Probing nonstandard lepton number violating interactions in neutrino oscillations

We discuss lepton number violating processes in the context of long-baseline neutrino oscillations. We summarise and compare neutrino flavour oscillations in quantum mechanics and quantum field theory, both for standard oscillations and for those that violate lepton number. When the active neutrinos are Majorana in nature, the required helicity reversal gives a strong suppression by the neutrino mass over the energy, $(m_{\nu}/E_{\nu})^{2}$. Instead, the presence of non-standard lepton number violating interactions incorporating right-handed lepton currents at production or detection alleviate the mass suppression while also factorising the oscillation probability from the total rate. Such interactions arise from dimension-six operators in the low energy effective field theory of the Standard Model. We derive general and simplified expressions for the lepton number violating oscillation probabilities and use limits from MINOS and KamLAND to place bounds on the interaction strength in interplay with the unknown Majorana phases in neutrino mixing. We compare the bounds with those from neutrinoless double beta decay and other microscopic lepton number violating processes and outline the requirements for future short- and long-baseline neutrino oscillation experiments to improve on the existing bounds.Comment: 33 pages, 9 figure

Diesel Engine Noise Source Visualization by Using Compressive Sensing Algorithms

To identify sound source locations by using Near-field Acoustical Holography (NAH), a large number of microphone measurements is generally required in order to cover the source region and ensure a sufficiently high spatial sampling rate: it may require hundreds of microphones. As a result, such measurements are costly, a fact which has limited the industrial application of NAH to identify sound source locations. However, recently, it has been shown possible to identify concentrated sound sources with a limited number of microphone measurements based on Compressive Sensing theory. In the present work, sound radiation from the front face of a diesel engine was measured by using one set of measurements from a thirty-five-channel combo-array placed in front of the engine. The locations of significant noise sources were then identified by using two algorithms: i.e., l1-norm minimization and a hybrid approach which combined Wideband Acoustical Holography (WBH) and l1- norm minimization. It was found that both algorithms could successfully localize and visualize the major noise sources over a broad range of frequencies, even when using a relatively small number of microphones. Finally, comments are made on sound field reconstruction differences between the two algorithms

A Hybrid Compressive Approach to Noise Source Visualization: Application to a Diesel Engine

To identify sound source locations by using Fourier-based Near-field Acoustical Holography (NAH), a large number of microphone measurements is generally required to span the source region and ensure a sufficiently high spatial sampling rate. As a result, such measurements are costly, a fact which has discouraged the industrial application of NAH to identify sound source locations. However, recently, compressive sensing approaches have made it feasible to identify concentrated sound sources with a limited number of microphone measurements. In the present work, sound radiation from the front face of a diesel engine was measured by using one set of measurements from a 35-channel combo-array. The locations of significant noise sources were then identified by using three compressive sensing algorithms: Wideband Acoustical Holography (WBH), l1-norm minimization, and a hybrid approach which combined WBH and l1-norm minimization. The latter approach takes advantage of the l1’ norm’s ability to locate spatially distinct sources, and WBH’s ability to suppress “ghost” sources. It was found that the hybrid algorithm can localize and visualize the major noise sources over a broad range of frequencies, even though using a relatively small number of microphones. Finally, comments are made regarding sound field reconstruction differences between the algorithms

Probing New Physics with Long-Range Neutrino Interactions: An Effective Field Theory Approach

We investigate forces induced by the exchange of two light neutrinos between Standard Model (SM) fermions in the presence of effective operators parametrising physics beyond the SM. We first set up a general framework in which we derive the long-range potential mediated by weakly interacting neutrinos in the SM, retaining both spin-independent and spin-dependent terms. We then derive neutrino-mediated potentials when there are vector, scalar and tensor non-standard interactions present as well as an exotic neutrino magnetic moment. Examining the phenomenology of such long-range potentials in atomic scale laboratory experiments, we derive upper bounds on the Wilson coefficients of the effective operators and compare these to those from processes such as charged lepton flavour violation.Comment: 60 pages, 6 figure

Neutrinoless double beta decay via light neutralinos in R-parity violating supersymmetry

We perform a study of neutrinoless double beta (0νββ) decay mediated by the lightest neutralino of arbitrary mass in the minimal supersymmetric Standard Model (MSSM) under the presence of R-parity violating trilinear interactions. In this scenario, the exchange of the lightest neutralino can result in 0νββ decay of either long-range or short-range behaviour, depending on the neutralino mass. Using nuclear matrix elements calculated in the interacting boson model, we use an interpolation between the long- and short-range behaviours with an approximate formula. The non-observation of 0νββ decay is then used to place constraints on the supersymmetry parameter space, compatible with constraints from collider experiments. We compare these constraints to bounds from pion decays, CKM unitarity and big bang nucleosynthesis

Perception of Diesel Engine Gear Rattle Noise

Component sound quality is an important factor in the design of competitive diesel engines. One component noise that causes complaints is the gear rattle that originates in the front-of-engine gear train which drives the fuel pump and other accessories. The rattle is caused by repeated tooth impacts resulting from fluctuations in differential torsional acceleration of the driving gears. These impacts generate a broadband, impulsive noise that is often perceived as annoying. In most previous work, the overall sound quality of diesel engines has been considered without specifically focusing on predicting the perception of gear rattle. Gear rattle level has been quantified based on angular acceleration measurements, but those measurements can be difficult to perform. Here, the emphasis was on developing a metric based on subjective testing of the perception of gear rattle. In the first part of the present work, a method to simulate gear rattle noise and incorporate it into a no-gear-rattle (baseline) recording was developed. That procedure enabled controlled variation of rattle within the total engine noise signal. The simulations were then used in a psychoacoustic test that was designed to quantify detectable levels, perception of growth, and increase in annoyance due to the presence of gear rattle noise. Forty subjects participated in the threshold detection tests and a paired comparison annoyance test. The responses of people who reported having experience with diesel engines were compared to those of a more general population. The subjects with diesel engine experience were found to be better at detecting gear rattle noise and found rattle more annoying than the other subjects, particularly at high rattle levels. Current work is focused on development of metrics that accurately reflect human responses to gear rattle

Probes of Heavy Sterile Neutrinos

We review probes of heavy sterile neutrinos, focusing on direct experimental searches and neutrinoless double beta decay. Working in a phenomenological parametrization, we emphasize the importance of the nature of sterile neutrinos in interpreting neutrinoless double beta decay searches. While current constraints on the active-sterile neutrino mixing are already stringent, we highlight planned future efforts that will probe regimes motivated by the lightness of active neutrinos

Diesel Engine Noise Source Visualization with Wideband Acoustical Holography

Wideband Acoustical Holography (WBH), which is a monopole-based, equivalent source procedure (J. Hald, “Wideband Acoustical Holography,” INTER-NOISE 2014), has proven to offer accurate noise source visualization results in experiments with a simple noise source: e.g., a loudspeaker (T. Shi, Y. Liu, J.S. Bolton, ”The Use of Wideband Holography for Noise Source Visualization”, NOISECON 2016). From a previous study, it was found that the advantage of this procedure is the ability to optimize the solution in the case of an under-determined system: i.e., when the number of measurements is much smaller than the number of parameters that must be estimated in the model. In the present work, a diesel engine noise source was measured by using one set of measurements from a thirty-five channel combo-array placed in front of the engine. The noise source distribution was reconstructed at the front face of diesel engine and it was possible to successfully localize and visualize the major noise sources over a broad range of frequencies, even when using a relatively small number of microphones, as in this case