A spectral fitter based on the graphics processor unit (GPU) has been developed for Borexino solar neutrino analysis. It is able to shorten the fitting time to a superior level compared to the CPU ...fitting procedure. In Borexino solar neutrino spectral analysis, fitting usually requires around one hour to converge since it includes time-consuming convolutions in order to account for the detector response and pile-up effects. Moreover, the convergence time increases to more than two days when including extra computations for the discrimination of \(^{11}\)C and external \(\gamma\)s. In sharp contrast, with the GPU-based fitter it takes less than 10 seconds and less than four minutes, respectively. This fitter is developed utilizing the GooFit project with customized likelihoods, pdfs and infrastructures supporting certain analysis methods. In this proceeding the design of the package, developed features and the comparison with the original CPU fitter are presented.
A search for the solar neutrino effective magnetic moment has been performed using data from 1291.5 days exposure during the second phase of the Borexino experiment. No significant deviations from ...the expected shape of the electron recoil spectrum from solar neutrinos have been found, and a new upper limit on the effective neutrino magnetic moment of \(\mu_{\nu}^{eff}\) \(<\) 2.8\(\cdot\)10\(^{-11}\) \(\mu_{B}\) at 90\% c.l. has been set using constraints on the sum of the solar neutrino fluxes implied by the radiochemical gallium experiments.Using the limit for the effective neutrino moment, new limits for the magnetic moments of the neutrino flavor states, and for the elements of the neutrino magnetic moments matrix for Dirac and Majorana neutrinos, are derived.
Phys. Rev. D 100, 082004 (2019) We present the first simultaneous measurement of the interaction rates of
$pp$, $^7$Be, and $pep$ solar neutrinos performed with a global fit to the
Borexino data in ...an extended energy range (0.19-2.93)$\,$MeV. This result was
obtained by analyzing 1291.51$\,$days of Borexino Phase-II data, collected
between December 2011 and May 2016 after an extensive scintillator purification
campaign. We find:
rate($pp$)$\,$=$\,$$134$$\,$$\pm$$\,$$10$$\,$($stat$)$\,$$^{\rm +6}_{\rm
-10}$$\,$($sys$)$\,$cpd/100$\,$t,
rate($^7$Be)$\,$=$\,$$48.3$$\,$$\pm$$\,$$1.1$$\,$($stat$)$\,$$^{\rm +0.4}_{\rm
-0.7}$$\,$($sys$)$\,$cpd/100$\,$t, and
rate($pep$)$\,$=$\,$$2.43$$\pm$$\,$$0.36$$\,$($stat$)$^{+0.15}_{-0.22}$$\,$($sys$)$\,$cpd/100$\,$t.
These numbers are in agreement with and improve the precision of our previous
measurements. In particular, the interaction rate of $^7$Be $\nu$'s is measured
with an unprecedented precision of 2.7%, showing that discriminating between
the high and low metallicity solar models is now largely dominated by
theoretical uncertainties. The absence of $pep$ neutrinos is rejected for the
first time at more than 5$\,$$\sigma$. An upper limit of $8.1$$\,$cpd/100$\,$t
(95%$\,$C.L.) on the CNO neutrino rate is obtained by setting an additional
constraint on the ratio between the $pp$ and $pep$ neutrino rates in the fit.
This limit has the same significance as that obtained by the Borexino Phase-I
(currently providing the tightest bound on this component), but is obtained by
applying a less stringent constraint on the $pep$ $\nu$ flux.
We present the results of a low-energy neutrino search using the Borexino detector in coincidence with the gravitational wave (GW) events GW150914, GW151226 and GW170104. We searched for correlated ...neutrino events with energies greater than 250 keV within a time window of \(\pm500\) s centered around the GW detection time. A total of five candidates were found for all three GW150914, GW151226 and GW170104. This is consistent with the number of expected solar neutrino and background events. As a result, we have obtained the best current upper limits on the GW event neutrino fluence of all flavors (\(\nu_e, \nu_{\mu}, \nu_{\tau}\)) in the energy range \((0.5 - 5.0)\) MeV.
