The Lambda polarization, the analyzing power, and the Lambda spin transfer coefficient of the reaction pp -> p K+ Lambda were measured at beam momenta of 2.70 GeV/c and 2.95 GeV/c, corresponding to ...excess energies of 122 MeV and 204 MeV. While the analyzing power and the spin transfer coefficient do not change significantly with the excess energy, the Lambda polarization varies strongly and changes its sign. As this is the first measurement of polarization observables below an excess energy of 200 MeV, the change of the sign of the Lambda polarization was not observed before. The high statistics of the data (~200 k events for each momentum) enables detailed studies of the dependence of the Lambda polarization and the analyzing power on the center of mass momentum of the particles. The results of the spin transfer coefficient are in qualitative agreement with the DISTO experiment. The Lambda polarization data of 2.95 GeV/c are only conform with the DISTO experiment, while both the 2.70 GeV/c and 2.95 GeV/c data differ strongly from all previous measurements, whether exclusive or inclusive.
The three precision measurements of the cross section
$\sigma\big(e^+e^-\rightarrow\pi^+\pi^-\gamma(\gamma)\big)$ using initial state
radiation by the KLOE collaboration provide an important input ...for the
prediction of the hadronic contribution to the anomalous magnetic moment of the
muon. These measurements are correlated for both statistical and systematic
uncertainties and, therefore, the simultaneous use of these measurements
requires covariance matrices that fully describe the correlations. We present
the construction of these covariance matrices and use them to determine a
combined KLOE measurement for
$\sigma\big(e^+e^-\rightarrow\pi^+\pi^-\gamma(\gamma)\big)$. We find, from this
combination, a two-pion contribution to the muon magnetic anomaly in the energy
range $0.10 < s < 0.95$ GeV$^2$ of $a_{\mu}^{\pi^+\pi^-} = (489.8 \pm 1.7_{\rm
stat} \pm 4.8_{\rm sys} ) \times 10^{-10}$.
This research was conducted to define viewing distance characteristics of individuals engaged in ordinary reading tasks. Specific attention was directed to assessing the potential relationship ...between observed distance and individual resting point accommodation. Consistent, statistically significant differences were observed across variable handheld and structurally-fixed hardcopy display configuration conditions. Relationships between observed viewing distance and resting point accommodation were not apparent. These findings suggest that simple eye-to-display viewing distance is fundamentally different for handheld text presentations and for the same text presented in a configuration similar to that of a video display terminal.
We conduct a search for the 4He-eta bound state with the WASA-at-COSY facility via the measurement of the excitation function for the reaction dd->3Heppi-. In first experiment performed in June 2008, ...we used COSY deuteron beam with a slowly ramped beam momentum corresponding to a variation of the excess energy for the 4He-eta system from -51.4 MeV to 22 MeV. Here we report on the status of the measurement and the data evaluation.
New data on the production of single neutral pions in the
$pd\rightarrow{}^3\textrm{He}\,\pi^0$ reaction are presented. For fifteen
proton beam momenta between $p_p=1.60\;\textrm{GeV}/c$ and
...$p_p=1.74\;\textrm{GeV}/c$, differential cross sections are determined over a
large fraction of the backward hemisphere. Since the only previous systematic
measurements of single-pion production at these energies were made in collinear
kinematics, the present work constitutes a significant extension of the current
knowledge on this reaction. Even this far above the production threshold,
significant changes are found in the behaviour of the angular distributions
over small intervals in beam momentum.
The measurement of the quasi-free production of the eta prime meson has been carried out at the COSY-11 detection setup using a proton beam and a deuteron cluster target. The energy dependence of the ...cross section is extracted using a fixed proton beam momentum of p_beam=3.35 GeV/c and exploiting the Fermi momenta of nucleons inside deuterons. The data cover a range of centre-of-mass excess energies from 0 to 24 MeV. Due to the low statistics at the present stage only upper limits for the cross sections could be extracted. In this article we focus on the functioning and efficiency determination of the neutron detector.
Positron Annihilation Lifetime Spectroscopy (PALS) has shown to be a powerful tool to study the nanostructures of porous materials. Positron Emissions Tomography (PET) are devices allowing imaging of ...metabolic processes e.g. in human bodies. A newly developed device, the J-PET (Jagiellonian PET), will allow PALS in addition to imaging, thus combining both analyses providing new methods for physics and medicine. In this contribution we present a computer program that is compatible with the J-PET software. We compare its performance with the standard program LT 9.0 by using PALS data from hexane measurements at different temperatures. Our program is based on an iterative procedure, and our fits prove that it performs as good as LT 9.0.
We describe a novel technique for comparing total cross sections for the reactions
pp→
ppπ
0,
pp→
ppη, and
pp→
ppη′ close to threshold. The initial and final state proton-proton interactions are ...factored out of the total cross section, and the dependence of this reduced cross section on the volume of phase space is discussed. Different models of the proton-proton interaction are compared. We argue that the scattering length of the S-wave
η′-proton interaction is of the order of 0.1 fm.
Phys. Rev. Lett. 121, 052001 (2018) Exclusive measurements of the quasi-free $pp \to pp\pi^+\pi^-$ reaction have
been carried out at WASA@COSY by means of $pd$ collisions at $T_p$ = 1.2 GeV.
Total ...and differential cross sections have been extracted covering the energy
region $T_p = 1.08 - 1.36$ GeV, which is the region of $N^*(1440)$ and
$\Delta(1232)\Delta(1232)$ resonance excitations. Calculations describing these
excitations by $t$-channel meson exchange are at variance with the measured
differential cross sections and underpredict substantially the experimental
total cross section. An isotensor $\Delta N$ dibaryon resonance with $I(J^P) =
2(1^+)$ produced associatedly with a pion is able to overcome these
deficiencies.
Phys. Rev. C 99, 025201 (2019) Exclusive measurements of the quasi-free $pp \to pp\pi^+\pi^-$ reaction have
been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA
detector setup ...at COSY. Total and differential cross sections have been
obtained covering the energy region $T_p = 1.08 - 1.36$ GeV ($\sqrt s$ = 2.35 -
2.46 GeV), which includes the regions of $N^*(1440)$ and
$\Delta(1232)\Delta(1232)$ resonance excitations. Calculations describing these
excitations by $t$-channel meson exchange are at variance with experimental
differential cross sections and underpredict substantially the measured total
cross section. An isotensor $\Delta N$ dibaryon resonance with $I(J^P) =
2(1^+)$ produced associatedly with a pion is able to overcome these
deficiencies. Such a dibaryon was predicted by Dyson and Xuong and more
recently calculated by Gal and Garcilazo.
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