A
bstract
We present new constraints on three different models, the so-called universal,
B − L
and
L
μ
− L
τ
models, involving a yet to be observed light vector
Z
′ mediator, by exploiting the recent ...observation of coherent elastic neutrino-nucleus scattering (CE
ν
NS) in argon and cesium-iodide performed by the COHERENT Collaboration. We compare the results obtained from a combination of the above data sets with the limits derived from searches in fixed target, accelerator, solar neutrino and reactor CE
ν
NS experiments, and with the parameter region that could explain the anomalous magnetic moment of the muon. We show that for the universal and the
B − L
models, the COHERENT data allow us to put stringent limits in the light vector mediator mass,
M
Z
′
, and coupling,
g
Z
′
, parameter space.
A
bstract
Despite being neutral particles, neutrinos can have a non-zero charge radius, which represents the only non-null neutrino electromagnetic property in the standard model theory. Its value ...can be predicted with high accuracy and its effect is usually accounted for through the definition of a radiative correction affecting the neutrino couplings to electrons and nucleons at low energy, which results effectively in a shift of the weak mixing angle. Interestingly, it introduces a flavour-dependence in the cross-section. Exploiting available neutrino-electron and coherent elastic neutrino-nucleus scattering (CE
ν
NS) data, there have been many attempts to measure experimentally the neutrino charge radius. Unfortunately, the current precision allows one to only determine constraints on its value. In this work, we discuss how to properly account for the neutrino charge radius in the CE
ν
NS cross-section including the effects of the non-null momentum-transfer in the neutrino electromagnetic form factor, which have been usually neglected when deriving the aforementioned limits. We apply the formalism discussed to a re-analysis of the COHERENT cesium iodide and argon samples and the NCC-1701 germanium data from the Dresden-II nuclear power plant. We quantify the impact of this correction on the CE
ν
NS cross-section and we show that, despite being small, it can not be neglected in the analysis of data from future high-precision experiments. Furthermore, this momentum dependence can be exploited to significantly reduce the allowed values for the neutrino charge radius determination.
A
bstract
Coherent elastic neutrino-nucleus scattering (CE
ν
NS) represents a powerful tool to investigate key electroweak physics parameters and neutrino properties since its first observation in ...2017 by the COHERENT experiment exploiting the spallation neutron source at Oak Ridge National Laboratory. In light of the recent detection of such a process with antineutrinos produced by the Dresden-II reactor scattering off a germanium detector, we revisit the limits so far set on the neutrino magnetic moments, charge radii and millicharges as well as on the weak mixing angle. In order to do so, we also include the contribution of elastic neutrino-electron scattering, whose effect becomes non negligible in some beyond the Standard Model theories. By using different hypotheses for the germanium quenching factor and the reactor antineutrino flux, we provide a measurement of the weak mixing angle at the low-energy scale of the Dresden-II reactor experiment and, thanks to a combined analysis with the latest cesium iodide and argon data set released by the COHERENT Collaboration, we deliver updated limits for the neutrino electromagnetic properties. Interestingly, we are able to set a new best upper limit on the electron neutrino charge radius and significantly improve the other CE
ν
NS-related limits on the neutrino electric charge and magnetic moment.
The COHERENT collaboration observed coherent elastic neutrino nucleus scattering using a 14.6 kg cesium-iodide (CsI) detector in 2017 and recently published the updated results before decommissioning ...the detector. Here, we present the legacy determination of the weak mixing angle and of the average neutron rms radius of
133
Cs
and
127
I
obtained with the full CsI dataset, also exploiting the combination with the atomic parity violation (APV) experimental result, that allows us to achieve a precision as low as
∼
4.5% and to disentangle the contributions of the
133
Cs
and
127
I
nuclei. Interestingly, we show that the COHERENT CsI data show a 6
σ
evidence of the nuclear structure suppression of the full coherence. Moreover, we derive a data-driven APV+COHERENT measurement of the low-energy weak mixing angle with a percent uncertainty, independent of the value of the average neutron rms radius of
133
Cs
and
127
I
,
that is allowed to vary freely in the fit. Additionally, we extensively discuss the impact of using two different determinations of the theoretical parity non-conserving amplitude in the APV fit. Our findings show that the particular choice can make a significant difference, up to 6.5% on
R
n
(Cs) and 11% on the weak mixing angle. Finally, in light of the recent announcement of a future deployment of a 10 kg and a
∼
700 kg cryogenic CsI detectors, we provide future prospects for these measurements, comparing them with other competitive experiments that are foreseen in the near future.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
We present the constraints on the parameters of several light boson mediator models obtained from the analysis of the current data of the COHERENT CE
ν
NS experiment. We consider a variety ...of vector boson mediator models: the so-called universal, the
B − L
and other anomaly-free U(1)′ gauge models with direct couplings of the new vector boson with neutrinos and quarks, and the anomaly-free
L
e
− L
μ
,
L
e
− L
τ
, and
L
μ
− L
τ
gauge models where the coupling of the new vector boson with the quarks is generated by kinetic mixing with the photon at the one-loop level. We consider also a model with a new light scalar boson mediator that is assumed, for simplicity, to have universal coupling with quarks and leptons. Since the COHERENT CE
ν
NS data are well-fitted with the cross section predicted by the Standard Model, the analysis of the data yields constraints for the mass and coupling of the new boson mediator that depend on the charges of quarks and neutrinos in each model under consideration. We compare these constraints with the limits obtained in other experiments and with the values that can explain the muon
g −
2 anomaly in the models where the muon couples to the new boson mediator.
The search for coherent elastic neutrino nucleus scattering (CEνNS) using reactor antineutrinos represents a formidable experimental challenge, recently boosted by the observation of such a process ...at the Dresden-II reactor site using a germanium detector. This observation relies on an unexpected enhancement at low energies of the measured quenching factor with respect to the theoretical Lindhard model prediction, which implies an extra observable ionization signal produced after the nuclear recoil. A possible explanation for this additional contribution could be provided by the so-called Migdal effect, which however has never been observed. Here, we study in detail the impact of the Migdal contribution to the standard CEνNS signal calculated with the Lindhard quenching factor, finding that the former is completely negligible for observed energies below ∼0.3keV where the signal is detectable, and thus unable to provide any contribution to CEνNS searches in this energy regime. To this purpose, we compare different formalisms used to describe the Migdal effect that intriguingly show a perfect agreement, making our findings robust.
Theories beyond the standard model involving a sub-GeV-scale vector Zd mediator have been largely studied as a possible explanation of the experimental values of the muon and electron anomalous ...magnetic moments. Motivated by the recent determination of the anomalous muon magnetic moment performed at Fermilab, we derive the constraints on such a model obtained from the magnetic moment determinations and the measurements of the proton and cesium weak charge, QW , performed at low-energy transfer. In order to do so, we revisit the determination of the cesium QW from the atomic parity violation experiment, which depends critically on the value of the average neutron rms radius of 133Cs , by determining the latter from a practically model-independent extrapolation from the recent average neutron rms radius of 208Pb performed by the PREX-2 Collaboration. From a combined fit of all the aforementioned experimental results, we obtain rather precise limits on the mass and the kinetic mixing parameter of the Z d boson, namely mZd = 47 + 61 − 16 MeV and ϵ = 2.3 + 1.1 − 0.4 × 10 −3, when marginalizing over the Z − Zd mass mixing parameter δ.
PDF
