arXiv subjects

E. Czerwiński

Publications and source records attributed to E. Czerwiński.

At least 37 records · Page 2Linked to original sources

arXiv2018

Measurement of the charge asymmetry for the $K_S \rightarrow πe ν$ decay and test of CPT symmetry with the KLOE detector

Using 1.63 fb$^{-1}$ of integrated luminosity collected by the KLOE experiment about $7\times 10^4$ $K_S \rightarrow π^{\pm}e^{\mp}ν$ decays have been reconstructed. The measured value of the charge asymmetry for this decay is $A_S = (-4.9 \pm 5.7_{stat} \pm 2.6_{syst}) \times 10^{-3}$, which is almost twice more precise than the previous KLOE result. The combination of these two measurements gives $A_S = (-3.8 \pm 5.0_{stat} \pm 2.6_{syst}) \times 10^{-3}$ and, together with the asymmetry of the $K_L$ semileptonic decay, provides significant tests of the CPT symmetry. The obtained results are in agreement with CPT invariance.

hep-ex↗

arXiv2018

On the Production of an Isotensor Dibaryon in the $pp \to ppπ^+π^-$ Reaction

Exclusive measurements of the quasi-free $pp \to ppπ^+π^-$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $T_p = 1.08 - 1.36$ GeV ($\sqrt s$ = 2.35 - 2.46 GeV), which includes the regions of $N^*(1440)$ and $Δ(1232)Δ(1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with experimental differential cross sections and underpredict substantially the measured total cross section. An isotensor $ΔN$ dibaryon resonance with $I(J^P) = 2(1^+)$ produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong and more recently calculated by Gal and Garcilazo.

nucl-ex↗

arXiv2018

Combined limit on the production of a light gauge boson decaying into $μ^+μ^-$ and $π^+π^-$

We searched for the $μ^+μ^-$ decay of a light vector gauge boson, also known as dark photon, in the $e^+ e^- \to μ^+ μ^- γ_{\rm ISR}$ process by means of the Initial State Radiation (ISR) method. We used 1.93~fb$^{-1}$ of data collected by the KLOE experiment at the DA$Φ$NE $ϕ$-factory. No structures have been observed over the irreducible $μ^+ μ^-$ background. A 90\% CL limit on the ratio $\varepsilon^2=α^{\prime}/α$ between the dark coupling constant and the fine structure constant of $ 3\times 10^{-6}-2\times 10^{-7}$ has been set in the dark photon mass region between 519 MeV and 973 MeV. This new limit has been combined with the published result obtained investigating the hypothesis of the dark photon decaying into hadrons in $e^+ e^- \to π^+ π^- γ_{\rm ISR}$ events. The combined 90\% CL limit increases the sensitivity especially in the $ρ-ω$ interference region and excludes $\varepsilon^2$ greater than $(13-2)\times 10^{-7}$. For dark photon masses greater than 600 MeV the combined limit is lower than 8~$\times\, 10^{-7}$ resulting more stringent than present constraints from other experiments.

hep-ex↗

arXiv2018

Evaluation of Single-Chip, Real-Time Tomographic Data Processing on FPGA - SoC Devices

A novel approach to tomographic data processing has been developed and evaluated using the Jagiellonian PET (J-PET) scanner as an example. We propose a system in which there is no need for powerful, local to the scanner processing facility, capable to reconstruct images on the fly. Instead we introduce a Field Programmable Gate Array (FPGA) System-on-Chip (SoC) platform connected directly to data streams coming from the scanner, which can perform event building, filtering, coincidence search and Region-Of-Response (ROR) reconstruction by the programmable logic and visualization by the integrated processors. The platform significantly reduces data volume converting raw data to a list-mode representation, while generating visualization on the fly.

physics.ins-det↗

arXiv2018

An Isotensor Dibaryon in the $pp \to ppπ^+π^-$ Reaction?

Exclusive measurements of the quasi-free $pp \to ppπ^+π^-$ reaction have been carried out at WASA@COSY by means of $pd$ collisions at $T_p$ = 1.2 GeV. Total and differential cross sections have been extracted covering the energy region $T_p = 1.08 - 1.36$ GeV, which is the region of $N^*(1440)$ and $Δ(1232)Δ(1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor $ΔN$ dibaryon resonance with $I(J^P) = 2(1^+)$ produced associatedly with a pion is able to overcome these deficiencies.

nucl-ex↗

arXiv2018

Combination of KLOE $σ\big(e^+e^-\rightarrowπ^+π^-γ(γ)\big)$ measurements and determination of $a_μ^{π^+π^-}$ in the energy range $0.10 < s < 0.95$ GeV$^2$

The three precision measurements of the cross section $σ\big(e^+e^-\rightarrowπ^+π^-γ(γ)\big)$ using initial state radiation by the KLOE collaboration provide an important input for the prediction of the hadronic contribution to the anomalous magnetic moment of the muon. These measurements are correlated for both statistical and systematic uncertainties and, therefore, the simultaneous use of these measurements requires covariance matrices that fully describe the correlations. We present the construction of these covariance matrices and use them to determine a combined KLOE measurement for $σ\big(e^+e^-\rightarrowπ^+π^-γ(γ)\big)$. We find, from this combination, a two-pion contribution to the muon magnetic anomaly in the energy range $0.10 < s < 0.95$ GeV$^2$ of $a_μ^{π^+π^-} = (489.8 \pm 1.7_{\rm stat} \pm 4.8_{\rm sys} ) \times 10^{-10}$.

