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A New Narrow Resonance in the D s +  0 System.

A New Narrow Resonance in the D s +  0 System. Brian Meadows University of Cincinnati. Outline. Introduction The BaBar Experiment Observation of D sJ (2317) ! D s  0 Search for other Modes ! D s  , D s  , D s1 (2112), D s  0  0 , D s  0  Corroboration by CLEO

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A New Narrow Resonance in the D s +  0 System.

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  1. A New Narrow Resonance in the Ds+0 System. Brian Meadows University of Cincinnati Brian Meadows, U. Cincinnati.

  2. Outline • Introduction • The BaBar Experiment • Observation of DsJ (2317)! Ds0 • Search for other Modes !Ds, Ds, Ds1(2112), Ds00, Ds0 • Corroboration by CLEO • Interpretations • Summary Brian Meadows, U. Cincinnati

  3. Introduction The spectrum of Ds (cs) states has gaps. • The scalar state predicted could decay to DK so it would be broad (» 270-990 MeV/c2). Observed Predicted Ds2 Ds1 D*K Mass GeV D0K D*s DsJ(2317) Ds New State JP This would make it difficult to observe …BUT If it were below DK threshold, it could be narrow. Brian Meadows, U. Cincinnati

  4. The BaBar Detector at SLAC (PEP2) • Asymmetric e+e- collisions at (4S). •  = 0.56 (3.1 GeV e+, 9.0 GeV e-) 1.5 T superconducting field. Instrumented Flux Return (IFR) Resistive Plate Chambers (RPC’s): Barrel: 19 layers in 65 cm steel Endcap: 18 “ “ 60 cm “ Brian Meadows, U. Cincinnati

  5. Particle ID - DIRC Detector of Internally Reflected Cherenkov light • Measures Cherenkov angle in quartz • Photons transported by internal refl. • Detected at end by » 10,000 PMT’s 144 quartz bars Brian Meadows, U. Cincinnati

  6. Particle ID - DIRC It Works Beautifully! Provides excellent K/ separation over the whole kinematic range Brian Meadows, U. Cincinnati

  7. Electromagnetic Calorimeter • CsI (doped with Tl) crystals • Arranged in 48()£120() • » 2.5% gaps in . • Forward endcap with 8 more  rings (820 crystals). Brian Meadows, U. Cincinnati

  8. PEP-II performances Peak Luminosity 4.9 £ 1033 cm-2¢ s-1 • 24 fb-1 in run 1 • 70 fb-1 in run2 • 10 fb-1 so far in run3 run3 This analysis uses runs 1 and 2 » 110 M cc pairs run2 (~12% off peak) run1 Brian Meadows, U. Cincinnati

  9. Off • On Charm at the BABARB Factory? • Cross section is large Can use off peak data • Also • Relatively small combinatorial backgrounds in e+e- interactions. • Good particle ID. • Detection of all possible final states including neutrals. • Good tracking and vertexing • Very high statistics. Brian Meadows, U. Cincinnati

  10. Charm at the BABARB Factory? • Present sample of 91 fb-1 sample contains • Compare with earlier charm experiments: • E791 - 35,400 1 • FOCUS - 120,000 2 • CDF - 56,320 • Approximately 1.12 £ 106 untagged D0!K-+ events 1. E791 Collaboration, Phys.Rev.Lett. 83 (1999) 32. 2. Focus Collaboration, Phys.Lett. B485 (2000) 62. Brian Meadows, U. Cincinnati

  11. Data Selection • All pairs of ’s, each  having energy > 100 MeV, are fitted to a 0 with mass constraint. • Each 0 is fitted twice: • To the production vertex to investigate the Ds+0 mass. • To the K+K-+ vertex so that we can also use the Ds! K+K-+0 mode. D’s from B decays were removed: - each event was required to have p*D > 2.5 GeV/c Brian Meadows, U. Cincinnati

  12. K+K-+ Mass Spectrum Approx. 131,000 Ds+ events above large background. Small bump at 2010 MeV/c2 from Brian Meadows, U. Cincinnati

