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Papers by G. Macharashvili
Journal of Physics: Conference Series, 2011
Spin observables in proton deuteron breakup reactions at low energies offer a rich testing ground... more Spin observables in proton deuteron breakup reactions at low energies offer a rich testing ground for the modern theory of nuclear forces, the chiral effective field theory (EFT). In the three-nucleon continuum the experimental data and the theoretical predictions are today at variance. At the PAX facility at COSY we plan to make an extensive study of analyzing powers and spin correlation parameters in pd breakup reactions at low energies between 30 and 50 MeV, an energy range where previous measurements are scarce and limited while three-nucleon effects are expected to be significant. Furthermore it is an ideal energy for the predictive power of chiral EFT to be tested. The longstanding physics question of the nature of three-nucleon forces will be studied with large coverage provided by an optimized silicon detector barrel, and flexibility utilizing the sampling method, a technique for direct comparison between experiment and theory developed specifically for the complex analysis of three-particle final states. The proposed experiment will yield an independent determination of the low-energy constants D and E and enable tests of appearing three-nucleon interactions in chiral EFT, with possible implications also for the spectra of light nuclei.
The first measurement of the pn → dω total cross section has been achieved at mean excess energie... more The first measurement of the pn → dω total cross section has been achieved at mean excess energies of Q ≈ 28 and 57 MeV by using a deuterium cluster-jet target. The momentum of the fast deuteron was measured in the ANKE spectrometer at COSY-Jülich and that of the slow "spectator" proton (psp) from the pd → pspdω reaction in a silicon telescope placed close to the target. The cross sections lie above those measured for pp → ppω but seem to be below theoretical predictions.
... Lett. B264 (1991) 269. 7. W. Abner, P. Baltes, Chr. Bormann, et al., Z. Phys. A341 (1991) 123... more ... Lett. B264 (1991) 269. 7. W. Abner, P. Baltes, Chr. Bormann, et al., Z. Phys. A341 (1991) 123. ... E. R6ssle and OWB Schult, ISSN 09386521,1993, pl. 9. W. Cassing. T. Demski, L. Jarczyk, B. Kamys, Z. Rudy, OWB Schult, A. Strzalkowski, Z. Phys. A, in press. 10. ...
The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungsze... more The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jülich. An initial scientific goal is to study K+-production in pA collisions at subthreshold energies below the free NN-threshold of T = 1.58 GeV. First measurements of double differential cross sections in p12C collisions at emission angles around 0° have been performed at T
A polarized antiproton beam at the Facility for Antiproton and Ion Research, proposed by the PAX ... more A polarized antiproton beam at the Facility for Antiproton and Ion Research, proposed by the PAX collaboration, will open a window to new physics uniquely accessible at the new High Energy Storage Ring. Our proposal to realize an asymmetric collider, in which polarized protons with momenta of about 3.5 GeV/c collide with polarized antiprotons with momenta up to 15 GeV/c, is well--suited to perform a direct measurement of the transversity distribution function h_1h_1h_1. In this report we summarize the outcome of various working group meetings within the PAX collaboration. The overall machine setup at the HESR, proposed by the PAX collaboration, is described along with the associated PAX experimental program.
We propose to use an internal polarized hydrogen storage cell gas target in the AD ring to determ... more We propose to use an internal polarized hydrogen storage cell gas target in the AD ring to determine for the first time the two total spin–dependent pbar-p cross sections σ1 and σ2 at antiproton beam energies in the range from 50 to 450 MeV. The data obtained are of interest by themselves for the general theory of pbar-p interactions since they will provide a first experimental constraint of the spin–spin dependence of the nucleon–antinucleon potential in the energy range of interest. In addition, measurements of the polarization buildup of stored antiprotons are required to define the optimum parameters of a future, dedicated Antiproton Polarizer Ring (APR), intended to feed a double–polarized asymmetric pbar-p collider with polarized antiprotons. Such a machine has recently been proposed by the PAX collaboration for the new Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, Germany. The availability of an intense stored beam of polarized antiprotons will provide ...
Physics Letters B, 2006
The pp → ppπ 0 differential cross section has been measured with the ANKE spectrometer at COSY-Jü... more The pp → ppπ 0 differential cross section has been measured with the ANKE spectrometer at COSY-Jülich for pion cms angles between 0 • and 15.4 • at a proton beam energy of 0.8 GeV. The selection of diproton pairs with an excitation energy E pp < 3 MeV ensures that the final pp system is dominantly in the spin-singlet 1 S 0 state. The kinematics are therefore very similar to those of pp → dπ + but with different spin and isospin transitions. The results will thus provide a crucial extra test of pion production models in nucleon-nucleon collisions.
