Publications (78)
Search for Narrow Nucleon Resonances below Pion Threshold in the H(e,e'pi^+)X and D(e,e'p)X Reactions
M. Kohl, M. Ases Antelo, C. Ayerbe +23
In two series of high-resolution coincidence experiments at the three-spectrometer facility at MAMI, the H(e,e'pi^+)X and D(e,e'p)X reactions were studied to search for narrow nucl…
Systematic treatment of hypernuclear data and application to the hypertriton
P. Eckert, P. Achenbach, M. Aragones Fontbote +26
A database is under construction to provide a complete collection of published basic properties of hypernuclei such as Î binding energies, lifetimes, or excitation energies. From…
Particle tracking in kaon electroproduction with cathode-charge sampling in multi-wire proportional chambers
P. Achenbach, C. Ayerbe Gayoso, J. C. Bernauer +18
Wire chambers are routinely operated as tracking detectors in magnetic spectrometers at high-intensity continuous electron beams. Especially in experiments studying reactions with…
Measurement of Rlt and Atl in the 4He(e,e'p)3H Reaction at pmiss of 130-300 MeV/c
K. A. Aniol, M. B. Epstein, E. Gama +41
We have measured the 4He(e,e'p)3H reaction at missing momenta of 130-300 MeV/c using the three-spectrometer facility at the Mainz microtron MAMI. Data were taken in perpendicular k…
Beam-Normal Single Spin Asymmetry in Elastic Electron Scattering off Si and Zr
A. Esser, M. Thiel, P. Achenbach +30
We report on a new measurement of the beam-normal single spin asymmetry in the elastic scattering of 570 MeV transversely polarized electrons off Si and $^{…
Search for light massive gauge bosons as an explanation of the anomaly at MAMI
H. Merkel, P. Achenbach, C. Ayerbe Gayoso +33
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 paper, the search for the sig…
High-precision determination of the electric and magnetic form factors of the proton
J. C. Bernauer, P. Achenbach, C. Ayerbe Gayoso +22
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 mea…
Measurement of the reaction close to threshold and at low
A1 Collaboration, I. FriÅ¡ÄiÄ, P. Achenbach +21
The cross section of the reaction has been measured for five kinematic settings at an invariant mass of MeV and for a four-momentum transfer of $Q^2 = 0.0…
Measurement of the cross sections at
M. MihoviloviÄ, L. Doria, P. Achenbach +22
We present the findings of a study based on a new inelastic electron-scattering experiment on the nucleus focusing on the kinematic region of $Q^2=0.8\,\mathrm{…
Beam-Normal Single-Spin Asymmetry in Pb at low energy: discrepancy resolved or new kinematic puzzle?
A. Esser, N. Kozyrev, K. Aulenbacher +17
A longstanding discrepancy between measured and predicted beam-normal single-spin asymmetries in elastic electron scattering off Pb has challenged our understanding…
The electric and magnetic form factors of the proton
A1 Collaboration, J. C. Bernauer, M. O. Distler +21
The paper describes a precise measurement of electron scattering off the proton at momentum transfers of \ GeV. The average point-to-point error…
The neutron charge form factor and target analyzing powers from pol.3He(pol e,e'n)-scattering
J. Bermuth, P. Merle, C. C. Carasco +40
The charge form factor of the neutron has been determined from asymmetries measured in quasi--elastic pol.3He(pol e,e'n) at a momentum transfer of 0.67(GeV/c)^2. In addition, the t…
Measurement of the recoil polarization in the p (\vec e, e' \vec p) pi^0 reaction at the Î(1232) resonance
Th. Pospischil, P. Bartsch, D. Baumann +39
The recoil proton polarization has been measured in the p (\vec e,e'\vec p) pi^0 reaction in parallel kinematics around W = 1232 MeV, Q^2 = 0.121 (GeV/c)^2 and epsilon = 0.718 usin…
Measurement of the neutron electric to magnetic form factor ratio at Q2 = 1.58 GeV2 using the reaction 3He(e,e'n)pp
B. S. Schlimme, P. Achenbach, C. A. Ayerbe Gayoso +29
A measurement of beam helicity asymmetries in the reaction 3He(e,e'n)pp has been performed at the Mainz Microtron in quasielastic kinematics in order to determine the electric to m…
Search for Light Gauge Bosons of the Dark Sector at the Mainz Microtron
H. Merkel, P. Achenbach, C. Ayerbe Gayoso +19
A new exclusion limit for the electromagnetic production of a light U(1) gauge boson γ' decaying to e^+e^- was determined by the A1 Collaboration at the Mainz Microtron. Such ligh…
Theoretical framework to analyze searches for hidden light gauge bosons in electron scattering fixed target experiments
