Beam-beam-induced orbit effects at LHC

For high bunch intensities the long-range beam-beam interactions are strong enough to provoke effects on the orbit. As a consequence the closed orbit changes. The closed orbit of an unperturbed machine with respect to a machine where the beam-beam force becomes more and more important has been studied and the results are presented in this paper.Comment: 5 pages, contribution to the ICFA Mini-Workshop on Beam-Beam Effects in Hadron Colliders, CERN, Geneva, Switzerland, 18-22 Mar 201

A theory driven analysis of the effective QED coupling at MZM_Z

An evaluation of the effective QED coupling at the scale M_Z is presented. It employs the predictions of perturbative QCD for the cross section of electron positron annihilation into hadrons up to order \alpha_s^2, including the full quark mass dependence, and of order \alpha_s^3 in the high energy region. This allows to predict the input for the dispersion relations over a large part of the integration region. The perturbative piece is combined with data for the lower energies and the heavy quark thresholds. The result for the hadronic contribution to the running of the coupling \Delta\alpha^{(5)}_{\rm had}(M_Z^2)= (277.5 \pm 1.7)\times 10^{-4} leads to (\alpha(M_Z^2))^{-1}=128.927 \pm 0.023. Compared to previous analyses the uncertainty is thus significantly reduced.Comment: 9 pages (Latex); minor error in result for charm threshold region fixed; final result unchange

Luminosity Optimization and Calibration in the LHC

The ability of a particle collider to produce the required number of events, the luminosity, is usually used to size its performances. As demonstrated in many accelerators optimizing and calibrating the luminosity can be done using the Van Der Meer method which consist of shifting one beam with respect to the other while recording the event rate. In the LHC it is planned to perform those scans at the four interaction points using the data from the machine detectors as well as the ones from the experiments. A graphical user interface (GUI) has been developed for this purpose. We looked into procedures to quantify and if possible minimize the systematic errors coming from the measurements and the beam parameters and will discuss how we plan on using the relevant informations such as the vertex position or background measurements coming from the experiments

Kinetic Regimes and Cross-Over Times in Many-Particle Reacting Systems

We study kinetics of single species reactions ("A+A -> 0") for general local reactivity Q and dynamical exponent z (rms displacement x_t ~ t^{1/z}.) For small molecules z=2, whilst z=4,8 for certain polymer systems. For dimensions d above the critical value d_c=z, kinetics are always mean field (MF). Below d_c, the density n_t initially follows MF decay, n_0 - n_t ~ n_0^2 Q t. A 2-body diffusion-controlled regime follows for strongly reactive systems (Q>Qstar ~ n_0^{(z-d)/d}) with n_0 - n_t ~ n_0^2 x_t^d. For Q<Qstar, MF kinetics persist, with n_t ~ 1/Qt. In all cases n_t ~ 1/x_t^d at the longest times. Our analysis avoids decoupling approximations by instead postulating weak physically motivated bounds on correlation functions.Comment: 10 pages, 1 figure, uses bulk2.sty, minor changes, submitted to Europhysics Letter

Hadron Production via e+e- Collisions with Initial State Radiation

A novel method of studying e+e- annihilation into hadrons using initial state radiation at e+e- colliders is described. After brief history of the method, its theoretical foundations are considered. Numerous experiments in which exclusive cross sections of e+e- annihilation into hadrons below the center-of-mass energy of 5 GeV have been measured are presented. Some applications of the results obtained to fundamental tests of the Standard Model are listed.Comment: 50 pages, 88 figures, accepted for publication in Rev. Mod. Phy