Barbara Ricci

• Researcher at University of Ferrara and Istituto Nazionale di Fisica Nucleare

JUNO is a huge neutrino detector that will use 20 kton of organic liquid scintillator as its detection medium. The scintillator is a mixture of linear alkyl benzene (LAB), 2.5 g/L of 2,5-diphenyloxazole (PPO) and 3 mg/L of 1,4-Bis(2-methylstyryl)benzene (Bis-MSB). The main goal of JUNO is to determine the Neutrino Mass Ordering [1,2,3]. In order to...

JUNO is a huge neutrino detector that will use 20 kton of organic liquid scintillator as its detection medium. The scintillator is a mixture of linear alkyl benzene (LAB), 2.5 g/L of 2,5-diphenyloxazole (PPO) and 3 mg/L of 1,4-Bis(2-methylstyryl)benzene (Bis-MSB). The main goal of JUNO is to determine the Neutrino Mass Ordering [1, 2, 3]. In order...

Several neutrino detectors, KamLAND, Daya Bay, Double Chooz, RENO, and the forthcoming large-scale JUNO, rely on liquid scintillator to detect reactor antineutrino interactions. In this context, inverse beta decay represents the golden channel for antineutrino detection, providing a pair of correlated events, thus a strong experimental signature to...

Nuclear reactors are a source of electron antineutrinos due to the presence of unstable fission products that undergo \(\beta ^-\) decay. They will be exploited by the JUNO experiment to determine the neutrino mass ordering and to get very precise measurements of the neutrino oscillation parameters. This requires the reactor antineutrino spectrum t...

Several neutrino detectors, KamLAND, Daya Bay, Double Chooz, RENO, and the forthcoming large-scale JUNO, rely on liquid scintillator to detect reactor antineutrino interactions. In this context, inverse beta decay represents the golden channel for antineutrino detection, providing a pair of correlated events, thus a strong experimental signature to...

The optical and radiochemical purification of the scintillating liquid, which will fill the central detector of the JUNO experiment, plays a crucial role in achieving its scientific goals. Given its gigantic mass and dimensions and an unprecedented target value of about 3% @ 1 MeV in energy resolution, JUNO has set severe requirements on the parame...

In the field of rare event physics, it is common to have huge masses of organic liquid scintillator as detection medium. In particular, they are widely used to study neutrino properties or astrophysical neutrinos. Thanks to its safety properties (such as low toxicity and high flash point) and easy scalability, linear alkyl benzene is the most commo...

This paper describes a design of an FPGA implementation of a Clock and Data Recovery (CDR) system. The core will be integrated in the FPGA configuration for the front-end electronics board of the Jiangmen Underground Neutrino Observatory (JUNO) experiment. The front-end will be placed on the main detector, underground and underwater, making the ele...

Borexino is a 280-ton liquid scintillator detector located at the Laboratori Nazionali del Gran Sasso (LNGS), Italy and is one of the two detectors that has measured geoneutrinos so far. The unprecedented radio-purity of the scintillator, the shielding with highly purified water, and the placement of the detector at a 3800 m w.e. depth have resulte...

Borexino is a 280-ton liquid scintillator detector located at the Laboratori Nazionali del Gran Sasso (LNGS), Italy and is one of the two detectors that has measured geoneutrinos so far. The unprecedented radio-purity of the scintillator, the shielding with highly purified water, and the placement of the detector at a 3800 m w.e. depth have resulte...

In this work, the $^{222}$Rn contamination mechanisms on acrylic surfaces have been investigated. $^{222}$Rn can represent a significant background source for low-background experiments, and acrylic is a suitable material for detector design thanks to its purity and transparency. Four acrylic samples have been exposed to a $^{222}$Rn rich environme...

This paper presents a geoneutrino measurement using 3262.74 days of data taken with the Borexino detector at LNGS in Italy. By observing $52.6 ^{+9.4}_{-8.6} ({\rm stat}) ^{+2.7}_{-2.1}({\rm sys})$ geoneutrinos (68% interval) from $^{238}$U and $^{232}$Th, a signal of $47.0^{+8.4}_{-7.7}\,({\rm stat)}^{+2.4}_{-1.9}\,({\rm sys})$ TNU with $^{+18.3}_...

