Recent development on the realization of a 1-inch VSiPMT prototype

The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design for a revolutionary hybrid photodetector. The idea, born with the purpose to use a SiPM for large detection volumes, consists in replacing the classical dynode chain with a SiPM. In this configuration, we match the large sensitive area of a photocathode with the performances of the SiPM technology, which therefore acts like an electron detector and so like a current amplifier. The excellent photon counting capability, fast response, low power consumption and great stability are among the most attractive features of the VSiPMT. In order to realize such a device we first studied the feasibility of this detector both from theoretical and experimental point of view, by implementing a Geant4-based simulation and studying the response of a special non-windowed MPPC by Hamamatsu with an electron beam. Thanks to this result Hamamatsu realized two VSiPMT industrial prototypes with a photocathode of 3mm diameter. We present the progress on the realization of a 1-inch prototype and the preliminary tests we are performing on it

Study of nuclear structure of 13C and 20Ne by low energy nuclear reactions

We report some recent experimental results on the spectroscopy of 13C and 20Ne nuclei by means of low energy nuclear reactions carried out with high resolution electrostatic accelerators. In the case of 13C we investigated the possible existence of a-cluster states above the a emission threshold by means of low energy elastic resonant scattering α+9Be in direct kinematics. Excitation functions show the presence of various resonances that have been reproduced by R-matrix fit. We studied also the structure of 20Ne by means of the 19F(p,α0) reaction at sub-barrier energies. The spectroscopy of 20Ne excited states in the region Ex 13.5-14.0 MeV can be probed by analyzing experimental angular distributions and excitation functions. This reaction plays an important role also in the CNOF cycle and is an important ingredient to describe hydrogen-induced destruction of fluorine in massive stars. For this reason we investigated the trend of S-factor, that has been compared with results previously reported in the literature. © Published under licence by IOP Publishing Lt

First Measurement of the He3+He3-->He4+2p Cross Section down to the Lower Edge of the Solar Gamow Peak

We give the LUNA results on the cross section measurement of a key reaction of the proton-proton chain strongly affecting the calculated neutrino luminosity from the Sun: He3+He3-->He4+2p. Due to the cosmic ray suppression provided by the Gran Sasso underground laboratory it has been possible to measure the cross section down to the lower edge of the solar Gamow peak, i.e. as low as 16.5 keV centre of mass energy. The data clearly show the cross section increase due to the electron screening effect but they do not exhibit any evidence for a narrow resonance suggested to explain the observed solar neutrino flux.Comment: 5 pages, RevTeX, and 2 figures in PostScript Submitted for publicatio

The VSiPMT project

Photon detection is a key factor to study many physical processes in several areas of fundamental physics research. Focusing the attention on photodetectors for particle astrophysics, the future experiments aimed at the study of very high-energy or extremely rare phenomena (e.g. dark matter, proton decay, neutrinos from astrophysical sources) will require additional improvements in linearity, gain, quantum efficiency and single photon counting capability. To meet the requirements of this class of experiments, we propose a new design for a modern hybrid photodetector: the VSiPMT (Vacuum Silicon PhotoMultiplier Tube). The idea is to replace the classical dynode chain of a PMT with a SiPM, which therefore acts as an electron detector and amplifier. The aim is to match the large sensitive area of a photocathode with the performances of the SiPM technology. We now present the preliminary study we are performing to realize a 3-inches VSiPMT prototype

The NUMEN Project: Toward new experiments with high-intensity beams

The search for neutrinoless double-beta (0νββ) decay is currently a key topic in physics, due to its possible wide implications for nuclear physics, particle physics, and cosmology. The NUMEN project aims to provide experimental information on the nuclear matrix elements (NMEs) that are involved in the expression of 0νββ decay half-life by measuring the cross section of nuclear double-charge exchange (DCE) reactions. NUMEN has already demonstrated the feasibility of measuring these tiny cross sections for some nuclei of interest for the 0νββ using the superconducting cyclotron (CS) and the MAGNEX spectrometer at the Laboratori Nazionali del Sud (LNS.) Catania, Italy. However, since the DCE cross sections are very small and need to be measured with high sensitivity, the systematic exploration of all nuclei of interest requires major upgrade of the facility. R&D for technological tools has been completed. The realization of new radiation-tolerant detectors capable of sustaining high rates while preserving the requested resolution and sensitivity is underway, as well as the upgrade of the CS to deliver beams of higher intensity. Strategies to carry out DCE cross-section measurements with high-intensity beams were developed in order to achieve the challenging sensitivity requested to provide experimental constraints to 0νββ NMEs

Evidence for a vector charmonium-like state in e+e−→Ds+Ds2∗(2573)−+c.c.e^+e^- \to D^+_sD^*_{s2}(2573)^-+c.c.

