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First results from SND at VEPP-2000

Budker Institute of Nuclear Physics. First results from SND at VEPP-2000. S. Serednyakov On behalf of SND group. VIII International Workshop on e + e - Collisions from Phi to Psi, PHIPSI11, Novosibirsk. VEPP -2000 Collider. Main parameters: collision time – 82 ns beam current – 0.2 A

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First results from SND at VEPP-2000

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  1. Budker Institute of Nuclear Physics First results from SND at VEPP-2000 S. Serednyakov On behalf of SND group VIII International Workshop on e+e- Collisions from Phi to Psi, PHIPSI11, Novosibirsk

  2. VEPP-2000 Collider • Main parameters: • collision time – 82 ns • beam current– 0.2 A • bunch length – 3.3 cm • perimeter– 24.4 m • Energy spread– 0.7 MeV • x≃ z =6.3 cm • L ≃ 1032cm-2c-1 (2E=2.0 GeV) • L=1031cm-2c-1 (2E=1.0 GeV) Achieved (2011): L~0.8·1031cm-2c-1 (2E=1.0 GeV) L~2·1031cm-2c-1 (2E=2.0 GeV) designed IL(1 y) = 1 fb-1 . SND - PHIPSI11

  3. SND for VEPP-2000 (1993, VEPP-2M) 1 – beam pipe, 2 – tracking system, 3 – aerogel Cherenkov counter , 4 – NaI(Tl) crystals, 5 – phototriodes, 6 – iron absorber, 7–9 – muon detector, 10 – focusing solenoids. NIM A449 (2000) 125-139 SND - PHIPSI11

  4. SND at VEPP-2000 SND - PHIPSI11

  5. SND at VEPP-2000 NaI(Tl) calorimeter Drift chamber Aerogel Cherenkov counter SND control room Iron absorber S.C. solenoid SND - PHIPSI11

  6. SND general parameters Calorimeter: 1632 NaI(Tl) crystals, VPT readout, 13.5 X0, W- 90% 4,  x =9º x 9º Tracking system: 9-layer cylindrical drift chamber, 24-jet cells, W - 94% 4, 90% Ar + 10% CO2 PID (dE/dX) p<300 MeV/c Energy resolution: Angular resolution: Angular resolution: SND - PHIPSI11

  7. Particle ID, aerogel Cherenkov counter n=1.13, W~60% 4p Cherenkov signal vs pion momentum (pions from e+e-→ π+π-π0π0 ) SND - PHIPSI11

  8. Experiments 2010 and 2011,preprint BINP 2011-21 SND - PHIPSI11

  9. Experiments 2010 and 2011,preprint BINP 2011-21 SND - PHIPSI11

  10. VEPP-2000 Physical program • 1. Precise measurement of the quantity R=(e+e–→ hadrons) / (e+e–→+-) • 2. Cross section measurements of the processes of e+e- -annihilation into hadrons:e+e– → 2h, 3h, 4h …, h= ,K,, … • 3. Study of excited vector states: ′, , ′, , ′,.. • 4. CVC tests: comparison of e+e–→ hadrons cross section with → ντ+ hadronsdecay spectra • 5.Study of nucleon - antinucleon pair production and nucleon electromagnetic form factors, search for NNbar resonances. • 6. Hadron production in radiative return (ISR) processes: e+e–→γ*γ, γ* → hadrons • 7. Two photon physics e+e–→ e+e– + hadrons • 8. Test of high-order QED 2→ 4, 5 SND - PHIPSI11

  11. e+e-→ ωπ0 → π0π0γ,2010 scan, preprint BINP 2011-21 • Selections: • -at least 5γ, • - no charged particles, • energy deposition -> Ebeam • kinematic fit: χ25γ<30; • χ2π0π0γ−χ 25γ<10; • |Mπ0γ− Mω|<100 MeV Fit: sum of ρ(770) and ρ(1450) contributions SND - PHIPSI11

