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Study of Double Charmonium Production in Continuum

Study of Double Charmonium Production in Continuum.  *. Shuwei Ye and Xinchou Lou U.T. Dallas BaBar Collab meeting, Dec 6, 2006. Outline. Motivations & method Previous measurements X(3940) by Belle Preliminary update on Preliminary result on Summary & plan. Motivation & History.

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Study of Double Charmonium Production in Continuum

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  1. Study of Double CharmoniumProduction in Continuum * Shuwei Ye and Xinchou Lou U.T. Dallas BaBar Collab meeting, Dec 6, 2006

  2. Outline • Motivations & method • Previous measurements • X(3940) by Belle • Preliminary update on • Preliminary result on • Summary & plan Shuwei YE

  3. Motivation & History Motivation • Belle/BaBarobserved surprising large cross sections for double , about an order of magnitude higher than NRQCD prediction • To confirm Belle’s X(3940) reported in double events • Good place to search for new statesinaccessible from direct e+e- annihilations. History • We analyzed Runs 1-3 data and published result for mRec<3.8 GeV/c2 • Glenn Williams, graduate Student, took over this analysis due to my important analysis on ISR J/, but left in December 2005. • I continued/extended this analysis in August 2006. Shuwei YE

  4. Method: Recoil Mass Recoil mass to the reconstructed  : recoiling charmonia: c , c , c(2S), ?J/, (2S) C = +1 C = -1 C = -1 is allowed if a swap of c and between 2 * Shuwei YE

  5. e+e- J/ cc PRL 89, 142001 PRD 72, 031101 • Belle found double charmonium final states:(J/, y(2S))(c, c) No signal of C = -1 states in the J/ recoil mass spectrum • J=0 & C=+1 only accompanying J/ • confirmed by BABAR Cross-sections (fb) Shuwei YE

  6. X(3940) in e+e- J/ cc at Belle Double charmonium production provides a new approach to search for high-mass charmonia Belle found c(3S) candidate (X3940) in ee J/ X(3940) c(2S) c(1S) 350 fb-1 c0 above DD and D*D thresholds hep-ex/0507019 M = (3943  6 6) MeV/c2  < 52 MeV (90% C. L.) Stat. significance 5.0  Shuwei YE

  7. Original Analysis Runs 1-3: 124 fb-1 • Candidates: J/  l+ l • PID on e/ • J/y mass windows e+e-: [-50, +30] MeV/c2 (with bremsstrahlung recovery) +-: [-30, +30] MeV/c2 • Cosine oflepton angle: |cosql+(J/y)|<0.90 Apply J/ymass-constraint to l+ l-to improve p*(J/y) resolution • Other selection criteria • nChg(GTL)>2 in the recoil side: to suppress QED • EQED= EEMC+ pmiss < Ebeams –1.0 GeV to further suppress QED bkg • (2S) veto • to suppress feed-down Shuwei YE

  8. Update on e+e- J/ cc with More Data J/ee,  ? X(3940)? c’ c Many from (2S) feeddown c0 Use original selection criteria More data: Runs 1-5, 386 fb-1 Shuwei YE

  9. e+e- J/ cc (nChg=2) Can we pick up nChg(GTL)=2 events? J/ee • Similar as before except • nChg(GTL)=2 in the recoil • No EQED cut • |cos*((2S))-0.05|<0.90 & noE*>3.0 GeV veto • to suppress ISR events J/ Shuwei YE

  10. e+e- J/ cc (nChg2) X(3940)? J/ee(>2) J/(2) J/ (2) Add up nChg>2 and nChg=2 c’ c0 c Shuwei YE

  11. New: e+e- cc (2S)J/ X(3940)? No significant contamination from higher charmonia to allow all events in the recoil side nChg>2 in recoil (2S)J/ • Selection criteria • Same selection of J/l+ l • (2S) mass window: 5 MeV/c2 • No EQED cut • |cos*((2S))-0.05|<0.90 & noE*>3.0 GeV veto • to suppress ISR events ? c0 c’ c All nChg Shuwei YE

  12. New: e+e- cc (2S)l+ l No significant contamination from higher charmonia J/ee • Selection: (2S)l+ l • Similar with J/l+ l J/ Shuwei YE

  13. e+e- J/ cc + (2S) cc ? c’ c c0 X(3940)? • J/ee (nCh>2) • J/ (nCh2) • (2S)J/ • (2S)(nCh>2) Sum of mRec against J/ and (2S)J/ Shuwei YE

  14. Summary and Plan • Evidence for X(3940) found in both eeJ/ and ee(2S) with current 386 fb-1 data • Significant signals foree(2S) c, (2S) c0, (2S)c(2S) • (2S)l+ l channel is challenging: (2S) is usable • Possible structures(?) above X(3940) in the recoil mass spectra • Prepare PDF and perform fits to the recoil mass spectra • Report result on X(3940) in winter conference • Publication • Further study on the higher recoil mass region and J/ +D pairs Shuwei YE

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