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Observation of Y(3940)→J/ ψω in B→J/ ψω K at B A B A R

Observation of Y(3940)→J/ ψω in B→J/ ψω K at B A B A R. Arafat Gabareen Mokhtar Colorado State University. SLAC seminar Aug/9/2007. Outline Introduction & Motivation B A B A R observation of Y(3940) Summary.

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Observation of Y(3940)→J/ ψω in B→J/ ψω K at B A B A R

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  1. Observation of Y(3940)→J/ψω in B→J/ψωK at BABAR Arafat Gabareen Mokhtar Colorado State University SLAC seminar Aug/9/2007 • Outline • Introduction & Motivation • BABAR observation of Y(3940) • Summary “there are quarkonia that we know we know; there are quarkonia that we know we don’t know; and then there are quarkonia that we don’t know that we don’t know ” Sounds familiar? 

  2. B Substitutedenergy e- (9 GeV) e+ (3.1 GeV) Y(4S) Kinematics Center of mass energy A. Gabareen Mokhtar

  3. Charmonium production • Color-suppressed b→c decay • Predominantly from B-meson decays • e+e- Initial State Radiation (ISR) • e+e- collision below nominal c.m. energy • JPC=1- - • Double charmonium production • Typically one J/ψ or ψ, plus second cc state • Two-photon production • Access to C=+1 states • pp annihilation (Tevatron) • All quantum numbers available A. Gabareen Mokhtar

  4. E. Eichten et al. arXiv:hep-ph/0701208 Quantum numbers Charmonium spectroscopy We know we don’t know We don’t know we don’t know We know we know A. Gabareen Mokhtar

  5. Latest observations • X(3872)seen in B→XK, X→J/ψπ+π- (dominant decay mode: D0D*0) (Belle,BABAR,CDF,D0), J/ψγ, J/ψπ+π-π0? Belle: PRL91, 262001 (2003) BABARPRD73, 011101 (2006) CDFPRL93, 072001 (2004) (hadronic production) D0PRL93, 162002 (2004) (hadronic production) Belle: arXiv:hep-ex/0505037 (Preliminary) EPS 2007 • Z(3930) seen in γγ→Z, Z→DD Belle: PRL96, 082003 (2006) • X(3940) seen in the e+e-→J/ψ + X(recoil) Belle: PRL98, 082001 (2007) • Y(4260) seen in ISR, e+e-→e+e-Y,Y→J/ψπ+π- (BABAR,CLEO, Belle) BABAR: PRL 95, 142001 (2005) CLEO: PRD74, 091104 (2006) Belle: arXiv:hep-ex/0612006 A. Gabareen Mokhtar

  6. No m(Kω) cut m(Kω)>1.6 GeV M(3π)Є [0.760,0.805] GeV m2J/ψω (GeV2/c4) m2Kω (GeV2/c4) Y(3940): Belle observation (L=253fb-1) • First observation of Y(3940) from Belle: PRL 94, 182002 (2005) • M(Y) = 3943±11(stat)±13(syst) MeV/c2 & Γ(Y)=87±22(stat)±26(syst) MeV • BR(B→KY(3940))BR(Y(3940) →J/ψω) =(7.1±1.3(stat)±3.1(syst))x10-5 A. Gabareen Mokhtar

  7. Conventional charmonium cc state? • Hybrid cc+gluons? • - Lowest state 1- + (forbidden for quarkonium) • - Dominant decay H→DD** • But…. Lattice QCD predicts higher masses • Molecule? (Torn Qvist, Eric Swanson) • Smaller number of states but still small widths also above the threshold • In this model, isospin can be violated • Four-quark state? qqqq (Maiani) • - Many quasi-degenerate states are predicted (several states have same mass) • - Small widths also above threshold Theoretical models A. Gabareen Mokhtar

  8. The BABAR detector • PEP-II : electron-positron collider at C.M. energy of 10.58 GeV • peak Luminosity: • 1.21*1034cm-2s-2 • Integrated Luminosity: • (10/1999-07/2007) 447fb-1 • Excellent track reconstruction capability (SVT & DCH) • Precision vertexing (SVT driven) • Particle identification (dE/dx) (DIRC, EMC, IFR) A. Gabareen Mokhtar

  9. BABAR search for Y(3940) • Data sample: • 348 fb-1 equivalent to 383 million BB events • Signal MC: • B→YK( Y → J/ψω) (neutral & charged mode) with different generated masses and width values (M(Y)=3915,3925,3930, & 3940 MeV/c2) (Γ(Y)=0,20,30,60,&120 MeV) • B →X(3872)K( X →J/ψω) (neutral & charged mode) (zero width) • Generic MC: • B± → J/ψX • B0 → J/ψX • e+e- →qq → J/ψX (q=u,d,s) • e+e- →cc → J/ψX A. Gabareen Mokhtar