Gravimetric methods are expected to play a decisive role in geophysical modeling of the regional crustal structure applied to geoneutrino studies. GIGJ (GOCE Inversion for Geoneutrinos at JUNO) is a 3‐D numerical model constituted by ~46 × 10³ voxels of 50 × 50 × 0.1 km, built by inverting GOCE (Gravity field and steady‐state Ocean Circulation Expl...

Clock synchronization procedures are mandatory in most physical experiments where event fragments are readout by spatially dislocated sensors and must be glued together to reconstruct key parameters (e.g. energy, interaction vertex etc.) of the process under investigation. These distributed data readout topologies rely on an accurate time informati...

This paper describes the design, construction principles and operations of the distillation and stripping pilot plants tested at the Daya Bay Neutrino Laboratory, with the perspective to adapt these processes, system cleanliness and leak-tightness standards to the final full scale plants to be used for the purification of the liquid scintillator of...

This paper describes the design, construction principles and operations of the distillation and stripping pilot plants tested at the Daya Bay Neutrino Laboratory, with the perspective to adapt this processes, system cleanliness and leak-tightness to the final full scale plants that will be used for the purification of the liquid scintillator used i...

Gravimetric methods are expected to play a decisive role in geophysical modeling of the regional crustal structure applied to geoneutrino studies. GIGJ (GOCE Inversion for Geoneutrinos at JUNO) is a 3D numerical model constituted by ~46 x 10$^{3}$ voxels of 50 x 50 x 0.1 km, built by inverting gravimetric data over the 6{\deg} x 4{\deg} area center...

Clock synchronization procedures are mandatory in most physical experiments where event fragments are readout by spatially dislocated sensors and must be glued together to reconstruct key parameters (e.g. energy, interaction vertex etc.) of the process under investigation. These distributed data readout topologies rely on an accurate time informati...

Large-area PhotoMultiplier Tubes (PMT) allow to efficiently instrument Liquid Scintillator (LS) neutrino detectors, where large target masses are pivotal to compensate for neutrinos' extremely elusive nature. Depending on the detector light yield, several scintillation photons stemming from the same neutrino interaction are likely to hit a single P...

Large-area PhotoMultiplier Tubes (PMT) allow to efficiently instrument Liquid Scintillator (LS) neutrino detectors, where large target masses are pivotal to compensate for neutrinos' extremely elusive nature. Depending on the detector light yield, several scintillation photons stemming from the same neutrino interaction are likely to hit a single P...

In the heart of the Creighton Mine near Sudbury (Canada), the SNO+ detector is foreseen to observe almost in equal proportion electron antineutrinos produced by U and Th in the Earth and by nuclear reactors. SNO+ will be the first long baseline experiment to measure a reactor signal dominated by CANDU cores ($\sim$55\% of the total reactor signal),...

In the heart of the Creighton Mine near Sudbury (Canada), the SNO+ detector is foreseen to observe almost in equal proportion electron antineutrinos produced by U and Th in the Earth and by nuclear reactors. SNO+ will be the first long baseline experiment to measure a reactor signal dominated by CANDU cores (~55% of the total reactor signal), which...

We review the geoneutrino measurement with Borexino from 2056 days of data taking.

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purpose underground liquid scintillator detector, was proposed with the determination of the neutrino mass hierarchy (MH) as a primary physics goal. The excellent energy resolution and the large fiducial volume anticipated for the JUNO detector offer exciting opportunities for ad...

We present a 1353 days measurement of the geo–neutrino flux in Borexino: the signal was found to be 14.3 ± 4.4 events. This result translates into Sgeo = (38.8 ± 12.0) TNU when a Th/U fixed chondritic mass ratio of 3.9 is assumed. Furthermore Borexino data are compatible with a mantle geo–neutrino signal of (15.4 ± 12.3) TNU.

