-
A. Thiel,
A. V. Anisovich,
D. Bayadilov,
B. Bantes,
R. Beck,
Yu. Beloglazov,
M. Bichow,
S. Böse, K. -Th. Brinkmann,
Th. Challand, [......],
V. Sokhoyan,
V. Sumachev,
U. Thoma,
H. van Pee,
D. Walther,
Ch. Wendel,
U. Wiedner,
A. Wilson,
A. Winnebeck,
Y. Wunderlich
[show abstract]
[hide abstract]
ABSTRACT: The first measurement is reported of the double-polarization observable G in
photoproduction of neutral pions off protons, covering the photon energy range
from 620 to 1120 MeV and the full solid angle. G describes the correlation
between the photon polarization plane and the scattering plane for protons
polarized along the direction of the incoming photon. The observable is highly
sensitive to contributions from baryon resonances. The new results are compared
to the predictions from SAID, MAID, and BnGa partial wave analyses. In spite of
the long-lasting efforts to understand {\gamma}p -> p{\pi} 0 as the simplest
photoproduction reaction, surprisingly large differences between the new data
and the latest predictions are observed which are traced to different
contributions of the N (1535) with spin-parity J^P = 1/2^- and N (1520) with
J^P = 3/2^- . In the third resonance region, where N (1680) with J^P = 5/2^+
production dominates, the new data are reasonably close to the predictions.
07/2012;
-
S. Abd El-Samad,
E. Borodina, K. -Th. Brinkmann,
H. Clement,
E. Doroshkevich,
R. Dzhygadlo,
K. Ehrhardt,
A. Erhardt,
W. Eyrich,
H. Freiesleben, [......],
M. Krapp,
J. Ritman,
E. Roderburg,
M. Roeder,
M. Schulte-Wissermann,
W. Schroeder,
T. Sfzick,
G. J. Wagner,
P. Wintz,
P. Wuestner
[show abstract]
[hide abstract]
ABSTRACT: Measurements of the $pp \to pK^+\Lambda$ reaction at $T_p$ = 2.28 GeV have
been carried out at COSY-TOF. In addition to the $\Lambda p$ FSI and $N^*$
resonance excitation effects a pronounced narrow structure is observed in the
Dalitz plot and in its projection on the $p\Lambda$-invariant mass. The
structure appears at the $pp \to $N$K^+\Sigma$ threshold and is interpreted as
$\Sigma$N cusp effect. The observed width of 20 MeV/$c^2$ is substantially
broader than anticipated from previous inclusive measurements. Angular
distributions of this cusp structure are shown to be dissimilar to those in the
residual $pK^+\Lambda$ channel, but similar to those observed in the
$pK^+\Sigma^0$ channel.
06/2012;
-
The COSY-TOF Collaboration,
M. Abdel-Bary,
S. Abdel-Samad, K-Th. Brinkmann,
H. Clement,
J. Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
K. Ehrhardt,
A. Erhardt, [......],
A. Teufel,
W. Ullrich,
G. J. Wagner,
M. Wagner,
R. Wenzel,
A. Wilms,
P. Wintz,
S. Wirth,
P. Wüstner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: This paper reports results on simultaneous measurements of the reaction channels pp
® \rightarrow
pK
+
L \Lambda and pp
® \rightarrow
pK
+
S0 \Sigma^{0}_{} at excess energies of 204, 239, and 284MeV (L \Lambda and 127, 162, and 207MeV (S0 \Sigma^{0}_{} . Total and differential cross-sections are given for both reactions. It is concluded from the measured total cross-sections
that the high-energy limit of the cross-section ratio is almost reached at an excess energy of only about 200MeV. From the
differential distributions observed in the overall CMS as well as in the Jackson and helicity frames, a significant contribution
of interfering nucleon resonances to the L \Lambda production mechanism is concluded while resonant S0 \Sigma^{0}_{} production seems to be of lesser importance and takes place only through specific partial waves of the entrance channel.
