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Changyi Zhou (McGill University ) on behalf of ZEUS Collaboration

Changyi Zhou (McGill University ) on behalf of ZEUS Collaboration February 26, 2008. Outline. Analysis motivations Previous publication and results Experimental setup and observation principle Data sample selection and K 0 s mass distribution

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Changyi Zhou (McGill University ) on behalf of ZEUS Collaboration

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  1. Changyi Zhou (McGill University ) on behalf of ZEUS Collaboration February 26, 2008

  2. Outline • Analysis motivations • Previous publication and results • Experimental setup and observation principle • Data sample selection and K0s mass distribution • K0sK0s spectra with interference fits • Non-interference function • Interference function • Summary and conclusion ECT *– Trento, February 25-29, 2008

  3. Motivations • The Standard Model explains the existence of hadrons well. • The Standard Model allows for the existence of particles made by gluons. • A gluon carries both a color and an anti-color. • Either two or three gluons may confine together as color singlet GLUEBALLs Examples of glueballs ECT *– Trento, February 25-29, 2008

  4. Motivations (Cont.) • The K0sK0s system is expected to couple to scalar and tensor glueballs K0s: has S=0, P=-1, C=+1 K0sK0s : has P=+1, C=+1  J = even Question: What is the mixing fraction of mesons and glueballs? Hybrid? Tetraquarks? Flavor octet states? ECT *– Trento, February 25-29, 2008

  5. Motivations (Cont.) ECT *– Trento, February 25-29, 2008

  6. Previous Publication • “K0sK0s Final State in two photon collisions and implications for glueballs” (L3) Published in Phys.Lett.B501:173-182,2001 (hep-ex/0010037) ~4σ for fJ(1710) ECT *– Trento, February 25-29, 2008

  7. HERA ECT *– Trento, February 25-29, 2008

  8. HERA and ZEUS ECT *– Trento, February 25-29, 2008

  9. Micro-Vertex Detector (MVD) Tracking Detector Central Tracking Detector (CTD) • official coordinate resolution ~160 m e p • 25-35 m resolution for vertical incidence ECT *– Trento, February 25-29, 2008

  10. K0sK0s states observation principles pπ+ pk1 π+ Collinearity Angle pπ- Pri. Vtx K0s π- Sec. Vtx IP pπ+ π+ K0s Decay Length pk2 pπ- Two V0 candidates π-

  11. DATA Sample and Event Selection The data sample is dominated by 90% photoproduction, while 10% is Deep Inelastic Scattering ECT *– Trento, February 25-29, 2008

  12. K0s mass distribution Full sample contains: 1300509 K0s 672418 K0sK0s ECT *– Trento, February 25-29, 2008

  13. Fitting functions • Modified Relativistic Breit-Wigner (MRBW) function: • Ci is the amplitude of the resonance • m*,i is the mass of resonance • Гd,i is the effective resonance width • M is the K0sK0s invariant mass • Background function: • A, B, C are free parameters • mK0s is the K0s mass from PDG ECT *– Trento, February 25-29, 2008

  14. Fitting using Breit-Wigner with no interference The structure around 1270 region is due to the destructive interference between f2(1270) and a2(1320) JPC= 0++ JPC= 2++ 2++ 2++ The dip between f2(1270)/a2(1320) and f2(1525) is due to the constructive interference between the states. ECT *– Trento, February 25-29, 2008

  15. Fitting using Breit-Wigner with interference No interference fit Interference fit WA102 ECT *– Trento, February 25-29, 2008

  16. Fitting using Breit-Wigner with interference Function = a {5 * BW_f2(1270) – 3* BW_a2(1320) + 2 * BW_f2(1525)}2 + b {BW_f0(1710)}2 + c Background U(M) a b c are free parameters BW is Relativistic Breit-Wigner function: ECT *– Trento, February 25-29, 2008

  17. Fitting using Breit-Wigner with interference Destructive interference Х2/ndf = 86/110 Improved fitting in 1270 and 1420 region, where destructive and constructive interference are well described. ECT *– Trento, February 25-29, 2008

  18. Summary ECT *– Trento, February 25-29, 2008

  19. Conclusion • Inclusiveep → K0s K0sX decay production was studied with all ZEUS statistics (0.5 fb-1) • Clear evidence for f’2(1525) and f0(1710) resonance state with large statistical significance • Very competitive measurements on peak position and width for f’2(1525) and f0(1710) are done with interference fit and compared well with the PDG values End ECT *– Trento, February 25-29, 2008

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