  10. ℓ+ B±→YK± , Y→J/ψω , J/ψ→ℓ+ℓ- (ℓ=e,μ) , ω→π+π-π0 , π0→γγ ℓ- J/ψ π+ π- ω Y γ π0 K+ B+ γ e- (9 GeV) e+ (3.1 GeV) Y(4S) B- ℓ+ B0→YKs , Y→J/ψω , Ks→π+π- J/ψ→ℓ+ℓ- (ℓ=e,μ) , ω→π+π-π0 , π0→γγ π+ ℓ- J/ψ π+ π- π- ω K0S Y γ K0 π0 B0 γ e- (9 GeV) e+ (3.1 GeV) Y(4S) B0 Event reconstruction A. Gabareen Mokhtar

  11. Selection criteria A. Gabareen Mokhtar

  12. π+ ω π0 π- The ω decay angular distribution Wrong π0 can lead to a wrong ω ….. ωhelicity angle (θh): the angle between π0 and π+ in the π+π- center of mass. Dalitz plot helicity cosine distribution: • The sin2θh dependence is not sensitive whether the di-pion form factor corresponds to a ρ Breit-Wigner lineshape or simply a constant (This is not true for eg. φ(1020)→π+π-π0 decay) • http://www.slac.stanford.edu/~wmd/omega_decay/isoscalar_vector_to_3pi.note Generated level A. Gabareen Mokhtar

  13. Background const Signal  sin2θh Truth-matched Truth-matched Non-Truth-matched Non-Truth-matched The ω decay angular distribution Cos(θh) dist.(3π) = dist(ω)+dist(bkg) Since then Each event has a weight of -√10P2 A. Gabareen Mokhtar

  14. Testing the method on signal MC Signal MC • The weighting procedure projects the entire signal • Reduces the background (combinatorial) • The weighting method is equivalent to the truth matching requirement A. Gabareen Mokhtar

  15. Comments on the weighting method • Number of events is given by N=Σwi • Uncertainty  ΔN=√Σwi2 • With P2 weighting <wi> > 1  statistical uncertainty is increased • Weighting method works best in samples with large statistics • We use the weighting method to confirm our findings with the un-weighted samples and so establish the correlation between the ω and B signals A. Gabareen Mokhtar

  16. Raw m 3π B0 B± -√10 P2Weighted m 3π B0 B± Fitting the ω signal Resolution B0 B± mωrec- mωgen (GeV/c2) • The resolution is fitted with three Gaussians (Not with the same center) • The resolution is about 15 MeV (full width at half max.) • The 3π is fitted with ω Breit-Wigner (PDG2006 values for mass and width) convolved with the resolution function and a second order polynomial for the background The helicity weighting procedure projects the number of signal events but with bigger statistical error A. Gabareen Mokhtar

  17. mES side-band ΔE side-band ΔE low side-band ΔE high side-band mES side-band MC data Data-MC B background comparison • No signals observed in the side-bands • In general, the generic MC reproduce the data in the side-bands • Similar results obtained for B0 samples (backup slides) A. Gabareen Mokhtar

  18. ω – mES signal correlation The 3π distributions are fitted in 10-MeV/c2 bins for the region 5.2<mES<5.29 GeV/c2 ω Line-shape is fixed (slide 17) The 3π distribution shows an ω signal only in the mES signal region A. Gabareen Mokhtar

  19. ω – ΔE signal correlation The 3π distributions are fitted in 40-MeV/c2 bins of ΔE in the range -0.18< ΔE <0.18 GeV/c2 The 3π distribution shows an ω signal only in the |ΔE| signal region A. Gabareen Mokhtar

  20. mES, ΔE, and ω signal correlation • The B→J/ψωKsignal can be derived by fitting either mES, ω, or ΔE! • Close to threshold  the 3π distribution is distorted • Lose statistical precision when using the weighting method (~2) A. Gabareen Mokhtar

  21. The strategy • Fitting the mESdistributions in mJ/ψ3πintervals • The B→J/ψωK candidates are the signal events as extracted from mES distributions • Consistency checks • Fit ΔE distributions in J/ψω mass intervals • Fit m3πdistributions in J/ψω mass intervals • The Y(J/ψω) sample is a sub-sample of the J/ψωK events A. Gabareen Mokhtar

  22. Signal Background data MC σ = 2.6±0.1 MeV/c2 μ=5279.1±0.1 MeV/c2 Nsig=734.2 (+41.6) (-41.0)(stat) CArg=-37.7 (+1.7) (-1.7) (stat) M(Y)=3940 MeV/c2 Γ(Y) = 0 MeV Fitting mES in B→Y(3940)K MC B± • Fitting mES is done in two steps: • Weighting ( -√10 P2)the signal MC and then fit with a single Gaussian to extract the mean and width • Fixing the mean and width, and fitting the data with ARGUS parameter free • From this point: mean, width & ARGUS parameter are fixed A. Gabareen Mokhtar

