Search results for "PERTURBATION"
showing 10 items of 811 documents
Kaon Physics at CERN – Recent Results from the NA48/2 and NA62 Experiments
2012
This letter presents recent results from the kaon experiments NA48/2 and its successor NA62 at CERN. With samples of 2.5 × 106 K µ 3 ± and 4.0 × 106 K e 3 ± events collected by NA48/2 in 2004, precise measurements of the form factors were performed. The Chiral Perturbation Theory was tested through a new study of K ± → π± γγ decays based on data taken with minimal trigger conditions. Using the beam line and detector of NA48/2 in the years 2007-2008, NA62 performed a precison measurement of the helicitysuppressed ratio of the charged kaon leptonic decay rates K ± → e+ ν and K ± → μ + ν Using the full data set, which is about ten times larger than the previous world data sample, the total unc…
Experiments on threshold pion electroproduction
2008
Experimental techniques to access the reactions p(e, e′ p)π0 and d(e, e′ d)π0 at low four momentum transfer and close to threshold are presented. For p(e, e′ p)π0 results at Q 2=0.1 GeV2/c 2 are given and compared to chiral perturbation theory. A new experimental program on d(e, e′ d)π0 is presented.
Thermodynamics of Toda lattice models: application to DNA
1993
Abstract Our generalised Bethe ansatz method is used to formulate the statistical mechanics of the classical Toda lattice in terms of a set of coupled integral equations expressed in terms of appropriate action-angle variables. The phase space as coordinatised by these action-angle variables is constrained; and both the soliton number density and the soliton contribution to the free energy density can be shown to decouple from the phonon degrees of freedom and to depend only on soliton-soliton interactions. This makes it possible to evaluate the temperature dependence of the soliton number density which, to leading order, is found to be proportional to T 1 3 .
Linear and nonlinear optical properties of some organoxenon derivatives
2007
We employ a series of state-of-the-art computational techniques to study the effect of inserting one or more Xe atoms in HC2H and HC4H, on the linear and nonlinear optical (L&NLO) properties of the resulting compounds. It has been found that the inserted Xe has a great effect on the L&NLO properties of the organoxenon derivatives. We analyze the bonding in HXeC2H, and the change of the electronic structure, which is induced by inserting Xe, in order to rationalize the observed extraordinary L&NLO properties. The derivatives, which are of interest in this work, have been synthesized in a Xe matrix. Thus the effect of the local field (LF), due to the Xe environment, on the properties of HXeC2…
Spectral properties of random non-self-adjoint operators
2015
In this thesis we are interested in the spectral properties of random non-self-adjoint operators. Weare going to consider primarily the case of small random perturbations of the following two types of operators: 1. a class of non-self-adjoint h-differential operators Ph, introduced by M. Hager [32], in the semiclassical limit (h→0); 2. large Jordan block matrices as the dimension of the matrix gets large (N→∞). In case 1 we are going to consider the operator Ph subject to small Gaussian random perturbations. We let the perturbation coupling constant δ be e (-1/Ch) ≤ δ ⩽ h(k), for constants C, k > 0 suitably large. Let ∑ be the closure of the range of the principal symbol. Previous results o…
How not to give up on train travel when you are deaf ?
2015
TRANSED 2015 - 14th International Conference on Mobility and Transport for Elderly and Disabled Persons, LISBONNE, PORTUGAL, 28-/07/2015 - 31/07/2015; The SUrDyn project aims at the design of an innovative visual information system, dedicated to travelers who cannot hear or understand audio disrupted announcements (e.g. cancellation, delay...) when they are in train stations. It is based on two previously developed systems: the Jade signer avatar, which informs travelers in French Signs Language, and an animated graphics translation. The objective is to combine these two approaches, in an optimal manner. We proposed a comprehension task to 159 participants divided in three groups: 53 deaf p…
Quel format visuel adopter pour informer les sourds et malentendants dans les transports collectifs ?
2013
Some information is not accessible to the deaf and hard-of-hearing in public transportation because it is diffused in an auditory mode with loud speakers. The present study aims to transcribe graphically five messages of disruption and test their understanding by an audience of people who are deaf or hard-of-hearing. Four graphic formats, more or less involving animation techniques have been developed. Messages have been tested experimentally to determine what format is the most adapted, i.e. the most understandable (understanding task), and to find out the favorite among the four proposed (judgment task). Three groups of subjects were involved in the experimentation: 36 born deaf people, 3…
Sensitivity of EDM experiments in paramagnetic atoms and molecules to hadronic CP violation
2020
Experiments searching for the electric dipole moment (EDM) of the electron $d_e$ utilise atomic/molecular states with one or more uncompensated electron spins, and these paramagnetic systems have recently achieved remarkable sensitivity to $d_e$. If the source of $CP$ violation resides entirely in the hadronic sector, the two-photon exchange processes between electrons and the nucleus induce $CP$-odd semileptonic interactions, parametrised by the Wilson coefficient $C_{SP}$, and provide the dominant source of EDMs in paramagnetic systems instead of $d_e$. We evaluate the $C_{SP}$ coefficients induced by the leading hadronic sources of $CP$ violation, namely nucleon EDMs and $CP$-odd pion-nu…
Measurement of the Charged-Pion Polarizability
2015
The COMPASS collaboration at CERN has investigated pion Compton scattering, $\pi^-\gamma\rightarrow \pi^-\gamma$, at centre-of-mass energy below 3.5 pion masses. The process is embedded in the reaction $\pi^-\mathrm{Ni}\rightarrow\pi^-\gamma\;\mathrm{Ni}$, which is initiated by 190\,GeV pions impinging on a nickel target. The exchange of quasi-real photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, $Q^2<0.0015$\,(GeV/$c$)$^2$. From a sample of 63\,000 events the pion electric polarisability is determined to be $\alpha_\pi\ =\ (\,2.0\ \pm\ 0.6_{\mbox{\scriptsize stat}}\ \pm\ 0.7_{\mbox{\scriptsize syst}}\,) \times 10^{-4}\,\mbox{fm}^3$ under the …
The full Boltzmann hierarchy for dark matter-massive neutrino interactions
2020
The impact of dark matter-neutrino interactions on the measurement of the cosmological parameters has been investigated in the past in the context of massless neutrinos exclusively. Here we revisit the role of a neutrino-dark matter coupling in light of ongoing cosmological tensions by implementing the full Boltzmann hierarchy for three massive neutrinos. Our tightest 95% CL upper limit on the strength of the interactions, parameterized via $u_\chi =\frac{\sigma_0}{\sigma_{Th}}\left(\frac{m_\chi}{100 \text{GeV}}\right)^{-1}$, is $u_\chi\leq3.34 \cdot 10^{-4}$, arising from a combination of Planck TTTEEE data, Planck lensing data and SDSS BAO data. This upper bound is, as expected, slightly …