JINR, Dubna5-9 December, 2011

Current status of luminosity measurements with the CMD-3 detector at VEPP-2000

G.V.FedotovichBINP, Novosibirsk

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

Motivation

Why luminosity determination better than 0.5% is required

Hadron contribution to (g-2) of muon is about 60 ppm 600.005 = 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)

Lay-out of VEPP-2000with 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 = 1032 cm-2s-1 at 2.0 GeV L = 1031 cm-2s-1 at 1 GeV

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 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)

event e+e- e+e-

R- plane

First run: winter-spring 2011

R-z plane

History of data taking in 2011

1. Hit points on track > 5 (max 19)2. Total charge = 03. 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 E1,2

> Ebeam

/2• Number of hitted sectors > 0

First step – collinear events selection

Second step – Bhabha events selection

- 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 are inside red box

Bhabha events

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

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 < 1500 MeV

Cut on angles between clusters in LXe:|θ1 + θ2 – π| < 0.3 rad

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)

Clusters reconstruction efficiency in calorimeters

2E, МeV Integr. lum., nb-1 2E, MeV Integr. lum., nb-1

1 1050 423.5 19 1975 513.6

2 1100 459.8 20 2000 471.3

3 1150 461.6 21 1875 663.4

4 1200 537.4 22 1825 503.6

5 1250 379.6 23 1775 550.1

6 1300 434.3 24 1725 523.8

7 1350 522 25 1675 562.9

8 1400 490.6 26 1625 511.5

9 1450 418.5 27 1575 498.7

10 1500 518.9 28 1525 498

11 1550 495.5 29 1475 476.0

12 1600 444 30 1425 509.9

13 1650 463.6 31 1375 178.7

14 1700 486.6 32 1325 501.0

15 1750 539.4 33 1275 432.4

16 1800 439.2 34 1225 507.8

17 1850 431.5 35 1175 496.5

18 1890 522.7 36 1125 522.2

19 1930 580.1 37 1075 524.8

2011 energy scan program

Gamma-gamma events

Preliminary results: 2E > 1 GeV

Half statistic 20 pb-1 is processed

(1

420)

(14

50)

(15

70)

(17

00)

(19

00)

(1

650)

(16

80)

Radiation return

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%

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

One of the main physical task is to measure quantity R(s)

a(theory) = a(QED) + a(Weak) + a(Hadronic)

2

2

24( ;1) ( ) ( )

3 m

m dsa Had K s R s

s

Contribution to avs energy,

10 MeV stepContribution to error of the avs

energy, 10 MeV step

red points-systematicblack points- statistic

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)

910

69 10F

F

GG

52 10Z

Z

MM

2

42

( ) (10 )Z

Z

M OM

What else?

, , M , M , m , M ... F Z W t HG

About 40% of the error comes from energy range 1 to 2.5 GeV

Today integrated luminosity inside this energy band is200nb-1

After this energy scan we have about 20 pb-1 (100 times more)

2

tot

2(5) 2

2

4

σ ( hadrons) R(s)=

σ( )

( )( ) Re

3 ( )Z

had ZZm

e e

e e

M R sM ds

s s M i

Depends on and value R(s)

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 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-, 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…

(ssg)

Exclusive decay modes

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 .

Thanks for attention

on behalf of theCMD-3

collaboration!

R- (drift time) 100 140 m R-z (charge division) 2 3 mm

(dE/dx) 0.15*dE/dx

DC resolutionsDC resolutions

Event e+e- + +

First run: winter-spring 2010