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 $bb$ states up to about $2T_c$ while $cc$ states are unlikely to be formed above $T_c$.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 $16^3\times4$ lattice using p4-improved staggered fermions with bare quark mass $m/T=0.4$. Derivatives of the thermodynamic grand canonical partition function $Z(V,T,\mu_u,\mu_d)$ with respect to chemical potentials $\mu_{u,d}$ 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 $\mu_{u,d}$ 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 $\gamma p\to\pi^0 p$ and $\gamma p\to\pi^+ n$ are analyzed in a semi-phenomenological approach up to $E\sim2.3$ 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 $\pi N$ scattering and the world data base of the reactions $\pi N\to\eta N$, $K\Lambda$, and $K\Sigma$ 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