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 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

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

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

CDF detector Muon ID 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

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

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

Reconstructed B+J/K+ Before Lxy>500 um, kaon LLR>0.2 7510 ( in 3 B+ window ~80%pure After Lxy>500 um, kaon LLR>0.2 ~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+

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

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) MeV sqrt(-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!

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 anywhere in 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

Results Yield =145 m = 1046.3 2.9 (stat) 1.2 (syst) MeV/c2 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

Backup slides

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

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

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

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 +- to J/ PDG mass value NOT applied yet: Lxy and kaon PID B+ mass Typical hadron collider environment, help from Lxy and kaon PID?

The answer to challenge—Lxy and kaon PID After Lxy>500 um, kaon LLR>0.2 7510 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) BaBar 2003, PRL 91, 071801 23 B+ 13 B0 J/ and ee define 3 as B+ signal region (17.7 MeV obtained from MC) Purity ~80% in the defined region

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

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