-
M. Oberle,
B. Krusche,
J. Ahrens,
J. R. M. Annand,
H. J. Arends,
K. Bantawa,
P. A. Bartolome,
R. Beck,
V. Bekrenev,
H. Berghaeuser, [......],
D. I. Sober,
A. Starostin,
I. Supek, M. Thiel,
A. Thomas,
M. Unverzagt,
D. P. Watts,
D. Werthmueller,
L. Witthauer,
F. Zehr
[show abstract]
[hide abstract]
ABSTRACT: Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz
for the photoproduction of neutral pion pairs in the reactions
$\vec{\gamma}p\rightarrow p\pi^0\pi^0$ and $\vec{\gamma}d\rightarrow
(n)p\pi^0\pi^0$, $\vec{\gamma}d\rightarrow (p)n\pi^0\pi^0$ off free protons and
off quasi-free nucleons bound in the deuteron for incident photon energies up
to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of
longitudinally polarized electrons and tagged with the Glasgow magnetic
spectrometer. Decay photons from the $\pi^0$ mesons, recoil protons, and recoil
neutrons were detected in the 4$\pi$ covering electromagnetic calorimeter
composed of the Crystal Ball and TAPS detectors. After kinematic reconstruction
of the final state, excellent agreement was found between the results for free
and quasi-free protons. This demonstrates that the free-nucleon behavior of
such observables can be extracted from measurements with quasi-free nucleons,
which is the only possibility for the neutron. Contrary to expectations, the
measured asymmetries are very similar for reactions off protons and neutrons.
The results are compared to the predictions from the Two-Pion-MAID reaction
model and (for the proton) also to the Bonn-Gatchina coupled channel analysis.
04/2013;
-
PANDA Collaboration,
W. Erni,
I. Keshelashvili,
B. Krusche,
M. Steinacher,
Y. Heng,
Z. Liu,
H. Liu,
X. Shen,
Q. Wang, [......],
S. Wronka,
A. Wysocka,
B. Zwieglinski,
P. Bühler,
O. Hartman,
P. Kienle,
J. Marton,
K. Suzuki,
E. Widmann,
J. Zmeskal
[show abstract]
[hide abstract]
ABSTRACT: 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 encloses a Micro-Vertex-Detector (MVD) for the inner
tracking and is followed in beam direction by a set of GEM-stations. The tasks
of the STT are the measurement of the particle momentum from the reconstructed
trajectory and the measurement of the specific energy-loss for a particle
identification. Dedicated simulations with full analysis studies of certain
proton-antiproton reactions, identified as being benchmark tests for the whole
PANDA scientific program, have been performed to test the STT layout and
performance. The results are presented, and the time lines to construct the STT
are described.
European Physical Journal A 02/2013; 49(25):1-104. · 2.19 Impact Factor
-
D. Hornidge,
P. Aguar Bartolome,
J. R. M. Annand,
H. J. Arends,
R. Beck,
V. Bekrenev,
H. Berghaeuser,
A. M. Bernstein,
A. Braghieri,
W. J. Briscoe, [......],
M. H. Sikora,
A. Starostin,
I. Supek, M. Thiel,
A. Thomas,
L. Tiator,
M. Unverzagt,
D. P. Watts,
D. Werthmueller,
L. Witthauer
[show abstract]
[hide abstract]
ABSTRACT: A precision measurement of the differential cross sections $d\sigma/d\Omega$
and the linearly polarized photon asymmetry $\Sigma \equiv \left(d\sigma_\perp
- d\sigma_\parallel \right) \slash \left(d\sigma_\perp + d\sigma_\parallel
\right)$ for the $\vec{\gamma} p \rightarrow \pi^0p$ reaction in the
near-threshold region has been performed with a tagged photon beam and almost
$4\pi$ detector at the Mainz Microtron. The Glasgow-Mainz photon tagging
facility along with the Crystal Ball/TAPS multi-photon detector system and a
cryogenic liquid hydrogen target were used. These data allowed for a precise
determination of the energy dependence of the real parts of the $S$- and all
three $P$-wave amplitudes for the first time and provide the most stringent
test to date of the predictions of Chiral Perturbation Theory and its energy
region of agreement with experiment.
