arXiv subjects

C. Guaraldo

Publications and source records attributed to C. Guaraldo.

At least 19 recordsLinked to original sources

arXiv2026

High-precision measurement of the kaonic hydrogen 1s level shift and width with SIDDHARTA-2

Kaonic atoms provide a unique experimental probe of strong interaction in the low-energy regime. In particular, the strong-interaction-induced shift ($\varepsilon_{1\text{s}}$) and width ($\Gamma_{1\text{s}}$) of kaonic hydrogen directly constrain the low-energy antikaon-nucleon ($\bar{K}N$) interaction at threshold and the theoretical description of the $\Lambda$(1405) resonance. We report a new high-precision measurement of kaonic hydrogen X-ray transitions performed by the SIDDHARTA-2 experiment at the DA$\Phi$NE collider (INFN-LNF), based on an integrated luminosity of 237 pb$^{-1}$. The extracted values, $\varepsilon_{1\text{s}}\,=\,-303.0\,\pm\,17.0\,(stat.)\,\pm\,2.5\,(syst.)$ eV and $\Gamma_{1\text{s}}\,=\,607\,\pm\,62\,(stat.)\,\pm\,6\,(syst.)$ eV, represent the most precise determination to date, improving the precision by approximately a factor-of-two with respect to the previous SIDDHARTA measurement. These results significantly tighten the experimental constraints on theoretical description of the low-energy $\bar{K}N$ interaction.

nucl-ex↗

arXiv2026

Bound-state QED test above the Schwinger limit with kaonic fluorine

Kaonic atoms, formed when a negatively charged kaon replaces an electron in an atomic orbit, provide access to bound-state quantum electrodynamics (BSQED) in electromagnetic fields far stronger than in ordinary atoms. Here, we report an experimental test of BSQED in a regime where the mean Coulomb field exceeds the Schwinger limit. Using high-precision x-ray spectroscopy of kaonic fluorine with the SIDDHARTA-2 experiment at DA$\Phi$NE, corresponding to an integrated luminosity of 22.4 pb$^{-1}$, we observe transitions involving the 4f and 3d levels, probing field-to-Schwinger-limit ratios of 1.11 and 3.70, respectively. The measured transition energies agree with state-of-the-art Dirac-Fock calculations. In particular, the 5g-4f transition showing a residual of 5.8 $\pm$ 4.7 (stat.) $\pm$ 5.5 (syst.) eV and a $\sim$ 9$\sigma$ sensitivity to QED contributions. These results provide a direct test of BSQED in the strong-field regime of QED above the Schwinger limit, opening a new avenue for precision studies in extreme electromagnetic fields.

physics.atom-ph↗

arXiv2025

New 1mm thick Silicon Drift Detectors for future researches of Kaonic Atoms and the Pauli Exclusion principle

Kaonic atoms, formed when a negatively charged kaon replaces an electron, provide a sensitive probe of the low-energy strong interaction via precision X-ray spectroscopy. The SIDDHARTA-2 experiment at the DA$\Phi$NE collider employs high-performance Silicon Drift Detectors (SDDs) optimized for the 4-12 keV range to study light kaonic systems. In preparation for the EXKALIBUR phase, which targets heavier kaonic atoms, new 1 mm-thick SDDs have been developed with Politecnico di Milano and Fondazione Bruno Kessler. Their increased thickness enhances the quantum efficiency by a factor of about two at 30 keV while preserving excellent energy resolution. These detectors are also intended for VIP-3, the next-generation test of the Pauli Exclusion Principle (PEP). Building on VIP-2, which set the most stringent limits on PEP-violating $K_{\alpha}$ transitions in copper, VIP-3 will extend the search to heavier elements such as Ag, Sn, and Zr. Preliminary measurements demonstrate efficient detection up to 30 keV, supporting future high-precision studies of the kaon-nucleon interaction and PEP in heavier systems.