T. Beranek, H. Merkel, M. Vanderhaeghen
Motivated by anomalies in cosmic ray observations and by attempts to solve questions of the Standad Model of particle physics like the (g-2)_mu discrepancy, U(1) extensions of the…
Electron beam studies of light collection in a scintillating counter with embedded fibers
M. LauÃ, P. Achenbach, S. Aulenbacher +28
The light collection of several fiber configurations embedded in a box-shaped plastic scintillating counter was studied by scanning with minimum ionizing electrons. The light was r…
Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR
PANDA Collaboration, B. P. Singh, W. Erni +532
Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description fo…
Vertical Beam Polarization at MAMI
B. S. Schlimme, P. Achenbach, K. Aulenbacher +35
For the first time a vertically polarized electron beam has been used for physics experiments at MAMI in the energy range between 180 and 855 MeV. The beam-normal single-spin asymm…
Measurement of the asymmetries in 3He(e,e'p)d and 3He(e,e'p)np
P. Achenbach, D. Baumann, R. Boehm +48
The electron-target-asymmetries A_parallel and A_perpendicular with target spin parallel and perpendicular to the momentum transfer q were measured for both the two-- and three-bod…
Measurement of the Ar(e,e) elastic scattering cross section with a novel gas-jet target
M. Littich, L. Doria, P. Brand +35
We report on a measurement of elastic electron scattering on argon performed with a novel cryogenic gas-jet target at the Mainz Microtron accelerator MAMI. The luminosity is estima…
Investigation of the Exclusive ^{3}He(e,e'pn)p Reaction
D. G. Middleton, J. R. M. Annand, M. Ases Antelo +46
Cross sections for the ^{3}He(e,e'pn)p reaction were measured for the first time at energy transfers of 220 and 270 MeV for several momentum transfers ranging from 300 to 450 MeV/c…
New detectors for the kaon and hypernuclear experiments with KaoS at MAMI and with PANDA at GSI
P. Achenbach, C. Ayerbe Gayoso, R. Böhm +31
The KaoS spectrometer at the Mainz Microtron MAMI, Germany, is perceived as the ideal candidate for a dedicated spectrometer in kaon and hypernuclei electroproduction. KaoS will be…
Dark Sectors and New, Light, Weakly-Coupled Particles
R. Essig, J. A. Jaros, W. Wester +86
Dark sectors, consisting of new, light, weakly-coupled particles that do not interact with the known strong, weak, or electromagnetic forces, are a particularly compelling possibil…
Development of large area focal plane detectors for MAGIX
P. Gülker, P. Achenbach, S. Aulenbacher +20
MAGIX is a planned experiment that will be implemented at the upcoming accelerator MESA in Mainz. Due to its location in the energy-recovering lane of the accelerator beam-currents…
PANDA Phase One
G. Barucca, F. Davì, G. Lancioni +421
The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. T…
Nuclear density dependence of polarization transfer in quasi-elastic reactions
T. Kolar, W. Cosyn, C. Giusti +52
The ratio of the transverse and longitudinal component of polarization transfer to protons in the quasi-elastic reaction, $P^{\prime}_x/P^{\prime}…
Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
PANDA Collaboration, B. Singh, W. Erni +502
Simulation results for future measurements of electromagnetic proton form factors at \PANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision w…
A Large-Scale FPGA-Based Trigger and Dead-Time Free DAQ System for the Kaos Spectrometer at MAMI
P. Achenbach, C. Ayerbe Gayoso, J. C. Bernauer +24
The Kaos spectrometer is maintained by the A1 collaboration at the Mainz Microtron MAMI with a focus on the study of (e,e'K^+) coincidence reactions. For its electron-arm two verti…
Measurement of the Beam-Recoil Polarization in Low-Energy Virtual Compton Scattering from the Proton
L. Doria, P. Janssens, P. Achenbach +38
Double-polarization observables in the reaction have been measured at . The experiment was performed at the spectrometer set…
Observation of a unitary cusp in the threshold γp -> Ï^{0}p reaction
A. M. Bernstein, E. Shuster, R. Beck +4
A rigorous multipole analysis of the recent γp -> Ï^{0}p cross section measurement is presented. The data were taken using the photon spectrometer TAPS at the tagged photon beam…
Measurement of Propagation Time Dispersion in a Scintillator
P. Achenbach, C. Ayerbe Gayoso, J. Bernauer +12
