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•A new versatile probability distribution function called “hyper-EMG” is presented.•Modeling of asymmetric MR-TOF mass spectra using the hyper-EMG is demonstrated.•Peak shape is ...precisely modeled over 5 orders of magnitude in abundance.•Hyper-EMG outperforms the common peak shape models in case of overlapping peaks.•Improved mass and abundance values are obtained for overlapping peaks in MR-TOF-MS.
A new probability distribution function (PDF) called hyper-Exponentially Modified Gaussian (hyper-EMG) is introduced for the analysis of high-resolution spectra from multiple-reflection time-of-flight mass spectrometers. The hyper-EMG consists of a central Gaussian distribution modified by multiple exponential tails with different strengths at one or both sides. The basic statistical properties of the new PDF are given and the analysis of mass spectra containing separated and overlapping peaks is presented. The main requirement is to accurately determine the positions and areas of the individual mass peaks. From the distances of positions the mass values can be determined, from the areas the population of different ground and isomeric states can be obtained. The hyper-EMG has been applied to high-resolution time and mass spectra characterized by mass resolving powers of 140,000 and 520,000 obtained with Cs+133 and K+39 ions, respectively. From the measured mass distribution of K+39 ions, an overlapping distribution of two peaks with an area ratio of 1:10 and a mass difference of 2.6ppm (parts-per-million) is generated and analyzed. The results reveal significant advantages of the new PDF for the evaluation of overlapping distributions for accurate mass and area determinations compared with commonly used PDFs which are more than one order of magnitude less accurate. It is obvious that the hyper-EMG can be favorably applied also to other fields.
Pseudo-ductility could be sought in composite structures to avoid their brittle behaviour and, consequently, to withstand higher levels of external loading due to an extended non-linear response. ...This mechanism has been deeply examined in the literature for angle-ply laminates submitted to uniaxial tests. Nonetheless, the pseudo-ductile effects could appear also under flexural loading because tension and compression are applied in different regions of the cross-sections simultaneously. In this sense, bending testing presents a higher degree of complexity introduced by the variation of the strain through the cross-section thickness. Taking this into account the main scope of this work is to understand, describe, predict and optimise the pseudo-ductile flexural response of symmetric ±45° angle-ply laminates consisting of unidirectional and continuous CFRP plies. The outcome of three-point bending tests is reviewed analytically and experimentally. The analytical study considers the different behaviour of the material under tension and compression as well as the neutral fibre deviation from the mid-height plane. During testing the full normal strain field is acquired by means of a DIC system while strain-rosettes help to complete the data. The post-process based on microscopic characterization using SEM technology allows to observe the procedure of damage initiation and its evolution. Finally, the determination of the stacking sequences that minimise the bending-twisting coupling but favour the pseudo-ductile response is developed applying optimisation techniques with design purposes.
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.
At the Mainz Microtron hypernuclei are produced by (e,e′K) reactions. A dedicated kaon spectrometer located at 0° with respect to the electron beam is used to detect kaons emitted in forward ...direction thus tagging events involving strangeness production. By measuring the momenta of pions from two body weak decays using high resolution magnetic spectrometers one gains direct access to the ground state masses of the produced hyperfragments. At FAIR the PANDA Collaboration intends to produce double-hypernuclei by numbers with an antiproton beam and study their high resolution γ-spectroscopy thus providing for the first time precise information on the level structure of these nuclei. The status of both experiments is reviewed.
A statistical combination of the experimental lifetime estimations available in the literatures is performed for 3ΛH and 4ΛH, including several recent measurements. The combined average values of the ...lifetime for 3ΛH and 4ΛH are respectively 216−16+19 ps and 192−18+20 ps with a reduced χ2 of 0.89 and 0.48. A new insight into the lifetime estimation of the HypHI Phase 0 experiment by a Bayesian approach is also presented. In this approach, several different prior distributions including the combination of previous lifetime data and a Jeffrey prior are used. The principal mode and the smallest credible interval at 68% of the posterior distribution, given by the prior belief of the previous measurements, are 217−16+19 ps and 194−18+20 ps respectively for 3ΛH and 4ΛH. The two employed approaches have revealed that the lifetime of hypernuclei 3ΛH and 4ΛH can be shorter than the Λ–hyperon lifetime.
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.
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Beam helicity asymmetries in the
e
→
p
→
e
K
+
Λ
reaction have been measured at unprecedentedly low four-momentum transfers
〈
Q
2
〉
=
0
.
05
(
GeV
/
c
)
2
. At the Mainz Microtron (MAMI), the ...experiment was performed with a longitudinally polarized beam and an out-of-plane detection of the scattered electron. This experiment probed the associated helicity-dependent structure function
d
σ
L
T
/
d
Ω
K
c
.
m
.
, which is sensitive to the details of resonances of the proton. The results were compared to models for kaon electroproduction using effective Lagrangians. The MAMI data is not supporting the Kaon-Maid isobar model, which uses strong longitudinal couplings of the virtual photon to nucleon resonances and predicts a strong peaking of the structure function at forward angles and low
Q
2
. The data is also in disagreement with a Regge-plus-resonance model that predicts the incorrect sign of the structure function. The combination of the MAMI results wih data taken at higher four-momentum transfers measured at Jefferson Lab indicates a smooth transition in
Q
2
without significant changes of the interference pattern in the electroproduction process.
Present and future research into the electroproduction of strangeness plays an important role at Mainz Microtron MAMI. With the Kaos spectrometer for kaon detection operated in the multi-spectrometer ...facility first cross section measurements of the exclusive p(e,e′K+)Λ,Σ0 reactions at low-momentum transfers have been performed. These measurements have clearly discriminated between effective Lagrangian models for photo- and electroproduction of strangeness. Recently, the Kaos spectrometer was upgraded to a double-arm spectrometer for the measurement of elementary cross sections at very forward scattering angles and for the missing mass spectroscopy of hypernuclear states. In parallel, pioneering experiments on decay-pion spectroscopy of electroproduced hypernuclei were carried out at MAMI. Future experiments will on the one side address the cross section of the elementary process with polarized beam and on the other side continue the hypernuclear spectroscopy with different light nuclear targets.
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