Subthreshold and near-threshold kaon and antikaon production in proton–nucleus reactions

Abstract

The differential production cross sections of K + and K − mesons have been measured at the ITEP proton synchrotron in p + Be, p + Cu collisions under lab angle of 10.5 • , respectively, at 1.7 and 2.25, 2.4 GeV beam energies. A detailed comparison of these data with the results of calculations within an appropriate folding model for incoherent primary proton-nucleon, secondary pion-nucleon kaon and antikaon production processes and processes associated with the creation of antikaons via the decay of intermediate phi mesons is given. We show that the strangeness exchange process Y N → N N K − gives a small contribution to the antikaon yield in the kinematics of the performed experiment. We argue that in the case when antikaon production processes are dominated by the channels with KK − in the final state, the cross sections of the corresponding reactions are weakly influenced by the in-medium kaon and antikaon mean fields.

Meson–nucleus potentials and the search for meson–nucleus bound states

“…The in-medium modifications of K − meson properties have also been studied experimentally in proton-nucleus reactions at beam energies close to or below the production threshold in N N collisions over the last years (see, for example, [46,58,64,166,167]). The advantage of such reactions compared to heavy-ion collisions is that the processes of hadron production and propagation proceed in cold static nuclear matter of well-defined density at zero temperature.…”

“…Measurements of inclusive antikaon momentum distributions from 0.6 to 1.3 GeV/c at a laboratory angle of 10.5 • in pBe and pCu interactions at 2.25 and 2.4 GeV beam energy have been performed at the ITEP/Moscow accelerator [58]. A reasonable description of these data has been achieved in the framework of a folding model, assuming vacuum K + , K − masses [58]. These calculations, based on the target nucleon momentum distribution and on free elementary cross sections, consider incoherent primary proton-nucleon, secondary pion- Figure 30: Ratio of invariant production cross sections of K − over K + mesons for inclusive p-Au (left) and p-C (right) collisions as a function of transverse mass.…”

Momentum dependence of pion-induced ϕ meson production on nuclei near threshold

“…(21), (32)-(59) for incident pion momentum of 1.7 GeV/c, for laboratory φ production angles of 10 • -45 • and for φN absorption cross section of 10 mb. The in-medium mass shifts at saturation density ρ 0 for the φ meson as well as for the secondary nucleons, produced in the channels (1), (29)- (31) and (23), (24), (25)- (28), were chosen in the calculations as -20, 25 and -60 MeV, respectively. These dependences are shown in Fig.…”

“…Consequently, accounting for the Fermi motion of intranuclear nucleons, this channel may contribute to the φ production on nuclei. In our calculations of this production we have neglected the elementary processes π − p → π 0 n, π − p → 2π 0 n, π − N → 3πN , since their cross sections at a beam momentum of 1.7 GeV/c are expected to be essentially less [49] than those of reactions (23), (24) and (25)- (28), which are shown (for free space) in Figs. 1-6 given below.…”

“…φ production in nuclei has also been intensively studied theoretically in proton-nucleus [19,20,[24][25][26][27][28] and photon-nucleus [29][30][31][32][33] reactions, with the aim of getting information on possible modification of the φ spectral function in cold nuclear matter. Unique information on the in-medium properties of light vector mesons, complementary to that from nucleus-nucleus, proton-nucleus and photon-nucleus collisions, can be deduced from pion-nucleus reactions [34,35].…”