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Two New Resonances in the Strange Charm System.

Two New Resonances in the Strange Charm System. Brian Meadows University of Cincinnati. Outline. Charm meson spectroscopy – brief history. The Discovery of D * sJ (2317) ! D s  0 The second D sJ state Present experimental situation Summary and Discussion. Important Milestones.

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Two New Resonances in the Strange Charm System.

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  1. Two New Resonancesin the Strange Charm System. Brian Meadows University of Cincinnati Brian Meadows, U. Cincinnati.

  2. Outline • Charm meson spectroscopy – brief history. • The Discovery of D*sJ (2317)! Ds0 • The second DsJ state • Present experimental situation • Summary and Discussion Brian Meadows, U. Cincinnati

  3. Important Milestones 1974: J/ observed ! discovery of charm. 1975: Open charm discovered (c, FNAL BC 1975 ; D0, D+, SLAC 1976) 1976: De Rujula, Georgi, Glashow – light and heavy degrees of freedom decouple. 1989: Heavy Quark Symmetry Brian Meadows, U. Cincinnati

  4. SQ L Sq Heavy-Light Systems areLike the Hydrogen Atom • When mQ ! 1, sQ is fixed. • So jq = L­sq is separately conserved • Total spin J = jq­sQ • Ground state (L=0) is doublet with jq=1/2 • Orbital excitations (L>0) – two doublets (jq=l+1/2 and jq=l-1/2). • For decays to ground state (L=1)! (L=0) +  : • for jq=3/2 state, final hadrons are in orbital D wave !jq= 3/2 states are narrow. • for decay of DJ(jq=1/2) state, final hadrons are in orbital S wave !jq=1/2 states are expected to be broad. Brian Meadows, U. Cincinnati

  5. Heavy-Light Systems (2) 2jqLJ  JP • Narrow statesare easy to find. • Wide states are hard. • Since charm quark is not infinitely heavy, some jq=1/2, 3/2 mixing can occur for the JP=1+ states. jq = 3/2 2+ small 3P2 large 1+ 1P1 L = 1 1+ 3P1 small jq = 1/2 1P0 0+ large tensor spin-orbit jq = 1/2 1- small 1S1 L = 0 small 0- 1S0 Brian Meadows, U. Cincinnati

  6. Charmed Meson Spectroscopy • This picture worked well prior to this year with all narrow L=0 and L=1 states found by 1995. • The wide, nonstrange jl=1/2 states were found in B decays by CLEO (1999) and BELLE (2002). Subsequently confirmed by BABAR in 2003. • Many potential model calculations for masses and widths predicted, mostly correctly, the expected, wide jl=1/2 states • Generally agreed that L=1 nonstrange states - 1/2D0,1/2D1 would be above threshold for decay with  emission. • And that strange ones 1/2Ds0,1/2Ds1 would be above threshold for K emission. Brian Meadows, U. Cincinnati

  7. Charmed Meson Spectroscopy c. 1995 Brian Meadows, U. Cincinnati

  8. Charmed Meson Spectroscopy pre 2003 Brian Meadows, U. Cincinnati

  9. The BaBar Detector at SLAC (PEP2) • Asymmetric e+e- collisions at (4S). •  = 0.56 (3.1 GeV e+, 9.0 GeV e-) • Principal purpose – study CPV in B decays 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

  10. Electromagnetic Calorimeter • CsI (doped with Tl) crystals • Arranged in 48()£120() • » 2.5% gaps in . • Forward endcap with 8 more  rings (820 crystals). BABAR  0  Brian Meadows, U. Cincinnati

  11. 144 quartz bars Particle ID - DIRC • Measures Cherenkov angle in 144 quartz bars arranged as a “barrel”. • Photons transported by internal reflection • Along the bars themselves. • Detected at end by ~ 10,000 PMT’s Detector of Internally Reflected Cherenkov light PMT’s Brian Meadows, U. Cincinnati

  12. 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

  13. 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

  14. Run 3 Run 4 Run 2 Run 1 Off Peak PEP-II performances Peak Luminosity ~ 6 £ 1033 cm-2/ s-1 24 fb-1 in run 1 70 fb-1 in run2 36 fb-1 so far in run3 10 fb-1 so far in run4 This analysis uses runs 1 and 2 » 110 M cc pairs 9% off peak Currently (Nov 2003) run 4 is in progress with ~155 fb-1 Brian Meadows, U. Cincinnati

