arXiv subjects

KamLAND Collaboration

Publications and source records attributed to KamLAND Collaboration.

6 recordsLinked to original sources

arXiv2022

First measurement of the strange axial coupling constant using neutral-current quasielastic interactions of atmospheric neutrinos at KamLAND

We report a measurement of the strange axial coupling constant $g_A^s$ using atmospheric neutrino data at KamLAND. This constant is a component of the axial form factor of the neutral-current quasielastic (NCQE) interaction. The value of $g_A^s$ significantly changes the ratio of proton and neutron NCQE cross sections. KamLAND is suitable for measuring NCQE interactions as it can detect nucleon recoils with low-energy thresholds and measure neutron multiplicity with high efficiency. KamLAND data, including the information on neutron multiplicity associated with the NCQE interactions, makes it possible to measure $g_A^s$ with a suppressed dependence on the axial mass $M_A$, which has not yet been determined. For a comprehensive prediction of the neutron emission associated with neutrino interactions, we establish a simulation of particle emission via nuclear deexcitation of $^{12}$C, a process not considered in existing neutrino Monte Carlo event generators. Energy spectrum fitting for each neutron multiplicity gives $g_A^s =-0.14^{+0.25}_{-0.26}$, which is the most stringent limit obtained using NCQE interactions without $M_A$ constraints. The two-body current contribution considered in this analysis relies on a theoretically effective model and electron scattering experiments and requires future verification by direct measurements and future model improvement.

hep-ex↗

arXiv2016

Search for electron antineutrinos associated with gravitational wave events GW150914 and GW151226 using KamLAND

We present a search for low energy antineutrino events coincident with the gravitational wave events GW150914 and GW151226, and the candidate event LVT151012 using KamLAND, a kiloton-scale antineutrino detector. We find no inverse beta-decay neutrino events within $\pm 500$ seconds of either gravitational wave signal. This non-detection is used to constrain the electron antineutrino fluence and the luminosity of the astrophysical sources.

astro-ph.HE↗

arXiv2015

Search for the proton decay mode $p \rightarrow \overlineν K^{+}$ with KamLAND

We present a search for the proton decay mode $p \rightarrow \overlineν K^{+}$ based on an exposure of 8.97 kton-years in the KamLAND experiment. The liquid scintillator detector is sensitive to successive signals from $p \rightarrow \overlineν K^{+}$ with unique kinematics, which allow us to achieve a detection efficiency of 44%, higher than previous searches in water Cherenkov detectors. We find no evidence of proton decays for this mode. The expected background, which is dominated by atmospheric neutrinos, is $0.9 \pm 0.2$ events. The nonbackground-subtracted limit on the partial proton lifetime is $τ/ B(p \rightarrow \overlineν K^{+}) > 5.4 \times 10^{32}$ years at 90% C.L.

hep-ex↗

arXiv2011

Measurement of the 8B Solar Neutrino Flux with the KamLAND Liquid Scintillator Detector

We report a measurement of the neutrino-electron elastic scattering rate from 8B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, above a 5.5 MeV analysis threshold is 1.49+/-0.14(stat)+/-0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a 8B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77+/-0.26(stat)+/-0.32(syst) x 10^6 cm^-2s^-1. The analysis threshold is driven by 208Tl present in the liquid scintillator, and the main source of systematic uncertainty is due to background from cosmogenic 11Be. The measured rate is consistent with existing measurements and with Standard Solar Model predictions which include matter enhanced neutrino oscillation.

hep-ex↗

arXiv2004

A High Sensitivity Search for $\barν_{e}$'s from the Sun and Other Sources at KamLAND

Data corresponding to a KamLAND detector exposure of 0.28 kton-year has been used to search for $\barν_e$'s in the energy range 8.3 MeV $<$ E$_{\barν_e}$ $<$ 14.8 MeV. No candidates were found for an expected background of $1.1{\pm}0.4$ events. This result can be used to obtain a limit on $\barν_{e}$ fluxes of any origin. Assuming that all $\barν_e$ flux has its origin in the Sun and has the characteristic $^8$B solar $ν_e$ energy spectrum, we obtain an upper limit of 3.7 \times 10$^2$ cm$^{-2}$ s$^{-1}$ (90% C.L.) on the $\barν_e$ flux. We interpret this limit, corresponding to $2.8{\times}10^{-4}$ of the Standard Solar Model $^8$B $ν_e$ flux, in the framework of spin--flavor precession and neutrino decay models.

hep-ex↗

arXiv2002

First Results from KamLAND: Evidence for Reactor Anti-Neutrino Disappearance

KamLAND has been used to measure the flux of $\barν_e$'s from distant nuclear reactors. In an exposure of 162 ton$\cdot$yr (145.1 days) the ratio of the number of observed inverse $β$-decay events to the expected number of events without disappearance is $0.611\pm 0.085 {\rm (stat)} \pm 0.041 {\rm (syst)} $ for $\barν_e$ energies $>$ 3.4 MeV. The deficit of events is inconsistent with the expected rate for standard $\barν_e$ propagation at the 99.95% confidence level. In the context of two-flavor neutrino oscillations with CPT invariance, these results exclude all oscillation solutions but the `Large Mixing Angle' solution to the solar neutrino problem using reactor $\barν_e$ sources.

hep-ex↗