Hypernuclear production cross sections have been deduced for the first time with induced reaction of heavy ion beam on fixed target and by means of the invariant mass method by the HypHI ...Collaboration exploiting the reaction of 6Li + 12C at 2A GeV or sNN=2.70 GeV. A production cross section of 3.9±1.4 μb for 3ΛH and of 3.1±1.0 μb for 4ΛH respectively in the projectile rapidity region was inferred as well as the total production cross section of the Λ hyperon was measured and found to be equal to 1.7±0.8 mb. A global fit based on a Bayesian approach was performed in order to include and propagate statistical and systematic uncertainties. Production ratios of 3ΛH/4ΛH, 3ΛH/Λ and 4ΛH/Λ were included in the inference procedure. The strangeness population factors S3 and S4 of 3ΛH and 4ΛH respectively were extracted. In addition, the multiplicities of the Λ hyperon, 3ΛH, and 4ΛH together with the rapidity and transversal momentum density distributions of the observed hypernuclei were extracted and reported.
We report the first measurement of the average of the electron-proton and positron-proton elastic scattering cross sections. This lepton charge-averaged cross section is insensitive to the leading ...effects of hard two-photon exchange, giving more robust access to the proton's electromagnetic form factors. The cross section was extracted from data taken by the OLYMPUS experiment at DESY, in which alternating stored electron and positron beams were scattered from a windowless gaseous hydrogen target. Elastic scattering events were identified from the coincident detection of the scattered lepton and recoil proton in a large-acceptance toroidal spectrometer. The luminosity was determined from the rates of Møller, Bhabha, and elastic scattering in forward electromagnetic calorimeters. The data provide some selectivity between existing form factor global fits and will provide valuable constraints to future fits.
Design and performance of a lead fluoride detector as a luminosity monitor Pérez Benito, R.; Khaneft, D.; O'Connor, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2016, Letnik:
826, Številka:
C
Journal Article
Recenzirano
Odprti dostop
Precise luminosity measurements for the OLYMPUS two-photon exchange experiment at DESY were performed by counting scattering events with alternating beams of electrons and positrons incident on ...atomic electrons in a gaseous hydrogen target. Final products of Møller, Bhabha, and pair annihilation interactions were observed using a pair of lead fluoride Cherenkov calorimeters with custom housings and electronics, adapted from a system used by the A4 parity violation experiment at MAMI. This paper describes the design, calibration, and operation of these detectors. An explanation of the Monte Carlo methods used to simulate the physical processes involved both at the scattering vertices and in the detector apparatus is also included.
The OLYMPUS experiment Milner, R.; Hasell, D.K.; Kohl, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2014, Letnik:
741
Journal Article
Recenzirano
Odprti dostop
The OLYMPUS experiment was designed to measure the ratio between the positron–proton and electron–proton elastic scattering cross-sections, with the goal of determining the contribution of two-photon ...exchange to the elastic cross-section. Two-photon exchange might resolve the discrepancy between measurements of the proton form factor ratio, μpGEp/GMp, made using polarization techniques and those made in unpolarized experiments. OLYMPUS operated on the DORIS storage ring at DESY, alternating between 2.01GeV electron and positron beams incident on an internal hydrogen gas target. The experiment used a toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight detectors to measure rates for elastic scattering over the polar angular range of approximately 25°–75°. Symmetric Møller/Bhabha calorimeters at 1.29° and telescopes of GEM and MWPC detectors at 12° served as luminosity monitors. A total luminosity of approximately 4.5fb−1 was collected over two running periods in 2012. This paper provides details on the accelerator, target, detectors, and operation of the experiment.
The HypHI Phase 0 experiment with 6Li projectiles at 2A GeV on a carbon target has been performed at GSI in order to demonstrate the feasibility of precise hypernuclear spectroscopy with peripheral ...heavy ion collisions. Current data analyses have preliminary shown peaks in invariant mass distributions of p+π− for Λ, He3+π− for HΛ3 and He4+π− for HΛ4. Lifetime values for the corresponding peaks have been also deduced, which is in good agreement with the former known values.
Hypernuclear production cross sections have been deduced for the first time with induced reaction of heavy ion beam on fixed target and by means of the invariant mass method by the HypHI ...Collaboration exploiting the reaction of 6Li + 12C at 2A GeV or sNN=2.70 GeV. A production cross section of 3.9±1.4 μb for 3ΛH and of 3.1±1.0 μb for 4ΛH respectively in the projectile rapidity region was inferred as well as the total production cross section of the Λ hyperon was measured and found to be equal to 1.7±0.8 mb. A global fit based on a Bayesian approach was performed in order to include and propagate statistical and systematic uncertainties. Production ratios of 3ΛH/4ΛH, 3ΛH/Λ and 4ΛH/Λ were included in the inference procedure. The strangeness population factors S3 and S4 of 3ΛH and 4ΛH respectively were extracted. In addition, the multiplicities of the Λ hyperon, 3ΛH, and 4ΛH together with the rapidity and transversal momentum density distributions of the observed hypernuclei were extracted and reported.
A novel experiment, aiming at demonstrating the feasibility of hypernuclear spectroscopy with heavy ion beams, was conducted. Using the invariant mass method, the spectroscopy of hypernuclear ...products of 6Li projectiles on a carbon target at 2A GeV was performed. Signals of the Λ-hyperon and HΛ3 and HΛ4 hypernuclei were observed for final states of p+π−, He3+π− and He4+π−, respectively, with significance values of 6.7, 4.7 and 4.9σ. By analyzing the proper decay time from secondary vertex distribution with the unbinned maximum likelihood fitting method, their lifetime values were deduced to be 262−43+56±45 ps for Λ, 183−32+42±37 ps for HΛ3, and 140−33+48±35 ps for HΛ4.
A novel experiment, aiming at demonstrating the feasibility of hypernuclear spectroscopy with heavy-ion beams, was conducted. Using the invariant mass method, the spectroscopy of hypernuclear ...products of 6Li projectiles on a carbon target at 2 AGeV was performed. Signals of the \Lambda-hyperon and 3\Lambda H and 4\Lambda H hypernuclei were observed for final states of p+\pi^-, 3He+\pi^- and 4He+\pi^-, respectively, with significance values of 6.7, 4.7 and 4.9\sigma. By analyzing the proper decay time from secondary vertex distribution with the unbinned maximum likelihood fitting method, their lifetime values were deduced to be $262 ^{+56}_{-43} \pm 45$ ps for \Lambda, $183 ^{+42}_{-32} \pm 37$ ps for 3\Lambda H, and $140 ^{+48}_{-33}\pm 35 $ ps for 4\Lambda H.
The HypHI Phase 0 experiment Saito, T.R.; Bianchin, S.; Borodina, O. ...
Nuclear physics. A,
04/2010, Letnik:
835, Številka:
1
Journal Article
Recenzirano
The HypHI Phase 0 experiment to demonstrate the feasibility of precise hypernuclear spectroscopy with induced reactions of heavy ion beams was performed at GSI in August and October in 2009, with a ...projectile of
6Li at 2
A GeV impinged on carbon graphite target with a thickness of 8 g/cm
2. The experiment mainly aims to reconstruct events of
3
ΛH,
4
ΛH and
5
ΛHe by observing the
π
−
decay channel. Details of the HypHI Phase 0 experiment performed in August in 2009 will be discussed.
PDF
