Current status and results of the experiments at VEPP-2000

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1 Current status and results of the experiments at VEPP-2000 Boris Shwartz, BINP, Novosibirsk, Introduction VEPP-2000 status Detectors Preliminary results MesonNet meeting, Prague, Czech Republic 1

2 Tests of perturbative QCD VEPP-2000 is BINPe + e collider for s = GeV Motivations for precise measurements of hadron cross sections in low energy region QCD sum rules, quark masses, quark and gluon condensates Higher order QCD corrections - Λ QCD, α(s) Hadronic corrections to fundamental parameters: Running fine structure constant - α(m Z2 ) Anomalous magnetic moment of the muon measurement of parameters of light vector mesons ρ, ω, φ, ρ, ρ,.. comparison with spectral functions of the hadronic tau decays via CVC Study of nucleon-antinucleon pair production nucleon ectromagnetic form factors, search for NNbar resonances,.. Hadron production in radiative return (ISR) processes Two photon physics MesonNet meeting, Prague, Czech Republic 2

3 Overview of the VEPP-2M results The VEPP-2M collider with the luminosity of cm- 2 s -1 was the main supplier of the precise data on the hadronic cross section in the energy range below up to 1.4 GeV for more than 25 years from 1974 to Ldt 70 pb 1 Systematic error: ~ % 1.0% 0.6% 1.5% % Error of R(s) Total error: ~ % 1.5% 1--2% 2.0% % MesonNet meeting, Prague, Czech Republic 3

4 Pion formfactor measurement (VEPP-2M) CMD-2 Comparison with ALEPH and BELLE tau decay data 0.7% 0.6% -0.8% Systematic error % Comparison with π + π γ - from BaBar (ISR) KLOE comparison ISR MesonNet meeting, Prague, Czech Republic 4

5 New collider VEPP-2000 The main idea 2Emax: 1.4 GeV 2 GeV round beams! ocussing solenoids =12 T MesonNet meeting, Prague, Czech Republic 5

6 Round beams VEPP-2000 uses special optics providing round beams L 2 2 πγ ξxξ yεx f σ 2 2 y 4 = 1 2 * + L = 2 re βy σx re β πγ ξ ε f ξx,y 0.1! MesonNet meeting, Prague, Czech Republic 6

7 The maximum luminosity is cm 1 s 1 at GeV, falling much slower with decreasing energy than before the round beams At high energies lumi is limited by a deficit of positrons and maximum energy of the booster (900 MeV now) MesonNet meeting, Prague, Czech Republic 7

8 Since 2010, when data taking started, until now CMD-3 collected: about 10 pb 1 at the φ-meson, 33 pb 1 from φ to 2 GeV and about 12 pb 1 below the φ. Current run will continue untill end of June. In 2013 we reached MeV, the smallest energy ever measured at ee colliders MesonNet meeting, Prague, Czech Republic 8

9 Online monitor (CMD-3, 1 hours) Two detectors have been build for the study We hope to collect fb 1 in few years By now We already have ~60 pb 1/detector Comparable to previous e + e experiments and ISR data from B factories. To measure the beam energy special system based on the Compton back scattering of the laser photons is used. The accuracy of these measurements is kev MesonNet meeting, Prague, Czech Republic 9

10 CMD-3 Detector Advantages compared to CMD-2: new drift chamber with x2 better resolution better tracking thicker barrel calorimeter better separation LXe calorimeter - much better spatial resolution for γ s 1 m -shower profile 1 beam pipe, 2 drift chamber, 3 BGO calorimeter (680 crystals), 4 Z chamber, 5 CMD-3 superconducting solenoid, 6 calorimeter LXe (400 liters), 7 calorimeter CsI (1152 crystals), 8 iron yoke, 9 solenoids of VEPP-2000, (not shown) muon range system (scintillation counters) and TOF system MesonNet meeting, Prague, Czech Republic 10

