arXiv subjects

J. Zmeskal

Publications and source records attributed to J. Zmeskal.

At least 37 records · Page 2Linked to original sources

arXiv2022

Cyclotron cooling to cryogenic temperature in a Penning-Malmberg trap with a large solid angle acceptance

Magnetized nonneutral plasma composed of electrons or positrons couples to the local microwave environment via cyclotron radiation. The equilibrium plasma temperature depends on the microwave energy density near the cyclotron frequency. Fine copper meshes and cryogenic microwave absorbing material were used to lower the effective temperature of the radiation environment in ASACUSA's Cusp trap, resulting in significantly reduced plasma temperature.

physics.plasm-ph↗

arXiv2022

Minimizing plasma temperature for antimatter mixing experiments

The ASACUSA collaboration produces a beam of antihydrogen atoms by mixing pure positron and antiproton plasmas in a strong magnetic field with a double cusp geometry. The positrons cool via cyclotron radiation inside the cryogenic trap. Low positron temperature is essential for increasing the fraction of antihydrogen atoms which reach the ground state prior to exiting the trap. Many experimental groups observe that such plasmas reach equilibrium at a temperature well above the temperature of the surrounding electrodes. This problem is typically attributed to electronic noise and plasma expansion, which heat the plasma. The present work reports anomalous heating far beyond what can be attributed to those two sources. The heating seems to be a result of the axially open trap geometry, which couples the plasma to the external (300 K) environment via microwave radiation.

physics.plasm-ph↗

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↗

arXiv2020

Measurement of the Principal Quantum Number Distribution in a Beam of Antihydrogen Atoms

The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration plans to measure the ground-state hyperfine splitting of antihydrogen in a beam at the CERN Antiproton Decelerator with initial relative precision of 10-6 or better, to test the fundamental CPT (combination of charge conjugation, parity transformation and time reversal) symmetry between matter and antimatter. This challenging goal requires a polarised antihydrogen beam with a sufficient number of antihydrogen atoms in the ground state. The first measurement of the quantum state distribution of antihydrogen atoms in a low magnetic field environment of a few mT is described. Furthermore, the data-driven machine learning analysis to identify antihydrogen events is discussed.

physics.atom-ph↗

arXiv2020

Characterization of the SIDDHARTA-2 luminosity monitor

A luminosity monitor, based on plastic scintillator detectors, has been developed for the SIDDHARTA-2 experiment aiming to perform high precision measurements of kaonic atoms and was installed in 2020 on the DAFNE $e^+e^-$ collider at LNF (Laboratori Nazionali di Frascati, INFN). The main goal of this system is to provide the~instantaneous and integrated luminosity of the DAFNE facility by measuring the rate of $K^+K^-$ correlated pairs emitted by the phi meson decay. This task requires an accurate timing of the DAQ signals, as well as timing resolution below 1ns, in order to disentangle the $K^\pm$ signals from the background minimum ionizing particles (MIPs) produced during the $e^+e^-$ collisions at DAFNE. In this paper the luminosity monitor concept as well as its laboratory characterization and the first results inside DAFNE are presented.

physics.ins-det↗

arXiv2020

Observation of a $\bar{K}NN$ bound state in the $^3{\rm He} (K^-, Λp)n$ reaction

We have performed an exclusive measurement of the $K^{-}+\! ~^{3}{\rm He} \to Λpn$ reaction at an incident kaon momentum of $1\ {\rm GeV}/c$.In the $Λp$ invariant mass spectrum, a clear peak was observed below the mass threshold of $\bar{K}\!+\!N\!+\!N$, as a signal of the kaonic nuclear bound state, $\bar{K}NN$.The binding energy, decay width, and $S$-wave Gaussian reaction form-factor of this state were observed to be $B_{K} = 42\pm3({\rm stat.})^{+3}_{-4}({\rm syst.})\ {\rm MeV}$, $Γ_{K} = 100\pm7({\rm stat.})^{+19}_{-9}({\rm syst.})\ {\rm MeV}$, and $Q_{K} = 383\pm11({\rm stat.})^{+4}_{-1}({\rm syst.})\ {\rm MeV}/c$, respectively. The total production cross-section of $\bar{K}NN$, determined by its $Λp$ decay mode, was $σ^{tot}_{K} \cdot BR_{Λp} = 9.3\pm0.8({\rm stat.})^{+1.4}_{-1.0}({\rm syst.})\ μ{\rm b}$.We estimated the branching ratio of the $\bar{K}NN$ state to the $Λp$ and $Σ^{0}p$ decay modes as $BR_{Λp}/BR_{Σ^{0}p} \sim 1.7$, by assuming that the physical processes leading to the $ΣN\!N$ final states are analogous to those of $Λpn$.

