57 research outputs found
Quark Matter in a Strong Magnetic Background
In this chapter, we discuss several aspects of the theory of strong
interactions in presence of a strong magnetic background. In particular, we
summarize our results on the effect of the magnetic background on chiral
symmetry restoration and deconfinement at finite temperature. Moreover, we
compute the magnetic susceptibility of the chiral condensate and the quark
polarization at zero temperature. Our theoretical framework is given by chiral
models: the Nambu-Jona-Lasinio (NJL), the Polyakov improved NJL (or PNJL) and
the Quark-Meson (QM) models. We also compare our results with the ones obtained
by other groups.Comment: 34 pages, survey. To appear in Lect. Notes Phys. "Strongly
interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K.
Landsteiner, A. Schmitt, H.-U. Ye
Search for astrophysical electron antineutrinos in Super-Kamiokande with 0.01wt% gadolinium-loaded water
We report the first search result for the flux of astrophysical electron
antineutrinos for energies O(10) MeV in the gadolinium-loaded Super-Kamiokande
(SK) detector. In June 2020, gadolinium was introduced to the ultra-pure water
of the SK detector in order to detect neutrons more efficiently. In this new
experimental phase, SK-Gd, we can search for electron antineutrinos via inverse
beta decay with efficient background rejection and higher signal efficiency
thanks to the high efficiency of the neutron tagging technique. In this paper,
we report the result for the initial stage of SK-Gd with a exposure at 0.01% Gd mass concentration. No significant excess
over the expected background in the observed events is found for the neutrino
energies below 31.3 MeV. Thus, the flux upper limits are placed at the 90%
confidence level. The limits and sensitivities are already comparable with the
previous SK result with pure-water () owing
to the enhanced neutron tagging
Search for astrophysical electron antineutrinos in Super-Kamiokande with 0.01% gadolinium-loaded water
We report the first search result for the flux of astrophysical electron antineutrinos for energies (10) MeV in the gadolinium-loaded Super-Kamiokande (SK) detector. In 2020 June, gadolinium was introduced to the ultrapure water of the SK detector in order to detect neutrons more efficiently. In this new experimental phase, SK-Gd, we can search for electron antineutrinos via inverse beta decay with efficient background rejection thanks to the high efficiency of the neutron tagging technique. In this paper, we report the result for the initial stage of SK-Gd, during 2020 August 26, and 2022 June 1 with a 22.5 × 552 kton · day exposure at 0.01% Gd mass concentration. No significant excess over the expected background in the observed events is found for the neutrino energies below 31.3 MeV. Thus, the flux upper limits are placed at the 90% confidence level. The limits and sensitivities are already comparable with the previous SK result with pure water (22.5 × 2970 kton · day) owing to the enhanced neutron tagging. Operation with Gd increased to 0.03% started in 2022 June.DE-SC0015628 - Department of Energyhttp://10.0.15.7/2041-8213/acdc9
Scintillator ageing of the T2K near detectors from 2010 to 2021
The T2K experiment widely uses plastic scintillator as a target for neutrino interactions and an active medium for the measurement of charged particles produced in neutrino interactions at its near detector complex. Over 10 years of operation the measured light yield recorded by the scintillator based subsystems has been observed to degrade by 0.9–2.2% per year. Extrapolation of the degradation rate through to 2040 indicates the recorded light yield should remain above the lower threshold used by the current reconstruction algorithms for all subsystems. This will allow the near detectors to continue contributing to important physics measurements during the T2K-II and Hyper-Kamiokande eras. Additionally, work to disentangle the degradation of the plastic scintillator and wavelength shifting fibres shows that the reduction in light yield can be attributed to the ageing of the plastic scintillator. The long component of the attenuation length of the wavelength shifting fibres was observed to degrade by 1.3–5.4% per year, while the short component of the attenuation length did not show any conclusive degradation
Measurements of the charge ratio and polarization of cosmic-ray muons with the Super-Kamiokande detector
We present the results of the charge ratio (R) and polarization (Pμ0) measurements using the decay electron events collected from 2008 September to 2022 June by the Super-Kamiokande detector. Because of its underground location and long operation, we performed high precision measurements by accumulating cosmic-ray muons. We measured the muon charge ratio to be R=1.32±0.02 (stat.+syst.) at EμcosθZenith=0.7+0.3−0.2 TeV, where Eμ is the muon energy and θZenith is the zenith angle of incoming cosmic-ray muons. This result is consistent with the Honda flux model while this suggests a tension with the πK model of 1.9σ. We also measured the muon polarization at the production location to be Pμ0=0.52±0.02 (stat.+syst.) at the muon momentum of 0.9+0.6−0.1 TeV/c at the surface of the mountain; this also suggests a tension with the Honda flux model of 1.5σ. This is the most precise measurement ever to experimentally determine the cosmic-ray muon polarization near 1 TeV/c. These measurement results are useful to improve the atmospheric neutrino simulations
