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SND new results and opportunities

SND new results and opportunities. Alexey Kharlamov. Budker Institute of Nuclear Physics (Novosibirsk, Russia) SND. Quarks in Hadrons and Nuclei, September, 2007. Outline. 1. SND and VEPP-2M Collider complex 2. New results on e + e -  K + K -  3. New results on e+e-  K S K L 

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SND new results and opportunities

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  1. SND new results and opportunities Alexey Kharlamov Budker Institute of Nuclear Physics (Novosibirsk, Russia) SND Quarks in Hadrons and Nuclei, September, 2007

  2. Outline • 1. SND and VEPP-2M Collider complex • 2. New results on e+e-K+K- • 3. New results on e+e-  KSKL • 4. New results on e+e-  • VEPP2000 project • The project of the nucleon form factor measurements • Summary

  3. VEPP-2M Collider Complex • VEPP-2M collider: 0.36-1.4 GeV in c.m., L31030 1/cm2s at 1 GeV • Detectors CMD-2 and SND: 60 pb-1 collected in 1993-2000 • All major hadronic modes are measured: e+e-  2, 3, 4, KK, .. e+e- , ,  Still a lot of data to analyze !

  4. Spherical Neutral Detector 1 – VEPP-2000 vacuum chamber, 2 – tracking system, 3 – aerogel counters, 4 – electromagnetic calorimeterNaI(Tl), 5 – vacuum phototriodes, 6 – absorber, 7-9 – muon system, 10 – VEPP-2000 phocusing solenoid

  5. e+e–→K+K- cross section stat. error 4.4% syst. error 5.2% Lto t= 8690 nb-1 background e+e-→+- PID e+e-→ e+e- Etot, θ, PID e+e-→μ+μ- muon syst.

  6. PID parametrs

  7. e+e–→KSKLprocess • KL-meson: • Decay length: • L= γβcτ=3,5÷ 14,9 metE0=510÷690 MeV • Nuclear length inNaI: • Lяд ≈ 33 ÷ 42 smatE0=510÷690 MeV • Number of clusters in calorimeter: • 0 – 17%, 1 – 42%, 2 – 27%, 3 – 9 %, ≥4 – 5% KL KL e+ e+ e– e– • KS → 2πo → 4γ: • Decay length ofKS meson: • L = γβcτ = 0,6÷2,6 sm atE0=510÷690 MeV • Number of clusters in calorimeter: • 4, (3 – ~5,6% МС) KS → 2πo → 4γ KS → 2πo → 4γ background e+e– → KSKLγISR 400 < Mrec<550 MeV e+e– → ηγγISR e+e– → ωπ0, ω→π0γ e+e– → ηγ

  8. e+e–→KSKLcross section KS → 2πo → 4γ ρ,ω, φ + φ(1680) : χ2/ndf = 19,6/21 ρ,ω, φ + ρ(1450) : χ2/ndf = 19,2/21 ρ,ω, φ + ρ(1700) : χ2/ndf = 19,3/21 ρ,ω, φ : χ2/ndf = 44,6/22 stat. error 4.1% syst. error 2.9 - 5.3% Lto t= 9100 nb-1

  9. Isovector form factor coming soon  φ(1680): M=1655±16 МэВ Γ = 161±32 МэВ σ = 0,68±0,13 нб ρ,ω,φ,φ(1680)

  10. e+e–→cross section Bρ=(2.40±0.25±0.07)×10-4 Bω= (4.63±0.46±0.13) )×10-4 B= (1.362±0.019±0.035) )×10-2 → +-0 syst. error 2.8% →30 syst. error 2.9% Lto t= 27.8 pb-1

  11. June2006 VEPP-2000 June 2007 CMD-3 First injection (RF off) Febr.15, 2006 per detector per year SND Total integrated luminosity with all detectors on VEPP-2M ~ 70 pb-1