The data also indicate that kaon exchange plays a minor role in the case of L \Lambda but an important role for S0 \Sigma^{0}_{} production. Thus the peculiar energy dependence of the L \Lambda/S0 \Sigma^{0}_{} cross-section ratio appears in a new light as its explanation requires more than mere differences between the p
L \Lambda and the p
S0 \Sigma^{0}_{} final-state interaction. The data provide a benchmark for theoretical models already available or yet to come.
European Physical Journal A 04/2012; 46(1):27-44. · 2.19 Impact Factor
-
The COSY-TOF Collaboration,
S. Abd El-Bary,
S. Abd El-Samad,
R. Bilger, K. -Th. Brinkmann,
H. Clement,
M. Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
K. Ehrhardt, [......],
G. Y. Sun,
J. Wächter,
G. J. Wagner,
M. Wagner,
U. Weidlich,
A. Wilms,
P. Wintz,
S. Wirth,
G. Zhang,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The two-pion production reaction pp → ppπ+π− was measured with a polarized proton beam at T
p
≈ 750 and 800MeV using the short version of the COSY-TOF spectrometer. The implementation of a delayed-pulse technique for
Quirl and central calorimeter provided positive π+ identification in addition to the standard particle identification, energy determination as well as time-of-flight and angle
measurements. Thus all four-momenta of the emerging particles could be determined with 1–4 overconstraints. Total and differential
cross-sections as well as angular distributions of the vector analyzing power have been obtained. They are compared to previous
data and theoretical calculations. In contrast to predictions we find significant analyzing-power values up to A
y
= 0.3. The data taken in the energy region of the excitation of the Roper resonance confirm that its dominant ππ decay channel
is N
* → Nσ.
European Physical Journal A 04/2012; 37(3):267-277. · 2.19 Impact Factor
-
The COSY-TOF Collaboration,
M. Abdel-Bary,
S. Abdel-Samad, K. -Th. Brinkmann,
H. Clement,
J. Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
K. Ehrhardt,
A. Erhardt, [......],
G. Y. Sun,
A. Teufel,
W. Ullrich,
G. J. Wagner,
M. Wagner,
R. Wenzel,
A. Wilms,
P. Wintz,
P. Wüstner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: A systematic study of the production of w \omega -mesons in proton-proton collisions was carried out in a kinematically complete experiment at three excess energies ( e \varepsilon = 92, 128, 173 MeV). Both protons were detected using the large-acceptance COSY-TOF spectrometer at an external beam line
at the Cooler Synchrotron COSY at Forschungszentrum Jülich. The total cross-section, angular distributions of both w \omega -mesons and protons were measured and presented in various reference frames such as the overall CMS, helicity and Jackson
frame. In addition, the orientation of the w \omega -spin and invariant-mass spectra were determined. We observe w \omega -production to take place dominantly in Ss and Sp final states at e \varepsilon = 92, 128 MeV and, additionally, in Sd at e \varepsilon = 173 MeV. No obvious indication of resonant w \omega -production via N*-resonances was found, as proton angular distributions are almost isotropic and invariant-mass spectra are compatible with
phase space distributions. A dominant role of 3
P
1 and 1
S
0 initial partial waves for w \omega -production was concluded from the orientation of the decay plane of the w \omega -meson. Although the Jackson angle distributions in the w \omega p-Jackson frame are anisotropic we argue that this is not an indication of a resonance but rather a kinematical effect reflecting
the anisotropy of the w \omega angular distribution. The helicity angle distribution in the w \omega p-helicity frame shows an anisotropy which probably reflects effects of the w \omega angular momenta in the final state; this observable may be, in addition to the orientation of the w \omega decay plane, the most sensitive one to judge the validity of theoretical descriptions of the production process.
