arXiv subjects

G. Felici

Publications and source records attributed to G. Felici.

At least 19 recordsLinked to original sources

arXiv2026

Measurement of Branching Fraction and Transition Magnetic Moment of the Hyperon Dalitz Decay $\Sigma^0 \rightarrow \Lambda e^+e^-$

Based on a data sample of 10 billion $J/\psi$ events collected with the BESIII detector operating at the BEPCII collider, the Dalitz decay $\Sigma^0 \rightarrow \Lambda e^+e^-$ is studied experimentally for the first time. The $\Sigma^0$ hyperons are produced through the process $J/\psi \rightarrow \Sigma^0\bar{\Sigma}^0$ and analyzed using a double-tag method. The absolute branching fraction is measured to be $\mathcal{B}(\Sigma^0 \rightarrow \Lambda e^+e^-) = (6.34 \pm 0.25_{\rm stat.} \pm 0.23_{\rm syst.}) \times 10^{-3}$. This result shows a $2\sigma$ discrepancy from the theoretical calculation quoted in the PDG, where the uncertainties are statistical and systematic, respectively. In addition to the branching fraction, the transition magnetic moment $\mu$ is determined to be $(1.74 \pm 0.03_{\rm stat.} \pm 0.09_{\rm syst.})\,\mu_N$, where $\mu_N=e/(2m_p)$ represents the nucleon magnetic moment, providing valuable insight into the intrinsic structure of the $\Sigma^0$ hyperon.

hep-ex↗

arXiv2026

Ultra-trace analysis of 40K in organic liquid scintillators

Rare-event searches require exceptionally low background levels, motivating the development of increasingly sophisticated screening methods to push sensitivity limits. Liquid scintillators are particularly attractive detector media due to their intrinsic radiopurity and the ability to scale to large target masses. In this work, we present a screening strategy capable of measuring ultra-trace concentrations of $^{40}\text{K}$ with sensitivities below $10^{-15}$g/g. The method combines neutron activation analysis with a dedicated radiochemical treatment, followed by low-background HPGe gamma spectroscopy. Using this approach, we achieved a minimum detectable concentration of $2.9\cdot10^{-16}$g/g for $^{40}\text{K}$, placing this technique among the most sensitive currently available.

physics.ins-det↗

arXiv2026

Search for an isoscalar partner of the $Z_c(3900)$ in $e^+e^-\to\pi^+\pi^-\eta J/\psi$

Using a data sample corresponding to an integrated luminosity of 20.3 fb$^{-1}$ collected at center-of-mass energies from 4.18 to 4.95 GeV with the BESIII detector, we observe the process $e^+e^-\to\pi^+\pi^-\eta J/\psi$ with a statistical significance of $6.0 \sigma$, including systematic uncertainties. The isoscalar partner of the $Z_c(3900)$, denoted $X(3900)$, is searched for in the $\eta J/\psi$ final state, and no significant signal is observed. The upper limits on the product of the Born cross section $\sigma^{\rm Born}[e^{+}e^{-}\to\pi^{+}\pi^{-} X(3900)$] and the branching fraction $\mathcal{B}[X(3900)\to\eta J/\psi]$ are given with various assumptions for the mass and width of the $X(3900)$.

hep-ex↗

arXiv2026

Search for the charged lepton flavor violating decay $\eta \to e^{\pm}\mu^{\mp}$

Based on $(10.087 \pm 0.044) \times 10^{9}~J/\psi$ events collected at the center-of-mass energy $\sqrt{s} = 3.097$~GeV with the BESIII detector, we search for the charged lepton flavor violating decay $\eta \to e^{\pm}\mu^{\mp}$ through the process $J/\psi \to \gamma \eta'$ with $\eta' \to \pi^{+} \pi^{-} \eta$. No signal is observed, and an upper limit on the branching fraction is determined to be $\mathcal{B}(\eta \to e^{\pm}\mu^{\mp}) < 6.8 \times 10^{-7}$ at the 90\% confidence level. This result improves the previous best limit by one order of magnitude.

hep-ex↗

arXiv2026

Observation of an Altered $a_{0}(980)$ Line shape in $D^{+} \rightarrow \pi^{+}\eta\eta$

