Neutrino Interactions at Low and Medium Energies

We discuss the calculations for several neutrino induced reactions from low energies to the GeV region. Special attention is paid to nuclear corrections when the targets are medium or heavy nuclei. Finally, we present several ratios of neutral to charged current reactions whose values on isoscalar targets can be estimated accurately. The ratios are useful for investigating neutrino oscillations in Long Baseline experiments.Comment: Contributed to 1st Workshop on Neutrino - Nucleus Interactions in the Few GeV Region (NuInt01), Tsukuba, Japan, 13-16 Dec 2001. 9 pages, 15 figure

Muon Spectra of Quasi-Elastic and 1-Pion Production Events in LBL Neutrino Oscillation Experiments

The muon energy spectra of the quasi-elastic and 1-pion production events in a LBL experiment, like K2K, are predicted to follow closely the neutrino energy spectrum, with downward shifts of the energy scale by $/2 M$ and $( + M_\Delta^2 - M^2)/2 M$ respectively. These predictions seem to agree with the observed muon spectra in the K2K nearby detector. The corresponding muon spectra in the far-away (SK) detector are predicted to show characteristic spectral distortions induced by $\nu_\mu$ oscillation. Comparison of the predicted spectral distortions with the observed muon spectra of the 1-Ring and 2-Ring muon events in the SK detector will help to determine the oscillation parameters. The results will be applicable to other LBL experiments as well.Comment: 13 pages. One figure and a few comments added, final version to appear in P

Neutrino Masses and Interactions in a Model with Nambu-Goldstone Bosons

A natural scenario for the generation of neutrino masses is the see-saw mechanism, in which a large right-handed neutrino mass makes the left-handed neutrinos light. We review a special case when the Majorana masses originate from spontaneous breaking of a global U(1)XU(1) symmetry. The interactions of the right-handed with the left-handed neutrinos at the electorweak scale further break the global symmetry giving mass to one pseudo Nambu-Goldstone boson (pNGB). The pNGB can then generate a long-range force. Leptogenesis occurs through decays of heavy neutrinos into the light ones and Higgs particles. The pNGB can become the acceleron field and the neutrino masses vary with the value of the scalar field. The talk is a brief preview of the results in reference [11].Comment: Invited talk presented at the Second International Conference on High Energy Physics (CICHEP II), January 14-17, 2006, Cairo, Egyp

Throughput Optimal Routing in Overlay Networks

Maximum throughput requires path diversity enabled by bifurcating traffic at different network nodes. In this work, we consider a network where traffic bifurcation is allowed only at a subset of nodes called \emph{routers}, while the rest nodes (called \emph{forwarders}) cannot bifurcate traffic and hence only forward packets on specified paths. This implements an overlay network of routers where each overlay link corresponds to a path in the physical network. We study dynamic routing implemented at the overlay. We develop a queue-based policy, which is shown to be maximally stable (throughput optimal) for a restricted class of network scenarios where overlay links do not correspond to overlapping physical paths. Simulation results show that our policy yields better delay over dynamic policies that allow bifurcation at all nodes, such as the backpressure policy. Additionally, we provide a heuristic extension of our proposed overlay routing scheme for the unrestricted class of networks

Fast reoptimization for the minimum spanning tree problem

AbstractWe study reoptimization versions of the minimum spanning tree problem. The reoptimization setting can generally be formulated as follows: given an instance of the problem for which we already know some optimal solution, and given some “small” perturbations on this instance, is it possible to compute a new (optimal or at least near-optimal) solution for the modified instance without ex nihilo computation? We focus on two kinds of modifications: node-insertions and node-deletions. When k new nodes are inserted together with their incident edges, we mainly propose a fast strategy with complexity O(kn) which provides a max{2,3−(2/(k−1))}-approximation ratio, in complete metric graphs and another one that is optimal with complexity O(nlogn). On the other hand, when k nodes are deleted, we devise a strategy which in O(n) achieves approximation ratio bounded above by 2⌈|Lmax|/2⌉ in complete metric graphs, where Lmax is the longest deleted path and |Lmax| is the number of its edges. For any of the approximation strategies, we also provide lower bounds on their approximation ratios