Measurements of energy behaviour of spin-dependentnp—observables over 1.2–3.7 GeV energy region Dubna “Delta-Sigma” Experiment

Measurements of energy behaviour of spin-dependentnp—observables over 1.2–3.7 GeV energy region Dubna “Delta-Sigma” Experiment

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  Measurements of energy behaviours of spin-dependent np observables over 1.2-3.7 GeV energy region Dubna Delta-Sigma Experiment V.I. SHAROV 1 *), N.G. ANISCHENKO 1, V. G. ANTONENKO 2, S. A. AVERICHEV 1, L. S. AZHGIREY 3, V.D. BARTENEV 1, N. A. BAZHANOV , A.A. BELYAEV 5, N.A. BLINOV 1, N. S. BORISOV 3, S. B. BORZAKOV 6, YU. T. BORZUNOV 1, YU. P. BUSHUEV 1, L.P. CHERNENKO6~ E.V. CHERNYKH 1, V. F. CHUMAKOV 1, S.A. DOLGII 1, A. N. FEDOROV 3, V.V. FIMUSHKIN 1, M. FINGER 3 7, M. FINGER, JR. 3, L. B. GOLOVANOV , G.M. GUREVICH 8, D. K. GURIEV n, A. JANATA 3, A. D. KIRILLOV 1, V. (1, KOLOMIETS 3, E.V. KOMOGOROV 1, A.D. KOVALENKO , A. [. KOVALEV , V.A. KRASNOV 1, P. KRSTONOSHICH 3, E.S. KUZMIN 3, N. A. KUZMIN 11, V.P. LADYGIN 1, A. B. LAZAREV 3, F. LEHAR 9, A. DE LESQUEN 9, M. YU. Lmuac 1, A.N. LIVANOV , A. A. LUKHANIN 5, P.K. MANIAKOV 1 1 V. N. MATAFONOV ], E.A. MATYUSHEVSKY , IV. D. MOROZ 1 , A.A. MOROZOV 1, A. B. NEGANOV 3, G. P. NIKOLAEVSKY 1, A.A. NOMOFILOV 1, TZ. PANTELEEV 6,1~ YU. K. PILIPENKO 1, I.L. PISAREV 3, Yu. A. PLIS 3, Yu. P. POLUNIN A. N. PROKOFIEV 4, V. YU. PRYTKOV P.A. RUKOYATKIN , V. A. SCHEDROV 4, O.N. SCHEVELEV 3, S.N. SHILOV 3, R. A. SHINDIN 1, M. SLUNECKA 3 7, V. SLUNECKOVA 7, A. YU. STARIKOV 1, I G.D. STOLETOV 31, L.N. STRUNOV 1, A. L. SVETOV I, Yu, A. USOV3~ T. VASILIEV 1, V. I. VOLKOV 1, E.I. VOROBIEV 1, I. P. YUDINll; I. V. ZAITSEV 1 , A.A. ZHDANOV , V.N. ZHMYROV 1 JINR, Veksler and Baldin Laboratory of High Energies, 141980 Dubna, Russia 2 Russian Scientitlc Center Kurchatov Institute , 123182 Moscow, Russia 3 JINR, Dzhelepov Laboratory of Nuclear Problems, 141980 Dubna, Russia 4 St.Petersburg Nuclear Physics Institute, High Energy Physics Division, 188350 Gatchina, Russia 5 Kharkov Institute of Physics and Technology, 310108 Kharkov, Ukraine 6 JINR, fYank Laboratory of Neutron Physics, 141980 Dubna, Russia Charles University, Faculty of Mathematics and Physics, V. Hole~ovi~kdch 2, 180 O0 Praha 8, Czech Republic s Institute for Nuclear Research, Russian Academy of Sciences, 117312 Moscow, Russia 9 DAPNIA, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France lo Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Tsarigradsko shaussee boulevard 72, 1784 SoIia, Bulgaria 11 JINR, Laboratory of Particle Physics, 141980 Dubna, Russia New accurate data on the neutron-proton spin-dependent total cross section difference ACrL(np) at the neutron beam kinetic energies 1.4, 1.7, 1.9 and 2.0 GeV are presented. A number of physical and methodical results on investigation of an elastic np ---* pn charge exchange process over a few GeV region are also presented. Measurements were carried *) e-maih Czechoslovak Journal of Physics, Vol. 55 2005), Suppl. A A289  V. L Sharov et al. out at the Synchrophasotron and Nuclotron of the Veksler and Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research. Key words: relativistic polarized neutron beam, polarized proton target, total cross section difference, spin correlation parameters, charge exchange process 1 Introduction The investigations were performed under the program of the first priority JINR project "Delta-Sigma" Experiment. 1) Full name of the project is "Determination of spin-dependent elastic np forward scattering amplitudes over 1.2-3.7 GeV region: measurements of" AO L, T rip) and A00kk rip) and A00nn np) - total np cross sections differences and spin-correlation parameters from np ~ pn scattering". The aim of the project is to extend investigations of NN interaction over the new high energy region (1.2-3.7 GeV) of free polarized neutron beams, p.mvided only by the JINR VBLHE accelerators at present. The main task of these studies is to determine the imaginary and real parts of spin dependent forward scattering np amplitudes over this energy region for the first time. For this purpose a suffi- cient data set of np spin dependent observables has to be obtained for the direct reconstruction of scattering amplitudes at several energies. 