Constraints on the Earth’s composition and on its radiogenic energy budget come from the detection of geoneutrinos. The Kamioka Liquid scintillator Antineutrino Detector (KamLAND) and Borexino experiments recently reported the geoneutrino flux, which reflects the amount and distribution of U and Th inside the Earth. The Jiangmen Underground Neutrin...

The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine the neutrino mass hierarchy using an underground liquid scintillator detector. It is located 53 km away from both Yangjiang and Taishan Nuclear Power Plants in Guangdong, China. The experimental hall, spanning more than 50 meters, is under a granite mountain of over 700 m...

We report an improved geo-neutrino measurement with Borexino from 2056 days of data taking. The present exposure is $(5.5\pm0.3)\times10^{31}$ proton$\times$yr. Assuming a chondritic Th/U mass ratio of 3.9, we obtain $23.7 ^{+6.5}_{-5.7} (stat) ^{+0.9}_{-0.6} (sys)$ geo-neutrino events. The null observation of geo-neutrinos with Borexino alone has...

In this paper, we discuss some aspects of solar physics from the standpoint of the so-called chameleon fields (i.e. quantum fields, typically scalar, where the mass is an increasing function of the matter density of the environment). Firstly, we analyze the effects of a chameleon-induced deviation from standard gravity just below the surface of the...

Geo-neutrinos, electron anti-neutrinos produced in beta-decays of naturally occurring radioactive isotopes in the Earth, are a unique direct probe of our planet's interior. After a brief introduction about the Earth, the geo-neutrinos' properties and the main aims of their study are discussed. An overview of the latest experimental results obtained...

Antineutrinos produced at nuclear reactors constitute a severe source of background for the detection of geoneutrinos, which bring to the Earth's surface information about natural radioactivity in the whole planet. In this framework we provide a reference worldwide model for antineutrinos from reactors, in view of reactors operational records yearl...

Borexino is a unique detector able to perform measurement of solar neutrinos fluxes in the energy region around 1 MeV or below due to its low level of radioactive background. It was constructed at the LNGS underground laboratory with a goal of solar $^{7}$Be neutrino flux measurement with 5\% precision. The goal has been successfully achieved marki...

We present an updated estimate of reactor antineutrino signal all over the world, with particular attention to the sites proposed for existing and future geo-neutrino experiment. In our calculation we take into account the most updated data on Thermal Power for each nuclear plant, on reactor antineutrino spectra and on three neutrino oscillation me...

We present a measurement of the geo--neutrino signal obtained from 1353 days of data with the Borexino detector at Laboratori Nazionali del Gran Sasso in Italy. With a fiducial exposure of (3.69 $\pm$ 0.16) $\times$ $10^{31}$ proton $\times$ year after all selection cuts and background subtraction, we detected (14.3 $\pm$ 4.4) geo-neutrino events a...

Geo-neutrinos, electron anti-neutrinos produced in β decays of naturally occurring radioactive isotopes in the Earth, are a unique direct probe of our planet's interior. We report the first observation at more than 3σ C.L. of geo-neutrinos, performed with the Borexino detector at Laboratori Nazionali del Gran Sasso. Anti-neutrinos are detected thro...

We present a new approach to study the properties of the sun. We consider small variations of the physical and chemical properties of the sun with respect to Standard Solar Model predictions and we linearize the structure equations to relate them to the properties of the solar plasma. By assuming that the (variation of) the present solar compositio...

Earth shines in antineutrinos produced from long-lived radioactive elements: detection of this signal can provide a direct test of the Bulk Silicate Earth (BSE) model and fix the radiogenic contribution to the terrestrial heat flow. In this paper we present a systematic approach to geo-neutrino production based on global mass balance, supplemented...

We discuss the implications of KamLAND result on geo-neutrinos for the radiogenic contribution of Uranium to terrestrial heat. We also discuss the potential of future experiments for assessing the amount of Uranium and Thorium in different reservoirs (crust, mantle and core) of the Earth.

