arXiv subjects

Irina Nasteva

Publications and source records attributed to Irina Nasteva.

11 recordsLinked to original sources

arXiv2026

Searches for CEνNS and Physics beyond the Standard Model using Skipper-CCDs at CONNIE

The Coherent Neutrino-Nucleus Interaction Experiment (CONNIE) aims to detect the coherent scattering (CE$ν$NS) of reactor antineutrinos off silicon nuclei using thick fully-depleted high-resistivity silicon CCDs. Two Skipper-CCD sensors with sub-electron readout noise capability were installed at the experiment next to the Angra-2 reactor in 2021, making CONNIE the first experiment to employ Skipper-CCDs for reactor neutrino detection. We report on the performance of the Skipper-CCDs, the new data processing and data quality selection techniques and the event selection for CE$ν$NS interactions, which enable CONNIE to reach a record low detection threshold of 15 eV. The data were collected over 300 days in 2021-2022 and correspond to exposures of 14.9 g-days with the reactor-on and 3.5 g-days with the reactor-off. The difference between the reactor-on and off event rates shows no excess and yields upper limits at 95% confidence level for the neutrino interaction rates comparable with previous CONNIE limits from standard CCDs and higher exposures. Searches for new neutrino interactions beyond the Standard Model were performed, yielding an improvement on the previous CONNIE limit on a simplified model with light vector mediators. A first dark matter (DM) search by diurnal modulation was performed by CONNIE and the results represent the best limits on the DM-electron scattering cross-section, obtained by a surface-level experiment. These promising results, obtained using a very small-mass sensor, illustrate the potential of Skipper-CCDs to probe rare neutrino interactions and motivate the plans to increase the detector mass in the near future.

hep-ex↗

arXiv2024

Search for reactor-produced millicharged particles with Skipper-CCDs at the CONNIE and Atucha-II experiments

Millicharged particles, proposed by various extensions of the standard model, can be created in pairs by high-energy photons within nuclear reactors and can interact electromagnetically with electrons in matter. Recently, the existence of a plasmon peak in the interaction cross-section with silicon in the eV range was highlighted as a promising approach to enhance low-energy sensitivities. The CONNIE and Atucha-II reactor neutrino experiments utilize Skipper-CCD sensors, which enable the detection of interactions in the eV range. We present world-leading limits on the charge of millicharged particles within a mass range spanning six orders of magnitude, derived through a comprehensive analysis and the combination of data from both experiments.

hep-ex↗

arXiv2022

Search for coherent elastic neutrino-nucleus scattering at a nuclear reactor with CONNIE 2019 data

The Coherent Neutrino-Nucleus Interaction Experiment (CONNIE) is taking data at the Angra 2 nuclear reactor with the aim of detecting the coherent elastic scattering of reactor antineutrinos with silicon nuclei using charge-coupled devices (CCDs). In 2019 the experiment operated with a hardware binning applied to the readout stage, leading to lower levels of readout noise and improving the detection threshold down to 50 eV. The results of the analysis of 2019 data are reported here, corresponding to the detector array of 8 CCDs with a fiducial mass of 36.2 g and a total exposure of 2.2 kg-days. The difference between the reactor-on and reactor-off spectra shows no excess at low energies and yields upper limits at 95% confidence level for the neutrino interaction rates. In the lowest-energy range, 50-180 eV, the expected limit stands at 34 (39) times the standard model prediction, while the observed limit is 66 (75) times the standard model prediction with Sarkis (Chavarria) quenching factors.

hep-ex↗

arXiv2021

Low-energy reactor neutrino physics with the CONNIE experiment

The Coherent Neutrino-Nucleus Interaction Experiment (CONNIE) uses fully depleted high-resistivity CCDs (charge coupled devices) with the aim of detecting the coherent elastic scattering of reactor antineutrinos off silicon nuclei and probing physics beyond the Standard Model. The analysis of the 2016--2018 data allowed us to set an upper limit at 95% confidence level on the coherent scattering rate, which was used to place stringent constraints on simplified extensions of the Standard Model with light scalar and vector mediators. In 2019, the experiment operated with an improved readout and a lower energy threshold of 50 eV. We present the performance of the CONNIE experiment, new results of the analysis of 2019 data, and the recent update of the detector with skipper CCDs.

physics.ins-det↗

arXiv2020

Search for light mediators in the low-energy data of the CONNIE reactor neutrino experiment

