arXiv subjects

D. Frekers

Publications and source records attributed to D. Frekers.

At least 19 recordsLinked to original sources

arXiv2025

A two-step strategy to identify episodic sources of gravitational waves and high energy neutrinos in starburst galaxies

Supermassive black hole mergers with spin-flips accelerate energetic particles through their precessing relativistic jets, producing high energy neutrinos and finally gravitational waves. In star formation massive stars come in pairs, triplets and quadruplets, allowing second generation mergers of the remnants with discrepant spin directions. The Gravitational Wave (GW) data support such a scenario. Earlier we suggested that stellar mass black hole mergers (visible in M82) with an associated spin-flip analogously allow the acceleration of energetic particles, with ensuing high energy neutrinos and high energy photons, and finally producing gravitational waves. At cosmic distances only the gravitational waves and the neutrinos remain detectable. Here we generalize the argument to starburst and normal galaxies throughout their cosmic evolution, and show that these galaxies may dominate over Active Galactic Nuclei (AGN) in the flux of ultra-high energy particles observed at Earth. All these sources contribute to the cosmic neutrino background, as well as the gravitational wave background (they detected the lower frequencies). We outline a search strategy to find such episodic sources, which requires to include both luminosity and flux density.

astro-ph.HE↗

arXiv2024

Cosmic ray contributions from rapidly rotating stellar mass black holes: Cosmic Ray GeV to EeV proton and anti-proton sources

In Radio Super Novae (RSNe) a magnetic field of $(B \, \times \, r) \, = \, 10^{16.0 \pm 0.12} \, {\rm Gauss \, \times \, cm}$ is observed; these are the same numbers for Blue Super Giant (BSG) star explosions as for Red Super Giant (RSG) star explosions, despite their very different wind properties. The EHT data for M87 as well for low power radio galaxies all show consistency with just this value of the quantity $(B \, \times \, r )$, key for angular momentum and energy transport, and can be derived from the radio jet data. We interpret this as a property of the near surroundings of a black hole (BH) at near maximal rotation, independent of BH mass. In the commonly used green onion model, in which a $2 \, \pi$ flow changes over to a jet flow we interpret this as a wind emanating from the BH/accretion disk system and its surroundings. Near the BH collisions in the wind can produce a large fraction of anti-protons. In this scenario the cosmic Ray (CR) population from the wind/jet is proposed to be visible as EeV protons and anti-protons in the CR data to EeV energy, with a $E^{-7/3}$ spectrum. This can be connected to a concept of inner and outer Penrose zones in the ergo-region. The observed numbers for the magnetic field imply the Planck time as the governing time scale: A BH rotating near maximum can accept a proton per log bin of energy in an extended spectrum with the associated pions every Planck time.

astro-ph.HE↗

arXiv2024

Loaded layer-cake model for cosmic ray interaction around exploding super-giant stars making black holes

The AMS experiment on the International Space Station has provided detailed cosmic ray spectra for various elements, revealing that interactions significantly reduce fluxes up to about 100 GV rigidity. This necessitates revisiting current cosmic ray interaction models. A new model proposed here involves cosmic ray interactions first in the wind shock shell of supergiant stars and second in the OB-Superbubble around supernovae. These stars, including red and blue supergiants, produce black holes and drive electric currents in winds and jets. Variability in these winds creates temporary electric fields that accelerate particles, resulting in steep spectra with synchrotron losses, and analogous hadron spectra produce a flat magnetic irregularity spectrum. This model matches AMS data, explaining cosmic ray spectra below 100 GV. The model predicts a secondary/primary ratio slope of -1/3 and a primary flux reduction below 100 GV relative to a power-law spectrum with slope +2. Key aspects are: a larger interaction column due to heavy element enrichment and a minor secondary contribution even for elements like He, C, and O, as indicated by the $^3$He/$^4$He ratio. This model also accounts for cosmic ray anti-protons, gamma-ray spectra, and high-energy neutrinos, including contributions from ISM-SNe.

astro-ph.HE↗

arXiv2022

A Search for Electron Neutrino Transitions to Sterile States in the BEST Experiment