  12. Mπ0γ e+e-→ ωπ0 → π0π0γ, 2010 scan Mp0 SND - PHIPSI11

  13. e+e-→ π+π-π0π0 , 2010 scan • Selections: • - at least 2 charged • particles and 4 photons • kinematic fit: χ2< 40; • Mπ0 = 70-200 MeV Statistical errors only SND - PHIPSI11

  14. e+e-→ π+π-π0π0, 2010 scan p0 masses m12 m34 SND - PHIPSI11

  15. e+e-→ π+π-π0 , 2010 scan Selections: – 2 or more tracks – 2 or 3 γ – Δφch.part.>10° – ΔΩch.part.>40° Total EMC energy – (0.3-0.8)Ebeam Kinematic fit: π+π–γ γ - χ2< 30 SND - PHIPSI11

  16. e+e-→ π+π-π0 , 2010 scan View ofdata e+e-→π+π- π0event Mp0 SND - PHIPSI11

  17. e+e-→ ηπ+π- , 2010 scan Selections: – 2 charged particles – 2 photons – θcharged (22.5°-157.5°) – θphoton (36°-144°) kinematic fit (π+π–γ γ): χ2< 20 mgg mpp SND - PHIPSI11

  18. C~1at T.~1 MeV At s->∞ GM falls as q-4 At s=4MN2 GE=GM SND - PHIPSI11

  19. Events features: • no signal from • “star” from annihilation point of in Cherenkov counters or calorimeter Picture of expected event e+e-→ n nbar, 2011 scan SND - PHIPSI11

  20. e+e-→ n nbar, 2011 scan Suppression of background Type of bkgd Source of bkgd Suppression cuts Nnbar detection efficiency ~ 20-30% SND - PHIPSI11

  21. e+e-→ n nbar, 2011 scan, cosmic bkgd subtraction be=n1/n0 b0=nc1/nc0 Nx=(1+be)(b0N0-N1)/(b0-be) n0 nc0 n1 nc1 Cross section: sexp= Nx/L2ged sMC=NxMC/LMCed LMC= N0MC/sMC Nx N1 N0 SND - PHIPSI11

  22. e+e-→ n nbar, 2011 scan Experimental event SND - PHIPSI11

  23. e+e-→ n nbar, 2011 scan After cosmic bkgd suppression using event time ( effect + phys. bkgd) Estimated background from physical processes(pp + ggg) SND test cross section s=0.04+-0.2 nb FENICE data Physical background – 1 – e+e-→ γγγ, σ~ 0.4 nb, 2 – e+e-→ ppbar, σ ~ 0.03 nb s=0.78+-0.2 nb threshold SND - PHIPSI11

  24. Events features (near threshold): • No signal from • “star” from annihilation point • at beam pipe • Events features (above the threshold): • charged track and no energy deposition for • charged track and “star” from annihilation point in Cherenkov counter for e+e-→ p pbar, 2011 scan Picture of expected event near threshold SND - PHIPSI11

  25. e+e-→ p pbar, 2011 scan Selections (near threshold): – 3 or more tracks with vertex at beam pipe, – energy in EMC > 650MeV Experimental event SND - PHIPSI11

  26. e+e-→ p pbar, 2011 scan Selections (above threshold): – 2 or more tracks, – 2 collinear tracks with large dE/dx, – EMC energy > 650MeV, Experimental event SND - PHIPSI11

  27. e+e-→ p pbar, 2011 scan − SND − BaBar1 Very preliminary e+e−→ pp cross section, SND preliminary result [1] B.Aubert et al., Phys.Rev.D73 (2006) 012005 SND - PHIPSI11

  28. Conclusions & Plans • First data taking runs have been performed with SND at VEPP-2000 in the range 1.0 − 2.0 GeV with ~ 30 inv. pb • Preliminary results on hadron cross sections have been obtained ( e+e-→ ωπ0,π+π- π0,π+π- π0 π0, η π+π-, ppbar, nnbar) • To analyze the full recorded statistics • To upgrade the SND electronics and reconstruction procedure • To continue data taking runs SND - PHIPSI11

  29. Thank you SND - PHIPSI11

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