physics.ins-det↗

arXiv2025

Precision Test of Bound-State QED at Intermediate-Z with Kaonic Neon

We report Dirac-Fock calculations of transition energies for kaonic neon (KNe). For the most intense line, the 7-6 transition, the calculated energy is 9450.28 eV, which includes a bound-state QED (BSQED) contribution of 12.66 eV. This is in excellent agreement with the recent SIDDHARTHA-2 measurement at DA$\Phi$NE of 9450.23 $\pm$ 0.37 (stat.) $\pm$ 1.50 (syst.) eV. With the QED shift far exceeding experimental uncertainty, these results establish kaonic atoms as powerful platforms for precision tests of BSQED in intermediate-Z systems.

physics.atom-ph↗

arXiv2024

The \pi^+\pi^- Coulomb interaction study and its use in the data processing

In this work the Coulomb effects (Coulomb correlations) in $\pi^+\pi^-$ pairs produced in p + Ni collisions at 24 GeV/$c$, are studied using experimental $\pi^+\pi^-$ pair distributions in $Q$, the relative momentum in the pair center of mass system (c.m.s), and its projections $Q_L$ (longitudinal component) and $Q_t$ (transverse component) relative to the pair direction in the laboratory system (l.s.). The $Q$, $Q_L$, and $Q_t$ distributions of the {\sl Coulomb pairs} in the c.m.s. have been simulated assuming they are described by the phase space modified by the known point-like Coulomb correlation function $A_C(Q)$, corrected for small effects due to the nonpoint-like pair production and the strong two-pion interaction. The same distributions of {\sl non-Coulomb pairs} have been simulated according to the phase space, but without $A_C(Q)$. It is shown that the number of {\sl Coulomb pairs} in all $Q_t$ intervals, including the small $Q_t$ (small opening angles $\theta$ in the l.s.) is calculated with the theoretical precision better than 2\%. The comparison of the simulated and experimental numbers of {\sl Coulomb pairs} at small $Q_t$ allows us to check and correct the detection efficiency for the pairs with small $\theta$ (0.06 mrad and smaller). It is shown that {\sl Coulomb pairs} can be used as a new physical tool to check and correct the quality of the simulated events. The special property of the {\sl Coulomb pairs} is the possibility of checking and correcting the detection efficiency, especially for the pairs with small opening angles.

hep-ph↗

arXiv2024

Measurement of the mesonic decay branch of the $\bar{K}\!N\!N$ quasi-bound state

We conducted measurements of $K^- + {^3{\rm He}} \to π\!Y \!N + N'$ reactions using a $1~{\rm GeV}/c$ $K^-$-beam, with the objective of understanding the broad decay width of $\bar{K} \!N \!N$ (approximately twice as broad as that of $Λ(1405)$ considered to be the $\bar{K} \!N$ quasi-bound state). We successfully reproduced distributions of the $π\! Y \! N$ invariant mass and momentum transfer for $π\! Y \! N$ using model fitting functions for $\bar{K} \!N \!N$ formation and quasi-free $\bar{K}$ absorption (${\rm QF}_{\bar{K}-{\rm abs}}$) processes. The model can describe the experimental data quite well, and four $\bar{K} \! N \! N \to π\! Y \! N $ cross-sections were obtained. The results indicate that mesonic decay is the dominant decay branch of $\bar{K} \! N \! N$. The results also suggest that $Γ_{πΛN} \sim Γ_{πΣN}$, which indicates that the $I_{\bar{K} \! N}=1$ absorption channel, in addition to the $I_{\bar{K} \! N}=0$ absorption channel, substantially contribute to the $\bar{K} \! N \! N$ decay, making the $\bar{K} \! N \! N$ state approximately twice as unstable as $Λ$(1405).

nucl-ex↗

arXiv2024

Kaonic lead feasibility measurement at DAΦNE to solve the charged kaon mass discrepancy

