arXiv subjects

R. Farinelli

Publications and source records attributed to R. Farinelli.

At least 127 records · Page 7Linked to original sources

arXiv2025

Measurement of Born Cross Sections and Effective Form Factors of $e^+e^-\to Ω^{-}\barΩ^{+}$ from$\sqrt{s}$ = 3.7 to 4.7 GeV

Using $e^+e^-$ collision data corresponding to an integrated luminosity of 22.7 fb$^{-1}$, collected at center-of-mass energies between 3.7 and 4.7 GeV with the BESIII detector at the BEPCII storage ring, we measure the energy-dependent Born cross sections of $e^+e^-\to Ω^{-}\barΩ^+$ and the effective form factors of the $Ω^-$ baryon. The analysis employs a single baryon tagging method, and the results are consistent with theoretical predictions, providing critical constraints on the electromagnetic structure of the $Ω^-$ hyperon. No significant signal of charmonium or charmonium-like states decaying to $Ω^{-}\barΩ^+$ is observed in the investigated energy range.

hep-ex↗

arXiv2025

Observation of Charmonium $h_{c}$ Radiative Decays to Multiple Light Hadrons and the Tensor State $f_2(1270)$

Using $ψ(3686)\rightarrow π^{0} h_{c}$ decays from a data sample of $(27.12\pm0.14)\times10^{8}$ $ψ(3686)$ events collected by the BESIII detector at the BEPCII collider, $h_c$ radiative decays to $γπ^{+}π^{-},~γπ^{+}π^{-}η,~\gamma2(π^{+}π^{-})$, and $γp\bar{p}$ are observed for the first time, each with a significance greater than $5σ$. The corresponding branching fractions are measured. Furthermore, intermediate states below 2.8 GeV/$c^{2}$ are investigated, leading to the first observation of the decay process of $h_c\rightarrowγf_{2}(1270)\rightarrowγπ^{+}π^{-}$ with a significance of $5.5\,σ$. This observation represents the first instance of $h_c$ radiative decay to a tensor state.

hep-ex↗

arXiv2025

Euclid: Quick Data Release (Q1)- The connection between galaxy close encounters and radio activity

Using the large statistics provided by both Euclid and the LOFAR surveys, we present the first large-scale study of the connection between radio emission, its morphology, and the merging properties of the hosts of radio sources up to z=2. By dividing the radio sample into active galactic nuclei (AGN) and star-forming galaxies, we find that radio-emitting AGN show a clear preference to reside within galaxies undergoing a merging event. This is more significant for AGN that present extended and/or complex radio emission: indeed, about half of them are associated with merging systems, while only 15% are hosted by an isolated galaxy. The observed trend is primarily driven by AGN residing at z < 1, especially in the case of high - P144MHz > 10^24 W Hz-1 sr-1 - radio luminosities (60% in mergers versus 10% isolated regardless of radio appearance). The situation is reversed in the case of radio-emitting star-forming galaxies, which are preferentially associated with isolated systems. This is more significant as we move towards low radio-luminosity/star-formation objects (P144MHz < 10^23 W Hz-1 sr-1) for which we find 40% in isolated systems versus 20% in mergers. These values hold regardless of redshift. We interpret the above result for AGN with their need to accrete outer gas from local encounters in order to trigger (radio) activity, especially in the case of extended radio emission such as hot-spots and lobes. This is mostly observed at z < 1, since in the local Universe galaxies are more gas deprived than their higher-redshift counterparts. Internal gas reservoirs instead seem sufficient to trigger star formation within the majority of galaxies, which indeed prefer to be associated with isolated systems at all redshifts probed. (abridged)

astro-ph.GA↗

arXiv2025

Euclid: Quick Data Release (Q1) -- Secondary nuclei in early-type galaxies

Massive early-type galaxies (ETGs) are believed to form primarily through mergers of less massive progenitors, leaving behind numerous traces of violent formation histories, such as stellar streams and shells. A particularly striking signature of these mergers is the formation of supermassive black hole (SMBH) binaries, which can create depleted stellar cores through interactions with stars on radial orbits - a process known as core scouring. The secondary SMBH in such systems may still carry a dense stellar envelope and thereby remain observable for some time as a secondary nucleus, while it is sinking towards the shared gravitational potential of the merged galaxy. We leverage Euclid's Q1 Early Release data to systematically search for secondary nuclei in ETGs. We present a preliminary sample of 666 candidate systems distributed over 504 hosts (some of which contain multiple secondary nuclei). The vast majority of these fall at separations of 3 kpc to 15 kpc, indicative of normal mergers. 44 fall at projected separations of less than 2 kpc. We argue those candidates at very close angular separations are unlikely to be a consequence of chance alignments. We show that their stellar masses are mostly too large for them to be globular clusters and that a significant subset are unresolved even at Euclid's spatial resolution, rendering them too small to be dwarf galaxies. These may represent the highest-density nuclei of a previously merged galaxy, currently sinking into the centre of the new, common gravitational potential and thus likely to host a secondary SMBH. We then demonstrate that convolutional neural networks offer a viable avenue to detect multiple nuclei in the thirty-times larger sky coverage of the future Euclid DR1. Finally, we argue that our method could detect the remnants of a recoil event from two merged SMBHs.