One contribution to the time resolution of a scintillation detector is the signal time spread due to path length variations of the detected photons from a point source. In an exper…
Feasibility study for the measurement of TDAs at PANDA in
PANDA Collaboration, B. Singh, W. Erni +508
The exclusive charmonium production process in annihilation with an associated meson is studied in the framework of QCD collinear factoriza…
Non-forward radiative corrections to electron-carbon scattering
M. MihoviloviÄ, A. B. Weber, P. Achenbach +37
Radiative corrections to elastic scattering represent an important part of the interpretation of electron-induced nuclear reactions at small energy transfers, where they make for a…
Consistent threshold pi0 electro-production at Q^2=0.05, 0.10, and 0.15 GeV^2/c^2
H. Merkel, P. Achenbach, C. Ayerbe Gayoso +22
New, accurate data are presented on the near threshold p(e,e'p)pi^0 reaction in the range of four-momentum transfers between Q^2=0.05 and 0.15GeV^2/c^2. The data were taken with th…
Measurement of the LT-asymmetry in Ï^0 electroproduction at the energy of the Î(1232) resonance
D. Elsner, A. Süle, P. Barneo +29
The reaction p(e,e'p)pi^0 has been studied at Q^2=0.2 (GeV/c)^2 in the region of W=1232 MeV. From measurements left and right of q, cross section asymmetries Ï_LT have been obtain…
Precise Neutron Magnetic Form Factors
G. Kubon, H. Anklin, P. Bartsch +36
Precise data on the neutron magnetic form factor G_{mn} have been obtained with measurements of the ratio of cross sections of D(e,e'n) and D(e,e'p) up to momentum transfers of Q^2…
Comparison of recoil polarization in the process for protons extracted from and shell
T. Kolar, S. Paul, T. Brecelj +29
We present first measurements of the double ratio of the polarization transfer components f…
Components of polarization-transfer to a bound proton in a deuteron measured by quasi-elastic electron scattering
A1 Collaboration, D. Izraeli, I. Yaron +33
We report the first measurements of the transverse ( and ) and longitudinal () components of the polarization transfer to a bound proton in the deuteron via th…
Measurement of the Generalized Polarizabilities of the Proton at Intermediate
H. Fonvieille, J. BeriÄiÄ, L. Correa +35
Background: Generalized polarizabilities (GPs) are important observables to describe the nucleon structure, and measurements of these observables are still scarce. Purpose: This pa…
The influence of Fermi motion on the comparison of the polarization transfer to a proton in elastic and quasi-elastic scattering
S. Paul, T. Brecelj, H. Arenhövel +35
A comparison between polarization-transfer to a bound proton in quasi-free kinematics by the A knockout reaction and that in elastic scattering off a free proto…
Technical Design Report for the: PANDA Straw Tube Tracker
PANDA Collaboration, W. Erni, I. Keshelashvili +470
This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encl…
Final State Interaction Effects in pol 3He(pol e,e'p)
C. Carasco, J. Bermuth, P. Merle +40
Asymmetries in quasi-elastic pol 3He(pol e,e'p) have been measured at a momentum transfer of 0.67 (GeV/c)^2 and are compared to a calculation which takes into account relativistic…
New Insight in the -Dependence of Proton Generalized Polarizabilities
J. BeriÄiÄ, L. Correa, M. Benali +35
Virtual Compton scattering on the proton has been investigated at three yet unexplored values of the four-momentum transfer : 0.10, 0.20 and 0.45 GeV, at the Mainz Microtr…
Monte Carlo simulation of virtual Compton scattering below pion threshold
P. Janssens, L. Van Hoorebeke, H. Fonvieille +22
This paper describes the Monte Carlo simulation developed specifically for the VCS experiments below pion threshold that have been performed at MAMI and JLab. This simulation gener…
First measurements of the ^16O(e,e'pn)^14N reaction
D. G. Middleton, J. R. M. Annand, C. Barbieri +39
This paper reports on the first measurement of the ^16O(e,e'pn)^14N reaction. Data were measured in kinematics centred on a super-parallel geometry at energy and momentum transfers…
A short-orbit spectrometer for low-energy pion detection in electroproduction experiments at MAMI
D. Baumann, M. Ding, I. FriÅ¡ÄiÄ +7
A new Short-Orbit Spectrometer (SOS) has been constructed and installed within the experimental facility of the A1 collaboration at Mainz Microtron (MAMI), with the goal to detect…
Lowest Q^2 Measurement of the gamma*p -> Delta Reaction: Probing the Pionic Contribution
S. Stave, M. O. Distler, I. Nakagawa +29
