arXiv subjects

M. Laubenstein

Publications and source records attributed to M. Laubenstein.

At least 73 records · Page 4Linked to original sources

arXiv2020

Comprehensive geoneutrino analysis with Borexino

This paper presents a geoneutrino measurement using 3262.74 days of data taken with the Borexino detector at LNGS in Italy. By observing $52.6 ^{+9.4}_{-8.6} ({\rm stat}) ^{+2.7}_{-2.1}({\rm sys})$ geoneutrinos (68% interval) from $^{238}$U and $^{232}$Th, a signal of $47.0^{+8.4}_{-7.7}\,({\rm stat)}^{+2.4}_{-1.9}\,({\rm sys})$ TNU with $^{+18.3}_{-17.2}$% total precision was obtained. This result assumes the same Th/U mass ratio found in chondritic CI meteorites but compatible results were found when contributions from $^{238}$U and $^{232}$Th were fit as free parameters. Antineutrino background from reactors is fit unconstrained and found compatible with the expectations. The null-hypothesis of observing a signal from the mantle is excluded at a 99.0% C.L. when exploiting the knowledge of the local crust. Measured mantle signal of $21.2 ^{+9.6}_{-9.0} ({\rm stat})^{+1.1}_{-0.9} ({\rm sys})$ TNU corresponds to the production of a radiogenic heat of $24.6 ^{+11.1}_{-10.4}$ TW (68% interval) from $^{238}$U and $^{232}$Th in the mantle. Assuming 18% contribution of $^{40}$K in the mantle and $8.1^{+1.9}_{-1.4}$ TW of radiogenic heat of the lithosphere, the Borexino estimate of the total Earth radiogenic heat is $38.2 ^{+13.6}_{-12.7}$ TW, corresponding to a convective Urey ratio of 0.78$^{+0.41}_{-0.28}$. These values are compatible with different geological models, however there is a 2.4$σ$ tension with those which predict the lowest concentration of heat-producing elements. By fitting the data with a constraint on the reactor antineutrino background, the existence of a hypothetical georeactor at the center of the Earth having power greater than 2.4 TW at 95% C.L. is excluded. Particular attention is given to all analysis details, which should be of interest for the next generation geoneutrino measurements.

hep-ex↗

arXiv2020

Constraints on Flavor-Diagonal Non-Standard Neutrino Interactions from Borexino Phase-II

The Borexino detector measures solar neutrino fluxes via neutrino-electron elastic scattering. Observed spectra are determined by the solar-$ν_{e}$ survival probability $P_{ee}(E)$, and the chiral couplings of the neutrino and electron. Some theories of physics beyond the Standard Model postulate the existence of Non-Standard Interactions (NSI's) which modify the chiral couplings and $P_{ee}(E)$. In this paper, we search for such NSI's, in particular, flavor-diagonal neutral current interactions that modify the $ν_e e$ and $ν_τe$ couplings using Borexino Phase II data. Standard Solar Model predictions of the solar neutrino fluxes for both high- and low-metallicity assumptions are considered. No indication of new physics is found at the level of sensitivity of the detector and constraints on the parameters of the NSI's are placed. In addition, with the same dataset the value of $\sin^2θ_W$ is obtained with a precision comparable to that achieved in reactor antineutrino experiments.

hep-ph↗

arXiv2019

Simultaneous Precision Spectroscopy of $pp$, $^7$Be, and $pep$ Solar Neutrinos with Borexino Phase-II

We present the first simultaneous measurement of the interaction rates of $pp$, $^7$Be, and $pep$ solar neutrinos performed with a global fit to the Borexino data in an extended energy range (0.19-2.93)$\,$MeV. This result was obtained by analyzing 1291.51$\,$days of Borexino Phase-II data, collected between December 2011 and May 2016 after an extensive scintillator purification campaign. We find: rate($pp$)$\,$=$\,$$134$$\,$$\pm$$\,$$10$$\,$($stat$)$\,$$^{\rm +6}_{\rm -10}$$\,$($sys$)$\,$cpd/100$\,$t, rate($^7$Be)$\,$=$\,$$48.3$$\,$$\pm$$\,$$1.1$$\,$($stat$)$\,$$^{\rm +0.4}_{\rm -0.7}$$\,$($sys$)$\,$cpd/100$\,$t, and rate($pep$)$\,$=$\,$$2.43$$\pm$$\,$$0.36$$\,$($stat$)$^{+0.15}_{-0.22}$$\,$($sys$)$\,$cpd/100$\,$t. These numbers are in agreement with and improve the precision of our previous measurements. In particular, the interaction rate of $^7$Be $ν$'s is measured with an unprecedented precision of 2.7%, showing that discriminating between the high and low metallicity solar models is now largely dominated by theoretical uncertainties. The absence of $pep$ neutrinos is rejected for the first time at more than 5$\,$$σ$. An upper limit of $8.1$$\,$cpd/100$\,$t (95%$\,$C.L.) on the CNO neutrino rate is obtained by setting an additional constraint on the ratio between the $pp$ and $pep$ neutrino rates in the fit. This limit has the same significance as that obtained by the Borexino Phase-I (currently providing the tightest bound on this component), but is obtained by applying a less stringent constraint on the $pep$ $ν$ flux.