nucl-ex↗

arXiv2019

Prototype-module of a muon tracker to investigate the Popocatepetl volcano lava dome density-distribution

The study of volcanic inner density distributions using cosmic muons is an innovative method, which is still in a stage of development. This technique can be used to determine the average density along the muon track, as well as the density distribution within a given volume, by measuring the attenuation of the cosmic muon flux going through it. The aim is to study the volcano domes and magmatic conduit systems within a given time-interval. Our first application will be the Popocatepetl, a large active andesitic stratovolcano built in the Trans-Mexican volcanic arc. Its recent activity includes emplacement of a lava dome, with explosions and frequent scoria and ash emissions. This study is part of a longer-term project of volcanic hazard monitoring that includes other Mexican volcanoes, like the Colima. Muon detector design depends on the volume-of-interest dimensions, as well as on the image-taking frequency required to detect dynamic density variations. Our muon-tracker proposal includes 3 planes, each having 16 independent position-sensitive modules consisting on rectangular aluminum tubes ($10x20x320cm^{3}$) filed with a liquid scintillator. The light collection inside each module is carried out using a wave-length-shifting (WLS) fiber matrix, running along the aluminum-tube length, which is bundled together at the tube extremes. The luminous signal readout is carried out using one SiPM optically coupled to the WLS bundle at each modules end. The main detector characteristics, such as time resolution, surface uniformity, and signal amplitude reconstruction using the time-over-threshold technique, will be presented.

physics.ins-det↗

arXiv2019

VIP2 in LNGS - Testing the Pauli Exclusion Principle for electrons with high sensitivity

The VIP2 (VIolation of the Pauli Exclusion Principle) experiment at the Gran Sasso underground laboratory (LNGS) is searching for possible violations of standard quantum mechanics predictions in atoms at very high sensitivity. We investigate atomic transitions with precision X-ray spectroscopy in order to test the Pauli Exclusion Principle (PEP) and therefore the related spin-statistics theorem. We will present our experimental method for the search for "anomalous" (i.e. Pauli-forbidden) X-ray transitions in copper atoms, produced by "new" electrons, which could have tiny probability to undergo Pauli-forbidden transition to the ground state already occupied by two electrons. We will describe the VIP2 experimental setup, which is taking data at LNGS presently. The goal of VIP2 is to test the PEP for electrons with unprecedented accuracy, down to a limit in the probability that PEP is violated at the level of 10$^{-31}$. We will present current experimental results and discuss implications of a possible violation.

quant-ph↗

arXiv2019

K$^-$ multi-nucleon absorption cross sections and branching ratios in $Λ$p and $Σ^0$p final states

The determination of low-energy cross sections and branching ratios of the K$^-$ multi-nucleon absorption processes in $Λ$p and $Σ^0$p final states performed by the AMADEUS collaboration is presented. Low momentum K$^-$ ($p_\mathrm{K} \simeq$ 127 MeV/c) produced at the DA$Φ$NE collider are impinged on a Carbon target within the KLOE detector and the two and three nucleon absorption processes are disentangled by comparing the experimental data to phenomenological calculations. The $Λ$p spectra are interpreted in terms of K$^-$ multi-nucleon absorption processes; the possible contribution of a K$^-$pp bound state is demonstrated to overlap with the two nucleon capture process, its absolute yield thus resulting indistinguishable.

nucl-ex↗

arXiv2019

Development of a compact HAPG crystal Von Hamos X-ray spectrometer forextended and diffused sources