hep-ex↗

arXiv2018

Backward single-pion production in the $\boldsymbol{pd\rightarrow {}^3\textrm{He}\,π^0}$ reaction with WASA-at-COSY

New data on the production of single neutral pions in the $pd\rightarrow{}^3\textrm{He}\,π^0$ reaction are presented. For fifteen proton beam momenta between $p_p=1.60\;\textrm{GeV}/c$ and $p_p=1.74\;\textrm{GeV}/c$, differential cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.

nucl-ex↗

arXiv2018

Feasibility study of the time reversal symmetry tests in decays of metastable positronium atoms with the J-PET detector

This article reports on the feasibility of testing of the symmetry under reversal in time in a purely leptonic system constituted by positronium atoms using the J-PET detector. The present state of T symmetry tests is discussed with an emphasis on the scarcely explored sector of leptonic systems. Two possible strategies of searching for manifestations of T violation in non-vanishing angular correlations of final state observables in the decays of metastable triplet states of positronium available with J-PET are proposed and discussed. Results of a pilot measurement with J-PET and assessment of its performance in reconstruction of three-photon decays are shown along with an analysis of its impact on the sensitivity of the detector for the determination of T -violation sensitive observables.

physics.ins-det↗

arXiv2018

Importance of d-wave contributions in the charge symmetry breaking reaction $dd \to {}^4\text{He}π^0$

This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction $dd \to {}^4\text{He}π^0$ using the WASA-at-COSY detector setup at an excess energy of $Q = 60$ MeV. The determined differential cross section can be parametrized as $\text{d}σ/\text{d}Ω= a + b\cos^{2}θ^*$, where $θ^*$ is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are $a = \left(1.55 \pm 0.46 (\text{stat}) ^{+0.32}_{-0.8} (\text{syst}) \right)$ pb/sr and $b = \left(13.1 \pm 2.1 (\text{stat}) ^{+1.0}_{-2.7} (\text{syst})\right)$ pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the $Δ$ isobar to the $dd \to {}^4\text{He}π^0$ reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions.

nucl-ex↗

arXiv2018

Towards 2+1 photon tomography: Energy-based selection of two 511 keV photons and a prompt photon with the J-PET scanner

The possibility to separate signals caused by 511 keV photons created in annihilation of electron-positron pairs and the so-called prompt photons from nuclei de- excitation is investigated. It could potentially be used to improve the quality of reconstructed images in the J-PET scanner in 2+1 photon tomography. Firstly, a research is conducted for several radioisotopes that decay via \b{eta}+ decay followed by de-excitation of an excited nucleus. Efficiency, purity and false positive rate are calculated for each isotope as a function of energy deposited threshold, with a hypothesis that signals caused by 511 keV photons deposit smaller values of energy than 1 z 13the selected threshold, while prompt photons deposit larger energy than the threshold. Analysis of the results accompanied with physical properties of radioisotopes suggests using 44 Sc, which is the most promising candidate for medical applications. With the use of GATE and J-POS simulation software, in-phantom scattering was introduced and the best energy deposited threshold value was estimated to be approximately 375 keV. It corresponds to almost 100% efficiency for 511 keV signals, 75% purity for 511 keV photons, and approximately 70% efficiency and purity for prompt photons.

physics.med-ph↗

arXiv2018

Search for $C$ violation in the decay $η\rightarrowπ^0+e^++e^-$ with WASA-at-COSY

We report on the investigation of the rare decay $η\rightarrowπ^0+\text{e}^++\text{e}^-$ which is of interest to study both $C$ violation in the electromagnetic interaction and to search for contributions from physics beyond the Standard Model, since the allowed decay via a two-photon intermediate state is strongly suppressed. The experiment has been performed using the WASA-at-COSY installation, located at the COSY accelerator of the Forschungszentrum Jülich, Germany. In total $3\times10^7$ events of the reaction $\text{p}+\text{d}\rightarrow{^3\text{He}}+η$ have been recorded at an excess energy of $Q = 59.8\,\textrm{MeV}$. Based on this data set the $C$ parity violating decay $η\rightarrowπ^0+γ^*\rightarrowπ^0+\textrm{e}^++\textrm{e}^-$ via a single-photon intermediate state has been searched for, resulting in new upper limits of $Γ\left(η\rightarrowπ^0+\textrm{e}^++\textrm{e}^-\right)/ Γ\left(η\rightarrowπ^++π^-+π^0\right) < 3.28\times10^{-5}$ and $Γ\left(η\rightarrowπ^0+\textrm{e}^++\textrm{e}^-\right)/ Γ\left(η\rightarrow\textrm{all}\right) < 7.5\times10^{-6}\ (\textrm{CL} = 90\,\%)$, respectively.