1.1 The "Delta-Sigma" experiment research program Using longitudinally (L) and transverse (T) polarized neutron beams and the Dubna movable polarized proton target (PPT) to measure the energy dependences of following quantities: The AaL(np) and AaT np) - the total cross section differences for parallel and antiparallel directions of beam and target polarizations, with energy steps of 100-200 MeV and expected statistical errors of ~ 1 mb; 2. Simultaneously and independently of the A6L,T(np) experiment, measure- ments of spin correlation parameters Aookk np) (together with AaL np)) and Aoonn nP) (together wit, h AaT(np)) with expected statistical errors 0.02-0.05. . Using the high intensity unpolarized neutTvn beam and the liquid hyd,vgen or deuterium targets, to measure at the same energies as for item 1, 2 the ratio Rdp = da/d~ nd)/da/d~ np) for elastic charge exchange process np --- pn 9 t 0 o with statistical errors of ~ 5 %. The observables AaL and AaT as well as ff0tot are obtained in transmission measurements. They are linearly related to the imaginary parts of forward scat- tering NN invariant amplitudes via optical theorems and allow to extract their imaginary parts. 1) For more detailed information see A290 Czech, J. Phys. 55 2005)  Measurements of energy behaviours of spin-dependent ... Tile A00kk(np) and A00nn np) values will be obtained by a registration of yields of protons from elastic charge exchange process np ~ pn at 0 o. They are bilineary related to real parts of amplitudes which can be extracted from measured data. The ratio Rdp of differential cross sections on deuterium and hydrogen targets gives one additional relation between NN-amplitudes and a set of such data allows to avoid one uncertainty of the real parts determination. The data set of energy dependences of observables AtiLT rip), A kk np), A onn np) and Rdp will be obtained for the first time over the energy range of neutron beam of 1.2-3.7 GeV. Besides the direct amplitude reconstruction, this data set will con- tribute to extend NN phase shift analysis (PSA) to high energies and to check the predictions of dynamical models. 1.2 The accelerators and tools 1. The Synchrophasotron and Nuclotron of the JINR VBLHE. 2. Relativistic (1-5 GeV): - polarized neutron beams with L or T orientation of polarization, reversion of polarization direction cycle by cycle and average polarization value of 0.53; - high intensity (2-3) 9 10 l~ d/cycle unpolarized deuteron beam. 3. Large polarized proton target (PPT) with volume of 140 cm 3 and polarization value of 0.7-0.8. 4. Cryogenic liquid hydrogen H2 and deuterium D2 targets 30 cm long. 5. Experimental set-up DELTA-SIGMA with: monitor and transmission neutron detectors; magnetic spectrometer with multiwire proportional chambers (MPC); - detectors for target surrounding (DTS); - time-of-flight (TOF) system; data acquisition system. In the following sections a determination of the NN spin-dependent observables and some results of investigations under tile Delta-Sigma experiment program will be done. The last accurate data [1, 2] on the neutron-proton spin-dependent total cross section difference AaL(np) at the neutron beam kinetic energies 1.4, 1.7, 1.9 and 2.0 GeV will be presented. A number of physical and methodical results on investigation of the elastic np ~ pn charge exchange process over the energy region under discussion will be also presented. Czech. J. Phys. 55 2005) A291  V.I. Sharov et al. 2 The A~ L,T(np) observables In this contribution, we use NN formalism and the notations for elastic nucleon- nucleon scattering observables from [3]. The general expression for the total cross section of a polarized nucleon beam trasmitted through a polarized proton target, with arbitrary directions of beam and target polarizations is Wtot = W0tot + Wltot(PB, PT) + W2tot(PB, k)(PT, k), 1) where PB and PT are the beam and target polarizations and k is a unit vector in the direction of the beam momentum. The term o-0tot is the total cross section for unpolarized particles, Wltot and W2tot are the spin-dependent contributions. They are related to the measurable observables AnT and AWL by: A~ T = 20 1tot , --AW L 2 Wltot -Jr- W2tot), 2) 3) Values of w0tot, AWT and AO L are connected with the imaginary parts of three invariant forward scattering amplitudes a+ b, c and d via three optical theorems 0 0tot = (27f/K) Im [a(0) + b(0)], --ANT = 47r/K) Im [c 0) + d 0)], -awl = 4~/~) Im It 0) - d 0)], 4) 5) 6) where K is the c.m. momentum of the incident nucleon. Relations (5) and (6) allow one to extract the imaginary parts of the spin-dependent invariant amplitudes c(0) and d(0) at an angle of 0 ~ from tile measured values of AaL and AW T. Using the measured vahles of AWL,T(np) and the existing AWL,T(pp) data at the same energy, one can deduce AWL,T(I = 0) as AaL,T(I = 0) = 2Ao L,T(np) AffL,T pp ). 