Recent analyses of solar spectroscopic data (see Asplund, Grevesse & Sauval 2005 and references therein) suggest a significative variation of the heavy element abundance. The change of the heavy mixture might affect the determination of the cluster ages for two different reasons: the change of theoretical isochrones at fixed metallicity and the var...

Earth shines in antineutrinos produced from long-lived radioactive elements: detection of this signal can provide a direct test of the Bulk Silicate Earth (BSE) model and fix the radiogenic contribution to the terrestrial heat flow. In this paper we present a systematic approach to geo-neutrino production based on global mass balance, supplemented...

We find that recent results from the KamLAND Collaboration on geologically produced antineutrinos, N(U+Th)=28-15+16 events, correspond to a radiogenic heat production from uranium and thorium decay chains H(U+Th)=38-33+35 TW. The 99% confidence limit on the geo-neutrino signal translates into the upper bound H(U+Th)<162 TW, which is much weaker tha...

Recent analyses of solar spectroscopic data (see Asplund, Grevesse & Sauval 2004 and references therein) suggest a significative variation of the heavy elements abundance. The change of heavy mixture might affect the determination of the clusters age for two different reasons: the change of theoretical isochrones at fixed metallicity and the variat...

We discuss implications of a new measurement of $^{14}N(p, \gamma)^{15}O$ concerning solar neutrinos, solar models and globular cluster dating. Predictions for the gallium and chlorine experiments are reduced by 2 and 0.1 SNU respectively. Predictions for helioseismic observables are unchanged within uncertainties. The age of globular clusters as d...

We discuss the possibility of studying nuclear reactions in the sun by means of solar neutrinos and helioseismology. In particular we review the observational information which is available on the energy source of the sun, cross sections and screening in the solar interior.

In this brief review we discuss the possibility of studying the solar interior by means of neutrinos, in the light of the enormous progress of neutrino physics in the last few years. The temperature near the solar center can be extracted from Boron neutrino experiments as: $ T= (1.57 \pm 0.01) 10^7 K$. The energy production rate in the Sun from pp...

Order of magnitude estimates of radiogenic heat and antineutrino production are given, using the San Marco cathedral as an example. Prospects of determining the radiogenic contribution to terrestrial heat by detection of antineutrinos from natural radioactivity (geoneutrinos) are discussed. A three kton scintillator detector in three years can clea...

We comment on the first indication of geo-neutrino events from KamLAND and on the prospects for understanding Earth energetics. Practically all models of terrestrial heat production are consistent with data within the presently limited statistics, the fully radiogenic model being closer to the observed value (≈9 geo-events). In a few years KamLAND...

We estimate terrestrial antineutrino and neutrino fluxes according to different models of Earth composition. We find large variations, corresponding to uncertainties on the estimated U, Th and K abundances in the mantle. Information on the mantle composition can be derived from antineutrino flux measurements after subtracting the crust contribution...

We review the observational information on the constancy of the fine structure constant alpha. We find that small improvements on the measurement of 187Re lifetime can provide significant progress in exploring the range of variability suggested by QSO data. We also discuss the effects of a time varying alpha on stellar structure and evolution. We f...

We comment on the first indication of geo-neutrino events from KamLAND and on the prospects for understanding Earth energetics. Practically all models of terrestrial heat production are consistent with data within the presently limited statistics, the fully radiogenic model being closer to the observed value ($\approx 9$ geo-events). In a few years...

We estimate terrestrial antineutrino and neutrino fluxes according to different models of Earth composition. We find large variations, corresponding to uncertainties on the estimated $U$, $Th$ and $K$ abundances in the mantle. Information on the mantle composition can be derived from antineutrino flux measurements after subtracting the crust contri...

Experimental results for sub-barrier nuclear fusion reactions show cross section enhancements with respect to bare nuclei which are generally larger than those expected according to electron screening calculations. We point out that energy spread of target or projectile nuclei is a mechanism which generally provides fusion enhancement. We present a...