The CONNIE experiment is located at a distance of 30 m from the core of a commercial nuclear reactor, and has collected a 3.7 kg-day exposure using a CCD detector array sensitive to an $\sim$1 keV threshold for the study of coherent neutrino-nucleus elastic scattering. Here we demonstrate the potential of this low-energy neutrino experiment as a probe for physics Beyond the Standard Model, by using the recently published results to constrain two simplified extensions of the Standard Model with light mediators. We compare the new limits with those obtained for the same models using neutrinos from the Spallation Neutron Source. Our new constraints represent the best limits for these simplified models among the experiments searching for CE$ν$NS for a light vector mediator with mass $M_{Z^{\prime}}<$ 10 MeV, and for a light scalar mediator with mass $M_ϕ<$ 30 MeV. These results constitute the first use of the CONNIE data as a probe for physics Beyond the Standard Model.

hep-ex↗

arXiv2019

Exploring low-energy neutrino physics with the Coherent Neutrino Nucleus Interaction Experiment (CONNIE)

The Coherent Neutrino-Nucleus Interaction Experiment (CONNIE) uses low-noise fully depleted charge-coupled devices (CCDs) with the goal of measuring low-energy recoils from coherent elastic scattering (CE$ν$NS) of reactor antineutrinos with silicon nuclei and testing nonstandard neutrino interactions (NSI). We report here the first results of the detector array deployed in 2016, considering an active mass 47.6 g (8 CCDs), which is operating at a distance of 30 m from the core of the Angra 2 nuclear reactor, with a thermal power of 3.8 GW. A search for neutrino events is performed by comparing data collected with reactor on (2.1 kg-day) and reactor off (1.6 kg-day). The results show no excess in the reactor-on data, reaching the world record sensitivity down to recoil energies of about 1 keV (0.1 keV electron-equivalent). A 95% confidence level limit for new physics is established at an event rate of 40 times the one expected from the standard model at this energy scale. The results presented here provide a new window to low-energy neutrino physics, allowing one to explore for the first time the energies accessible through the low threshold of CCDs. They will lead to new constrains on NSI from the CE$ν$NS of antineutrinos from nuclear reactors.

physics.ins-det↗

arXiv2016

Summary of the 2015 LHCb workshop on multi-body decays of D and B mesons

This document contains a summary of the LHCb workshop on multi-body decays of D and B mesons, held at CBPF, Rio de Janeiro, in July 2015. The workshop was focused on issues related to amplitude analysis of three- and four-body hadronic decays. In addition to selected LHCb results, contributions from guest theorists are included.

hep-ex↗

arXiv2013

Studies of charmless B decays including CP violation effects

The latest experimental results in charmless B decays are presented with a focus on CP violation measurements. These include the first observation of CP violation in B_s decays, evidence for CP violation in charmless three-body B+ decays, branching fraction measurements of B+ --> ppK+ decays and the first observation of the decay B_s --> phi K*0 from LHCb, a comparison of B+ --> K+K-K+ CP violation measurements between LHCb and BaBar, and the first evidence for the decay B0 --> K+K-pi0 obtained by Belle.

hep-ex↗

arXiv2009

SuperNEMO - the next generation double beta decay experiment

The SuperNEMO experiment is being designed to search for neutrinoless double beta decay to test if neutrinos are Majorana particles. The experimental technique follows that of the currently running NEMO-3 experiment, which successfully combines tracking and calorimetry to measure the topology and energy of the final state electrons. Unique particle identification capabilities of SuperNEMO will be employed with about 100 kg of 82 Se and will reach sensitivity to a half-life of about 2 x 10^26 years, which corresponds to Majorana neutrino masses of about 50 meV, depending on the calculated value of the nuclear matrix element. In this poster, the current status of the SuperNEMO project is presented.

hep-ex↗

arXiv2008

Neutrinoless double beta decay search with the NEMO 3 experiment

The NEMO 3 experiment searches for neutrinoless double beta decay and makes precision measurements of two-neutrino double beta decay in seven isotopes. The latest two-neutrino half-life results are presented, together with the limits on neutrinoless half-lives and the corresponding effective Majorana neutrino masses. Also given are the limits obtained on neutrinoless double beta decay mediated by Rp-violating SUSY, right-hand currents and different Majoron emission modes.

hep-ex↗

arXiv2007

The SuperNEMO double beta decay experiment

The SuperNEMO project studies the feasibility of employing a technique of tracking plus calorimetry to search for neutrinoless double beta decay in 100 kg of enriched isotopes. It aims to reach an effective neutrino mass sensitivity of 50 meV. The current status of the SuperNEMO R&D programme is described, focusing on the main areas of improvement.

physics.ins-det↗