Using $20.3~{\rm fb}^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector at $\sqrt{s}=3.773~{\rm GeV}$, we perform the first amplitude analysis of the decay $D^+\to\pi^+\eta\eta$. The intermediate process $D^+\to a_0(980)^+\eta$, $a_0(980)^+\to\pi^+\eta$, is observed as the only significant component in the amplitude analysis, and its branching fraction is measured to be $(3.67\pm0.12_{\rm stat}\pm0.06_{\rm syst})\times10^{-3}$. The $\pi^+\eta$ mass spectrum associated with $a_0(980)^+\eta$ production exhibits a line shape that differs substantially from those observed in $D_{(s)}\to a_0(980)\pi$ and $D^0\to a_0(980)^-e^+\nu_e$ decays. We examine several conventional descriptions of the $a_0(980)$ amplitude, including Flatt\'e, dispersively modified Flatt\'e, $T$-matrix, and $K$-matrix parameterizations. With reference $a_0(980)$ parameters, neither these models nor their extensions including additional small resonant or non-resonant amplitudes reproduce the observed line shape satisfactorily. When the $a_0(980)$ parameters are allowed to float, satisfactory fits can be obtained, but the pole mass is driven well above the $K\bar K$ threshold, inconsistent with the near-threshold character of the $a_0(980)$. The results reveal a tension between fit quality and the physical pole position in conventional direct-production amplitude models.

hep-ex↗

arXiv2026

Updated measurement of the branching fraction of $D_s^+ \to \tau^+ \nu_{\tau}$

Using a dataset of 7.33 fb$^{-1}$ of $e^+ e^-$ annihilation data collected with the BESIII detector at center-of-mass energies from 4.128 to 4.226 GeV, we report an updated measurement of the branching fraction of $D_s^+ \to \tau^+ \nu_{\tau}$ via four $\tau^+$ decay modes: $\tau^+ \to e^+ \nu_e \bar{\nu}_{\tau}$, $\mu^+ \nu_{\mu} \bar{\nu}_{\tau}$, $\pi^+\bar{\nu}_{\tau}$, and $\pi^+ \pi^{0} \bar{\nu}_{\tau}$. The branching fraction is determined to be $\mathcal{B}({D_s^+ \to \tau^+ \nu_{\tau}}) = (5.37 \pm 0.08_{\rm stat} \pm 0.06_{\rm syst})$ %. The product of the modulus of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ and the $D_s^+$ decay constant $f_{D_s^+}$ is measured to be $f_{D_s^+} |V_{cs}| = (248.2 \pm 1.9_{\rm stat} \pm 1.4_{\rm syst} \pm 0.6_{\rm input} \pm 0.8_{\rm EM})$ MeV. Both the branching fraction and the product $f_{D_s^+} |V_{cs}|$ are the most precise results yet obtained. Then, taking $f_{D_s^+}$ from lattice quantum chromodynamics calculations results in $|V_{cs}| = 0.993 \pm 0.008_{\rm stat} \pm 0.006_{\rm syst} \pm 0.003_{\rm input} \pm 0.003_{\rm EM}$. Conversely, one finds $f_{D_s^+} = (255.0 \pm 1.9_{\rm stat} \pm 1.4_{\rm syst} \pm 0.6_{\rm input} \pm 0.8_{\rm EM})$ MeV when taking $|V_{cs}|$ from the CKMfitter group as an input. Combining with the world average value of $D_s^+ \to \mu^+ \nu_{\mu}$, the ratio of the branching fractions between $D_s^+ \to \tau^+ \nu_{\tau}$ and $D_s^+ \to \mu^+ \nu_{\mu}$ is estimated to be $10.04 \pm 0.29$, which is consistent with the Standard Model prediction of lepton flavor universality.