We describe the Monte Carlo (MC) simulation package of the Borexino detector and discuss the agreement of its output with data. The Borexino MC 'ab initio' simulates the energy loss of particles in ...all detector components and generates the resulting scintillation photons and their propagation within the liquid scintillator volume. The simulation accounts for absorption, reemission, and scattering of the optical photons and tracks them until they either are absorbed or reach the photocathode of one of the photomultiplier tubes. Photon detection is followed by a comprehensive simulation of the readout electronics response. The algorithm proceeds with a detailed simulation of the electronics chain. The MC is tuned using data collected with radioactive calibration sources deployed inside and around the scintillator volume. The simulation reproduces the energy response of the detector, its uniformity within the fiducial scintillator volume relevant to neutrino physics, and the time distribution of detected photons to better than 1% between 100 keV and several MeV. The techniques developed to simulate the Borexino detector and their level of refinement are of possible interest to the neutrino community, especially for current and future large-volume liquid scintillator experiments such as Kamland-Zen, SNO+, and Juno.
We detected the seasonal modulation of the $^7$Be neutrino interaction rate
with the Borexino detector at the Laboratori Nazionali del Gran Sasso in Italy.
The period, amplitude, and phase of the ...observed time evolution of the signal
are consistent with its solar origin, and the absence of an annual modulation
is rejected at 99.99\% C.L. The data are analyzed using three methods: the
sinusoidal fit, the Lomb-Scargle and the Empirical Mode Decomposition
techniques, which all yield results in excellent agreement.
We present the first simultaneous measurement of the interaction rates of \(pp\), \(^7\)Be, and \(pep\) solar neutrinos performed with a global fit to the Borexino data in an extended energy range ...(0.19-2.93)\(\,\)MeV. This result was obtained by analyzing 1291.51\(\,\)days of Borexino Phase-II data, collected between December 2011 and May 2016 after an extensive scintillator purification campaign. We find: rate(\(pp\))\(\,\)=$\,$$134$$\,$$\pm$$\,$$10$$\,\((\)stat\()\)\,$$^{\rm +6}_{\rm -10}$$\,\((\)sys\()\)\,\(cpd/100\)\,\(t, rate(\)^7\(Be)\)\,\(=\)\,$$48.3$$\,$$\pm$$\,$$1.1$$\,\((\)stat\()\)\,$$^{\rm +0.4}_{\rm -0.7}$$\,\((\)sys\()\)\,\(cpd/100\)\,\(t, and rate(\)pep\()\)\,\(=\)\,$$2.43$$\pm$$\,$$0.36$$\,\((\)stat\()\)^{+0.15}_{-0.22}$$\,\((\)sys\()\)\,\(cpd/100\)\,\(t. These numbers are in agreement with and improve the precision of our previous measurements. In particular, the interaction rate of \)^7\(Be \)\nu\('s is measured with an unprecedented precision of 2.7%, showing that discriminating between the high and low metallicity solar models is now largely dominated by theoretical uncertainties. The absence of \)pep\( neutrinos is rejected for the first time at more than 5\)\,$$\sigma\(. An upper limit of \)8.1$$\,\(cpd/100\)\,\(t (95%\)\,\(C.L.) on the CNO neutrino rate is obtained by setting an additional constraint on the ratio between the \)pp\( and \)pep\( neutrino rates in the fit. This limit has the same significance as that obtained by the Borexino Phase-I (currently providing the tightest bound on this component), but is obtained by applying a less stringent constraint on the \)pep\( \)\nu$ flux.
We detected the seasonal modulation of the \(^7\)Be neutrino interaction rate with the Borexino detector at the Laboratori Nazionali del Gran Sasso in Italy. The period, amplitude, and phase of the ...observed time evolution of the signal are consistent with its solar origin, and the absence of an annual modulation is rejected at 99.99\% C.L. The data are analyzed using three methods: the sinusoidal fit, the Lomb-Scargle and the Empirical Mode Decomposition techniques, which all yield results in excellent agreement.
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