Bragg spectroscopy is one of the best established experimental methods for high energy resolution X-ray measurements; however, this technique is limited to the measurement of photons producedfrom well collimated (tens of microns) or point-like sources and becomes quite inefficient for photonscoming from extended and diffused sources. The possibility to perform simultaneous measurementsof several energies is strongly demanded when low rate signals are expected and single angular scansrequire long exposure times. A prototype of a high resolution and high precision X-ray spectrometerworking also with extended isotropic sources, has been developed by the VOXES collaboration atINFN Laboratories of Frascati, using Highly Annealed Pyrolitic Graphite (HAPG) crystals in a semi- Von Hamos configuration, in which the position detector is rotated with respect to thestandard Von Hamos one, to increase the dynamic energy range. The aim is to deliver a cost effectivesystem having an energy resolution at the level of eV for X-ray energies from about 2 keV up to tensof keV, able to perform sub-eV precision measurements with non point-like sources. The proposedspectrometer has possible applications in several fields, going from fundamental physics to quantummechanics tests, synchrotron radiation and X-FEL applications, astronomy, medicine and industry.In particular, this technique is fundamental for a series of nuclear physics measurements like, forexample, the energies of the exotic atoms radiative transitions which allow to extract fundamentalparameters in the low energy QCD in the strangeness sector. In this work, the working principleof the spectrometer is presented, together with the tests and the results, in terms of resolution andsource, size obtained for Fe(K\alpha1,2), Cu(K\alpha1,2), Ni(Kβ), Zn(K\alpha1,2), Mo(K\alpha1,2) and Nb(Kβ)lines.

physics.ins-det↗

arXiv2019

Wide acceptance measurement of the K$^-$/K$^+$ ratio from Ni+Ni collisions at 1.91A GeV

The FOPI Collaboration at the GSI SIS-18 synchrotron measured charged kaons from central and semi-central collisions of Ni+Ni at a beam energy of 1.91A GeV. We present the distribution of the K$^-$\K$^+$ ratio on the energy vs polar angle plane in the nucleon-nucleon center-of-mass frame, with and without subtraction of the contribution of $ϕ$(1020) meson decays to the K$^-$ yield. The acceptance of the current experiment is substantially wider compared to the previous measurement of the same colliding system. The ratio of K$^-$ to K$^+$ energy spectra is expected to be sensitive to the in-medium modifications of basic kaon properties like mass. Recent results obtained by the HADES Collaboration at 1.23A and 1.76A GeV indicate that after inclusion of the $ϕ$ meson decay contribution to the K$^-$ production no difference between the slopes of the K$^-$ and K$^+$ energy spectra is observed within uncertainties. For our data a linear fit to this ratio obtained after subtraction of the $ϕ$ meson contribution still shows a decrease with kinetic energy, although a constant value cannot be rejected. The contribution of $Λ(1520) \rightarrow p\text{K}^-$ decays estimated from fitting the thermal model to the experimental yields appears to be another factor of moderate relevance.

nucl-ex↗

arXiv2018

A hydrogen beam to characterize the ASACUSA antihydrogen hyperfine spectrometer

The antihydrogen programme of the ASACUSA collaboration at the antiproton decelerator of CERN focuses on Rabi-type measurements of the ground-state hyperfine splitting of antihydrogen for a test of the combined Charge-Parity-Time symmetry. The spectroscopy apparatus consists of a microwave cavity to drive hyperfine transitions and a superconducting sextupole magnet for quantum state analysis via Stern-Gerlach separation. However, the small production rates of antihydrogen forestall comprehensive performance studies on the spectroscopy apparatus. For this purpose a hydrogen source and detector have been developed which in conjunction with ASACUSA's hyperfine spectroscopy equipment form a complete Rabi experiment. We report on the formation of a cooled, polarized, and time modulated beam of atomic hydrogen and its detection using a quadrupole mass spectrometer and a lock-in amplification scheme. In addition key features of ASACUSA's hyperfine spectroscopy apparatus are discussed.t

physics.atom-ph↗

arXiv2018

Hyperfine spectroscopy of hydrogen and antihydrogen in ASACUSA

The ASACUSA collaboration at the Antiproton Decelerator of CERN aims at a precise measurement of the antihydrogen ground-state hyperfine structure as a test of the fundamental CPT symmetry. A beam of antihydrogen atoms is formed in a CUSP trap, undergoes Rabi-type spectroscopy and is detected downstream in a dedicated antihydrogen detector. In parallel measurements using a polarized hydrogen beam are being performed to commission the spectroscopy apparatus and to perform measurements of parameters of the Standard Model Extension (SME). The current status of antihydrogen spectroscopy is reviewed and progress of ASACUSA is presented.

