J. Pätzold's research while affiliated with University of Tuebingen and other places
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Publications (34)
The WASA 4π multidetector system, aimed at investigating light meson production in light ion collisions and η meson rare decays at the CELSIUS storage ring in Uppsala is presented. A unique feature of the system is the use of hydrogen pellets as internal targets for the first time. A detailed description of the design, together with the anticipated...
A discussion on the 4π multidetector system for investigation of η-meson rare decays at the Uppsala CELSIUS storage ring was presented. The system includes a Central Detector for particles scattered isotropically, a Pellet Target system and a Forward detector, for particles scattered at angles below 18°, together with a Tagging Spectrometer for He...
The CELSIUS/WASA experiment is now finishing its commissioning phase and has started regular data taking in autumn 2001. Results from a first analysis of data samples from an experimental run at a beam energy of Tp = 1360 MeV in September 2001 are presented. The results show the ability to tag π0 and η production events. For 2π0 production a large...
The WASA detector located at the CELSIUS storage ring of the The Svedberg Laboratory in Uppsala has recently finished its commissioning phase and is in full operation. An unique internal pellet-target system together with a detector covering a solid angle close to 4π steradians gives opportunities to study the rare decays of the π0 and the eta; mes...
Analyzing powers of pion–proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS and a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for π+p scattering, and at 67.3 and 87.2 MeV for...
Exclusive measurements of the two-pion production channel
$pp \rightarrow pp\pi^ + \pi^-$
have been carried out near threshold at CELSIUS with the PROMICE/WASA detector. They reveal
$pp \rightarrow pp^*(1440)\rightarrow pp\sigma \rightarrow pp(\pi^ + \pi^-)_{I = \ell = 0}$
as the dominant process at these energies, however, the data exhibit also...
This version is available at the following Publisher URL: http://prc.aps.org
Exclusive measurements of the p p -> p p pi+ pi- reaction have been carried out at Tp = 775 MeV at CELSIUS using the PROMICE/WASA setup. Together with data obtained at lower energy they point to a dominance of the Roper excitation in this process. From the observed interference of its decay routes N* -> N sigma and N* -> Delta pi -> N sigma their e...
The status on the search for NN-decoupled
NNpNN\pi
-resonances is reviewed with regard to recent experimental searches in the pionic double-charge exchange in nuclei, the two-pion production in nucleon-nucleon collisions, the photo pion-production on the deuteron and the electro pion-production in nuclei.
The status on the search for the as of yet hypothetical NN-decoupled NNpi resonance d' is reviewed with regard to recent experimental searches in the pionic double charge exchange in nuclei, the two-pion production in nucleon-nucleon collisions, the photo pion-production on the deuteron and the electro pion-production in nuclei.
Narrow structures in the range of a few MeV have been searched for in ppπ+ and ppπ− invariant mass spectra (Mppπ+ and Mppπ−) obtained from exclusive measurements of the pp→ppπ+π− reaction at Tp=725,750 and 775 MeV using the PROMICE/WASA detector at CELSIUS. The selected reaction is particularly well suited for the search for dibaryon resonances dec...
The pp-->pp pi(+) pi(-) reaction has been measured exclusively near threshold at CELSIUS. The total cross sections are nearly an order of magnitude lower than expected from previous inclusive measurements. The differential cross sections reveal pp-->pp(*)(1440)-->pp sigma = pp(pi(+)pi(-))(I = l = 0) as the dominant process as well as significant co...
The two-pion production in proton-proton collisions in vacuum has been
measured for the first time exclusively in the energy range
Tp=650-750 MeV with the WASA/PROMICE detector at CELSIUS. The
differential cross sections reveal
pp-->pp*(1440)-->ppσ-->pp(π-π+)l=l=0
to be the dominant process with a significant contribution from the path
pp-->pp*(144...
The experimental results for the (π+,π-)
reaction on nuclei obtained in recent years reveal clear systematic
features of this reaction. New data on 7Li, 12C,
16O, and 56Fe supplementing the existing data base
are presented. The data on 12C are partly at variance with
previous results. The dependence of the cross sections on incident
energy, scatter...
With the PROMICE/WASA detector setup at CELSIUS the reaction pp → NNππ has been measured in the energy range from 650 to 775 MeV. These data constitute the first exclusive high-statistics measurements on a pure hydrogen target, supplying both differential and integral cross sections. Most of the differential spectra for pp → ppπ-π+ are close to pha...
The reaction pp -> NNpipi has been measured close to threshold in the energy range from 650 to 775 MeV using the PROMICE/WASA setup at CELSIUS. These data constitute the first exclusive high-statistics measurements of this reaction on a pure hydrogen target, supplying both differential and integral cross sections. The obtained total cross sections...
