175 research outputs found
Collision damping in the pi 3He -> d'N reaction near the threshold
We present a simple quantum mechanical model exploiting the optical potential
approach for the description of collision damping in the reaction pi 3He -> d'N
near the threshold, which recently has been measured at TRIUMF. The influence
of the open d'N -> NNN channel is taken into account. It leads to a suppression
factor of about ten in the d' survival probability. Applications of the method
to other reactions are outlined.Comment: RevTeX4, 14 pages, 3 Postscript figures, uses epsfig.sty, to appear
in Phys.Rev.
The barrel DIRC of PANDA
Cooled antiproton beams of unprecedented intensities in the momentum range of 1.5-15 GeV/c will be used for the PANDA experiment at FAIR to perform high precision experiments in the charmed quark sector. The PANDA detector will investigate antiproton annihilations with beams in the momentum range of 1.5 GeV/c to 15 GeV/c on a fixed target. An almost 4π acceptance double spectrometer is divided in a forward spectrometer and a target spectrometer. The charged particle identification in the latter is performed by ring imaging Cherenkov counters employing the DIRC principle
Status of the PANDA barrel DIRC
The PANDA experiment at the future Facility for Antiproton and Ion Research in Europe GmbH (FAIR) at GSI, Darmstadt will study fundamental questions of hadron physics and QCD using high-intensity cooled antiproton beams with momenta between 1.5 and 15 GeV/c. Hadronic PID in the barrel region of the PANDA detector will be provided by a DIRC (Detection of Internally Reflected Cherenkov light) counter. The design is based on the successful BABAR DIRC with several key improvements, such as fast photon timing and a compact imaging region. Detailed Monte Carlo simulation studies were performed for DIRC designs based on narrow bars or wide plates with a variety of focusing solutions. The performance of each design was characterized in terms of photon yield and single photon Cherenkov angle resolution and a maximum likelihood approach was used to determine the π/K separation. Selected design options were implemented in prototypes and tested with hadronic particle beams at GSI and CERN. This article describes the status of the design and R&D for the PANDA Barrel DIRC detector, with a focus on the performance of different DIRC designs in simulation and particle beams
The barrel DIRC of PANDA
Cooled antiproton beams of unprecedented intensities in the momentum range of 1.5-15 GeV/c will be used for the PANDA experiment at FAIR to perform high precision experiments in the charmed quark sector. The PANDA detector will investigate antiproton annihilations with beams in the momentum range of 1.5 GeV/c to 15 GeV/c on a fixed target. An almost 4π acceptance double spectrometer is divided in a forward spectrometer and a target spectrometer. The charged particle identification in the latter is performed by ring imaging Cherenkov counters employing the DIRC principle
Photoproduction of eta-mesic 3He
The photoproduction of eta-mesic 3He has been investigated using the TAPS
calorimeter at the Mainz Microtron accelerator facility MAMI. The total
inclusive cross section for the reaction gamma+3He->eta+X has been measured for
photon energies from threshold to 820 MeV. The total and angular differential
coherent eta cross sections have been extracted up to energies of 745 MeV. A
resonance-like structure just above the eta production threshold with an
isotropic angular distribution suggests the existence of a resonant quasi-bound
state. This is supported by studies of a competing decay channel of such a
quasi-bound eta-mesic nucleus into pi^0+p+X. A binding energy of (-4.4+-4.2)
MeV and a width of (25.6+-6.1) MeV is deduced for the quasi-bound eta-mesic
state in 3He.Comment: v1: 4 pages, 4 figures, submitted to PRL; v2: minor revisions and
corrections, new figure added, 4 pages, 5 figs; v3: minor change
The TORCH time-of-flight detector
AbstractThe TORCH time-of-flight detector is being developed to provide particle identification between 2 and 10GeV/c momentum over a flight distance of 10m. TORCH is designed for large-area coverage, up to 30m2, and has a DIRC-like construction. The goal is to achieve a 15ps time-of-flight resolution per incident particle by combining arrival times from multiple Cherenkov photons produced within quartz radiator plates of 10mm thickness. A four-year R&D programme is underway with an industrial partner (Photek, UK) to produce 53×53mm2 Micro-Channel Plate (MCP) detectors for the TORCH application. The MCP-PMT will provide a timing accuracy of 40ps per photon and it will have a lifetime of up to at least 5Ccm−2 of integrated anode charge by utilizing an Atomic Layer Deposition (ALD) coating. The MCP will be read out using charge division with customised electronics incorporating the NINO chipset. Laboratory results on prototype MCPs are presented. The construction of a prototype TORCH module and its simulated performance are also described
The barrel DIRC of PANDA
Cooled antiproton beams of unprecedented intensities in the momentum range of 1.5-15 GeV/c will be used for the PANDA experiment at FAIR to perform high precision experiments in the charmed quark sector. The PANDA detector will investigate antiproton annihilations with beams in the momentum range of 1.5 GeV/c to 15 GeV/c on a fixed target. An almost 4π acceptance double spectrometer is divided in a forward spectrometer and a target spectrometer. The charged particle identification in the latter is performed by ring imaging Cherenkov counters employing the DIRC principle
Search for Narrow NNpi Resonances in Exclusive p p -> p p pi+ pi- Measurements
Narrow structures in the range of a few MeV have been searched for in p p pi+
and p p pi- invariant mass spectra obtained from exclusive measurements of the
p p -> p p pi+ pi- reaction at Tp = 725, 750 and 775 MeV using the PROMICE/WASA
detector at CELSIUS. The selected reaction is particularily well suited for the
search for NN and / or N Delta decoupled dibaryon resonances. Except for a
possible fluctuation at 2087 MeV/c^2 in Mpppi- no narrow structures could be
identified neither in Mpppi+ nor in Mpppi- on the 3 sigma level of statistical
significance, giving an upper limit (95% C.L.) for dibaryon production in this
reaction of sigma < 20 nb for 2020 MeV/c^2 < m(dibaryon) < 2085 MeV/c^2Comment: 3 pages, 4 figure
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 over the energy region of the so-called ABC
effect, a pronounced low-mass enhancement in the -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 in both and systems.
Necessary further tests of the resonance interpretation are discussed
Charge Symmetry Breaking in dd->4He{\pi}0 with WASA-at-COSY
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->4He{\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=1.2 GeV/c using the WASA-at-COSY
facility. The total cross section amounts to sigma(tot) = (118 +- 18(stat) +-
13(sys) +- 8(ext)) pb and first data on the differential cross section are
consistent with s-wave pion production.Comment: 14 pages, 5 figure
- …