Geissel, H.

Rappold, C.

Saito, Takehiko

Scheidenberger, C.

GSI Repository

Experimental Setup for hypernuclear study at the Super-FRSC.Rappold∗1,2, T.R. Saito1,3,4, C. Scheidenberger1,2, and H. Geissel1,21GSI, Darmstadt, Germany; 2Justus-Liebig-Universita¨t Giessen, Germany; 3Johannes Gutenberg-Universita¨t, Mainz,Germany; 4The Helmholtz Institute Mainz, Mainz, GermanyThe first experiment of the HypHI collaboration aimedto demonstrate the feasibility of the hypernuclear spec-troscopy by means of heavy ion beam induced reactions.The final results show that the experimental method is vi-able for the study of hypernuclei [1, 2, 3].The study of exotic hypernuclei which can not be pro-duced in typical missing mass experiments involved atJPARC or JLab and MamiC is the topic of the future phasesof the project[4]. The use of rare-isotope beams is manda-tory to the study of exotic hypernuclei toward the proton-and neutron-drip line. The Super-FRS is crucial to thefuture phases of the HypHI project at FAIR, a feasibilitystudy of the Super-FRS capability toward high energy ofseveral GeV had to be achieved. A dedicated apparatus forexclusive measurement can be set up within the fragmentseparator Super-FRS, as an alternative to the experimentalapparatus devoted to inclusive measurement as it was per-formed during the first experiments of the HypHI project.A detection apparatus consisting of an additional set mag-netic optics could be install in order to separate the π− me-son of the mesonic weak decay of produced hypernuclei,while the second part of the Super-FRS is used as a frag-ment spectrometer to determine precisely the momentumof the fragment of hypernucleus of interest. Two differentstrategies have been investigated. The first strategy is touse a couple of dipole magnets in order to deflect the π−meson from the positively charged particles and fragmentswith a first dipole magnet. The induced deflection to thefragments is then compensated with the second magnet inorder to allow them to enter appropriately the second partof the Super-FRS. The second approach consists of using asolenoid magnet in order to analyze the momentum of theπ− meson while the fragments is to enter the second part ofthe Super-FRS as in the case of first approach. The detec-tion apparatus is then to be considered to allow the vertexreconstruction of the hypernuclear decay. In the first case,detectors already developed and used in the first experimentof the HypHI project such as the fiber detectors can used ina similar way to track charged particles around the decayvolume and in the upstream of the dipole magnets. π− me-son are then detected with a set of a hodoscope wall anddrift chambers already available from the first HypHI ex-periment in order to complete the information needed forthe track reconstruction. In solenoid magnet approach, adedicated detection apparatus has to be developed in or-der to perform the position and energy-loss measurements∗ c.rappold@gsi.dewithin the solenoid magnet and the solenoid end-cap.In both case, Monte Carlo simulations of the experimen-tal apparatus has been carried out in the case of the studyof the d+π− final state of the 3Λn that was reported to befound by the HypHI collaboration [3]. In those case stud-ies, dedicated detection apparatus as described above wasdesigned. The main purpose of those first Monte Carlo sim-ulations was to estimate the possible improvement that theuse of the Super-FRS as spectrometer could provide. Theinvariant mass distributions of d+π− final state of the eventreconstruction of the simulated data is shown figure 1. Onthe left panel, the invariant mass was calculated exclusivelywith the track reconstruction involving the simulated datafrom the detection apparatus, without including the Super-FRS momentum measurement of the deuteron fragment,while on the right panel, the distribution include the ex-pected momentum measurement of the deuteron with themomentum reconstruction of the π− within the detectionapparatus. An improvement on the mass resolution of afactor 4.5 is expected when the momentum resolution δp/pof deuteron is about 10−3. It demonstrates the gain of per-forming a exclusive measurement of hypernuclear matterwith the Super-FRS.Mean    2.056RMS    0.004815Constant   2639Mean      2.056Sigma     0.003598Invariant Mass (GeV)2.04 2.05 2.06 2.07 2.08 2.09Counts010002000M2RMS : 3.6 MeVMean    2.059RMS   0.000811Invariant Mass (GeV)2.055 2.06 2.065 2.07 2.075Counts0200040006000inv_massRMS : 0.8 MeV1% δp/p for π−0.1% δp/p for dFigure 1: The invariant mass distribution of simulatedd+π− final state of 3Λn, without (left panel) and with(right panel) the expected momentum measurement of thedeuteron fragment by Super-FRS as a spectrometer.References[1] C. Rappold et al., Nucl. Phys. A 913, 170 (2013).[2] C. Rappold et al., Phys. Lett. B 728, 543 (2014).[3] C. Rappold et al., Phys. Rev. C 88, 041001 (2013).[4] T.R. Saito et al., Letter Of Intent of HypHI project.GSI SCIENTIFIC REPORT 2013 NUSTAR-FRS-04doi:10.15120/GR-2014-1-NUSTAR-FRS-04 101

Experimental Setup for hypernuclear study at the Super-FRS

http://repository.gsi.de/record/67823/files/NUSTAR-FRS-04.pdf

Experimental Setup for hypernuclear study at the Super-FRS

Abstract

Similar works

Full text

Available Versions

GSI Repository