Publications
340
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1
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285
Recent Additions
- PublicationMono-Higgs and Mono-Z Production in the Minimal Vector Dark Matter Model(2024-07-01)The minimal vector dark matter is a viable realization of the minimal dark matter paradigm. It extends the standard model by the inclusion of a vector matter field in the adjoint representation of SU(2)L. The dark matter candidate corresponds to the neutral component of the new vector field (V0). Previous studies have shown that the model can explain the observed dark matter abundance while evading direct and indirect searches. At colliders, the attention has been put on the production of the charged companions of the dark matter candidate. In this work, we focus on the mono-Higgs and mono-Z signals at Hadron colliders. The new charged vectors (V±) are invisible unless a dedicated search is performed. Consequently, we assume that the mono-Higgs and mono-Z processes correspond to the pp→hV+,0V−,0 and pp→ZV+,0V−,0 reactions, respectively. We show that, while the pp→hV+,0V−,0 is more important, both channels may produce significant signals at the HL-LHC and colliders running at s=27 TeV and 100 TeV, probing almost the complete parameter space.
- PublicationSequentially loop-generated quark and lepton mass hierarchies in an extended Inert Higgs Doublet model(2019-06-01)Abstract Extended scalar and fermion sectors offer new opportunities for generating the observed strong hierarchies in the fermion mass and mixing patterns of the Standard Model (SM). In this work, we elaborate on the prospects of a particular extension of the Inert Higgs doublet model where the SM hierarchies are generated sequentially by radiative virtual corrections in a fully renormalisable way, i.e. without adding any non-renormalisable Yukawa terms or soft-breaking operators to the scalar potential. Our model has a potential to explain the recently observed R K and R K∗ anomalies, thanks to the non universal U1X assignments of the fermionic fields that yield non universal Z′ couplings to fermions. We explicitly demonstrate the power of this model for generating the realistic quark, lepton and neutrino mass spectra. In particular, we show that due to the presence of both continuous and discrete family symmetries in the considered framework, the top quark acquires a tree-level mass, lighter quarks and leptons get their masses at one- and two-loop order, while neutrino masses are generated at three-loop level. The minimal field content, particle spectra and scalar potential of this model are discussed in detail.
- PublicationA new technique for separation of partial discharge sources and electromagnetic noise in radiofrequency measurements using energy ratios of different antennas(2021-06-01)One of the main tools for monitoring the condition of high voltage equipment is the measurement of partial discharges (PD). The electromagnetic (EM) radiation originated from this degradation phenomenon can be captured by various types of ultra-high frequency (UHF) antennas carefully designed and optimised for specific frequency bands. However, the presence of environmental noise may limit the use of this technique. Different types of monopole antennas normally used in UHF PD measurement have been evaluated in order to validate the performance of a novel separation technique of EM sources. Accordingly, a new separation technique based on the energy ratio of the captured signals was developed, considering noise interferences. The results revealed that the new technique allows an adequate separation, even when three sources act simultaneously.
- PublicationConstraints on New Physics in Electron g-2 from a Search for Invisible Decays of a Scalar, Pseudoscalar, Vector, and Axial Vector(2021-05-25)We performed a search for a new generic X boson, which could be a scalar (S), pseudoscalar (P), vector (V) or an axial vector (A) particle produced in the 100 GeV electron scattering off nuclei, e−Z→e−ZX, followed by its invisible decay in the NA64 experiment at CERN. No evidence for such process was found in the full NA64 data set of 2.84×1011 electrons on target. We place new bounds on the S,P,V,A coupling strengths to electrons, and set constraints on their contributions to the electron anomalous magnetic moment ae, |ΔaX|≲10−15−10−13 for the X mass region mX≲1 GeV. These results are an order of magnitude more sensitive compared to the current accuracy on ae from the electron g−2 experiments and recent high-precision determination of the fine structure constant.
- PublicationImproved Λp Elastic Scattering Cross Sections between 0.9 and 2.0 GeV/c as a Main Ingredient of the Neutron Star Equation of State(2021-12-31)Strange matter is believed to exist in the cores of neutron stars based on simple kinematics. If this is true, then hyperon-nucleon interactions will play a significant part in the neutron star equation of state. Yet, compared to other elastic scattering processes, there is very little data on Λ-N scattering. This experiment utilized the CEBAF Large Acceptance Spectrometer (CLAS) detector to study the Λp → Λp elastic scattering cross section in the incident Λ momentum range 0.9–2.0 GeV=c. These are the first data on this reaction since the 1970s. The new cross sections have significantly better accuracy and precision than the existing world data, and the techniques developed here can also be used in future experiments.