11 SND 2000 σ E 4.2% 0 = 0.82 σ E 4 φ = 0.63 EGeV ( ) EGeV ( ) 0 Energy resolution 1 beam pipe Advantages compared to old SND: 2 tracking system new system - cherenkov counters (n= 1.13) 3 aerogel e/π separation E<450 MeV 4 NaI(Tl) crystals π/k separation E<1 GeV 5 phototriodes new drift chamber NIM A449 (2000) muon absorber better tracking 7 9 muon detector better determination of solid angle 10 focussing solenoid MesonNet meeting, Prague, Czech Republic 11

12 Pion Form Factor with CMD MesonNet meeting, Prague, Czech Republic 12

13 Pion Form Factor with CMD-3 expectations Source of error 2pi s<1 GeV Event separation 0.2% Fiducial volume 0.2% Energy calibration 0.1% Efficiency correction 0.1% Pion losses (decay, NI) 0.1% Radiative corrections 0.1% Total 0.35% MesonNet meeting, Prague, Czech Republic 13

14 e + e - ηπ + π - ηρ e + e - π 0 π + π - ρ / ρ М ππ MesonNet meeting, Prague, Czech Republic 14

15 e + e π + π π 0 π 0 ρ / +ρ // scan 2010 Intermediate states: ωπ 0 a 1 π ρ + ρ ρf 0 ρf 2 Only statistical errors are shown MesonNet meeting, Prague, Czech Republic 15

16 e + e - ωπ 0 π 0 π 0 γ, scan M π0γ Fit: sum of ρ(770) and ρ(1450) contributions MesonNet meeting, Prague, Czech Republic 16

17 e + e π + π π 0 η (ωη,φη) e + e - π + π - π 0 π 0 π 0 π 0 π + π - 8γ scan 2011 Preliminary η First observation! p bar p threshold MesonNet meeting, Prague, Czech Republic 17

18 + e e p p, n n 2 2 d σ α βc M N 2 2 = { G M (s) (1 + cos ϑ ) + G E (s) sin d Ω 4 s s ϑ } σ = N 2 M (s) + G E (s) 2 πα βc { G 3s 2M s } C πα β πα /(1 e ) At s=4m N2 G E =G M β MesonNet meeting, Prague, Czech Republic 18

19 Collinear events in CMD-3 (E c.m. = 1.95 GeV) e + e used for luminosity meas. Currently ~1% syst. (goal ~0.1%) e + e cosmic μ+μ P P + π + π K + K MesonNet meeting, Prague, Czech Republic 19

20 Preliminary results for the e + e > PbarP study Clear signature of the PbarP events SND BaBar 1 SND preliminary MesonNet meeting, [1] B.Aubert Prague, et al., Czech Phys.Rev.D73 Republic (2006)

21 e + e nn Event topology n n Even signature: no signal from neutron star from anti neutron NNbar detection efficiency ~ 20 30% MesonNet meeting, Prague, Czech Republic 21 21

22 Preliminary results for the e + e > 2(π + π ) study We have relatively clean selection of 4 and 3 charged pions Example of e + e - -> 4 charged tracks in CMD-3 BaBar CMD 3 PbarP threshold Statistical errors are at the level of 1-2% per point. Systematical errors are under investigation. We confirm a 1 (1260)π dominance. Some other states (ρ(770)f 0 (600), ρ(770)f 0 (980)) are seen, but small MesonNet meeting, Prague, Czech Republic 22

23 Preliminary results for the e + e > K + K π + π study We have very clean selection of the Κ + Κ π + π channel. πk separation by dedx in DC Ec.m. = 1.8 GeV K + K π + π ρ(770) K*(892) BaBar CMD 3 3 track events are reconstructed as well MesonNet meeting, Prague, Czech Republic 23

24 Example of e + e > π + π π + π π + π from CMD MesonNet meeting, Prague, Czech Republic 24

25 e + e 3π + 3π The very first physical publication of CMD-3 in arxiv: , PLB A scan from 1500 to 2000 MeV, Ldt =22 pb 1 About 8k five- and six-track events selected (5069 and 2887 events, respectively) Very few candidates below 1.5 GeV We study dynamics, pure phase space doesn t work, three models with JPC = 1, each with one ρ 0 /event: ρ(1450)(2π + 2π ) S wave a 1 (1260) ± πππ + π ρ 0 2(π + π ) 3(π + π ) ρ(770)(2π + 2π ) S wave 3(π + π ) 3 options for 2π + 2π : phase space, f 0 (1370), f 0 (1500) ρ(770)f 2 (1270) 3(π + π ) The best description is with one (770) and 4 pions in S-wave MesonNet meeting, Prague, Czech Republic 25