hep-ex↗

arXiv2019

First direct search for $2ε$ and $εβ^+$ decay of $^{144}$Sm and $2β^-$ decay of $^{154}$Sm

The first direct search for the double electron capture ($2ε$) and the electron capture with positron emission ($εβ^+$) in $^{144}$Sm to the ground state and to the excited levels of $^{144}$Nd was realized by measuring - over 1899 h - a 342 g sample of highly purified samarium oxide (Sm$_2$O$_3$) with the ultra-low background HP-Ge $γ$ spectrometer GeCris (465 cm$^3$) at the STELLA facility of the Gran Sasso National Laboratory (LNGS). No effect was observed and half-life limits were estimated at the level of $T_{1/2} \sim (0.1-1.3) \times 10^{20}$ yr (90% C.L.). Moreover, for the first time half-life limits of the double beta ($2β^-$) decay of $^{154}$Sm to several excited levels of $^{154}$Gd have been set; they are at the level of $T_{1/2} \sim (0.06-8) \times 10^{20}$ yr (90% C.L.).

nucl-ex↗

arXiv2019

Probing Majorana neutrinos with double-$β$ decay

A discovery that neutrinos are not the usual Dirac but Majorana fermions, i.e. identical to their antiparticles, would be a manifestation of new physics with profound implications for particle physics and cosmology. Majorana neutrinos would generate neutrinoless double-$β$ ($0νββ$) decay, a matter-creating process without the balancing emission of antimatter. So far, 0$νββ$ decay has eluded detection. The GERDA collaboration searches for the $0νββ$ decay of $^{76}$Ge by operating bare germanium detectors in an active liquid argon shield. With a total exposure of 82.4 kg$\cdot$yr, we observe no signal and derive a lower half-life limit of T$_{1/2}$ > 0.9$\cdot$10$^{26}$ yr (90% C.L.). Our T$_{1/2}$ sensitivity assuming no signal is 1.1$\cdot$10$^{26}$ yr. Combining the latter with those from other $0νββ$ decay searches yields a sensitivity to the effective Majorana neutrino mass of 0.07 - 0.16 eV, with corresponding sensitivities to the absolute mass scale in $β$ decay of 0.15 - 0.44 eV, and to the cosmological relevant sum of neutrino masses of 0.46 - 1.3 eV.

hep-ex↗

arXiv2019

Search for low-energy neutrinos from astrophysical sources with Borexino

We report on searches for neutrinos and antineutrinos from astrophysical sources performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso in Italy. Electron antineutrinos ($\barν_e$) are detected in an organic liquid scintillator through the inverse $β$-decay reaction. In the present work we set model-independent upper limits in the energy range 1.8-16.8 MeV on neutrino fluxes from unknown sources that improve our previous results, on average, by a factor 2.5. Using the same data set, we first obtain experimental constraints on the diffuse supernova $\barν_e$ fluxes in the previously unexplored region below 8 MeV. A search for $\barν_e$ in the solar neutrino flux is also presented: the presence of $\barν_e$ would be a manifestation of a non-zero anomalous magnetic moment of the neutrino, making possible its conversion to antineutrinos in the strong magnetic field of the Sun. We obtain a limit for a solar $\barν_e$ flux of 384 cm$^{-2}$s$^{-1}$ (90% C.L.), assuming an undistorted solar $^{8}$B neutrinos energy spectrum, that corresponds to a transition probability $p_{ ν_e \rightarrow \barν_{e}}<$ 7.2$\times$10$^{-5}$ (90% C.L.) for E$_{\bar ν_e}$ $>$ 1.8 MeV. At lower energies, by investigating the spectral shape of elastic scattering events, we obtain a new limit on solar $^{7}$Be-$ν_e$ conversion into $\barν_e$ of $p_{ ν_e \rightarrow \bar ν_{e}}<$ 0.14 (90% C.L.) at 0.862 keV. Last, we investigate solar flares as possible neutrino sources and obtain the strongest up-to-date limits on the fluence of neutrinos of all flavor neutrino below 3-7 ,MeV. Assuming the neutrino flux to be proportional to the flare's intensity, we exclude an intense solar flare as the cause of the observed excess of events in run 117 of the Cl-Ar Homestake experiment.

