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Meson spectroscopy - glueballs

Meson spectroscopy - glueballs. Meike Door. Making a glueball Decay products Kaon detection Kinematic fitting Partial wave analysis Glueball candidates & spectra Further Research. Quantum Numbers are conserved. Making a glueball.

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Meson spectroscopy - glueballs

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  1. Meson spectroscopy - glueballs Meike Door • Making a glueball • Decay products • Kaon detection • Kinematic fitting • Partial wave analysis • Glueball candidates & spectra • Further Research

  2. Quantum Numbers are conserved Making a glueball J/ψ: meson, mass: 3097 MeV/c2 , lifetime ~10-20s, SpinParity (JP): 1- Glueball: particleconsistingsolelyofgluons , JP=0+ Short lifetime: decayproductsareamongothers K+K- ,K0K0, π+π- , …

  3. Measurethedecayproductsof a glueball • Let‘sfocus on K+K-, becausethisisthefavoreddecayprocess (shownby M.S. Chanowitz, „chiralsuppressionofscalar-Glueballdecay“, Physicalreviewletters, 2005)

  4. Kaondetection (16.09.09) Drift chamberxyview Chargedparticles: Usedriftchamber & TOF B-field in thedriftchamber → Kaonsfollow a curvedpath → calculatethemomentumoftheKaon 4

  5. Kaon detection (16.09.09) dE/dx EnergydepositiondE/dx in thechamber → particleidentification Kaonsare well distinguishable fromotherparticles TOF: mass & velocityofparticle

  6. Intermezzo: Kaons • Spin parity 0-, lifetime ~10-8s • K+ : K- : K0: : • due toweakinteractionthereis a couplingbetween K0K0 . → thephysicalKaonstatesare a mixure! → Discovery oftwokindsof neutral Kaons: Kl0 (long-lived, ~10-8s) and Ks0(short-lived, ~10-10s). SubjectofanotherSemimar! • But: Kaonsaredecayproductsofotherreactions, too… howcanyouprovethat a measuredKaoncamefrom a glueball? 0 _

  7. Conservationofenergy & momentum & Glueball decays in e.g. Kaons: energy & momentum has to be conserved! Remember last week: (in natural units, c=1) Decay into two Kaons: Invariant massoftheglueball Requirementforbeing a glueball !

  8. Addtionally, must hold. Advantage: The massof a kaonisvery well known: mK= 493,677±0,013 MeV E andaremeasuredwith an uncertainty. → modify E and so thatmKisobtained Thisiscalledkinematicfitting!

  9. Kinematicfitting §3.4 Idea:useknownpropertiesof a given processtoimprovethe measurementsandresolution. Mathematicalmethod…

  10. Untilnowweknow… • whatarethedecayproductsof a glueball(Kaonsfavored) • howKaonsaredetected • underwhichconditionsKaonsare a decayproductofglueball • Howtoimprovemeasurements & resolution Kinematicfitting Invariant massspectrum

  11. We had a glueball… What was its mass, witdh, spin, parity? Apply Partial Wave Analysis (PWA) (widely used in high energy physics). Use the fact that Cross section is measureable. How does the amplitude look like? Write it as Legendre Polynomial * weighting factor Cross section ~ Amplitude²

  12. PWA Legendre Polynomial x weighting factor → → Partial wave amplitude Spherical harmonic Get Alm using the orthogonality relation: * → Put in measured amplitude → Calculate partial wave amplitude Alm (This is for spin=0. Spin ≠0 is more complicated)

  13. Glueball spin Θisthedecay angle w.r.t. the reconstructed momentumof theglueball Spin 0: nofavoreddirection after decay → uniform angular distribution, flat spectrum Spin ≠ 0 : favoreddirection after decay → no uniform angular distribution, noflat spectrum Learnaboutthespinofyourglueball Diagrams: „Physicsat BES-III“, Kuang-Ta Chao andYifang Wang, 2008, §3.5.5

  14. What about parity? • Glueballscanhave all statesindicated in themassspectrum • Kaons: 0- • Thereare JPCstates, whichsupressdecayinto KK → Can youimaginewhy? Conservationofcharge/parityviolated

  15. Scalar Glueball candidates • f0(1370) • f0(1500) • f0(1710) Note: There are also vector- and tensor- glueballs, and pseudoscalar glueballs. Too much for today!

