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Meson production in the ISR reactions at BaBar

Meson production in the ISR reactions at BaBar. E.Solodov for BaBar collaboration Budker INP SB RAS, Novosibirsk, Rusia. MESON2012, Crakow, Poland. Motivation. Low energy e + e  cross section dominates in hadronic contribution to a m = (g-2)/2 of muon

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Meson production in the ISR reactions at BaBar

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  1. Meson production in the ISRreactions at BaBar E.Solodov for BaBar collaboration Budker INP SB RAS, Novosibirsk, Rusia MESON2012, Crakow, Poland

  2. Motivation • Low energy e+ecross section dominates in hadronic contribution to • am = (g-2)/2 of muon • Direct e+edata in 1.4 - 2.5 GeV region have very low statistic • new inputs for the hadron spectroscopy at low masses and charmonium region • ISR at BaBar gives competitive statistic • BaBar has excellent capability for ISR study • All major hadronic processes are under study • e+e  2, 2, 2K, 2p, cLc • e+e  3 • e+e  2( • e+e 2( • e+e   • e+e   • e+e  • Some reactions are being updated to full BaBar data with ~500fb-1 ISR at BaBar, E.Solodov

  3. BaBar measurements summary 0.5-2% syst. errors 4-15% syst. errors To calculate R in the energy range1-2 GeVthe processes +-30, +-40, K+K-, KSKL, KSKL, KSK+-0are under study. The +-20 is still preliminary. Work is in progress. ISR at BaBar, E.Solodov

  4. e+e- K+K-p+p-,K+K-p0p0 We present new preliminary results on the study of the processes: e+e- K+K-p+p- e+e- K+K-p0p0 e+e- K+K-K+K- (arXiv:1103.3001v1) Submitted to PRD Our previous publication, based on part of the data: B. Aubert et al. (BaBar Collaboration), Phys. Rev. D76, 012008 (2007). ISR at BaBar, E.Solodov

  5. e+e- K+K-p+p-,K+K-p0p0 In the new study, base on full BaBar data set (454 fb-1): We know many ISR processes for better control of the background We know tracking and photon reconstruction efficiency with better accuracy. More intermediate states are separated. All above allows to decrease systematic uncertainties. Important for g-2 BABAR K+K-p0p0 BABAR K+K-p+p- • Systematic error 4% (was 8%) • Error dominated by acceptance • Still no other measurements • Systematic error 7% (was 11%) ISR at BaBar, E.Solodov

  6. Kaon substructures for K+K,00 Charged combinations from K*(892)0 bands K*0(892) K1(1270) K2*(1430)0 K1(1400) ? Cross section dominates by K*0(892)Kfinal state. BUT….. K1(1270,1400) KK, K , and K1(1270,1400) Kr(770) are seen. ISR at BaBar, E.Solodov

  7. Kaon substructures (2) Count number of K*(892)0and K2*(1430)0 by fitting K+p-mass in every 40 MeV bin of K-p+mass. Less than 1% of 2K2p events are from K*0(892) K*0(892) K*0(892)K2*(1430)0 + c.c. is seen, mostly from J/decay Br = (6.7  2.6 ) x 10-3 (PDG) Count number of K*(892)+ events fitting 40 MeV mass slice in K-p0mass Cross section dominates by K*(892)Kfinal state, the same as forK+final state, but ~30% (1750 ± 60) events are from K*(892)+K*(892)- - compare to <1% K*(892)0K*(892)0 from K+K-p+p-study (548 ± 263).No other structures are seen in K00 or K+K-0 . ISR at BaBar, E.Solodov

  8. Inclusive e+eK* K, K+Kcross sections Fit in every 0.025 GeV/c2 bin of 2K2 mass • N K*(892) = 53997  526 • m K*(892) = 893.2  0.2 MeV/c2 •  = 52.1  0.7 MeV • N K2*(1430) = 4361  235 • m K2 = 1427.4  1.9 MeV/c2 • = 90.2  5.6 MeV • In agreement with PDG Fit in every 0.025 GeV/c2 bin of 2K2 mass Mass and width of are fixed ISR at BaBar, E.Solodov

  9. Selection of (1020) K+K-p+p- K+K-p0p0 Nf0= 437 ± 75 Nf = 709 ± 30 Nf0= 83 ± 27 Nf = 3951 ± 91 f0(600) ? Number of fpp events are selected by fitting of f signal in 0.025 (0.04) GeV/c2 bin of 2K2p mass The f0(980) parameters are not shifted from PDG values – f0-ppinterference is small because of kinematics. ISR at BaBar, E.Solodov

  10. Cross sections for e+e , 00 f0(980) threshold J/ J/ 0.85<m(pp)<1.1 m(pp)<0.85 Cut m(pp)<0.85 completely removes structures above Ecm = 2 GeV !! And confirms Y(2175) structure if 0.85<m(pp)<1.1 GeV/c2 (next slides) ISR at BaBar, E.Solodov

