| 1. |
- Adlarson, Patrik, et al.
(författare)
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Charge symmetry breaking in dd -> He-4 pi(0) with WASA-at-COSY
- 2014
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 739, s. 44-49
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Tidskriftsartikel (refereegranskat)abstract
- Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd -> He-4 pi(0) have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of p(d) = 1.2GeV/c using the WASA-at-COSY facility. The total cross section amounts to sigma(tot) =(118 +/- 18(stat) +/- 13(sys) +/- 8(ext)) p band first data on the differential cross section are consistent with s-wave pion production.
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| 2. |
- Adlarson, Patrik, et al.
(författare)
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Cross section ratio and angular distributions of the reaction p + d -> He-3 + eta at 48.8MeV and 59.8MeV excess energy
- 2014
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 50:6, s. 100-
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Tidskriftsartikel (refereegranskat)abstract
- We present new data for angular distributions and on the cross section ratio of the p+d -> He-3+eta reaction at excess energies of Q - 48.8MeV and Q - 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum Julich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.
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| 3. |
- Adlarson, Patrik, et al.
(författare)
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Evidence for a New Resonance from Polarized Neutron-Proton Scattering
- 2014
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:20, s. 202301-
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Tidskriftsartikel (refereegranskat)abstract
- Exclusive and kinematically complete high-statistics measurements of quasifree polarized (n) over right arrowp scattering have been performed in the energy region of the narrow resonancelike structure d* with I(J(P)) = 0(3(+)),M approximate to 2380 MeV, and Gamma approximate to 70 MeV observed recently in the double-pionic fusion channels pn -> d pi(0)pi(0) and pn -> d pi(+)pi(-). The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process (d) over right arrowp -> np + p(spectator). This allowed the np analyzing power, A(y), to be measured over a broad angular range. The obtained A(y) angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new A(y) data into the SAID analysis produces a pole in the D-3(3) - (3)G(3) waves in support of the d* resonance hypothesis.
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| 4. |
- Adlarson, Patrik, et al.
(författare)
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Measurement of the eta -> pi(+)pi(-)pi(0) Dalitz plot distribution
- 2014
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 90:4, s. 045207-
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Tidskriftsartikel (refereegranskat)abstract
- The Dalitz plot distribution of the eta -> pi(+)pi(-)pi(0) decay is determined by using a data sample of 1.2 x 10(7) eta mesons from the pd -> He-3 eta reaction at 1 GeV collected by the WASA detector at COSY.
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| 5. |
- Adlarson, Patrik, et al.
(författare)
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Neutron-proton scattering in the context of the d*(2380) resonance
- 2014
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 90:3, s. 035204-
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Tidskriftsartikel (refereegranskat)abstract
- New data on quasifree polarized neutron-proton scattering in the region of the recently observed d* resonance structure are obtained by exclusive and kinematically complete high-statistics measurements with WASA at COSY. This paper details the determination of the beam polarization, checks of the quasifree character of the scattering process, on all obtained Ay angular distributions and on the new partial-wave analysis, which includes the new data producing a resonance pole in D-3(3)-(3)G(3) coupled partial waves at (2380 +/- 10 - i40 +/- 5) MeV-in accordance with the d* dibaryon resonance hypothesis. The effect of the new partial-wave solution on the description of total and differential cross-section data as well as specific combinations of spin-correlation and spin-transfer observables available from COSY-ANKE measurements at T-d = 2.27 GeV is discussed.
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| 6. |
- Pyszniak, Andrzej, et al.
