The T2K ND280 off-axis pi–zero detector Assylbekov, S.; Barr, G.; Berger, B.E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
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The pi–zero detector (PØD) is one of the subdetectors that makes up the off-axis near detector for the Tokai-to-Kamioka (T2K) long baseline neutrino experiment. The primary goal for the PØD is to ...measure the relevant cross-sections for neutrino interactions that generate π0's, especially the cross-section for neutral current π0 interactions, which are one of the dominant sources of background to the νμ→νe appearance signal in T2K. The PØD is composed of layers of plastic scintillator alternating with water bags and brass sheets or lead sheets and is one of the first detectors to use Multi-Pixel Photon Counters (MPPCs) on a large scale.
Historically high N prices have increased farmer interest in economic optimum N rates for rice (Oryza sativa L.). This study uses five to 8 yr of rice variety by N data from four research locations ...in Arkansas varying by soil series Perry clay (Vertic Haplaquepts); Sharkey clay (Vertic Haplaquepts); DeWitt silt loam (Typic Albaqualfs); and Hillemann silt loam (Thermic, Albic, Glossic Natraqualfs) to estimate rice yield response to N functions for five common functional forms quadratic, quadratic-plateau, square root, linear-plateau, and Mitscherlich. Economic optimum N rates (EONs) are calculated by location and functional form across years using both nonlinear optimization and a numerical method proposed for making N rate guidelines in the Corn Belt of the United States. Statistical analysis indicated the quadratic fits the yield data best at three of four locations and performs as well as either the linear-plateau or quadratic-plateau at the fourth location. The numerical method produces approximately the same EON rates (within ±1 kg ha–1) as nonlinear optimization. Economic optimum N rates varied by research location and are as follows assuming average 2006–2008 rice price and N cost data and annual quadratic functions: 150 kg N ha–1 at the DeWitt silt loam location; 122 kg N ha–1 at the Hillemann silt loam location; 181 kg N ha–1 at the Sharkey clay location; and 187 kg N ha–1 at the Perry clay location.
A supermassive black hole, obscured by cosmic dust, powers the nearby active galaxy NGC 1068. Neutrinos, which rarely interact with matter, could provide information on the galaxy’s active core. We ...searched for neutrino emission from astrophysical objects using data recorded with the IceCube neutrino detector between 2011 and 2020. The positions of 110 known gamma-ray sources were individually searched for neutrino detections above atmospheric and cosmic backgrounds. We found that NGC 1068 has an excess of
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neutrinos at tera–electron volt energies, with a global significance of 4.2σ, which we interpret as associated with the active galaxy. The flux of high-energy neutrinos that we measured from NGC 1068 is more than an order of magnitude higher than the upper limit on emissions of tera–electron volt gamma rays from this source.
Nearby active galaxy emits neutrinos
Observations have shown a diffuse background of high-energy neutrinos, which is known to be of extragalactic origin. However, it has been difficult to identify individual sources that contribute to this background. The IceCube Collaboration reanalyzed the arrival directions of astrophysical neutrinos and then searched for point sources (see the Perspective by Murase). They identified evidence for neutrino emission from NGC 1068 (also known as Messier 77), a nearby active galaxy. Its properties are quite different from TXS 0506+056, which was found to be a neutrino source in 2018, leading the investigators to suggest that there might be more than one population contributing to the neutrino background. —KTS
The arrival directions of astrophysical neutrinos indicate point source neutrino emission from NGC 1068.
On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced ...Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of \(\sim 1.7\,{\rm{s}}\) with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of \({40}_{-8}^{+8}\) Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 \(\,{M}_{\odot }\). An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at \(\sim 40\,{\rm{Mpc}}\)) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position \(\sim 9\) and \(\sim 16\) days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.
ABSTRACT The IceCube Collaboration has previously discovered a high-energy astrophysical neutrino flux using neutrino events with interaction vertices contained within the instrumented volume of the ...IceCube detector. We present a complementary measurement using charged current muon neutrino events where the interaction vertex can be outside this volume. As a consequence of the large muon range the effective area is significantly larger but the field of view is restricted to the Northern Hemisphere. IceCube data from 2009 through 2015 have been analyzed using a likelihood approach based on the reconstructed muon energy and zenith angle. At the highest neutrino energies between and a significant astrophysical contribution is observed, excluding a purely atmospheric origin of these events at significance. The data are well described by an isotropic, unbroken power-law flux with a normalization at neutrino energy of and a hard spectral index of . The observed spectrum is harder in comparison to previous IceCube analyses with lower energy thresholds which may indicate a break in the astrophysical neutrino spectrum of unknown origin. The highest-energy event observed has a reconstructed muon energy of which implies a probability of less than for this event to be of atmospheric origin. Analyzing the arrival directions of all events with reconstructed muon energies above no correlation with known γ-ray sources was found. Using the high statistics of atmospheric neutrinos we report the current best constraints on a prompt atmospheric muon neutrino flux originating from charmed meson decays which is below 1.06 in units of the flux normalization of the model in Enberg et al.