We review the observational information on the constancy of the fine structure constant alpha. We find that small improvements on the measurement of ^{187}Re lifetime can provide significant progress in exploring the range of variability suggested by QSO data. We also discuss the effects of a time varying alpha on stellar structure and evolution. W...

We investigate whether present data on helioseismology and solar neutrino fluxes may constrain WIMP--matter interactions in the range of WIMP parameters under current exploration in WIMP searches. We find that, for a WIMP mass of 30 GeV, once the effect of the presence of WIMPs in the Sun's interior is maximized, the squared isothermal sound speed...

Several properties of the solar interior are determined with a very high accuracy, which in some cases is comparable to that achieved in the determination of the Newton constant $G_N$. We find that the present uncertainty $\Delta G_N/G_N=\pm 1.5\cdot 10^{-3}$ has significant effects on the profile of density and pressure, however it has negligible...

By combining the results of SNO and Super-Kamiokande one can derive—in the absence of sterile neutrinos—the total neutrino flux produced from 8B decay in the Sun. We use this information to check the accuracy of several input parameters of solar model calculations. Opacity and p–p fusion cross section are constrained by the 8B flux measurement to t...

The comparison of the SNO charged current result with the solar neutrino signal measured by Super-Kamiokande has provided, for the first time, the evidence of a non electron flavour active neutrino component in the solar flux. We remark here that this evidence can be obtained in a model independent way, i.e. without any assumpion about solar models...

We show that helioseismology provides information on Beryllium neutrino production in the Sun. In particular, we derive a lower limit on the Beryllium neutrino flux on earth, ΦminBe = 1 · 109 cm−2s−1, in the absence of oscillations, by using helioseismic data, the B-neutrino flux measured by Superkamiokande and the hydrogen abundance at the solar c...

We review recent advances concerning helioseismology, solar models and solar neutrinos. Particularly we address the following points: i) helioseismic tests of recent SSMs; ii) predictions of the Beryllium neutrino flux based on helioseismology; iii) helioseismic tests regarding the screening of nuclear reactions in the Sun. Comment: 7 pages with 6...

We review recent advances concerning helioseismology, solar models and solar neutrinos. Particularly we address the following points: i) helioseismic tests of recent SSMs; ii) predictions of the Beryllium neutrino flux based on helioseismology; iii) helioseismic tests regarding the screening of nuclear reactions in the Sun.

We show that models for screening of nuclear reactions in the Sun can be tested by means of helioseismology. As well known, solar models using the weak screening factors are in agreement with data. We find that the solar model calculated with the anti-screening factors of Tsytovich is not consistent with helioseismology, both for the sound speed pr...

We provide a determination of the Beryllium neutrino luminosity directly by means of helioseismology, without using additional assumptions. We have constructed solar models where Beryllium neutrino, ($\nu_{Be}$) production is artificially changed by varying in an arbitrary way the zero energy astrophysical S-factor $S_{34}$ for the reaction $^3{\rm...

We discuss in detail the information on large extra dimensions which can be derived in the framework of stellar evolution theory and observation. The main effect of large extra dimensions arises from the production of the Kaluza-Klein (KK) excitations of the graviton. The KK-graviton and matter interactions are of gravitational strength, so the KK...

We discuss in detail the information on large extra dimensions which can be derived in the framework of stellar evolution theory and observation. The main effect of large extra dimensions arises from the production of the Kaluza-Klein (KK) excitations of the graviton. The KK-graviton and matter interactions are of gravitational strength, so the KK...

Low-energy cross section data for 86 charged-particle induced reactions involving light (1 ⩽ Z ⩽ 14), mostly stable, nuclei are compiled. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 106 K to 1010 K are calculated. These evaluations assume either that the...

We review recent advances concerning helioseismology, solar models and solar neutrinos. Particularly we shall address the following points: i) helioseismic tests of recent SSMs; ii) the accuracy of the helioseismic determination of the sound speed near the solar center; iii) predictions of neutrino fluxes based on helioseismology, (almost) independ...

