3,771 research outputs found
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
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
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
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
Life history and control of the juniper tip midge, Oligotrophus apicis Appleby and Neiswander
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
The 2mrad horizontal crossing angle IR layout for a TeV ILC
The current status of the 2mrad crossing angle layout for the ILC is
reviewed. The scheme developed in the UK and France is described and the
performance discussed for a TeV machine. Secondly, the scheme developed at SLAC
and BNL is then studied and modified for a TeV machine. We find that both
schemes can handle the higher energy beam with modifications, and share many
common features.Comment: The proceedings of the 2005 International Linear Collider Workshop,
March 2005. 4 pages, 5 figure
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