2,340 research outputs found
Reinterpreting the weak mixing angle from atomic parity violation in view of the Cs neutron rms radius measurement from COHERENT
No full textUsing the first model independent average neutron rms radius of Cs133 and I127 obtained from the analysis of the coherent elastic neutrino-nucleus scattering data of the COHERENT experiment, we show the effect on the weak mixing angle measurement from the atomic parity violation (APV) in cesium. Despite that the large uncertainty on the neutron skin measurement makes it difficult to draw statistically significant conclusions on the weak mixing angle, we exploit the fact that the APV result is highly sensitive to the cesium neutron rms radius, Rn, to combine the APV and the COHERENT measurements in order to get a better determination of Rn, assuming that the standard model is correct. The value of Rn=5.42±0.31 fm is obtained, improving significantly the current uncertainty. This result allows to infer a meaningful value of the cesium neutron skin, the difference between the neutron and proton distribution radii, equal to ΔRnp=0.62±0.31 fm, showing for the first time a 2σ deviation from zero
A view of coherent elastic neutrino-nucleus scattering
No full textWe review the physics of coherent elastic neutrino-nucleus scattering and the results and perspectives for the measurements of the radius of the neutron distribution of the nucleus, of the weak mixing angle, and of new neutrino interactions due to physics beyond the Standard Model
Neutrino, electroweak, and nuclear physics from COHERENT elastic neutrino-nucleus scattering with refined quenching factor
No full textWe present an updated analysis of the coherent neutrino-nucleus elastic scattering data of the COHERENT experiment, taking into account the new quenching factor published recently in [Phys. Rev. D 100, 033003 (2019)]. Through a fit of the COHERENT time-integrated energy spectrum, we show that the new quenching factor leads to a better determination of the average rms radius of the neutron distributions of Cs-133 and I-127, while in combination with the atomic parity violation (APV) experimental results, it allows us to determine a data-driven APV measurement of the low-energy weak mixing angle in very good agreement with the Standard Model prediction. We also find a 3.7 sigma evidence of the suppression of coherence due to the nuclear structure. Neutrino properties are better constrained by considering the COHERENT time-dependent spectral data, that allow us to improve the bounds on the neutrino charge radii and magnetic moments. We also present for the first time constraints on the neutrino charges obtained with coherent neutrino-nucleus elastic scattering data. In particular, we obtain the first laboratory constraints on the diagonal charge of nu(mu) and the nu(mu)-nu(tau) transition charge
Muon and electron g - 2and proton and cesium weak charges implications on dark Zd models
No full textTheories beyond the standard model involving a sub-GeV-scale vector 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, , performed at low-energy transfer. In order to do so, we revisit the determination of the cesium from the atomic parity violation experiment, which depends critically on the value of the average neutron rms radius of , by determining the latter from a practically model-independent extrapolation from the recent average neutron rms radius of 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 boson, namely and , when marginalizing over the mass mixing parameter
Constraints on light vector mediators through coherent elastic neutrino nucleus scattering data from COHERENT
No full textWe present new constraints on three different models, the so-called universal, B − L and Lμ− Lτ models, involving a yet to be observed light vector Z′ mediator, by exploiting the recent observation of coherent elastic neutrino-nucleus scattering (CEνNS) 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 CEνNS 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, MZ′, and coupling, gZ′, parameter space
Physics results from the first COHERENT observation of coherent elastic neutrino-nucleus scattering in argon and their combination with cesium-iodide data
No full textWe present the results on the radius of the neutron distribution in Ar40, on the low-energy value of the weak mixing angle, and on the electromagnetic properties of neutrinos obtained from the analysis of the coherent neutrino-nucleus elastic scattering data in argon recently published by the COHERENT Collaboration, taking into account proper radiative corrections. We present also the results of the combined analysis of the COHERENT argon and cesium-iodide data for the determination of the low-energy value of the weak mixing angle and the electromagnetic properties of neutrinos. In particular, the COHERENT argon data allow us to improve significantly the only existing laboratory bounds on the electric charge qμμ of the muon neutrino and on the transition electric charge qμτ
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Potentialities of a low-energy detector based on He evaporation to observe atomic effects in coherent neutrino scattering and physics perspectives
No full textOn the impact of the Migdal effect in reactor CEνNS experiments
No full textThe 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
Nuclear neutron radius and weak mixing angle measurements from latest COHERENT CsI and atomic parity violation Cs data
No full textThe 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 Cs-133 and I-127 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 similar to 4.5% and to disentangle the contributions of the Cs-133 and I-127 nuclei. Interestingly, we show that the COHERENT CsI data show a 6 sigma 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 Cs-133 and I-127, 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 similar to 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
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