Medium effects in λK ⁺ pair production by 2.83 GeV protons on nuclei

Abstract

We study ΛK + pair production in the interaction of protons of 2.83 GeV kinetic energy with C, Cu, Ag, and Au target nuclei in the framework of the nuclear spectral function approach for incoherent primary proton-nucleon and secondary pion-nucleon production processes, and processes associated with the creation of intermediate Σ 0 K + pairs. The approach accounts for the initial proton and final Λ hyperon absorption, final K + meson distortion in nuclei, target nucleon binding, and Fermi motion, as well as nuclear mean-field potential effects on these processes. We calculate the Λ momentum dependence of the absolute ΛK + yield from the target nuclei considered, in the kinematical conditions of the ANKE experiment, performed at COSY, within the different scenarios for the Λ-nucleus effective scalar potential. We show that the above observable is appreciably sensitive to this potential in the low-momentum region. Therefore, direct comparison of the results of our calculations with the data from the ANKE-at-COSY experiment can help to determine the above potential at finite momenta. We also demonstrate that the two-step pion-nucleon production channels dominate in the lowmomentum ΛK + production in the chosen kinematics and, therefore, they have to be taken into account in the analysis of these data.

Near-threshold K*(892)+ meson production in the interaction of π− mesons with nuclei

“…The study of the modification of the hadronic properties (masses and widths) of light non-strange vector mesons, , , ; light strange pseudoscalar mesons K and ; pseudoscalar mesons, , ; as well as open and hidden charm mesons D and in a strongly interacting environment has received considerable interest in recent years owing to the expectation to observe a partial restoration of chiral symmetry in a nuclear medium (see, for example, [1][2][3][4][5][6][7][8][9][10][11][12][13]). The in-medium properties of hyperons at finite density have also been a matter of intense theoretical investigations in the last two decades [14][15][16][17][18][19][20][21][22][23][24]. Another interesting case of medium renormalization of hadrons is that of the strange vector and axial-vector mesons with the same charge states (or with the same quark structure or with ); for these mesons, the in-medium mass difference, as is expected [25][26][27], is sensitive to the chiral order parameter, giving rise to the possibility to identify unambiguously the effect of the breaking of chiral symmetry in a nuclear medium.…”

“…MeV throughout the study. Following the predictions of the chiral effective field theory approach [18,40] and the SU(6) quark model [41,42] for the fate of hyperons in nuclear matter and phenomenological information deduced from hypernuclear data [6,43], i.e., that the hyperon experiences only a moderately repulsive nuclear potential of about 10-40 MeV at central nuclear densities and finite momenta as well as a weakly attractive potential at the surface of the nucleus, we will Chinese Physics C Vol. 44, No.…”

“…cross sections , calculated in line with Eqs (11),(12),. and(18) for pion momenta of 1.4 and 1.7 GeV/c, a target proton bound in C by16 MeV, and with relevant internal momenta of 500 and 250 MeV/c, are about 28 and 35 μb, respectively2) . This opens up the possibility of measuring the yield inChinese Physics C Vol.…”