1 / 43

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.

clint
Download Presentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

More Related