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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. Kai Yi University of Iowa (for CDF Collaboration) Fermilab, March 17, 2009 .  - discovery J/  (cc) discovery  (bb) discovery. History—from strange to bottom discovery.

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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 Kai Yi University of Iowa (for CDF Collaboration) Fermilab, March 17, 2009

  2.  -discoveryJ/ (cc) discovery  (bb) discovery History—from strange to bottom discovery BNL SLAC FNAL BNL BNL • 1964 1968 1974 1974 1977 • Heavy flavor spectroscopy helped turn quarks into a reality! • B+J/K+ decay includes b,c,s,u quarks

  3. b u d c c Quark Model • Six quarks exist in Standard Model • charm/bottom/top called heavy • no free quarks, they have to be bound • top so heavy, it decays before forming bound states • Baryons are bound states of three quarks • Mesons are bound states of quark and anti-quark • quarkonia: quark and its own antiquark • Quark model works pretty well • Challenged by newly discovered charmonium-like states

  4. PRL 91, 262001 X(3872)--2003 CC X(3872)J/+- M=3871.8±0.7±0.4 MeV < 3.5 MeV @ 90% CL mass ~70 MeV > predictions (2003) +- peak at high value like a ρ (2003) ?? JPC = 1++ or 2-+

  5. Y(3940)J/, Y(4260)J+---2005 PRL 94, 182002 PRL 95, 142001 Y(4260)J/+- M≈4259±8 MeV ≈88 23 MeV Y(3940)J/ω M≈3940±11 MeV ≈92±24 MeV Above DD && DD* threshold, tiny Branching Fraction expected New mass and width from BaBar: M 3914+3.8-3.42.0,  34+12-8 5 MeV at the J/ threshold ? Well above DD && DD* threshold, tiny Branching Fraction expected JPC=1--, plus Y(4350), Y(4660) too many 1-- ?

  6. Z(4430)+(2S)+--2008 PRL 100, 142001 Z(4430)+(2S)+ M≈4433±4 MeV ≈44 ±17 MeV Needs confirmation The first charged charmonium-like new state, if confirmed Many more new states… They do not (easily) fit into charmonium Beyond (qq) mesons: exotic mesons?

  7. c u u c g g c g c Exotic Mesons—QCD predictions • Multi-quark mesons • molecule, diquark-antidiquark • Hybrid mesons • quark-antiquark-gluon • Glueball • gluonic color singlet states • Explore more channels to understand • How about J/ψϕ? (threshold @4.116 GeV, VV, C=+) • (cc) with a mass above 4.116 GeV, expect tiny branching fraction

  8. Charmonium hybridJ/ψϕ ? PRD 57, 5653 (1998) F. Close et al accessible J/ψϕis also accessible to 0-+, 2-+ (0-+ ,1-+ ,2-+) masses are expected near Y(4260), E. Eichten

  9. Multi-quark statesJ/ψϕ ? arXiv:0902.2803 (new) N. V. Drenska et al J/ψϕis well motivated! How to search? Inclusive? Challenge! Through B decays!

  10. Experimentally easy to search through clean BJ/K channel • -- taking advantage of B lifetime and narrow B mass window • -- BJ/ψϕK is OZI suppressed, so low physics background Search structuresJ/ through B decays PRL 84,1393 PRL 91, 071801 vacuum polarization gluon coupling

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

  12. Why search at CDF? • B hadrons at Tevatron are: • copiously produced • boosted • --vertex separation • --boost low pT daughters • CDF has: • excellent mass resolution • excellent vertexresolution • reasonable hadron PID • CDF detector mass

  13. CDF detector • Muon: μ ID • ToF: TOF • COT: track p • dEdx • Silicon: track p • vertex

  14. CDF Di-muon trigger pT > 1.5 GeV both muons Scale to ~2.7 fb-1, ~20M J/with silicon hits used for this analysis

  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 Time-of-Flight acceptance+efficiency ~60% CDF hadron PID Main background: prompt pions, need PID to suppress TOF mass Make use of both dEdx and ToF for hadron PID summarizing dEdx and ToF into a log-likelihood ratio

  16. CDF hadron PID K-π separation 3.0σ 1.5σ Typical B decay daughter momentum ~GeV

  17. + J/ - primary vertex secondary vertex Search? Lxy +  - B+ + Vertex separation Particle Identification • I) Reconstruct B+ as: • B+ J/ + • J/+- • +- • II) Search for structure in J/ mass spectrum inside B+ mass window Analysis strategy

  18. I) Reconstruct B+J/K+

  19. 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

  20. Applying Lxy • Maximize S/√(S+B) for B+J/K+ signal, has nothing to do with J/ • Maximized cuts: Lxy>500 m, kaon LLR>0.2 +Lxy>500 um B+ mass Lxy Reduce background by a factor of ~200

  21. Applying Lxy and kaon PID Gaussian function mean fixed to PDG rms fixed to resolution (5.9 MeV) 7510 define 3 as B+ signal region (17.7 MeV obtained from MC) Purity ~80% in B+ region Kaon PID reduce background by a factor of ~100 clear B+J/K+ signal

  22. Control channels • We also reconstruct two control channels with similar cuts: • ~3 000BsJ/, ~50 000B+J/K+ • before Lxy and kaon LLR cuts • Clean control signals after Lxy and kaon LLR cuts • cross check and efficiency evaluation BsJ/ ~ 800 events B+J/K+ ~21k events

  23. Before Lxy>500 um, kaon LLR>0.2 After Lxy>500 um, kaon LLR>0.2 Background reduction factor Reduce background by a factor of 20 000 by using Lxy and kaon PID cuts while keeping about 20% of signal as estimated by control channels. Any background under ?

