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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,

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Presentation on theme: "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,"— Presentation transcript:

1 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 Budker Institute of Nuclear Physics

2 19.09.2011SND - PHIPSI112 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 ≃ 10 32 cm -2 c -1 (2E=2.0 GeV) L=10 31 cm -2 c -1 (2E=1.0 GeV)  L(1 y) = 1 fb -1. designed Achieved (2011): L~0.8·10 31 cm -2 c -1 ( 2E=1.0 GeV) L~2·10 31 cm -2 c -1 ( 2E=2.0 GeV)

3 19.09.2011SND - PHIPSI113 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

4 19.09.2011SND - PHIPSI114 SND at VEPP-2000

5 19.09.2011SND - PHIPSI115 SND at VEPP-2000 Iron absorber S.C. solenoid SND control room Drift chamber Aerogel Cherenkov counter NaI(Tl) calorimeter

6 19.09.2011SND - PHIPSI116 SND general parameters Calorimeter: 1632 NaI(Tl) crystals, VPT readout, 13.5 X0,  - 90% 4 ,  x  =9º x 9º Energy resolution: Angular resolution: Tracking system: 9-layer cylindrical drift chamber, 24-jet cells,  - 94% 4 , 90% Ar + 10% CO 2 PID (dE/dX) p<300 MeV/c Angular resolution:

7 19.09.2011SND - PHIPSI117 Particle ID, aerogel Cherenkov counter Cherenkov signal vs pion momentum (pions from e + e - → π + π - π 0 π 0 ) n=1.13,  ~60% 4 

8 19.09.2011SND - PHIPSI118 Experiments 2010 and 2011, preprint BINP 2011-21 Energy Region, GeV Energy step, MeV Integrated luminosity, pb -1 scan20101.1-1.91005 scan20111.05-2.025

9 19.09.2011SND - PHIPSI119 Experiments 2010 and 2011, preprint BINP 2011-21 Beam currents, e +, e -, mA ~ 50, 50 Beam life time, hr ~2 SND trigger threshold ~ 100 MeV Trigger rateN cosm =130Hz, N beam ~ 100 Hz Trigger live time95% DCH rate 100 kHz Event size~7 kbt Luminosity monitoringe + e - >e + e -

10 19.09.2011SND - PHIPSI1110 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  → ν τ + hadrons decay 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 VEPP-2000 Physical program

11 19.09.2011SND - PHIPSI1111 e + e - → ωπ 0 → π 0 π 0 γ, 2010 scan, preprint BINP 2011-21 Selections: - at least 5γ, - no charged particles, -energy deposition -> E beam -kinematic fit: χ 2 5γ <30; χ 2 π0π0γ − χ 2 5γ <10; |M π0γ − M ω |<100 MeV Fit: sum of ρ(770) and ρ(1450) contributions

12 19.09.2011SND - PHIPSI1112 Mπ0γMπ0γ e + e - → ωπ 0 → π 0 π 0 γ, 2010 scan M0M0

13 19.09.2011SND - PHIPSI1113 Selections: - at least 2 charged particles and 4 photons - kinematic fit: χ 2 < 40; M π0 = 70-200 MeV Statistical errors only e + e - → π + π - π 0 π 0, 2010 scan

14 19.09.2011SND - PHIPSI1114 e + e - → π + π - π 0 π 0, 2010 scan  0 masses m 12 m 34

15 19.09.2011SND - PHIPSI1115 e + e - → π + π - π 0, 2010 scan Selections: – 2 or more tracks – 2 or 3 γ – Δφ ch.part. >10° – ΔΩ ch.part. >40° Total EMC energy – (0.3-0.8)E beam Kinematic fit: π + π – γ γ - χ 2 < 30

16 19.09.2011SND - PHIPSI1116 View of data e + e - → π + π - π 0 event e + e - → π + π - π 0, 2010 scan M0M0

17 19.09.2011SND - PHIPSI1117 e + e - → ηπ + π -, 2010 scan Selections: – 2 charged particles – 2 photons – θ charged (22.5°-157.5°) – θ photon (36°-144°) kinematic fit (π + π – γ γ): χ 2 < 20 m  m 

18 19.09.2011SND - PHIPSI1118 At s=4M N 2 G E =G M C~1 at T. ~1 MeV At s-> ∞ G M falls as q -4

19 19.09.2011SND - PHIPSI1119 Picture of expected event Events features: - no signal from - “star” from annihilation point of in Cherenkov counters or calorimeter e + e - → n nbar, 2011 scan

20 19.09.2011SND - PHIPSI1120 e + e - → n nbar, 2011 scan Suppression of background Cosmic bkgd Muon tracks in EMC, showers In EMC Muon system veto, r.f. time, Signature in EMC Beam bkgd Beam scattering on residial gas, Toushek effect High EMC threshold, Signature in EMC,  E=1000-1800 MeV Physical bkgd e + e -  2 , n , e + e -  e + e - (  ), e + e -  hadrons, No tracks in DCH, No central  in EMC, No E-P conservation, Type of bkgdSource of bkgdSuppression cuts Nnbar detection efficiency ~ 20-30%

21 19.09.2011SND - PHIPSI1121  e =n 1/ n 0  0 =nc 1 /nc 0 N x =(1+  e )(  0 N 0 -N 1 )/(  0 -  e ) n1n1 n0n0 nc 1 nc 0 N1N1 N0N0 NxNx Cross section:  exp = N x /L 2    MC =Nx MC /L MC  L MC = N0 MC /  MC e+e-→ n nbar, 2011 scan, cosmic bkgd subtraction

22 19.09.2011SND - PHIPSI1122 e + e - → n nbar, 2011 scan Experimental event

23 19.09.2011SND - PHIPSI1123 After cosmic bkgd suppression using event time ( effect + phys. bkgd) Estimated background from physical processes (pp +  SND test cross section FENICE data Physical background – 1 – e + e - → γγγ, σ ~ 0.4 nb, 2 – e + e - → ppbar, σ ~ 0.03 nb  =0.78+-0.2 nb  =0.04+-0.2 nb threshold e + e - → n nbar, 2011 scan

24 19.09.2011SND - PHIPSI1124 e + e - → p pbar, 2011 scan Picture of expected event near threshold 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

25 19.09.2011SND - PHIPSI1125 Selections (near threshold): – 3 or more tracks with vertex at beam pipe, – energy in EMC > 650MeV e + e - → p pbar, 2011 scan Experimental event

26 19.09.2011SND - PHIPSI1126 Selections (above threshold): – 2 or more tracks, – 2 collinear tracks with large dE/dx, – EMC energy > 650MeV, Experimental event e + e - → p pbar, 2011 scan

27 19.09.2011SND - PHIPSI1127 − SND − BaBar 1 e + e − → pp cross section, SND preliminary result [1] B.Aubert et al., Phys.Rev.D73 (2006) 012005 e + e - → p pbar, 2011 scan

28 19.09.2011SND - PHIPSI1128 Conclusions & Plans 1.First data taking runs have been performed with SND at VEPP-2000 in the range 1.0 − 2.0 GeV with ~ 30 inv. pb 2.Preliminary results on hadron cross sections have been obtained ( e + e - → ωπ 0, π + π - π 0, π + π - π 0 π 0, η π + π -, ppbar, nnbar) 3.To analyze the full recorded statistics 4.To upgrade the SND electronics and reconstruction procedure 5.To continue data taking runs

29 19.09.2011SND - PHIPSI1129 Thank you

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