(författare)
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A pellet tracking system for the PANDA experiment
- 2014
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 229:1-3, s. 159-163
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Tidskriftsartikel (refereegranskat)abstract
- Frozen microspheres of hydrogen (pellets) will be one of the target types for the future hadron physics experiment PANDA at FAIR (GSI, Darmstadt, Germany) [1]. Pellets with a diameter of 25- mum are generated about 3 meters above the interaction region, to which they travel with a velocity around 80 m/s inside a narrow pipe. The interaction region is defined by the overlap of the pellet stream and the accelerator beam and has a size of a few millimeters. One would like to know the interaction point more precisely, to have better possibilities to reconstruct particle tracks and events e.g. in charmonium decay studies. One would also like to suppress background events that do not originate in a pellet, but e.g. may occur in rest gas, that is present in the beam pipe. A solution is provided by the presented pellet tracking system together with a target operation mode that provides one and only one pellet in the interaction region most of the time. The goal is to track individual pellets in order to know their position with a resolution of a few tenths of a millimeter at the time of an interaction. The system must also be highly efficient and provide tracking information for essentially all pellets that pass the interaction region. Presented results from the design studies show that the goals can be fulfilled by this solution.
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| 7. |
- Pyszniak, Andrzej, 1986-
(författare)
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Development and Applications of Tracking of Pellet Streams
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of a system for optical tracking of frozen hydrogen microsphere targets (pellets) was done. It is intended for the upcoming hadron physics experiment PANDA at FAIR, Darmstadt, Germany. Knowledge of the interaction position, obtained with this system, will improve background rejection, precision of particle track reconstruction and will also help distinguish between primary and secondary vertices. Investigations of pellet detection conditions and pellet stream parameters were performed at Uppsala Pellet Test Station located at The Svedberg Laboratory. Various illumination and detection conditions were checked and optimized. The gained knowledge has been used to develop Monte Carlo procedures simulating experiments with pellets. Then simulations of pellet tracking were carried out including the constraints from the PANDA setup. The performance of the tracking was checked for various pellet stream and pellet detection conditions. Two procedures of pellet track reconstruction were developed – a fast procedure and a high efficiency procedure. The studies were done for one tracking section (just below pellet generator) and for two sections (the second just above pellet dump) and showed that the resolution of the tracking system can be better than 100 μm (sigma) in each direction and that the interaction point will be reconstructed for 70-95% of hadronic events, for suitable pellet stream and detection conditions. Usage of pellet tracking information in the hadronic data analysis was discussed, concerning the data taking, particle track reconstruction together with the PANDA micro vertex detector, hadronic event classification and treatment of the various classes. Test measurements with the WASA setup at FZJ, Jülich, Germany were done to check how the information about the number of pellets in the accelerator beam region can be used in the hadronic data analysis. Instantaneous rates of WASA "elastic" triggers were used for classification of hadronic events as coming from pellets or from a background. The study clearly showed that one can distinguish between the two event classes. The study gave experience in using two different systems synchronized with each other – the experiment's DAQ and another system that works with a much longer time scale – similar to the pellet tracking system.
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| 8. |
- Pyszniak, Andrzej, et al.
(författare)
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Studies on implementation of pellet tracking in hadron physics experiments
- 2014
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Ingår i: Meson 2014 - 13th International Workshop on Production, Properties and Interaction of Mesons. - : EDP Sciences.
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Konferensbidrag (refereegranskat)abstract
- A system for optical tracking of frozen hydrogen microsphere targets (pellets) has been designed. It is intended for the upcoming hadron physics experiment PANDA at FAIR, Darmstadt, Germany. With such a tracking system one can reconstruct the positions of the individual pellets at the time of a hadronic interaction in the offline event analysis. This gives information on the position of the primary interaction vertex with an accuracy of a few 100 mu m, which is very useful e.g. for reconstruction of charged particle tracks and secondary vertices and for background suppression. A study has been done at the WASA detector setup (Forschungszentrum Julich, Germany) to check the possibility of classification of hadronic events as originating in pellets or in background. The study has been done based on the instantaneous rate a Long Range TDC which was used to determine if a pellet was present in the accelerator beam region. It was clearly shown that it is possible to distinguish the two event classes. Also, an experience was gained with operation of two synchronized systems operating in different time scales, as it will also be the case with the optical pellet tracking.
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