Signatures for Black Hole production from hadronic observables at the Large Hadron Collider

The concept of Large Extra Dimensions (LED) provides a way of solving the Hierarchy Problem which concerns the weakness of gravity compared with the strong and electro-weak forces. A consequence of LED is that miniature Black Holes (mini-BHs) may be produced at the Large Hadron Collider in p+p collisions. The present work uses the CHARYBDIS mini-BH generator code to simulate the hadronic signal which might be expected in a mid-rapidity particle tracking detector from the decay of these exotic objects if indeed they are produced. An estimate is also given for Pb+Pb collisions.Comment: 11 pages, 9 figures, ISHIP 2006 conference proceedin

Analysis of HOM interaction between cavities by multi-modal s-parameter measurements

Accelerating cavities exchange HOM power through interconnecting beam pipes in case of signal frequencies above the cut-off of their propagating waveguide modes. This may lead either to improved HOM damping or - in the case most severe - to unwanted phase coherence of fields to the beam. Therefore the knowledge of the scattering properties of a cavity as a line element is needed to analyse all kinds of RF cavity-cavity interaction. Since there is a lack of measurement tools capable to provide a multidimensional scattering matrix at a given frequency point, we have been developing a method for this purpose. It uses a set of 2-port S-parameters of the device under test, embedded in a number of geometrically different RF environments. The application of the method is demonstrated with copper models of TESLA cavities

Information gain versus state disturbance for a single qubit

The trade-off between the information gain and the state disturbance is derived for quantum operations on a single qubit prepared in a uniformly distributed pure state. The derivation is valid for a class of measures quantifying the state disturbance and the information gain which satisfy certain invariance conditions. This class includes in particular the Shannon entropy versus the operation fidelity. The central role in the derivation is played by efficient quantum operations, which leave the system in a pure output state for any measurement outcome. It is pointed out that the optimality of efficient quantum operations among those inducing a given operator-valued measure is related to Davies' characterization of convex invariant functions on hermitian operators.Comment: 17 pages, LaTeX, osid.sty. Substantially expanded and generalize

The influence of wakefields on superconducting TESLA-cavities in FEL-operation

Due to the additional need of very short bunches for the FEL operation with the TESLA-machine strong wakefield effects are expected. One third of the total wakefield energy per bunch is radiated into the frequency region above the energy gap of Cooper pairs in superconducting niobium. The energy of the cooper pairs in superconducting niobium at 2 K corresponds to a frequency of 700 GHz. An analytical and experimental estimation for the overall energy loss of the FEL bunch above energy gap is presented. The analytical method is based on a study from R. B. Palmer [1]. The results of the wakefield estimations are used to calculate possible quality factor reduction of the TESLA cavities during FEL operation. Results are presented

The design of the HOM-damping cells for the S-band linear collider

Damping cells for the higher order modes are necessary for the S-band linear collider to minimize BBU (Beam-Break-Up). The construction of the damper cells has to take into account the different field geometries of the higher order modes. So two different types of dampers have been designed: a wall slotted an an iris slotted cell. In order to optimize the two types of damping cells with respect to damping strength, impedance matching between coupling system and waveguide dampers and between damping cell and undamped cells and the tuning system, damping cells of both types have been built and examinated

The effect of a single HOM-damper cell within a channel of undamped cells

The effect of a single HOM-damper cell within a channel of undamped cells is described theoretically using an equivalent circuit model. From this a simple equation can be derived which relates the Q-value of the single damping-cell, the bandwidth of the passband under consideration, and the additional phase shift which is introduced by the damper cell to provide energy flow into the damper cell. This equation immediately shows the limitations of such single cell damping systems. Comparisons with experimental results are shown