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R. Siudak

Publications and source records attributed to R. Siudak.

At least 37 records · Page 2Linked to original sources
arXiv2012

ABC Resonance Structure in the Double-Pionic Fusion to 4He

Exclusive and kinematically complete high-statistics measurements of the double pionic fusion reaction $dd \to ^4$He$π^0π^0$ have been performed in the energy range 0.8 - 1.4 GeV covering thus the region of the ABC effect, which denotes a pronounced low-mass enhancement in the $ππ$-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY. Similar to the observation in the basic $pn \to d π^0π^0$ reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. The maximum occurs at m=2.37 GeV + 2$m_N$, i.e. at the same position as in the basic reaction. The observed resonance width $Γ\approx$ 160 MeV can be understood from broadening due to Fermi motion of the nucleons in initial and final nuclei together with collision damping. Differential cross sections are described equally well by the hypothesis of a $pn$ resonance formation during the reaction process.

nucl-ex↗
arXiv2012

Technical Design Report for the: PANDA Straw Tube Tracker

This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM-stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy-loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.

physics.ins-det↗
arXiv2011

Strangeness Production in Hadron Reactions

The paper gives an overview of strangeness-production experiments at the Cooler Synchrotron COSY. Results on kaon-pair and $ϕ$ meson production in $pp$, $pd$ and $dd$ collisions, hyperon-production experiments and $Λp$ final-state interaction studies are presented as well as a search for a strangeness $S=-1$ resonance in the $Λp$ system.

hep-ex↗
arXiv2011

Exclusive Measurement of the eta --> pi+ pi- gamma Decay

An exclusive measurement of the decay eta --> pi+ pi- gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction pd --> 3He X at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on 13340\pm140 events after background subtraction. The measured pion angular distribution is consistent with a relative p-wave of the two-pion system, whereas the measured photon energy spectrum was found at variance with the simplest gauge invariant matrix element of eta --> pi+ pi- gamma. A parameterization of the data can be achieved by the additional inclusion of the empirical pion vector form factor multiplied by a first-order polynomial in the squared invariant mass of the pi+ pi- system.

nucl-ex↗
arXiv2011

Sequential and simultaneous emission of fragments from p+Al collisions

The energy and angular dependencies of double differential cross sections d^2sigma/dOmegadE were measured for p,d,t,^{3,4,6}He,^{6,7,8}Li,{7,9,10}Be, and ^{10,11,12}B produced in collisions of 1.2, 1.9, and 2.5 GeV protons with an Al target. The spectra and angular distributions of Li, Be, and B isotopes indicate a presence of two contributions: an isotropic, low energy one which is attributed to the evaporation of particles from excited remnants of the intranuclear cascade, and an anisotropic part which is interpreted to be due to multifragmentation of the remnants. It was found that such a hypothesis leads to very good description of spectra and angular distributions of all intermediate mass fragments (^6He-^{12}B) using the critical value of the excitation energy per nucleon as a single parameter, varying slowly with the beam energy.

nucl-ex↗
arXiv2011

Upper limits for a narrow resonance in the reaction p + p -> K^+ + (Lambda p)

The reaction pp -> K^+ + (Lambda p) has been measured at T_p = 1.953 GeV and Θ= 0 deg with a high missing mass resolution in order to study the Lambda p final state interaction. Narrow S = -1 resonances predicted by bag model calculations are not visible in the missing mass spectrum. Small structures observed in a previous experiment are not confirmed. Upper limits for the production cross section of a narrow resonance are deduced for missing masses between 2058 and 2105 MeV/c^2.

hep-ex↗
arXiv2011

ABC Effect in Basic Double-Pionic Fusion --- Observation of a new resonance?

