1,744 research outputs found
Pion photoproduction in a dynamical coupled-channel model
Pion photoproduction reactions are investigated in a dynamical
coupled-channel approach based on the Juelich pi-N model, which presently
includes the hadronic pi-N and eta-N stable channels as well as the pi-Delta,
sigma-N and rho-N effective channels. This model has been quite successful in
the description of pi-N to pi-N scattering for center-of-mass energies up to
1.9 GeV. The full pion photoproduction amplitude is constructed to satisfy the
generalized Ward-Takahashi identity and hence, it is fully gauge invariant. The
calculated differential cross sections and photon spin asymmetries up to 1.65
GeV center-of-mass energy for the reactions gamma p to pi+ n, gamma p to pi0 p
and gamma n to pi- p are in good agreement with the experimental data.Comment: Invited talk given at 12th International Conference on Meson-Nucleon
Physics and the Structure of the Nucleon (MENU2010), Williamsburg, USA, May
31-June 4 201
Color Screening and Quark-Quark Interactions in Finite Temperature QCD
We analyze the screening of static diquark sources in 2-flavor QCD and
compare results with the screening of static quark-antiquark pairs. We show
that a two quark system in a fixed color representations is screened at short
distances like a single quark source in the same color representation whereas
at large distances the two quarks are screened independently. At high
temperatures we observe that the relative strength of the interaction in
diquark and quark-antiquark systems, respectively, obeys Casimir scaling. We
use this result to examine the possible existence of heavy quark-quark bound
states in the high temperature phase of QCD. We find support for the existence
of states up to about while states are unlikely to be formed
above .Comment: 8 pages, 6 figure
On the cross section ratio sigma_n/sigma_p in eta photoproduction
The recently discovered enhancement of eta photoproduction on the quasi-free
neutron at energies around sqrt(s)~1.67 GeV is addressed within a SU(3) coupled
channel model. The quasi-free cross sections on proton and neutron, sigma_n and
sigma_p, can be quantitatively explained. In this study, the main source for
the peak in sigma_n/sigma_p is a coupled channel effect in S-wave that explains
the dip-bump structure in gamma n --> eta n. In particular, the photon coupling
to the intermediate meson-baryon states is important. The stability of the
result is extensively tested and consistency with several pion- and
photon-induced reactions is ensured.Comment: Version accepted by Phys. Lett.
Career Choice With the Serious Game Like2be
Choosing a career is an important biographical event for adolescents. Toward the end of compulsory education, they must decide which career path they want to pursue. The serious game like2be was developed to support adolescents in this individual career choice process. In a quasi-experimental intervention study with 809 adolescents, like2be was evaluated for its effectiveness in career choice classes at the lower secondary level. In addition, a teaching concept for the application of the serious game which included additional teaching materials was analyzed. The data show that like2be is an effective medium for broadening personal career choice horizons, especially when it is pedagogically well-founded and integrated into career choice classes. Although the effectiveness of like2be in stimulating intensive reflection on one's own vocational aptitude or a gender-sensitive attitude towards occupations is limited, the present study shows that like2be has major potential for supporting the process of career choice among adolescents
Development of intraindividual value structures in middle childhood: A multicultural and longitudinal investigation
Objective
We examined changes in value interrelations during middle childhood. In line with the Personal Values Theory, we expected a value system, with individuals similarly valuing related motivations, and setting priorities between conflicting motivations. We hypothesized this system to develop dynamically during middle childhood as children deepen their understanding of their own values.
Method
Using unfolding analysis, we estimated intraindividual value structure coherence, that is, the extent to which the interrelations among a child's values are similar to the hypothesized interrelations. Cross-Cultural Study 1 (N = 4615, 6–12-year-old children) included children from 12 countries. Cross-Sequential Study 2 (N = 629, 6–10-year-old children at Time 1) included three annual measurements.
Results
In Study 1, we found a curvilinear association between age and intraindividual value structure coherence: Children's values were more coherent at ages 9–10 than before or after. Study 2 confirmed this pattern of within-individual development.