hep-ex↗

arXiv2026

Measurement of the branching fraction of $D_{s}^{*+}\to e^{+}e^{-}D_{s}^{+}$

The branching fraction of the electromagnetic Dalitz decay $D^{*+}_{s}\to e^{+}e^{-}D^{+}_{s}$ is measured with an $e^{+}e^{-}$ collision data sample collected by the BESIII experiment at center-of-mass energies between 4.128 and 4.226 $\mathrm{GeV}$, corresponding to a total integrated luminosity of 7.33 $\mathrm{fb}^{-1}$. The measurement yields the branching fraction ${\mathcal{B}(D^{*+}_{s}\to e^{+}e^{-}D^{+}_{s})=(7.28\pm0.61_{\mathrm{stat}}\pm0.31_{\mathrm{syst}})\times10^{-3}}$. The result is consistent with the previous one, with a 2.5-fold improvement in precision. This provides an important input for constraining the parameters of theoretical models and for determining the absolute branching fractions of $D^{*+}_{s}\to \pi^{0}D^{+}_{s}$ and $D^{*+}_{s}\to \gamma D^{+}_{s}$, measured with a relative method.

hep-ex↗

arXiv2026

Thin single-crystal perovskite detector for high-energy charged particles

The organometal halide perovskites (OMHP) semi-conductors have shown recently a strong potential as radiation detectors, beside the well-known success in photovoltaics and as photo-detectors. Many studies have been published on X-rays detection, and a few studies about detection of alpha, beta-particles and protons. Less literature is present for high energy charged particles. OMHP-based devices for tracking and real-time monitoring for high energy particles may offer many advantages. OMHPs can be directly grown on pixelated electronics, even on curved substrates, without the need of complex and expensive bump-bonding procedures. Moreover, OMHPs have shown self-healing features after radiation exposure, which makes them attractive for high-flux applications. In this paper we report a device based on a thin single OMHP crystal, about 150 mum thick, directly grown on a patterned substrate through dewetting technique, able to detect high-energy charged particles in a high dynamic range of incident fluxes. A dedicated electronics circuit has been developed to match the expected time characteristics of the OMHP crystals. This is the first demonstration of thin OMHP single crystals being able to detect high energy charged particles of hundreds of MeV.

physics.ins-det↗

arXiv2026

Biophoton Emission from Palm during Meditation: A Multi-Method Complexity Analysis

Biophotons are ultra-weak photon emissions in the visible spectrum produced by living organisms. While extensively studied in plants, germinating seeds, and cell cultures, no systematic multi-method complexity analysis of human ultraweak photon emission (UPE) under physiological modulation has been reported. We address this gap by applying a comprehensive analytical framework to UPE measurements from the right palm of a human subject. Three independent sessions were conducted on different days, each comprising four consecutive 15-minute phases: Dark reference, pre-meditation resting state (Pre), structured meditation based on the Sama Vritti box-breathing protocol, and post-meditation recovery (Post). Photon count series are analysed with four complementary methods: distributional statistics (Fano factor, skewness, tail Expected Shortfall); multiscale Fano factor and Allan deviation; stripe-filtered Diffusion Entropy Analysis (DEA); and Renyi entropy with a Time Reversal test. The methods show complementary sensitivities, converging on a coherent picture: a systematic reduction of emission intermittency during meditation, consistently detected across all three sessions. Stripe-filtered DEA places the emission in the non-ergodic renewal regime with a Pre-to-Meditation decrease of the scaling exponent. Renyi analysis reveals two effects: reduced marginal amplitude burstiness (Tdir) and increased sequential pattern structure (Tseq), interpreted as entrainment to the Sama Vritti rhythm. These findings are consistent with cardiac complexity transitions during meditation reported by Tuladhar et al. and with EEG reorganization during Sama Vritti breathing by Zaccaro et al., suggesting a coordinated multi-channel physiological response. The results establish a proof-of-concept framework for complexity analysis of human UPE under physiological modulation.

physics.bio-ph↗

arXiv2026

Measurement of branching fractions of $D^+_s\to K^0_SK^0_S \pi^+\pi^0$ and $D^+_s\to K^0_S K^+\pi^0\pi^0$