11/2012;
-
PANDA Collaboration,
W. Erni,
I. Keshelashvili,
B. Krusche,
M. Steinacher,
Y. Heng,
Z. Liu,
H. Liu,
X. Shen,
Q. Wang, [......],
M. Plominski,
J. Szewinski,
K. Traczyk,
B. Zwieglinski,
P. Bühler,
A. Gruber,
P. Kienle,
J. Marton,
E. Widmann,
J. Zmeskal
[show abstract]
[hide abstract]
ABSTRACT: This document illustrates the technical layout and the expected performance
of the Micro Vertex Detector (MVD) of the PANDA experiment. The MVD will detect
charged particles as close as possible to the interaction zone. Design criteria
and the optimisation process as well as the technical solutions chosen are
discussed and the results of this process are subjected to extensive Monte
Carlo physics studies. The route towards realisation of the detector is
outlined.
07/2012;
-
V. L. Kashevarov,
A. Fix,
S. Prakhov,
P. Aguar-Bartolomé,
J. R. M. Annand,
H. J. Arends,
K. Bantawa,
R. Beck,
V. Bekrenev,
H. Berghäuser, [......],
I. I. Strakovsky,
I. M. Suarez,
I. Supek,
C. M. Tarbert, M. Thiel,
A. Thomas,
M. Unverzagt,
D. P. Watts,
D. Werthmüller,
F. Zehr
[show abstract]
[hide abstract]
ABSTRACT: The gamma p --> pi0 pi0 p reaction has been measured from threshold to 1.4
GeV using the Crystal Ball and TAPS photon spectrometers together with the
photon tagging facility at the Mainz Microtron. The experimental results
include total and differential cross sections as well as specific angular
distributions, which were used to extract partial-wave amplitudes. In
particular, the energy region below the D13(1520) resonance was studied.
04/2012;
-
The Crystal Ball at MAMI, TAPS, and Collaborations,
V. L. Kashevarov,
A. Fix,
P. Aguar-Bartolomé,
L. K. Akasoy,
J. R. M. Annand,
H. J. Arends,
K. Bantawa,
R. Beck,
V. Bekrenev, [......],
A. Starostin,
I. M. Suarez,
I. Supek,
C. M. Tarbert, M. Thiel,
A. Thomas,
M. Unverzagt,
D. P. Watts,
I. Zamboni,
F. Zehr
[show abstract]
[hide abstract]
ABSTRACT: Total and differential cross-sections for the reaction gp®p0hp\ensuremath \gamma p\rightarrow\pi^0\eta p have been measured with the Crystal Ball/TAPS detector using the tagged photon facility at the MAMI C accelerator in Mainz.
In the energy range Eg = 0.95-1.4\ensuremath E_{\gamma} = 0.95\mbox{--}1.4 GeV the reaction is dominated by the excitation and sequential decay of the D(1700)D33\ensuremath \Delta(1700)D_{33} -resonance. Angular distributions measured with high statistics allow us to determine the ratio of hadronic decay widths
GhD/GpS11\ensuremath \Gamma_{\eta\Delta}/\Gamma_{\pi S_{11}} and the ratio of the helicity amplitudes A3/2/A1/2\ensuremath A_{3/2}/A_{1/2} for this resonance.
European Physical Journal A 04/2012; 42(2):141-149. · 2.19 Impact Factor
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F. Pheron,
J. Ahrens,
J. R. M. Annand,
H. J. Arends,
K. Bantawa,
P. A. Bartolome,
R. Beck,
V. Bekrenev,
H. Berghaeuser,
B. Boillat, [......],
D. I. Sober,
A. Starostin,
I. Supek, M. Thiel,
A. Thomas,
M. Unverzagt,
D. P. Watts,
D. Werthmueller,
L. Witthauer,
F. Zehr
[show abstract]
[hide abstract]
ABSTRACT: Coherent photoproduction of $\eta$-mesons off $^3$He, i.e. the reaction
$\gamma ^3{He}\rightarrow \eta ^3{He}$, has been investigated in the
near-threshold region. The experiment was performed at the Glasgow tagged
photon facility of the Mainz MAMI accelerator with the combined Crystal Ball -
TAPS detector. Angular distributions and the total cross section were measured
using the $\eta\rightarrow \gamma\gamma$ and $\eta\rightarrow 3\pi^0\rightarrow
6\gamma$ decay channels. The observed extremely sharp rise of the cross section
at threshold and the behavior of the angular distributions are evidence for a
strong $\eta {^3{He}}$ final state interaction, pointing to the existence of a
resonant state. The search for further evidence of this state in the excitation
function of $\pi^0$-proton back-to-back emission in the $\gamma
^3{He}\rightarrow \pi^0 pX$ reaction revealed a very complicated structure of
the background and could not support previous conclusions.
