A search for neutrino and antineutrino events correlated with 2,350 gamma-ray bursts (GRBs) is pe... more A search for neutrino and antineutrino events correlated with 2,350 gamma-ray bursts (GRBs) is performed with Borexino data collected between December 2007 and November 2015. No statistically significant excess over background is observed. We look for electron antineutrinos (ν e) that inverse beta decay on protons with energies from 1.8 MeV to 15 MeV and set the best limit on the neutrino fluence from GRBs below 8 MeV. The signals from neutrinos and antineutrinos from GRBs that scatter on electrons are also searched for, a detection channel made possible by the particularly radio-pure scintillator of Borexino. We obtain currently the best limits on the neutrino fluence of all flavors and species below 7 MeV. Finally, time correlations between GRBs and bursts of events are investigated. Our analysis combines two semi-independent data acquisition systems for the first time: the primary Borexino readout optimized for solar neutrino physics up to a few MeV, and a fast waveform digitizer system tuned for events above 1 MeV.
This paper describes the main features of the proposed low energy solar neutrino detector Borexin... more This paper describes the main features of the proposed low energy solar neutrino detector Borexino, planned to be installed at the Gran Sasso Laboratory. This real time detector is based on a massive, calorimetric, liquid scintillation spectroscopy technique, whose high luminosity is the base for the attempt to achieve a low signal detection threshold. After a description of the main
We report on the study of a new liquid scintillator target for neutrino interactions in the frame... more We report on the study of a new liquid scintillator target for neutrino interactions in the framework of the research and development program of the BOREXINO solar neutrino experiment. The scintillator consists of 1,2-dimethyl-4-(1-phenylethyl)-benzene (phenyl-o-xylylethane, PXE) as solvent and 1,4-diphenylbenzene (para-Terphenyl, p-Tp) as primary and 1,4-bis(2-methylstyryl)benzene (bis-MSB) as secondary solute. The density close to that of water and the high
Liquid noble gases are often used as scintillating material in rare event physics. Their primary ... more Liquid noble gases are often used as scintillating material in rare event physics. Their primary scintillation light emission is in the vacuum ultraviolet spectral region at about 130 and 170 nm for argon and xenon, respectively. The efficiency for converting power deposited in the material into light is very high, on the order of 30% (Ar) to 40% (Xe) [1] in gas at atmospheric pressure. These values do not change very much for the liquid phase. We have started a program in which we study the optical properties of liquid noble gases, spectrally resolved. Time resolved measurements are also performed for the various emission bands which can be identified. So far the experiments were focused on argon since it has the highest excitation energies from which energy transfer occurs to impurities, including heavier rare gases. So we avoided contamination of our gas system with xenon. Applying careful distillation techniques it is now possible to study also Ar-Xe mixtures and return to clean...
The Borexino detector at Gran Sasso has now accumulated over ten years of continuous data which r... more The Borexino detector at Gran Sasso has now accumulated over ten years of continuous data which represent a magnificent opportunity to study the cosmic muon flux at a deep underground location. We present here a precision measurement of the flux and of the expected seasonal modulation. We present the correlation with the atmospheric temperature variations from global atmospheric models. We measure the correlation parameters and infer the kaon-to-pion ratio in the production of cosmic muons from high energy primaries. We also find evidence of a long term modulation that is not present in the atmospheric data and we investigate a possible positive correlation with the solar activity. Finally we observe a seasonal modulation of the production rate of cosmogenic neutrons that is in phase with the muon modulation but shows a surprisingly larger amplitude.