astro-ph.GA↗

arXiv2025

Euclid Quick Data Release (Q1). Spectroscopic unveiling of highly ionised lines at z = 2.48-3.88

This study explores a rare population of sources in a currently uncharted region of spectroscopic redshift space in the Euclid Quick Data Release (Q1), and is intended potentially to support upcoming spectroscopic studies. Our goal is to identify and investigate a population of sources characterised by highly ionised emission lines in their spectra, which are indicative of active galactic nucleus activity, extreme shock phenomena, or Wolf--Rayet stars. A comprehensive visual inspection of spectra is conducted to ensure the reliability of the sample, focusing on the simultaneous detection of both NeV and OII emission-line measurements, a condition that restricts the Euclid spectroscopic redshift range to z=2.48--3.88. To characterise this population, we analysed the morpho-spectrophotometric properties of their host galaxies. This allowed for a direct comparison with control sources that exhibit similar OII properties and spectroscopic redshifts, but not NeV lines. We identify sources solely based on spectroscopic criteria in the redshift range beyond the Halpha regime. Encompassing 65 potential NeV candidates, the resulting sample delivers the first systematic probe of these NeV candidate emitters at high redshift. We found a good agreement, within 1$σ$, between the spectral measurements calculated using both direct integration and Gaussian fitting methodologies. The NeV candidates exhibit colours similar to bright QSOs, with only a few in the tail of very red quasars. We observed a higher stellar mass content, a lower continuum around the 4000A break, and a similar Sérsic index distribution compared to the control sample. This unique sample paves the way for a wide range of scientific investigations, which will be pursued in the forthcoming data releases.

astro-ph.GA↗

arXiv2025

Euclid Quick Data Release (Q1). Extending the quest for little red dots to z<4

Recent James Webb Space Telescope (JWST) observations have revealed a population of sources with a compact morphology and a characteristic `v-shaped' continuum, namely blue at rest-frame $λ<4000$A and red at longer wavelengths. The nature of these sources, called `little red dots' (LRDs), is still debated, as it is unclear if they host active galactic nuclei (AGN) and their number seems to drastically drop at z<4. We take advantage of the $63 °^2$ covered by the quick Euclid Quick Data Release (Q1) to extend the search for LRDs to brighter magnitudes and to lower redshifts than what has been possible with JWST. The selection is performed by fitting the available photometric data (Euclid, the Spitzer Infrared Array Camera (IRAC), and ground-based $griz$ data) with two power laws, to retrieve both the rest-frame optical and UV slopes consistently over a large redshift range (i.e, z<7.6). We exclude extended objects and possible line emitters, and perform a careful visual inspection to remove any imaging artefacts. The final selection includes 3341 LRD candidates at z=0.33-3.6, with 29 detected also in IRAC. The resulting rest-frame UV luminosity function, in contrast with previous JWST studies, shows that the number density of LRD candidates increases from high-z down to z=1.5-2.5 and decreases at lower z. However, less evolution is apparent focusing on the subsample of more robust LRD candidates having IRAC detections, which however has low statistics and limited by the IRAC resolution. The comparison with previous quasar (QSO) UV luminosity functions shows that LRDs are not the dominant AGN population at z<4 and $M_{\rm UV}<-21$. Follow-up studies of these LRD candidates are pivotal to confirm their nature, probe their physical properties and check for their compatibility with JWST sources, given the different spatial resolution and wavelength coverage of Euclid and JWST.

astro-ph.GA↗

arXiv2025

Measurements of the absolute branching fractions of the doubly Cabibbo-suppressed decays $D^+\to K^+π^0$, $D^+\to K^+η$ and $D^+\to K^+η^{\prime}$

