58 research outputs found
Cross Sections of the Deuteron-Proton Breakup at 130 MeV:A Probe of Three-Nucleon System Dynamics
Three-nucleon system dynamics can be investigated quantitatively by comparing observables calculated with the use of Faddeev equations with results of precise measurements. Proper description of the experimental data can be achieved only if the dynamical models include, in addition to the nucleon-nucleon interaction, subtle effects of suppressed degrees of freedom, effectively introduced by means of genuine three-nucleon forces. A large set of high precision, exclusive cross-section data for the (1)H(d,pp)n breakup reaction at 130 MeV contributes significantly to constrain the physical assumptions underlying the theoretical interaction models. Comparison of nearly 1,800 cross section data points with the predictions using nuclear interactions generated in various ways, allowed to establish importance of including both, the three-nucleon and the Coulomb forces to significantly improve the description of the whole data set
Search for eta-mesic 4He in the dd->3He n pi0 and dd->3He p pi- reactions with the WASA-at-COSY facility
The search for 4He-eta bound states was performed with the WASA-at-COSY
facility via the measurement of the excitation function for the dd->3He n pi0
and dd->3He p pi- processes. The beam momentum was varied continuously between
2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the dd->4He
eta reaction ranging from Q=-70 MeV to Q=30 MeV. The luminosity was determined
based on the dd->3He n reaction and quasi-free proton-proton scattering via
dd->pp n_spectator n_spectator reactions. The excitation functions determined
independently for the measured reactions do not reveal a structure which could
be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the
total cross sections for the bound state production and decay in
dd->(4He-eta)_bound->3He n pi0 and dd->(4He-eta)_bound->3He p pi- processes
were determined taking into account the isospin relation between both the
channels considered. The results of the analysis depend on the assumptions of
the N* momentum distribution in the anticipated mesic-4He. Assuming as in the
previous works, that this is identical with the distribution of nucleons bound
with 20 MeV in 4He, we determined that (for the mesic bound state width in the
range from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about
3 nb and about 6 nb for npi0 and ppi- channels, respectively. However, based on
the recent theoretical findings of the N*(1535) momentum distribution in the
N*-3He nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector
acceptance decreases and hence the corresponding upper limits are 5 nb and 10
nb for npi0 and ppi- channels respectively.Comment: This article will be submitted to JHE
Cross section ratio and angular distributions of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8 MeV excess energy
We present new data for angular distributions and on the cross section ratio
of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q =
59.8 MeV. The data have been obtained at the WASA-at-COSY experiment
(Forschungszentrum J\"ulich) using a proton beam and a deuterium pellet target.
While the shape of obtained angular distributions show only a slow variation
with the energy, the new results indicate a distinct and unexpected total cross
section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the
variation of the production mechanism within this energy interval.Comment: 9 pages, 9 figure
Investigation of the Three-Nucleon System Dynamics in the Deuteron-Proton Breakup Reaction
Precise and large sets of cross section, vector A x , A y and tensor A xx , A xy , A yy analyzing power data for the 1 H(d, pp)n breakup reactions were measured at 100 and 130 MeV deuteron beam energies with the SALAD and BINA detectors at KVI and the Germanium Wall setup at FZ-Jülich. Results are compared with various theoretical approaches which model the three-nucleon system dynamics. The cross section data reveal a sizable three-nucleon force (3NF) and Coulomb force influence. In case of the analyzing powers very low sensitivity to these effects was found and the data are well describe by 2N models only. For A xy at 130 MeV, serious disagreements were observed when 3NF models are included in the calculations
Gregor Lang-Wojtasik (2008): Schule in der Weltgesellschaft – Herausforderungen und Perspektiven einer Schultheorie jenseits der Moderne. Weinheim, München: Juventa 2008, 240 S. [Rezension]
Rezension zu: Gregor Lang-Wojtasik (2008): Schule in der Weltgesellschaft – Herausforderungen und Perspektiven einer Schultheorie jenseits der Moderne. Weinheim, München: Juventa 2008, 240 S., ISBN 978-3-7799-1267-
Measurement of deuteron carbon vector analyzing powers in the kinetic energy range 170-380 MeV
A measurement of vector analyzing powers in elastic deuteron-carbon
scattering has been performed at the Cooler Synchrotron COSY of
Forschungszentrum J\"ulich, Germany. Seven kinetic beam energies between 170
and 380 MeV have been used. A vector-polarized beam from a polarized deuteron
source was injected, accelerated to the final desired energy and stored in
COSY. A thin needle-shaped diamond strip was used as a carbon target, onto
which the beam was slowly steered. Elastically scattered deuterons were
identified in the forward direction using various layers of scintillators and
straw tubes. Where data exist in the literature (at 200 and 270 MeV), excellent
agreement of the angular shape was found. The beam polarization of the
presented data was deduced by fitting the absolute scale of the analyzing power
to these references. Our results extend the world data set and are necessary
for polarimetry of future electric dipole moment searches at storage rings.