European Physical Journal A 04/2012; 44(1):7-22. · 2.19 Impact Factor
-
COSY-TOF Collaboration: M. Abdel-Bary,
S. Abdel-Samad, K-Th. Brinkmann,
H. Clement,
J. Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
K. Ehrhardt,
A. Erhardt,
W. Eyrich, [......],
A. Teufel,
W. Ullrich,
G. J. Wagner,
M. Wagner,
R. Wenzel,
A. Wilms,
P. Wintz,
S. Wirthand,
P. Wüstner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: This paper reports results from a study of the reaction pp->pK0\Sigma+ at
beam momenta of p_{beam} = 2950, 3059, and 3200 MeV/c (excess energies of
\epsilon= 126, 161, and 206 MeV). Total cross sections were determined for all
energies; a set of differential cross sections (Dalitz plots; invariant mass
spectra of all two-body subsystems; angular distributions of all final state
particles; distributions in helicity and Jackson frames) are presented for
\epsilon= 161 MeV. The total cross sections are proportional to the volume of
available three-body phase-space indicating that the transition matrix element
does not change significantly in this range of excess energies. It is concluded
from the differential data that the reaction proceeds dominantly via the
N(1710)P_{11} and/or N(1720)P_{13} resonance(s); N(1650)S_{11} and
\Delta(1600)P_{33} could also contribute.
02/2012;
-
The COSY-TOF Collaboration: M. Abdel-Bary,
S. Abdel-Samad, K. -Th. Brinkmann,
H. Clement,
J Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
K. Ehrhardt,
A Erhardt,
W Eyrich, [......],
A Teufel,
W. Ullrich,
G. J. Wagner,
M Wagner,
R. Wenzel,
A. Wilms,
P. Wintz,
S Wirth,
P. Wüstner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: This paper reports results on simultaneous measurements of the reaction channels pp -> pK+\Lambda and pp -> pK+\Sigma^0 at excess energies of 204, 239, and 284 MeV (\Lambda) and 127, 162, and 207 MeV (\Sigma^0). Total and differential cross sections are given for both reactions. It is concluded from the measured total cross sections that the high energy limit of the cross section ratio is almost reached at an excess energy of only about 200 MeV. From the differential distributions observed in the overall CMS as well as in the Jackson and helicity frames, a significant contribution of interfering nucleon resonances to the \Lambda production mechanism is concluded while resonant \Sigma^0-production seems to be of lesser importance and takes place only through specific partial waves of the entrance channel. The data also indicate that kaon exchange plays a minor role in the case of \Lambda- but an important role for \Sigma^0-production. Thus the peculiar energy dependence of the \Lambda-to-\Sigma^0 cross section ratio appears in a new light as its explanation requires more than mere differences between the p\Lambda and the p\Sigma^0 final state interaction. The data provide a benchmark for theoretical models already available or yet to come. Comment: 18 pages, 10 figures; accepted by The European Physical Journal A (EPJ A)
08/2010;
-
COSY-TOF Collaboration: M. Abdel-Bary,
S. Abdel-Samad, K. -Th. Brinkmann,
H. Clement,
J Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
K. Ehrhardt,
A Erhardt,
W Eyrich, [......],
G. Y. Sun,
A Teufel,
W. Ullrich,
G. J. Wagner,
M Wagner,
R. Wenzel,
A. Wilms,
P. Wintz,
P. Wüstner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: A systematic study of the production of omega-mesons in proton-proton-collisions was carried out in a kinematically complete experiment at three excess energies(epsilon= 92, 128, 173MeV). Both protons were detected using the large-acceptance COSY-TOF spectrometer at an external beam line at the Cooler Synchrotron COSY at Forschungszentrum J\"ulich. The total cross section, angular distributions of both omega-mesons and protons were measured and presented in various reference frames such as the overall CMS, helicity and Jackson frame. In addition, the orientation of the omega-spin and invariant mass spectra were determined. We observe omega-production to take place dominantly in Ss and Sp final states at epsilon = 92, 128 MeV and, additionally, in Sd at epsilon= 173 MeV. No obvious indication of resonant omega-production via N^*-resonances was found, as proton angular distributions are almost isotropic and invariant mass spectra are compatible with phase space distributions. A dominant role of ^3P_1 and ^1S_0 initial partial waves for omega-production was concluded from the orientation of the decay plane of the omega-meson. Although the Jackson angle distributions in the omega-p-Jackson frame are anisotropic we argue that this is not an indication of a resonance but rather a kinematical effect reflecting the anisotropy of the omega angular distribution. The helicity angle distribution in the omega-p-helicity frame shows an anisotropy which probably reflects effects of the omega angular momenta in the final state; this observable may be, in addition to the orientation of the omega decay plane, the most sensitive one to judge the validity of theoretical descriptions of the production process. Comment: 17 pages, 16 figures, accepted for publication in EPJA