  24. Verify B+J/K+ • Investigate components of B+ peak • --relax K+K- mass window to: • [1.0,1.04] MeV • --do B+ sideband subtraction for K+K- • --fit to sideband subtracted K+K- mass • A P-wave relativistic BW only fit to • data with 2 probability 28%, no • f0K+K- or K+K- phase space • components with our ϕ mass window • Conclusion • pure B+J/K+ for B+ peak • negligible B+J/f0K+, J/K+K-K+ components

  25. II) Search for structures in J/ψϕ spectrum from B

  26. Monte Carlo

  27. InvestigateJ/mass spectrum in MC • MC simulated phase space, full detector simulation M=m(+-K+K-)-m(+-) • MC events smoothly distributed in Dalitz plot • No artifacts in the J/ mass spectrum • How about reflections from other B hadrons?

  28. InvestigateJ/mass spectrum in MC • We simulate generic B hadron decays with a J/ in the final state and • we identified a contamination channel: Bs(2S), (2S)J/+- (Bs(2S), (2S)J/ +-) B+J/K+ due to kaon mis-identification • Bs contamination at M>1.56 GeV, • cut it off for simplification 20 times Luminosity of data

  29. Data

  30. Search for structures in J/mass--Data M=m(+-K+K-)-m(+-) Three-body Phase Space Background shape is different from data An near threshold enhancement is observed

  31. Robustness test Lxy>100m Default cuts M=m(+-K+K-)-m(+-) p(vertex-2)>10-5 SVX hits3 • Extensive cross checks by varying • Lxy, kaon PID LLR, B+ mass window, • vertex probability, # of silicon hits,… • Robust against variations • More signal but with more background

  32. Search for structures in J/mass--Data • We model the Signal (S) and Background (B) as: • S: S-wave relativistic Breit-Wigner B: Three-body decay Phase Space Yield =145 m = 1046.3 2.9 (stat) MeV/c2 Width = 11.7 +8.3-5.0 (stat) MeV Convoluted with resolution (1.7 MeV) M=m(+-K+K-)-m(+-) √(-2log(Lmax/L0 ))=5.3, need Toy MC to determine significance for low statistics

  33. 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 for each trial • anywherein m between 1.02 and 1.56 GeV • width between 1.7 MeV (resolution) and 120 MeV (10X observed width) • --Count it if -2log(Lmax/L0 ) (-2Δln) ≥ -2Δln value in data P-value: 9.3X10-6 (3.1 million total trials) corresponding to 4.3 -2Δln

  34. Cross check: • --fit -2Δln distribution with 2 Probability Density Function to get n (d.o.f): • --calculate p value using 2 PDF as cross check Significance study P-value by integrating 2 PDF: 6.5X10-6, corresponding to 4.3, consistent with counting Best estimation of significance More conservative -2Δln • Most conservative: Phase Space and flat background for non-B background, 3.8

  35. Results • 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/ψ mass) • Width = 11.7 +8.3-5.0 (stat) 3.7(syst) MeV • Significance: at least 3.8σ for most unphysical conservative background • Width indicates a strong decay • tentatively name it as Y(4140)

  36. What is it? Y(4140) • Well above • charm pair threshold • Expect tinyBF to J/ • Does not • fit into charmonium • Close J/ threshold • like Y(3940) • arXiv:0903.2529[hep-ph] • molecular?

  37. Opportunities • Determine JPC (c=+)? Need statistics • --increase efficiency, reduce background • --add more data, 5σ • --investigate efficiencies against angles? • … • More channels for this structure? • --open charm pair? • Note: Search for potential more structures? • B+(2S)K+, B+K+, BsJ/ • (nS), …

  38. Summary Mass = 4143.0  2.9 (stat) 1.2 (syst) MeV/c2 Width = 11.7 +8.3-5.0 (stat) 3.7(syst) MeV JPC=??+ tentatively name it as Y(4140) CDF Stay tuned!

  39. J/ee ~ 400 fb-1 mee 220 fb-1 m Backup 1 J/ee is difficult but not impossible Trigger is gone 

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

  41. Backup 3 M=m(+-K+K-)-m(+-)

  42. Tevatron

  43. Exotic JPC • For qq meson system, let L to be the orbital angular momentum. • The meson spin J is given by |L-S|<J<|L+S|, • where S=0 (antiparallel quark spin) or 1 (parallel quark spin) • The parity P and charge parity C of the meson system can be expressed as: • P=(-1)L+1 • C=(-1)L+S • In the configuration of P=(-1)J, S=1, CP=+1,  • Exotic JPC (not allowed for qq meson): • 0--, 0+-,1-+,2+-,… • But exotic mesons can have these JPC due to additional degree of freedom. • Identify exotic JPC is helpful to identify exotic mesons

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