Design and construction of the SAPHIR detector

doi:10.1016/0168-9002(94)90868-0

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Volume 344, Issue 3, 15 May 1994, Pages 470-486

https://doi.org/10.1016/0168-9002(94)90868-0 Get rights and content

Abstract

The design, construction, and performance of the large solid angle magnetic spectrometer SAPHIR is described. It was built for the investigation of photon-induced reactions on nucleons and light nuclei with multi-particle final states up to photon energies of 3.1 GeV. The detector is equipped with a tagged photon beam facility and is operated at the stretcher ring ELSA in Bonn.

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Cited by (38)

Light Baryon Spectroscopy
2022, Progress in Particle and Nuclear Physics
Citation Excerpt :
Two different experimental halls are currently in use, which allow experiments with polarized or unpolarized electron beams. The large solid angle magnetic spectrometer SAPHIR (Spectrometer Arrangement for PHoton Induced Reactions) [129] was built up at the ELSA accelerator in Bonn and took data between 1993 and 1998. Its setup featured a large magnet with several drift chambers inside.
This review treats the advances in Light Baryon Spectroscopy of the last two decades, which were mainly obtained by measuring meson-production reactions at photon facilities all over the world. We provide a consistent compendium of experimental results, as well as a review of the theoretical methods of amplitude analysis used to analyze the data. The most significant datasets are presented in detail and are listed in combination with a full set of the relevant references. In addition, a brief summary of spin-formalisms, which are ubiquitous in Light Baryon Spectroscopy, as well as a review on complete experiments, are provided. The synthesis of the reviewed knowledge is presented in a full interpretation of the new results on the Light Baryon Spectrum.
Photoproduction reactions and non-strange baryon spectroscopy
2020, Progress in Particle and Nuclear Physics
We review the last two decades of using photon beams to measure the production of mesons, and in particular the information that can be obtained on the spectrum of light, non-strange baryons. This is a compendium of experimental results, which should be used as a complement to theoretical reviews of the subject. Lists of data sets are given, together with a comprehensive set of references. An indication of the impact of the data is presented with a summary of the results.
Recent results from ELSA
2005, Progress in Particle and Nuclear Physics
Citation Excerpt :
The successful completion of the GDH-experiment with polarized proton and deuteron targets, both at MAMI and ELSA, demonstrated the feasibility of performing long runs of such double polarization experiments [1]. The SAPHIR detector [2], shown schematically in Fig. 2, is a multi-purpose magnetic spectrometer with a large angular acceptance consisting of drift chambers and scintillator walls for triggering and time-of-flight measurements. Photons are produced via bremsstrahlung in a copper foil target.
One of the foremost challenges in hadron physics is to obtain an understanding of the structure of baryons. The main features of the baryon mass spectrum at low excitation energies are reasonably known and described quite accurately by models, but the high-mass spectrum is still rather obscure. With modern achievements in accelerators, highly polarized nucleon targets and hermetically closed detectors allowing for charged and neutral particle detection high-lying excitations can be investigated through the systematic study of single and multiple meson production. In this contribution the instrumentation and results of experiments from the ELSA accelerator at Bonn as well as their significance for baryon resonance analyses are described. In particular, data on photoproduction of vector and pseudoscalar mesons of different flavors are presented.
Kaon photoproduction at SAPHIR for photon energies up to 2.6 GeV
2005, Nuclear Physics A
The measurement of photoproduction reactions with open strangeness is one of the central issues of the physics program at SAPHIR. We report here on the analysis of the reactions $γ p \to K^{+} Σ^{0}$ and $γ p \to K^{0} Σ^{+}$ in the photon energy range between threshold and 2.6 GeV using data taken in the years 1997–1998. The measured cross sections suggest contributions from resonance production for both reactions. Coupled channel analysis of the two mentioned isospin channels together with the reaction $γ p \to K^{+} Λ$ also measured by SAPHIR, should help to extract resonance informations in these reactions. Upcoming data from different experiments on the photoproduction of kaon–hyperon pairs on the neutron and electroproduction of strangeness, including cross sections and polarization observables, will even improve this situation. However, for an initial discussion of what one could learn from strangeness production in the future final data for the reaction $γ p \to K^{+} Σ^{0}$ the preliminary SAPHIR results for the reaction $γ p \to K^{0} Σ^{+}$ are compared here with an isobar model designed for the previous SAPHIR data. The latter had less energy and a smaller kaon production angle resolution than new SAPHIR data and delivered data for $γ p \to K^{+} Λ$ and $γ p \to K^{+} Σ^{0}$ only up to 2.0 GeV and for $γ p \to K^{0} Σ^{+}$ up to 1.55 GeV. The new data show clearly that such a model must be refined to describe the new SAPHIR data, because these data are more sensitive to background and resonance contributions.
Drift chamber with a c-shaped frame
2005, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
We present the construction of a planar drift chamber with wires stretched between two arms of a c-shaped aluminum frame. The special shape of the frame allows to extend the momentum acceptance of the COSY-11 detection system towards lower momenta without suppressing the high-momentum particles. The proposed design allows for construction of tracking detectors covering small angles with respect to the beam, which can be installed and removed without dismounting the beam-pipe. For a three-dimensional track reconstruction a computer code was developed using a simple algorithm of hit pre-selection.
Evidence for the positive-strangeness pentaquark θ<sup>+</sup> in photoproduction with the SAPHIR detector at ELSA
2003, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
The positive-strangeness baryon resonance Θ⁺ is observed in photoproduction of the nK⁺K⁰_s final state with the SAPHIR detector at the Bonn ELectron Stretcher Accelerator ELSA. It is seen as a peak in the nK⁺ invariant mass distribution with a 4.8σ confidence level. We find a mass M_Θ⁺=1540±4±2 MeV and an upper limit of the width Γ_Θ⁺<25 MeV at 90% c.l. The photoproduction cross section for $K^{0} Θ^{+}$ is in the order of 300 nb. From the absence of a signal in the pK⁺ invariant mass distribution in γp→pK⁺K⁻ at the expected strength we conclude that the Θ⁺ must be isoscalar.

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^☆: This work is supported by the Bundesminister für Forschung und Technologie (BMFT) under contract number 06 BN 621 I.

¹: No longer working for the SAPHIR project.

^∗: Corresponding author, address: Physikalisches Institut der Univ. Bonn, Nusallee 12, D-53115 Bonn, Germany.

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Design and construction of the SAPHIR detector☆

Abstract

BONN-HE-87-19

ein neuer Beschleuniger der Mittelenergiephysik

BONN-IR-87-30

Phys. Bl.

BONN-IR-89-31

BONN-IR-92-46

BONN-IR-91-17

BONN-IR-91-59

BONN-IR-93-15

BONN-IR-91-27

BONN-IR-87-36

BONN-IR-92-02

BONN-IR-84-01

BONN-IR-84-02

BONN-IR-92-47

BONN-IR-89-31

BONN-IR-85-13

BONN-IR-93-06

BONN-IR-93-55