  23. Stability of the ARGUS parameter • Does the ARGUS parameter depend on mJ/ψ3π? A. Gabareen Mokhtar

  24. Low statistics → Poisson distribution • Poisson distribution is needed to deal with low statistics (provides stability to the fits) • Binned maximum likelihood mES fits: we minimize the function: L=2Σi (fi – Nobsi Log(fi)) • In mES fits Mass and width, and ARGUS parameter are fixed • Background and signal events are free A. Gabareen Mokhtar

  25. B±Events / 2 (MeV/c2) mES (GeV/c2) • 10-MeV intervals of mJ/ψ3π • Clear mES signals are observed in the range 3.8925-3.9325 GeV/c2 mES fits in 3.8825<mJ/ψ3π<3.9825 GeV/c2 A. Gabareen Mokhtar

  26. 50-MeV/c2 intervals in mJ/ψ3π mES fits in 3.9825<mJ/ψ3π<4.7825 GeV/c2 B± Events / 2 (MeV/c2) mES (GeV/c2) mES (GeV/c2) A. Gabareen Mokhtar

  27. B± →J/ψωK± B± →J/ψωK± Signal extraction from mES fits • We study the entire J/ψω mass region (from threshold to the kinematical limit (mB-mK) • Clear excess of events is observed close to threshold • The excess is localized below ~4 GeV/c2 • The weighted version shows similar behaviour but with larger statistical uncertainties A. Gabareen Mokhtar

  28. B± →J/ψωK± B± →J/ψωK± Consistency Y-signal extraction from ΔEfits • The ΔE distributions are fitted in the same binning of mJ/ψ3π as in mES fits • Clear excess of events is observed near threshold • Similar results to those given by fitting mES A. Gabareen Mokhtar

  29. So far… • The excess of events is seen in fitting mES ,ΔE, and m3π • However, since the signal is observed close to the J/ψω threshold, the m3πis distorted and extraction of the ω signal is difficult • The mESdistributions is not affected in this kinematical region • Therefore we are extracting the J/ψω signal by fitting the mESdistribution in each J/ψ3π mass interval A. Gabareen Mokhtar

  30. Exploring the data • Generic MC cannot produce the data peak • In the data, no evidence for B→J/ψK*(Kω) • The B→J/ψK*(Kω) is over estimated in the MC BellePRL 87, 161601(2001) A. Gabareen Mokhtar

  31. Five sets of MC were generated Syst Stat • For each mass, the zero width sample was generated MC generation choices A. Gabareen Mokhtar

  32. Reconstructed MC Y(J/ψω) signals • In the Y-MC samples, mES distributions are fitted in bins of Y-mass • Each point in the figure stands for the B-signal events (from mES fit) and the error bar represents the statistical uncertainty • The X(3872)→J/ψω sample does not show any peak in the region • 3.8825<mJ/ψω<4.08 GeV/c2 •  The resonance we observed is not due to X(3872) decay A. Gabareen Mokhtar

  33. Acceptance, purity, and efficiency • N1i ≡ The number of events generated and reconstructed in the ith bin • N2i ≡ The number of events generated the ith bin but not reconstructed in it (it can be migrated to other bins) • N3i ≡ The number of events generated outside the ith bin but reconstructed in the ith bin N1i, N2i , & N3i are un-correlated  A. Gabareen Mokhtar

  34. Bin-by-bin correction Acceptance from the fit Acceptance correction Works under the assumption that MC reproduce the data This is relevant when fit the acceptance with high order polynomial →→→ A. Gabareen Mokhtar

  35. Fit validation • Quasi-two-body phase-space is needed to describe the signal near threshold • S-wave relativistic Breit Wigner to describe the resonance A. Gabareen Mokhtar

  36. B+→Y(J/ψω)K+ Y(3940) Γ(60) Y(3940) Γ(110) mJ/ψω (GeV/c2) mJ/ψω (GeV/c2) Y(3915) Γ(20) Y(3925) Γ(30) mJ/ψω (GeV/c2) mJ/ψω (GeV/c2) Y(3930) Γ(20) mJ/ψω (GeV/c2) Testing the method • Fitting mES in 10-MeV bins of J/ψω mass for each MC sample • Correcting the signal number of events with the acceptance • Fitting the corrected distributions with free mass and width • Good fits were obtained • How do the mass-width values agree with the inputs? A. Gabareen Mokhtar

  37. 1.6 MeV/c2 shift Up-to 2σ difference Input-output comparison Here we compare the values of the mass & width from the MC fits with the input values as the MC was generated A. Gabareen Mokhtar