We report on a high-statistics measurement of the basic double pionic fusion reaction $pn \to dπ^0π^0$ over the energy region of the so-called ABC effect, a pronounced low-mass enhancement in the $ππ$-invariant mass spectrum. The measurements were performed with the WASA detector setup at COSY. The data reveal the ABC effect to be associated with a Lorentzian shaped energy dependence in the integral cross section. The observables are consistent with a resonance with $I(J^P) =0(3^+)$ in both $pn$ and $ΔΔ$ systems. Necessary further tests of the resonance interpretation are discussed.

nucl-ex↗
arXiv2010

Study of the $\bm{p+^6}$Li$\bm{\toη+^7}$Be reaction 11.3 MeV above threshold

The cross section for the reaction $p+^6\text{Li}\toη+^7\text{Be}$ was measured at an excess energy of 11.28 MeV above threshold by detecting the recoiling $^7$Be nuclei. A dedicated set of focal plane detectors was built for the magnetic spectrograph Big Karl and was used for identification and four momentum measurement of the $^7$Be. A differential cross section of $\frac{dσ}{dΩ}=(0.69\pm{0.20}\text{(stat.)}\pm 0.20\text{(syst.)})\text{nb/sr}$ for the ground state plus the 1/2$^-$ was measured. The result is compared to model calculations.

nucl-ex↗
arXiv2010

Cross section of the $pp\to K^+Σ^+n$ reaction close to threshold

We have measured inclusive data on $K^+$-meson production in $pp$ collisions at COSY Jülich close to the hyperon production threshold and determined the hyperon-nucleon invariant mass spectra. The spectra were decomposed into three parts: $Λp$, $Σ^0p$ and $Σ^+n$. The cross section for the $Σ^+n$ channel was found to be much smaller than a previous measurement in that excess energy region. The data together with previous results at higher energies are compatible with a phase space dependence.

hep-ex↗
arXiv2010

High resolution study of the Lambda p final state interaction in the reaction p + p -> K+ + (Lambda p)

The reaction pp -> K+ + (Lambda p) was measured at Tp=1.953 GeV and Theta = 0 deg with a high missing mass resolution in order to study the Lambda p final state interaction. The large final state enhancement near the Lambda p threshold can be described using the standard Jost-function approach. The singlet and triplet scattering lengths and effective ranges are deduced by fitting simultaneously the Lambda p invariant mass spectrum and the total cross section data of the free Lambda p scattering.

nucl-ex↗
arXiv2009

Evidence of Ni break-up from total production cross sections in p+Ni collisions

The total production cross sections of light charged particles (LCPs), intermediate mass fragments (IMFs) and heavy reaction products of p+Ni collisions available in the literature have been compared with predictions of a two-step model in the proton beam energy range from reaction threshold up to approximately 3 GeV. Model cross sections were calculated assuming, that the reaction proceeds via an intranuclear cascade of nucleon-nucleon collisions followed by evaporation of particles from an equilibrated, heavy target residuum. The shape of the excitation functions was well described by model calculations for all reaction products. The magnitude of the cross sections was reasonably well reproduced for heavy reaction products, i.e. for nuclei heavier than Al, but the cross sections for lighter products were systematically underestimated. This fact was used as an argument in favor of a significant break-up contribution to the reaction mechanism. The present conclusions are supported by recently published results of investigations of differential cross sections in p+Ni collisions, which showed that hypothesis of the break-up of target nucleus is indispensable for a good reproduction of d2 sigma/dOmega dE for LCPs and IMFs.

nucl-ex↗
arXiv2009

Event Reconstruction for a DIRC

Monte Carlo simulations were made for a possible DIRC at the WASA detector at COSY. A statistical method for pattern recognition is presented and the possible angle resolution and velocity precision achieved are discussed.