We derive a lower limit on the Beryllium neutrino flux on earth, $\Phi(Be)_{min} = 1\cdot 10^9 cm^{-2} s^{-1}$, in the absence of oscillations, by using helioseismic data, the B-neutrino flux measured by Superkamiokande and the hydrogen abundance at the solar center predicted by Standard Solar Model (SSM) calculations. We emphasize that this abunda...

The excess of highest energy solar-neutrino events recently observed by Superkamiokande can be in principle explained by anomalously high hep-neutrino flux Φν(hep). Without using SSM calculations, from the solar luminosity constraint we derive that Φν(hep)/S13 cannot exceed the SSM estimate by more than a factor three. If one makes the additional h...

Nuclear reactions in stars occur between nuclei in the high-energy tail of the energy distribution and are sensitive to possible deviations from the standard equilibrium thermal-energy distribution. We are able to derive strong constraints on such deviations by using the detailed helioseismic information of the solar structure. If a small deviation...

The problem of measuring the solar age by means of helioseismology hasbeen recently revisited by Guenther & Demarque (1997) and by Weiss & Schlattl (1998). Different best values for $t_{\rm seis}$ and different assessment of the uncertainty resulted from these two works. We show that depending on the way seismic data are used, one may obtain the va...

The excess of highest energy solar-neutrino events recently observed by Superkamiokande can be in principle explained by anomalously high $hep$-neutrino flux $\Phi_{\nu}(hep)$. Without using SSM calculations, from the solar luminosity constraint we derive that $\Phi_\nu(hep)/S_{13}$ cannot exceed the SSM estimate by more than a factor three. If one...

We present a quantitative estimate of the accuracy of the calculated diffusion coefficients, by comparing predictions of solar models with observational data provided by helioseismology. By taking into account the major uncertainties in building solar models we conclude that helioseismology confirms the diffusion efficiency adopted in SSM calculati...

Nuclear reactions in stars occur between nuclei in the high-energy tail of the energy distribution and are sensitive to possible deviations from the standard equilibrium thermal-energy distribution. We are able to derive strong constraints on such deviations by using the detailed helioseismic information of the solar structure. If a small deviation...

We consider a wide class of solar models with mixed core. Most of these models can be excluded as the sound speed profile that they predict is in sharp disagreement with helioseismic constraints. All the remaining models predict 8B and/or 7Be neutrino fluxes of at least as large as those of SSMs. In conclusion, helioseismology shows that a mixed so...

We summarize the results of solar neutrino experiments and update a solar model independent analysis of solar neutrino data. We discuss the implications of helioseismology on solar models and predicted solar neutrino fluxes. Finally , we discuss the potential of new experiments for detecting specific signatures of the proposed solutions to the sola...

We present our results concerning a systematical analysis of helioseismic implications on solar structure and neutrino production. We find Y$_{ph}=0.238-0.259$, $R_b/R_\odot=0.708-0.714$ and $\rho_b=(0.185-0.199)$ gr/cm$^3$. In the interval $0.2<R/R_\odot<0.65$, the quantity $U=P/\rho$ is determined with and accuracy of $\pm 5$\permille~or better....

By using a phenomenological field theory of nucleon-nucleon interactions, Oberhummer et al. found a cross section of p+p --> d + e+ + νe about 2.9 times that given by the potential approach and adopted in Standard Solar Model calculations. We show that a solar model with S=2.9SSSM is inconsistent with helioseismic data, the difference between model...

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We consider a wide class of solar models with mixed core. Most of these models can be excluded as the predicted sound speed profile is in sharp disagreement with helioseismic constraints. All the remaining models predict $^7$Be and/or $^7$B neutrino fluxes at least as large as those of SSMs. In conclusion, helioseismology shows that a mixed solar c...

The central solar temperature T and its uncertainties are calculated in helioseismologically-constrained solar models. From the best fit to the convective radius, density at the convective radius and seismically determined helium abundance the central temperature is found to be T = 1.58 × 107 K, in excellent agreement with Standard Solar Models. Co...

