Theory and phenomenology of non-global logarithms

We discuss the theoretical treatment of non-global observables, those quantities that are sensitive only to radiation in a restricted region of phase space, and describe how large `non-global' logarithms arise when we veto the energy flowing into the restricted region. The phenomenological impact of non-global logarithms is then discussed, drawing on examples from event shapes in DIS and energy-flow observables in 2-jet systems. We then describe techniques to reduce the numerical importance of non-global logarithms, looking at clustering algorithms in energy flow observables and the study of associated distribution of multiple observables.Comment: Based on talks presented at the XXXVIIIth Rencontres de Moriond 'QCD and high-energy hadronic interactions', 8 page

The FLUKA Model of IR8

The study of machine induced background (MIB), the radiation environment and beam dynamics of the LHC requires a detailed model of the machine tunnel, elements and electromagnetic fields. In this note, a specially created model of IR8 in FLUKA is described, including the tunnel, vacuum chambers, magnets, collimators, injection elements and shielding. The inclusion of all relevant machine elements in the LSS of IR8 results in a very flexible model suitable for a large variety of calculations and studies. The validation of the model is discussed, and some example applications described

Machine Protection for the Experiments of the LHC

The LHC stored beam contains 362 MJ of energy at the top beam energy of 7 TeV/c, presenting a significant risk to the components of the machine and the detectors. In response to this threat, a sophisticated system of machine protection has been developed to minimize the danger, and detect potentially dangerous situations. In this paper, the protection of the experiments in the LHC from the machine is considered, focusing on pilot beam strikes on the experiments during injection and on the dynamics of hardware failure with a circulating beam, with detailed time-domain calculations performed for LHC ring power converter failures and magnet quenches. The prospects for further integration of the machine protection and experimental protection systems are considered, along with the risk to nearbeam detectors from closed local bumps

Gaps between Jets in the High Energy Limit

We use perturbative QCD to calculate the parton level cross section for the production of two jets that are far apart in rapidity, subject to a limitation on the total transverse momentum Q0 in the interjet region. We specifically address the question of how to combine the approach which sums all leading logarithms in Q/Q0 (where Q is the jet transverse momentum) with the BFKL approach, in which leading logarithms of the scattering energy are summed. This paper constitutes progress towards the simultaneous summation of all important logarithms. Using an "all orders" matching, we are able to obtain results for the cross section which correctly reproduce the two approaches in the appropriate limits.Comment: 29 pages, 9 figures, minor corrections to text and improved figure

Expected Performance of TOTEM BLMS at the LHC

The TOTEM experiment at the LHC will operate down to 10 sigma from the beam in the forward region of the CMS experiment. The associated beam loss monitors (BLMs) are crucial to monitor the position of the detectors and to provide a rapid identification of abnormal beam conditions for machine protection purposes. In this paper, the response of the TOTEM BLMs is considered for nominal machine operation and the protection thresholds are defined, withcalculations made of the expected signal fromprotons grazing the TOTEM pot as a function of pot distance from the beam, and the BLM signal from proton collisions at the CMS beam interaction point

A Quantum-Bayesian Route to Quantum-State Space

In the quantum-Bayesian approach to quantum foundations, a quantum state is viewed as an expression of an agent's personalist Bayesian degrees of belief, or probabilities, concerning the results of measurements. These probabilities obey the usual probability rules as required by Dutch-book coherence, but quantum mechanics imposes additional constraints upon them. In this paper, we explore the question of deriving the structure of quantum-state space from a set of assumptions in the spirit of quantum Bayesianism. The starting point is the representation of quantum states induced by a symmetric informationally complete measurement or SIC. In this representation, the Born rule takes the form of a particularly simple modification of the law of total probability. We show how to derive key features of quantum-state space from (i) the requirement that the Born rule arises as a simple modification of the law of total probability and (ii) a limited number of additional assumptions of a strong Bayesian flavor.Comment: 7 pages, 1 figure, to appear in Foundations of Physics; this is a condensation of the argument in arXiv:0906.2187v1 [quant-ph], with special attention paid to making all assumptions explici

Integration of the Forward Detectors inside the LHC Machine

Several forward detectors have been installed in the LHC long straight sections located on each side of the experimental caverns. Most of these detectors have been designed by the LHC experiments to study the forward physics while some of them are dedicated to the measurement of the LHC luminosity. The integration and the installation of the forward detectors have required an excellent coordination between the experiments and the different CERN groups involved into the design and the installation of the LHC accelerator. In some cases the integration of these detectors has required a modification of the standard beam lines in order to maximise their physics potential. Finally, additional systems have been installed in the LHC tunnel to ensure the operation of the forward detectors in a high radiation environment

ATF2 spot size tuning using the rotation matrix

The Accelerator Test Facility (ATF2) at KEK aims to experimentally verify the local chromaticity correction scheme to achieve a vertical beam size of 37nm. The facility is a scaled down version of the final focus design proposed for the future linear colliders. In order to achieve this goal, high precision tuning methods are being developed. One of the methods proposed for ATF2 is a novel method known as the ‘rotation matrix’ method. Details of the development and testing of this method, including orthogonality optimisation and simulation methods, are presented