By analyzing $e^+e^-$ collision data corresponding to an integrated luminosity of 7.33~fb$^{-1}$ collected with the BESIII detector at center-of-mass energies ranging from 4.128 to 4.226~GeV, we report the observations of the hadronic decays $D^+_s\to K^0_SK^0_S\pi^+\pi^0$ and $D^+_s\to K^0_S K^+\pi^0\pi^0$. Their decay branching fractions are determined to be ${\mathcal B}(D^+_s\to K^0_SK^0_S \pi^+\pi^0)=(4.08\pm0.46_{\rm stat}\pm0.45_{\rm syst})\times 10^{-3}$ and ${\mathcal B}(D^+_s\to K^0_S K^+\pi^0\pi^0)=(3.32\pm0.64_{\rm stat}\pm0.31_{\rm syst})\times 10^{-3}$, where the first uncertainties are statistical and the second are systematic.

hep-ex↗

arXiv2026

First Measurement of the $D_s^+\rightarrow K^{}(892)^0\mu^+\nu_{\mu}$ Decay, Study of Dynamics and Test of Lepton Universality with $D_s^+\rightarrow K^{}(892)^0\ell^+\nu_{\ell}$ Decays

We report the first measurement of the semileptonic decay $D^+_s \rightarrow K^*(892)^0\mu^+\nu_{\mu}$ and an improved measurement of the decay $D^+_s \rightarrow K^*(892)^0 e^+\nu_{e}$ using a sample of $7.33~\mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data collected at center-of-mass energies between 4.128 to 4.226~GeV with the BESIII detector at the BEPCII collider. We measure the branching fractions to be $\mathcal B({D^+_s\rightarrow K^*(892)^0 \mu^+\nu_{\mu}})=(2.07\pm0.22_{\rm stat}\pm0.10_{\rm syst})\times10^{-3}$ and $\mathcal B({D^+_s\rightarrow K^*(892)^0 e^+\nu_{e}})=(2.14\pm0.18_{\rm stat}\pm0.10_{\rm syst})\times10^{-3}$. Based on a simultaneous study of the dynamics in two semileptonic decays, the hadronic form factor parameters in the $D^+_s\rightarrow K^{*}(892)^0$ transition are determined to be $r_{V} = V(0)/A_1(0) = 1.63 \pm 0.14_{\rm stat} \pm 0.08_{\rm syst}$, $r_{2} = A_2(0)/A_1(0) = 0.60 \pm 0.13_{\rm stat} \pm 0.06_{\rm syst}$, and $A_1(0)=0.56 \pm 0.02_{\rm stat} \pm 0.01_{\rm syst}$, where $V(0)$ is the vector form factor and $A_{1,2}(0)$ are the axial-vector form factors evaluated at $q^2=0$. The precision of $r_V$ and $r_2$ is improved by twofold and $A_1(0)$ is measured for the first time. We also report the first model-independent measurements of the differential decay rates and the lepton forward-backward asymmetries for $D^+_s\rightarrow K^{*}(892)^0\ell^+\nu_{\ell}$ decays. Based on these measurements, we perform a test of lepton flavor universality in full and separate $q^2$ intervals with $D^+_s\rightarrow K^{*}(892)^0\ell^+\nu_{\ell}$ decays. No violation is found within uncertainties. Our results present for the first time a complete study of the dynamics in the $D_s^+\rightarrow K^*(892)^0$ transition, and provide stringent tests of various non-perturbative theoretical calculations.

hep-ex↗

arXiv2026

Measurement of the double Dalitz decay $\eta \to e^+e^-e^+e^-$

Using a data sample of $(1.0087 \pm 0.0044) \times {10^{10}}$ $J/{\psi}$ events collected with the BESIII detector, we study the rare double Dalitz decay of $\eta\rightarrow e^+e^-e^+e^-$ through the processes $J/\psi\rightarrow \gamma \eta$ and $J/\psi\rightarrow \gamma \eta' ,\eta' \to \pi^+\pi^-\eta$. Clear $\eta$ signals are observed in the $e^+e^-e^+e^-$ invariant mass spectrum, with statistical significances of 5.9$\sigma$ and 7.8$\sigma$ for the two channels, respectively. By combining both modes, we determine the branching fraction of $\eta\rightarrow e^+ e^- e^+ e^-$ to be $(2.63~\pm~0.34_{\rm stat}~\pm~0.16_{\rm syst}) \times10^{-5}$. The result is consistent with the previous measurements within uncertainties and further constrains physics beyond the standard model.