  12. BaBar-ISR measurement summary σ~5% Physics program at VEPP-2000 1. Precise measurement of the quantity R=(e+e-- > hadrons)/ (e+e-->+--) 2. Study of hadronic channels: e+e-- > 2h, 3h, 4h …, h= ,K, 3. Study of ‘excited’ vector mesons: ’, ’’, ’, ’,.. 4. CVC tests: comparison of e+e-- > hadr. (T=1) cross section with -decay spectra 5. Study of nucleon-antinucleon pair production – nucleon electromagnetic form factors, search for NNbar resonances, .. 6. Hadron production in ‘radiative return’ (ISR) processes 7. Two photon physics 8. Test of the QED high order processes 2->4,5

  13. Monte Carlo time spectra of n nbar events in SND calorimeter MC p pbar DC trigger efficiency Nucleon-antinucleon pair production Antineutrons give stars inside calorimeter Antiprotons annihilate in material before drift chamber, Ek<7Mev

  14. Nucleon production cross section C~1 at Tkin. 1 MeV At the threshold we have s=4MN2 and GE=GM, if GE =GM=0.3, then At s=0: GEp(0)=1, GEn(0)=0, GMp(0)=2.79, GMn(0)=-1.79 Radiative correction: For T=1Mev e-n=0.62; For T=50 Mev e-n=0.82;

  15. e+e-→ , MC distribution over cosθ. Extraction of GM, GE GM gives (1+cos 2q ), GE gives (1-cos 2q ). With T =10MeV, N=3000 ev., ratio GE /GM is measured with 8% accuracy Estimates of statistics at threshold : Instant luminosity – - 0.1 nb-1 sec-1 Time – 107 sec Integrated luminosity – 1 fb-1 Cross section - 0.7 nb Detection efficiency – 0.15 Number of events: 105 GE /GM – with 5% statistical accuracy, 10 bins

  16. Conclusion • K+K- and KSKL production cross sections have been measured with best accuracy today, now it is possible to separate isovector and isoscalar parts of kaon form factor • Most precise measurement of ηγ cross section have been performed, ρ,ω,φ branching ratios are extracted • VEPP-2000 has got first collisions, a lot of resonances are waiting to be measured • SND upgraded, nucleon form factors coming soon 

  17. SND old version

  18. NaI(Tl) calorimeter Energy resolution: Angular resolution: • Calorimeter parameters • 1680 crystals • VPT readout • 3 spherical layers • 3.5 tons • 13.5 X0 • 90% 4 •  x =90 x 90 • 0 - mass =8,6 MeV

  19. Cryogenic Magnetic Detector-3 1 – vacuum chamber 2 – drift chamber 3 – electromagnetic calorimeter BGO 4 – Z–chamber 5 – CMD SC solenoid 6 – electromagnetic calorimeter LXe 7 – electromagnetic calorimeterCsI 8 – yoke 9 – VEPP-2000 solenoid

  20. Most important SND physical results • Electric dipole radiative decays (1020) f0(980) and (1020)  a0(980)  • were observed at the first time. Relatively large rate of these processes supports • the model of 4-quark structure of the lightest scalars a0 andf0 . • The measured ,00 branching ratios in 3-4 times exceed VDM • predictions. The decay 00 was observed for the first time. Its branching • ratio can be explained by -meson contribution. For the 00 decay • there is no theoretical explanation. • The branching ratios of radiative magnetic dipole decays , ,   0 ,  were measured with high accuracy - test of VDM and quark model. • The branching ratios of 0, + decays were measured. 0 decay was observed for the first time - study of OZIand isospin violation. • In the cross section of the e+e+0 process the structure near 1200MeV was observed, which is direct manifestation of  (1400) resonance. • The e+e4,0 cross sections were measured with highest accuracy – (g-2) and CVC test. Work in progress: • e+e+ • e+eKSKL, K+K simultaneous fit • e+ee+e • e+e+ 2E > 1GeV • ,   +