Borexino is a 280-ton liquid scintillator detector located at the Laboratori Nazionali del Gran S... more Borexino is a 280-ton liquid scintillator detector located at the Laboratori Nazionali del Gran Sasso (LNGS), Italy and is one of the two detectors that has measured geoneutrinos so far. The unprecedented radio-purity of the scintillator, the shielding with highly purified water, and the placement of the detector at a 3800 m w.e. depth have resulted in very low background levels and has made Borexino an excellent apparatus for geoneutrino measurements. The new update of the Borexino geoneutrino measurement, using the data obtained from December 2007 to April 2019, has been presented. Enhanced analysis techniques, adopted in this measurement, have been also presented (poster presentation #39 by S. Kumaran). The updated statistics and the new elaborate analysis have led to more than a factor two increase in exposure ((1.12 ± 0.05) × 1032 protons × yr) when compared to the latest Borexino result from 2015. The resulting geoneutrino signal of 47.0 − 7.7 + 8.4 ( stat ) − 1.9 + 2.4 ( sys ...
We report an improved geo-neutrino measurement with Borexino from 2056 days of data taking. The p... more We report an improved geo-neutrino measurement with Borexino from 2056 days of data taking. The present exposure is (5.5 ± 0.3) × 10 31 proton×yr. Assuming a chondritic Th/U mass ratio of 3.9, we obtain 23.7 +6.5 −5.7 (stat) +0.9 −0.6 (sys) geo-neutrino events. The null observation of geo-neutrinos with Borexino alone has a probability of 3.6 × 10 −9 (5.9σ). A geo-neutrino signal from the mantle is obtained at 98% C.L. The radiogenic heat production for U and Th from the present best-fit result is restricted to the range 23-36 TW, taking into account the uncertainty on the distribution of heat producing elements inside the Earth.
Vacuum ultraviolet light emission from xenon-doped liquid argon is described in the context of li... more Vacuum ultraviolet light emission from xenon-doped liquid argon is described in the context of liquid noble gas particle detectors. Xenon concentrations in liquid argon from 0.1 ppm to 1000 ppm were studied. The energy transfer from the second excimer continuum of argon (∼ 127 nm) to the second excimer continuum of xenon (∼ 174 nm) is observed by recording optical emission spectra. The transfer almost saturates at a xenon concentration of ∼10 ppm for which, in addition, an intense emission in the infrared at a peak wavelength of 1.17 µm with 13000 ± 4000 photons per MeV deposited by electrons had been found. The corresponding value for the VUV emission at a peak wavelength of 174 nm (second excimer continuum of xenon) is determined to be 20000±6000 photons per MeV electron energy deposited. Under these excitation conditions pure liquid argon emits 22000 ± 3000 photons per MeV electron energy deposited at a peak wavelength of 127 nm. An electron-beam induced emission spectrum for the 10 ppm Ar-Xe liquid mixture ranging from 115 nm to 3.5 µm is presented. VUV emission spectra from xenon-doped liquid argon with exponentially varied xenon concentrations from 0.1 ppm to 1000 ppm are also shown. Time structure measurements of the light emissions at well-defined wavelength positions in the vacuum ultraviolet as well as in the near-infrared are presented.
A next-generation liquid-scintillator detector will be able to perform high-statistics measuremen... more A next-generation liquid-scintillator detector will be able to perform high-statistics measurements of the solar neutrino flux. In LENA, solar 7 Be neutrinos are expected to cause 1.7×10 4 electron recoil events per day in a fiducial volume of 35 kilotons. Based on this signal, a search for periodic modulations on sub-percent level can be conducted, surpassing the sensitivity of current detectors by at least a factor of 20. The range of accessible periods reaches from several minutes, corresponding to modulations induced by helioseismic g-modes, to tens of years, allowing to study long-term changes in solar fusion rates.
We have studied the α-decays of 214 Po into 210 Pb and of 212 Po into 208 Pb tagged by the coinci... more We have studied the α-decays of 214 Po into 210 Pb and of 212 Po into 208 Pb tagged by the coincidence with the preceding β-decays from 214 Bi and 212 Bi, respectively. The 222 Rn, 232 Th, and 220 Rn sources used were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of 214 Po is (236.00 ± 0.42(stat) ± 0.15(syst)) μs and that of 212 Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results, obtained from data with signal-to-background ratio larger than 1000, reduce the overall uncertainties and are compatible with previous measurements.