  15. On Off 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

  16. Charm at the BABARB Factory? • Present sample of 91 fb-1 sample contains • Compare with other 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

  17. 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 pD* > 2.5 GeV/c BABAR results from B decays are forthcoming however. Brian Meadows, U. Cincinnati

  18. K+K-+ Mass Spectrum Approx. 131,000 Ds+ events above large background. 4 3 2 1 0 X 103 X 103 60 40 20 0 D0! K+K- Events / 3 MeV/c2 1.75 1.85 1.95 m(K-K+) GeV/c2 1.8 1.9 2.0 m(K-K++) GeV/c2 Small bump at 2010 MeV/c2 from Brian Meadows, U. Cincinnati

  19. The Ds+ Dalitz Plot • Data sample: D*s(2112)+!Ds+: • NOTE • K* and  bands do not cross (no double counting). • cos2 distributions evident in vector bands. Selection essentially keeps events in the 4 peaks. Brian Meadows, U. Cincinnati

  20. Total K+K-+ Mass Spectrum • Sum of + and K¤0K+ contributions is » 80,000 Ds+ above background. • We define signal region: 1954 < m(K+K-+) < 1980 MeV/c2 and two sideband regions: 1912 < m(K+K-+) < 1934 MeV/c2 1998 < m(K+K-+) < 2020 MeV/c2 Brian Meadows, U. Cincinnati

  21. The Ds(2317)see PRL 90, 242001 (2003) • When Antimo Palano studied the Ds0 system he found a huge, unexpected peak. CLEO There is no signal from Ds+ sidebands. The Ds*!Ds+0 signal is clear too. How did CLEO miss it?! Brian Meadows, U. Cincinnati

  22. The Ds(2317) • The signal is clearly associated with both Ds+ and 0. There is no signal from 0 sidebands either. [NOTE – smearing the 0 signal smears the Ds*! Ds+0 signal too.] Brian Meadows, U. Cincinnati

  23. A Real Particle? • Is the signal due to reflection of a known resonance? Approximately 80 £ 106e+e-!cc reactions simulated. All that was known about charm spectroscopy was included. Conclude signal is not a reflection. Brian Meadows, U. Cincinnati

  24. CMS Momentum (p*) Dependence • Signal seen in all p* ranges. • Background less significant at higher p* values • Yield maximum at ~3.9 GeV/c • Excitation curve appears to be compatible with charm fragmentation process. Brian Meadows, U. Cincinnati

  25. 250 200 150 100 50 0  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 Multiple Ds+ Modes • Separate + and K¤0K+ subsamples: • Ds*+(2112) and signal at 2.317 GeV/c2 present in both channels with roughly equal strength. p* > 3.5 GeV/c Brian Meadows, U. Cincinnati

  26. 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. N = 1267 § 53 Events m = 2316.8 § 0.4 GeV/c2 = 8.6 § 0.4 MeV/c2 (errors statistical only).  is compatible with detector resolution. m requires small correction due to Ds(2458) overlap. Brian Meadows, U. Cincinnati

  27. Cross Check - a Different Topology Select Ds+! K-K++0 N = 273 § 33 events m = 2317.6 § 1.3 MeV/c2  = 8.8 § 1.1 MeV/c2 (consistent with detector resolution). Results agree with those from other Ds+ modes Brian Meadows, U. Cincinnati

  28. Conclusions on the state so far • Real and it decays to Ds+0: Implies natural parity. • Narrow - consistent with BaBar resolution : < 10MeV/c2. • If a normal Ds+ then this decay violates I spin conservation. • This could explain the narrowness. • Being below D0K+ threshold may force such a decay. • Could be the missing 0+ BUT if so, its mass is lower by » 170 MeV/c2 than expected by potential models. We label it “DsJ*(2317)+” • What else … Brian Meadows, U. Cincinnati

  29. DsJ+(2317) Decay Angular Distribution • Helicity angle distribution could provide spin information. • The corrected distribution in cos  is consistent with being flat (43% probability). • This could mean that J=0 or just that state is unaligned. Acceptance Uncorrected Corrected 0  DsJ(2317) 10 x Efficiency Ds cos cos cos Brian Meadows, U. Cincinnati

  30. 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. None of these found Brian Meadows, U. Cincinnati

  31. Ds+, Ds+, Ds*(2112) • No evidence for DsJ(2317) in any of these decays. • Absence of Ds+ weakly suggests J = 0 • However other two modes would be expected for a JP = 0+. Brian Meadows, U. Cincinnati

