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

2. Short outline 1. VEPP-2000 and CMD-3 detector 2. Energy scan in runs 2011 3. Detector resolutions 4. Luminosity determination 5. Some preliminary results 6. 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. Lay-out of VEPP-2000 with round beams CMD-3 SND 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 = 10 32 cm -2 s -1 at 2.0 GeV L = 10 31 cm -2 s -1 at 1 GeV

5. 3D view CMD-3 detector DC – 1218 hexagonal cells with sensitive wires, W-Re alloy, 15  in diameter. Z-chamber – start FLT, precise determine z-coordinate ~ 500  (detector acceptance) LXe calorimeter thickness 7 X 0, 196 towers & 1286 strips. Spatial resolution 1 – 2 mm. Calorimeter with CsI crystals (  3,5 t), 8 octants, number of crystals - 1152, 8 X 0. 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. event e+e-  e+e- R-  plane First run: winter-spring 2011 R-z plane

7. History of data taking in 2011

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

9. - Number of hitted wires (track belong) in DC >= 10 - 500 MeV/c < P 1,P 2 < 1500 MeV/c -|θ 1 - θ 2 | π - 1.0 < ( θ 1 + (π - θ 2 ))/2 < 1.0 Bhabha events are inside red box Bhabha events

10. Luminosity determination L = N e+e- /(σ Born *  rad *ε DC *ε 2 cl ) Ne+e- -- number of detected Bhabha events σ Born -- Born cross section  rad -- radiation correction (  0.95) ε DC -- track reconstr. effi. in DC (  99.142 ± 0.084 %) ε cl -- 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, E 1 + E 2 > 1.3*E beam, E 1, E 2 < 1500 MeV Cut on angles between clusters in LXe:|θ 1 + θ 2 – π| < 0.3 rad

12. 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 φ DC - φ LXe < 0.3 rad θ DC - θ LXe < 0.4 rad As a result was found that: ε cl = 0.995 (1000 MeV) Clusters reconstruction efficiency in calorimeters

13. 2E, МeVIntegr. lum., nb -1 2E, MeVIntegr. lum., nb -1 11050423.5191975513.6 21100459.8202000471.3 31150461.6211875663.4 41200537.4221825503.6 51250379.6231775550.1 61300434.3241725523.8 71350522251675562.9 81400490.6261625511.5 91450418.5271575498.7 101500518.9281525498 111550495.5291475476.0 121600444301425509.9 131650463.6311375178.7 141700486.6321325501.0 151750539.4331275432.4 161800439.2341225507.8 171850431.5351175496.5 181890522.7361125522.2 191930580.1371075524.8 2011 energy scan program

14. Gamma-gamma events

15. Preliminary results: 2E > 1 GeV

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

17. What does a  consist of? Relative contributions to a  2 , 73% , 5.5% , 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) a μ (theory) = a μ (QED) + a μ (Weak) + a μ (Hadronic) Contribution to a  vs energy, 10 MeV step Contribution to error of the a  vs energy, 10 MeV step red points-systematic black points- statistic

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

21. What else? 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 about 20 pb -1 (100 times more) Depends on and value R(s)

22. Search for  (1420) &  (1650) decay into 3  vs energy a 1 (1260)  is enough to describe cross section dependence vs energy for 4  channel. But at high statistic  channel will contribute 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 -, K S K L and strange vector hybrid in decays  (1680)  K*K  KK  &   K 1 (1400)K  K*  K  KK .  f 0 (980), , , radiation decays and physics of  и  mesons… Exclusive decay modes

23. Nearest plans? Collect the integrated luminosity in forthcoming season about 200 pb -1 Search for N Ñ 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 (  10 31 ). New injection complex will provide project luminosity  10 32.

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

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

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