To determine nonspherical angular momentum amplitudes in hadrons at long ranges (low Q^2), data were taken for the p(\vec{e},e'p)Ï^0 reaction in the Delta region at Q^2=0.060 (GeV…
Two-Photon EXchange -- TPEX
R. Alarcon, R. Beck, J. C. Bernauer +33
We propose a new measurement of the ratio of positron-proton to electron-proton, elastic scattering at DESY to determine the contributions beyond single-photon exchange, which are…
Fundamental Physics at the Intensity Frontier
J. L. Hewett, H. Weerts, R. Brock +465
The Proceedings of the 2011 workshop on Fundamental Physics at the Intensity Frontier. Science opportunities at the intensity frontier are identified and described in the areas of…
Measurement of Strange Quark Contributions to the Vector Form Factors of the Proton at Q**2=0.22 (GeV/c)**2
S. Baunack, K. Aulenbacher, D. Balaguer RÃos +24
A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q^2=0.22 (GeV/c)^2 is reported…
Operation and characterization of a windowless gas jet target in high-intensity electron beams
B. S. Schlimme, S. Aulenbacher, P. Brand +54
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…
Virtual Compton Scattering measurements in the nucleon resonance region
A. Blomberg, H. Atac, N. Sparveris +25
We report on new measurements of the electric Generalized Polarizability (GP) of the proton in a kinematic region where a puzzling dependence on momentum transfer has been o…
Measurement of the beam-helicity asymmetry in the p(e_pol,e'p)pi_0 reaction at the energy of the Delta(1232) resonance
P. Bartsch, D. Baumann, J. Bermuth +32
In a p(e_pol,e'p)pi_0 out-of-plane coincidence experiment at the 3-spectrometer setup of the Mainz Microtron MAMI, the beam-helicity asymmetry has been precisely measured around th…
Low- elastic electron-proton scattering using a gas jet target
Y. Wang, J. C. Bernauer, B. S. Schlimme +54
In this paper, we describe an experiment measuring low- elastic electron-proton scattering using a newly developed cryogenic supersonic gas jet target in the A1 three-spectrom…
Measurement of the Electric Form Factor of the Neutron at Q^2 = 0.3-0.8 (GeV/c)^2
D. I. Glazier, M. Seimetz, J. R. M. Annand +41
The electric form factor of the neutron, G_En, has been measured at the Mainz Microtron by recoil polarimetry in the quasielastic D(e_pol,e'n_pol)p reaction. Three data points have…
High-precision Studies of the He(e,ep) Reaction at the Quasielastic Peak
R. E. J. Florizone, W. Bertozzi, J. P. Chen +38
Precision studies of the reaction He(e,ep) using the three-spectrometer facility at the Mainz microtron MAMI are presented. All data are for quasielastic kinematics…
Recoil polarization and beam-recoil double polarization measurement of ηelectroproduction on the proton in the region of the S_{11}(1535) resonance
H. Merkel, P. Achenbach, C. A. Ayerbe Gayoso +20
The beam-recoil double polarization P_{x'}^h and P_{z'}^h and the recoil polarization P_{y'} were measured for the first time for the p(\vec{e},e'\vec{p})ηreaction at a four-momen…
Study of Two-Photon Exchange via the Beam Transverse Single Spin Asymmetry in Electron-Proton Elastic Scattering at Forward Angles over a Wide Energy Range
B. Gou, J. Arvieux, K. Aulenbacher +26
We report on a new measurement of the beam transverse single spin asymmetry in electron-proton elastic scattering, , at five beam energies from 315.1 MeV to 1508.4…
A new measurement of the structure functions and in virtual Compton scattering at 0.33 (GeV/c)
A1 Collaboration, P. Janssens, L. Doria +36
The cross section of the reaction has been measured at (GeV/c). The experiment was performed using the electron beam of the MAMI accelerator and…
High accuracy synchrotron radiation interferometry with relativistic electrons
P. Klag, P. Achenbach, T. Akiyama +28
A high-precision hypernuclear experiment has been performed at the Mainz Microtron (MAMI) to determine the hypertriton Î binding energy via decay-pion spectroscopy. A key element…
Polarization-transfer measurement to a large-virtuality bound proton in the deuteron
A1 Collaboration, I. Yaron, D. Izraeli +28
Possible differences between free and bound protons may be observed in the ratio of polarization-transfer components, . We report the measurement of , in the…
Virtual Compton Scattering measurements in the $γ^* N\to Î$ transition
N. F. Sparveris, P. Achenbach, C. Ayerbe Gayoso +30
We report on new H measurements in the resonance at (GeV/c) carried out simultaneously with H. It is the lowest fo…