01/2010;
-
S. Abd El-Samad,
R. Bilger, K. -Th. Brinkmann,
H. Clement,
M. Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
K. Ehrhardt,
A Erhardt,
W Eyrich, [......],
W Schroeder,
F. Stinzing,
G. Y. Sun,
J. Waechter,
G. J. Wagner M. Wagner,
U. Weidlich,
A. Wilms,
S Wirth,
G. Zhang,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Data accumulated recently for the exclusive measurement of the $pp\to pp\pi^+\pi^-$ reaction at a beam energy of 0.793 GeV using the COSY-TOF spectrometer have been analyzed with respect to possible events from the $pp \to nn\pi^+\pi^+$ reaction channel. The latter is expected to be the only $\pi\pi$ production channel, which contains no major contributions from resonance excitation close to threshold and hence should be a good testing ground for chiral dynamics in the $\pi\pi$ production process. No single event has been found, which meets all conditions for being a candidate for the $pp \to nn \pi^+\pi^+$ reaction. This gives an upper limit for the cross section of 0.16 $\mu$b (90% C.L.), which is more than an order of magnitude smaller than the cross sections of the other two-pion production channels at the same incident energy.
06/2009;
-
The COSY-TOF Collaboration,
S. Abd El-Samad,
R. Bilger, K. -Th. Brinkmann,
H. Clement,
M. Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
K. Ehrhardt,
A. Erhardt, [......],
F. Stinzing,
G. Y. Sun,
J. Wächter,
G. J. Wagner,
M. Wagner,
U. Weidlich,
A. Wilms,
S. Wirth,
G. Zhang,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The single-pion production reactions pp
® \rightarrow
d
p+ \pi^{+}_{} , pp
® \rightarrow
np
p+ \pi^{+}_{} and pp
® \rightarrow
pp
p0 \pi^{0}_{} were measured at a beam momentum of 0.95GeV/c ( T
p
» \approx 400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification,
energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts.
Thus all pion production channels were recorded with 1-4 overconstraints. The main emphasis is put on the presentation and
discussion of the np
p+ \pi^{+}_{} channel, since the results on the other channels have already been published previously. The total and differential cross-sections
obtained are compared to theoretical calculations. In contrast to the pp
p0 \pi^{0}_{} channel we observe in the np
p+ \pi^{+}_{} channel a strong influence of the D \Delta excitation. In particular, the pion angular distribution exhibits a (3 cos2
Q \Theta + 1) -dependence, typical for a pure s -channel D \Delta excitation and identical to that observed in the d
p+ \pi^{+}_{} channel. Since the latter is understood by a s -channel resonance in the 1
D
2
pn partial wave, we discuss an analogous scenario for the pn
p+ \pi^{+}_{} channel.
European Physical Journal A 02/2009; 39(3):281-289. · 2.19 Impact Factor
-
The COSY-TOF Collaboration,
M. Abdel-Bary, K. -Th. Brinkmann,
H. Clement,
E. Doroshkevich,
S. Dshemuchadse,
A. Erhardt,
W. Eyrich,
H. Freiesleben,
A. Gillitzer, [......],
E. Roderburg,
W. Schroeder,
M. Schulte-Wissermann,
Th. Sefzick,
A. Teufel,
A. Ucar,
W. Ullrich,
P. Wintz,
P. Wüstner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The quasifree reaction
np® ppp-np\rightarrow pp\ensuremath{\pi^{-}}
was studied in a kinematically complete experiment by bombarding a liquid-hydrogen target with a deuteron beam of momentum
1.85GeV/c and analyzing the data along the lines of the spectator model. In addition to the three charged ejectiles the spectator proton
was also detected in the large-acceptance time-of-flight spectrometer COSY-TOF. It was identified by its momentum and flight
direction thus yielding access to the Fermi motion of the bound neutron and to the effective neutron 4-momentum vector
\mathbb P \mathbb {P}
n which differed from event to event. A range of almost 90MeV excess energy above threshold was covered. Energy-dependent angular
distributions, invariant-mass spectra as well as fully covered Dalitz plots were deduced. Sizeable pp FSI effects were found as were contributions of p and d partial waves. In comparison with existing literature data the results provide a sensitive test of the spectator model. The
behavior of the elementary cross-section σ01 close to threshold is discussed in view of new cross-section data.