The Baksan Experiment on Sterile Transitions (BEST) probes the gallium anomaly and its possible connections to oscillations between active and sterile neutrinos. Based on the Gallium-Germanium Neutrino Telescope (GGNT) technology of the SAGE experiment, BEST employs two zones of liquid Ga target to explore neutrino oscillations on the meter scale. Oscillations on this short scale could produce deficits in the $^{71}$Ge production rates within the two zones, as well as a possible rate difference between the zones. From July 5th to October 13th 2019, the two-zone target was exposed to a primarily monoenergetic, 3.4-MCi $^{51}$Cr neutrino source 10 times for a total of 20 independent $^{71}$Ge extractions from the two Ga targets. The $^{71}$Ge production rates from the neutrino source were measured from July 2019 to March 2020. At the end of these measurements, the counters were filled with $^{71}$Ge doped gas and calibrated during November 2020. In this paper, results from the BEST sterile neutrino oscillation experiment are presented in details. The ratio of the measured $^{71}$Ge production rates to the predicted rates for the inner and the outer target volumes are calculated from the known neutrino capture cross section. Comparable deficits in the measured ratios relative to predicted values are found for both zones, with the $4 σ$ deviations from unity consistent with the previously reported gallium anomaly. If interpreted in the context of neutrino oscillations, the deficits give best fit oscillation parameters of $Δm^2=3.3^{+\infty}_{-2.3}$ eV$^2$ and sin$^2 2θ=0.42^{+0.15}_{-0.17}$, consistent with $ν_e \rightarrow ν_s$ oscillations governed by a surprisingly large mixing angle.

nucl-ex↗

arXiv2022

Results from the Baksan Experiment on Sterile Transitions (BEST)

The Baksan Experiment on Sterile Transitions (BEST) was designed to investigate the deficit of electron neutrinos, $ν_{e}$, observed in previous gallium-based radiochemical measurements with high-intensity neutrino sources, commonly referred to as the \textit{gallium anomaly}, which could be interpreted as evidence for oscillations between $ν_e$ and sterile neutrino ($ν_s$) states. A 3.414-MCi \nuc{51}{Cr} $ν_e$ source was placed at the center of two nested Ga volumes and measurements were made of the production of \nuc{71}{Ge} through the charged current reaction, \nuc{71}{Ga}($ν_e$,e$^-$)\nuc{71}{Ge}, at two average distances. The measured production rates for the inner and the outer targets respectively are ($54.9^{+2.5}_{-2.4}(\mbox{stat})\pm1.4 (\mbox{syst})$) and ($55.6^{+2.7}_{-2.6}(\mbox{stat})\pm1.4 (\mbox{syst})$) atoms of \nuc{71}{Ge}/d. The ratio ($R$) of the measured rate of \nuc{71}{Ge} production at each distance to the expected rate from the known cross section and experimental efficiencies are $R_{in}=0.79\pm0.05$ and $R_{out}= 0.77\pm0.05$. The ratio of the outer to the inner result is 0.97$\pm$0.07, which is consistent with unity within uncertainty. The rates at each distance were found to be similar, but 20-24\% lower than expected, thus reaffirming the anomaly. These results are consistent with $ν_e \rightarrow ν_s$ oscillations with a relatively large $Δm^2$ ($>$0.5 eV$^2$) and mixing sin$^2 2θ$ ($\approx$0.4).

nucl-ex↗

arXiv2018

Search for magnetic monopoles with the MoEDAL forward trapping detector in 2.11 fb$^{-1}$ of 13 TeV proton-proton collisions at the LHC

We update our previous search for trapped magnetic monopoles in LHC Run 2 using nearly six times more integrated luminosity and including additional models for the interpretation of the data. The MoEDAL forward trapping detector, comprising 222~kg of aluminium samples, was exposed to 2.11~fb$^{-1}$ of 13 TeV proton-proton collisions near the LHCb interaction point and analysed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges equal to the Dirac charge or above are excluded in all samples. The results are interpreted in Drell-Yan production models for monopoles with spins 0, 1/2 and 1: in addition to standard point-like couplings, we also consider couplings with momentum-dependent form factors. The search provides the best current laboratory constraints for monopoles with magnetic charges ranging from two to five times the Dirac charge.