hep-ex↗

arXiv2018

Total and differential cross sections of $η$-production in proton-deuteron fusion for excess energies between $Q_η=13\;\text{MeV}$ and $Q_η=81\;\text{MeV}$

New data on both total and differential cross sections of the production of $η$ mesons in proton-deuteron fusion to ${}^3\text{He}\,η$ in the excess energy region $13.6\;\text{MeV}\leq Q_η\leq 80.9\;\text{MeV}$ are presented. These data have been obtained with the WASA-at-COSY detector setup located at the Forschungszentrum Jülich, using a proton beam at 15 different beam momenta between $p_p = 1.60\;\text{GeV}/c$ and $p_p = 1.74\;\text{GeV}/c$. While significant structure of the total cross section is observed in the energy region $20\;\text{MeV}\lesssim Q_η\lesssim 60\;\text{MeV}$, a previously reported sharp variation around $Q_η\approx 50\;\text{MeV}$ cannot be confirmed. Angular distributions show the typical forward-peaking that was reported elsewhere. For the first time, it is possible to study the development of these angular distributions with rising excess energy over a large interval.

nucl-ex↗

arXiv2017

Human Tissues Investigation Using PALS Technique

Samples of uterine leiomyomatis and normal tissues taken from patients after surgery were investigated using the Positron Annihilation Lifetime Spectroscopy (PALS). Significant differences in all PALS parameters between normal and diseased tissues were observed. For all studied patients, it was found that the values of the free annihilation and ortho-positronium lifetime are larger for the tumorous tissues than for the healthy ones. For most of the patients, the intensity of the free annihilation and ortho-positronium annihilation was smaller for the tumorous than for the healthy tissues. For the first time, in this kind of studies, the $3γ$ fraction of positron annihilation was determined to describe changes in the tissue porosity during morphologic alteration.

physics.med-ph↗

arXiv2017

Commissioning of the J-PET detector for studies of decays of positronium atoms

The Jagiellonian Positron Emission Tomograph (J-PET) is a detector for medical imaging of the whole human body as well as for physics studies involving detection of electron-positron annihilation into photons. J-PET has high angular and time resolution and allows for measurement of spin of the positronium and the momenta and polarization vectors of annihilation quanta. In this article, we present the potential of the J-PET system for background rejection in the decays of positronium atoms.

physics.ins-det↗

arXiv2017

J-PET: a new technology for the whole-body PET imaging

The Jagiellonian Positron Emission Tomograph (J-PET) is the first PET built from plastic scintillators. J-PET prototype consists of 192 detection modules arranged axially in three layers forming a cylindrical diagnostic chamber with the inner diameter of 85 cm and the axial field-of-view of 50 cm. An axial arrangement of long strips of plastic scintillators, their small light attenuation, superior timing properties, and relative ease of the increase of the axial field-of-view opens promising perspectives for the cost effective construction of the whole-body PET scanner, as well as construction of MR and CT compatible PET inserts. Present status of the development of the J-PET tomograph will be presented and discussed.

physics.ins-det↗

arXiv2017

Introduction of total variation regularization into filtered backprojection algorithm

In this paper we extend the state-of-the-art filtered backprojection (FBP) method with application of the concept of Total Variation regularization. We compare the performance of the new algorithm with the most common form of regularizing in the FBP image reconstruction via apodizing functions. The methods are validated in terms of cross-correlation coefficient between reconstructed and real image of radioactive tracer distribution using standard Derenzo-type phantom. We demonstrate that the proposed approach results in higher cross-correlation values with respect to the standard FBP method.

physics.med-ph↗

arXiv2017

Three-dimensional image reconstruction in J-PET using Filtered Back Projection method

We present a method and preliminary results of the image reconstruction in the Jagiellonian PET tomograph. Using GATE (Geant4 Application for Tomographic Emission), interactions of the 511 keV photons with a cylindrical detector were generated. Pairs of such photons, flying back-to-back, originate from e+e- annihilations inside a 1-mm spherical source. Spatial and temporal coordinates of hits were smeared using experimental resolutions of the detector. We incorporated the algorithm of the 3D Filtered Back Projection, implemented in the STIR and TomoPy software packages, which differ in approximation methods. Consistent results for the Point Spread Functions of ~5/7,mm and ~9/20, mm were obtained, using STIR, for transverse and longitudinal directions, respectively, with no time of flight information included.

physics.ins-det↗

arXiv2017

Calculation of time resolution of the J-PET tomograph using the Kernel Density Estimation

In this paper we estimate the time resolution of the J-PET scanner built from plastic scintillators. We incorporate the method of signal processing using the Tikhonov regularization framework and the Kernel Density Estimation method. We obtain simple, closed-form analytical formulas for time resolutions. The proposed method is validated using signals registered by means of the single detection unit of the J-PET tomograph built out from 30 cm long plastic scintillator strip. It is shown that the experimental and theoretical results, obtained for the J-PET scanner equipped with vacuum tube photomultipliers, are consistent.

physics.ins-det↗