Using $20.3\,\rm fb^{-1}$ of $e^+e^-$ collision data collected at a center-of-mass energy of 3.773\,GeV with the BESIII detector, we present the measurements of the absolute branching fractions of the doubly Cabibbo-suppressed decays $D^+\to K^+π^0$, $D^+\to K^+η$ and $ D^+ \to K^+ η^{\prime}$ with the double-tag method, with significantly improved precision compared to the previous measurements. The statistical significance of each signal decay exceeds $10σ$. The branching fractions are determined to be ${\mathcal B}(D^+\to K^+ π^0) = (1.45 \pm 0.06 \pm 0.08)\times 10^{-4}$, ${\mathcal B}(D^+\to K^+ η) = (1.17 \pm 0.10 \pm 0.03)\times 10^{-4}$ and ${\mathcal B}(D^+\to K^+ η^{\prime}) = (1.88 \pm 0.15 \pm 0.11)\times 10^{-4}$, where the first uncertainties are statistical and the second systematic. The branching fractions of $D^+\to K^+η$ and $ D^+ \to K^+ η^{\prime}$ are consistent with the world average values. The reported branching fraction of $D^+\to K^+π^0$ deviates with the world average value by 3$σ$.

hep-ex↗

arXiv2025

First observation of $Λ_{c}(2595)^{+} \to Λ^{+}_{c}π^0π^0$ and $Λ_{c}(2625)^{+}\to Λ^{+}_{c}π^0π^0$

By analysing $e^+e^-$ annihilation data corresponding to an integrated luminosity of 368.48~pb$^{-1}$ collected at the centre-of-mass energies of $\sqrt{s} = 4.918$ and $4.951$~GeV with the BESIII detector, we report the first observation of $Λ_{c}(2595)^{+}$ and $Λ_{c}(2625)^{+}\to Λ^{+}_{c}π^0π^0$ with statistical significances of 7.9$σ$ and 11.8$σ$, respectively. The branching fractions of $Λ_{c}(2595)^{+}$ and $Λ_{c}(2625)^{+}\to Λ^{+}_{c}π^0π^0$ are measured to be $(59.5 \pm 11.1_{\rm stat.} \pm 7.9_{\rm syst.}) \%$ and $(41.0 \pm 5.2_{\rm stat.} \pm 3.3_{\rm syst.}) \%$, respectively. The absolute branching fraction of $Λ_{c}(2595)^{+}$ is consistent with the expectation of the mechanism referred to as the threshold effect, proposed for the strong decays of $Λ_{c}(2595)^{+}$ within uncertainty.

hep-ex↗

arXiv2025

Search for the charmonium weak decays $J/ψ\to D_{s}^{-}ρ^{+}+c.c.$ and $J/ψ\to D_{s}^{-}π^{+}+c.c.$

Based on $(10087\pm44)\times 10^6$ $J/ψ$ events recorded with the BESIII detector, we search for the rare charmonium weak decays $J/ψ\to D_{s}^{-}ρ^{+}+c.c.$ and $J/ψ\to D_{s}^{-}π^{+}+c.c.$ No signal is observed, and upper limits on the branching fractions at the $90\%$ confidence level are set as $\mathcal{B}(J/ψ\to D_{s}^{-}ρ^{+}+c.c.)<8.0\times10^{-7}$ and $\mathcal{B}(J/ψ\to D_{s}^{-}π^{+}+c.c.)<4.1\times10^{-7}$. Our results provide the most stringent experimental constraints on these decays.

hep-ex↗

arXiv2025

Euclid Quick Data Release (Q1). A probabilistic classification of quenched galaxies

Investigating what drives the quenching of star formation in galaxies is key to understanding their evolution. The Euclid mission will provide rich data from optical to infrared wavelengths for millions of galaxies, and enable precise measurements of their star formation histories. Using the first Euclid Quick Data Release (Q1), we developed a probabilistic classification framework that combines the average specific star-formation rate inferred over two timescales ($10^8,10^9$ yr) to categorise galaxies as `ageing' (secularly evolving), `quenched' (recently halted star formation), or `retired' (dominated by old stars). Two classification methods were employed: a probabilistic approach, which integrates posterior distributions, and a model-driven method, which optimises sample purity and completeness using IllustrisTNG. At $z<0.1$ and $M_\ast \gtrsim 3\times10^{8}\,M_\odot$, we obtain Euclid class fractions of 68-72\%, 8-17\%, and 14-19\% for ageing, quenched, and retired populations, respectively. Ageing and retired galaxies dominate at the low- and high-mass end, respectively, while quenched galaxies surpass the retired fraction for $M_\ast \lesssim 10^{10}\,\rm M_\odot$. The evolution with redshift shows increasing and decreasing fractions of ageing and retired galaxies, respectively. More massive galaxies usually undergo quenching episodes at earlier times than to their low-mass counterparts. In terms of the mass-size-metallicity relation, ageing galaxies generally exhibit disc morphologies and low metallicities. Retired galaxies show compact structures and enhanced chemical enrichment, while quenched galaxies form an intermediate population that is more compact and chemically evolved than ageing systems. This work demonstrates Euclid's great potential for elucidating the physical nature of the quenching mechanisms that govern galaxy evolution.