7) 3 Results of the AaL(np) measurements A large amount of results for np elastic scattering and transmission experiments at energies up to 1.1 GeV was accumulated by the end of the 80 th. (See for exam- ple review [4].) The possibility to extend measurements of the np spin-dependent observables to higher energies exists now at the JINR VBLHE accelerators only. The measurements of energy dependences of the np total cross sections differ- ences AaL(np) and Aaw(np) for parallel and antiparallel particle spins oriented longitudinally or transverse were proposed [5, 6] at the beginning of the 90 th and started [7-10] in Dubna. To implement the proposed Aaa,T(np) experimental pro- gram, a large Argonne-Saclay polarized proton target (PPT) was reconstructed in Dubna [11-13], and a new polarized neutron beam line with suitable parameters A292 Czech. J. Phys. 55 2005)  Measurements of energy behaviours of spin-dependent ... [14, 15] was constructed and tested. A set of necessary neutron detectors with cor- responding electronics, and up to date data acquisition system and other needed equipment were also prepared, tuned and tested. Two successful data taking runs were carried out in 1995 and 1997. The energy dependence of A~L(np) was mea- sured at 1.19, 1.59, 1.79, 2.2, 2.49, and 3.66GeV [7-10]. This contribution presents new results for the spin-dependent np total cross section difference Aaa (rip) obtained in 2001 with longitudinally polarized both the quasi-monochromatic polarized neutron beam and the PPT. The values of AaL(np) were measured at neutron beam kinetic energies of 1.4, 1.7, 1.9 and 2.0 GeV. The measured -AaL(np) values are presented in [1, 2] and shown in Fig. 1. Statistical and systematic errors are taken into account. Total errors are the quadratic sums of experimental and systematic uncertainties. The results of our earlier measurements [7-10] together with the existing AaL(np) data [4], obtained with free polarized neutrons at lower energies, are also shown in Fig. 1. One can see that the new results smoothly connect with the lower energy data and confirm a fast decrease to zero within a 1.2-2.0 GeV energy region, observed previously [7-10]. The solid curves show the last energy-dependent GW/VPI PSA fits [16, 17] (FA95, SP99 and SP03 solutions) of this observable over the interval from 0.1 to 1.3 GeV. Above 1.1 CeV (Saturne II), the np database is insufficient and a high energy part of the AaL(np) PSA predictions still disagrees with the measured data. Below 2.0 GeV, a usual meson exchange theory of NN scattering [18] gives the AO'L (np) energy dependence as shown by the dotted curve in Fig. 1. It can be seen that this model provides a qualitative description only. More detailed and accurate --AaL(np) measurements around 1.8 GeV and ob- taining of new -Ar data using coming high intensity (_> 2 9 101~ d/cycle) relativistic polarized deuteron beam from the JINR VBLHE Nuclotron are planned. 4 Measurements of the Aookk(np) and Aoonn(np) observables from np ~ pn process An expression ibr the differential cross sections for scattering of polarized nu- cleon beam with energy E on the polarized target nucleons with the scattered particle detection at an angle of 8 is [3, 4] [da/dfl]pol(E, 8) = da/dYl(E, 8). [1 + Aoono(E, 8). PB" + Aooon(E, 8). PT- +Aoon,~(E, 8). PB- 9 PT- + Aooss(E, 8). PB, 9 PTS +Aookk(E, 8). PBk 9 PT~ +Aoo~k(E, 8)(PB s" PT k + PSi" PTs)], 8) where da/dfl is the cross section for unpolarized nucleons. If the scattered particles are detected at 0 ~ then analyzing powers A0on0 (E, 0) = Aooo,~ ( E , O) = 0 and parameters Ao0sk(E,0) = 0 and A00ss(E, O) = Aoonn ( E , 0). Thus, only two different non-vanishing spin-dependent quantities A00nn (E, 0) and Ao0kk(E, 0) remain in Eq. (8). Czech. J. Phys. 55 2005) A293
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