A search for neutrino and antineutrino events correlated with 2,350 gamma-ray bursts (GRBs) is pe... more A search for neutrino and antineutrino events correlated with 2,350 gamma-ray bursts (GRBs) is performed with Borexino data collected between December 2007 and November 2015. No statistically significant excess over background is observed. We look for electron antineutrinos (ν e) that inverse beta decay on protons with energies from 1.8 MeV to 15 MeV and set the best limit on the neutrino fluence from GRBs below 8 MeV. The signals from neutrinos and antineutrinos from GRBs that scatter on electrons are also searched for, a detection channel made possible by the particularly radio-pure scintillator of Borexino. We obtain currently the best limits on the neutrino fluence of all flavors and species below 7 MeV. Finally, time correlations between GRBs and bursts of events are investigated. Our analysis combines two semi-independent data acquisition systems for the first time: the primary Borexino readout optimized for solar neutrino physics up to a few MeV, and a fast waveform digitizer system tuned for events above 1 MeV.
This paper describes the main features of the proposed low energy solar neutrino detector Borexin... more This paper describes the main features of the proposed low energy solar neutrino detector Borexino, planned to be installed at the Gran Sasso Laboratory. This real time detector is based on a massive, calorimetric, liquid scintillation spectroscopy technique, whose high luminosity is the base for the attempt to achieve a low signal detection threshold. After a description of the main
We report on the study of a new liquid scintillator target for neutrino interactions in the frame... more We report on the study of a new liquid scintillator target for neutrino interactions in the framework of the research and development program of the BOREXINO solar neutrino experiment. The scintillator consists of 1,2-dimethyl-4-(1-phenylethyl)-benzene (phenyl-o-xylylethane, PXE) as solvent and 1,4-diphenylbenzene (para-Terphenyl, p-Tp) as primary and 1,4-bis(2-methylstyryl)benzene (bis-MSB) as secondary solute. The density close to that of water and the high
Liquid noble gases are often used as scintillating material in rare event physics. Their primary ... more Liquid noble gases are often used as scintillating material in rare event physics. Their primary scintillation light emission is in the vacuum ultraviolet spectral region at about 130 and 170 nm for argon and xenon, respectively. The efficiency for converting power deposited in the material into light is very high, on the order of 30% (Ar) to 40% (Xe) [1] in gas at atmospheric pressure. These values do not change very much for the liquid phase. We have started a program in which we study the optical properties of liquid noble gases, spectrally resolved. Time resolved measurements are also performed for the various emission bands which can be identified. So far the experiments were focused on argon since it has the highest excitation energies from which energy transfer occurs to impurities, including heavier rare gases. So we avoided contamination of our gas system with xenon. Applying careful distillation techniques it is now possible to study also Ar-Xe mixtures and return to clean...
The Borexino detector at Gran Sasso has now accumulated over ten years of continuous data which r... more The Borexino detector at Gran Sasso has now accumulated over ten years of continuous data which represent a magnificent opportunity to study the cosmic muon flux at a deep underground location. We present here a precision measurement of the flux and of the expected seasonal modulation. We present the correlation with the atmospheric temperature variations from global atmospheric models. We measure the correlation parameters and infer the kaon-to-pion ratio in the production of cosmic muons from high energy primaries. We also find evidence of a long term modulation that is not present in the atmospheric data and we investigate a possible positive correlation with the solar activity. Finally we observe a seasonal modulation of the production rate of cosmogenic neutrons that is in phase with the muon modulation but shows a surprisingly larger amplitude.