An HPGe detector equipped with a transistor reset preamplifier and readout with a CAEN DT5781 fast pulse digitizer was employed in the measurement of X-rays from kaonic lead at the DA$Φ$NE $e^+e^-$ collider at the Laboratori Nazionali di Frascati of INFN. A thin scintillator in front of a lead target was used to select kaons impinging on it and to form the trigger for the HPGe detector. We present the results of the kaonic lead feasibility measurement, where we show that the resolution of the HPGe detector in regular beam conditions remains the same as that without the beam and that a satisfactory background reduction can be achieved. This measurement serves as a test bed for future dedicated kaonic X-rays measurements for the more precise determination of the charged kaon mass.

physics.ins-det↗

arXiv2023

SIDDHARTA-2 apparatus for kaonic atoms research on the DA$Φ$NE collider

SIDDHARTA-2 represents a state-of-the-art experiment designed to perform dedicated measurements of kaonic atoms, which are particular exotic atom configurations composed of a negatively charged kaon and a nucleus. Investigating these atoms provides an exceptional tool to comprehend the strong interactions in the non-perturbative regime involving strangeness. The experiment is installed at the DA$Φ$NE electron-positron collider, of the INFN National Laboratory of Frascati (INFN-LNF) in Italy, aiming to perform the first-ever measurement of the 2p$\rightarrow$1s X-ray transitions in kaonic deuterium, a crucial step towards determining the isospin-dependent antikaon-nucleon scattering lengths. Based on the experience gained with the previous SIDDHARTA experiment, which performed the most precise measurement of the kaonic hydrogen 2p$\rightarrow$1s X-ray transitions, the present apparatus has been upgraded with innovative Silicon Drift Detectors (SDDs), distributed around a cryogenic gaseous target placed in a vacuum chamber at a short distance above the interaction region of the collider. We present a comprehensive description of the SIDDHARTA-2 setup including the optimization of its various components during the commissioning phase of the collider.

physics.ins-det↗

arXiv2023

CdZnTe detectors tested at the DAΦNE collider for future kaonic atoms measurements

The SIDDHARTA-2 collaboration at the INFN Laboratories of Frascati (LNF) aims to perform groundbreaking measurements on kaonic atoms. In parallel and beyond the ongoing kaonic deuterium, presently running on the DA$Φ$NE collider at LNF, we plan to install additional detectors to perform further kaonic atoms' studies, taking advantage of the unique low energy and low momentum spread $K^-$ beam delivered by the at-rest decay of the $ϕ$ meson. CdZnTe devices are ideal for detecting transitions toward both the upper and lower levels of intermediate-mass kaonic atoms, like kaonic carbon and aluminium, which have an important impact on the strangeness sector of nuclear physics. We present the results obtained in a set of preliminary tests conducted on DA$Φ$NE, in view of measurements foreseen in 2024, with the twofold aim to tune the timing window required to reject the extremely high electromagnetic background, and to quantify the readout electronics saturation effect due to the high rate, when placed close to the Interaction Region (IR). In the first test we used commercial devices and electronics, while for the second one both were customized at the IMEM-CNR of Parma and the University of Palermo. The results confirmed the possibility of finding and matching a proper timing window where to identify the signal events and proved better performances, in terms of energy resolution, of the custom system. In both cases, strong saturation effects were confirmed, accounting for a loss of almost 90\% of the events, which will be overcome by a dedicated shielding structure foreseen for the final experimental setup.

physics.ins-det↗

arXiv2023

Precise lifetime measurement of $^4_Λ$H hypernucleus using in-flight $^4$He$(K^-, π^0)^4_Λ$H reaction

We present a new measurement of the $^4_Λ$H hypernuclear lifetime using in-flight $K^-$ + $^4$He $\rightarrow$ $^4_Λ$H + $π^0$ reaction at the J-PARC hadron facility. We demonstrate, for the first time, the effective selection of the hypernuclear bound state using only the $γ$-ray energy decayed from $π^0$. This opens the possibility for a systematic study of isospin partner hypernuclei through comparison with data from ($K^-$, $π^-$) reaction. As the first application of this method, our result for the $^4_Λ$H lifetime, $τ(^4_Λ\mathrm{H}) = 206 \pm 8 (\mathrm{stat.}) \pm 12 (\mathrm{syst.})\ \mathrm{ps}$, is one of the most precise measurements to date. We are also preparing to measure the lifetime of the hypertriton ($^3_Λ$H) using the same setup in the near future.