We report the measurement of $e^+e^- \to D^+_sD^*_{s2}(2573)^-+c.c.$ via initial-state radiation using a data sample of an integrated luminosity of 921.9 fb$^{-1}$ collected with the Belle detector at the $\Upsilon(4S)$ and nearby. We find evidence for an enhancement with a 3.4$\sigma$ significance in the invariant mass of $D^+_sD^*_{s2}(2573)^- +c.c.$ The measured mass and width are $(4619.8^{+8.9}_{-8.0}({\rm stat.})\pm2.3({\rm syst.}))~{\rm MeV}/c^{2}$ and $(47.0^{+31.3}_{-14.8}({\rm stat.})\pm4.6({\rm syst.}))~{\rm MeV}$, respectively. The mass, width, and quantum numbers of this enhancement are consistent with the charmonium-like state at 4626 MeV/$c^2$ recently reported by Belle in $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ The product of the $e^+e^-\to D^+_sD^*_{s2}(2573)^-+c.c.$ cross section and the branching fraction of $D^*_{s2}(2573)^-\to{\bar D}^0K^-$ is measured from $D^+_sD^*_{s2}(2573)^-$ threshold to 5.6 GeV.Comment: 9 pages, 4 figure

Measurement of the Branching Fraction of the Decay B+→π+π−ℓ+νℓ\boldsymbol{B^{+}\to\pi^{+}\pi^{-}\ell^{+}\nu_\ell} in Fully Reconstructed Events at Belle

We present an analysis of the exclusive $B^{+}\to\pi^{+}\pi^{-}\ell^{+}\nu_{\ell}$ decay, where $\ell$ represents an electron or a muon, with the assumption of charge-conjugation symmetry and lepton universality. The analysis uses the full $\Upsilon(4S)$ data sample collected by the Belle detector, corresponding to 711 fb$^{-1}$ of integrated luminosity. We select the events by fully reconstructing one $B$ meson in hadronic decay modes, subsequently determining the properties of the other $B$ meson. We extract the signal yields using a binned maximum-likelihood fit to the missing-mass squared distribution in bins of the invariant mass of the two pions or the momentum transfer squared. We measure a total branching fraction of ${{\cal B}(B^{+}\to \pi^{+}\pi^{-}\ell^{+}\nu_{\ell})= [22.7 ^{+1.9}_{-1.6} (\mathrm{stat}) \pm 3.5(\mathrm{syst}) ]\times 10^{-5}}$, where the uncertainties are statistical and systematic, respectively. This result is the first reported measurement of this decay.Comment: 23 pages, 19 figure

Measurement of the CKM Matrix Element ∣Vcb∣|V_{cb}| from B0→D∗−ℓ+νℓB^{0} \to D^{*-} \ell^+ \nu_\ell at Belle

We present a new measurement of the CKM matrix element $|V_{cb}|$ from $B^{0} \to D^{*-} \ell^+ \nu_\ell$ decays, reconstructed with the full Belle data set of $711 \, \rm fb^{-1}$ integrated luminosity. Two form factor parameterizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product $\mathcal{F}(1)\eta_{\rm EW}|V_{cb}|$ and the decay form factors, where $\mathcal{F}(1)$ is the normalization factor and $\eta_{\rm EW}$ is a small electroweak correction. In the CLN parameterization we find $\mathcal{F}(1)\eta_{\rm EW}|V_{cb}| = (35.06 \pm 0.15 \pm 0.56) \times 10^{-3}$, $\rho^{2}=1.106 \pm 0.031 \pm 0.007$, $R_{1}(1)=1.229 \pm 0.028 \pm 0.009$, $R_{2}(1)=0.852 \pm 0.021 \pm 0.006$. For the BGL parameterization we obtain $\mathcal{F}(1)\eta_{\rm EW}|V_{cb}|= (34.93 \pm 0.23 \pm 0.59)\times 10^{-3}$, which is consistent with the World Average when correcting for $\mathcal{F}(1)\eta_{\rm EW}$. The branching fraction of $B^{0} \to D^{*-} \ell^+ \nu_\ell$ is measured to be $\mathcal{B}(B^{0}\rightarrow D^{*-}\ell^{+}\nu_{\ell}) = (4.90 \pm 0.02 \pm 0.16)\%$. We also present a new test of lepton flavor universality violation in semileptonic $B$ decays, $\frac{{\cal B }(B^0 \to D^{*-} e^+ \nu)}{{\cal B }(B^0 \to D^{*-} \mu^+ \nu)} = 1.01 \pm 0.01 \pm 0.03~$. The errors correspond to the statistical and systematic uncertainties respectively. This is the most precise measurement of $\mathcal{F}(1)\eta_{\rm EW}|V_{cb}|$ and form factors to date and the first experimental study of the BGL form factor parameterization in an experimental measurement

Dalitz analysis of D0 →k-π+η decays at Belle

© 2020 authors. We present the results of the first Dalitz plot analysis of the decay D0→K-π+η. The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb-1 collected by the Belle detector at the asymmetric-energy e+e- KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels K̄∗(892)0η, K-a0(980)+, K-a2(1320)+, K̄∗(1410)0η, K∗(1680)-π+ and K2∗(1980)-π+, together with Kπ and Kη S-wave components. The decays K∗(1680)-→K-η and K2∗(1980)-→K-η are observed for the first time. We measure ratio of the branching fractions, B(D0→K-π+η)B(D0→K-π+)=0.500±0.002(stat)±0.020(syst)±0.003(BPDG). Using the Dalitz fit result, the ratio B(K∗(1680)→Kη)B(K∗(1680)→Kπ) is measured to be 0.11±0.02(stat)-0.04+0.06(syst)±0.04(BPDG); this is much lower than the theoretical expectations (≈1) made under the assumption that K∗(1680) is a pure 13D1 state. The product branching fraction B(D0→[K2∗(1980)-→K-η]π+)=(2.2-1.9+1.7)×10-4 is determined. In addition, the πη′ contribution to the a0(980)± resonance shape is confirmed with 10.1σ statistical significance using the three-channel Flatté model. We also measure B(D0→K̄∗(892)0η)=(1.41-0.12+0.13)%. This is consistent with, and more precise than, the current world average (1.02±0.30)%, deviates with a significance of more than 3σ from the theoretical predictions of (0.51-0.92)%