  13. The Ds+ Dalitz Plot • Events in the Ds+ mass band: • K* and  bands do not cross (no double counting). • cos2 distributions evident in vector bands. Brian Meadows, U. Cincinnati

  14. Selection of Ds+!+ and K¤0K+ • Select  mass band: |m(K+K-) – 1.019| · 0.01 GeV/c2; • Select K¤0 mass band: |m(+K-) – 0.896| · 0.05 GeV/c2; • Require |cos| > 0.5 to enhance proper helicities of each vector. • Each resulting sample has about same size. Brian Meadows, U. Cincinnati

  15. Total K+K-+ Mass Spectrum • Sum of + and K¤0K+ contributions is » 80,000 Ds+ above background. • We define • signal region: 1.954 < m(K+K-+) < 1.980 GeV/c2 • and two sideband regions: 1.912 < m(K+K-+) < 1.934 GeV/c2 1.998 < m(K+K-+) < 2.020 GeV/c2 Brian Meadows, U. Cincinnati

  16. Ds+0 Mass Spectrum • A striking signal observed in the Ds+0 system. • Signal clearly associated with both Ds+ and 0 • Is not a reflection of any other known state (MC) D § Ds§ 0 Brian Meadows, U. Cincinnati

  17. 200 150 100 50 0 K* Events / 5 MeV/c2 2.1 2.3 2.5 2.1 2.3 2.5 m(Ds+0)GeV/c2 Ds+0 Mass Spectra • Separate + and K¤0K+ subsamples: • Require p¤ > 3.5 GeV/c • Ds*+(2112) and signal at 2.32 GeV/c2 present in both channels with roughly equal strength. Brian Meadows, U. Cincinnati

  18. Study Ds+0 mass spectrum behavior in p* intervals Present in all intervals Better signal to background at higher p* values Study dependence in Monte Carlo Ds0 CMS Momentum (p*) Dependence • A p* > 3.5 GeV/c cut • Improves signal-to-background • Slightly improves resolution Brian Meadows, U. Cincinnati

  19. 400 300 200 100 0 Events / 5 MeV/c2 2.1 2.2 2.3 2.4 2.5 m(Ds+0) GeV/c2 Fit to the Signal • Require p* > 3.5 GeV/c. Fit to polynomial and a single Gaussian. m = 2316.8 § 0.4 GeV/c2 = 8.6 § 0.4 MeV/c2 (errors statistical only). Brian Meadows, U. Cincinnati

  20. Experimental Resolution • Fit Ds*+(2112) width in Monte Carlo and Data: Data:  = 6.6 § 0.1 MeV/c2 MC:  = 5.7 § 0.1 MeV/c2 • So MC is too optimistic by factor 1.16. • Generate Monte Carlo events for DsJ+(2317) with  = 0:  = 7.7 § 0.2 MeV/c2 • Scale by factor 1.16 ! expect  = 8.9 MeV/c2. • ForDsJ+(2317) with p* > 3.0 GeV/c we find:  = 9.0 § 0.4 MeV/c2 So width is consistent with mass resolution. Brian Meadows, U. Cincinnati

  21. Data from Ds+!K+K-+0 X 103 Use other vertex for 0 Require at least one vector meson in two body subsystem. No  from a 0 candidate can be part of any other 0. Require p* > 3.5 GeV/c. Require laboratory momentum of each  be > 300 MeV/c. 25 20 15 10 5 0 Ds+ D+ 1.75 2.0 m(K+K-+0) GeV/c2 Brian Meadows, U. Cincinnati

  22. Over 1500 events in the signal. The resonance has width comparable with the mass resolution in these systems. It is evident in two different topologies a)D§s!K§ K¨ § (two modes) b) D§s!K§ K¨ §0 Masses consistent in all channels – width » resolution. New Narrow Resonance “DsJ(2317)” “Ds(2317)” Ds1(2112) p* > 3.5 GeV/c p* > 3.5 GeV/c Ds1(2112) Brian Meadows, U. Cincinnati