  32. Ds+0, Ds*(2112)0- Other Possibilities • No evidence for D*sJ(2317)+ either of these modes • BUT … • Is there a second state at ~ 2460 MeV/c2 ? Events / 7 MeV/c2 Ds*(2112)0 m(Ds+0) Brian Meadows, U. Cincinnati

  33. 2.4 2.3 2.2 2.1 2.0 m(Ds+)GeV/c2 2.1 2.2 2.3 2.4 2.5 m (Ds+0) GeV/c2 A Second State ? • The decays DsJ(2317)+!Ds+0 and Ds*(2112)+!Ds+ overlap kinematically just where m(Ds+0)~2460 MeV/c2. • Gives us two problems: • Produces a kinematic peak at 2460 MeV/c2 – signal? • Resolution smearing makes it difficult to distinguish decays of a 2460 MeV/c2 state to Ds*(2112)+0 or D*sJ(2317)+ ? m(Ds+0)= 2.46 GeV/c2 Brian Meadows, U. Cincinnati

  34. A Second State ? • Another concern we resolved: Is the D*sJ(2317) signal just a reflection of the higher mass state?! • NO – such reflection is • Too wide • Wrong mass • Too small by factor ~ 5. Brian Meadows, U. Cincinnati

  35. A Second State ? … from our PRL 90 (2003) 242001. • “Although we rule out the decay of a state of mass 2.46 GeV/c2 as the sole source of the Ds+0 mass peak corresponding to the D*sJ(2317)+, such a state may be produced in addition to the D*sJ(2317)+. However, the complexity of the overlapping kinematics of the Ds*(2112)+!Ds+ and D*sJ(2317)+!Ds+0 decays requires more detailed study, currently underway, in order to arrive at a definitive conclusion.” Meanwhile … Brian Meadows, U. Cincinnati

  36. CLEO Sees D*sJ(2317) Too m(Ds0) – m(Ds) 350.0 § 1.2 (stat) § 1.0 (syst) (MeV/c2) Not in Ds+- • From 13.5 fb-1 CLEO II • Signal seen in Ds0 • Not seen in Ds+-, • Ds, Ds1(2112) Signal has events (» same yield / fb-1 as BABAR). PRD 68, 032002 (2003) Brian Meadows, U. Cincinnati

  37. So Does Belle (in continuum) • 78 fb-1 sample • Ds!, p* > 3.5 GeV/c • M = 2317 § 0.5 MeV/c2 • = 8.1 § 0.5 MeV/c2 • N = 770 § 43 events • They also observe it in • B!D DsJ decays. Y. Mikami, et al, hep-ex/0307052v2 (2003) Brian Meadows, U. Cincinnati

  38. The DsJ (2458)+ • CLEO results are published with title: “Observation of a Narrow Resonance of Mass 2.46-GeV/c2 Decaying to Ds*(2112)+0 and Confirmation of the D*sJ(2317)+ State.” in PRD 68, 032002 (2003) • BELLE has also observed the DsJ (2458)+ • In continuum – hep-ex/0307052 • In B!DDsJ decay – hep-ex/0308019 • What BABAR says about the second state now … Brian Meadows, U. Cincinnati

  39. 2.4 2.3 2.2 2.1 2.0 m(Ds+)GeV/c2 2.1 2.2 2.3 2.4 2.5 m (Ds+0) GeV/c2 Recap - theProblem • The decays DsJ(2317)+!Ds+0 and Ds*(2112)+!Ds+ overlap just where m(Ds+0)~2460 MeV/c2. • This gives us two problems: • Produces a kinematic peak at 2460 MeV/c2 • Resolution smearing makes it difficult to distinguish decays of a 2460 MeV/c2 state to Ds*(2112)+0 or DsJ(2317)+ m(Ds+0)= 2.46 GeV/c2 Brian Meadows, U. Cincinnati

  40. BABAR - There is a Signal! Data MC A strong peak appears in BABAR data that is absent in generic MC [e+e-!cc that includes D*sJ(2317)+ production]. Attribute the excess to a new signal at 2458 MeV/c2. DsJ(2458)+ m() ´ m(KK0) - m(KK0) m(0) ´ m(KK0) - m(KK) NOTE – Change of variables Next: a) extract signal strength and properties; b) distinguish Ds*(2112)+0 from DsJ(2317)+ Brian Meadows, U. Cincinnati