01/2012;
-
E. F. McNicoll,
S. Prakhov,
I. I. Strakovsky,
P. Aguar-Bartolomé,
L. K. Akasoy,
J. R. M. Annand,
H. J. Arends,
R. A. Arndt,
Ya. I. Azimov,
K. Bantawa, [......],
I. Supek, M. Thiel,
A. Thomas,
L. Tiator,
M. Unverzagt,
D. P. Watts,
D. Werthmüller,
R. L. Workman,
I. Zamboni,
F. Zehr
[show abstract]
[hide abstract]
ABSTRACT: Here we correct a factor of 2 missed in one of figures and the
corresponding sentence in the text. It does not change any conclusions.
Physical Review C 07/2011; 84(2):29901. · 3.31 Impact Factor
-
A. Starostin,
I. M. Suarez,
B. M. K. Nefkens,
J. Ahrens,
J. R. M. Annand,
H.J. Arends,
K. Bantawa,
P. A. Bartolome,
R. Beck,
V. Bekrenev, [......],
S. Schumann,
M. H. Sikora,
D. Sober,
I. Supek, M. Thiel,
A Thomas,
M. Unverzagt,
D. P. Watts,
D. Wertmueller,
L. Witthauer
[show abstract]
[hide abstract]
ABSTRACT: The total cross section for gamma p -> 3pi0 p has been measured for the first
time from threshold to 1.4 GeV using the tagged photon beam of the Mainz
Microtron. The equipment utilized the Crystal Ball multiphoton spectrometer,
the TAPS forward detector and a particle identification detector. The gamma p
-> 3pi0 p total cross section has two broad enhancements at sqrt{s}~1.5 GeV and
1.7 GeV. We obtained the ratio of the total cross sections gamma p -> 3pi0 p to
gamma p -> eta p equal to 0.014 \pm 0.001 at sqrt{s}~1.5 GeV.
01/2011;
-
V. L. Kashevarov,
A. Fix,
P. Aguar-Bartolomé,
L. K. Akasoy,
J. R. M. Annand,
H.J. Arends,
K. Bantawa,
R. Beck,
V. Bekrenev,
H. Berghäuser, [......],
I. M. Suarez,
I. Supek,
C. Tarbert, M. Thiel,
A Thomas,
M. Unverzagt,
D. P. Watts,
D. Werthmüller,
I. Zamboni,
F. Zehr
[show abstract]
[hide abstract]
ABSTRACT: The circular photon asymmetry for pi0 eta photoproduction on the proton was measured for the first time at the tagged photon facility of the MAMI C accelerator using the Crystal Ball/TAPS photon spectrometer. The experimental results are interpreted within a phenomenological isobar model that confirms the dominant role of the Delta(1700)D33 resonance. The measured asymmetry allows us to identify small contributions from positive-parity resonances via interference terms with the dominant D33 amplitude. Comment: 11 pages, 3 figures, submitted to Phys.Lett. B
09/2010;
-
E. F. McNicoll,
S. Prakhov,
I. I. Strakovsky,
P. Aguar-Bartolomepmainz,
L. K. Akasoy,
J. R. M. Annand,
H.J. Arends,
R. A. Arndt,
Ya. I. Azimov,
K. Bantawa, [......],
I. Supek, M. Thiel,
A Thomas,
L. Tiator,
M. Unverzagt,
D. P. Watts,
D. Werthmueller,
R. L. Workman,
I. Zamboni,
F. Zehr
[show abstract]
[hide abstract]
ABSTRACT: The gp-->etap reaction has been measured with the Crystal Ball and TAPS multiphoton spectrometers in the energy range from the production threshold of 707 MeV to 1.4 GeV (1.49 =< W >= 1.87 GeV). Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz Microtron MAMI-C and momentum analyzed by the Glasgow Tagging Spectrometer were used for the eta-meson production. Our accumulation of 3.8 x 10^6 gp-->etap-->3pi0p-->6gp events allows a detailed study of the reaction dynamics. The gp-->etap differential cross sections were determined for 120 energy bins and the full range of the production angles. Our data show a dip near W = 1680 MeV in the total cross section caused by a substantial dip in eta production at forward angles. The data are compared to predictions of previous SAID and MAID partial-wave analyses and to thelatest SAID and MAID fits that have included our data. Comment: 15 pages, 12 figures
07/2010;
-
The PANDA Collaboration,
W. Erni,
I. Keshelashvili,
B. Krusche,
M. Steinacher,
Y. Heng,
Z Liu,
H Liu,
X Shen,
O. Wang, [......],
M. Plominski,
J. Szewinski,
K. Traczyk,
B. Zwieglinski,
P. Buehler,
A Gruber,
P. Kienle,
J. Marton,
E. Widmann,
J. Zmeskal
[show abstract]
[hide abstract]