  23. DsJ+(2317) Decay Angular Distribution • Helicity angle distribution could provide spin information. • The Ds+0 mass spectrum is fitted in 10 slices of cos . • The corrected distribution in cos  is consistent with being flat (43 % probability). uncorrected Acceptance corrected cos  cos  cos  Brian Meadows, U. Cincinnati

  24. Search for Other DsJ+(2317) Decay Modes • We have studied the mass spectra for • Ds+00 • Ds+ • Ds+ • Ds*+(2112) • Ds+0 • In all cases, we require that: • The ’s are not part of any 0 candidate. • The combination has p* > 3.5 GeV/c. Brian Meadows, U. Cincinnati

  25. DsJ (2317)? Events / 12 MeV/c2 m(Ds00) GeV/c2 Ds00 System Limited statistics in this system. No prominent structure at the mass of DsJ+(2317) Brian Meadows, U. Cincinnati

  26. Ds+, Ds+, Ds1(2112) • No evidence for any of these decays. • Suggests JP = 0+ Brian Meadows, U. Cincinnati

  27. DsJ(2317) Other Possibilities -Ds+0, Ds1(2112)0 • No evidence for DsJ(2317) • Enhancement at 2460 MeV/c2 mostly due to kinematic overlap between DsJ(2317) and Ds1(2112) bands. • Great care required to extract any signal from the region. Ds1(2112)0 Brian Meadows, U. Cincinnati

  28. CLEO Sees it Too Not in Ds+- • They use 13.5 fb-1 • Signal seen in Ds0 • Not seen in Ds+-, • Ds, Ds1(2112) Signal has events (» same yield / fb as BABAR). Brian Meadows, U. Cincinnati

  29. Physics Summary • We observe a state at 2.32 GeV/c2 whose measured width is consistent with the mass resolution ( < 10 MeV/c2). • So far, this is only seen in the Ds0 decay mode. • The mass is about 40 MeV/c2 below the DK threshold. • The decay to Ds0 implies natural parity (0+, 1-, 2+, etc.) • JP=0+ suggested by absence of a signal in Ds+ and Ds00. • If this is so, decay to Ds1(2112)  is allowed, but not yet seen. Brian Meadows, U. Cincinnati

  30. So What is this State? • If this state is a cs meson, then the decay observed violates isospin conservation • This is not unusual. Ds1(2112) also decays to Ds0 about 5% of the time. Cho and Wise have predicted this rate using 0- mixing. • A multi quark state (conjectured by N. Isgur and H. Lipkin). • First heavy quark recurrence of a0(980) or even f0(980)? a0(980) ! / KK (I=1) f0(980) ! / KK (I=0) • Work is in progress to search for Ds+§ decay modes. Brian Meadows, U. Cincinnati

  31. If it is a cs Meson … R. Cahn and J.D. Jackson, hep-ph/0305012. • It could be the missing P wave cs state with JP = 0+. • Our result disagrees with current expectations. Mass and decay modes are quite different from those expected. • Use Ds(2317) mass as one of three inputs – predict mass of fourth p wave state. pwave states Drawing: R Cahn, J. Jackson Brian Meadows, U. Cincinnati

  32. Summary • New charmed, strange, narrow resonance at 2.32 GeV/c. • Poses possible problems for the quark potential model. • May be a four quark or DK bound state. • Much speculation is being generated: R. Cahn, J.D. Jackson, hep-ph/0305012 T. Barnes, F. E. Close, H. J. Lipkin, hep-ph/0305025 E. Van Beveran, G. Rupp, hep-ph/0305035 H-Y Cheng, W-S Hou, hep-ph 0305038 W. A. Bardeen, E. J. Eichten, C. T. Hill, hep-ph 0305049 P. Szczepaniak, hep-ph 0305060 S. Godfrey, hep-ph/0305122 P. Colangelo, F. De Fazio, hep-ph/0305140 Brian Meadows, U. Cincinnati

  33. Back up Slides Brian Meadows, U. Cincinnati

  34. Silicon Vertex Tracker (SVT) • 5 Layers double sided AC-coupled Silicon • Rad-hard readout IC (2 MRad – replace ~2005) • Low mass design • Stand alone tracking for slow particles • Point resolution z » 20 m • Radius 32-140 mm Brian Meadows, U. Cincinnati