hep-ex↗

arXiv2019

First search for 2$\varepsilon$ and $\varepsilonβ^+$ processes in $^{168}$Yb

The double-electron capture and the electron capture with positron emission in $^{168}$Yb have been investigated for the first time at the STELLA facility of the Gran Sasso underground laboratory (Italy) measuring 371 g of highly purified ytterbium oxide placed on the end-cap of a 465 cm$^3$ ultra-low-background high purity Germanium detector (HPGe). No gamma associated to double beta processes in $^{168}$Yb have been observed after 2074 h of data taking. This has allowed setting the half-life limits on the level of $\lim T_{1/2}\sim$ $10^{14}-10^{18}$ yr at 90\% C.L. Particularly, a lower half-life limit on a possible resonant neutrinoless double-electron capture in $^{168}$Yb to the $(2)^-$ 1403.7 keV excited state of $^{168}$Er is set as $T_{1/2}\geq1.9\times 10^{18}$ yr at 90\% C.L. Half-life limits $T_{1/2}^{2ν(0ν)}\geq 4.5(4.3)\times10^{16}$ yr were set on the $2ν(0ν)2β^-$ decay of $^{176}$Yb to the $2^+$ 84.3 keV first excited level of $^{176}$Hf.

nucl-ex↗

arXiv2019

A Test of Bolometric Properties of Tm-containing Crystals as a Perspective Detector for the Solar Axion Search

The $^{169}$Tm nuclide has first nuclear level at 8.41 keV with magnetic type transition to the ground state and, therefore, can be used as a target nucleus for the search of resonant absorption of solar axions. We plan to use a Tm-containing crystal of a garnet family Tm$_3$Al$_5$O$_{12}$ as a bolometric detector in order to search for the excitation of the first nuclear level of $^{169}$Tm via the resonant absorption of solar axions. With this perspective in mind, a sample of the Tm$_3$Al$_5$O$_{12}$ crystal was grown and tested for its bolometric and optical properties. Measurements of chemical and/or radioactive contaminations were performed as well. In this paper we present the test results and estimate the requirements for a future low-background experimental setup.

physics.ins-det↗

arXiv2019

VIP2 in LNGS - Testing the Pauli Exclusion Principle for electrons with high sensitivity

The VIP2 (VIolation of the Pauli Exclusion Principle) experiment at the Gran Sasso underground laboratory (LNGS) is searching for possible violations of standard quantum mechanics predictions in atoms at very high sensitivity. We investigate atomic transitions with precision X-ray spectroscopy in order to test the Pauli Exclusion Principle (PEP) and therefore the related spin-statistics theorem. We will present our experimental method for the search for "anomalous" (i.e. Pauli-forbidden) X-ray transitions in copper atoms, produced by "new" electrons, which could have tiny probability to undergo Pauli-forbidden transition to the ground state already occupied by two electrons. We will describe the VIP2 experimental setup, which is taking data at LNGS presently. The goal of VIP2 is to test the PEP for electrons with unprecedented accuracy, down to a limit in the probability that PEP is violated at the level of 10$^{-31}$. We will present current experimental results and discuss implications of a possible violation.

quant-ph↗

arXiv2019

Modulations of the Cosmic Muon Signal in Ten Years of Borexino Data

We have measured the flux of cosmic muons in the Laboratori Nazionali del Gran Sasso at 3800\,m\,w.e. to be $(3.432 \pm 0.003)\cdot 10^{-4}\,\mathrm{{m^{-2}s^{-1}}}$ based on ten years of Borexino data acquired between May 2007 and May 2017. A seasonal modulation with a period of $(366.3 \pm 0.6)\,\mathrm{d}$ and a relative amplitude of $(1.36 \pm0.04)\%$ is observed. The phase is measured to be $(181.7 \pm 0.4)\,\mathrm{d}$, corresponding to a maximum at the 1$^\mathrm{st}$ of July. Using data inferred from global atmospheric models, we show the muon flux to be positively correlated with the atmospheric temperature and measure the effective temperature coefficient $α_\mathrm{T} = 0.90 \pm 0.02$. The origin of cosmic muons from pion and kaon decays in the atmosphere allows to interpret the effective temperature coefficient as an indirect measurement of the atmospheric kaon-to-pion production ratio $r_{\mathrm{K}/π} = 0.11^{+0.11}_{-0.07}$ for primary energies above $18\,\mathrm{TeV}$. We find evidence for a long-term modulation of the muon flux with a period of $\sim 3000\,\mathrm{d}$ and a maximum in June 2012 that is not present in the atmospheric temperature data. A possible correlation between this modulation and the solar activity is investigated. The cosmogenic neutron production rate is found to show a seasonal modulation in phase with the cosmic muon flux but with an increased amplitude of $(2.6 \pm 0.4)\%$.