nucl-ex↗

arXiv2023

Measurements of high-n transitions in intermediate mass kaonic atoms by SIDDHARTA-2 at DA$\mathrmΦ$NE

The SIDDHARTA-2 experiment installed at the DA$\mathrmΦ$NE collider of INFN-LNF performed, for the first time, measurements of high-n transitions in intermediate mass kaonic atoms during the data taking campaigns of 2021 and 2022. Kaonic carbon, oxygen, nitrogen and aluminium transitions, which occur in the setup materials, were measured by using the kaons stopped in the gaseous helium target cell with aluminium frames and Kapton walls, and are reported in this paper. These new kaonic atoms measurements add valuable input to the kaonic atoms transitions data base, which is used as a reference for theories and models of the low-energy strong interaction between antikaon and nuclei. Moreover, these results pave the way for future dedicated kaonic atoms measurements through the whole periodic table and to a new era for the antikaon-nuclei studies at low energy.

nucl-ex↗

arXiv2023

New opportunities for kaonic atoms measurements from CdZnTe detectors

We present the tests performed by the SIDDHARTA-2 collaboration at the DAΦNE collider with a quasi-hemispherical CdZnTe detector. The very good room-temperature energy resolution and efficiency in a wide energy range show that this detector technology is ideal for studying radiative transitions in intermediate and heavy-mass kaonic atoms. The CdZnTe detector was installed for the first time in an accelerator environment to perform tests on the background rejection capabilities, which were achieved by exploiting the SIDDHARTA-2 Luminosity Monitor. A spectrum with an $^{241}Am$ source has been acquired, with beams circulating in the main rings, and peak resolutions of 6% at 60 keV and of 2.2% at 511 keV have been achieved. The background suppression factor, which turned out to be of the order of $\simeq10^{5-6}$, opens the possibility to plan for future kaonic atom measurements with CdZnTe detectors.

physics.ins-det↗

arXiv2022

Pole position of $Λ(1405)$ measured in $d(K^-,n)πΣ$ reactions

We measured a set of $π^\pmΣ^\mp$, $π^0Σ^0$, and $π^-Σ^0$ invariant mass spectra below and above the $\bar{K}N$ mass threshold in $K^-$-induced reactions on deuteron. We deduced the $S$-wave $\bar{K}N\rightarrowπΣ$ and $\bar{K}N\rightarrow\bar{K}N$ scattering amplitudes in the isospin 0 channel in the framework of a $\bar{K}N$ and $πΣ$ coupled channel. We find that a resonance pole corresponding to $Λ(1405)$ is located at 1417.7$^{+6.0}_{-7.4}$(fitting errors)$^{+1.1}_{-1.0}$(systematic errors) + $[-26.1^{+6.0}_{-7.9}$(fitting errors)$^{+1.7}_{-2.0}$(systematic errors)]$i$ MeV/$c^2$, closer to the $\bar{K}N$ mass threshold than the value determined by the Particle Data Group.

nucl-ex↗

arXiv2022

Studies of the linearity and stability of Silicon Drift Detectors for kaonic atoms X-ray spectroscopy

The SIDDHARTA-2 experiment at the DA$Φ$NE collider aims to perform precision measurements of kaonic atoms X-ray spectroscopy for the investigation of the antikaon-nucleon strong interaction. To achieve this goal, novel large-area Silicon Drift Detectors (SDDs) have been developed. These devices have special geometry, field configuration and readout electronics that ensure excellent performance in terms of linearity and stability. The paper presents preliminary results for the linearity determination and stability monitoring of the SDDs system during the measurement of kaonic deuterium carried out in the summer of 2022.

physics.ins-det↗

arXiv2022

First tests of the full SIDDHARTA-2 experimental apparatus with a 4 He gaseous target

