A bstract We present a method to determine the leading-order (LO) contact term contributing to the nn → ppe − e − amplitude through the exchange of light Majorana neutrinos. Our approach is based on the representation of the amplitude as the momentum integral of a known kernel (proportional to the neutrino propagator) times the generalized forward Compton scattering amplitude n ( p 1 ) n ( p 2 ) W + ( k ) → $$ p\left({p}_1^{\prime}\right)p\left({p}_2^{\prime}\right){W}^{-}(k) $$ p p 1 ′ p p 2 ′ W − k , in analogy to the Cottingham formula for the electromagnetic contribution to hadron masses. We construct model-independent representations of the integrand in the low- and high-momentum regions, through chiral EFT and the operator product expansion, respectively. We then construct a model for the full amplitude by interpolating between these two regions, using appropriate nucleon factors for the weak currents and information on nucleon-nucleon ( NN ) scattering in the 1 S 0 channel away from threshold. By matching the amplitude obtained in this way to the LO chiral EFT amplitude we obtain the relevant LO contact term and discuss various sources of uncertainty. We validate the approach by computing themore »
This content will become publicly available on February 2, 2024
Measurement of the axial vector form factor from antineutrino–proton scattering
Abstract Scattering of high energy particles from nucleons probes their structure, as was done in the experiments that established the non-zero size of the proton using electron beams 1 . The use of charged leptons as scattering probes enables measuring the distribution of electric charges, which is encoded in the vector form factors of the nucleon 2 . Scattering weakly interacting neutrinos gives the opportunity to measure both vector and axial vector form factors of the nucleon, providing an additional, complementary probe of their structure. The nucleon transition axial form factor, F A , can be measured from neutrino scattering from free nucleons, ν μ n → μ − p and $${\bar{\nu }}_{\mu }p\to {\mu }^{+}n$$ ν ¯ μ p → μ + n , as a function of the negative four-momentum transfer squared ( Q 2 ). Up to now, F A ( Q 2 ) has been extracted from the bound nucleons in neutrino–deuterium scattering 3–9 , which requires uncertain nuclear corrections 10 . Here we report the first high-statistics measurement, to our knowledge, of the $${\bar{\nu }}_{\mu }\,p\to {\mu }^{+}n$$ ν ¯ μ p → μ + n cross-section from the hydrogen atom, using the plastic scintillator more »
- Authors:
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publication Date:
- NSF-PAR ID:
- 10410067
- Journal Name:
- Nature
- Volume:
- 614
- Issue:
- 7946
- Page Range or eLocation-ID:
- 48 to 53
- ISSN:
- 0028-0836
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Adopting the Standard Halo Model (SHM) of an isotropic Maxwellian velocity distribution for dark matter (DM) particles in the Galaxy, the most stringent current constraints on their spin-dependent scattering cross-section with nucleons come from the IceCube neutrino observatory and the PICO-60 $$\hbox {C}_3\hbox {F}_8$$ C 3 F 8 superheated bubble chamber experiments. The former is sensitive to high energy neutrinos from the self-annihilation of DM particles captured in the Sun, while the latter looks for nuclear recoil events from DM scattering off nucleons. Although slower DM particles are more likely to be captured by the Sun, the faster ones are more likely to be detected by PICO. Recent N-body simulations suggest significant deviations from the SHM for the smooth halo component of the DM, while observations hint at a dominant fraction of the local DM being in substructures. We use the method of Ferrer et al. (JCAP 1509: 052, 2015) to exploit the complementarity between the two approaches and derive conservative constraints on DM-nucleon scattering. Our results constrain $$\sigma _{\mathrm{SD}} \lesssim 3 \times 10^{-39} \mathrm {cm}^2$$ σ SD ≲ 3 × 10 - 39 cm 2 ( $$6 \times 10^{-38} \mathrm {cm}^2$$ 6 × 10 - 38 cm 2more »
-
Abstract Atmospheric neutrinos are one of the most relevant natural neutrino sources that can be exploited to infer properties about cosmic rays and neutrino oscillations. The Jiangmen Underground Neutrino Observatory (JUNO) experiment, a 20 kton liquid scintillator detector with excellent energy resolution is currently under construction in China. JUNO will be able to detect several atmospheric neutrinos per day given the large volume. A study on the JUNO detection and reconstruction capabilities of atmospheric $$\nu _e$$ ν e and $$\nu _\mu $$ ν μ fluxes is presented in this paper. In this study, a sample of atmospheric neutrino Monte Carlo events has been generated, starting from theoretical models, and then processed by the detector simulation. The excellent timing resolution of the 3” PMT light detection system of JUNO detector and the much higher light yield for scintillation over Cherenkov allow to measure the time structure of the scintillation light with very high precision. Since $$\nu _e$$ ν e and $$\nu _\mu $$ ν μ interactions produce a slightly different light pattern, the different time evolution of light allows to discriminate the flavor of primary neutrinos. A probabilistic unfolding method has been used, in order to infer the primary neutrino energy spectrummore »
-
ABSTRACT Blazars are a rare class of active galactic nuclei (AGNs) with relativistic jets pointing towards the observer. Jets are thought to be launched as Poynting-flux dominated outflows that accelerate to relativistic speeds at the expense of the available magnetic energy. In this work, we consider electron–proton jets and assume that particles are energized via magnetic reconnection in parts of the jet where the magnetization is still high (σ ≥ 1). The magnetization and bulk Lorentz factor Γ are related to the available jet energy per baryon as μ = Γ(1 + σ). We adopt an observationally motivated relation between Γ and the mass accretion rate into the black hole $\dot{m}$, which also controls the luminosity of external radiation fields. We numerically compute the photon and neutrino jet emission as a function of μ and σ. We find that the blazar SED is produced by synchrotron and inverse Compton radiation of accelerated electrons, while the emission of hadronic-related processes is subdominant except for the highest magnetization considered. We show that low-luminosity blazars (Lγ ≲ 1045 erg s−1) are associated with less powerful, slower jets with higher magnetizations in the jet dissipation region. Their broad-band photon spectra resemble those of BL Lac objects,more »
-
A bstract The production of the W ± bosons measured in p–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 8 . 16 TeV and Pb–Pb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5 . 02 TeV with ALICE at the LHC is presented. The W ± bosons are measured via their muonic decay channel, with the muon reconstructed in the pseudorapidity region − 4 < $$ {\eta}_{\textrm{lab}}^{\mu } $$ η lab μ < − 2 . 5 with transverse momentum $$ {p}_{\textrm{T}}^{\mu } $$ p T μ > 10 GeV /c . While in Pb–Pb collisions the measurements are performed in the forward (2 . 5 < $$ {y}_{\textrm{cms}}^{\mu } $$ y cms μ < 4) rapidity region, in p–Pb collisions, where the centre-of-mass frame is boosted with respect to the laboratory frame, the measurements are performed in the backward ( − 4 . 46 < $$ {y}_{\textrm{cms}}^{\mu } $$ y cms μ < − 2 . 96) and forward (2 . 03 < $$ {y}_{\textrm{cms}}^{\mu } $$ y cms μ < 3 . 53) rapidity regions. The W − and W + production cross sections, lepton-charge asymmetry, and nuclear modification factorsmore »
