Angular dependence of pp spin correlation and rescattering observables between 1.80 and 2.10 GeV

A polarized proton beam extracted from SATURNE II and the Saclay polarized proton target were used to determine the spin correlation parameter Aoosk and the rescattering observablesK _os″ so; D_os″ok, N_os″sn, andN _onsk at 1.80 and 2.10 GeV. The beam polarization was oriented perpendicular to the beam direction in the horizontal scattering plane and the target polarization was directed either along the vertical axis or longitudinally. Left-right and up-down asymmetries in the second scattering were measured. A check for the beam optimization with the beam and target polarizations oriented vertically provided other observables, of which results forD _onon andK _onno at 1.80, 1.85, 2.04, and 2.10 GeV are listed here. The new data at 2.10 GeV suggest a smooth energy dependence of spin triplet scattering amplitudes at fixed angles in the vicinity of this energy.     

Elastic and quasi-elastic pp scattering in ^6LiH and ^6LiD targets between 1.1 and 2.4 GeV

A polarized proton beam extracted from SATURNE II, the Saclay polarized target with Li compounds, and a target were used to measure elastic and quasi-elastic pp spin-dependent observables in the angular region . The beam and/or target polarizations were oriented vertically. Accurate pp data for the analyzing power , spin-correlation parameter , and the polarization transfer were measured at 1.1 GeV. The observables and were determined at six other energies between 1.6 and 2.4 GeV. At 1.6 GeV, was also obtained. The individual contributions from H, Li, and LiD were deduced. The target provided results on free hydrogen and on protons in carbon. The elastic and quasi-elastic observables are compared with existing data and with phase-shift analysis predictions. Received: 19 April 1999 / Published online: 14 October 1999     

Regge approach to charged pion photoproduction at invariant energies above 2 GeV

A Regge model with absorptive corrections is employed in a global analysis of the world data on positive and negative pion photoproduction for photon energies from 3 to 8GeV. In this region resonance contributions are expected to be negligible so that the available experimental information on differential cross-sections and single polarization observables at - t ⩽ 2 GeV^2 allows us to determine the non-resonant part of the reaction amplitude reliably. The model amplitude is then used to predict observables for photon energies below 3GeV. Differences between our predictions and data in this energy region are systematically examined as possible signals for the presence of excited baryons. We find that the data available for the polarized photon asymmetry show promising resonance signatures at invariant energies around 2GeV. With regard to differential cross-sections the analysis of negative pion photoproduction data, obtained recently at JLab, indicates likewise the presence of resonance structures around 2GeV.     

Quasi-free scattering in the 3-N continuum

The interaction of a nucleon with the deuteron leading to break-up at the quasi-free scattering (QFS) condition is studied atE _N ^lab =12.0, 22.7, 68.0, and 140.0 MeV. Results of rigorous Faddeev calculations and of the impulse approximation (IA) are compared at these energies for bothn-p andp-p QFS in order to study the importance of rescattering terms. For the two-nucleon interaction the Paris potential is used. It is restricted to act in two-body states with total angular momentumj2. Also we compare the Faddeev calculations with experimental data for the QFS cross section and analyzing powerA _y and find overall agreement. The behaviour of scattering observables turns out to be different forn-p andp-p QFS. Also the energy dependence of rescattering terms is different in the two cases. For all energies studied the IA is not reliable.     

Measurement of the spin correlationA ookk innp elastic scattering between 0.63 and 1.08 GeV

We present the measurements of the spin correlation parameterA _ookk (np). A longitudinally polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the longitudinally polarized Saclay frozen-spin proton target. Measurements were carried out at SATURNE II, at neutron beam kinetic energies of 0.63, 0.88, 0.98 and 1.08 GeV. The data points cover the angular region from about 40° to 110° CM. The observed angular dependence ofA _ookk (np) at 0.63 GeV agree with the phase shift analysis predictions except at small angles.     

