STATUS OF PREPARATION OF dp-ELASTIC SCATTERING STUDY AT THE EXTRACTED BEAM OF NUCLOTRON. Yu.V.Gurchin LHE JINR September 2009

Collaboration Veksler-Baldin Laboratory of High Energies, JINR, Dubna Institute of Physics Slovak Academy of Sciences, Bratislava, Slovakia P.J. Safarik University, Koshice, Slovakia Advanced Research Institute for Electrical Engineering, Bucharest, Romania Center for Nuclear Study, University of Tokio, Tokio, Japan

Abstract The selection of the dp-elastic scattering events at the energy of 1.6 and 2.0 GeV using scintillation counters has been performed. The procedure of the CH 2 –C subtraction has been established. The dependence of the elastic events yield on the degrader thickness has been investigated. This method can be used to develop the efficient high energy deuteron beam polarimetry.

LNS project The main purpose of LNS (Light Nuclei Structure) project is the broadening of the energy and angular ranges in the measurement of different observables in the processes including 3-nucleon systems. The main aim of this experimental program is the obtaining of the information on the spin-dependent part of 3- nucleon forces. LNS project experimental program includes 2 experiments, one of them is the experiment of dp-elastic scattering study. The detection of dp- elastic scattering is realized by the coincidence of the signals from scintillation counters.

Since deuteron is spin-1 particle, deuteron beam has vector and tensor polarizations. The polarimetry should have a capability to determine both components of polarization, if possible, simultaneously. Advantages of the dp-elastic scattering reaction over the others: 1) vector and tensor analyzing powers have large values. 2) detection using simple plastic scintillation counters. The goal of present investigation is to study the possibility to use high energy dp-elastic scattering at forward angles with the selection by means of the kinematical coincidences of deuteron and proton with simple plastic scintillation counters.

Deuteron beam 1.6 Gev, 2 GeV Targets: СH 2, С Detector angles: D - 8° lab P- 70° lab Schematic view of the experiment P-proton detector, D-deuteron detector DEUTERON-PROTON ELASTIC SCATTERING EVENTS SELECTION

Detector Plastic scintillators (thickness: 5 and 25 mm) Fotomultipliers FEU-85 Digital divisors Remote high voltage supply control

The results obtained at 2.0 GeV deuteron beam on polyethylene target: a) deuteron energy losses, b) proton energy losses, c) correlation of proton and deuteron energy losses, d) time difference between the signals for deuteron and proton detectors. DEUTERON-PROTON ELASTIC SCATTERING EVENTS SELECTION ab cd

The selection of the “dp”-elastic scattering events by the energy losses correlation – a) and time difference after appying of the energy losses correlation cut- b). ab

The results obtained at 2.0 GeV deuteron beam on carbon target: a) deuteron energy losses, b) proton energy losses, c) correlation of proton and deuteron energy losses, d) time difference between the signals for deuteron and proton detectors. ab d c

Time difference spectra obtained on polyethylene (blue colour) and carbon (red) targets.

The relative normalization of the spectra by fitting by the sum of gaussian and constant obtained from polyethylene (a) and carbon (b) targets.. ab

Time difference distribution for dp-elastic events obtained from CH2-C subtraction

Relative yield of selected “dp”- events as a function of the degrader thickness: ▲- criteria A, ■- criteria A+B, ▼- criteria A+B with the background subtraction. DEPENDENCE OF THE YIELD FROM THE DEGRADER THICKNESS

CONCLUSIONS The following results has been obtained: The possibility of the dp-elastic scattering events selection at high energies and small scattering angles using scintillation counters techniques has been demonstrated. The dependence of the useful for the polarimetry events on the Pb- degrader thickness has been investigated. It is shown that the use of degrader can allow to increase the yield of useful events.

REFERENCES [1] L.S.Zolin et al., JINR Rapid Comm. 2[88]-98, 27(1998); Yu.K.Pilipenko et al., AIP Conf. Proc. 570, 801 (2001). [2] L.S.Azhgirey et al., Nucl.Instr.Meth. in Phys.Res. A497, 340 (2003). [3] K.Suda et al., Nucl.Instr.Meth. in Phys.Res. A572, 745 (2007). [4] T.Uesaka et al. Phys.Part.Nucl.Lett. 3, 305 (2006). [5] T.Uesaka et al., CNS Report , CNS, Tokyo; submitted to Nucl.Instr.Meth. in Phys.Res.

Acknowledgments. The investigation has been partly supported by the Russian Foundation for Fundamental Research (Grant No a).