Reply to Comment on "High-Precision Determination of the Electric and Magnetic Form Factors of the Proton"
J. C. Bernauer, P. Achenbach, C. Ayerbe Gayoso +22
In arXiv:1108.3058v1 [nucl-ex], Arrington criticizes the Coulomb corrections we applied in the analysis of high precision form factor data (see Phys.Rev.Lett.105:242001, 2010, arXi…
Measurements of the γ* p --> Î(1232) reaction at low Q2
N. Sparveris, S. Stave, P. Achenbach +29
We report new p measurements in the resonance at the low momentum transfer region utilizing the magnetic spectrometers of the A1 Collab…
Measurement of polarization-transfer to bound protons in carbon and its virtuality dependence
A1 Collaboration, D. Izraeli, T. Brecelj +26
We measured the ratio of the transverse to longitudinal components of polarization transferred from electrons to bound protons in by the $^{12}\math…
Polarization transfer in the HeH reaction
S. Dieterich, P. Bartsch, D. Baumann +39
Polarization transfer in the 4He(e,e'p)3H reaction at a Q^2 of 0.4 (GeV/c)^2 was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization…
Exclusive electroproduction of K+ Lambda and K+ Sigma^0 final states at Q^2 = 0.030-0.055 (GeV/c)^2
P. Achenbach, C. Ayerbe Gayoso, J. C. Bernauer +32
Cross section measurements of the exclusive p(e,e'K+)Lambda,Sigma^0 electroproduction reactions have been performed at the Mainz Microtron MAMI in the A1 spectrometer facility usin…
Determination of quadrupole strengths in the gamma*p-->Delta(1232) transition at Q2= 0.20 (GeV/c)2
N. F. Sparveris, P. Achenbach, C. Ayerbe Gayoso +29
We report new precise p measurements at the peak of the resonance at $Q^2=\unit[0.20](GeV/c)^2$ performed at the Mainz Microtron (MAMI). Th…
Technical Design Report for the PANDA Endcap Disc DIRC
Panda Collaboration, F. Davi, W. Erni +460
PANDA (anti-Proton ANnihiliation at DArmstadt) is planned to be one of the four main experiments at the future international accelerator complex FAIR (Facility for Antiproton and I…
Measurement of polarization transfer in the quasi-elastic process
T. Kolar, P. Achenbach, M. Christmann +32
Polarization transfer to a bound proton in polarized electron knock-out reactions, , is a powerful tool to look for in-medium modification of…
Separated cross sections in Ï^0 electroproduction at threshold at Q^2 = 0.05 GeV^2/c^2
M. Weis, P. Bartsch, D. Baumann +26
The differential cross sections Ï_0=Ï_T+εÏ_L, Ï_{LT}, and Ï_{TT} of Ï^0 electroproduction from the proton were measured from threshold up to an additional center of mass ene…
In-beam tests of scintillating fibre detectors at MAMI and at GSI
P. Achenbach, C. Ayerbe Gayoso, J. C. Bernauer +27
The performance of scintillating fibre detectors was studied with electrons at the spectrometer facility of the Mainz microtron MAMI, as well as in a C-12 beam of 2 AGeV energy and…
Beam-helicity asymmetry in photon and pion electroproduction in the Delta(1232) resonance region at Q^2= 0.35 (GeV/c)^2
A1 Collaboration, I. K. Bensafa, P. Achenbach +40
The beam-helicity asymmetry has been measured simultaneously for the reactions (e p \to e p γ) and (e p \to e p Ï^0) in the resonance region at 0.35 (GeV/c)…
Measurement of the α-particle monopole transition form factor challenges theory: a low-energy puzzle for nuclear forces?
S. Kegel, P. Achenbach, S. Bacca +30
We perform a systematic study of the -particle excitation from its ground state to the resonance. The so-called monopole transition form factor is investigated…
Observation of Lambda H-4 hyperhydrogen by decay-pion spectroscopy in electron scattering
A. Esser, S. Nagao, F. Schulz +38
At the Mainz Microtron MAMI, the first high-resolution pion spectroscopy from decays of strange systems was performed by electron scattering off a Be-9 target in order to study the…
First measurement of proton's charge form factor at very low with initial state radiation
M. MihoviloviÄ, A. B. Weber, P. Achenbach +36
We report on a new experimental method based on initial-state radiation (ISR) in e-p scattering, in which the radiative tail of the elastic e-p peak contains information on the pro…
The focal plane proton-polarimeter for the 3-spectrometer setup at MAMI
T. Pospischil, P. Bartsch, D. Baumann +46
For experiments of the type A(\vec e,e'\vec p) the 3-spectrometer setup of the A1 collaboration at MAMI has been supplemented by a focal plane proton-polarimeter. To this end, a ca…