  21. Data Approximation Vector Dominance Model KS e+ V=ρ,ω,φ,… γ* e– KL SU(3) JPC=1––

  22. Recoil mass of KS meson 2E0=1,04÷1,05ГэВ 2E0=1,06÷1,09ГэВ 2E0=1,1÷1,18 ГэВ 2E0=1,2÷1,38 ГэВ KLγ KL e+e– → ωπ0, ω→π0γ

  23. e+e–→KSKLprocess • √s > 1,12 ГэВ • Etot < 0.5 √s • MC precision~20% • √s > 1,2 ГэВ • NNP < 7 • Etot ≥ 0.5 √s • MC precision~5% Beam background e+e– → ωπ0, ω→π0γ

  24. Detection Efficiency ε( 1,15 ГэВ ,Eγ) ε( 1,27ГэВ ,Eγ) ε(1,38ГэВ ,Eγ) ε(E,Eγ=0)

  25. background e+e– → KSKL, KS→20 e+e– → ωπ00, ω→π0γ e+e– → 00γ e+e– → 2(3)γ 400 < Mrec< 600 MeV

  26. Time resolution NaI(Tl)  2.8 ns Electronics is under upgrade Time resolution of the whole NaI(Tl) calorimeter s<1 nsec at DE~0.5 GeV is expected.

  27. SND subsystems • NaI(Tl) calorimeter - ~50% new phototriodes • Тracking system – new • Аerogel cherenkov detector – new subsystem • Electronics – ~50% new • Data acquisition system – 90% new • Data processing – 90% new • Antineutron detector –new subsystem

  28. Cross section predictions for SND

  29. Exclusive channels of e+e- annihilation into hadrons

  30. e+e- annihilation with kaon production e+e- > K+ K-- e+e- > KS K+-- e+e- > KS KL Totalintegrated luminosity in the range 2E=1.4-2.0 GeV is 5 /pb.

  31. Light vector meson table Nearly all excitations are within VEPP-2000 range Table of masses, widths (1450): M=1465 25; =310 60, (1700): M=1700 20; =240 60, (2150): M=2149 17; =363 50, (1420): M=1419 31; =174 60, (1650): M=1649 24; =220 35, (1680): M=1680 20; =150 50, Main decay channels … (1450) -> 4 , , , .. (1700) -> 2, 4 , , .. (1420)-> 3, .. (1700)-> , .. (1680) -> KK, KK*, .. Summary for VEPP-2000: with 1 fb-1 the knowledge of vector excitations can be improved to the level of knowledge of (770), (782), (1020)

  32. Indications on possible resonance structure near NNbar threshold Diffr.photoproduction,E687, BNl, 2001 +Be->6+Be Antineutron-proton cross section • Fitting of 6 • mass spectrum • M = 1911 +- 4 MeV, • = 29 +- 11 MeV, • = 62 +- 12 deg. Ares/Anres=0.31+-0.07 2/ND = 1.1 ------------------ JPCIG = 1- - 1+ Models: 1.vector hybrid 1.9 GeV, 2.vector glueballs  2 GeV, 3.NNbar resonance • Fitting results: • M 1881 (+- 1MeV) •  4 (+- 2MeV) Above threshold !! Isovector (nbar p) ! If L=0 (S-wave) S(spin)=0,1 JPC = 0-+ or 1- - If 1- - -> VEPP-2000  3! • Conclusions for VEPP-2000: • if Nnbar state is above threshold, it could be • seen in e+e->Nnbar and in e+e->hadrons cross section; • if below – only in e+e->hadron cross section.

  33. Physical background for NN in SND (MC) Example of suppression (MC) Physical background e+ e--> KSKL, 0.1nb e+ e--> KSKL0, 1nb   e+ e--> 0->00, 0.1 nb   e+ e--> ,->neutrals,10 pb   e+ e--> hadrons->neutrals,<0.1   e+ e--> 4,5, (QED),0.1 nb For comparison, e+e-->n nbar cross section 1 nb The most physical background comes from the reactions with KL production. KLinteractions and decays in flight look similar to nbar because they give ‘stars’ outside the detector center. cut Event momentum Event energy

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