VV process. Liu Zhiqing ( 劉智青 ) IHEP, Beijing. On behalf of Belle Collaboration.

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1 VV process Liu Zhiqing ( 劉智青 ) IHEP, Beijing On behalf of Belle Collaboration zqliu@ihep.ac.cn The 9th Chinese HFCPV Hangzhou, 12th, Oct, 2011.

2 Outline 1. Introduction. 2. Belle experiment. 3. reaction. 4. Charmonium-(like) state. 5. Summary. 2

3 I. Introduction Quantum number constraint: Q=0, C=+, J P =0 +, 0 -, 2 +, 2 - Experimental measurements report: interaction in an e + e - Collider. Hadron production process: 1. High virtuality: large Q 2, double tag or single tag method. 2. Quasi-real photons: small Q 2, Q 2 <<W 2 Q 2 <<E 2 QCD, non-tag method, characteristic Pt* distribution. *Br( f) or f cross section, coupling constant, provide info of hadron structure. Hunt new hadrons, study hadron structure, test QCD properties and form factors measurement 3

4 I. Introduction 1. X(3915) was discovered in J/ (PRL104,092001) Evidence for X(4350) in J/ (PRL104,112004) Good candidate for molecule and tetraquark state. is promising: only replace cc to ss. 2. VV is good channel for 4-quark state search. Consist of VV pair and well glued to system, lot of models: MIT bag (Sov. Phys. Usp. 34,1991) Measured by L3 and ARGUS. Enhancements have been observed above threshold, what s the nature of them? has rough measurement, no data yet. 3. It s time to further study 4

5 II. Belle experiment ISR, Two-photon 5

6 VV ( ) 6

7 How to extract signal events? 870 fb -1 K + K -, L=870fb -1, Y(nS) n=1,,5 1. Quasi-real photon: Double un-tag method. 2. Signal events: Pt* (vector sum) distribution peak at zero. 3. Background events: relative large Pt* value. 4. Pure signal events is extracted through fit Pt* distribution with smooth background shape in each mass bin. 5. Direct final state background is estimated through sideband events. 7

8 VV mass spectrum (~2<W<3.8GeV) (a) c (b) c2 c0 c (c) c2 c0 1. (a) (b) (c) mass spectrum in two-photon process. 2. Background is estimated from sideband, i.e. 4K, 6 3. Obvious enhancement below 2.8GeV/c 2 New state? Threshold effect? or QCD production? 4. Charmonia is observed significantly, more precise result is expected. 8

9 Spin-Parity results for M(VV)<2.8GeV/c 2 (a) (b) (c) 0+ and and 2-0+ and 2+ Angle definition: 1. Five kinematically independent angles: cos, cos *,cos **, *, ** 2. Transversity angle: T = *+ ** ; Polar-angle product: =(sin *) 2 (sin **) 2 3. (a)4 4 (b)5 5 (c)10 10 bins. Fig (a) shows distribution in each T bin, i.e. distribution while T [0.0.25) for first 4 bins and similarity for others. 4. Fit 2-D angle distribution f( T, ) to extract different J P components. (a). Can not separate 0 + S-Wave or 2 + S-Wave, best fit give 50%+50% (b). 0 + S-Wave(34%) and 2 - P-Wave(66%) (c). 0 + S-Wave(35%) and 2 + S-Wave(65%) 9

10 Cross section measurement (a) (b) (c) 1. (a) (b) (c) cross section together with different J P component contribution. 2. TREPS to generate two-photon events and calculate two-photon luminosity. 3. Efficiency is got through MC simulation and re-weighed according to mass dependent spin-parity analysis result. 4. Systematic would be in ~10%-13% level. 10

11 Nature of these broad peaks? 1. New state? No known existing states in these energy region coupling to VV. Each enhancement have mixed spin-parity, not a single state? two state? 2. Threshold effect? Decreasing cross section increasing phase space? 11

12 Nature of these broad peaks? 1. New state? No known existing states in these energy region coupling to VV. Each enhancement have mixed spin-parity, not a single state? two state? 2. Threshold effect? Decreasing cross section increasing phase space? Answer is NO! pqcd: W -n (n=8~10) n 12

13 Nature of these broad peaks? 1. New state? No known existing states in these energy region coupling to VV. Each enhancement have mixed spin-parity, not a single state? two state? 2. Threshold effect? Decreasing cross section increasing phase space? 3. QCD production? pqcd can make some prediction in high energy region (e.g arxiv: Chernyak). Complicated question near threshold. 4. Other information can help us identify these state? e.g d /d cos 13