By using a phenomenological field theory of nucleon-nucleon interactions, Oberhummer et al. found a cross section of p+p $\to$ d + e$^+$ + $\nu _e$ about 2.9 times that given by the potential approach and adopted in Standard Solar Model calculations. We show that a solar model with $S=2.9 S_{SSM}$ is inconsistent with helioseismic data, the differe...

The central solar temperature T and its uncertainties are calculated in helioseismologically-constrained solar models. From the best fit to the convective radius, density at the convective radius and seismically determined helium abundance the central temperature is found to be T=1.58x10^7 K, in excellent agreement with Standard Solar Models. Conse...

This question, which often comes in when discussing solar neutrinos, is not clearly analysed in any textbook, to our knowledge. In this note we give a simple estimate of the flow time, also reminding its (ir)relevance to the solar neutrino problem.

After a short survey of the physics of solar neutrinos, giving an overview of hydrogen burning reactions, predictions of standard solar models and results of solar neutrino experiments, we discuss the solar-model-independent indications in favour of non-standard neutrino properties. The experimental results appear to be in contradiction with each o...

We present a systematical analysis of uncertainties in the helioseismological determination of quantities characterizing the solar structure. We discuss the effect of errors on the measured frequencies, the residual solar model dependence and the uncertainties of the inversion method. We find Y_{ph}=0.238-0.259, $R_b/R_\odot=0.708-0.714$ and $\rho_...

Exposure to a 51Cr neutrino source as that used in Gallex will provide an excellent overall performance test of Borexino, which should collect about 1400 source induced events, with an initial rate of about 35 counts per day. This will be particularly important if MSW-small-angle turns out to be the solution of the solar neutrino problem. In additi...

Exposure to a $^{51}$Cr neutrino source as that used in Gallex will provide an excellent overall performance test of Borexino, which should collect about 1400 source induced events, with an initial rate of about 35 counts per day. This will be particularly important if MSW-small-angle turns out to be the solution of the solar neutrino problem. In a...

After a short survey of the physics of solar neutrinos, giving an overview of hydrogen burning reactions, predictions of standard solar models and results of solar neutrino experiments, we discuss the solar-model-independent indications in favour of non-standard neutrino properties. The experimental results look to be in contradiction with each oth...

We present an updated version of our standard solar model (SSM) where helium and heavy elements diffusion is included and the improved OPAL equation of state (Rogers 1994, Rogers Swenson \& Iglesias 1996) is used. In such a way the EOS is consistent with the adopted opacity tables, from the same Livermore group, an occurrence which should further e...

We present an updated version of our standard solar model (SSM) where helium and heavy elements diffusion is included and the improved OPAL equation of state (Rogers 1994, Rogers Swenson \& Iglesias 1996) is used. In such a way the EOS is consistent with the adopted opacity tables, from the same Livermore group, an occurrence which should further e...

In connection with the recent suggestion by Tsytovich et al. that opacity in the solar core could be overestimated, we consider the following questions: i) What would a 10\% opacity reduction imply for the solar neutrino puzzle? ii) Is there any hope of solving the solar neutrino puzzle by changing opacity? iii) Is a 10\% opacity reduction testable...

We extract information on the fluxes of Be and CNO neutrinos directly from solar neutrino experiments, with minimal assumptions about solar models. Next we compare these results with solar models, both standard and non standard ones. Finally we discuss the expectations for Borexino, both in the case of standard and non standard neutrinos.

We extract information on the fluxes of Be and CNO neutrinos directly from solar neutrino experiments, with minimal assumptions about solar models. Next we compare these results with solar models, both standard and non standard ones. Finally we discuss the expectations for Borexino, both in the case of standard and non standard neutrinos.

A variation of Newton's constant $G$ over cosmological time scales would modify the main-squence time of globular cluster (GC) stars. We have calculated the evolution of low-mass stars typical for GCs both for standard non-varying $G$ and under the assumption of a linear variation of $G$. The age of the isochrones resulting from the latter models t...