physics.data-an↗
arXiv2009

Variation of nonequilibrium processes in p+Ni system with beam energy

The energy and angular dependence of double differential cross sections dsigma/dOmega dE were measured for p, d, t, 3,4He, 6,7Li, 7,9Be, and 10,11B produced in collisions of 0.175 GeV protons with Ni target. The analysis of measured dfferential cross sections allowed to extract total production cross sections for ejectiles listed above. The shape of the spectra and angular distributions indicate the presence of other nonequilibrium processes besides the emission of nucleons from the intranuclear cascade, and besides the evaporation of various particles from remnants of intranuclear cascade. These nonequilibrium processes consist of coalescence of nucleons into light charged particles during the intranuclear cascade, of the fireball emission which contributes to the cross sections of protons and deuterons, and of the break-up of the target nucleus which leads to the emission of intermediate mass fragments. All such processes were found earlier at beam energies 1.2, 1.9, and 2.5 GeV for Ni as well as for Au targets, however, significant differences in properties of these processes at high and low beam energy are observed in the present study.

nucl-ex↗
arXiv2009

Comparison of nonequilibrium processes in p+Ni and p+Au collisions at GeV energies

The energy and angular dependence of double differential cross sections d2sigma/dOmega dE were measured for p, d, t, 3,4,6He, 6,7,8Li, 7,9,10Be, 10,11B, and C produced in collisions of 1.2, 1.9, and 2.5 GeV protons with a Ni target. The shape of the spectra and angular distributions does almost not change whereas the absolute value of the cross sections increases by a factor about 1.7 for all ejectiles in this beam energy range. It was found that energy and angular dependencies of the cross sections cannot be reproduced by the microscopic model of intranuclear cascade with coalescence of nucleons and the statistical model for evaporation of particles from excited, equilibrated residual nuclei. The inclusion of nonequilibrium processes, described by a phenomenological model of the emission from fast and hot moving sources, resulting from break-up of the target nucleus by impinging proton, leads to very good reproduction of data. Cross sections of these processes are quite large, exhausting approximately half of the total production cross sections. Due to good reproduction of energy and angular dependencies of d2sigma/dOmega dE by model calculation it was possible to determine total production cross sections for all studied ejectiles. Results obtained in this work point to the analogous reaction mechanism for proton induced reactions on Ni target as that observed previously for Au target in the same beam energy range.

nucl-ex↗
arXiv2009

Technical Design Report for the PANDA Solenoid and Dipole Spectrometer Magnets

This document is the Technical Design Report covering the two large spectrometer magnets of the PANDA detector set-up. It shows the conceptual design of the magnets and their anticipated performance. It precedes the tender and procurement of the magnets and, hence, is subject to possible modifications arising during this process.

physics.ins-det↗
arXiv2009

Precision measurements of the pp\to π^+pn and pp\to π^+d reactions: importance of long-range and tensor force effects

Inclusive measurements of pion production in proton--proton collisions in the forward direction were undertaken at 400 and 600 MeV at COSY using the Big Karl spectrograph. The high resolution in the $π^+$ momentum ensured that there was an unambiguous separation of the $pp\to π^+d/π^+pn$ channels. Using these and earlier data, the ratio of the production cross sections could be followed through the $Δ$ region and compared with the predictions of final state interaction theory. Deviations are strongly influenced by long-range terms in the production operator and the tensor force in the final $pn$ system. These have been investigated in a realistic $pp\toπ^+d/π^+pn$ calculation that includes $S \rightleftharpoons D$ channel coupling between the final nucleons. A semi-quantitative understanding of the observed effects is achieved.

nucl-ex↗
arXiv2009

Physics Performance Report for PANDA: Strong Interaction Studies with Antiprotons

To study fundamental questions of hadron and nuclear physics in interactions of antiprotons with nucleons and nuclei, the universal PANDA detector will be built. Gluonic excitations, the physics of strange and charm quarks and nucleon structure studies will be performed with unprecedented accuracy thereby allowing high-precision tests of the strong interaction. The proposed PANDA detector is a state-of-the art internal target detector at the HESR at FAIR allowing the detection and identification of neutral and charged particles generated within the relevant angular and energy range. This report presents a summary of the physics accessible at PANDA and what performance can be expected.

hep-ex↗