astro-ph.GA↗

arXiv2025

Measurements of absolute branching fractions of $D^{0(+)}\to KKKπ$ decays

Using an $e^+e^-$ sample of $20.3\,\rm fb^{-1}$ collected at the center-of-mass energy $\sqrt{s}=$ 3.773 GeV with the BESIII detector, we report measurements of several four-body hadronic decays of the $D$ mesons. The absolute branching fractions are determined to be ${\mathcal B}(D^0\to K^0_S K^+K^-π^0 )=( 18.4^{+2.6}_{-2.5}\pm 2.4)\times 10^{-5}$, ${\mathcal B}(D^0\to K^0_S K^0_S K^-π^+ )=( 12.9^{+1.7}_{-1.6}\pm 2.5)\times 10^{-5}$, ${\mathcal B}(D^0\to K^0_S K^0_S K^+π^-)=(5.7^{+1.2}_{-1.1}\pm 1.3)\times 10^{-5}$, ${\mathcal B}(D^0\to K^+K^-K^-π^+ )=(17.4^{+1.8}_{-1.7}\pm { 2.2})\times 10^{-5}$, and ${\mathcal B}(D^+\to K^0_S K^+K^-π^+)=(13.8^{+2.4}_{-2.2}\pm 2.5)\times 10^{-5}$. Furthermore, significant $ϕ$ signals are found in the decay channels involving $K^+K^-$ pair, and the corresponding branching fractions are measured as ${\mathcal B}(D^0\to ϕK^0_Sπ^0 )=( 22.7^{+5.4}_{-5.1}\pm 3.7)\times 10^{-5}$, ${\mathcal B}(D^0\to ϕK^-π^+ )=(25.2^{+3.5}_{-3.3}\pm 4.6)\times 10^{-5}$, ${\mathcal B}(D^+\to ϕK^0_Sπ^+)=(16.5 ^{+6.0}_{-5.3}\pm 2.6 )\times 10^{-5}$. The branching fractions of $D^0\to K^0_S K^+K^-π^0$, $D^0\to ϕK^0_Sπ^0$, and $D^+\to ϕK^0_S π^+$ are measured for the first time, and those of $D^0\to K^0_S K^0_SK^-π^+$, $D^0\to K^0_S K^0_SK^+π^-$, $D^0\to K^+K^-K^-π^+$, $D^0\to ϕK^-π^+$, and $D^+\to K^0_S K^+K^-π^+$ are measured with improved precision. The first uncertainties are statistical and the second are systematic.

hep-ex↗

arXiv2025

Search for the charged lepton flavor violating decay $ψ(3686)\to e^{\pm}μ^{\mp}$

By analyzing $(2367.0\pm11.1)\times10^6$ $ψ(3686)$ events collected in $e^+e^-$ collisions at $\sqrt{s}=3.686~\rm GeV$ with the BESIII detector at the BEPCII collider, we report the first search for the charged lepton flavor violating decay $ψ(3686)\to e^{\pm}μ^{\mp}$. No signal is found. An upper limit on the branching fraction $\mathcal{B}(ψ(3686)\to e^{\pm}μ^{\mp})$ is determined to be $1.4\times10^{-8}$ at the 90\% confidence level.

hep-ex↗

arXiv2025

Observation of $D^+\to K^0_Sπ^0μ^+ν_μ$, Test of Lepton Flavor Universality and First Angular Analysis of $D^+\to \bar{K}^\ast(892)^0\ell^+ν_\ell$