hep-ex↗

arXiv2017

Search for magnetic monopoles with the MoEDAL forward trapping detector in 13 TeV proton-proton collisions at the LHC

MoEDAL is designed to identify new physics in the form of long-lived highly-ionising particles produced in high-energy LHC collisions. Its arrays of plastic nuclear-track detectors and aluminium trapping volumes provide two independent passive detection techniques. We present here the results of a first search for magnetic monopole production in 13 TeV proton-proton collisions using the trapping technique, extending a previous publication with 8 TeV data during LHC run-1. A total of 222 kg of MoEDAL trapping detector samples was exposed in the forward region and analysed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges exceeding half the Dirac charge are excluded in all samples and limits are placed for the first time on the production of magnetic monopoles in 13 TeV $pp$ collisions. The search probes mass ranges previously inaccessible to collider experiments for up to five times the Dirac charge.

hep-ex↗

arXiv2016

Electroweak Decay Studies of Highly Charged Radioactive Ions with TITAN at TRIUMF

Several modes of electroweak radioactive decay require an interaction between the nucleus and bound electrons within the constituent atom. Thus, the probabilities of the respective decays are not only influenced by the structure of the initial and final states in the nucleus, but can also depend strongly on the atomic charge. Conditions suitable for the partial or complete ionization of these rare isotopes occur naturally in hot, dense astrophysical environments, but can also be artificially generated in the laboratory to selectively block certain radioactive decay modes. Direct experimental studies on such scenarios are extremely difficult due to the laboratory conditions required to generate and store radioactive ions at high charge states. A new electron-beam ion trap (EBIT) decay setup with the TITAN experiment at TRIUMF has successfully demonstrated such techniques for performing spectroscopy on the radioactive decay of highly charged ions.

nucl-ex↗

arXiv2016

Spin dipole nuclear matrix elements for double beta decay nuclei by charge-exchange reactions

Spin dipole (SD) strengths for double beta-decay (DBD) nuclei were studied experimentally for the first time by using measured cross sections of (3He,t) charge exchange reactions (CERs). Then SD nuclear matrix elements (NMEs) for low-lying 2- states were derived from the experimental SD strengths by referring to the experimental GT (Gamow-Teller) and F (Fermi) strengths. They are consistent with the empirical SD NMEs based on the quasi-particle model with the empirical effective SD coupling constant. The CERs are used to evaluate the SD NME, which is associated with one of the major components of the neutrino-less DBD NME.

nucl-ex↗

arXiv2016

Search for magnetic monopoles with the MoEDAL prototype trapping detector in 8 TeV proton-proton collisions at the LHC

The MoEDAL experiment is designed to search for magnetic monopoles and other highly-ionising particles produced in high-energy collisions at the LHC. The largely passive MoEDAL detector, deployed at Interaction Point 8 on the LHC ring, relies on two dedicated direct detection techniques. The first technique is based on stacks of nuclear-track detectors with surface area $\sim$18 m$^2$, sensitive to particle ionisation exceeding a high threshold. These detectors are analysed offline by optical scanning microscopes. The second technique is based on the trapping of charged particles in an array of roughly 800 kg of aluminium samples. These samples are monitored offline for the presence of trapped magnetic charge at a remote superconducting magnetometer facility. We present here the results of a search for magnetic monopoles using a 160 kg prototype MoEDAL trapping detector exposed to 8 TeV proton-proton collisions at the LHC, for an integrated luminosity of 0.75 fb$^{-1}$. No magnetic charge exceeding $0.5g_{\rm D}$ (where $g_{\rm D}$ is the Dirac magnetic charge) is measured in any of the exposed samples, allowing limits to be placed on monopole production in the mass range 100 GeV$\leq m \leq$ 3500 GeV. Model-independent cross-section limits are presented in fiducial regions of monopole energy and direction for $1g_{\rm D}\leq|g|\leq 6g_{\rm D}$, and model-dependent cross-section limits are obtained for Drell-Yan pair production of spin-1/2 and spin-0 monopoles for $1g_{\rm D}\leq|g|\leq 4g_{\rm D}$. Under the assumption of Drell-Yan cross sections, mass limits are derived for $|g|=2g_{\rm D}$ and $|g|=3g_{\rm D}$ for the first time at the LHC, surpassing the results from previous collider experiments.

