Changyi Zhou Mc Gill University on behalf of

Changyi Zhou (Mc. Gill University on behalf of ZEUS Collaboration February 26, 2008 )

Outline l l l Analysis motivations Previous publication and results Experimental setup and observation principle Data sample selection and K 0 s mass distribution K 0 s spectra with interference fits Non-interference function Ø Interference function Ø l Summary and conclusion C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 2

Motivations n n 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 C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 3

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

Motivations (Cont. ) C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 5

Previous Publication n “K 0 s Final State in two photon collisions and implications for glueballs” (L 3) Published in Phys. Lett. B 501: 173 -182, 2001 (hep-ex/0010037) ~4σ for f. J(1710) C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 6

HERA C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 7

HERA and ZEUS C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 8

Tracking Detector Central Tracking Detector (CTD) nofficial m e coordinate resolution ~160 p Micro-Vertex Detector (MVD) m resolution for vertical incidence n 25 -35 C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 9

K 0 s states observation principles pπ+ π+ pk 1 Collinearity Angle Pri. Vtx K 0 s π- pπ- Sec. Vtx IP Dec ay K 0 s π+ pπ+ Leng th π- pk 2 Two V 0 candidates

DATA Sample and Event Selection Luminosity HERAII Total 121. 6 pb-1 401. 68 pb-1 ≈ 0. 5 fb-1 Tracking Quality Cuts Pт(pion) (Ge. V) η(pion) > 0. 14 (-1. 75, 1. 75) K 0 s Selection Cuts Pт(kaon) (Ge. V) > 0. 25 η(kaon) (-1. 6, 1. 6) Decay Length (cm) (0, 30) Collinearity(2 D) < 0. 12 Inv_ππ (Ge. V) (0. 4806, 0. 515) C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 The data sample is dominated by 90% photoproduction, while 10% is Deep Inelastic Scattering 11

K 0 s mass distribution Full sample contains: 1300509 K 0 s 672418 K 0 s C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 12

Fitting functions Ø 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 K 0 s invariant mass Ø Background function: • A, B, C are free parameters • m. K 0 s is the K 0 s mass from PDG C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 13

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

Fitting using Breit-Wigner with interference No interference fit Interference fit WA 102 C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 15

Fitting using Breit-Wigner with interference Coherent States Isospin I = f 2(1270) a 2(1320) f 2(1525) 0 1 0 5 BW -3 BW 2 BW Quark Content Charge Factor Amplitude ratio Function = a {5 * BW_f 2(1270) – 3 * BW_a 2(1320) + 2 * BW_f 2(1525)}2 + b {BW_f 0(1710)}2 + c Background U(M) a b c are free parameters BW is Relativistic Breit-Wigner function: C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 16

Fitting using Breit-Wigner with interference Destructive interference Х 2/ndf = 86/110 Improved fitting in 1270 and 1420 region, where destructive and constructive interference are well described. C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 17

Summary C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 18

Conclusion n Inclusive ep → K 0 s. X decay production was studied with all ZEUS statistics (0. 5 fb-1) n Clear evidence for f’ 2(1525) and f 0(1710) resonance state with large statistical significance n Very competitive measurements on peak position and width for f’ 2(1525) and f 0(1710) are done with interference fit and compared well with the PDG values End C. Zhou (Mc. Gill Univ. ) ECT *– Trento, February 25 -29, 2008 19