We report on the first measurement of \(p\Lambda\) and \(pp\) correlations via the femtoscopy method in p+Nb reactions at \(\mathrm{\sqrt{s_{NN}}=3.18} ~\mathrm{GeV}\), studied with the High ...Acceptance Di-Electron Spectrometer (HADES). By comparing the experimental correlation function to model calculations, a source size for \(pp\) pairs of \(r_{0,pp}=2.02 \pm 0.01(\mathrm{stat})^{+0.11}_{-0.12} (\mathrm{sys}) ~\mathrm{fm}\) and a slightly smaller value for \(p\Lambda\) of \(r_{0,\Lambda p}=1.62 \pm 0.02(\mathrm{stat})^{+0.19}_{-0.08}(\mathrm{sys}) ~\mathrm{fm}\) is extracted. Using the geometrical extent of the particle emitting region, determined experimentally with \(pp\) correlations as reference together with a source function from a transport model, it is possible to study different sets of scattering parameters. The \(p\Lambda\) correlation is proven sensitive to predicted scattering length values from chiral effective field theory. We demonstrate that the femtoscopy technique can be used as valid alternative to the analysis of scattering data to study the hyperon-nucleon interaction.
North Atlantic Marine Mammals Waring, Gordon T.; Palka, Debra L.; Evans, Peter G.H.
Encyclopedia of Marine Mammals,
2009, 20090000
Book Chapter, Reference
Marine mammals are a diverse, widespread, and significant component of North Atlantic marine ecosystems. Four of the five commonly recognized marine mammal taxa reside in the North Atlantic: ...cetaceans, sirenians, pinnipeds, and polar bears. A fifth taxon and sea and sea lions and fur seals (family Otariidae) have not inhabited the North Atlantic since at least the late Pleistocene. The systematics of marine mammals is still being disputed. Marine mammals occupy all North Atlantic marine regimes, tropical to polar, although species-specific ranges exist and distribution patterns are not uniform. The large-scale, nonrandom distribution of marine mammals is influenced by oceanographic features, whereas small-scale distributions are influenced by factors such as the animal's physiology, behavior, and ecology. The physical characteristics of the North Atlantic ecosystem critically influence marine mammal distribution. Although the ocean basin provides marine mammals with an open pathway that extends from the equator northward to the Arctic and includes adjacent bodies of water, the North Atlantic has many different ecosystems. Some adjacent seas, such as the Baltic and Mediterranean, are more isolated from the open ocean and form separate ecosystems. Baleen whales are widely distributed in the North Atlantic, with individual species exhibiting preferences for certain ecosystems. Centuries of human activities have affected all North Atlantic marine mammal populations. Prehistoric people hunted coastal marine mammals for subsistence use, and in some areas aboriginal hunting still exists. Commercial exploitation of smaller cetaceans began in the fourteenth century when the Danes initiated organized hunts of Baltic Sea harbor porpoises.
We study the production of Sigma^+-pi^+-pK^+ particle quartets in p+p reactions at 3.5 GeV kinetic beam energy. The data were taken with the HADES experiment at GSI. This report evaluates the ...contribution of resonances like Lambda(1405$, Sigma(1385)^0, Lambda(1520), Delta(1232), N^* and K^*0 to the Sigma^+- pi^-+ p K+ final state. The resulting simulation model is compared to the experimental data in several angular distributions and it shows itself as suitable to evaluate the acceptance corrections properly.
The aim of the present analysis is to determine the relative production cross
sections of the $\Lambda$(1405) and $\Sigma(1385)^{0}$ resonances in p+p
collisions at E$_{kin}$=3.5 GeV measured with ...HADES. Upper and lower limits
have been determined for the ratio
$\sigma_{(\Sigma(1385)^{0}+p+K^{+})}/\sigma_{(\Lambda(1405)+p+K^{+})}=0.76_{-0.26}^{+0.54}$.
The knowledge of this ratio is an essential input for the analysis of the decay
$\Lambda(1405)\rightarrow\Sigma^{\pm}\pi^{\mp}$, where an unambiguous
separation of the $\Lambda$(1405) and $\Sigma(1385)^{0}$ signals is not
possible.
We present the inclusive invariant-mass, transverse momentum and rapidity distributions of dielectrons (e\(^{+}\)e\(^{-}\) pairs) in p+p interactions at 3.5 GeV beam kinetic energy. In the ...vector-meson mass region, a distinct peak corresponding to direct \(\omega\) decays is reconstructed with 2% mass resolution. The data is compared to predictions from three model calculations. Due to the large acceptance of the HADES apparatus for \(e^{+}e^{-}\) invariant masses above 0.2 GeV/\(c^{2}\) and for transverse pair momenta p\(_{t}\) \( <\) 1 GeV/\(c\), acceptance corrections are to a large extent model independent. This allows us to extract from dielectron data for the first time at this energy the inclusive production cross sections for light vector mesons. Inclusive production cross sections for \(\pi^o\) and \(\eta\) mesons are also reported. The obtained results will serve as an important reference for the study of vector meson production in proton-nucleus and heavy-ion collisions. Furthermore, using this data, an improved value for the upper bound of the branching ratio for direct \(\eta\) decays into the electron-positron channel is obtained.
We present results of an exclusive measurement of the first excited state of the Sigma hyperon, Sigma(1385)^+, produced in p+p -> Sigma^+ + K^+ + n at 3.5 GeV beam energy. The extracted data allow to ...study in detail the invariant mass distribution of the Sigma(1385)^+. The mass distribution is well described by a relativistic Breit-Wigner function with a maximum at m_0 = 1383.2 +- 0.9 MeV/c^2 and a width of 40.2 +- 2.1 MeV/c^2. The exclusive production cross-section comes out to be 22.27 +- 0.89 +- 1.56 +3.07 -2.10 mu b. Angular distributions of the Sigma(1385)^+ in different reference frames are found to be compatible with the hypothesis that 33 % of Sigma(1385)^+ result from the decay of an intermediate Delta^{++} resonance.
The J-PET tomograph is constructed from plastic scintillator strips arranged axially in concentric cylindrical layers. It enables investigations of positronium decays by measurement of the time, ...position, polarization and energy deposited by photons in the scintillators, in contrast to studies conducted so far with crystal and semiconductor based detection systems where the key selection of events is based on the measurement of the photons energies. In this article we show that the J-PET tomograph system is capable of exclusive measurements of the decays of ortho-positronium atoms. We present the first positronium production results, its lifetime distribution measurements and discuss estimation of the influence of various background sources. The tomograph s performance demonstrated here makes it suitable for precision studies of positronium decays including entanglement of the final state photons, positron annihilation lifetime spectroscopy plus molecular imaging diagnostics.
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