hep-ex↗

arXiv2015

A search for double-electron capture in 74Se using coincidence/anticoincidence gamma-ray spectrometry

Evaluation of single, coincidence and anticoincidence gamma-ray spectrometry methods has been carried out with the aim to search for double-electron capture in 74Se. This process is unique, because there is probability for transition to the 2+ excited state in 74Ge (1204 keV), and de-excitation through two gamma-quanta cascade with energies of 595.9 keV and 608.4 keV. Long-term measurements with anticosmic shielded HPGe spectrometer and the coincidence HPGe-NaI(Tl) spectrometer did not show any evidence for the double-electron capture in 74Se. The best limit for the half-life of the double electron capture in 74Se (both for the neutrinoless and two neutrino processes) was estimated to be >1.5x10E19 years.

nucl-ex↗

arXiv2014

Low-Background In-Trap Decay Spectroscopy with TITAN at TRIUMF

An in-trap decay spectroscopy setup has been developed and constructed for use with the TITAN facility at TRIUMF. The goal of this device is to observe weak electron-capture (EC) branching ratios for the odd-odd intermediate nuclei in the $ββ$ decay process. This apparatus consists of an up-to 6 Tesla, open-access spectroscopy ion-trap, surrounded radially by up to 7 planar Si(Li) detectors which are separated from the trap by thin Be windows. This configuration provides a significant increase in sensitivity for the detection of low-energy photons by providing backing-free ion storage and eliminating charged-particle-induced backgrounds. An intense electron beam is also employed to increase the charge-states of the trapped ions, thus providing storage times on the order of minutes, allowing for decay-spectroscopy measurements. The technique of multiple ion-bunch stacking was also recently demonstrated, which further extends the measurement possibilities of this apparatus. The current status of the facility and initial results from a $^{116}$In measurement are presented.

physics.ins-det↗

arXiv2014

The TITAN in-trap decay spectroscopy facility at TRIUMF

This article presents an upgraded in-trap decay spectroscopy apparatus which has been developed and constructed for use with TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). This device consists of an open-access electron-beam ion-trap (EBIT), which is surrounded radially by seven low-energy planar Si(Li) detectors. The environment of the EBIT allows for the detection of low-energy photons by providing backing-free storage of the radioactive ions, while guiding charged decay particles away from the trap centre via the strong (up to 6 T) magnetic field. In addition to excellent ion confinement and storage, the EBIT also provides a venue for performing decay spectroscopy on highly-charged radioactive ions. Recent technical advancements have been able to provide a significant increase in sensitivity for low-energy photon detection, towards the goal of measuring weak electron-capture branching ratios of the intermediate nuclei in the two-neutrino double beta ($2νββ$) decay process. The design, development, and commissioning of this apparatus are presented together with the main physics objectives. The future of the device and experimental technique are discussed.

physics.ins-det↗

arXiv2014

Sensitivity Increases for the TITAN Decay Spectroscopy Program

The TITAN facility at TRIUMF has recently initiated a program of performing decay spectroscopy measurements in an electron-beam ion-trap (EBIT). The unique environment of the EBIT provides backing-free storage of the radioactive ions, while guiding charged decay particles from the trap centre via the strong magnetic field. This measurement technique is able to provide a significant increase in detection sensitivity for photons which result from radioactive decay. A brief overview of this device is presented, along with methods of improving the signal-to-background ratio for photon detection by reducing Compton scattered events, and eliminating vibrational noise.

