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Low Mass Scalars - Experimental

Low Mass Scalars - Experimental. C.Bini Sapienza Università and INFN Roma 22 June 2012. A rich structure of states below 2 GeV hard to produce and to analyze . Two interesting features in the two multiplets :  inverted spectra

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Low Mass Scalars - Experimental

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  1. Low Mass Scalars - Experimental C.Bini Sapienza Università and INFN Roma 22 June 2012

  2. A richstructureofstatesbelow2GeV hard to produce and toanalyze. Twointerestingfeatures in the twomultiplets:  inverted spectra  one extra f0 state (I=0) (even if strongly controversial) Muchspaceforexotics: 4q + gluonium

  3. Fewclearpoints: • The sigma pole isthere, but IT IS NOT a BW (aspointed out severaltimesbyD.Bugg). Itmanifestsitselfas a bump in mass distributions or Dalitzplots, tipically people needittofit data, but “handlewith care”; • f0(980) and a0(980) are stronglycoupledtoKaons, hencehave a large s-quark contentin theirwavefunctions • (KLOE and NovosibirskfSg results); • Problemswithisospin (violationsobserved (seeJ/ygppp) talk byB.Liu; • ggisapparentlynot conclusive (evenifinterestingworks are there, seePennington), butprobably more insightisneeded on this.

  4. BES3 is in the frontlineforthisphysics (J/ydecays): poorstatisticsis no more a problem

  5. Notonlyimprovementofstatistics, butalsoof detector performance BES3 BES2 Strong reductionof background due toimprovement in gdetection.

  6. BES presented at thisconference a detailedstudyof the ppamplitude in J/ygp0p0 with PWA (covariant tensor formalism) (B.Liu). f0(980) and f0(1370) belowsignificance limits

  7. BES presented MC testsof MIPWA and conclude:

  8. “a nightmare for experiment and a paradise for theory!” (S.Eidelman) Conclusionfromanexperimentalistpointofview: not a nightmarebut a sortof “frustration”: so beautiful and high quality data and not a firmconclusionfromthem. Are “newexperimental data badlyneeded” ? Bottomline: the nature ofhadrons (and of scalar hadrons in particular) isintrinsicallycomplicated, out ofour full understanding at leastnow. A realstepforward in interpretationisbadlyneeded.

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