The branching fraction ratio $mathcal{R}(D^{*}) equiv mathcal{B}(overline{B}^0 to D^{*+}tau^{-}overline{ u}_{tau})/mathcal{B}(overline{B}^0 to D^{*+}mu^{-}overline{ u}_{mu})$ is measured using a sample of proton-proton collision data corresponding to
3.0invfb of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $tau^{-} to mu^{-}overline{ u}_{mu} u_{tau}$. The semitauonic decay is sensitive to contributions from non-Standard-Model particles that preferentially couple to the third generation of fermions, in particular Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate $overline{B}^0$ decays gives $mathcal{R}(D^{*}) = 0.336 pm 0.027(stat) pm 0.030 (syst)$. This result, which is the first measurement of this quantity at a hadron collider, is $2.1$ standard deviations larger than the value expected from lepton universality in the Standard Model.
In this paper we discuss two constructions of an effective field theory starting from a local interaction functional. One relies on the well-established graphical combinatorics of the BPHZ algorithm to renormalize divergent Feynman amplitudes. The ot
her, more recent and due to Costello, relies on an inductive construction of local counterterms that uses no graphical combinatorics whatsoever. We show that these two constructions produce the same effective field theory.
A novel computational, non-iterative and noise-robust reconstruction method is introduced for the planar anisotropic inverse conductivity problem. The method is based on bypassing the unstable step of the reconstruction of the values of the isotherma
l coordinates on the boundary of the domain. Non-uniqueness of the inverse problem is dealt with by recovering the unique isotropic conductivity that can be achieved as a deformation of the measured anisotropic conductivity by emph{isothermal coordinates}. The method shows how isotropic D-bar reconstruction methods have produced reasonable and informative reconstructions even when used on EIT data known to come from anisotropic media, and when the boundary shape is not known precisely. Furthermore, the results pave the way for regularized anisotropic EIT. Key aspects of the approach involve D-bar methods and inverse scattering theory, complex geometrical optics solutions, and quasi-conformal mapping techniques.
In Electrical Impedance Tomography (EIT), the internal conductivity of a body is recovered via current and voltage measurements taken at its surface. The reconstruction task is a highly ill-posed nonlinear inverse problem, which is very sensitive to
noise, and requires the use of regularized solution methods, of which D-bar is the only proven method. The resulting EIT images have low spatial resolution due to smoothing caused by low-pass filtered regularization. In many applications, such as medical imaging, it is known emph{a priori} that the target contains sharp features such as organ boundaries, as well as approximate ranges for realistic conductivity values. In this paper, we use this information in a new edge-preserving EIT algorithm, based on the original D-bar method coupled with a deblurring flow stopped at a minimal data discrepancy. The method makes heavy use of a novel data fidelity term based on the so-called {em CGO sinogram}. This nonlinear data step provides superior robustness over traditional EIT data formats such as current-to-voltage matrices or Dirichlet-to-Neumann operators, for commonly used current patterns.
We have fabricated AlGaAs/GaAs heterostructure devices in which the conduction channel can be populated with either electrons or holes simply by changing the polarity of a gate bias. The heterostructures are entirely undoped, and carriers are instead
induced electrostatically. We use these devices to perform a direct comparison of the scattering mechanisms of two-dimensional (2D) electrons ($mu_textrm{peak}=4times10^6textrm{cm}^2/textrm{Vs}$) and holes ($mu_textrm{peak}=0.8times10^6textrm{cm}^2/textrm{Vs}$) in the same conduction channel with nominally identical disorder potentials. We find significant discrepancies between electron and hole scattering, with the hole mobility being considerably lower than expected from simple theory.
Examination of loading the isotopes $^{85}$Rb and $^{87}$Rb simultaneously into a shallow far-off-resonance trap (FORT) has revealed an unexpected decrease in maximum atom number loaded as compared to loading either isotope alone. The simultaneous lo
ading of the FORT will be affected by additional homonuclear and heteronuclear light-assisted collisional losses. However, these losses are measured and found to be insufficient to explain the observed drop in total number of atoms loaded into the FORT. We find that our observations are consistent with a decrease in loading rate caused by inter-isotope disruptions of the efficient laser cooling required to load atoms into the optical trap.
We report a measurement of the inclusive semileptonic branching fraction of the B_s meson using data collected with the BaBar detector in the center-of-mass (CM) energy region above the Upsilon(4S) resonance. We use the inclusive yield of phi mesons
and the phi yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B_s mesons relative to all B mesons as a function of CM energy. The inclusive semileptonic branching fraction of the B_s meson is determined to be B(B_s to l nu X)=9.5 (+2.5/-2.0)(stat)(+1.1/-1.9)(syst)%, where l indicates the average of e and mu.
One of the major challenges of modern cosmology is the detection of B-mode polarization anisotropies in the CMB. These originate from tensor fluctuations of the metric produced during the inflationary phase. Their detection would therefore constitute
a major step towards understanding the primordial Universe. The expected level of these anisotropies is however so small that it requires a new generation of instruments with high sensitivity and extremely good control of systematic effects. We propose the QUBIC instrument based on the novel concept of bolometric interferometry, bringing together the sensitivity advantages of bolometric detectors with the systematics effects advantages of interferometry. Methods: The instrument will directly observe the sky through an array of entry horns whose signals will be combined together using an optical combiner. The whole set-up is located inside a cryostat. Polarization modulation will be achieved using a rotating half-wave plate and interference fringes will be imaged on two focal planes (separated by a polarizing grid) tiled with bolometers. We show that QUBIC can be considered as a synthetic imager, exactly similar to a usual imager but with a synthesized beam formed by the array of entry horns. Scanning the sky provides an additional modulation of the signal and improve the sky coverage shape. The usual techniques of map-making and power spectrum estimation can then be applied. We show that the sensitivity of such an instrument is comparable with that of an imager with the same number of horns. We anticipate a low level of beam-related systematics thanks to the fact that the synthesized beam is determined by the location of the primary horns. Other systematics should be under good control thanks to an autocalibration technique, specific to our concept, that will permit the accurate determination of most of the systematics parameters.
The ATLAS trigger has been used very successfully to collect collision data during 2009 and 2010 LHC running at centre of mass energies of 900 GeV, 2.36 TeV, and 7 TeV. This paper presents the ongoing work to commission the ATLAS trigger with proton
collisions, including an overview of the performance of the trigger based on extensive online running. We describe how the trigger has evolved with increasing LHC luminosity and give a brief overview of plans for forthcoming LHC running.
The purpose of this paper is to describe an analogue of a construction of Costello in the context of finite-dimensional differential graded Frobenius algebras which produces closed forms on the decorated moduli space of Riemann surfaces. We show that
this construction extends to a certain natural compactification of the moduli space which is associated to the modular closure of the associative operad, due to the absence of ultra-violet divergences in the finite-dimensional case. We demonstrate that this construction is equivalent to the dual construction of Kontsevich.
