Search for π0→νμνˉμ\pi^0 \to \nu_{\mu}\bar\nu_{\mu} Decay in LSND

We observe a net beam-excess of $8.7 \pm 6.3$ (stat) $\pm 2.4$ (syst) events, above 160 MeV, resulting from the charged-current reaction of $\nu_{\mu}$ and/or $\bar\nu_{\mu}$ on C and H in the LSND detector. No beam related muon background is expected in this energy regime. Within an analysis framework of $\pi^0 \to \nu_{\mu}\bar\nu_{\mu}$, we set a direct upper limit for this branching ratio of $\Gamma(\pi^0 \to \nu_\mu \bar\nu_\mu) / \Gamma(\pi^0 \to all) < 1.6 \times 10^{-6}$ at 90% confidence level.Comment: 4 pages, 4 figure

Pion-nucleus elastic scattering on 12C, 40Ca, 90Zr, and 208Pb at 400 and 500 MeV

Pion-nucleus elastic scattering at energies above the Delta(1232) resonance is studied using both pi+ and pi- beams on 12C, 40Ca, 90Zr, and 208Pb. The present data provide an opportunity to study the interaction of pions with nuclei at energies where second-order corrections to impulse approximation calculations should be small. The results are compared with other data sets at similar energies, and with four different first-order impulse approximation calculations. Significant disagreement exists between the calculations and the data from this experiment

Mesonic cloud contribution to the nucleon and delta masses

Pion-nucleon elastic scattering in the dominant $P_{33}$ channel is examined in the model in which the interaction is of the form $\pi + N\leftrightarrow N, \Delta(1232)$. New expressions are found for the elastic pion-nucleon scattering amplitude which differ from existing formula both in the kinematics and in the treatment of the renormalization of the nucleon mass and coupling constant. Fitting the model to the phase shifts in the $P_{33}$ channel does not uniquely fix the parameters of the model. The cutoff for the pion-nucleon form factor is found to lie in the range $\beta = 750\pm350$ MeV/c. The masses of the nucleon and the $\Delta$ which would arise if there were no coupling to mesons are found to be $m_{_N}^{(0)}= 1200\pm 200$ MeV and $m_\Delta^{(0)} = 1500\pm 200$ MeV. The difference in these bare masses, a quantity which would be accounted for by a residual gluon interaction, is found to be $\delta m^{(0)}=350\pm 100$ MeV.Comment: 26 pages, 9 figures, significant rewrit

A Behaviour Awareness Mechanism to Support Collaborative Learning

Awareness has been identified as a key element that affects the quality of collaboration. Several studies indicate that awareness mechanisms to support collaborative learning activities should include factors and stimuli from the students’ context and social interactions. This contributes to enhance the collaboration process and the learning experience of the students. This paper proposes a behaviour awareness mechanism to support collaborative learning in undergraduate learning scenarios. This mechanism has been designed to provide personal and social awareness to students about both, their own and their peers learning behaviour. Moreover, this mechanism encourages reflection and promotes social interactions among students in order to improve the effectiveness of collaborative learning. The article also describes and evaluates a prototype of the proposed mechanism and its implementation in a collaborative mobile learning application, using a case study. The preliminary results show that this proposal helps promote collaborative learning in undergraduate learning contexts.Peer ReviewedPostprint (published version