We present the first determination of the energy-dependent amplitudes of N⁎ resonances extracted from their decay in KΛ pairs in p+p→pK+Λ reactions. A combined Partial Wave Analysis of seven data ...samples with exclusively reconstructed p+p→pK+Λ events measured by the COSY-TOF, DISTO, FOPI and HADES Collaborations in fixed target experiments at kinetic energies between 2.14 to 3.5 GeV is used to determine the amplitude of the resonant and non-resonant contributions into the associated strangeness final state. The contribution of seven N⁎ resonances with masses between 1650 MeV/c2 and 1900 MeV/c2 for an excess energy between 0 and 600 MeV has been considered. The Σ–p cusp and final state interactions for the p–Λ channel are also included as coherent contributions in the PWA. The N⁎ contribution is found to be dominant with respect to the phase space emission of the pKΛ+ final state at all energies demonstrating the important role played by both N⁎ and interference effects in hadron–hadron collisions.
.
The production of K
+
, K
-
and
(1020) mesons is studied in Al+Al collisions at a beam energy of 1.9A GeV which is close to or below the production threshold in NN reactions. Inverse slopes, ...anisotropy parameters, and total emission yields of K
±
mesons are obtained. A comparison of the ratio of kinetic energy distributions of K
-
and K
+
mesons to the HSD transport model calculations suggests that the inclusion of the in-medium modifications of kaon properties is necessary to reproduce the ratio. The inverse slope and total yield of
mesons are deduced. The contribution to K
-
production from
meson decays is found to be
%. The results are in line with the previous K
±
and
data obtained for different colliding systems at similar incident beam energies.
SiΛvio: A trigger for Λ-hyperons Münzer, Robert; Berger, Martin; Fabbietti, Laura ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2014, Letnik:
745
Journal Article
Recenzirano
Odprti dostop
As online trigger for events containing Λ hyperons in p+p collisions at 3.1GeV a silicon-based device has been designed and built. This system has been integrated close to the target region within ...the FOPI spectrometer at GSI and was also employed as a tracking device to improve the vertex reconstruction of secondary decays. The design of the detector components, read-out, the trigger capability as well as the tracking performance are presented. An enrichment factor of about 14 was achieved for events containing a Λ-hyperon candidate.
The FOPI Collaboration at the GSI SIS-18 synchrotron measured charged kaons from central and semi-central collisions of Ni+Ni at a beam energy of 1.91A GeV. We present the distribution of the ...K\(^-\)\K\(^+\) ratio on the energy vs polar angle plane in the nucleon-nucleon center-of-mass frame, with and without subtraction of the contribution of \(\phi\)(1020) meson decays to the K\(^-\) yield. The acceptance of the current experiment is substantially wider compared to the previous measurement of the same colliding system. The ratio of K\(^-\) to K\(^+\) energy spectra is expected to be sensitive to the in-medium modifications of basic kaon properties like mass. Recent results obtained by the HADES Collaboration at 1.23A and 1.76A GeV indicate that after inclusion of the \(\phi\) meson decay contribution to the K\(^-\) production no difference between the slopes of the K\(^-\) and K\(^+\) energy spectra is observed within uncertainties. For our data a linear fit to this ratio obtained after subtraction of the \(\phi\) meson contribution still shows a decrease with kinetic energy, although a constant value cannot be rejected. The contribution of \(\Lambda(1520) \rightarrow p\text{K}^-\) decays estimated from fitting the thermal model to the experimental yields appears to be another factor of moderate relevance.
We present the first determination of the energy-dependent production amplitudes of N\(^{*}\) resonances with masses between 1650 MeV/c\(^{2}\) and 1900 MeV/c\(^{2}\) for an excess energy between ...\(0\) and \(600\) MeV. A combined Partial Wave Analysis of seven exclusively reconstructed data samples for the reaction p+p \(\rightarrow pK\Lambda\) measured by the COSY-TOF, DISTO, FOPI and HADES collaborations in fixed target experiments at kinetic energies between 2.14 and 3.5 GeV is used to determine the amplitude of the resonant and non-resonant contributions.
Phys. Rev. C 94, 014901 (2016) We analysed the $\phi$ meson production in central Ni+Ni collisions at the
beam kinetic energy of 1.93A GeV with the FOPI spectrometer and found the
production ...probability per event of $8.6 ~\pm~ 1.6 ~(\text{stat}) \pm 1.5
~(\text{syst}) \times 10^{-4}$. This new data point allows for the first time
to inspect the centrality dependence of the subthreshold $\phi$ meson
production in heavy-ion collisions. The rise of $\phi$ meson multiplicity per
event with mean number of participants can be parameterized by the power
function with exponent $\alpha = 1.8 \pm 0.6$. The ratio of $\phi$ to
$\text{K}^-$ production yields seems not to depend within the experimental
uncertainties on the collision centrality, and the average of measured values
was found to be $0.36 \pm 0.05$.
$\phi$ and K$^-$ mesons from Ni+Ni collisions at the beam energy of 1.91A GeV
have been measured by the FOPI spectrometer, with a trigger selecting central
and semi-central events amounting to 51% of ...the total cross section. The phase
space distributions, and the total yield of K$^-$, as well as the kinetic
energy distribution and the total yield of $\phi$ mesons are presented. The
$\phi$\K$^-$ ratio is found to be $0.44 \pm 0.07(\text{stat}) ^{+0.18}_{-0.12}
(\text{syst})$, meaning that about 22% of K$^-$ mesons originate from the
decays of $\phi$ mesons, occurring mostly in vacuum. The inverse slopes of
direct kaons are up to about 15 MeV larger than the ones extracted within the
one-source model, signalling that a considerable share of gap between the
slopes of K$^+$ and K$^-$ could be explained by the contribution of $\phi$
mesons to negative kaons.
Azimuthal emission patterns of $K^\pm$ mesons have been measured in Ni + Ni
collisions with the FOPI spectrometer at a beam kinetic energy of 1.91 A GeV.
The transverse momentum $p_{T}$ integrated ...directed and elliptic flow of
$K^{+}$ and $K^{-}$ mesons as well as the centrality dependence of $p_{T}$ -
differential directed flow of $K^{+}$ mesons are compared to the predictions of
HSD and IQMD transport models. The data exhibits different propagation patterns
of $K^{+}$ and $K^{-}$ mesons in the compressed and heated nuclear medium and
favor the existence of a kaon-nucleon in-medium potential, repulsive for
$K^{+}$ mesons and attractive for $K^{-}$ mesons.
We analysed the \(\phi\) meson production in central Ni+Ni collisions at the beam kinetic energy of 1.93A GeV with the FOPI spectrometer and found the production probability per event of \(8.6 ~\pm~ ...1.6 ~(\text{stat}) \pm 1.5 ~(\text{syst}) \times 10^{-4}\). This new data point allows for the first time to inspect the centrality dependence of the subthreshold \(\phi\) meson production in heavy-ion collisions. The rise of \(\phi\) meson multiplicity per event with mean number of participants can be parameterized by the power function with exponent \(\alpha = 1.8 \pm 0.6\). The ratio of \(\phi\) to \(\text{K}^-\) production yields seems not to depend within the experimental uncertainties on the collision centrality, and the average of measured values was found to be \(0.36 \pm 0.05\).
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