The design and testing of a π/μ identifier suitable for use in pion–proton elastic scattering experiments in the momentum range 65–160 MeV/c is described. A neural network technique is used for particle identification. The apparatus (a multilayer scintillator stack) was found to have a particle identification efficiency of better than 98%.
The assembly of the WASA 4π detector at the The Svedberg Laboratory in Uppsala is now completed. The superconducting solenoid, the vacuum chambers and all of the sensitive parts of the detector have been installed at the CELSIUS accelerator and storage ring. The pellet generator, providing internal hydrogen (and deuterium) targets, has been install...
With the PROMICE/WASA detector setup at CELSIUS the reaction {pp --> NNpi pi} has been measured in the energy range from 650 to 775 MeV. These data constitute the first exclusive high-statistics measurements on a pure hydrogen target, supplying both differential and integral cross sections. Most of the differential spectra for {pp --> pppi -pi + }...
The design and testing of a /pi/mu identifier suitable for use in pion-proton elastic scattering experiments in the momentum range 65-160 MeV//c is described. A neural network technique is used for particle identification. The apparatus (a multilayer scintillator stack) was found to have a particle identification efficiency of better than 98%.
The WASA (Wide Angle Shower Apparatus) is a new detector system with very high acceptance presently being commisioned at the CELSIUS storage ring located at The Svedberg Laboratory in Uppsala. It has been designed to study rare decays of light mesons with sensitivity down to 10-9 in the branching ratio. It will also allow for unprecedented quality...
Using the CHAOS spectrometer at TRIUMF pion momentum spectra and angular distributions were measured for the 3He(π−,π+) reaction at incident energies from 65 to 120 MeV and total cross sections were deduced. The data are compared to Monte Carlo simulations for the conventional reaction process as well as to predictions for the production of the hyp...
Differential cross sections of the reactions pp→dπ+ and pp→pnπ+ have been measured at Tp=400 MeV by detecting the charged ejectiles in the angular range 4°≤ΘLab≤21°. The deduced total cross sections agree well with those published previously for neighbouring energies. The invariant mass spectra are observed to be strongly affected by Δ production a...
Recently, it has been proposed that the observed anomaly in the time distribution of neutrino induced reactions, reported by the KARMEN Collaboration, can be interpreted as a signal from an exotic muon decay branch μ+→e+X. It has been shown that this hypothesis gives an acceptable fit to the KARMEN data if the boson X has a mass of mX=103.9MeV/c2,...
A search for the production of a bound trineutron state has been performed using the reaction 3He(π−,π+)nnn at incident pion energies of 65, 75, and 120 MeV. No evidence for the existence of the 3n was found, and an upper limit for the production cross section of approximately 30 nb/sr (2σ confidence level) was obtained.
The reaction 7Li(π+,π−)7B has been measured at incident pion energies of 30–90 MeV. 7Li constitutes the lightest target nucleus, where the pionic charge exchange may proceed as a binary reaction to a discrete final state. Like in the Δ-resonance region the observed cross sections are much smaller than expected from the systematics found for heavier...
Recently, it has been proposed that the observed anomaly in the time distribution of neutrino induced reactions, reported by the KARMEN collaboration, can be interpreted as a signal from an exotic muon decay branch mu+ to e+ X. It has been shown that this hypothesis gives an acceptable fit to the KARMEN data if the boson X has a mass of m_X=103.9Me...
The pionic double charge exchange reaction on nuclei is reviewed. The observed systematics in the data points to a large sensitivity to short-range nucleon-nucleon correlations in nuclei --- as anticipated since long for this genuine two-nucleon process. This is particularly true for non-analog transitions, which do not contain the mean-field drive...
The reaction Nb-93(pi(+),pi(-))Te-93 has been measured in the energy range T-pi = 30-60 MeV at various scattering angles. At all energies the groundstate transition could be observed, whereas the transition to the double isobaric analog state has been identified unambiguously only at T-pi = 50 MeV. The groundstate transition exhibits a pronounced r...
The reaction 93Nb(π+,π−)93Te has been measured in the energy range Tπ=30–60 MeV at various scattering angles. At all energies the groundstate transition could be observed, whereas the transition to the double isobaric analog state has been identified unambiguously only at Tπ=50 MeV. The groundstate transition exhibits a pronounced resonance-like en...
The reaction 7Li(π+,π−)7B has been measured at incident pion energies of 30–90 MeV. 7Li constitutes the lightest target nucleus, where the pionic charge exchange may proceed as a binary reaction to a discrete final state. Like in the Δ-resonance region the observed cross sections are much smaller than expected from the systematics found for heavier...