  41. 100 80 60 40 20 0 0.3 0.2 0.1 80 60 40 20 0 Events / 7 MeV/c2 m() GeV/c2 0.25 0.50 m(0) GeV/c2 0.25 0.50 m(0) GeV/c2 0.25 0.50 m(0) GeV/c2 Extraction of Signal from Background Seems most obvious method - make a (peaking) sideband subtraction and fit to Gaussian: ! m = 344.6 § 1.2 MeV/c2. BUT: • Assumes background is linear. • Not true as resolution of m(0) changes with m(). • Width of signal depends on width of sideband selected. • Ignores D*sJ(2317)+ decay possibility. Brian Meadows, U. Cincinnati

  42. Monte Carlo for DsJ(2458)+!Ds*(2112)0 Monte Carlo for DsJ(2458)+!DsJ(2317) Decay Mode • Distinction between Ds*(2112)0 and DsJ (2317)+ decays is possible from different line shapes each produces. • Data clearly prefer the shape for DsJ (2458)+! Ds*(2112)0 Brian Meadows, U. Cincinnati

  43. Channel Likelihood1 Method • Determine fractions xi of processes producing events and best mass (m) and Gaussian width () for DsJ (2458). • Each Ds+0 combination is assigned a likelihood: L = x1P1 + x2P2 + … + (1 - x1 - x2 - …) where Pi are normalized Probability Density Functions. Processes included were: P1: DsJ(2458) !Ds*0 P2: DsJ(2458) !DsJ(2317) P3: Ds+0!Ds* + random  P4: Ds+0!DsJ(2317) + random 0 P5: Ds+0! combinatorial background Assumption: that DsJ(2458) decay is all quasi two body with no interference (reasonable since the states are all narrow). 1 P.E. Condon and P.L. Powell, PRD 9, 2558 (1974) Brian Meadows, U. Cincinnati

  44. Fit Results • Important results from the fit are: • The DsJ(2458)+ width is consistent with detector resolution indicating that the state is narrow. • We infer that: Brian Meadows, U. Cincinnati

  45. Fit Results (2) • The fit assigns a probability xiPi to each event to belong to a process, so weighted plots take account of all reflections. Unweighted Ds+0 Weighted Data Weighted DsJ(2458)+!Ds*+0 Fit Weighted DsJ(2458)+!DsJ(2317)+ Brian Meadows, U. Cincinnati

  46. Correction to DsJ (2317)+ Mass • Distortion of the DsJ(2317)+ signal due to background from DsJ(2458)+!Ds*(2112)+0decays can be estimated from a Monte Carlo study. • Re fitting to include this, DsJ(2317)+ parameters are: m = 2317.3 § 0.4 MeV/c2 ;  = 7.3 § 0.2 MeV/c2. Brian Meadows, U. Cincinnati

  47. Spin-Parity of DsJ(2458)+ • The decay observed here violates I-spin. The width is small. • So natural parity (0+, 1-, 2+, …) appear to be ruled out as this state could decay to D0K+, conserving I-spin. • It is below D*K threshold, a decay accessible to unnatural parity, so its width is compatible with JP=0-, 1+, 2-, … • The helicity distribution is also consistent with this hypothesis. Brian Meadows, U. Cincinnati

  48. Spin-Parity of DsJ (2458)+ • Helicity angle of : • JP = 0- agrees worst. 1- and 2+ cannot be ruled out. • Unnatural parity distributions depend on alignment of DsJ(2458)+.  Ds*(2112) h 0 Ds No conclusive information on spin here Brian Meadows, U. Cincinnati

  49. Belle 86.9 fb-1 CLEO “Ds(2463)” 13.5 fb-1 D*(2112) D*(2112) sidebands N = 41§ 12 events (>5) m = 349.8 § 1.3 MeV/c2 N = 126§ 25 events m = 345.4 § 1.3 MeV/c2 CLEO and Belle See Ds(2458) in Continuum PRD 68, 032002 (2003) hep-ex/0307052 Brian Meadows, U. Cincinnati

  50. More Observations by Belle • See both states in B decay • See DsJ(2458)+!Ds+ Continuum B!D DsJ DsJ(2317)+ !Ds+0 DsJ(2458)+ !Ds*(2112)+0 DsJ(2458)+ !Ds+ Rules out J = 0 Brian Meadows, U. Cincinnati

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