ABSTRACT: This document is the Technical Design Report covering the two large spectrometer magnets of the PANDA detector set-up. It shows the conceptual design of the magnets and their anticipated performance. It precedes the tender and procurement of the magnets and, hence, is subject to possible modifications arising during this process. Comment: 10 pages, 14MB, accepted by FAIR STI in May 2009, editors: Inti Lehmann (chair), Andrea Bersani, Yuri Lobanov, Jost Luehning, Jerzy Smyrski, Technical Coordiantor: Lars Schmitt, Bernd Lewandowski (deputy), Spokespersons: Ulrich Wiedner, Paola Gianotti (deputy)
PANDA Collaboration. 07/2009;
-
The PANDA Collaboration: W. Erni,
I. Keshelashvili,
B. Krusche,
M. Steinacher,
Y. Heng,
Z. Liu,
H. Liu,
X. Shen,
O. Wang,
H. Xu, [......],
M. Plominski,
J. Szewinski,
K. Traczyk,
B. Zwieglinski,
P. Buehler,
A. Gruber,
P. Kienle,
J. Marton,
E. Widmann,
J. Zmeskal
[show abstract]
[hide abstract]
ABSTRACT: This document is the Technical Design Report covering the two large
spectrometer magnets of the PANDA detector set-up. It shows the
conceptual design of the magnets and their anticipated performance. It
precedes the tender and procurement of the magnets and, hence, is
subject to possible modifications arising during this process.
06/2009;
-
A. Starostin,
B. M. K. Nefkens,
J. Ahrens,
J. R. M. Annand,
H. J. Arends,
K. Bantawa,
P. A. Bartolome,
R. Beck,
V. Bekrenev,
A. Braghieri, [......],
S. Schumann,
M. H. Sikora,
D. Sober,
I. M. Suarez,
I. Supek,
C. M. Tarbert, M. Thiel,
A. Thomas,
M. Unverzagt,
D. P. Watts
[show abstract]
[hide abstract]
ABSTRACT: A new upper limit of 2.3×10-4 on the branching ratio of the decay ω→ηπ0 has been obtained using the Crystal Ball multiphoton spectrometer at the Mainz Microtron MAMI. This decay is forbidden by charge-conjugation invariance of the strong and electromagnetic interactions. We have also obtained the upper limit of 2.3×10-4 for the forbidden decay ω→3π0 and the upper limit of 2.4×10-4 for ω→2π0.
Phys. Rev. C. 06/2009; 79(6).
-
PANDA Collaboration,
W. Erni,
I. Keshelashvili,
B. Krusche,
M. Steinacher,
Y. Heng,
Z Liu,
H Liu,
X Shen,
O. Wang, [......],
P. Buehler,
A Gruber,
P. Kienle,
J. Marton,
E. Widmann,
J. Zmeskal,
M. F. M. Lutz,
B. Pire,
O. Scholten,
R. Timmermans
[show abstract]
[hide abstract]
ABSTRACT: To study fundamental questions of hadron and nuclear physics in interactions of antiprotons with nucleons and nuclei, the universal PANDA detector will be built. Gluonic excitations, the physics of strange and charm quarks and nucleon structure studies will be performed with unprecedented accuracy thereby allowing high-precision tests of the strong interaction. The proposed PANDA detector is a state-of-the art internal target detector at the HESR at FAIR allowing the detection and identification of neutral and charged particles generated within the relevant angular and energy range. This report presents a summary of the physics accessible at PANDA and what performance can be expected. Comment: 216 pages
03/2009;
-
V. L. Kashevarov,
A. Fix,
P. Aguar-Bartolome,
L. K. Akasoy,
J. R. M. Annand,
H.J. Arends,
K. Bantawa,
R. Beck,
V. Bekrenev,
H. Berghauser, [......],
A. Starostin,
I. M. Suarez,
I. Supek,
C. M. Tarbert, M. Thiel,
A Thomas,
M. Unverzagt,
D. P. Watts,
I. Zamboni,
F. Zehr
[show abstract]
[hide abstract]
ABSTRACT: Total and differential cross sections for the reaction gamma p -> pi^o eta p have been measured with the Crystal Ball/TAPS detector using the tagged photon facility at the MAMI C accelerator in Mainz. In the energy range E_gamma=0.95-1.4 GeV the reaction is dominated by the excitation and sequential decay of the Delta(1700)D33 resonance. Angular distributions measured with high statistics allow us to determine the ratio of hadronic decay widths \Gamma_{\eta \Delta}/\Gamma_{\pi S11} and the ratio of the helicity amplitudes A_{3/2}/A_{1/2} for this resonance. Comment: 9 pages, 11 figures