The (π+,π-) reaction on the isoscalar, doubly magic nuclei 16O and 40Ca has been measured in the energy range Tπ = 45–90MeV. The forward angle cross sections of the ground state transitions (GST) show a very pronounced resonancelike energy dependence. The observed energy and angle dependences are well described by the recent hypothesis of the forma...
This version is available at the following Publisher URL: http://prl.aps.org
Citations
... The hydrogen pellet target is a part of the WASA experiment [4]. It was designed to provide a hydrogen target with an effective thickness of up to 10 16 atoms/cm 2 and in addition provide space so that detectors can cover a very large solid angle around the interaction point. ...
Reference: News from CELSIUS
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... An even more exciting feature of non-analog transitions has been revealed by subsequent measurements [218,219,220,221,222,223,224] at low energies. There these transitions exhibit in general not only larger cross sections than at higher energies, but also a very pronounced narrow resonant structure in the energy dependence (Fig. 4), which we will discuss in detail in the following. ...
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... The present work fills a gap between these previous studies by measuring correlations in the 2p ground-state (g.s.) decay of the sd-shell nucleus 16 Ne where the Coulombic effects appear to be strong enough to be observable. Known experimentally for several decades [16], 16 Ne has remained poorly investigated with just a few experimental studies [17][18][19][20]. However, interest has returned recently with the decay of 16 Ne measured in relativistic neutron-knockout reactions from a 17 Ne beam [21,22]. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/278887947882506-1443503476591_Q64/Dieter-Renker.jpg)
... A number of low statistic experiments on pion productions in NN interactions have been performed in the past spanning the energy region from threshold to many GeV's by using bubble chamber techniques [3]- [4]. Recently, double-pion production in NN collisions has been accurately measured at CEL-SIUS [5,6,7], COSY [8,9], KEK [10], and PNPI-Gatchina [11] facilities. The intriguing results, obtained by the WASA collaboration [8,9,12,13,14,15,16,17,18] renewed the interest for the study of the two-pion production in NN collisions, in order to check the possible contribution of a dibaryon resonance [19,20]. ...
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... [1,2,[36][37][38] in contrast to negative measurements in Refs. [39][40][41][42] (We list only work known to us and not reviewed in Refs. [43,44]). ...
Reference: Emergence of a Brunnian neutron state
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... The entire neutron path through the detector needs to be shielded with 6 Li to reduce the background capture gamma rate to a level comparable to that from deuterons, not to limit the total count rate. In a highly segmented scintillator array such as the WASA detector [400], the count rate would be ∼500 kHz in each channel. In 6 months of beamtime on ANNI, the experiment would collect 7 × 10 15 gammas, resulting in δA = 1/P √ NG = 4 × 10 −8 given the total neutron polarisation P = 0.6 and geometry factor (cos θ coverage and detection efficiency) G = 0.5. ...
... [1,2,[36][37][38] in contrast to negative measurements in Refs. [39][40][41][42] (We list only work known to us and not reviewed in Refs. [43,44]). ...
Reference: Emergence of a Brunnian neutron state
![[object Object]](https://i1.rgstatic.net/ii/profile.image/272477200842757-1441975035244_Q64/Pierre-Andre-Amaudruz.jpg)
... And, indeed, already the first test run for measuring two-pion production close to threshold revealed a narrow, 4 MeV broad structure in the ppπ − invariant mass spectrum at 2.063 GeV, i.e. right at the position, where d (2065) was expected [307]. However, a follow-up high-statistics run revealed this structure to be partly a statistical fluctuation and partly an instrumental artifact [308]. No statistical significant (> 3σ) narrow structures have been observed, neither in the ppπ − nor in the ppπ + spectrum, see Fig. 8. ...
... Ref. [11] Ref. [28] a cc (fm) 0.12097 ( ES reactions. One dataset of AP measurements contains data of both ES reactions, namely seven π + p datapoints and three π − p ES datapoints [31]. It must be borne in mind that the DCSs of the CHAOS Collaboration [32], which are not included in the DB ± of this project, are omitted from Table 2: the two attempts to analyse these data within the context of this project a few years ago [33,34] were not satisfactory; excepting only one datapoint, the DCSs of the CHAOS Collaboration are included in the SAID πN DB. • In addition to the DCS and AP measurements, the DB 0 contains measurements of the total cross section (TCS). ...
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... This experiment was carried out as the WASA-FRS campaign together with the η' mesonic nuclei experiment. These have been conducted at the fragment separator, so-called FRS [12] with the WASA central detector [13] at GSI. The WASA (Wide Angle Shower Apparatus), which was used at COSY-Jülich, consists of a superconducting solenoid magnet and associated detectors. ...