In this paper, we present the first tests performed after the full installation of the SIDDHARTA-2 experimental apparatus on the Interaction Region of the DAΦNE collider at the INFN National Laboratories of Frascati. Before starting the first measurement of the kaonic deuterium 2p{\rightarrow}1s transition, accurate evaluation of the background rejection. mainly achieved with the Kaon Trigger system, was required. This run, performed in the period 04-26/05/2022 with a 4 He gaseous target, confirmed the 10^5 rejection factor obtained with a reduced version of the setup and different machine conditions in 2021. This important outcome motivated the filling of the target cell with deuterium and the starting of the measurement campaign of the kaonic deuterium 2p{\rightarrow}1s transition.

physics.ins-det↗

arXiv2022

Investigation of $K^+K^-$ pairs in the effective mass region near $2m_K$

The DIRAC experiment at CERN investigated in the reaction $\rm{p}(24~\rm{GeV}/c) + Ni$ the particle pairs $K^+K^-, π^+ π^-$ and $p \bar{p}$ with relative momentum $Q$ in the pair system less than 100 MeV/c. Because of background influence studies, DIRAC explored three subsamples of $K^+K^-$ pairs, obtained by subtracting -- using time-of-flight (TOF) technique -- background from initial $Q$ distributions with $K^+K^-$ sample fractions more than 70\%, 50\% and 30\%. The corresponding pair distributions in $Q$ and in its longitudinal projection $Q_L$ were analyzed first in a Coulomb model, which takes into account only Coulomb final state interaction (FSI) and assuming point-like pair production. This Coulomb model analysis leads to a $K^+K^-$ yield increase of about four at $Q_L=0.5$ MeV/c compared to 100 MeV/c. In order to study contributions from strong interaction, a second more sophisticated model was applied, considering besides Coulomb FSI also strong FSI via the resonances $f_0(980)$ and $a_0(980)$ and a variable distance $r^*$ between the produced $K$ mesons. This analysis was based on three different parameter sets for the pair production. For the 70\% subsample and with best parameters, $3680\pm 370$ $K^+K^-$ pairs was found to be compared to $3900\pm 410$ $K^+K^-$ extracted by means of the Coulomb model. Knowing the efficiency of the TOF cut for background suppression, the total number of detected $K^+K^-$ pairs was evaluated to be around $40000\pm 10\%$, which agrees with the result from the 30\% subsample. The $K^+K^-$ pair number in the 50\% subsample differs from the two other values by about three standard deviations, confirming -- as discussed in the paper -- that experimental data in this subsample is less reliable.

hep-ex↗

arXiv2021

Recent results and future prospects of kaonic nuclei at J-PARC

$\bar K$-nuclear bound systems, kaonic nuclei, have been widely discussed as products of the strongly attractive $\bar K N$ interaction in $I = 0$ channels. Recently, we demonstrated that kaonic nuclei can be produced via in-flight $(K^-,N)$ reactions using the low-momentum DC kaon beam at the J-PARC E15 experiment. We observed the simplest kaonic nuclei, $K^-pp$, having a much deeper binding energy than normal nuclei. For further studies, we have proposed a series of experimental programs for the systematic investigation of light kaonic nuclei, from $\bar K N$ ($Λ(1405)$) to $\bar K NNNN$. In the new experiment approved as J-PARC E80, we will measure the $\bar K NNN$ ($A=3$) system as a first step toward a comprehensive study.

nucl-ex↗

arXiv2021

Fundamental physics at the strangeness frontier at DAΦNE. Outline of a proposal for future measurements

The DAΦNE collider at INFN-LNF is a unique source of low-energy kaons, which was used by the DEAR, SIDDHARTA and AMADEUS collaborations for unique measurements of kaonic atoms and kaon-nuclei interactions. Presently, the SIDDHARTA-2 collaboration is underway to measure the kaonic deuterium exotic atom. With this document we outline a proposal for fundamental physics at the strangeness frontier for future measurements of kaonic atoms and kaon-nuclei interactions at DAΦNE, which is intended to stimulate discussions within the broad scientific community performing research directly or indirectly related to this field.

nucl-ex↗