We report a study of the semileptonic decays $D^+\to K_S^0π^0\ell^+ν_\ell$ ($\ell = e, μ$) based on $20.3\,\mathrm{fb}^{-1}$ of $e^+e^-$ collision data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The $D^+\to K_S^0π^0μ^+ν_μ$ decay is observed for the first time, with a branching fraction of $(0.896\pm0.017_{\rm stat}\pm0.008_{\rm syst})\%$, and the branching fraction of $D^+\to K_S^0π^0e^+ν_e$ is determined with the improved precision as $(0.943\pm0.012_{\rm stat}\pm0.010_{\rm syst})\%$. From the analysis of the dynamics, we observe that the dominant $\bar{K}^\ast(892)^0$ component is accompanied by an $S$-wave contribution, which accounts for $(7.10 \pm 0.68_{\rm stat} \pm 0.41_{\rm syst})\%$ of the total decay rate of the $μ^+$ channel and $(6.39 \pm 0.17_{\rm stat} \pm 0.14_{\rm syst})\%$ of the $e^+$ channel. Assuming a single-pole dominance parameterization, the hadronic form factor ratios are extracted to be $r_V=V(0)/A_1(0)=1.42 \pm\, 0.03_{\rm stat} \pm\, 0.02_{\rm syst}$ and $r_2=A_2(0)/A_1(0)=0.75 \pm\, 0.03_{\rm stat} \pm\, 0.01_{\rm syst}$. Based on the first comprehensive angular and the decay-rate $CP$ asymmetry analysis, the full set of averaged angular and $CP$ asymmetry observables are measured as a function of the momentum-transfer squared; they are consistent with expectations from the Standard Model. No evidence for violation of $μ-e$ lepton-flavor universality is observed in either the full range or the five chosen bins of momentum-transfer squared.

hep-ex↗

arXiv2025

Study of $ϕ\to K\bar{K}$ and $K_{S}^{0}-K_{L}^{0}$ Asymmetry in the Amplitude Analysis of $D_{s}^{+} \to K_{S}^{0}K_{L}^{0}π^{+}$ Decays

Using $e^+e^-$ annihilation data corresponding to a total integrated luminosity of 7.33 $\rm fb^{-1}$ collected at center-of-mass energies between 4.128 and 4.226~GeV with the BESIII detector, we provide the first amplitude analysis and absolute branching fraction measurement of the hadronic decay $D_{s}^{+} \to K_{S}^{0}K_{L}^{0}π^{+}$. The branching fraction of $D_{s}^{+} \to K_{S}^{0}K_{L}^{0}π^{+}$ is determined to be $(1.86\pm0.06_{\rm stat}\pm0.03_{\rm syst})\%$. Combining the $\mathcal{B}[D_{s}^{+} \to ϕ(\to K_{S}^0K_{L}^0) π^+]$ obtained in this work and the world average of $\mathcal{B}[D_{s}^{+} \to ϕ(\to K^+K^-) π^+]$, we measure the relative branching fraction $\mathcal{B}(ϕ\to K_S^0K_L^0)/\mathcal{B}(ϕ\to K^+K^-)$=($0.593 \pm 0.023_{\rm stat} \pm 0.014_{\rm syst} \pm 0.016_{ϕπ}$), where the third error is due to the uncertainty of the $\mathcal{B}(D_s^+ \to ϕπ^+,ϕ\to K^+K^-)$. Our result deviates from the Particle Data Group value by more than 3$σ$. Furthermore, the asymmetry of the branching fractions of $D^+_s\to K_{S}^0K^{*}(892)^{+}$ and $D^+_s\to K_{L}^0K^{*}(892)^{+}$, $\frac{\mathcal{B}[D_{s}^{+} \to K_{S}^0K^{*}(892)^{+}]-\mathcal{B}[D_{s}^{+} \to K_{L}^0K^{*}(892)^{+}]}{\mathcal{B}[D_{s}^{+} \to K_{S}^0K^{*}(892)^{+}]+\mathcal{B}[D_{s}^{+} \to K_{L}^0K^{*}(892)^{+}]}$, is determined to be $(-14.5\pm 5.1_{\rm stat}\pm 1.8_{\rm syst})\%$.

hep-ex↗

arXiv2025

Single Inclusive $π^\pm$ and $K^\pm$ Production in $e^+e^-$ Annihilation at center-of-mass Energies from 2.000 to 3.671GeV

Using data samples with a total integrated luminosity of 253 $\rm pb^{-1}$ collected by the BESIII detector operating at the BEPCII collider, the differential cross-sections of inclusive $π^\pm$ and $K^\pm$ production, as a function of momentum and normalized by the total hadronic cross-section, are measured at center-of-mass energies from 2.000 to 3.671 GeV. The measured $π^{\pm}$ cross sections are consistent with the previously reported $π^{0}$ cross-sections by BESIII, while the $K^{\pm}$ cross sections are systematically higher than the $K^0_S$ cross sections by a factor of approximately 1.4. These new results are in agreement with state-of-the-art QCD analyses at next-to-next-to-leading order accuracy, particularly in the large hadron momentum region at energy scales down to 3 GeV. These findings support the validity of isospin symmetry in parton fragmentation processes.

