New precise results of a measurement of the elastic electron-proton scattering cross section performed at the Mainz Microtron MAMI are presented. About 1400 cross sections were measured with negative ...four-momentum transfers squared up to Q² = 1 (GeV/c)² with statistical errors below 0.2%. The electric and magnetic form factors of the proton were extracted by fits of a large variety of form factor models directly to the cross sections. The form factors show some features at the scale of the pion cloud. The charge and magnetic radii are determined to be <r²E>½ = 0.879(5)stat(4)syst(2)model(4)group fm and <r²M>½ = 0.777(13)stat(9)syst(5)model(2)group fm.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The mechanism for the formation of the
Λ
(
1405
)
resonance is studied in a chiral quark model that includes quark-meson as well as contact (four point) interactions. The negative-parity
S
-wave ...scattering amplitudes for strangeness
-
1
and 1 are calculated within a unified coupled-channel framework that includes the
KN
,
K
¯
N
,
π
Σ
,
η
Λ
,
K
Ξ
,
π
Λ
, and
η
Σ
channels and possible genuine three-quark bare singlet and octet states corresponding to
1
2
-
resonances. It is found that in order to reproduce the scattering amplitudes in the
S
01
partial wave it is important to include the pertinent three-quark octet states as well as the singlet state, while the inclusion of the contact term is not mandatory. The Laurent-Pietarinen expansion is used to determine the
S
-matrix poles. Following their evolution as a function of increasing interaction strength, the mass of the singlet state is strongly reduced due to the attractive self-energy in the
π
Σ
and
K
¯
N
channels; when it drops below the
KN
threshold, the state acquires a dominant
K
¯
N
component which can be identified with a molecular state. The attraction between the kaon and the nucleon is generated through the
K
¯
N
Λ
∗
interaction rather than by meson-nucleon forces.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A massive, but light, Abelian U(1) gauge boson is a well-motivated possible signature of physics beyond the standard model of particle physics. In this Letter, the search for the signal of such a ...U(1) gauge boson in electron-positron pair production at the spectrometer setup of the A1 Collaboration at the Mainz Microtron is described. Exclusion limits in the mass range of 40 MeV/c^{2} to 300 MeV/c^{2}, with a sensitivity in the squared mixing parameter of as little as ε^{2}=8×10^{-7} are presented. A large fraction of the parameter space has been excluded where the discrepancy of the measured anomalous magnetic moment of the muon with theory might be explained by an additional U(1) gauge boson.
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We perform a systematic study of the α-particle excitation from its ground state 0_{1}^{+} to the 0_{2}^{+} resonance. The so-called monopole transition form factor is investigated via an electron ...scattering experiment in a broad Q^{2} range (from 0.5 to 5.0 fm^{-2}). The precision of the new data dramatically supersedes that of older sets of data, each covering only a portion of the Q^{2} range. The new data allow the determination of two coefficients in a low-momentum expansion, leading to a new puzzle. By confronting experiment to state-of-the-art theoretical calculations, we observe that modern nuclear forces, including those derived within chiral effective field theory that are well tested on a variety of observables, fail to reproduce the excitation of the α particle.
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We report on a comprehensive reinterpretation of the existing cross-section data for elastic electron-proton scattering obtained by the initial-state radiation technique, resulting in a significantly ...improved accuracy of the extracted proton charge radius. By refining the external energy corrections we have achieved an outstanding description of the radiative tail, essential for a detailed investigation of the proton finite-size effects on the measured cross sections. This development, together with a novel framework for determining the radius, based on a regression analysis of the cross sections employing a polynomial model for the form factor, led us to a new value for the charge radius, which is
(
0.878
±
0
.
011
stat
.
±
0
.
031
sys
.
±
0
.
002
mod
.
