Search results for "Particle physics"
showing 10 items of 6826 documents
Anomalous non-leptonic kaon decays
1992
8 páginas, 1 figura.
Pion photo- and electroproduction in relativistic baryon chiral perturbation theory and the chiral MAID interface
2013
We present a calculation of pion photo- and electroproduction in manifestly Lorentz-invariant baryon chiral perturbation theory up to and including order ${q}^{4}$. We fix the low-energy constants by fitting experimental data in all available reaction channels. Our results can be accessed via a Web interface, the so-called chiral MAID. We explain how our program works and how it can be used for further analysis.
Geometric approaches to particle physics
2008
Geometric approaches to particle physics have opened up new perspectives and unifying insights. After a few historical remarks I discuss the essence of the concept of G-theory: a primordial symmetry acting on a manifold and on the fields defined on it. This is then illustrated by the finite-dimensional case of Kaluza-Klein theories and by the infinite-dimensional case of chiral anomalies in Yang-Mills theories. In the latter case, a new and unifying description of topological and global anomalies is obtained.
Pion Production at Threshold as Test of Chiral Perturbation Theory
2003
An overview of recent results in threshold pion production is given. While the photoproduction data are in impressive agreement with calculations in the framework of Chiral Perturbation Theory, electroproduction data at low four-momentum transfer show severe deviations from these calculations.
ChPT parameters from tau-decay data
2015
Using the updated ALEPH V-A spectral function from tau decays, we determine the lowest spectral moments of the left-right correlator and extract dynamical information on order parameters of the QCD chiral symmetry breaking. Uncertainties associated with violations of quark-hadron duality are estimated from the data, imposing all known short-distance constraints on a resonance-based parametrization. Employing proper pinched weight functions, we obtain an accurate determination of the effective chiral couplings L10 and C87 and the dimension-six and -eight contributions in the Operator Product Expansion.
Excited charmed mesons in chiral perturbation theory
1992
Abstract Heavy meson, p- to s-wave, one-pion transitions are studied in the context of the union of heavy quark and chiral symmetries. The interactions are described by an effective lagrangian density invariant under the combined heavy quark and chiral symmetries. We study the pattern of the heavy quark symmetry breaking by considering 1 m Q corrections to the infinite mass limit.
Antennas for the detection of radio emission pulses from cosmic-ray induced air showers at the Pierre Auger Observatory.
2012
The Pierre Auger Observatory is exploring the potential of the radio detection technique to study extensive air showers induced by ultra-high energy cosmic rays. The Auger Engineering Radio Array (AERA) addresses both technological and scientific aspects of the radio technique. A first phase of AERA has been operating since September 2010 with detector stations observing radio signals at frequencies between 30 and 80 MHz. In this paper we present comparative studies to identify and optimize the antenna design for the final configuration of AERA consisting of 160 individual radio detector stations. The transient nature of the air shower signal requires a detailed description of the antenna s…
Searches for Large-Scale Anisotropy in the Arrival Directions of Cosmic Rays Detected above Energy of $10^{19}$ eV at the Pierre Auger Observatory an…
2014
Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above 1019 eV is presented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a series of anisotropy searches, and in particular to report on the angular power spectrum of cosmic rays above 1019 eV. No significant devia…
Performance of jet substructure techniques for large-$R$ jets in proton-proton collisions at $\sqrt{s}$ = 7 TeV using the ATLAS detector
2013
This paper presents the application of a variety of techniques to study jet substructure. The performance of various modified jet algorithms, or jet grooming techniques, for several jet types and event topologies is investigated for jets with transverse momentum larger than 300 GeV. Properties of jets subjected to the mass-drop filtering, trimming, and pruning algorithms are found to have a reduced sensitivity to multiple proton-proton interactions, are more stable at high luminosity and improve the physics potential of searches for heavy boosted objects. Studies of the expected discrimination power of jet mass and jet substructure observables in searches for new physics are also presented.…
Coherence resonance in Bonhoeffer-Van der Pol circuit
2009
International audience; A nonlinear electronic circuit simulating the neuronal activity in a noisy environment is proposed. This electronic circuit is exactly ruled by the set of Bonhoeffer-Van Der Pol equations and is excited with a Gaussian noise. Without external deterministic stimuli, it is shown that the circuit exhibits the so-called 'coherence resonance' phenomenon.