Borexino is a 280-ton liquid scintillator detector located at the Laboratori Nazionali del Gran S... more Borexino is a 280-ton liquid scintillator detector located at the Laboratori Nazionali del Gran Sasso (LNGS), Italy and is one of the two detectors that has measured geoneutrinos so far. The unprecedented radio-purity of the scintillator, the shielding with highly purified water, and the placement of the detector at a 3800 m w.e. depth have resulted in very low background levels and has made Borexino an excellent apparatus for geoneutrino measurements. The new update of the Borexino geoneutrino measurement, using the data obtained from December 2007 to April 2019, has been presented. Enhanced analysis techniques, adopted in this measurement, have been also presented (poster presentation #39 by S. Kumaran). The updated statistics and the new elaborate analysis have led to more than a factor two increase in exposure ((1.12 ± 0.05) × 1032 protons × yr) when compared to the latest Borexino result from 2015. The resulting geoneutrino signal of 47.0 − 7.7 + 8.4 ( stat ) − 1.9 + 2.4 ( sys ...
We report an improved geo-neutrino measurement with Borexino from 2056 days of data taking. The p... more We report an improved geo-neutrino measurement with Borexino from 2056 days of data taking. The present exposure is (5.5 ± 0.3) × 10 31 proton×yr. Assuming a chondritic Th/U mass ratio of 3.9, we obtain 23.7 +6.5 −5.7 (stat) +0.9 −0.6 (sys) geo-neutrino events. The null observation of geo-neutrinos with Borexino alone has a probability of 3.6 × 10 −9 (5.9σ). A geo-neutrino signal from the mantle is obtained at 98% C.L. The radiogenic heat production for U and Th from the present best-fit result is restricted to the range 23-36 TW, taking into account the uncertainty on the distribution of heat producing elements inside the Earth.
Vacuum ultraviolet light emission from xenon-doped liquid argon is described in the context of li... more Vacuum ultraviolet light emission from xenon-doped liquid argon is described in the context of liquid noble gas particle detectors. Xenon concentrations in liquid argon from 0.1 ppm to 1000 ppm were studied. The energy transfer from the second excimer continuum of argon (∼ 127 nm) to the second excimer continuum of xenon (∼ 174 nm) is observed by recording optical emission spectra. The transfer almost saturates at a xenon concentration of ∼10 ppm for which, in addition, an intense emission in the infrared at a peak wavelength of 1.17 µm with 13000 ± 4000 photons per MeV deposited by electrons had been found. The corresponding value for the VUV emission at a peak wavelength of 174 nm (second excimer continuum of xenon) is determined to be 20000±6000 photons per MeV electron energy deposited. Under these excitation conditions pure liquid argon emits 22000 ± 3000 photons per MeV electron energy deposited at a peak wavelength of 127 nm. An electron-beam induced emission spectrum for the 10 ppm Ar-Xe liquid mixture ranging from 115 nm to 3.5 µm is presented. VUV emission spectra from xenon-doped liquid argon with exponentially varied xenon concentrations from 0.1 ppm to 1000 ppm are also shown. Time structure measurements of the light emissions at well-defined wavelength positions in the vacuum ultraviolet as well as in the near-infrared are presented.
A next-generation liquid-scintillator detector will be able to perform high-statistics measuremen... more A next-generation liquid-scintillator detector will be able to perform high-statistics measurements of the solar neutrino flux. In LENA, solar 7 Be neutrinos are expected to cause 1.7×10 4 electron recoil events per day in a fiducial volume of 35 kilotons. Based on this signal, a search for periodic modulations on sub-percent level can be conducted, surpassing the sensitivity of current detectors by at least a factor of 20. The range of accessible periods reaches from several minutes, corresponding to modulations induced by helioseismic g-modes, to tens of years, allowing to study long-term changes in solar fusion rates.
We have studied the α-decays of 214 Po into 210 Pb and of 212 Po into 208 Pb tagged by the coinci... more We have studied the α-decays of 214 Po into 210 Pb and of 212 Po into 208 Pb tagged by the coincidence with the preceding β-decays from 214 Bi and 212 Bi, respectively. The 222 Rn, 232 Th, and 220 Rn sources used were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of 214 Po is (236.00 ± 0.42(stat) ± 0.15(syst)) μs and that of 212 Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results, obtained from data with signal-to-background ratio larger than 1000, reduce the overall uncertainties and are compatible with previous measurements.
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Papers by L. Oberauer