  38. Number of BB events (1.1 %) • Secondary branching fractions (up-to 1%) • Branching fraction of Y(4S) to B0B0 and B+B- (4.75 %) • MC statistics (mES parameters were varied by ±σ) • Particle Identification (6%) • Tracking efficiency (6%) • KS reconstruction efficiency (3%) Systematics A. Gabareen Mokhtar

  39. Simultaneous fit Free fit parameters: N±sig , N±bkg , m0 , Γ0 , R1 , R2 , μ , σ Fitting the data with Where: R1 the ratio of B0 to B+ in the signal region R2 the ratio of B0 to B+ in the non resonant region A. Gabareen Mokhtar

  40. Isospin conservation Fit results: plots • The B0 sample was corrected for K0L and K0S→π0π0 • Clear resonance is observed in the B+ channel • Less significant peak is observed in the B0 mode • The Gaussian function describe well the non-resonant region B+→J/ψωK+ B0→J/ψωK0 A. Gabareen Mokhtar

  41. Belle: m(Y)=3943±11(stat)±13(syst) Γ(Y)=87 ±22(stat)±26(syst) Belle PRL 94, 182002 (2005) BABARpreliminary Fit results: values BABARpreliminary B → X(3872)K: R1= 0.50 ± 0.31 BABAR PRD 73, 011101 (2006) B → J/ψK: R1= 0.865 ± 0.044 PDG B → ψ(2S)K: R1= 0.957 ± 0.106 PDG A. Gabareen Mokhtar

  42. Belle: PRL 94 182002 (2005) Fit results: Branching fractions BABARpreliminary A. Gabareen Mokhtar

  43. Fitting with Belle parameters • The fit was repeated with mass and width fixed to the Belle central values m(Y) = 3943 MeV/c2 Γ(Y) = 87 MeV • This leads to χ2/NDF = 57.6/44 to be compared with (36.2/42) • Then BR(B+)=(4.80 ± 1.22(stat))10-5 BR(B0)=(0.06 ± 1.81(stat))10-5 • Are BABARresults in agreement with the Belle ones? A. Gabareen Mokhtar

  44. X(3872)→J/ψπ+π-π0 Preliminary • Belle has reported: • B→X(3872)K, • X(3872)→J/ψπ+π-π0 • arXiv:hep-ex/0505037 Preliminary A. Gabareen Mokhtar

  45. mass (relative to X) X(3872)→J/ψπ+π-π0 X(3872)→J/ψπ+π- X(3872)→J/ψπ+π-π0 ? M.B. Voloshin: PRD 76, 014007(2007) • X(3872) →J/ψπ+π- should be significantly narrower than X(3872)→J/ψπ+π-π0 • If the two decays modes are allowed → isospin is violated (two & three pions in final state) • According to Voloshin model: → X(3872) →J/ψπ+π- & X(3872)→J/ψπ+π-π0 have the same mass • Our observation is far away from Voloshin prediction A. Gabareen Mokhtar

  46. B± X(3872)→J/ψπ+π-π0 ? • The un-weighted sample contains ω events as well as 3π combinations • The weighting method projects the ω events • The subtraction of the weighted from the un-weighted should show the non-ω 3π combinations • No evidencefor X(3872) →J/ψπ+π-π0 A. Gabareen Mokhtar

  47. Summary • The search for Y(3940)→J/ψω was done in the BABARexperiment • An evidence for B+ →Y(J/ψω)K+ has been observed with 5σ • Statistically limited signal observed in the B0 →Y(J/ψω)K0 • The ratio of B0 to B+ in the non Y-resonant region found in agreement with the prediction of the Isospin conservation • The ratio of B0 to B+ in the Y-resonant region is 3σ below the Isospin conservation • No evidence for B →X(3872)(Y(J/ψω)K) • No evidence for B →X(3872)(Y(J/ψπ+π-π0)K) • The sum of B0 & B+ branching fractions of agrees with the Belle results THANKS for your attention A. Gabareen Mokhtar

  48. ΔE low side-band ΔE side-band mES side-band ΔE high side-band mES side-band MC data Data-MC B background comparison II The weighted version of the previous distributions are consistent with zero A. Gabareen Mokhtar

  49. ω candidates at higher mJ/ψω masses Our signal! as shown in the Dalitz plot A. Gabareen Mokhtar

  50. Fitting ΔE • Fit the ΔE weighted signal MC distribution to fix the shape • ΔE is fitted with double Gaussian functions with different centers • Second Gaussian is needed to describe the asymmetric distribution in the low tail • Good fit was obtained. No structure in the difference between the distribution and the fitting function • From this stage on, we fix the shape of ΔE for any further fitting A. Gabareen Mokhtar

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