Neutrinos were assumed to be massless particles until the discovery of the neutrino oscillation process. This phenomenon indicates that the neutrinos have non-zero masses and the mass eigenstates ...(ν1, ν2, ν3) are mixtures of their flavour eigenstates (νe, νμ, ντ). The oscillations between different flavour eigenstates are described by three mixing angles (θ12, θ23, θ13), two differences of the squared neutrino masses of the ν2/ν1 and ν3/ν1 pairs and a charge conjugation parity symmetry violating phase δCP. The Double Chooz experiment, located near the Chooz Electricité de France reactors, measures the oscillation parameter θ13 using reactor neutrinos. Here, the Double Chooz collaboration reports the measurement of the mixing angle θ13 with the new total neutron capture detection technique from the full data set, yielding sin2(2θ13) = 0.105 ± 0.014. This measurement exploits the multidetector configuration, the isoflux baseline and data recorded when the reactors were switched off. In addition to the neutrino mixing angle measurement, Double Chooz provides a precise measurement of the reactor neutrino flux, given by the mean cross-section per fission 〈σf〉 = (5.71 ± 0.06) × 10−43 cm2 per fission, and reports an empirical model of the distortion in the reactor neutrino spectrum.The Double Chooz collaboration reports the neutrino oscillation parameter θ13 from a measurement of the disappearance of reactor anti-electron neutrinos with the total neutron capture technique.
In experiments for direct dark matter searches, neutrinos coherently scattering off nuclei can produce similar events as Weakly Interacting Massive Particles (WIMPs). The calculated count rate for ...solar neutrinos in such experiments is a few events per ton-year. This count rate strongly depends on the nuclear recoil energy threshold achieved in the experiments for the WIMP search. We show that solar neutrinos can be a serious background source for direct dark matter search experiments using Ge, Ar, Xe and CaWO
4 as target materials. To reach sensitivities better than ∼10
−10
pb for the elastic WIMP nucleon spin-independent cross section in the zero-background limit, energy thresholds for nuclear recoils should be ≳2.05
keV for CaWO
4, ≳4.91
keV for Ge, ≳2.89
keV for Xe, and ≳8.62
keV for Ar as target material. Next-generation experiments should not only strive for a reduction of the present energy thresholds but mainly focus on an increase of the target mass. Atmospheric neutrinos limit the achievable sensitivity for the background-free direct dark matter search to ≳10
−12
pb.
A
bstract
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
τ
e
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
2
θ
W
is obtained with a precision comparable to that achieved in reactor antineutrino experiments
.
The Double Chooz antineutrino detectors Abe, Y.; Alba, J.; Barriere, J. C. ...
European physical journal. C, Particles and fields,
09/2022, Letnik:
82, Številka:
9
Journal Article
Recenzirano
Odprti dostop
This article describes the setup and performance of the near and far detectors in the Double Chooz experiment. The electron antineutrinos of the Chooz nuclear power plant were measured in two ...identically designed detectors with different average baselines of about 400 m and 1050 m from the two reactor cores. Over many years of data taking the neutrino signals were extracted from interactions in the detectors with the goal of measuring a fundamental parameter in the context of neutrino oscillation, the mixing angle
θ
13
. The central part of the Double Chooz detectors was a main detector comprising four cylindrical volumes filled with organic liquids. From the inside towards the outside there were volumes containing gadolinium-loaded scintillator, gadolinium-free scintillator, a buffer oil and, optically separated, another liquid scintillator acting as veto system. Above this main detector an additional outer veto system using plastic scintillator strips was installed. The technologies developed in Double Chooz were inspiration for several other antineutrino detectors in the field. The detector design allowed implementation of efficient background rejection techniques including use of pulse shape information provided by the data acquisition system. The Double Chooz detectors featured remarkable stability, in particular for the detected photons, as well as high radiopurity of the detector components.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present a search for signatures of neutrino mixing of electron anti-neutrinos with additional hypothetical sterile neutrino flavors using the Double Chooz experiment. The search is based on data ...from 5 years of operation of Double Chooz, including 2 years in the two-detector configuration. The analysis is based on a profile likelihood, i.e. comparing the data to the model prediction of disappearance in a data-to-data comparison of the two respective detectors. The analysis is optimized for a model of three active and one sterile neutrino. It is sensitive in the typical mass range
5
×
10
-
3
eV
2
≲
Δ
m
41
2
≲
3
×
10
-
1
eV
2
for mixing angles down to
sin
2
2
θ
14
≳
0.02
. No significant disappearance additionally to the conventional disappearance related to
θ
13
is observed and correspondingly exclusion bounds on the sterile mixing parameter
θ
14
as a function of
Δ
m
41
2
are obtained.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We have measured the flux of cosmic muons in the Laboratori Nazionali del Gran Sasso at 3800 m w.e. to be (3.432±0.003)ċ10−4 m−2s−1 based on ten years of Borexino data acquired between May 2007 and ...May 2017. A seasonal modulation with a period of (366.3±0.6) d and a relative amplitude of (1.36±0.04)% is observed. The phase is measured to be (181.7±0.4) d, corresponding to a maximum at the 1st 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 αT=0.90±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 rK/π=0.11+0.11−0.07 for primary energies above 18 TeV. We find evidence for a long-term modulation of the muon flux with a period of ∼3000 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±0.4)%.