Measurements of the np total cross section difference DsL\Delta \sigma_L at 1.59, 1.79 and 2.20 GeV

New results of the neutron-proton spin-dependent total cross section difference at the neutron beam kinetic energies 1.59, 1.79 and 2.20 GeV are presented. Measurements were performed at the Synchrophasotron of the Laboratory of High Energies of the Joint Institute for Nuclear Research in Dubna. A quasi-monochromatic neutron beam was produced by break-up of extracted polarized deuterons. Neutrons were transmitted through a large polarized proton target. Measurements were performed either with a parallel or an antiparallel beam and target polarizations, both oriented along the beam momentum. The results at the two higher energies were measured with two opposite beam and target polarization directions. Only one target polarization direction was available at 1.59 GeV. The present measurements agree well with existing data. A fast decrease of the values with increasing energy above 1.1 GeV was confirmed. The new results are also compared with model predictions and with phase shift analysis fits. The quantities for isosinglet state I=0, deduced from the measured values and known data, are given. Received: 19 August 1999 / Published online: 3 February 2000     

Developing a generalized diffraction model for elastic pd scattering at intermediate energies

A generalization of the Glauber-Sitenko diffraction model that includes the spin dependence of NN amplitudes, the D-wave of the deuteron, and the charge exchange effects is constructed for elastic pd scattering at intermediate energies. The developed model was used to analyze differential cross sections and some spin observables (analyzing powers) at the incident proton energies T _p = 1 GeV, 440 and 250 MeV. It was shown that predictions of the generalized diffraction model agree both with the experimental data and with the exact Faddeev calculations at low transfer momenta.     

Quasi-elastic pn scattering in ^6LiD and ^6LiH targets from 1.1 to 2.4 GeV

A polarized proton beam from SATURNE II, the Saclay polarized targets with Li compounds, and an unpolarized target were used to measure spin-dependent observables for protons scattered on bound nucleons. The beam and target polarizations were oriented vertically. The analyzing power and the depolarization were determined at seven energies between 1.1 and 2.4 GeV. The spin correlation parameter was measured at only 1.1 and 1.6 GeV. Measurements with the target at 1.1 GeV provided data for scattering of polarized protons on neutrons in carbon. The quasi-elastic observables are compared with previous elastic scattering measurements and at 1.1 GeV with predictions of phase shift analyses. Received: 19 April 1999 / Published online: 28 September 1999     

General features ofK + d interactions at 70 GeV/c

We have studied 70 GeV/cK ⁺ d interactions from about 10 K events. The inelastic cross-section for three or more prongs is found to be (28.9±0.4) mb. From odd-and even-prong topologies we have extracted topological break-up ofK ⁺ n interactions by taking into account spectator corrections, rescattering effects and Glauber screening. The rescattering fraction is found to be 0.06±0.01 which is substantially different from pion and proton interactions. Combining ourK ⁺ n data with other existing π^± n andp ^±n we find〈n _ch 〉 ^ph ?〈n _ch 〉 ^hn =0.33±0.04 andD/〈n _ch 〉=0.529±0.003.     

Backward pion-nucleon scattering

A global analysis of the world data on differential cross-sections and polarization asymmetries of backward pion-nucleon scattering for invariant collision energies above 3GeV is performed in a Regge model. Including the N_a\ensuremath N_{\alpha} , N_g\ensuremath N_{\gamma} , D_d\ensuremath \Delta_{\delta} and D_b\ensuremath \Delta_{\beta} trajectories, we reproduce both angular distributions and polarization data for small values of the Mandelstam variable u , in contrast to previous analyses. The model amplitude is used to obtain evidence for baryon resonances with mass below 3GeV. Our analysis suggests a G₃₉\ensuremath G_{39} -resonance with a mass of 2.83GeV as member of the D_b\ensuremath \Delta_{\beta} -trajectory from the corresponding Chew-Frautschi plot.     

Nucleon spin-polarisabilities from polarisation observables in low-energy deuteron Compton scattering

We investigate the dependence of polarisation observables in elastic deuteron Compton scattering below the pion production threshold on the spin-independent and spin-dependent iso-scalar dipole polarisabilities of the nucleon. The calculation uses Chiral Effective Field Theory (c \chi EFT) with dynamical D \Delta(1232) degrees of freedom in the Small Scale Expansion (SSE) at next-to-leading order. Resummation of the NN intermediate rescattering states and including the D \Delta induces sizeable effects. The analysis considers cross-sections and the analysing power of linearly polarised photons on an unpolarised target, and cross-section differences and asymmetries of linearly and circularly polarised beams on a vector-polarised deuteron. An intuitive argument helps one to identify kinematics in which one or several polarisabilities do not contribute. Some double-polarised observables are only sensitive to linear combinations of two of the spin-polarisabilities, simplifying a multipole analysis of the data. Spin-polarisabilities can be extracted at photon energies ≳ 100 MeV, after measurements at lower energies of <~ \lesssim 70 MeV provide high-accuracy determinations of the spin-independent ones. An interactive Mathematica 7.0 notebook of our findings is available from hgrie@gwu.edu.     

