First results of SND experiment at VEPP-2000 Alexey Kharlamov Budker Institute of Nuclear Physics (Novosibirsk, Russia) SND Quarks in Hadrons and Nuclei, September, 2011

Outline 1. SND and VEPP-2000 Collider complex 2. Process e+e-→ ωπ0 → π0π0γ 3. Process e+e-→ π+π-π0π0 Process e+e-→ π+π-π0 Process e+e-→ ηπ+π- Process Summary

VEPP-2000 Collider Complex CMD-3 VEPP-2000 collider: 0.36-2.0 GeV in c.m., L11031 1/cm2s at 1 GeV L11032 1/cm2s at 2 GeV Detectors CMD-2 and SND:  60 pb-1 collected in 2010-2011 Total integrated luminosity with all detectors on VEPP-2M ~ 70 pb-1

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

World best bunch to bunch luminosity First experiments with SND at VEPP-2000 Instant luminosity L > 1∙1031 cm-2s-1, at 2Е = 1 GeV Round beam conception works VEPP-2000 Energy Region, GeV Energy step, MeV Integrated luminosity, pb-1 scan2010 1.1-1.9 100 5 scan2011 1.05-2.0 25 VEPP-2М World best bunch to bunch luminosity 2011 2010

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

e+e- annihilation into hadrons Contributions to the Standard Model (SM) Prediction: From dispersion relations a [exp ] – a [SM ] ~ 3 σ had  Dominant uncertainty from lowest order hadronic piece. Cannot be calculated from QCD (“first principles”) – but: we can use experiment  had   uncertainty

e+e-→ ωπ0 → π0π0γ cross section Data - scan2010 Mπ0γ σ~20MeV Cuts: - at least 5γ - no charged particles - total energy depos. > Ebeam - kinemat. reconstruction: χ25γ <30; χ2π0π0γ− χ 25γ <10; |Mπ0γ − Mω|<100 MeV Fitting: sum of ρ(770) and ρ(1450)

e+e-→ π+π-π0π0 cross section Points – Data Histogram – MC V = ρ ρ′ ρ″ π0 π+ π- ω ρ e+ e- e+e-→ωπ0→π+π-π0π0 e+e-→a1π→π+π-π0π0 a1 e+e-→σV→π+π-π0π0 M(π+π-π0 ) Cuts: - at least 2 charged particles and 4 photons 2 tracks are central kinematic reconstruction: χ2 < 40; Mπ0 in 70-200 MeV Data - scan2010 The bump is a sum of contributions from ρ(770), ρ(1450) and ρ(1700) decays Only statistical errors

Process e+e-→ π+π-π0 Cuts: – at least 2 central charged particles Data - scan2010 Cuts: – at least 2 central charged particles – 2 or 3 γ – Δφch.part.>10° – ΔΩch.part. >40° En.depos. of ch.part.<Ebeam Total en.depos. – (0.3-0.8)Ebeam Kinematic reconstruction: interaction point - χ2r < 40; π+π–γ γ - χ2 < 30; Fittng of Mπ0 (effect+background)

e+e-→ ηπ+π- cross section Data - scan2010 Cuts: – 2 central charged particles – 2 photons – θcharged (22.5°-157.5°) – θphoton (36°-144°) kinematic reconstruction (π+π–γ γ): χ2 < 20

Picture of expected event Process Picture of expected event Cuts: – no central charged tracks – no collinear clusters in calorimeter – no signals in muon system – signals in 3 calorimeter layers – crystals in calorimeter are not located along one line – no events with main en.dep. on small angles (θ<36° or θ>144°) and full pulse in calorimeter directed into small angles – limitations on cluster quality and total pulse in calorimeter – total en.dep in the range 1.0-1.8GeV – cosmic suppression using event time Events features: No signal from “star” from annihilation point of in Cherenkov counters or calorimeter

cross section

Process Cuts(at the threshold): Cuts(above the threshold): – 3 or more charged particles with common point on vacuum tube – total en. deposition > 650MeV Cuts(above the threshold): – 2 or more charged particles – 2 central collinear tracks with large dE/dx in tracking system and 36°<θ<144° – total en. deposition > 650MeV – distribution of energy deposition in calorimeter is not located along one line

cross section Very preliminary Registration efficiency ~ 40% Background ~ 6 % (estimated using the same cuts below threshold) Data - scan2010+scan2011(part.) Babar data Very preliminary SND

Summary First data runs were performed on VEPP-2000 with SND detector (approximately 30 nb-1 collected at the energy range 1.05 − 2.0 GeV) Preliminary results on different hadron cross sections were obtained ( e+e-→ ωπ0, π+π- π0, π+π- π0 π0, η π+π-, ) The results are in agreement with previous measurements New run for study with higher luminosity and with smaller energy step will be performed (5 points with 25 MeV step → 25 points with 5 MeV step) VEPP-2000 upgrade plan: Connection to positron source VEPP-5, Smaller vacuum chamber for BEP Booster to increase B and to inject at 1 GeV, Compton scattering energy measurement system

SND old version

NaI(Tl) calorimeter Energy resolution: Angular resolution: 0 - mass 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

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 calorimeter CsI 8 – yoke 9 – VEPP-2000 solenoid

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 and f0 . 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 OZI and isospin violation. In the cross section of the e+e  +0 process the structure near 1200 MeV 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 ,   + 

Data Approximation Vector Dominance Model SU(3) JPC=1– – γ* n2S+1lJ KS e+ V=ρ,ω,φ,… γ* e– KL SU(3) JPC=1– – n2S+1lJ I=1 I=0 13S1 ρ(770) φ(1020) ω(783) 13D1 ρ(1700) – ω(1650) 23S1 ρ(1450) φ(1680) ω(1420)

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