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JINR, Dubna 5-9 December, 2011

Current status of luminosity measurements with the CMD-3 detector at VEPP-2000 G.V.Fedotovich BINP, Novosibirsk. JINR, Dubna 5-9 December, 2011. Short outline. 1. VEPP-2000 and CMD-3 detector

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JINR, Dubna 5-9 December, 2011

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  1. Current status of luminosity measurements with the CMD-3 detector at VEPP-2000 G.V.Fedotovich BINP, Novosibirsk JINR, Dubna 5-9 December, 2011

  2. Short outline 1. VEPP-2000 and CMD-3 detector 2. Energy scan in runs 20113. Detector resolutions4. Luminosity determination5. Some preliminary results6. Nearest plans

  3. Motivation Why luminosity determination better than 0.5% is required Hadron contribution to (g-2) of muon is about 60 ppm 600.005 = 0.3 ppm Aim new FNAL experiment for (g-2) of muon is to improve BNL result by a factor of 4! Current accuracy 0.6 ppm As a rule all hadronic cross sections in experiments at e+e- colliders are normalized on integrated luminosity For luminosity determination it is necessary to use well known QED processes which have the large magnitude of cross section and a simple signature in detector e+e-  e+e-, , +- (cross check capability)

  4. CMD-3 Lay-out of VEPP-2000with round beams • revolution time – 82 ns beam current – 200 mA • beam length – 3.3 cm energy spread – 0.7 MeV • circumference – 24.4 m beta function in IP x=z =4.3cm • L = 1032cm-2s-1at 2.0 GeV L = 1031cm-2s-1 at 1 GeV SND

  5. 3D view CMD-3 detector DC – 1218 hexagonal cells with sensitive wires, W-Re alloy, 15 m in diameter. Z-chamber – start FLT, precise determine z-coordinate ~ 500  (detector acceptance) LXe calorimeter thickness 7 X0, 196 towers & 1286 strips. Spatial resolution 1 – 2 mm. Calorimeter with CsI crystals (3,5 t), 8 octants, number of crystals - 1152, 8 X0. TOF – 16 counters, time resolution ~ 1ns MR system – 8 octants (cosmic veto, ~ 1ns) Project magnetic field - 1,5 T (working at 1.3 T while)

  6. First run: winter-spring 2011 event e+e-  e+e- R-z plane R- plane

  7. History of data taking in 2011

  8. First step – collinear events selection 1. Hit points on track >5 (max 19) 2. Total charge =0 3.Accolinearity angle in R -  plane: | | φ1-φ0|-π | < 0.15 rad 4. Accolinearity angle in R – z plane: |θ1 + θ0 -π| < 0.25 rad 1. Event is Bhabha, if: • Number of cluster in LXe calorimeter is 2 exactly • Angle (π - 1.0) < ( θ1lxe- θ0lxe +π )/2 < 1.0 rad • Energy every cluster E1,2 > Ebeam/2 • Number of hitted sectors > 0 Second step – Bhabha events selection

  9. Bhabha events • - Number of hitted wires (track belong) in DC >= 10 • - 500 MeV/c < P1,P2< 1500 MeV/c • |θ1 -θ2| < (3.14 - 2)<=>π-1.0 < ( θ1 +(π-θ2))/2 <1.0 • Bhabha events areinside red box

  10. Luminosity determination L = Ne+e-/(σBorn*rad*εDC*ε2cl ) Ne+e- -- number of detected Bhabha events σBorn -- Born cross section rad -- radiation correction ( 0.95) εDC -- track reconstr. effi. in DC ( 99.142 ± 0.084 %) εcl-- probability that cluster energy in calorimeters grater than 0.5 2Ebeam and smaller than 1.5 2Ebeam

  11. Track reconstruction efficiency in DC Events are selected using calorimeters information only: Selection conditions and cuts nLXe = 2 & nCsI = 2, E1 + E2 > 1.3*Ebeam, E1,E2 < 1500MeVCut on angles between clusters in LXe:|θ1 + θ2 –π| < 0.3 rad

  12. Clusters reconstruction efficiency in calorimeters Events are selected using DC and ZC information only: Selection conditions and cuts Two back-to-back tracks in DC and look for clusters in LXe calorimeter which are belong tracks Cuts φDC-φLXe <0.3 rad θDC-θLXe <0.4 rad As a result was found that: εcl = 0.995 (1000 MeV)

  13. 2011 energy scan program

  14. Gamma-gamma events

  15. Preliminary results: 2E > 1 GeV

  16. Radiation return Half statistic  20 pb-1 is processed (1450) (1570) (1420) (1650) (1680) (1700) (1900)

  17. What does a consist of? Relative contributions toa , 5.5% 2, 73% , 5.2% 2E, 0.6–1.8 GeV, 7.8% 2E, 1.8 – 5 GeV, 6.0%

  18. Hadronic contribution to anomalous magnetic moment of muon This plot demonstrates how quickly integral amount to asymptotic value ~ 60 ppm. For s>2 GeV the contribution is about ~ 6 ppm only

  19. One of the main physical task is to measure quantity R(s) aμ(theory) = aμ(QED) + aμ(Weak) + aμ(Hadronic) Contribution to am vs energy, 10 MeV step Contribution to error of the am vs energy, 10 MeV step black points- statistic red points-systematic

  20. Derivative d|F(E)|²/dE/|F(E)|²x E/E (accuracy of energy determination) (E/E = 10-3) Derivative jumps up and down inside corridor 1%, but near  and  mesons reaches the values 6%. Very important taskto determine beam energy with relative accuracy E/E  10-4 or even better

  21. What else? Depends on and value R(s) About 40% of the error comes from energy range 1 to 2.5 GeV Today integrated luminosity inside this energy band is200nb-1 After this energy scan we have about20pb-1 (100 times more)

  22. Exclusive decay modes Search for (1420)&(1650) decay into 3 vs energy a1(1260) is enough to describe cross section dependence vs energy for 4 channel. But at high statistic  channelwillcontribute at noticeable level too? Search for intermediate dynamics is very importance. 5 channel with intermediate states (1420) & (1650) which decay to  5 channel with intermediate states(1450)&(1700) which can decay to  6 channel - gold mode for search(1900). What is the mass? It is upper or lower of the threshold production NNbar? Is this state baryonium?Hybrid or something else? Search for decay(1680)K+K-, KSKL and strange vector hybrid in decays (1680)  K*K  KK  &  K1(1400)KK*K  KK. f0(980), , , radiation decays and physics of и  mesons…

  23. Nearest plans? Collect the integrated luminosity in forthcoming season about 200 pb-1 Search for NÑ events, select and study detection efficiency for this process Study in detail 4, 5 and 6 channels (prepare preliminary results for coming conferences) New techniques will be installed for beam energy determination using Compton’s back scattering (10-4). It will take additional time (about 2 months) RF system of the booster will be redone too to provide beam energy injection up to 1000 MeV (850 MeV). We loose about 30% of integrated luminosity for higher energies while. The rise time and fall time of beam energy in VEPP-2000 is a complicated problem. Luminosity is limited by positron storage rate (1031). New injection complex will provide project luminosity 1032 .

  24. Thanks for attention on behalf of the CMD-3 collaboration!

  25. DC resolutions R- (drift time) 100 140 m R-z (charge division)2  3 mm (dE/dx) 0.15*dE/dx

  26. First run: winter-spring 2010 Evente+e-++ 

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