Positronium signature in organic liquid scintillators for neutrino experiments

Franco, D.; Consolati, G.; Trezzi, D.

doi:10.1103/physrevc.83.015504

Cited by 49 publications

(53 citation statements)

References 24 publications

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“…43. The fitted ortho-positronium formation probability of 53% is compatible with other laboratory measurements [61].…”

Section: Xv2 βsupporting

confidence: 88%

“…In liquid scintillator, however, the life-time of ortho-positronium is reduced because of interactions with the surrounding medium: processes like spin-flip, or pick-off annihilation on collision with an anti-parallel spin bulk electron, lead to the two-body decay within few ns. Laboratory measurements lead to ∼3 ns mean-life and ∼50% ortho-positronium formation probability [61] in scintillators. This delay of the annihilation introduced by the ortho-positronium formation is comparable in size to the fast scintillation time constant τ 1 (see Table III), and therefore is expected to introduce a measurable distortion in the time distribution of hit PMTs with respect to a pure β − event of the same reconstructed energy.…”

Section: Xv2 βmentioning

confidence: 99%

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Final results of Borexino Phase-I on low-energy solar neutrino spectroscopy

Bellini¹,

Benziger²,

Bick³

et al. 2014

Phys. Rev. D

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286

345

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Borexino has been running since May 2007 at the LNGS laboratory in Italy with the primary goal of detecting solar neutrinos. The detector, a large, unsegmented liquid scintillator calorimeter characterized by unprecedented low levels of intrinsic radioactivity, is optimized for the study of the lower energy part of the spectrum. During the Phase-I (2007Phase-I ( -2010), Borexino first detected and then precisely measured the flux of the 7 Be solar neutrinos, ruled out any significant day-night asymmetry of their interaction rate, made the first direct observation of the pep neutrinos, and set the tightest upper limit on the flux of CNO solar neutrinos. In this paper we discuss the signal signature and provide a comprehensive description of the backgrounds, quantify their event rates, describe the methods for their identification, selection or subtraction, and describe data analysis. Key features are an extensive in situ calibration program using radioactive sources, the detailed modeling of the detector response, the ability to define an innermost fiducial volume with extremely low background via software cuts, and the excellent pulse-shape discrimination capability of the scintillator that allows particle identification. We report a measurement of the annual modulation of the 7 Be neutrino interaction rate. The period, the amplitude, and the phase of the observed modulation are consistent with the solar origin of these events, and the absence of their annual modulation is rejected with higher than 99% C.L. The physics implications of Phase-I results in the context of the neutrino oscillation physics and solar models are presented.

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“…43. The fitted ortho-positronium formation probability of 53% is compatible with other laboratory measurements [61].…”

Section: Xv2 βsupporting

confidence: 88%

Section: Xv2 βmentioning

confidence: 99%

Final results of Borexino Phase-I on low-energy solar neutrino spectroscopy

Bellini¹,

Benziger²,

Bick³

et al. 2014

Phys. Rev. D

Self Cite

286

345

View full text Add to dashboard Cite

show abstract

“…A coincidence in time and space of an electron/positron signal with a neutron capture gammaray allows the identification of that signal as a positron. In addition, experiments have shown that scintillation detectors are able to differentiate electrons and positrons through pulse shape discrimination (Kino et al 2000;Franco et al 2011), which allows for further differentiation between electronscattering and ē n absorption events. Pulse shape discrimination has been demonstrated in active scintillation detectors (Abe et al 2014;Bellini et al 2014), and we anticipate its continued use in future scintillation detectors.…”

Section: Scintillation Detectorsmentioning

confidence: 99%

Detecting the Supernova Breakout Burst in Terrestrial Neutrino Detectors

Wallace

Burrows

Dolence

2016

ApJ

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We calculate the distance-dependent performance of a few representative terrestrial neutrino detectors in detecting and measuring the properties of the ν e breakout burst light curve in a Galactic core-collapse supernova. The breakout burst is a signature phenomenon of core collapse and offers a probe into the stellar core through collapse and bounce. We examine cases of no neutrino oscillations and oscillations due to normal and inverted neutrinomass hierarchies. For the normal hierarchy, other neutrino flavors emitted by the supernova overwhelm the ν e signal, making a detection of the breakout burst difficult. For the inverted hierarchy (IH), some detectors at some distances should be able to see the ν e breakout burst peak and measure its properties. For the IH, the maximum luminosity of the breakout burst can be measured at 10 kpc to accuracies of ∼30% for Hyper-Kamiokande (Hyper-K) and ∼60% for the Deep Underground Neutrino Experiment (DUNE). Super-Kamiokande (Super-K) and Jiangmen Underground Neutrino Observatory (JUNO) lack the mass needed to make an accurate measurement. For the IH, the time of the maximum luminosity of the breakout burst can be measured in Hyper-K to an accuracy of ∼3 ms at 7 kpc, in DUNE to ∼2 ms at 4 kpc, and JUNO and Super-K can measure the time of maximum luminosity to an accuracy of ∼2 ms at 1 kpc. Detector backgrounds in IceCube render a measurement of the ν e breakout burst unlikely. For the IH, a measurement of the maximum luminosity of the breakout burst could be used to differentiate between nuclear equations of state.

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“…An alternative PSD, based on the observation of the ortho-positronium (o-Ps) was proposed [7] for β + /β − discrimination. The positron emitted in the IBD process annihilates with an electron in matter, sometimes forming a positronium metastable state, which leads to a delayed annihilation.…”

Section: Introductionmentioning

confidence: 99%

Ortho-positronium observation in the Double Chooz experiment

Abe

Anjos²,

Barrière³

et al. 2014

J. High Energ. Phys.

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The Double Chooz experiment measures the neutrino mixing angle θ 13 by detecting reactorν e via inverse beta decay. The positron-neutron space and time coincidence allows for a sizable background rejection, nonetheless liquid scintillator detectors would profit from a positron/electron discrimination, if feasible in large detector, to suppress the remaining background. Standard particle identification, based on particle dependent time profile of photon emission in liquid scintillator, can not be used given the identical mass of the two particles. However, the positron annihilation is sometimes delayed by the orthopositronium (o-Ps) metastable state formation, which induces a pulse shape distortion that could be used for positron identification. In this paper we report on the first observation of positronium formation in a large liquid scintillator detector based on pulse shape analysis of single events. The o-Ps formation fraction and its lifetime were measured, finding the values of 44 % ± 12 % (sys.) ± 5 % (stat.) and 3.68 ns ± 0.17 ns (sys.) ± 0.15 ns (stat.) respectively, in agreement with the results obtained with a dedicated positron annihilation lifetime spectroscopy setup.

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Positronium signature in organic liquid scintillators for neutrino experiments

Cited by 49 publications

References 24 publications

Final results of Borexino Phase-I on low-energy solar neutrino spectroscopy

Final results of Borexino Phase-I on low-energy solar neutrino spectroscopy

Detecting the Supernova Breakout Burst in Terrestrial Neutrino Detectors

Ortho-positronium observation in the Double Chooz experiment

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