26 Preliminary results for the e + e > 3(π + π ) study We have very clean selection of 6 and 5 pions Physics Letters B 723 (2013) BaBar CMD 3 Other data for e + e > 3(π + π ) PbarP threshold MesonNet meeting, Prague, Czech Republic 26

27 Preliminary results for the e + e > 2(π + π π 0 ) study We have relatively clean selection of 2 and 1 π 0 in addition to four charged tracks #1 #2 m γγ, MeV ωη, φη, ρ4π intermediate states are seen, systematic errors are under study MesonNet meeting, Prague, Czech Republic 27

28 Further improvements ILU 2.5 MeV Linac CMD-3 B-3M 250 MeV synchrobetatron BEP e, e + booster 825 MeV RF VEPP m SND 500 MeV e +,e from the new injection complex with 500 MeV linac and cooling ring e e + convertor 1000 MeV A long shutdown for years to increase the booster energy to 1 GeV and commission the new injection complex to reach cm 2 s MesonNet meeting, Prague, Czech Republic 28

29 Conclusion New accelerator principles put on the base of the VEPP-2000 collider were successfully proved. First two experimental runs generated considerable amount of data which are analyzed now. Hopefully, in the next 5-10 years the VEPP-2000 will produce the integrated luminosity ~ 1 fb 1 which should provide new precise interesting results on the hadron production in e + e annihilation. The current run will continue untill the end of June. Then a long shutdown for years to increase the booster energy to 1 GeV and commission the new injection complex to reach cm 1 s 1 We intend to use this time for the data analysis and detectors upgrade MesonNet meeting, Prague, Czech Republic 29

30 backup MesonNet meeting, Prague, Czech Republic 30

31 Muon Anomalous Magnetic Moment had αmμ Ks () aμ (. lo.) = ds R( s) 2 3π s 2 2 π 4m Rs () σ = + ( e e γ hadrons) (0) + + σ ( ee μ μ ) (0) * contribution (from F. Jegerlehner) error 2 Δ(exp-theory) > 3σ! MesonNet meeting, Prague, Czech Republic 31

32 VEPP-2000 view MesonNet meeting, Prague, Czech Republic 32

33 Energy measurement BS Compton МэВM.N. Achasov et al. arxiv: v1 [physics.acc-ph] 1 Nov MesonNet meeting, Prague, Czech Republic 33

34 CMD-3 Detector SND at VEPP MesonNet meeting, Prague, Czech Republic 34

35 Systematic errors Source of error CMD-2 s<1 GeV SND CMD-2 s>1.0 GeV Event separation % 0.5% % Fiducial volume 0.2% 0.8% % Energy calibration % 0.3% % Efficiency correction 0.2%-0.5% 0.6% % Pion losses (decay, NI) 0.2% 0.2% 0.2% Other 0.2% 0.5% % Radiative corrections % 0.2% % Total % 1.3% % MesonNet meeting, Prague, Czech Republic 35

36 e + e π + π π 0, π + π η 2010 scan e + e - π + π π 0 event π η M MesonNet meeting, Prague, Czech Republic 36 γγ, MeV

37 Preliminary study of the e + e > π + π π 0 π 0 process Looking for two π 0 in addition to two charged tracks. The π 0 efficiency is under investigation. Preliminary mass distributions study: ω(782) In addition to dominant ωπ 0 and a 1 π we see ρ + ρ, ρ(770)f 0 (600)?, ρ(770)f 0 (980) First look to the e + e > 2(π + π )π 0 process a 1 (1260) Example of ωf 0 (980) signal In ωπ + π final state MesonNet meeting, Prague, Czech Republic 37

38 3 track events MesonNet meeting, Prague, Czech Republic 38