14 Charmonium results (a) (b) First evidence (3.8 ) of c (c) 1. Clear c, c0 and c2 signal in (b) mode and first evidence for (c) c 2. Measurement of *Br(VV) Consistent with previous results in EPJC53,1(2008) 14

15 IV. Charmonium-(like) states 15

16 confirm c2 (2P) state PRL96,082003(2006) 395 fb -1 (J=2, =2) (J=0) M(Z(3930)) = MeV/c 2 (Z(3930))= MeV *Br(Z DD)= kev 384 fb -1 PRD81,092003(2010) (J=2, =2) (J=0) M(Z(3930))= MeV/c 2 (Z(3930))= MeV *Br(Z DD)= kev 16

17 confirm c2 (2P) state PRL96,082003(2006) 395 fb -1 M(Z(3930)) = MeV/c 2 (J=2, =2) (Z(3930))= MeV *Br(Z DD)= kev (J=0) Discovered by Belle and confirmed by BaBar in Belle and BaBar results are consistent! Spin=2 => Z(3930)= c2 (2P) 384 fb -1 PRD81,092003(2010) (J=2, =2) (J=0) M(Z(3930))= MeV/c 2 (Z(3930))= MeV *Br(Z DD)= kev 17

18 confirm c2 (2P) state PRL96,082003(2006) 395 fb -1 M(Z(3930)) = MeV/c 2 (J=2, =2) (Z(3930))= MeV *Br(Z DD)= kev (J=0) Discovered by Belle and confirmed by BaBar in Belle and BaBar results are consistent! Spin=2 => Z(3930)= c2 (2P) PDG 2011 s Summary Table 384 fb -1 PRD81,092003(2010) (J=2, =2) (J=0) M(Z(3930))= MeV/c 2 (Z(3930))= MeV *Br(Z DD)= kev 18

19 confirm c2 (2P) state PRL96,082003(2006) 395 fb fb -1 PRD81,092003(2010) M(Z(3930)) = MeV/c 2 (J=2, =2) (Z(3930))= MeV *Br(Z DD)= kev (J=0) Discovered by Belle and confirmed by BaBar in Belle and BaBar results are consistent! Spin=2 => Z(3930)= c2 (2P) Where is c0 (2P) and c1 (2P)? (J=2, =2) PRD72,054026(2005) Possible in (3S,2D) radiative transition? (J=0) M(Z(3930))= MeV/c 2 (Z(3930))= MeV *Br(Z DD)= kev 19

20 The nature of X(3915) PRL104,092001(2010) J/ l + l - Two-photon production Possible J P =0 +,2 + c2 (2P) has been confirmed experimentally. X(3915) 694fb -1 J Only background fit New decay mode of c2 (2P)? Can not be c1 (2P)? c0 (2P) candidate? Or new state if X(3872)= c0 (2P)? 20

21 Evidence of X(4350) in J/ PRL104,112004(2010) 825fb -1 X(4350) N= J/ Motivated by Y(4140) in B YK J/ K found by CDF. [PRL102,242002(2009)] Belle try to search this Y(4140) both in B decay and reaction. 1. No signal for Y(4140) 2. But observed evidence for X(4350). M= MeV/c2 = MeV 21

22 Evidence of X(4350) in J/ PRL104,112004(2010) 825fb -1 X(4350) N= What s it? Molecule or tetra-quark state? J/ J.Phys.G37:075017(2010) The answer may be clear in Super-B period! 22

23 Summary 1. VV cross section is measured. 2. Significant enhancement is observed near threshold, how to understand them? 3. Charmonium-(like) state searching give us exciting results and is still ongoing. Thank You! 23

24 V. PP (P= 0 ) 24

25 PRD82,114031(2010) 393fb -1 f 2 (1270) f 2 (1525) f 2 (X)? 1. Excited light hadron produced, f 2 (1270) 25

26 PRD82,114031(2010) 393fb -1 PRD79,052009(2009) W -n fit 1. Excited light hadron produced, f 2 (1270) 2. pqcd can make prediction in higher energy region, ~W -n 26

27 PRD82,114031(2010) 393fb -1 PRD79,052009(2009) W -n fit 3. Ratio ) 27

28 PRD24,1808(1981) PRD82,114031(2010) 393fb -1 PRD79,052009(2009) W -n fit 3. Ratio ) 0, PRD80,032001(2009), PLB615,39(2005) K + K, PLB615,39(2005) KsKs, PLB651,15(2007) 28

29 Angle definition 29