OKA:
Status of the experimental programwith RF-separated K beam at U-70
Protvino, Russia.
V.F. Kurshetsov, IHEP, Protvino
Representing the OKA collaboration (IHEP-INR-JINR-...)OKA
GAMS: Meson
Spectroscopy

SPHINX: Baryon
Spectroscopy

ISTRA+: Kaon
DecaysExperimentswith KAons

Last status OKA report at KAON's:
V.F. Obraztsov, KAON-05, Evanston, 17 June 2005
A detailed description of the project, its history, possible
parameters of the beam and OKA setup as well as physicalprogram, as we understood it at that time, can be found there.
Conclusions from his report:
1. The construction of the RF separated high energy kaon
beam at IHEP, Protvino is close to completion.... The complex
startup of the separated beam is scheduled for December
2005.
2. The experimental setup is under construction.

Scheme of RF-separation (Panofsky).

RF Separatores during low temperature tests

Channel 21КХвост канала 21ККриогенная система канала 21К

Runs at OKA
Run 1 — Dec 2004
Run 2 — Dec 2005
Run 3 — Dec 2006
Run 4 — Dec 2007
Run 5 — Apr 2008
Run 6 — Dec 2008
Run 7 — Apr 2009*****

ProjectDecember
2007

December2008

April2009RF1, MV/m

1,00

0,32

0,590,55

RF2, MV/m

1,000,56 (∼ 0,90)

0,920,91

Oka Setup 200922 мая 2009 г.

8OKA setup at U-70
1. Beam spectrometer:
1mm pitch PC, ~1500 channels; Cherenkov counters
2. Decay volume with veto system:
11m; Veto: 670 Lead-Scintillator sandwiches 20* (5mmSc+1.5 mm Pb), WLS readout
3. PC's and DT's for magnetic spectrometer:~5000 ch. PC (2 mm pitch) + 1300 DT (1 and 3 cm)
4. Pad Hodoscope ~300 ch.
5. Magnet: aperture 200*140 cm2
6. Gamma detectors:
GAMS2000, EHS-backward EM cal. ~ 4000 LG+ 256PWOcrystals.
7. Muon identification:
GDA-100 + 4 muon trigger counters

Beam Spectrometer10Veto System(5mm Sc.+1.5 mm Pb)21 Full length ~ 11 m., 191 ФЭУ(PM)-84

11

BIG Cherenkov Counter (C3), BIG PC

e~95%

Profile and threshold curves of Big PC
Ar:Ib:Fr12=70%:28.8%:0.2%

12Straw­tubes

Prodused in Dubna (V..D. Peshekhonov)2 planes2
2140x140 cm +1 plane 180x180 cm two layes 9mm straw­
tubes, 920 channels overall. Gas mixture Ar:CO2 80%:20%

Space resolution мкм(an error is dominated by TDC bin (5 nsec ,LE-78)
13

Drift Tubes

Two planes, each plane — 3 layes of 56 3cmtubes, 336 channels overall. Gas Mixture
Ar:CO2 88%:12%Space resolution мкм (an error is dominated byTDC bin (5 nsec, LE-78)

14

Pad Hodoscope INR­RAS

2D profile (1/4 of detector)

252 + 32 channels, WLS и SiPM

Time distribution (5 nsec./bin)

15

GDA­100 and Muon CountersКалибровка ГДА-100 на мюонах16

Run April 2009
Mostly technical run from U-70 point of view.
Proton beam in U-70 was 50 GeV/c.
Three days of data taking with separated beam (12.5 GeV/c,25% Kaons).
One day of calibration with 5 GeV/c electron beam.
Total amount of data written — 830 Gb, 300M physical events+ 40M calibration events .
Based on the analysis of 1% of statistics we estimate thenumber of reconstructable K-->2pi and K-->3pi (charged)
decays as 2-3M and 0.5-0.7M correspondingly.
22 мая 2009 г.

17

Software Status
From the very beginning we decided to have two independent(almost) software branches:
Plan A: new software based on modern technologies (C++, Root,Geant4. etc.)
Plan B: software based on Sphinx analysis tools (Fortran withstructures, Geant3, Paw, etc.)
Below I will present the results from Plan B implementation.

MC EventReal Event

Triggers Apr2009:
Tr1 = Beam
Tr2 = Kaon * BK
Tr3 = Kaon * BK * C3
Tr4 = Kaon * BK * EGams

12 June 2009

Electronsby different Triggers

Near-term plan
Next run - November-December 2009
There is a plan how to improve the work of the separator
There is a plan how to improve beam collimation and intensity
With all that we hope to have in December 1M Kaons/spill(compare to 250k Kaons/spill in April)
Meantime the data analysis should give us better
understanding of the installation, better calibration andalignment constants and allow us to find the ways ofimprovements
22 мая 2009 г.

22

Main directions of the experimental program
Kaon Decays:
continuation of the physical program of ISTRA+ (see reportby V. Duck at this conference) with the increase in statistics
by a factor of 10-100
Fix-Target program:
1. Search for exotic mesons and baryons
2. Spectroscopy and Decays of light mesons
3. Primakoff physics in kaon beam

Conclusions
OKA is a working detector now!
We hope to start the production ofphysical results in the near future