  35. Drift Chamber 40 layer small cell design 7104 cells He-Isobutane for low multiple scattering dE/dx Resolution »7.5% Mean position Resolution 125 m Brian Meadows, U. Cincinnati

  36. Particle ID - DIRC D0 D0 Brian Meadows, U. Cincinnati

  37. An Example: Ds Production spectrum • Below 2.4 GeV/c Ds can come from B decay • Use off peak data there to reduce combinatorial background Off peak (normalized for p*>2.4 GeV/c) On peak Brian Meadows, U. Cincinnati

  38. Data Selection • In this study we look for resonances decaying to: Ds0 • Ds+ mesons are selected with +,K¤0K+ and K+K-+0 decay modes, so we select events in final state: K+K-+ (+ charged conjugate) • To do this we: • Select all combinations of three charged tracks with total charge § 1, an identified K+K- pair and a third track which is not a K§. • Require Ds+ candidate fit well to a common vertex. • Fit the Ds+ composite momentum to a primary vertex Brian Meadows, U. Cincinnati

  39. Resolution Improvement a) Constrain Ds mass b) Remove duplicated ’s Brian Meadows, U. Cincinnati

  40. Another Topology Ds+!K+K-+0 Rational: • Mode has same topology as Ds+0 when Ds+!K+K-+. • Width of Ds+!K+K-+0 gives further, direct information on the Ds+0 mass resolution. • Can provide corroborative evidence for Ds+0(2317) signal. Strategy: • Use other vertex fit. • Select cleaner sample using K*0, K*§, +,  resonant sub channel selections. Brian Meadows, U. Cincinnati

  41. Test Using Monte Carlo Simulation • We simulate the reaction e+e-!cc using GEANT4. • Events generated contain all that is presently known about charm spectroscopy. • Approximately 80 x 106 events are processed exactly the same way as the data. Brian Meadows, U. Cincinnati

  42. Test Using Monte Carlo Simulation • Sum of + and K¤0K+ and Ds+0 mass spectra. • We observe the known decay: Ds¤+(2112)!Ds+0. • The Ds+0 mass spectrum shows no sign of 2.32 GeV/c2 signal. We would expect » 1,400 events. We conclude that the 2.32 GeV/c2 structure is not due to reflections from known charm states. Brian Meadows, U. Cincinnati

  43. 2.32 GeV/c2 Is 2.32 GeV/c2 Structure due to Ds¤+(2112)? • We use the ’s from the 0 candidate to compute the two masses Ds+1,2. • The 2.32 GeV/c2 signal survives when events with a Ds+1,2 mass in the Ds¤+(2112) are removed. Ds¤+(2112) removed Ds¤+(2112) selected We conclude that the signal at 2.32 GeV/c2 is not a Ds¤+ reflection Brian Meadows, U. Cincinnati

  44. Mass and Width Ds+!K-K++0: M = 2317.6 § 1.3 MeV/c2  = 8.8 § 1.1 MeV/c2 Ds+!K*0K+, +: M = 2316.8 § 0.4 MeV/c2  = 8.6 § 0.4 MeV/c2 Brian Meadows, U. Cincinnati

  45. DK Molecule? T. Barnes, F.E. Close, H.J. Lipkin, hep-ph/0305025 • I=0 csnn or a DK bound state? • If DK bound state, then some I=0 component to explain narrow width. Brian Meadows, U. Cincinnati

  46. A qqcs Four Quark State? From H. Cheng and W. Hou, hep-ph/0305038. Brian Meadows, U. Cincinnati

  47. Quasi Bound cs State? E. van Beveren, G. Rupp, hep-ph/0305035 • Charmed cousin of a0(980), f0(980), (600), (800) nonet. • Predicts D0(2030) – broad because above DK threshold • Also predicts D0(2640), D0(2790) to go with K0(1430), etc. Brian Meadows, U. Cincinnati

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