hep-ex↗

arXiv2026

Performance of the LHCb muon detector in Run 3

In Run 3 of the LHC, the instantaneous luminosity at the LHCb interaction point has been increased by a factor of five, from $4\times 10^{32}\rm{cm}^{-2}\rm{s}^{-1}$ to $2\times 10^{33}\rm{cm}^{-2}\rm{s}^{-1}$. Several hardware interventions, including a complete overhaul of the readout electronics, have been carried out on the muon detector. The muon identification algorithms in the software trigger were improved with the aim of ensuring Run 2 performance under a higher particle rate. The operation and calibration of the upgraded muon detector are presented. The muon detection efficiency and muon identification performance are evaluated on data calibration samples collected during the year 2024. A muon identification efficiency above 90\% with sub-percent hadron misidentification probability is achieved by exploiting the pattern of hits in the muon detector.

hep-ex↗

arXiv2026

First energy scan measurement of $e^{+}e^{-}\to K^{+}K^{-}$ around the $\psi(2S)$ resonance

We report the precise energy scan measurement of the cross section lineshape of $\psi(2S)\to K^{+}K^{-}$. The analysis is based on $e^{+}e^{-}$ collision data corresponding to an integrated luminosity of 495~pb$^{-1}$ collected with the BESIII detector at BEPCII. By analyzing the cross section line-shape, we extract the relative phase $\Phi$ between the strong and electromagnetic amplitudes of the $\psi(2S)$ resonance, a fundamental parameter in charmonium physics, based on the assumption that the relative phase between the electromagnetic amplitude of the $\psi(2S)$ resonance and the continuum is zero. Two distinct solutions for the branching fraction $\mathcal{B}$ of $\psi(2S)\to K^{+}K^{-}$ are observed: a constructive interference solution with $\mathcal{B}=(7.49\pm0.41)\times10^{-5}$ and $\Phi=(110.1 \pm6.7)^\circ$, and a destructive interference solution with $\mathcal{B}=(10.94\pm0.48)\times10^{-5}$ and $\Phi=(-106.8\pm5.7)^\circ$. A significant correlation between $\Phi$ and $\mathcal{B}$ is established, demonstrating that interference effects must be taken into account in the $\psi(2S)$ branching fraction measurements. Additionally, the first results for both the $\psi(2S)$ strong form factor, which characterizes the strong coupling between $\psi(2S)$ and $K^{+}K^{-}$, and the energy-dependent electromagnetic form factor of the charged kaon in this energy region are reported.

hep-ex↗

arXiv2026

Observation of $\Lambda^+_c\to n\pi^+\eta$ and search for $\Lambda^+_c\to na_0(980)^+$

By analysing 6.1 ${\rm fb}^{-1}$ of data collected at center-of-mass energies between $\sqrt{s}=4.600$ and 4.843 $\rm GeV$ with the BESIII detector at the BEPCII collider, we observe the decay $\Lambda_c^+\to n\pi^+\eta$ for the first time with a statistical significance of $9.5\sigma$. The ratio of branching fractions $\mathcal{B}(\Lambda_c^+\to n\pi^+\eta)/\mathcal{B}(\Lambda_c^+\to \Lambda\pi^+\eta)$ is measured to be $0.155\pm0.031_{\rm stat.}\pm0.012_{\rm syst.}$ Taking the world average of $\mathcal{B}(\Lambda_c^+\to \Lambda\pi^+\eta)$ as reference, the absolute branching fraction is calculated to be $\mathcal{B}(\Lambda_c^+\to n\pi^+\eta)=(2.94\pm0.59_{\rm stat.}\pm0.23_{\rm syst.}\pm0.13_{\rm ref.})\times10^{-3}$. The intermediate process $\Lambda_c^+\to na_0(980)^+$ is also searched for in the $\pi^+\eta$ invariant mass spectrum. Since no significant signal is found, the upper limit on $\mathcal{B}(\Lambda_c^+\to na_0(980)^+)\times\mathcal{B}(a_0(980)^+\to\pi^+\eta)$ is set to $8.4\times10^{-4}$ at 90\% confidence level. A sophisticated deep learning approach using a Transformer-based architecture is employed to distinguish signals from prevalent hadronic backgrounds, complemented by thorough validation and systematic uncertainty quantification.