)
fm
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A highly segmented neutron polarimeter for A1 Spreckels, R.; Hoek, M.; Müller, U. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2024, Volume:
1062
Journal Article
Peer reviewed
Open access
A new neutron polarimeter for measuring the neutron’s electric form factor was designed and constructed to complement the A1 spectrometer setup at the Mainz Microtron (MAMI). The design is based on a ...previous polarimeter with significant improvements to halve the error of the extracted form factor. A higher granularity of the polarimeter sections and a deeper first section on the one hand, and a faster readout employing Time-over-Threshold methods to measure the signal amplitudes combined with a high-precision FPGA-based TDC on the other hand will allow to achieve this goal. The performance of the new polarimeter during a first measurement campaign in 2019 using liquid hydrogen and deuterium targets will be discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The meson scattering and electroproduction amplitudes in the
D
13 ,
D
33 and
D
15 partial waves are calculated in a coupled-channel formalism incorporating quasi-bound quark-model states, extending ...our previous studies of the
P
11 ,
P
33 and
S
11 partial waves. The vertices of the baryon-meson interaction including the
s
- and
d
-wave pions and
-mesons, the
s
-wave
-meson, and the
s
- and
p
-wave
-mesons are determined in the Cloudy Bag Model, with some changes of the parameters to reproduce the widths of the resonances. The helicity amplitudes and the electroproduction amplitudes exhibit consistent behavior in all channels but tend to be too weak compared to the experiment. We discuss possible origins of this discrepancy which arises also in the constituent quark model calculations.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A cryogenic supersonic gas jet target was developed for the MAGIX experiment at the high-intensity electron accelerator MESA. It will be operated as an internal, windowless target in the ...energy-recovering recirculation arc of the accelerator with different target gases, e.g., hydrogen, deuterium, helium, oxygen, argon, or xenon. Detailed studies have been carried out at the existing A1 multi-spectrometer facility at the electron accelerator MAMI. This paper focuses on the developed handling procedures and diagnostic tools, and on the performance of the gas jet target under beam conditions. Considering the special features of this type of target, it proves to be well suited for a new generation of high-precision electron scattering experiments at high-intensity electron accelerators.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The root-knot nematode Meloidogyne ethiopica Whitehead, mainly reported from African countries, was first described in 1968 in Tanzania (4). It was further detected in South America (Brazil, Chile, ...and Peru) (2). In 2004, M. ethiopica was recorded for the first time in Europe on tomato (3) and later in field soil samples from maize (Zea mays L.) and kiwi Actinidia deliciosa (A. Chev.) C. F. Liang & A. R. Ferguson collected in the area of Kavalla in North Greece (1). M. ethiopica was included on the EPPO alert list of harmful organisms in 2011. In summer 2009, severe stunting, leaf wilting, and extensive root galling of a presumed root-knot nematode (Meloidogyne sp.) were detected during a routine survey for root nematodes attacking tomato (Solanum lycopersicum L.) crops from two greenhouses in the campus of University of Ondokuz Mayis and attacking cucumber (Cucumis sativus L.) crops from commercial greenhouses in Çarsamba district of Samsun Province, Turkey. Perineal patterns of Meloidogyne sp. females collected from infested roots were variable, with moderately high to high dorsal arch, lateral line mostly indistinct and striae usually wavy, which is very similar to that seen in M. incognita Kofoid & White. Such variability among perineal patterns precluded its accurate identification. For further species identification, protein extracted from young egg-laying females were resolved in 3% stacking (pH 6.8) and 7% separating (pH 8.8) polyacrylamide gel with Tris-glycine buffer. The gels were stained with α-naphthyl acetate substrate for esterase activity (1). The esterase phenotypes exhibited a three banded pattern, E3, that was identical to M. ethiopica. Therefore, esterase studies were repeated including nematodes from M. ethiopica culture from Slovenia used as a reference. In addition, small subunit rDNA sequence analyses were performed to complete species identification. DNA sequences of a 1.6-kb rDNA fragment were generated using two sets of primers (1) and deposited in the NCBI GenBank with the accession number KC551945. The sequence was compared to the corresponding fragments of M. ethiopica and closely related species from the NCBI GenBank. DNA sequence of M. ethiopica from Turkey exhibited the highest identity of 99.8% to the sequence FJ559408 of M. ethiopica from Slovenia. Sequences KC551945, FJ559408, AY942630, and JQ768373 of M. ethiopica from Turkey, Slovenia, Brazil, and Greece, respectively, clustered together and formed a separate clade using phylogenetic analyses. This species may pose a threat for vegetable production in Turkey since it has a wide host range infesting numerous higher plants including monocotyledons, dicotyledons, herbaceous, and woody plants. Furthermore, M. ethiopica may have been present in Turkey for many years because correct identification based only on perineal pattern is difficult. Thus, misidentification might have been possible. The distribution of this nematode in more extensive vegetable fields should be determined. To our knowledge, this is the first report of M. ethiopica in Turkey and the third finding of this species in Europe. References: (1) I. L. Conceição et al. Eur. J. Plant Pathol. 134:451, 2012. (2) S. N. Murga-Gutierrez et al. Nematropica. 42:57, 2012. (3) S. Širca et al. Plant Disease. 88:680, 2004. (4) A. G. Whitehead. Nematology. 15:315, 1969.
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