European Physical Journal A 03/2008; 36(1):7-16. · 2.19 Impact Factor
-
The COSY-TOF collaboration,
M. Abdel-Bary,
S. Abdel-Samad, K. -Th. Brinkmann,
H. Clement,
J Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
K. Ehrhardt,
A Erhardt, [......],
M. Schulte-Wissermann,
M Steinke,
G. J. Sun,
W. Ullrich,
R. Wenzel,
P. Wintz,
M Wagner,
A. Wilms,
S Wirth,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The reaction $ pp\to pp\bf \omega$ was investigated with the TOF spectrometer, which is an external experiment at the accelerator COSY (Forschungszentrum J\"ulich, Germany). Total as well as differential cross sections were determined at an excess energy of $93 MeV$ ($p_{beam}=2950 MeV/c$). Using the total cross section of $(9.0\pm 0.7 \pm1.1) \mu b$ for the reaction $ pp\to pp\omega$ determined here and existing data for the reaction $pp\to pp\bf \phi$, the ratio $\mathcal{R}_{\phi/\omega}=\sigma_\phi/\sigma_\omega$ turns out to be significantly larger than expected by the Okubo-Zweig-Iizuka (OZI) rule. The uncertainty of this ratio is considerably smaller than in previous determinations. The differential distributions show that the $\omega$ production is still dominated by S-wave production at this excess energy, however higher partial waves clearly contribute. A comparison of the measured angular distributions for $\omega$ production to published distributions for $\phi$ production at $83 MeV$ shows that the data are consistent with an identical production mechanism for both vector mesons.
03/2007;
-
COSY-TOF collaboration,
M. Abdel-Bary,
S. Abdel-Samad, K. -Th. Brinkmann,
R. Castelijns,
H. Clement,
J Dietrich,
S. Dshemuchadse,
E. Dorochkevitch,
W Eyrich, [......],
M. Schulte-Wissermann,
W Schroeder,
T. Sefzick,
A Teufel,
A. Ucar,
W. Ullrich,
R. Wenzel,
P. Wintz,
P. Wuestner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The pp -> p K0 Sigma+ reaction was investigated with the TOF spectrometer at COSY at 3.059 GeV/c incident beam momentum. The main objective was to clarify whether or not a narrow exotic S = +1 resnance, the Theta+ pentaquark, is populated at 1.53 GeV/c2 in the K0 p subsystem with a data sample of much higher statistical significance compared to the previously reported data in this channel. An analysis of these data does not confirm the existence of the Theta+ pentaquark. This is expressed as an upper limit for the cross section sigma (pp -> p K0 Sigma+) < 0.15 microbarn at the 95 percent confidence level.
01/2007;
-
The COSY-TOF Collaboration,
M. Abdel-Bary, K. -Th. Brinkmann,
H. Clement,
E. Doroshkevich,
S. Dshemuchadse,
A. Erhardt,
W. Eyrich,
H. Freiesleben,
A. Gillitzer, [......],
W. Schroeder,
M. Schulte-Wissermann,
G. Y. Sun,
A. Teufel,
A. Ucar,
G. J. Wagner,
M. Wagner,
P. Wintz,
P. Wüstner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The reaction
dp ® ppp p-dp \ensuremath \rightarrow ppp \pi^-
has been studied in a kinematically complete experiment at a single beam momentum
pd=1.85\ensuremath p_{d}=1.85
GeV/c (T = 759MeV). All four ejectiles have been detected in the large-acceptance time-of-flight spectrometer COSY-TOF. We analyzed
the data along the lines of the spectator model as a means to isolate the quasi-free
np® ppp-\ensuremath np\rightarrow pp\pi^-
reaction. The spectator proton was identified by its momentum and flight direction thus yielding access to the associated
Fermi motion of the bound neutron. A comparison is carried out with Monte Carlo simulations based on two different parameterizations
of the deuteron wave function. Up to a Fermi momentum of roughly 150MeV/c no significant deviations between experimental and simulated data of various observables were found from which we conclude
that the deuteron can indeed be taken as a valid substitute for the neutron.