Physics Letters B, 2006
Vector and tensor analysing powers of the dp → (pp)n (charge-exchange) and dp → (pn)p (non-charge... more Vector and tensor analysing powers of the dp → (pp)n (charge-exchange) and dp → (pn)p (non-charge-exchange) breakup reactions have been measured with the ANKE spectrometer at the COSY ring at a deuteron beam energy of 1170 MeV for small momentum transfers to the low excitation energy (pp) or (pn) systems. A quantitative understanding of the values of A xx and A yy for the charge-exchange reaction is provided by impulse approximation calculations. The data suggest that spin-flip isospin-flip transitions, which dominate the charge-exchange breakup of the deuteron, are also important in the non-charge-exchange reaction.
Nuclear Physics A, 2000
The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungsze... more The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jülich. It enables the study of forward going ejectiles from proton-induced reactions at internal targets in COSY. First measurements of the double differential cross sections for the subthreshold K+-production in pA collisions have been performed at projectile energies as low as 1.0 GeV, i.e.
The European Physical Journal A, 2007
The production of ω-mesons in the pp → ppω reaction has been investigated with the COSY-ANKE spec... more The production of ω-mesons in the pp → ppω reaction has been investigated with the COSY-ANKE spectrometer for excess energies of 60 and 92 MeV by detecting the two final protons and reconstructing their missing mass. The large physical background was subtracted using an event-by-event transformation of the proton momenta between the two energies. Differential distributions and total cross sections were obtained after careful studies of possible systematic uncertainties in the overall ANKE acceptance. The results are compared with the predictions of theoretical models. Combined with data on the φ-meson, a more refined estimate is made of the Okubo-Zweig-Iizuka rule violation in the φ/ω production ratio.
A measurement of the vector analyzing power Ay of the pd --&amp;amp;gt; (pp) + n reaction... more A measurement of the vector analyzing power Ay of the pd --&amp;amp;gt; (pp) + n reaction was carried out at the ANKE spectrometer at COSY at beam energies of 0.5 and 0.8 GeV by detection of a fast forward proton pair of small excitation energy Epp &amp;amp;lt; 3 MeV. While at Tp = 0.8 GeV the measured analyzing power Ay
Journal of Physics: Conference Series, 2011
Spin observables in proton deuteron breakup reactions at low energies offer a rich testing ground... more Spin observables in proton deuteron breakup reactions at low energies offer a rich testing ground for the modern theory of nuclear forces, the chiral effective field theory (EFT). In the three-nucleon continuum the experimental data and the theoretical predictions are today at variance. At the PAX facility at COSY we plan to make an extensive study of analyzing powers and spin correlation parameters in pd breakup reactions at low energies between 30 and 50 MeV, an energy range where previous measurements are scarce and limited while three-nucleon effects are expected to be significant. Furthermore it is an ideal energy for the predictive power of chiral EFT to be tested. The longstanding physics question of the nature of three-nucleon forces will be studied with large coverage provided by an optimized silicon detector barrel, and flexibility utilizing the sampling method, a technique for direct comparison between experiment and theory developed specifically for the complex analysis of three-particle final states. The proposed experiment will yield an independent determination of the low-energy constants D and E and enable tests of appearing three-nucleon interactions in chiral EFT, with possible implications also for the spectra of light nuclei.
The first measurement of the pn → dω total cross section has been achieved at mean excess energie... more The first measurement of the pn → dω total cross section has been achieved at mean excess energies of Q ≈ 28 and 57 MeV by using a deuterium cluster-jet target. The momentum of the fast deuteron was measured in the ANKE spectrometer at COSY-Jülich and that of the slow "spectator" proton (psp) from the pd → pspdω reaction in a silicon telescope placed close to the target. The cross sections lie above those measured for pp → ppω but seem to be below theoretical predictions.
... Lett. B264 (1991) 269. 7. W. Abner, P. Baltes, Chr. Bormann, et al., Z. Phys. A341 (1991) 123... more ... Lett. B264 (1991) 269. 7. W. Abner, P. Baltes, Chr. Bormann, et al., Z. Phys. A341 (1991) 123. ... E. R6ssle and OWB Schult, ISSN 09386521,1993, pl. 9. W. Cassing. T. Demski, L. Jarczyk, B. Kamys, Z. Rudy, OWB Schult, A. Strzalkowski, Z. Phys. A, in press. 10. ...