01/2009;
-
S. Prakhov,
B. M. K. Nefkens,
P. Aguar-Bartolome,
L. K. Akasoy,
J. R. M. Annand,
H.J. Arends,
K. Bantawa,
R. Beck,
V. Bekrenev,
H. Berghauser, [......],
A. Starostin,
I. M. Suarez,
I. Supek,
C. M. Tarbert, M. Thiel,
A Thomas,
M. Unverzagt,
D. P. Watts,
I. Zamboni,
F. Zehr
[show abstract]
[hide abstract]
ABSTRACT: The dynamics of the $\eta\to 3\pi^0$ decay have been studied with the Crystal Ball multiphoton spectrometer and the TAPS calorimeter. Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz microtron MAMI-C and tagged by the Glasgow photon spectrometer were used for $\eta$-meson production. The analysis of $3 \times 10^6$ $\gamma p \to \eta p \to 3\pi^0 p \to 6\gamma p$ events yields the value $\alpha=-0.032\pm0.003$ for the $\eta\to 3\pi^0$ slope parameter, which agrees with the majority of recent experimental results and has the smallest uncertainty. The $\pi^0\pi^0$ invariant-mass spectrum was investigated for the occurrence of a cusplike structure in the vicinity of the $\pi^+\pi^-$ threshold. The observed effect is small and does not affect our measured value for the slope parameter.
12/2008;
-
PANDA Collaboration,
W. Erni,
I. Keshelashvili,
B. Krusche,
M. Steinacher,
Y. Heng,
Z Liu,
H Liu,
X Shen,
O. Wang, [......],
M. Plominski,
J. Szewinski,
K. Traczyk,
B. Zwieglinski,
P. Buehler,
A Gruber,
P. Kienle,
J. Marton,
E. Widmann,
J. Zmeskal
[show abstract]
[hide abstract]
ABSTRACT: This document presents the technical layout and the envisaged performance of the Electromagnetic Calorimeter (EMC) for the PANDA target spectrometer. The EMC has been designed to meet the physics goals of the PANDA experiment, which is being developed for the Facility for Antiproton and Ion Research (FAIR) at Darmstadt, Germany. The performance figures are based on extensive prototype tests and radiation hardness studies. The document shows that the EMC is ready for construction up to the front-end electronics interface. Comment: 199 pages, submitted to FAIR STI on July 1st 2008, Editors: Fritz-Herbert Heinsius, Bertram Kopf, Bernd Lewandowski (Deputy Technical Coordinator), Herbert L\"ohner, Rainer Novotny (Project Coordinator), Klaus Peters, Philippe Rosier, Lars Schmitt (Technical Coordinator), Alexander Vasiliev; Spokespersons: Ulrich Wiedner, Paola Gianotti (deputy)
10/2008;
-
[show abstract]
[hide abstract]
ABSTRACT: For the first time, the response function to high-energy photons of a 3times3 matrix comprising large volume LYSO crystals was measured using energy marked photons provided by the tagged photon facility of MAMI. The crystal quality was determined based on the optical transparency, the intrinsic radioactivity and the luminescence yield. Energy and time resolutions for photons up to 490 MeV photon energy have been deduced from the reconstruction of the electromagnetic shower deposited into the crystal array and the data deliver very promising results.
IEEE Transactions on Nuclear Science 07/2008; · 1.45 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The response function of a 3 times 3 matrix of 200-mm-long PWO-II crystals has been measured with energy-marked photons up to 675 MeV energy. For the first time the crystals were readout individually with one large area avalanche photo diode of the second generation operating at a temperature of 0degC. The reconstructed electromagnetic shower distributions show excellent energy resolutions down to 40 MeV. Reducing the temperature and increasing the light collection by an additional large-area avalanche photo diode can achieve further improvement.
IEEE Transactions on Nuclear Science 07/2008; · 1.45 Impact Factor