Implementation of the SuSAv2-meson exchange current 1p1h and 2p2h models in GENIE and analysis of nuclear effects in T2K measurements
International audienceWe first present the implementation and validation of the SuSAv2-MEC 1p1h and 2p2h models in the GENIE neutrino-nucleus interaction event generator and a comparison of the subsequent predictions to measurements of lepton and hadron kinematics from the T2K experiment. These predictions are also compared to those of other available models in GENIE. We further compare semi-inclusive predictions of the implemented 1p1h model to those of the microscopic model on which SuSAv2 is based—relativistic mean field—to begin to test the validity of widely used “factorization” assumptions employed by generators to predict hadron kinematics from inclusive input models. The results highlight that a more precise treatment of hadron kinematics in generators is essential in order to attain the few-% level uncertainty on neutrino interactions necessary for the next generation of accelerator-based long-baseline neutrino oscillation experiments
Modeling neutrino-nucleus interactions for neutrino oscillation experiments
International audienceWe present our recent progress on the relativistic modeling of neutrino-nucleus reactions for their implementation in MonteCarlo event generators (GENIE, NEUT) employed in neutrino oscillation experiments. We compare charged-current neutrino ( ) and antineutrino ( ) cross sections obtained within the SuSAv2 model, which is based on the Relativistic Mean Field theory and on the analysis of the superscaling behavior exhibited by ( ) data. We also evaluate and discuss the impact of multi-nucleon excitations arising from 2p–2h states excited by the action of weak forces in a fully relativistic framework, showing for the first time their implementation in GENIE and their comparison with recent T2K data
Implementation of the SuSAv2-MEC 1p1h and 2p2h models in GENIE and analysis of nuclear effects in T2K measurements
We first present the implementation and validation of the SuSAv2-MEC 1p1h and 2p2h models in the GENIE neutrino-nucleus interaction event generator and a comparison of the subsequent predictions to measurements of lepton and hadron kinematics from the T2K experiment. These predictions are also compared to those of other available models in GENIE. We additionally compare the semi-inclusive predictions of the implemented 1p1h model to those of the microscopic model on which SuSAv2 is based - Relativistic Mean Field (RMF) - to begin to test the validity of widely-used `factorisation' assumptions employed by generators to predict hadron kinematics from inclusive input models. The results highlight that a more precise treatment of hadron kinematics in generators is essential in order to attain the few-% level uncertainty on neutrino interactions necessary for the next generation of accelerator-based long-baseline neutrino oscillation experiments
Analysis of the MINERvA antineutrino double-differential cross sections within the SuSAv2 model including meson-exchange currents
International audienceWe compare the results of the SuSAv2 model including meson-exchange currents (MEC) with the recent measurement of the quasielasticlike double differential antineutrino cross section on a hydrocarbon performed by the MINERvA Collaboration [C. E. Patrick (MINERvA Collaboration), Phys. Rev. D 97, 052002 (2018)10.1103/PhysRevD.97.052002]. The relativistic nature of the model makes it suitable to describe these data, which correspond to a mean beam energy of 3.5 GeV. The standard SuSAv2 model predictions agree well with the data without needing any additional or tuned parameter. The role of longitudinal MEC is non-negligible and improves the agreement with the data. We also consider the impact of different treatments of the Δ-resonance propagator in the two-body currents on the data comparison
Theoretical description of semi-inclusive T2K, MINERνA and MicroBooNE neutrino-nucleus data in the relativistic plane wave impulse approximation
International audienceWe present the results of semi-inclusive neutrino-nucleus cross sections within the plane wave impulse approximation (PWIA) for three nuclear models: relativistic Fermi gas, independent-particle shell model, and natural orbital shell model in comparison with the available CC0π measurements from the T2K, MINERνA, and MicroBooNE collaborations where a muon and at least one proton are detected in the final state. Results are presented as a function of the momenta and angles of the final particles, as well as in terms of the imbalances between proton and muon kinematics. The present semi-inclusive formalism is based on fully relativistic microscopic calculations and numerical integrations to produce both lepton and hadron kinematics without relying on further approximations. The analysis reveals that contributions beyond PWIA are crucial to explain the experimental measurements and that the study of correlations between final-state proton and muon kinematics can provide valuable information on relevant nuclear effects such as the Fermi motion and final-state interactions
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