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- PublicationMeasurement of two-photon exchange effect by comparing elastic e±p cross sections(2017-06-01)Background: The electromagnetic form factors of the proton measured by unpolarized and polarized electron scattering experiments show a significant disagreement that grows with the squared four-momentum transfer (Q2). Calculations have shown that the two measurements can be largely reconciled by accounting for the contributions of two-photon exchange (TPE). TPE effects are not typically included in the standard set of radiative corrections since theoretical calculations of the TPE effects are highly model dependent, and, until recently, no direct evidence of significant TPE effects has been observed. Purpose: We measured the ratio of positron-proton to electron-proton elastic-scattering cross sections in order to determine the TPE contribution to elastic electron-proton scattering and thereby resolve the proton electric form factor discrepancy. Methods: We produced a mixed simultaneous electron-positron beam in Jefferson Lab’s Hall B by passing the 5.6-GeV primary electron beam through a radiator to produce a bremsstrahlung photon beam and then passing the photon beam through a convertor to produce electron-positron pairs. The mixed electron-positron (lepton) beam with useful energies from approximately 0.85 to 3.5 GeV then struck a 30-cm-long liquid hydrogen (LH2) target located within the CEBAF Large Acceptance Spectrometer (CLAS). By detecting both the scattered leptons and the recoiling protons, we identified and reconstructed elastic scattering events and determined the incident lepton energy. A detailed description of the experiment is presented. Results: We present previously unpublished results for the quantity R2γ , the TPE correction to the elasticscattering cross section, at Q2 ≈ 0.85 and 1.45 GeV2 over a large range of virtual photon polarization ε. Conclusions: Our results, along with recently published results from VEPP-3, demonstrate a nonzero contribution from TPE effects and are in excellent agreement with the calculations that include TPE effects and largely reconcile the form-factor discrepancy up to Q2 ≈ 2 GeV2 . These data are consistent with an increase in R2γ with decreasing ε at Q2 ≈ 0.85 and 1.45 GeV2 . There are indications of a slight increase in R2γ with Q2.
- PublicationAn Assessment of the Metal Removal Capability of Endemic Chilean Species(2022-03-01)In Chile, there are several abandoned mine tailing impoundments near population centers that need to be remediated. In this study, the ability of Oxalis gigantea, Cistanthe grandiflora, and Puya berteroniana to remove Zn, Ni, and Cr from mine tailings was evaluated. The plants’ removal efficiency, bioconcentration, and translocation factors regarding these metals were determined to assess the ability of certain endemic species from Northern and Central Chile to extract or stabilize metals. After a period of seven months, the chemical analysis of plants and tailings, together with the statistical treatment of data, indicated the inability of all the species to translocate Ni, Cr, or Zn with a translocation factor lower than one. The results showed the stabilizing character of Oxalis gigantea, Puya berteroniana, and Cistanthe grandiflora for Zn, with a bioconcentration factor close to 1.2 in all cases, and the same ability of the latter two species for Cr, with a bioconcentration factor of 1.5 in the case of Cistanthe grandiflora and 1.7 for Puya berteroniana. Finally, a removal efficiency of 9.3% was obtained with Cistanthe grandiflora for Cr and 15% for Ni; values lower than 6.4% were obtained for Zn in all cases. Improvements in the process should be sought to enhance the performance of these species for the accumulation of the target metals.
- Organizational Unit
- PublicationRobust self-organizing maps(2004-01-01)The Self Organizing Map (SOM) model is an unsupervised learning neural network that has been successfully applied as a data mining tool. The advantages of the SOMs are that they preserve the topology of the data space, they project high dimensional data to a lower dimension representation scheme, and are able to find similarities in the data. However, the learning algorithm of the SOM is sensitive to the presence of noise and outliers as we will show in this paper. Due to the influence of the outliers in the learning process, some neurons (prototypes) of the ordered map get located far from the majority of data, and therefore, the network will not effectively represent the topological structure of the data under study. In this paper, we propose a variant to the learning algorithm that is robust under the presence of outliers in the data by being resistant to these deviations. We call this algorithm Robust SOM (RSOM). We will illustrate our technique on synthetic and real data sets.
- Organizational Unit