  11. Decomposition of K+Kmass spectrum K+K K*0(892)K K+K  K2*0(1430)K Tables with cross sections (corrected for BF) are provided ISR at BaBar, E.Solodov

  12. Cross section for e+e  () VMD model description ISR at BaBar, E.Solodov

  13. Angles for e+e p+p- events S-wave for  (pp) S-wave for from f0(s) P-wave for KK from  K+ K K  f and pp system are in S-wave Pions in pp system are in S-wave Kaons from f are in P-wave (as expected)  e e+ f0    ISR at BaBar, E.Solodov

  14. Cross section for e+e ( Consider as quazi-two-body reaction with two particles in S-wave. Two possible resonances below 3 GeV can be described as: XS is corrected by: Br( K+K) =0.491 Br(f0) = 2/3 Phase space in S-wave ~ momentum for two particles: mi = m - narrow mj = m() - not narrow - use integral over  mass: BW(s) - describes  mass distribution ISR at BaBar, E.Solodov

  15.  mass distribution Describe m() as a sum of two Breit-Wigner functions normalized to unit (interference is small due to kinematics) • m1 = 0.972  0.002 GeV/c2 m2 = 0.692  0.015 GeV/c2 • 1= 0.056  0.011 GeV  = 0.538  0.038 GeV r = 0.32  0.03 - fraction of f0(980) Flatte approximation for f0(980) gives better fit with a little wider width: (and leave less room for f0(600)) ISR at BaBar, E.Solodov

  16. Cross section for e+e  (1) Option #1 - both resonances decay to f0(600) + f0(980)) P(s) integral has sum of bwf0 + bw m()<3.0 m()<0.85 P() = 0.32 The m()<0.85 selection completely removes second resonance! Model is wrong. Not a surprise - f0(600) has only u,d quarks, but f0(980) is ss or ssss ISR at BaBar, E.Solodov

  17. Cross section for e+e  (2) • Option #2 - first resonance decays to f0(600) , second to f0(980) - Belle paper. • Have two phase spaces: P(s)and Pf0(s) - integral uses one BW for each mode. m()<3.0 0.85<m()<1.1 m()<0.85 P() = 0.011 P() = 0.92 P() = 10-5 This approach cannot explain our data for the 0.85<m()<1.1 selection ISR at BaBar, E.Solodov

  18. Cross section for e+e  (3) Option #3 - first resonance decays to f0(600) (A1) and f0(980) (A2), second only to f0(980). m()<3.0 m()<0.85 0.85<m()<1.1 P() = 0.54 no fit! P() = 0.22 no fit! P() = 0.75 P() = 0.96 fit P() = 0.38 fit (1680)->f0 (1680)->f0 Fit of total XS automatically describes all m() selections. There is no physical reasons for (1680) not to decay to f0(980) and have large coupling… But no evidence for Y(2175) decay to f0(600) . ISR at BaBar, E.Solodov

  19. Our results for (1680) For e+e- f(1680) fpp we get: For e+e- f(1680) f f0(980) we cannot use expression • 0 = 0.678  0.062 nb • m = 1.733  0.015 GeV/c2 • = 0.300  0.040 GeV ee Bpp (42  2  3) eV Not clear how to present result To use g2f f0(980) /g2fpp ?How to calculate? (369 eV for KK* and 138 eV for fh ) ISR at BaBar, E.Solodov

  20. What we know about (1680) From 2010 PDG (only e+e- experiments): There is NO BF table – only “seen”. BaBar provides ee B for KK* and fh and fpp There are 4 photo-production (K+K- channel) and one pp (KSKp) experiments giving mass ~1740, and width ~0.1 GeV (but could be r(1700) as stated in PDG) Taking into account energy dependent width (“standard“ for recent low mass spectroscopy) makes mass ~50 MeV higher and 100-150 MeV wider width ISR at BaBar, E.Solodov

  21. Cross section for e+e f0(980), Y(2175) K+K + K+K  = 150/(61-2) P=10-8 • 0x = 0.093  0.023  0.010 nb • mx = 2.180  0.008  0.008 GeV/c2 • x= 0.077  0.015  0.010 GeV  = 60/(61-6) P=0.3 ee B f0 (2.3  0.3  0.3) eV 2 ln (L0/Lx) = sqrt (150 – 64) ~ 9.3  XS is corrected by: Br( K+K) =0.491 Br(f0) = 2/3 Br(f0) = 1/3 Good overall agreement with 670 fb-1 Belle data for K+K channel C.P.Shen et al. (Belle Collaboration), Phys. Rev. D80, 031101(R) (2009). A fit with free interference phase with continuum ISR at BaBar, E.Solodov