We report on measurements of the all-particle cosmic ray energy spectrum and composition in the PeV to EeV energy range using 3 years of data from the IceCube Neutrino Observatory. The IceTop ...detector measures cosmic ray induced air showers on the surface of the ice, from which the energy spectrum of cosmic rays is determined by making additional assumptions about the mass composition. A separate measurement is performed when IceTop data are analyzed in coincidence with the high-energy muon energy loss information from the deep in-ice IceCube detector. In this measurement, both the spectrum and the mass composition of the primary cosmic rays are simultaneously reconstructed using a neural network trained on observables from both detectors. The performance and relative advantages of these two distinct analyses are discussed, including the systematic uncertainties and the dependence on the hadronic interaction models, and both all-particle spectra as well as individual spectra for elemental groups are presented.
We have searched for proton decay via p→e+π0 and p→μ+π0 using Super-Kamiokande data from April 1996 to March 2015, 0.306 megaton·years exposure in total. The atmospheric neutrino background rate in ...Super-Kamiokande IV is reduced to almost half that of phase I-III by tagging neutrons associated with neutrino interactions. The reach of the proton lifetime is further enhanced by introducing new signal criteria that select the decay of a proton in a hydrogen atom. No candidates were seen in the p→e+π0 search. Two candidates that passed all of the selection criteria for p→μ+π0 have been observed, but these are consistent with the expected number of background events of 0.87. Lower limits on the proton lifetime are set at τ/B(p→e+π0)>1.6×1034 years and τ/B(p→μ+π0)>7.7×1033 years at 90% confidence level.
ABSTRACT The recent discovery of a diffuse cosmic neutrino flux extending up to PeV energies raises the question of which astrophysical sources generate this signal. Blazars are one class of ...extragalactic sources which may produce such high-energy neutrinos. We present a likelihood analysis searching for cumulative neutrino emission from blazars in the 2nd Fermi-LAT AGN catalog (2LAC) using IceCube neutrino data set 2009-12, which was optimized for the detection of individual sources. In contrast to those in previous searches with IceCube, the populations investigated contain up to hundreds of sources, the largest one being the entire blazar sample in the 2LAC catalog. No significant excess is observed, and upper limits for the cumulative flux from these populations are obtained. These constrain the maximum contribution of 2LAC blazars to the observed astrophysical neutrino flux to 27% or less between around 10 TeV and 2 PeV, assuming the equipartition of flavors on Earth and a single power-law spectrum with a spectral index of −2.5. We can still exclude the fact that 2LAC blazars (and their subpopulations) emit more than 50% of the observed neutrinos up to a spectral index as hard as −2.2 in the same energy range. Our result takes into account the fact that the neutrino source count distribution is unknown, and it does not assume strict proportionality of the neutrino flux to the measured 2LAC γ-ray signal for each source. Additionally, we constrain recent models for neutrino emission by blazars.
The results of a 3 + 1 sterile neutrino search using eight years of data from the IceCube Neutrino Observatory are presented. A total of 305 735 muon neutrino events are analyzed in reconstructed ...energy-zenith space to test for signatures of a matter-enhanced oscillation that would occur given a sterile neutrino state with a mass-squared differences between 0.01 and 100 eV2. The best-fit point is found to be at sin2(2θ24) = 0.10 and Δm412 = 4.5 eV2, which is consistent with the no sterile neutrino hypothesis with a p value of 8.0%.
Inelasticity, the fraction of a neutrino’s energy transferred to hadrons, is a quantity of interest in the study of astrophysical and atmospheric neutrino interactions at multi-TeV energies with ...IceCube. In this work, a sample of contained neutrino interactions in IceCube is obtained from five years of data and classified as 2650 tracks and 965 cascades. Tracks arise predominantly from charged-current νμ interactions, and we demonstrate that we can reconstruct their energy and inelasticity. The inelasticity distribution is found to be consistent with the calculation of Cooper-Sarkar et al. across the energy range from ∼1 to ∼100 TeV. Along with cascades from neutrinos of all flavors, we also perform a fit over the energy, zenith angle, and inelasticity distribution to characterize the flux of astrophysical and atmospheric neutrinos. The energy spectrum of diffuse astrophysical neutrinos is described well by a power law in both track and cascade samples, and a best-fit index γ=2.62±0.07 is found in the energy range from 3.5 TeV to 2.6 PeV. Limits are set on the astrophysical flavor composition and are compatible with a ratio of (13∶13∶13)⊕. Exploiting the distinct inelasticity distribution of νμ and ν¯μ interactions, the atmospheric νμ to ν¯μ flux ratio in the energy range from 770 GeV to 21 TeV is found to be 0.77−0.25+0.44 times the calculation by Honda et al. Lastly, the inelasticity distribution is also sensitive to neutrino charged-current charm production. The data are consistent with a leading-order calculation, with zero charm production excluded at 91% confidence level. Future analyses of inelasticity distributions may probe new physics that affects neutrino interactions both in and beyond the Standard Model.
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