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arXiv2025

Euclid: Exploring observational systematics in cluster cosmology -- a comprehensive analysis of cluster counts and clustering

This study explores the impact of observational and modelling systematic effects on cluster number counts and cluster clustering and provides model prescriptions for their joint analysis, in the context of the \Euclid survey. Using 1000 \Euclid-like cluster catalogues, we investigate the effect of systematic uncertainties on cluster summary statistics and their auto- and cross-covariance, and perform a likelihood analysis to evaluate their impact on cosmological constraints, with a focus on the matter density parameter $Ω_{\rm m}$ and on the power spectrum amplitude $σ_8$. Combining cluster clustering with number counts significantly improves cosmological constraints, with the figure of merit increasing by over 300\% compared to number counts alone. We confirm that the two probes are uncorrelated, and the cosmological constraints derived from their combination are almost insensitive to the cosmology dependence of the covariance. We find that photometric redshift uncertainties broaden cosmological posteriors by 20--30\%, while secondary effects like redshift-space distortions (RSDs) have a smaller impact on the posteriors -- 5\% for clustering alone, 10\% when combining probes -- but can significantly bias the constraints if neglected. We show that clustering data below $60\,h^{-1}\,$Mpc provides additional constraining power, while scales larger than acoustic oscillation scale add almost no information on $Ω_{\rm m}$ and $σ_8$ parameters. RSDs and photo-$z$ uncertainties also influence the number count covariance, with a significant impact, of about 15--20\%, on the parameter constraints.

astro-ph.CO↗

arXiv2025

Cosmology Likelihood for Observables in \Euclid (CLOE). 1. Theoretical recipe

As the statistical precision of cosmological measurements increases, the accuracy of the theoretical description of these measurements needs to increase correspondingly in order to infer the underlying cosmology that governs the Universe. To this end, we have created the Cosmology Likelihood for Observables in Euclid (CLOE), which is a novel cosmological parameter inference pipeline developed within the Euclid Consortium to translate measurements and covariances into cosmological parameter constraints. In this first in a series of six papers, we describe the theoretical recipe of this code for the Euclid primary probes. These probes are composed of the photometric 3x2pt observables of cosmic shear, galaxy-galaxy lensing, and galaxy clustering, along with spectroscopic galaxy clustering. We provide this description in both Fourier and configuration space for standard and extended summary statistics, including the wide range of systematic uncertainties that affect them. This includes systematic uncertainties such as intrinsic galaxy alignments, baryonic feedback, photometric and spectroscopic redshift uncertainties, shear calibration uncertainties, sample impurities, photometric and spectroscopic galaxy biases, as well as magnification bias. The theoretical descriptions are further able to accommodate both Gaussian and non-Gaussian likelihoods and extended cosmologies with non-zero curvature, massive neutrinos, evolving dark energy, and simple forms of modified gravity. These theoretical descriptions that underpin CLOE will form a crucial component in revealing the true nature of the Universe with next-generation cosmological surveys such as Euclid.

astro-ph.CO↗

arXiv2025

Improved Measurements of $D^+ \to ηe^+ν_e$ and $D^+ \to ημ^+ν_μ$

Using 20.3 fb$^{-1}$ of $e^+e^-$ collision data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we measure the branching fractions of $D^+\to ηe^+ν_e$ and $D^+\to ημ^+ν_μ$ to be $(9.75\pm0.29\pm0.28)\times10^{-4}$ and $(9.08\pm0.35\pm0.23)\times10^{-4}$, where the first and second uncertainties are statistical and systematic, respectively. From a simultaneous fit to their partial decay rates, we determine the product of the hadronic form factor $f^η_+(0)$ and the modulus of the $c\to d$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ to be $f^η_+(0)|V_{cd}|=0.078\pm0.002\pm0.001$. Taking the $|V_{cd}|$ value from the Standard Model global fit as input, we obtain $f^η_+(0)=0.345\pm0.008\pm0.003$. The ratio between the measured branching fractions of $D^+\toη^+μ^+ν_μ$ and $D^+\toηe^+ν_e$, is determined to be $0.93\pm0.05_{\rm stat.}\pm0.02_{\rm syst.}$, indicating no violation of lepton flavor universality.

hep-ex↗