In-Medium Effects on Phase Space Distributions of Antikaons Measured in Proton-Nucleus Collisions

Abstract

Differential production cross sections of K+/- mesons have been measured in p + C and p + Au collisions at 1.6, 2.5, and 3.5 GeV proton beam energy. At beam energies close to the production threshold, the K- multiplicity is strongly enhanced with respect to proton-proton collisions. According to microscopic transport calculations, this enhancement is caused by two effects: the strangeness exchange reaction NY --> K- NN and an attractive in-medium K- N potential at saturation density.

On the strangeness -1 S-wave meson-baryon scattering

“…Apart from that, these interactions are interrelated with many other interesting areas, as listed in ref. [21], e.g., possible kaon condensation in neutron-proton stars [26,27,28,29], large yields of K − in heavy ions collisions [30,31], kaonic atoms [32] or non-zero strangeness content of the proton [33,34].…”

Medium effects in proton-inducedK0production at 3.5 GeV

“…For the yield calculation an assumption is made that the contribution of theK 0 's to the K 0 S production is negligible. This assumption is justified by the estimate of the antikaon yield performed by the KaoS Collaboration in p + Au collisions at the same beam energy of 3.5 GeV: Y K − /Y K + = 2.3% [43]. Note that this value should be considered as an upper limit for the relative yield of antikaons for both p + p and p + Nb reactions, where in-medium effects, possibly enhancing the antikaon production, are either absent (p + p) or less pronounced (p + Nb) in comparison to p + Au reactions.…”

“…A comparison of the HADES p + Nb results with the data on K + production in p + 197 Au and p + 12 C collisions reported by the KaoS Collaboration at the same beam kinetic energy of 3.5 GeV [43] was made in terms of R Au/Nb (p) and R Nb/C (p) [defined in full analogy to R Nb/p (p)]. All relevant quantities are listed in Table III.…”

MARS15 code developments driven by the intensity frontier needs

“…Experimental data of the HARP collaboration [3] covers angles from 20° to 123°. This data could be also successfully fitted by the two-source model with χ 2 /n ~ 1 for any HARP momentum (3,5,8,12 GeV/c). If other measurements at large angles are included into fitting procedure, quality of the fit becomes slightly worse (χ 2 /n ~ 2), but still is acceptable.…”

“…The newest developments include: new and better approximations for elementary total, elastic, and inelastic cross sections for NN and πN interactions; several channels have been implemented for an explicit description: N+N→N+N+mπ, π+N→N+mπ (m<5), B+B→B+Y+K, π+B→Y+K, Kbar+B→Y+π, and K+Kbar, N+Nbar pair production; combination of the phase space and isobar models and experimental data; A reactions extended down to GDR and below; and an arbitrary light nuclear projectile (e.g., d) and nuclear target (e.g., He). Figure 3 shows comparison of calculated kaon spectra with experimental data [5].…”