19615803
Probing the eV-Mass range for solar axions with CAST
The CERN Axion Solar Telescope (CAST) is searching for solar axions which could be produced in the core of the Sun via the so-called Primakoff effect. Not only would these hypothetical particles solve the strong CP problem, but they are also one of the favored candidates for dark matter. In order to look for axions originating from the Sun, CAST uses a decommissioned LHC prototype magnet. In its 10 m long magnetic field region of 9 Tesla, axions could be reconverted into X-ray photons. Different X-ray detectors are installed on both ends of the magnet, which is mounted on a structure built to follow the Sun during sunrise and sunset for a total of about 3 hours per day. The analysis of the data acquired during the first phase of the experiment with vacuum in the magnetic field region yielded the most restrictive experimental upper limit on the axion-to-photon coupling constant for axion masses up to about 0.02 eV. In order to extend the sensitivity of the experiment to a wider mass range, the CAST experiment continues its search for axions with helium in the magnet bores. In this way it is possible to restore coherence of conversion for larger masses. Changing the pressure of the helium gas enables the experiment to scan different axion masses in the range of up to about 1.2 eV. Especially at high pressures, a precise knowledge of the gas density distribution is crucial to obtain accurate results. In the first part of this second phase of CAST, 4He was used and the axion mass region was extended up to 0.39 eV, a part of phase space favored by axion models. In CAST's ongoing 3He phase the studied mass range is now being extended further. In this contribution the final results of CAST's 4He phase will be presented and the current status of the 3He run will be given. This includes latest results as well as prospects of future axion experiments.
120352716
Status and perspectives of the CAST experiment
The CERN Axion Solar Telescope (CAST) is currently the most sensitive axion helioscope designed to search for axions produced by the Primakoff process in the solar core. CAST is using a Large Hadron Collider (LHC) test magnet where axions could be converted into X-rays with energies up to 10 keV. During the phase I, the experiment operated with vacuum inside the magnet bores and covered axion masses up to 0.02 eV. In the phase II, the magnet bores were filled with a buffer gas (first 4He and later 3He) at various densities in order to extend the sensitivity to higher axion masses (up to f .18 eV). The phase II data taking was completed in 2011. So far, no evidence of axion signal has been found and CAST set the most restrictive experimental limit on the axion-photon coupling constant over a broad range of axion masses. The latest CAST results with 3He data in the mass range 0.39 eV < ma < 0.64 eV will be presented.
119257623
An updated analysis on the rise of the hadronic total cross-section at the LHC energy region
pp elastic scattering above 5 GeV is presented. The dataset includes the recent high-precision TOTEM measurements of the pp total and elastic (integrated) cross-sections at 7 TeV and 8 TeV. Following previous works, the leading high-energy contribution for the total cross-section (�tot) is parametrized as ln(s/sh), where and sh are free real fit parameters. Singly-subtracted derivative dispersion relations are used to connecttot and the rho parameter (�) in an analytical way. Different fit procedures are considered, including individual fits totot data, global fits totot anddata, constrained and unconstrained data reductions. The results favor a rise of thetot faster than the log-squared bound by Froissart and Martin at the LHC energy region. The parametrization fortot is extended to fit the elastic cross-section (�el) data with satisfactory results. The analysis indicates an asymptotic ratioel/�tot consistent with 1/3 (as already obtained in a previous work). A critical discussion on the correlation, practical role and physical implications of the parameters and sh is presented. The discussion confronts the 2002 prediction oftot by the COMPETE Collaboration and the recent result by the Particle Data Group (2012 edition of the Review of Particle Physics). Some conjectures on possible implications of a fast rise of the proton-proton total cross-section at the highest energies are also presented.
118857116
Recent results on Top quark Physics with the ATLAS and CMS experiments
An overview of the most recent results on top quark physics obtained using proton-proton collision data collected with the ATLAS and the CMS experiments at 7 TeV center-of-mass energy is given. Measurements for inclusive and differential top quark pair or single top quark production in different final states are reviewed. Top properties such as W helicity in top decays, electric charge, charge asymmetry and spin correlations of top quark pairs, among others have also been measured by the LHC experiments. All the measurements are found to be consistent with the Standard Model predictions with a good level of accuracy. The latest results in the measurement of the top quark mass at the LHC are also presented and discussed.
7497403
Tuning HMC using Poisson Brackets
We discuss how the integrators used for the Hybrid Monte Carlo (HMC) algorithm not only approximately conserve some Hamiltonian H but exactly conserve a nearby shadow Hamiltonian H, and how the difference ∆H ≡ H −H may be expressed as an expansion in Poisson brackets. By measuring average values of these Poisson brackets over the equilibrium distribution ∝ e−H generated by HMC we can find the optimal integrator parameters from a single simulation. We show that a good way of doing this in practice is to minimize the variance of ∆H rather than its magnitude, as has been previously suggested. Some details of how to compute Poisson brackets for gauge and fermion fields, and for nested and force gradient integrators are also presented.
119020741
Studying the infrared behaviour of gluon and ghost propagators using large asymmetric lattices
We report on the infrared limit of the quenched lattice Landau gauge gluon propagator computed from large asymmetric lattices. In particular, the compatibility of the pure power law infrared solution (q2)2κ of the Dyson‐Schwinger equations is investigated and the exponent κ is measured. Some results for the ghost propagator and for the running coupling constant will also be shown.
18513841
Fitting BOOMERANG and MAXIMA-1 data with a Einstein–Yang–Mills cosmological model
Abstract We analyse the implications of recent Cosmic Microwave Background (CMB) data for a specific cosmological model, based on the higher-dimensional Einstein–Yang–Mills system compactified on a R × S 3 × S d topology and conclude that the model parameters are tightly constrained by CMB spectra. Moreover, the model predicts a relationship between the deceleration parameter at present, q 0 , and some characteristic features of CMB spectra, namely, the height of the first peak and the the location of the second peak, that is consistent with the observations and which can be further tested by future CMB and other experiments.