Relations between polarization observables and complete sets for deuteron photodisintegration

The polarization observables for deuteron photodisintegration are given as Hermitean forms of theT-matrix elementst _i . By inversion we are able to express a given productt _i ^* t _j in terms of polarization observables. This allows (i) to derive linear relations between observables for unpolarized, circularly and linearly polarized photons, (ii) to construct explicitly complete sets of polarization observables, and (iii) to derive quadratic relations between observables.Supported by the Deutsche Forschungsgemeinschaft (SFB 201)     

K<Superscript>+</Superscript> production in proton-nucleus reactions and the role of momentum-dependent potentials

The production of K⁺-mesons in proton-nucleus collisions from 1.0 to 2.5GeV is analyzed with respect to one-step nucleon-nucleon ( NN → NYK ⁺) and two-step Δ-nucleon ( ΔN → K ⁺ YN) or pion-nucleon ( πN → K ⁺ Y) production channels on the basis of a coupled-channel transport approach (CBUU) including the kaon final-state interactions. The influence of momentum-dependent potentials for the nucleon, hyperon and kaon in the final state are studied as well as the importance of K⁺ elastic rescattering in the target nucleus. The transport calculations are compared to the experimental K⁺ spectra taken at LBL Berkeley, SATURNE, CELSIUS, GSI and COSY-Jülich. It is found that the momentum-dependent baryon potentials affect the excitation function of the K⁺ cross-section; at low bombarding energies of ∼ 1.0GeV the attractive baryon potentials in the final state lead to a relative enhancement of the kaon yield, whereas the net repulsive potential at bombarding energies ∼ 2GeV causes a decrease of the K⁺ cross-section. Furthermore, it is pointed out that especially the K⁺ spectra at low momenta (or kinetic energy T _K) allow to determine the in-medium K⁺ potential almost model independently due to a relative shift of the K⁺ spectra in kinetic energy that arises from the acceleration of the kaons when propagating out of the nuclear medium to free space, i.e. converting the potential energy to the kinetic energy of the free kaon. Received: 28 January 2002 / Accepted: 3 June 2002 / Published online: 19 November 2002 RID="a" ID="a"e-mail: Wolfgang.Cassing@theo.physik.uni-giessen.de Communicated by P. Schuck     

Measurement of the spin parameters A and Ann in pp elastic scattering in the 1–3 GeV/c region

We have measured the asymmetry parameter A and the spin correlation parameter A_nn in pp elastic scattering, using the Argonne ZGS polarized proton beam and a polarized proton target. Angular distributions of A and A_nn for |t| ? 0.2 (GeV/c)²wereobtainedateightmomentabetween 1.10 and 2if2.75 GeV/c. We find significant structure in both the energy and t-dependence of A_nn at these energies. At p_lab ≈ 1.34 GeV/cA_nn reaches a very large value of about 0.8–0.9 near θ_cm = 90°.     

Chiral SU(4) × SU(4) breaking: masses and decay constants of charmed hadrons

The (4, 4*) ⊕ (4*, 4) model of broken chiral SU (4) × SU (4) symmetry has been used to calculate the third-order coupling constants involving charmed and ordinary pseudoscalar mesons. These coupling constants are exploited to derive some interesting new relations among the masses and decay constants of these charmed particles. Using the known masses and decay constants as inputs, we exploit these relations to predict:F _D = −1·41F _π ,F _F = −1·13F _π ,F _D/F_F = 1·25,m(D _s) = 1·43 GeV,m(F _s) = 1·39 GeV andm(K _s) = 1·02 GeV.     

Measurements of the total-cross-section difference ΔσL(np) at 1.39, 1.69, 1.89, and 1.99 GeV