physics.ins-det↗

arXiv2014

The Physics Programme Of The MoEDAL Experiment At The LHC

The MoEDAL experiment at Point 8 of the LHC ring is the seventh and newest LHC experiment. It is dedicated to the search for highly ionizing particle avatars of physics beyond the Standard Model, extending significantly the discovery horizon of the LHC. A MoEDAL discovery would have revolutionary implications for our fundamental understanding of the Microcosm. MoEDAL is an unconventional and largely passive LHC detector comprised of the largest array of Nuclear Track Detector stacks ever deployed at an accelerator, surrounding the intersection region at Point 8 on the LHC ring. Another novel feature is the use of paramagnetic trapping volumes to capture both electrically and magnetically charged highly-ionizing particles predicted in new physics scenarios. It includes an array of TimePix pixel devices for monitoring highly-ionizing particle backgrounds. The main passive elements of the MoEDAL detector do not require a trigger system, electronic readout, or online computerized data acquisition. The aim of this paper is to give an overview of the MoEDAL physics reach, which is largely complementary to the programs of the large multi-purpose LHC detectors ATLAS and CMS.

hep-ph↗

arXiv2013

Trapped-ion decay spectroscopy towards the determination of ground-state components of double-beta decay matrix elements

A new technique has been developed at TRIUMF's TITAN facility to perform in-trap decay spectroscopy. The aim of this technique is to eventually measure weak electron capture branching ratios (ECBRs) and by this to consequently determine GT matrix elements of $ββ$ decaying nuclei. These branching ratios provide important input to the theoretical description of these decays. The feasibility and power of the technique is demonstrated by measuring the ECBR of $^{124}$Cs.

nucl-ex↗

arXiv2011

Measurement of charm production in neutrino charged-current interactions

The nuclear emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy from 1994 to 1997. In total about 100000 charged-current neutrino interactions with at least one identified muon were located in the emulsion target and fully reconstructed, using newly developed automated scanning systems. Charmed particles were searched for by a program recognizing particle decays. The observation of the decay in nuclear emulsion makes it possible to select a sample with very low background and minimal kinematical bias. 2013 charged-current interactions with a charmed hadron candidate in the final state were selected and confirmed through visual inspection. The charm production rate induced by neutrinos relative to the charged-current cross-section is measured to be sigma(nu_mu N -> mu- C X)/sigma(CC) = (5.75 +-0.32 stat +-0.30 syst)%. The charm production cross-section as a function of the neutrino energy is also obtained. The results are in good agreement with previous measurements. The charm-quark hadronization produces the following charmed hadrons with relative fractions (in %): f_Dzero = 43.7+-4.5, f_Lambda_c^plus = 19.2+-4.2, f_Dplus = 25.3+-4.2, and f_D_splus = 11.8+-4.7.

hep-ex↗

arXiv2011

The $^{150}$Nd($^3$He,$t$) and $^{150}$Sm($t$,$^3$He) reactions with applications to $ββ$ decay of $^{150}$Nd

The $^{150}$Nd($^3$He,$t$) reaction at 140 MeV/u and $^{150}$Sm($t$,$^3$He) reaction at 115 MeV/u were measured, populating excited states in $^{150}$Pm. The transitions studied populate intermediate states of importance for the (neutrinoless) $ββ$ decay of $^{150}$Nd to $^{150}$Sm. Monopole and dipole contributions to the measured excitation-energy spectra were extracted by using multipole decomposition analyses. The experimental results were compared with theoretical calculations obtained within the framework of Quasiparticle Random-Phase Approximation (QRPA), which is one of the main methods employed for estimating the half-life of the neutrinoless $ββ$ decay ($0νββ$) of $^{150}$Nd. The present results thus provide useful information on the neutrino responses for evaluating the $0νββ$ and $2νββ$ matrix elements. The $2νββ$ matrix element calculated from the Gamow-Teller transitions through the lowest $1^{+}$ state in the intermediate nucleus is maximally about half of that deduced from the half-life measured in $2νββ$ direct counting experiments and at least several transitions through $1^{+}$ intermediate states in $^{150}$Pm are required to explain the $2νββ$ half-life. Because Gamow-Teller transitions in the $^{150}$Sm($t$,$^3$He) experiment are strongly Pauli-blocked, the extraction of Gamow-Teller strengths was complicated by the excitation of the $2\hbarω$, $ΔL=0$, $ΔS=1$ isovector spin-flip giant monopole resonance (IVSGMR). However, the near absence of Gamow-Teller transition strength made it possible to cleanly identify this resonance, and the strength observed is consistent with the full exhaustion of the non-energy-weighted sum rule for the IVSGMR.

nucl-ex↗