  22. Evidence of Y (2175) in K+K-f0 final state Y(2175) ff0 ? ff0 Possible nature of Y(2175): 1 –ssss,2 –f ’’ but no BR fpp, 3- Y(2175) is similar to Y(4260): Y(4260) = J/Y f0, Gee=5.5 eV Y(2175)= ff0, Gee=2.3 eV Raw pp mass No background subtraction ISR at BaBar, E.Solodov

  23. e+e- K+K-K+K- fK+K- selection J/ψ 1 ? 2 ? Y(2175) fK+K- dominates 1 3 ISR at BaBar, E.Solodov

  24. Accepted by PRD ISR at BaBar, E.Solodov

  25. ISR at BaBar, E.Solodov

  26. ISR at BaBar, E.Solodov

  27. J/S  2(+-),K+K00,K+K +-, 2(K+K) We measure Because of small systematic uncertainties in L (~1%) and efficiency (~3%) BaBar is competitive for measurements, where systematic errors dominate. (Plus new, never studied states!) ISR at BaBar, E.Solodov

  28. ISR at BaBar, E.Solodov

  29. J region for K+K-p+p-,K+K-p0p0, K+K-K+K- Small systematic errors allow BaBar to improve BF for major decay modes. ISR at BaBar, E.Solodov

  30. Summary • Analysis of 2(), K+K, K+K00,K+KK+Khas been performed using ISR and 454 fb-1 • The e+e- -> 2()cross section has been measured with 2.4% syst. errors • The K+K cross section has been measured with ~4% syst. errors • The K+K00cross section has been measuredwith ~8% syst. errors • Inclusive cross sections for K*(892)0, K2(1430)0, and r(770)0 are provided • It is shown, that K*0K*0production is suppressed, but K*+K*-is not. • Final states ,00and f0(980) (f0  ,00) are selected • A structure with m ~ 2.18 GeV/c2 and  ~ 0.08 GeV has been confirmed • in e+e f0(980) (f0  ,00) reactions with ~9  significance • The confirmation comes from BES and Belle. • Y(2175) state decays to  f0(980) but does not decay to  f0(600). • New final states (and f0(980)) have been observed for (1680) and parameters measured • J/ decays to 2(),K+K , K+K00,,00and f0(980)have been measured. • PRD paper is submitted. ISR at BaBar, E.Solodov

  31. ISR PEP-II e+e- collider, Babar detector E+ = 3.1 GeV, E- = 9 GeV BaBar PEP-II e+ DIRC SVT DCH EMC IFR ECM = M((4S))=10.6 GeV 2000 – 2008 yrs DL = 500 fb-1 N(B) = 109 e- - photon polar angle in c.m. ISR at BaBar, E.Solodov

  32.  phase space 2-body massless The observed  mass distribution used to calculated a phase space according to: ff0 where BW(s) - describes  mass distribution The observed  mass shape significantly differ from pure fpp three-body phase space and has ~150 MeV shifted threshold and fast rise, when ff0 channel is opening. fpp quazi-two-body phase space with no resonant structure. The  mass shape contribute only to phase space! ISR at BaBar, E.Solodov

  33. Width energy dependence First resonance is presumably (1680) with dominant decay to KK* + fh and we see ~5-10% in (1020)f0(600) mode - “standard” way for (s): - P-wave for K*K For second resonance we use: Using width depending on energy significantly changes the resonance parameters for wide resonances and has small influence to narrow resonances. ISR at BaBar, E.Solodov

  34. Cross section for e+e f0(980) 232 fb-1 454 fb-1 • 0 = 0.13  0.04 nb • m = 2.175  0.010 GeV/c2 • = 0.058  0.016 GeV  = - 2.57  0.30 rad. • 0 = 0.093  0.021 nb • m = 2.180  0.008 GeV/c2 • = 0.077  0.015 GeV  = - 2.11  0.24 rad.  = 37.6  = 60/(61-6) P(2)=0.3  = 159/(61-2)  = 80.5 Significance is sqrt(80.5 - 37.6) ~ 6.5  Significance is sqrt(150 - 64) ~ 9.2  XS is corrected by: Br( K+K) =0.491 Br(f0) = 2/3 Br(f0) = 1/3 ISR at BaBar, E.Solodov

  35. Cross section for e+e f0(980) ~ 670 fb-1 Belle data 454 fb-1 BaBar data • 0 = 0.077  0.018 nb • M = 2.156  0.011 GeV/c2 • = 0.109  0.022 GeV  = - 1.85  0.54 rad. • 0 = 0.094  0.023 nb • M = 2.179  0.008 GeV/c2 • = 0.091  0.019 GeV  = - 1.80  0.28 rad.  = 57/(44-6)  = 41(45-6) Threshold shifted by 40 MeV! - worse resolution? Error in scale? f0(980) mass is shifted to adjust. XS is corrected by: Br( K+K) =0.491 Br(f0) = 2/3 ISR at BaBar, E.Solodov

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