Conclusions
We propose that development in coherence with the theoretical value structure offers insight into children's understanding of values as well as changes in value priorities
Dynamical coupled-channels model study of pion photoproduction
The photoproduction of pion off nucleon is investigated within a dynamical
coupled-channels approach based on the Juelich pi-N model, which has been quite
successful in the description of pi-N to pi-N scattering for center-of-mass
energies up to 1.9 GeV. The full pion photoproduction amplitude is constructed
to satisfy the generalized Ward-Takahashi identity and hence, it is fully gauge
invariant. The calculated differential cross sections and photon spin
asymmetries up to 1.65 GeV center-of-mass energy for the reactions gamma p to
pi^+ n, gamma p to pi^0 p and gamma n to pi^- p are in good agreement with the
experimental data.Comment: Talk given at The 8th International Workshop on the Physics of
Excited Nucleons (NSTAR2011), May 17-20, 2011, Thomas Jefferson National
Accelerator Facility, Newport News, Virginia, US
Values in the School Curriculum from Teachers' Perspective: A mixed-methods Study
The transmission of human values plays a key role in the educational landscape around the world (Matthes, 2014; Beck, 1990; Halstead, 1996), and educational frameworks (c.f. OECD , 2019; Council of Europe , 2016) as well as national school curricula (c.f. National Curriculum , Ofsted, 2018 ; Lehrplan 21 , D -EDK, 2016) are based on values that are considered important. However, empirical research into how values are structurally reflected in school curricula and how these values are perceived in the school environment by teachers is very limited. This mixed-methods study is the first of its kind to provide findings based on data from Switzerland, where a new comprehensive curriculum has recently been introduced. Schwartz's theory of basic human values (1992), the most widely researched values framework, serves as its conceptual framework. A Qualitative Content Analysis of the Swiss educational curriculum ( Lehrplan 21 , D -EDK, 2016) revealed a wealth of references to values, with a focus on values belonging to Schwartz' higher order values Openness to Change (Basic values: Self-Direction and Stimulation ), Conservation ( Tradition, Conformity and Security ) and Self-Transcendence ( Benevolence and Universalism ). On the other hand, values belonging to the higher order value of Self-Enhancement ( Power and Achievement ) did not play an important role in the investigated curriculum. In a complementary quantitative study, the value statements from the Swiss educational curriculum were embedded in a questionnaire, which 108 (102 female (94.4%), 6 male (5.6%)) primary school teachers completed with regard to how they perceive the value-oriented curricular contents in their school environment. Multidimensional Scaling revealed that teachers' perception of value-oriented curricular contents in their school environment was structured alongside Schwartz's motivational continuum of values, with values of Openness to Change being opposed to values of Conservation , and values of Self-Transcendence being opposed to values of Self-Enhancement
Factors Influencing the Effectiveness of Serious Gaming in the Field of Vocational Orientation
This study investigates the effectiveness of the serious game like2be, which has been developed to support the individual career orientation process of adolescents by broadening their occupational horizon. In this paper, we present results from an intervention study with n = 809 adolescents in Swiss schools at the lower secondary education level. To analyze the extent to which cognitive, affective, and motivational factors are stimulated and what influence they have on expanding knowledge about occupations (measured learning outcome), we applied confirmatory factor analysis, multiple linear regression, and a structural equation model. The results indicate that the stimulation of cognitive processes through serious gaming has a statistically significant impact on learning outcome, although such factors as enjoyment, flow experience, or self-perceived benefits in playing like2be did not significantly impact gain in knowledge about occupations
The QCD equation of state for two flavours at non-zero chemical potential
We present results of a simulation of 2 flavour QCD on a
lattice using p4-improved staggered fermions with bare quark mass .
Derivatives of the thermodynamic grand canonical partition function
with respect to chemical potentials for
different quark flavours are calculated up to sixth order, enabling estimates
of the pressure and the quark number density as well as the chiral condensate
and various susceptibilities as functions of via Taylor series
expansion. Results are compared to high temperature perturbation theory as well
as a hadron resonance gas model. We also analyze baryon as well as isospin
fluctuations and discuss the relation to the chiral critical point in the QCD
phase diagram. We moreover discuss the dependence of the heavy quark free
energy on the chemical potential.Comment: 4 pages, 7 figures, talk presented at Quark Matter 2005, Budapes
Photocouplings at the Pole from Pion Photoproduction
The reactions and are analyzed in a
semi-phenomenological approach up to GeV. Fits to differential cross
section and single and double polarization observables are performed. A good
overall reproduction of the available photoproduction data is achieved. The
J\"ulich2012 dynamical coupled-channel model -which describes elastic
scattering and the world data base of the reactions ,
, and at the same time - is employed as the hadronic
interaction in the final state. The framework guarantees analyticity and, thus,
allows for a reliable extraction of resonance parameters in terms of poles and
residues. In particular, the photocouplings at the pole can be extracted and
are presented.Comment: 37 pages, 31 figures. Angles of the photocouplings at the pole
adapted to the convention of Phys. Rev. C 87, 068201 (2013
- …