hep-ex↗

arXiv2019

Characterization of 30 $^{76}$Ge enriched Broad Energy Ge detectors for GERDA Phase II

The GERmanium Detector Array (GERDA) is a low background experiment located at the Laboratori Nazionali del Gran Sasso in Italy, which searches for neutrinoless double beta decay of $^{76}$Ge into $^{76}$Se+2e$^-$. GERDA has been conceived in two phases. Phase II, which started in December 2015, features several novelties including 30 new Ge detectors. These were manufactured according to the Broad Energy Germanium (BEGe) detector design that has a better background discrimination capability and energy resolution compared to formerly widely-used types. Prior to their installation, the new BEGe detectors were mounted in vacuum cryostats and characterized in detail in the HADES underground laboratory in Belgium. This paper describes the properties and the overall performance of these detectors during operation in vacuum. The characterization campaign provided not only direct input for GERDA Phase II data collection and analyses, but also allowed to study detector phenomena, detector correlations as well as to test the strength of pulse shape simulation codes.

physics.ins-det↗

arXiv2018

A new investigation of half-lives for the decay modes of $^{50}$V

A new search for the decay modes of the 4-fold forbidden non-unique decay of $^{50}$V has been performed at the Gran Sasso Underground Laboratory (LNGS). In total an exposure of 197 kg $\times$ d has been accumulated. The half-life for the electron capture into the first excited state of $^{50}$Ti has been measured with the highest precision to date as $2.67_{-0.18}^{+0.16} \times 10^{17}$ yr (68% C.I.) in which systematics uncertainties dominate. The search for the $β$-decay into the first excited state of $^{50}$Cr resulted in a lower limit of ${1.9} \times 10^{19}$ yr (90% C.I.), which is an improvement of almost one order of magnitude compared to existing results. The sensitivity of the new measurement is now in the region of theoretical predictions.

nucl-ex↗

arXiv2018

Final results of the Aurora experiment to study 2$β$ decay of $^{116}$Cd with enriched $^{116}$CdWO$_4$ crystal scintillators

The double-beta decay of $^{116}$Cd has been investigated with the help of radiopure enriched $^{116}$CdWO$_4$ crystal scintillators (mass of 1.162 kg) at the Gran Sasso underground laboratory. The half-life of $^{116}$Cd relatively to the $2\nu2β$ decay to the ground state of $^{116}$Sn was measured with the highest up-to-date accuracy as $T_{1/2}=(2.63^{+0.11}_{-0.12})\times10^{19}$ yr. A new improved limit on the 0$ν$2$β$ decay of $^{116}$Cd to the ground state of $^{116}$Sn was set as $T_{1/2}\geq 2.2 \times 10^{23}$ yr at 90\% C.L., which is the most stringent known restriction for this isotope. It corresponds to the effective Majorana neutrino mass limit in the range $\langle m_ν\rangle\le(1.0-1.7)$ eV, depending on the nuclear matrix elements used in the estimations. New improved half-life limits for the 0$ν$2$β$ decay with majoron(s) emission, Lorentz-violating $2\nu2β$ decay and $2β$ transitions to excited states of $^{116}$Sn were set at the level of $T_{1/2}\geq 10^{20}-10^{22}$ yr. New limits for the hypothetical lepton-number violating parameters (right-handed currents admixtures in weak interaction, the effective majoron-neutrino coupling constants, R-parity violating parameter, Lorentz-violating parameter, heavy neutrino mass) were set.

nucl-ex↗

arXiv2018

Double beta decay of $^{150}$Nd to the first excited $0^+$ level of $^{150}$Sm: preliminary results

