Using single top rapidity to measure V_td, V_ts, V_tb at hadron colliders

Single top production processes are usually regarded as the ones in which V_tb can be directly measured at hadron colliders. We show that the analysis of the single top rapidity distribution in t-channel and tW production can also set direct limits on V_td. At LHC with 10 fb^-1 at 14 TeV the combined limits on V_td may be reduced by almost a factor of two when the top rapidity distribution is used. This also implies that the limits on V_tb can also be reduced by 15%, since both parameters as well as V_ts must be simultaneously obtained from a global fit to data. At Tevatron the explotation of this distribution would require very high statistics.Comment: LaTeX 19 pages, 48 PS figures. A section added with estimations of systematics, LO/NLO comparison and a fast detector simulation. Final version to appear in PR

Constraints on the Wtb vertex from early LHC data

We use the recent measurements of top quark decay asymmetries in ATLAS and the t-channel single top cross section in CMS to set the first combined LHC limits on the Wtb vertex. This combination allows to obtain much better limits than the separate measurements. The resulting constraints are comparable, although still weaker, than the ones obtained using Tevatron data with much more statistics.Comment: RevTeX 4 page

Pairwise thermal entanglement in Ising-XYZ diamond chain structure in an external magnetic field

Quantum entanglement is one of the most fascinating types of correlation that can be shared only among quantum systems. The Heisenberg chain is one of the simplest quantum chains which exhibits a reach entanglement feature, due to the Heisenberg interaction is quantum coupling in the spin system. The two particles were coupled trough XYZ coupling or simply called as two-qubit XYZ spin, which are the responsible for the emergence of thermal entanglement. These two-qubit operators are bonded to two nodal Ising spins, and this process is repeated infinitely resulting in a diamond chain structure. We will discuss two-qubit thermal entanglement effect on Ising-XYZ diamond chain structure. The concurrence could be obtained straightforwardly in terms of two-qubit density operator elements, using this result, we study the thermal entanglement, as well as the threshold temperature where entangled state vanishes. The present model displays a quite unusual concurrence behavior, such as, the boundary of two entangled regions becomes a disentangled region, this is intrinsically related to the XY-anisotropy in the Heisenberg coupling. Despite a similar property had been found for only two-qubit, here we show in the case of a diamond chain structure, which reasonably represents real materials.Comment: 6 pages, 7 figure

Two dimensional XXZ-Ising model on square-hexagon lattice

We study a two dimensional XXZ-Ising on square-hexagon (4-6) lattice with spin-1/2. The phase diagram of the ground state energy is discussed, shown two different ferrimagnetic states and two type of antiferromagnetic states, beside of a ferromagnetic state. To solve this model, it could be mapped into the eight-vertex model with union jack interaction term. Imposing exact solution condition we find the region where the XXZ-Ising model on 4-6 lattice have exact solutions with one free parameter, for symmetric eight-vertex model condition. In this sense we explore the properties of the system and analyze the competition of the interaction parameters providing the region where it has an exact solution. However the present model does not satisfy the \textit{free fermion} condition, unless for a trivial situation. Even so we are able to discuss their critical points region, when the exactly solvable condition is ignored.Comment: 5 pages, 5 figure

A Frustrated 3-Dimensional Antiferromagnet: Stacked J1−J2J_{1}-J_{2} Layers

We study a frustrated 3D antiferromagnet of stacked $J_1 - J_2$ layers. The intermediate 'quantum spin liquid' phase, present in the 2D case, narrows with increasing interlayer coupling and vanishes at a triple point. Beyond this there is a direct first-order transition from N{\' e}el to columnar order. Possible applications to real materials are discussed.Comment: 11 pages,7 figure

Blind ocean acoustic tomography: experimental results on the INTIFANTE'00 data set

Blind Ocean Acoustic Tomography (BOAT) is an ocean remote exploration concept similar to acoustic tomography but where both the emitted signal waveform and the source osition are unknown. BOAT consists of a minimal environmental model of the area, a broadband matched- eld processor and a genetic algorithm search procedure. This paper presents the results obtained with BOAT on part of the data set acquired during the INTIFANTE'00 sea trial, where an acoustic source was towed along both range independent and range dependent paths, with source-receiver ranges varying from 500 m up to 5.5 km and water depths varying from 70 to 120 m. The results obtained on several hours of data, show that source range and depth can be used as focalizing parameters, together with the Bartlett power to indicate model tness. Using this three parameters it becomes clear when the environment is \in focus" and when it is \out of focus" leading to realiable estimates of the geometric and environmental parameters under estimation.This work was supported by programe PRAXIS XXI of FCT, Portugal, under projects INTIMATE and ATOMS and under project TOMPACO, CNR, Italy. The authors are also in debt of SACLANTCEN for equipment loan and to the crew of NRP D.Carlos I of IH, that made the sea trial successful