The main goal of the JUNO experiment is the determination of the neutrino mass ordering. To achieve this, an extraordinary energy resolution of at least 3 % at 1 MeV is required for which all parts ...of the JUNO detector need to meet certain quality criteria. This is relevant in particular for those which are related to the energy resolution of the detector, such as the photomultiplier tubes (PMTs) to be deployed in JUNO. This paper presents the setup and performance of a dedicated PMT mass testing facility to examine and characterize the performance of the 20-inch JUNO PMTs. Its quasi-industrial size and operation level allows to test all 20000 PMTs intended to be used in the JUNO experiment. With this PMT mass testing system, several key characteristics like dark count rate, peak-to-valley ratio, photon detection efficiency, and timing resolution have been determined at an operating gain of 1 נ107 and assessed with respect to the requirements of JUNO. Measurement conditions and modes for the PMTs as well as estimated accuracies for the determination of the individual PMT parameters with the system are presented as well.
We report the complete GNO solar neutrino results for the measuring periods GNO III, GNO II, and GNO I. The result for GNO III (last 15 solar runs) is 54.3−9.3+9.9(stat)±2.3(syst)SNU(1σ) or ...54.3−9.6+10.2(incl. syst) SNU (1σ) with errors combined. The GNO experiment is now terminated after altogether 58 solar exposure runs that were performed between 20 May 1998 and 9 April 2003. The combined result for GNO (I+II+III) is 62.9−5.3+5.5(stat)±2.5(syst) SNU (1σ) or 62.9−5.9+6.0 SNU (1σ) with errors combined in quadrature. Overall, gallium based solar observations at LNGS (first in GALLEX, later in GNO) lasted from 14 May 1991 through 9 April 2003. The joint result from 123 runs in GNO and GALLEX is 69.3±5.5(incl. syst) SNU (1σ). The distribution of the individual run results is consistent with the hypothesis of a neutrino flux that is constant in time. Implications from the data in particle- and astrophysics are reiterated.
A
bstract
A
θ
13
oscillation analysis based on the observed antineutrino rates at the Double Chooz far and near detectors for different reactor power conditions is presented. This approach provides a ...so far unique simultaneous determination of
θ
13
and the total background rates without relying on any assumptions on the specific background contributions. The analysis comprises 865 days of data collected in both detectors with at least one reactor in operation. The oscillation results are enhanced by the use of 24.06 days (12.74 days) of reactor-off data in the far (near) detector. The analysis considers the
ν
¯
e
interactions up to a visible energy of 8.5 MeV, using the events at higher energies to build a cosmogenic background model considering fast-neutrons interactions and
9
Li decays. The background-model-independent determination of the mixing angle yields sin
2
(2
θ
13
) = 0
.
094 ± 0
.
017, being the best-fit total background rates fully consistent with the cosmogenic background model. A second oscillation analysis is also performed constraining the total background rates to the cosmogenic background estimates. While the central value is not significantly modified due to the consistency between the reactor-off data and the background estimates, the addition of the background model reduces the uncertainty on
θ
13
to 0.015. Along with the oscillation results, the normalization of the anti-neutrino rate is measured with a precision of 0.86%, reducing the 1.43% uncertainty associated to the expectation.
Abstract
The Accelerator Neutrino Neutron Interaction Experiment
(ANNIE) is a 26-ton water Cherenkov neutrino detector installed on
the Booster Neutrino Beam (BNB) at Fermilab. Its main physics goals
...are to perform a measurement of the neutron yield from
neutrino-nucleus interactions, as well as a measurement of the
charged-current cross section of muon neutrinos. An equally
important focus is the research and development of new detector
technologies and target media. Specifically, water-based liquid
scintillator (WbLS) is of interest as a novel detector medium, as it
allows for the simultaneous detection of Cherenkov light and
scintillation. This paper presents the deployment of a 366 L WbLS
vessel in ANNIE in March 2023 and the subsequent detection of both
Cherenkov light and scintillation from the WbLS. This
proof-of-concept allows for the future development of reconstruction
and particle identification algorithms in ANNIE, as well as
dedicated analyses within the WbLS volume, such as the search for
neutral-current events and the hadronic scintillation component.
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