New accurate data of the neutron-proton spin-dependent total-cross-section difference Δσ _L(np) at the neutron-beam kinetic energies 1.39, 1.69, 1.89, and 1.99 GeV are presented. In general, these data complete the measurements of energy dependence of Δσ _L(np) over the Dubna Synchrophasotron energy region. Measurements were carried out at the Synchrophasotron of the Veksler and Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research. The quasi-monochromatic neutron beam was produced by breakup of extracted polarized deuterons. The deuteron (and hence neutron) polarization direction was flipped every accelerator burst. The initial transverse (with respect to beam momentum) neutron polarization was changed to a longitudinal one and longitudinally polarized neutrons were transmitted through the large proton longitudinally polarized target. The target polarization direction was inverted after one to two days of measurements. Four different combinations of the beam and target parallel and antiparallel polarization directions, both oriented along the neutron-beam momentum, were used at each energy. A fast decrease in −Δσ _L(np) with increasing energy above 1.1 GeV and a structure in the energy dependence around 1.8 GeV, first observed from our previous data, seem to be well revealed. The new results are also compared with model predictions and with phase-shift analysis fits. The Δσ _L quantities for isosinglet state I = 0, deduced from the measured Δσ _L(np) values and known Δσ _L(pp) data, are also given. The results of the measurements of unpolarized total cross sections σ _0tot(np) at 1.3, 1.4, and 1.5 GeV and σ _0tot(nC) at 1.4 and 1.5 GeV are presented as well. These data were obtained using the same apparatus and high-intensity unpolarized deuteron beams extracted either from the Synchrophasotron or from the Nuclotron. From Yadernaya Fizika, Vol. 68, No. 11, 2005, pp. 1858–1873. Original English Text Copyright ? 2005 by Sharov, Anischenko, Antonenko, Averichev, Azhgirey, Bartenev, Bazhanov, Belyaev, Blinov, Borisov, Borzakov, Borzunov, Bushuev, Chernenko, Chernykh, Chumakov, Dolgii, Fedorov, Fimushkin, Finger, Finger, Jr., Golovanov, Gurevich, Janata, Kirillov, Kolomiets, Komogorov, Kovalenko, Kovalev, Krasnov, Krstonoshich, Kuzmin, Ladygin, Lazarev, Lehar, de Lesquen, Liburg, Livanov, Lukhanin, Maniakov, Matafonov, Matyushevsky, Moroz, Morozov, Neganov, Nikolaevsky, Nomofilov, Panteleev, Pilipenko, Pisarev, Plis, Polunin, Prokofiev, Prytkov, Rukoyatkin, Schedrov, Schevelev, Shilov, Shindin, Slunečka, Slunečková, Starikov, Stoletov, Strunov, Svetov, Usov, Vasiliev, Volkov, Vorobiev, Yudin, Zaitsev, Zhdanov, Zhmyrov.     

Measurement of spin-transfer observables in p p-->Lambda Lambda at 1.637 GeV/c

Spin-transfer observables for p p-->Lambda Lambda have been measured using a transversely polarized frozen-spin target and a beam momentum of 1.637 GeV/c. Current models of the reaction near threshold are in good agreement with existing measurements performed with unpolarized particles in the initial state but produce conflicting predictions for the spin-transfer observables Dnn and Knn (the normal-to-normal depolarization and polarization transfer), which are measurable only with polarized target or beam. Measurements of Dnn and Knn presented here are found to be in disagreement with predictions from these models.     

Measurement of the beam asymmetry Σ in πeta; production off the proton with the CBELSA/TAPS experiment?

In photoproduction experiments, a large number of final states yielding various resonance contributions are accessible. To extract resonance parameters via partial-wave analysis not only the measurement of differential cross-sections is necessary, but also the determination of polarization observables. At the electron accelerator ELSA (Bonn) the coherent bremsstrahlung method was used to generate a linearly polarized photon beam. Using the CBELSA/TAPS detector setup, the beam asymmetry Σ in the reaction γp → pπ⁰η was determined as a function of various masses and angles for photon energies between 970MeV and 1650MeV.     

Proton distributions in the target fragmentation region in proton-nucleus and nucleus-nucleus collisions at high energies

We present measurements of the rapidity and transverse-momentum distributions of the protons emitted in S+W, O+W, andp+W reactions at 200 GeV/A around the target rapidity (y=1). The rapidity density rises linearly with the transverse energy for all three systems, but the slope forp+W is much steeper than for O+W and S+W. The rapidity density forp+W is much higher than predicted by summing single nucleonnucleon collisions without any nuclear effects, indicating substantial rescattering of the produced particles. The predictions of the VENUS 3 model, including rescattering, show reasonable agreement with the data for all three systems. We do not have evidence for a strong collective flow of the outgoing particles.     

Off-shell effects inpp↔πd spin observables

We show that spin observables inppd are fairly sensitive to small changes in the off-shell N helicity amplitudes. This is illustrated at proton laboratory kinetic energies ofT _p=515 MeV andT _p=578 MeV. A reduction of the helicity-flip amplitude by 13% brings the predictions of the relativistic rescattering model much closer to experiment.