The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungsze... more The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jülich. An initial scientific goal is to study K+-production in pA collisions at subthreshold energies below the free NN-threshold of T = 1.58 GeV. First measurements of double differential cross sections in p12C collisions at emission angles around 0° have been performed at T
A polarized antiproton beam at the Facility for Antiproton and Ion Research, proposed by the PAX ... more A polarized antiproton beam at the Facility for Antiproton and Ion Research, proposed by the PAX collaboration, will open a window to new physics uniquely accessible at the new High Energy Storage Ring. Our proposal to realize an asymmetric collider, in which polarized protons with momenta of about 3.5 GeV/c collide with polarized antiprotons with momenta up to 15 GeV/c, is well--suited to perform a direct measurement of the transversity distribution function h_1h_1h_1. In this report we summarize the outcome of various working group meetings within the PAX collaboration. The overall machine setup at the HESR, proposed by the PAX collaboration, is described along with the associated PAX experimental program.
We propose to use an internal polarized hydrogen storage cell gas target in the AD ring to determ... more We propose to use an internal polarized hydrogen storage cell gas target in the AD ring to determine for the first time the two total spin–dependent pbar-p cross sections σ1 and σ2 at antiproton beam energies in the range from 50 to 450 MeV. The data obtained are of interest by themselves for the general theory of pbar-p interactions since they will provide a first experimental constraint of the spin–spin dependence of the nucleon–antinucleon potential in the energy range of interest. In addition, measurements of the polarization buildup of stored antiprotons are required to define the optimum parameters of a future, dedicated Antiproton Polarizer Ring (APR), intended to feed a double–polarized asymmetric pbar-p collider with polarized antiprotons. Such a machine has recently been proposed by the PAX collaboration for the new Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, Germany. The availability of an intense stored beam of polarized antiprotons will provide ...
Physics Letters B, 2006
The pp → ppπ 0 differential cross section has been measured with the ANKE spectrometer at COSY-Jü... more The pp → ppπ 0 differential cross section has been measured with the ANKE spectrometer at COSY-Jülich for pion cms angles between 0 • and 15.4 • at a proton beam energy of 0.8 GeV. The selection of diproton pairs with an excitation energy E pp < 3 MeV ensures that the final pp system is dominantly in the spin-singlet 1 S 0 state. The kinematics are therefore very similar to those of pp → dπ + but with different spin and isospin transitions. The results will thus provide a crucial extra test of pion production models in nucleon-nucleon collisions.
Physics Letters B, 2006
Vector and tensor analysing powers of the dp → (pp)n (charge-exchange) and dp → (pn)p (non-charge... more Vector and tensor analysing powers of the dp → (pp)n (charge-exchange) and dp → (pn)p (non-charge-exchange) breakup reactions have been measured with the ANKE spectrometer at the COSY ring at a deuteron beam energy of 1170 MeV for small momentum transfers to the low excitation energy (pp) or (pn) systems. A quantitative understanding of the values of A xx and A yy for the charge-exchange reaction is provided by impulse approximation calculations. The data suggest that spin-flip isospin-flip transitions, which dominate the charge-exchange breakup of the deuteron, are also important in the non-charge-exchange reaction.
Nuclear Physics A, 2000
The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungsze... more The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jülich. It enables the study of forward going ejectiles from proton-induced reactions at internal targets in COSY. First measurements of the double differential cross sections for the subthreshold K+-production in pA collisions have been performed at projectile energies as low as 1.0 GeV, i.e.
The European Physical Journal A, 2007
The production of ω-mesons in the pp → ppω reaction has been investigated with the COSY-ANKE spec... more The production of ω-mesons in the pp → ppω reaction has been investigated with the COSY-ANKE spectrometer for excess energies of 60 and 92 MeV by detecting the two final protons and reconstructing their missing mass. The large physical background was subtracted using an event-by-event transformation of the proton momenta between the two energies. Differential distributions and total cross sections were obtained after careful studies of possible systematic uncertainties in the overall ANKE acceptance. The results are compared with the predictions of theoretical models. Combined with data on the φ-meson, a more refined estimate is made of the Okubo-Zweig-Iizuka rule violation in the φ/ω production ratio.
A measurement of the vector analyzing power Ay of the pd --&amp;amp;gt; (pp) + n reaction... more A measurement of the vector analyzing power Ay of the pd --&amp;amp;gt; (pp) + n reaction was carried out at the ANKE spectrometer at COSY at beam energies of 0.5 and 0.8 GeV by detection of a fast forward proton pair of small excitation energy Epp &amp;amp;lt; 3 MeV. While at Tp = 0.8 GeV the measured analyzing power Ay