physics.atom-ph↗

arXiv2018

"$\mathbf{{\textit K^-}{\textit p}{\textit p}}$", a ${\overline{K}}$-Meson Nuclear Bound State, Observed in $^{3}{\rm He}({K^-}, Λ p)n$ Reactions

We observed a distinct peak in the $Λp$ invariant mass spectrum of $^{3}{\rm He}(K^-, \, Λp)n$, well below the mass threshold of $m_K + 2 m_p$. By selecting a relatively large momentum-transfer region $q = 350 \sim 650$ MeV/$c$, one can clearly separate the peak from the quasi-free process, $\overline{K}N \rightarrow \overline{K}N$ followed by the non-resonant absorption by the two spectator-nucleons $\overline{K}NN \rightarrow ΛN $. We found that the simplest fit to the observed peak gives us a Breit-Wigner pole position at $B_{\rm {\it Kpp}} = 47 \pm 3 \, (stat.) \,^{+3}_{-6} \,(sys.)$ MeV having a width $Γ_{\rm {\it Kpp}} = 115 \pm 7 \, (stat.) \,^{+10}_{-9} \,(sys.)$ MeV, and the $S$-wave Gaussian reaction form-factor parameter $Q_{\rm {\it Kpp}} = 381 \pm 14 \, (stat.)\,^{+57}_{-0} \,(sys.)$ MeV/$c$, as a new form of the nuclear bound system with strangeness -- "$K^-pp$".

nucl-ex↗

arXiv2018

Determination of N* amplitudes from associated strangeness production in p+p collisions

We present the first determination of the energy-dependent production amplitudes of N$^{*}$ resonances with masses between 1650 MeV/c$^{2}$ and 1900 MeV/c$^{2}$ for an excess energy between $0$ and $600$ MeV. A combined Partial Wave Analysis of seven exclusively reconstructed data samples for the reaction p+p $\rightarrow pKΛ$ measured by the COSY-TOF, DISTO, FOPI and HADES collaborations in fixed target experiments at kinetic energies between 2.14 and 3.5 GeV is used to determine the amplitude of the resonant and non-resonant contributions.

nucl-ex↗

arXiv2018

Detector setup of the VIP2 Underground Experiment at LNGS

The VIP2 experiment tests the Pauli Exclusion Principle with high sensitivity, by searching for Pauli-forbidden atomic transitions from the 2p to the 1s shell in copper at about 8keV. The transition energy of Pauli-forbidden K X-rays is shifted by about 300 eV with respect to the normal allowed K line. This energy difference can be resolved using Silicon Drift Detectors. The data for this experiment is taken in the Gran Sasso underground laboratory (LNGS), which provides shielding from cosmic radiation. An overview of the detection system of the VIP2 experiment will be given. This includes the Silicon Drift Detectors used as X-ray detectors which provide an energy resolution of around 150 eV at 6 keV and timing information for active shielding. Furthermore, the low maintenance requirement makes them excellent X-ray detectors for the use in an underground laboratory. The VIP2 setup will be discussed which consists of a high current target system and a passive as well as an active shielding system using plastic scintillators read out by Silicon Photomultipliers.

physics.ins-det↗

arXiv2018

VOXES: a high precision X-ray spectrometer for diffused sources with HAPG crystals in the 2-20 keV range

Bragg spectroscopy is one of the best established experimental methods for high energy resolution X-ray measurements and has been widely used in several fields, going from fundamental physics to quantum mechanics tests, synchrotron radiation and X-FEL applications, astronomy, medicine and industry. However, this technique is limited to the measurement of photons produced from well collimated or point-like sources and becomes quite inefficient for photons coming from extended and diffused sources like those,for example, emitted in the exotic atoms radiative transitions. The VOXES project's goal is to realise a prototype of a high resolution and high precision X-ray spectrometer, using Highly Annealed Pyrolitic Graphite (HAPG) crystals in the Von Hamos configuration, working also for extended sources. The aim is to deliver a cost effective system having an energy resolution at the level of eV for X rays energies from about 2 keV up to tens of keV, able to perform sub-eV precision measurements with non point-like sources. In this paper, the working principle of VOXES, together with first results, are presented.

physics.ins-det↗