  16. Glueball f0(1370) f0(980) 3 particlesmeasured: φ, π+ , π- f0(980) candidateformultiquark ormoleculestates (Chapter 11, Physicsof soft Pions) f0(1790) discussedlater f0(1370) f0(1790)

  17. Glueball f0(1370) f0(980) Figure: broadenhancementaround f0(1370) BES II: strong f0(1370) signalfor J/ψ → π+π- Nosignificant f0(1370) signalfor J/ψ → K+ K- MassM=1350±50MeV Width Γ = 265±40MeV f0(1370) f0(1790) PWA: peakaround 1370MeV comesfrom a dominant f0(1370) termthatinterferes with an f2(1270) and a smaller f0(1500)

  18. Glueball f0(1500) f2(1270) background f0(1500) observed in many experiments, Interpreted as non- state Strong f2(1270) signal Shoulder at ~1.45 GeV Enhancement at ~1.7GeV Peak at ~2.1GeV Shaded area: background ~1.7GeV ~1.45GeV ~2.1GeV J/ψ→γπ+π-

  19. Glueball f0(1500) f2(1270), • PWA: background flat, peaksareleftover Two 0+ states in the 1.45GeV & 1.75GeV massregions In contrastto f2(1270), the f0(1500) is not directlyobserved in certainproductionchannelsof J/ψhadronicdecays(f0(1500) has a larger branchingratiotoππ than KK) → but existanceof a 0++ scalarat 1.5GeV issuggestedforotherproductionchannelswith a larger branchingratioto KK thantoππ J/ψ→γπ+π- f0(1500): M = 1466±6±20 MeV → future: searchfor f0(1500) in moredecaymodes & studyingitsspin-parity

  20. Glueball f0(1710) • f0(1710) main competitor of f0(1500) for the lightest 0+ glueball (large production rate, also in J/ψ decay) • Different experiments before BES gave different masses, widths and spin-parities • Most experiments give JP= 0+ • BES-II: M=1738±30MeV; Γ=125±20MeV, JP= 0+

  21. Glueball f0(1710) f0(1710) Pseuodoscalarglueball (not treated in thislecture) f2‘(1525) _ J/ψ→γKK M(K+K-) (GeV/c²) Wheredoesthebackgroundcomefrom? Spectrum: „Physics at BES-III“, Kuang-Ta Chao and Yifang Wang, 2008, §9.3.2

  22. Glueball f0(1710) PWA fit projection Peak at 1765±13MeV Thisstatemaybethe f0(1710) , the f0(1790) or a superposition!

  23. f0(1790) & f0(1710): 1 or 2 states? f0(1710) _ J/ψ→γKK f0(1790) left: f0(1790) peak, right: f0(1710) peak. Masseslieclosetogether! PWA showsthatthesestatesaredistinct

  24. Current & Further Research • 1~2GeV: at least 3 scalarmesons (glueballcandidates) (f0(1370), f0(1500) & f0(1710)) whichareexplored • Behaviourhasunexpectedfeatures • Questionsariseabout → structure → decaymechanism → glueball (yesorno?) → Ifyes: istheglueball pure ormixed? → natureofthecandidatesremains a mystery

  25. BES-III • Large data sample & excellentdetectorperformance will increasethesensitivity • Searchforotherhadronstatesispossiblewith BES-III • Recently, two additional scalarmesoncandidates (f0(1790)& f0(1810)) werereportedby BES-II → confirmationrequiredbyBES-III

  26. References • „Physicsat BES-III“, Kuang-Ta Chao andYifang Wang, 2008 • M.S. Chanowitz, „chiralsuppressionofscalar-Glueballdecay“, Physicalreviewletters, 2005 • BES-III detectorproperties, G.J. Tambave, lecture 16th sept. 2009

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