hep-ex↗

arXiv2026

Real-Time Wiener Deconvolution for feature reconstruction in JUNO

In particle physics, experiments generate substantial amounts of data that can be difficult to process without preliminary scaling. To avoid losing potentially crucial data, experimental collaborations are studying novel techniques for real-time data processing to extract features for further physics analysis. A common approach, especially in neutrino physics, is to use FPGAs for data acquisition and pre-processing. This paper presents an advanced Real-Time Wiener deconvolution algorithm designed to leverage the processing capabilities of the FPGA integrated into the readout boards of the Jiangmen Underground Neutrino Observatory (JUNO). The goal is to enable real-time reconstruction of the signal generated by photomultiplier tubes (PMTs) when neutrino interactions are detected. By exploiting online reconstruction of the signal generated by PMTs, we expect to improve the detection of low-energy depositions, such as those produced by transient astrophysical phenomena. These depositions are usually not saved because of the significant background that affects the low end of the energy spectrum, which would result in a large trigger rate, hence a large amount of data required for storage. This paper presents the features of the algorithm, including its ability to manage high-throughput data streams with minimal latency, adaptability, and resilience in discerning the characteristics of input data. Performance is evaluated on a JUNO electronic board. This study further demonstrates the potential of FPGA-based solutions for neutrino physics.

physics.ins-det↗

arXiv2026

Search for the radiative decays $D^0\to \gamma \bar K_1(1270)^0$ and $D^+\to \gamma K_1(1270)^+$

A search for the radiative decays $D^0\to \gamma \bar K_1(1270)^0$ and $D^+\to \gamma K_1(1270)^+$ is conducted using $20.3~\mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data collected at the center-of-mass energy $\sqrt{s}=3.773$ GeV by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and upper limits on the branching fractions of $D^0\to \gamma \bar K_1(1270)^0$ and $D^+\to \gamma K_1(1270)^+$ at 90\% confidence level are determined to be $7.7\times10^{-4}$ and $3.9\times10^{-5}$, respectively. This represents the first test of the Vector Meson Dominance mechanism in the radiative decays of charmed mesons to axial-vector mesons.

hep-ex↗

arXiv2026

Observation of $D_s^+ \to a_0(980)^+f_0(500)$ in the Amplitude Analysis of $D_s^+ \to \pi^+ \pi^0 \pi^0 \eta$

We report the first observation of the decay $D_s^+ \to \pi^+\pi^0\pi^0\eta$ in a data set corresponding to an integrated luminosity of 7.33 fb$^{-1}$, collected in $e^+e^-$ collisions by the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV. An unexpectedly large branching fraction $\mathcal{B}( D_s^+ \to a_0(980)^+ f_0(500), a_0(980)^+ \to \pi^+\eta, f_0(500)\to \pi^0\pi^0) = (0.98 \pm 0.16_{\rm{stat.}} \pm 0.22_{\rm{syst.}})\%$ is measured with a significance exceeding $10\sigma$, offering new constraints on the internal structure of light scalar mesons. The dominant intermediate process is $D_s^+ \to a_1(1260)^+\eta, a_1(1260)^+\to \rho(770)^+\pi^0$ with a branching fraction of $(1.77 \pm 0.21_{\rm stat.} \pm 0.12_{\rm syst.})\%$. The isospin symmetry has been validated to the decays of $a_1(1260)^+\to \rho(770)^0\pi^+$ and $a_1(1260)^+\to \rho(770)^+\pi^0$. Moreover, the measured $\mathcal{B}(D_s^+\to \pi^+\pi^0\pi^0\eta|_{\rm{non}-\eta^\prime})=(2.97 \pm 0.23_{\rm stat.} \pm 0.14_{\rm sys.})$ reduces the undetected $D_s^+ \to \eta X$ decay branching fractions to (0.1 $\pm$ 3.1)\%.

hep-ex↗