The double beta decay of $^{150}$Nd to the first excited 0$^+$ level of $^{150}$Sm ($E_{exc}$ = 740.5 keV) has been investigated with the help of the ultra-low-background setup consisting of four HP Ge (high-purity germanium) detectors (${\approx}$ 225 cm$^3$ volume each one) at the Gran Sasso underground laboratory of INFN (Italy). A highly purified 2.381-kg sample of neodymium oxide (Nd$_2$O$_3$) was used as a source of $γ$ quanta expected in the decays. Gamma quanta with energies 334.0 keV and 406.5 keV emitted after deexcitation of the $0_1^+$ 740.5 keV level of $^{150}$Sm are observed in the coincidence spectra accumulated over 16375 h. The half-life relatively to the two neutrino double beta decay $^{150}$Nd $\rightarrow$ $^{150}$Sm(0$_1^+$) is measured as $T_{1/2} = [4.7_{-1.9}^{+4.1}\text{(stat)} {\pm} 0.5\text{(syst)}] {\times} 10^{19} y$, in agreement with results of previous experiments.

nucl-ex↗

arXiv2018

First search for $2\varepsilon$ and $\varepsilonβ^+$ decay of $^{162}$Er and new limit on $2β^{-}$ decay of $^{170}$Er to the first excited level of $^{170}$Yb

The first search for double electron capture ($2\varepsilon$) and electron capture with positron emission ($\varepsilonβ^+$) of $^{162}$Er to the ground state and to several excited levels of $^{162}$Dy was realized with 326 g of highly purified erbium oxide. The sample was measured over 1934 h by the ultra-low background HP Ge $γ$ spectrometer GeCris (465 cm$^3$) at the Gran Sasso underground laboratory. No effect was observed, the half-life limits were estimated at the level of $\lim T_{1/2}\sim 10^{15}-10^{18}$ yr. A possible resonant $0νKL_1$ capture in $^{162}$Er to the $2^+$ 1782.7 keV excited state of $^{162}$Dy is restricted as $T_{1/2}\geq5.0\times 10^{17}$ yr at 90% C.L. A new improved half-life limit $T_{1/2}\geq4.1\times 10^{17}$ yr was set on the $2β^-$ decay of $^{170}$Er to the $2^+$ 84.3 keV first excited state of $^{170}$Yb.

nucl-ex↗

arXiv2018

Detector setup of the VIP2 Underground Experiment at LNGS

The VIP2 experiment tests the Pauli Exclusion Principle with high sensitivity, by searching for Pauli-forbidden atomic transitions from the 2p to the 1s shell in copper at about 8keV. The transition energy of Pauli-forbidden K X-rays is shifted by about 300 eV with respect to the normal allowed K line. This energy difference can be resolved using Silicon Drift Detectors. The data for this experiment is taken in the Gran Sasso underground laboratory (LNGS), which provides shielding from cosmic radiation. An overview of the detection system of the VIP2 experiment will be given. This includes the Silicon Drift Detectors used as X-ray detectors which provide an energy resolution of around 150 eV at 6 keV and timing information for active shielding. Furthermore, the low maintenance requirement makes them excellent X-ray detectors for the use in an underground laboratory. The VIP2 setup will be discussed which consists of a high current target system and a passive as well as an active shielding system using plastic scintillators read out by Silicon Photomultipliers.

physics.ins-det↗

arXiv2018

Speeding up complex multivariate data analysis in Borexino with parallel computing based on Graphics Processing Unit

A spectral fitter based on the graphics processor unit (GPU) has been developed for Borexino solar neutrino analysis. It is able to shorten the fitting time to a superior level compared to the CPU fitting procedure. In Borexino solar neutrino spectral analysis, fitting usually requires around one hour to converge since it includes time-consuming convolutions in order to account for the detector response and pile-up effects. Moreover, the convergence time increases to more than two days when including extra computations for the discrimination of $^{11}$C and external $γ$s. In sharp contrast, with the GPU-based fitter it takes less than 10 seconds and less than four minutes, respectively. This fitter is developed utilizing the GooFit project with customized likelihoods, pdfs and infrastructures supporting certain analysis methods. In this proceeding the design of the package, developed features and the comparison with the original CPU fitter are presented.

physics.data-an↗

arXiv2018

Experimental search for the violation of Pauli Exclusion Principle

The VIolation of Pauli exclusion principle -2 experiment, or VIP-2 experiment, at the Laboratori Nazionali del Gran Sasso searches for x-rays from copper atomic transition that are prohibited by the Pauli Exclusion Principle. Candidate direct violation events come from the transition of a $2p$ electron to the ground state that is already occupied by two electrons. From the first data taking campaign in 2016 of VIP-2 experiment, we determined a best upper limit of 3.4 $\times$ 10$^{-29}$ for the probability that such a violation exists. Significant improvement in the control of the experimental systematics was also achieved, although not explicitly reflected in the improved upper limit. By introducing a simultaneous spectral fit of the signal and background data in the analysis, we succeeded in taking into account systematic errors that could not be evaluated previously in this type of measurements.

physics.atom-ph↗