They will as well serve as an input for theoretical description of polarized
hadron-hadron scattering
Measurement of global polarization of {\Lambda} hyperons in few-GeV heavy-ion collisions
The global polarization of {\Lambda} hyperons along the total orbital angular
momentum of a relativistic heavy-ion collision is presented based on the high
statistics data samples collected in Au+Au collisions at \sqrt{s_{NN}} = 2.4
GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer
(HADES) at GSI, Darmstadt. This is the first measurement below the strangeness
production threshold in nucleon-nucleon collisions. Results are reported as a
function of the collision centrality as well as a function of the hyperon
transverse momentum (p_T) and rapidity (y_{CM}) for the range of centrality
0--40%. We observe a strong centrality dependence of the polarization with an
increasing signal towards peripheral collisions. For mid-central (20--40%)
collisions the polarization magnitudes are (%) = 6.0 \pm 1.3
(stat.) \pm 2.0 (syst.) for Au+Au and (%) = 4.6 \pm 0.4 (stat.)
\pm 0.5 (syst.) for Ag+Ag, which are the largest values observed so far. This
observation thus provides a continuation of the increasing trend previously
observed by STAR and contrasts expectations from recent theoretical
calculations predicting a maximum in the region of collision energies about 3
GeV. The observed polarization is of a similar magnitude as predicted by 3D
fluid dynamics and the UrQMD plus thermal vorticity model and significantly
above results from the AMPT model.Comment: 8 pages, 4 figure
Pinus sylvestris L. jako biomonitor zanieczyszczenia srodowiska metalami ciezkimi [Zn, Cd, Pb]
Oceniono wpływ emisji przemysłowych na wybrane parametry (wielkość pierśnicy oraz przyrostów rocznych) drzew rosnących w pobliżu emitorów. Powierzchnie badawcze rozmieszczono w różnych odległościach od źródeł zanieczyszczeń, jakimi są huta cynku i ołowiu w Miasteczku Śląskim oraz huta stali w Dąbrowie Górniczej (dawna Huta Katowice). Wielkość przyrostów rocznych P. sylvestris oraz zawartość metali ciężkich (Zn, Cd., Pb) w drewnie mierzono w przedziałach pięcioletnich.
Szerokość przyrostów rocznych drzew jest determinowana przez różne czynniki ekologiczne (m.in. klimatyczne, siedliskowe), ale również przez zanieczyszczenie atmosfery. Zaobserwowano zmniejszony przyrost roczny drzew rosnących na badanych terenach jak również zwiększoną zawartość metali ciężkich w drewnie w pierwszych latach po rozpoczęciu działalności zakładów przemysłowych.The impact of industrial emissions on selected parameters of wood from Scots pine was assessed. Samples of wood from Scots pine which ran along a gradient of industrial pollution were investigated in the South of Poland. These sites located are at various distances from a zinc and lead smelter (Miasteczko Śląskie) and steelworks (Dąbrowa Górnicza).
Samples were taken from two polluted zones and from a control zone. The relative size of the increment and heavy metal content were measured in a wood sample from Scots pine over 5-year periods covering a 25-year period of activity of industrial plants mentioned according to the method presented by Nabais et al. [1999], The analyses of heavy metal content in wood were made using the conventional AAS method [Ostrowska et al. 1991].
Annual ring widths of forest trees are affected by different ecological factors (climate, soil,) and also air pollution. In the investigated tree areas with an intensive air pollution the annual ring width reductions are observed.
The heavy metal concentration was increased in the first years of the activity of industrial plants. However some studies present a positive correlation between radial distributions of heavy metals in tree rings and temporal records of pollution from industry and others fail in using dendroanalysis as a chronological record of pollution [Hagemeyer, Schäfer 1995].
It should be noted that the conclusions presented here are based on a relatively small amount of data. Thus the interpretation of obtained results needs to be confirmed by further investigations
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