold Structure in the J/ from B+J/K+ Decay at CDF Jane Nachtman University of Iowa (for CDF Collaboration) Rencontres de Moriond QCD March 2009

  2. A Little Background • In recent years, several interesting particles have been discovered Y(3940) M≈3940 ± 11 MeV  ≈ 92 ± 24 MeV X(3872)J/+- M=3871.8±0.7±0.4 MeV < 3.5 MeV @ 90% CL Y(4260) M=4259  8 MeV  = 88  23 MeV Unusual decays of these mesons lead to speculation of exotic mesons (hybrids, four-quark states

  3. Next place to look: J/ channel through B decays? • Hints of exotic mesons  look for “relatives” • J/ channel (threshold at 4.116 GeV, VV, C=+) is accessible to: • hybrid: 0-+, 1-+, 2-+ expected nearby Y(4260) (1--, m=4.26 GeV) • multi-quark states: X(3872)J/+// etc, Y(3940)J/+ (threshold) • glueball and other possibilities • Normal charmonium with mass above 4.116 GeV has tiny BF to this channel • Experimentally easy to search through clean BJ/K channel. vacuum polarization gluon coupling

  4. CDF II Why search at CDF? • B hadrons copiously produced at Tevatron • B hadrons boosted at Tevatron • smooth acceptance for potential structures • CDF has excellent mass/vertexresolution and hadron particle id (PID)

  5. Muon ID CDF detector Track momentum PID from dE/dx Kaon ID • Muon: muon ID • ToF: kaon PID from TOF • COT: track momentum • kaon PID from dEdx • Silicon: track momentum • vertex position Track momentum vertex position

  6. Tevatron Performance To tape 2.7 fb-1 Used for this result With excellent Tevatron performance, we certainly can expect more!!!

  7. + J/ - primary vertex secondary vertex Search? Lxy +  - B+ + Vertex separation Particle Identification (Kaon LLR) Analysis strategy • Reconstruct B+ as: • B+ J/ + • J/+- • +- • Search for structure in J/ mass spectrum inside B+ mass window Reconstruct control channels : ~3 000BsJ/, ~50 000B+J/K+ before Lxy and kaon LLR cuts

  8. Before Lxy>500 um, kaon LLR>0.2 After Lxy>500 um, kaon LLR>0.2 7510 ( in 3 B+ window ~80%pure Reconstructed B+J/K+ ~20% signal eff. x20K bkg reduction • Check inside B+ mass window for  with relaxed K+K- mass window, B+ sideband subtraction • A P-wave relativistic BW only good fit to data • 2 probability 28%, no f0K+K- or K+K- phase space components • We conclude that the signals in the B+ peak are pure B+J/K+

  9. Investigate J/ mass spectrum in MC • MC simulated in phase space  smooth Dalitz plot, no structure in mass M=m(+-K+K-)-m(+-) • Check for reflections –found (Bs(2S), (2S)J/ +-) B+J/K+ due to kaon mis-identification • Bs contamination at M>1.56 GeV, • cut it off for simplification

  10. Search for structures in J/mass--Data • An enhancement at threshold is observed M=m(+-K+K-)-m(+-) • We model the Signal (S) and Background (B) as: S: S-wave relativistic Breit-Wigner B: Three-body decay Phase Space • The fit returns: Yield =145 m = 1046.3 2.9 (stat) MeV/c2 • Width = 11.7 +8.3-5.0 (stat) MeVsqrt(-2log(Lmax/L0 ))=5.3 • Significance: it would be 5.3 if there were a priori predictions for mass and width BUT there were NOT!

  11. Significance study • We determine significance from simulation (Toy MC): • --Using Three-body decay Phase Space only to generate the m spectrum • --Find the most significant fluctuation in the Toy events for each trial anywherein m between 1.02 and 1.56 GeV, and with a width between 1.7 MeV (resolution) and 120 MeV (10 times of the observed width) • --count the number of times that a fluctuation with -2log(Lmax/L0 ) greater or equal to the value in the data and calculate a p-value • Significance: • the p-value obtained from simulation is 9.3X10-6, corresponding to 4.3 • drops from 5.3 to 4.3 (absence of a priori predictions for mass and width) • 3.8 using Phase Space and flat background for non-B background for cross-check

  12. Results See Kai Yi’s Wine and Cheese talk Tuesday at Fermilab (available on streaming video) • Including systematics: • Yield =145 • m = 1046.3 2.9 (stat) 1.2 (syst) MeV/c2 • Mass = 4143.0  2.9 (stat) 1.2 (syst) MeV/c2 (adding J/ mass) • Width = 11.7 +8.3-5.0 (stat) 3.7(syst) MeV • Significance: 4.3 • after taking absence of prediction of mass and width into account. • tentatively name it Y(4140) • Width indicates a strong decay

  13. Backup slides

  14. CLEO, PRL 84,1393 BaBar 2003, PRL 91, 071801 23 B+ 13 B0 J/ and ee, 10 B+ and B0 J/ and ee The current status • The current status through B J/ K: • statistically limited, no structures reported

  15. dEdx residual CDF Time-of-flight: Tevatron store 860-12/23/2001 1.5σ dE/dx parameterized using D*+(-)→D0π+(-) sample dE/dx efficiency ~100% Excellent resolution TOF acceptance+efficiency ~60% CDF hadron PID Make use both dEdx and ToF for hadron PID Summarizing dEdx and ToF into a log-likelihood ratio

  16. CDF Di-muon trigger Scale to ~2.7 fb-1, ~20M J/with silicon hits

  17. The challenge • Start with typical requirements for B hadron at CDF: • --p(2) for B+ vertex fit>1% • --pT(track)>0.4 GeV, • -- >=4 r- silicon hits • --pT(B+)>4 GeV • --mass window: • J/ (50 MeV) and  ( 7 MeV) • constrain +- toJ/ PDG mass value • NOT applied yet: Lxy and kaon PID B+ mass Typical hadron collider environment, help from Lxy and kaon PID?

  18. After Lxy>500 um, kaon LLR>0.2 7510 BaBar 2003, PRL 91, 071801 23 B+ 13 B0 J/ and ee The answer to challenge—Lxy and kaon PID • Justification on S/sqrt(S+B) of B+J/K+ Signal • Justified cuts: • Lxy>500 m, kaon LLR>0.2 • The largest B+J/K+ to date: • 7510 (CDF) define 3 as B+ signal region (17.7 MeV obtained from MC) Purity ~80% in the defined region

  19. What is it? Y(4140) • Well above open charm pair threshold • Expect tiny BF to J/ • Does not fit into charmonium • Close J/ threshold like Y(3940) • What is it? from Estia Eichten

  20. Backup 2 Not close from the PDF comparison although they both have C=+ X(4160)D*D*

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