European Physical Journal A 08/2006; 29(3):353-361. · 2.19 Impact Factor
-
The COSY-TOF Collaboration,
S. Abd El-Samad,
R. Bilger, K. -Th. Brinkmann,
H. Clement,
M. Dietrich,
E. Doroshkevich,
S. Dshemuchadse,
A. Erhardt,
W. Eyrich, [......],
F. Stinzing,
G. Y. Sun,
J. Wächter,
G. J. Wagner,
M. Wagner,
U. Weidlich,
A. Wilms,
S. Wirth,
G. Zhang,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The single-pion production reactions pp → dπ+, pp → npπ+ and pp → ppπ0 were measured at a beam momentum of 0.95GeV/c ( T
p ≈ 400MeV) using the short version of the COSY-TOF spectrometer. The implementation of a central calorimeter provided particle
identification, energy determination and neutron detection in addition to time-of-flight and angle measurements. Thus, all
pion production channels were recorded with 1-4 overconstraints. The total and differential cross-sections obtained are compared
to previous data and theoretical calculations. Main emphasis is put on the discussion of the ppπ0 channel, where we obtain angular distributions different from previous experimental results, however, partly in good agreement
with recent phenomenological and theoretical predictions. In particular, we observe very large anisotropies for the π0 angular distributions in the kinematical region of small relative proton momenta revealing there a dominance of proton spinflip
transitions associated with π0
s and d partial waves and emphasizing the important role of π0
d-waves.
European Physical Journal A 01/2006; 30(2):443-453. · 2.19 Impact Factor
-
M. Abdel-Bary,
S. Abdel-Samad, K. -Th. Brinkmann,
H. Clement,
E. Doroshkevich,
M. Drochner,
S. Dshemuchadse,
A Erhardt,
W Eyrich,
D Filges, [......],
F. Stinzing,
G. Y. Sun,
A Teufel,
A. Ucar,
G. J. Wagner,
M. Wagnerc,
A. Wilms,
P. Wintz,
St. Wirth,
P. Wuestner
[show abstract]
[hide abstract]
ABSTRACT: The hadronic reaction pp --> Sigma+ K0 p was measured exclusively at a beam momentum of 2.95 GeV/c using the TOF detector at the COSY storage ring. A narrow peak was observed in the invariant mass spectrum of the K0 p subsystem at 1530 +- 5 MeV/c2 with a significance of 4 - 6 standard deviations, depending on background assumptions. The upper limit of 18 +- 4 MeV/c2 (FWHM) for its width is given by the experimental resolution. The corresponding total cross section is estimated to be about 0.4 +- 0.1(stat) +- 0.1(syst) microbarn. Since a resonance in this subsystem must have strangeness S = + 1 we claim it to be the Theta+ state for which very recently evidence was found in various experiments.
04/2004;
-
The COSY-TOF Collaboration,
M. Abdel-Bary,
S. Abdel-Samad,
R. Bilger, K.-Th. Brinkmann,
H. Clement,
S. Dshemuchadse,
E. Dorochkevitch,
H. Dutz,
W. Eyrich, [......],
W. Schroeder,
T. Sefzick,
F. Stinzing,
G.Y. Sun,
G.J. Wagner,
M. Wagner,
A. Wilms,
P. Wintz,
S. Wirth,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The reaction pp → ppη was measured at excess energies of 15 and 41 MeV at an external target of the Jülich Cooler Synchrotron COSY with the time-of-flight
spectrometer. About 25000 events were measured for the excess energy of 15 MeV and about 8000 for 41 MeV. Both protons of
the process ppη were detected with an acceptance of nearly 100% and the η was reconstructed by the missing-mass technique. For both excess
energies the angular distributions are found to be nearly isotropic. In the invariant-mass distributions strong deviations
from the pure phase space distributions are seen.
European Physical Journal A 12/2002; 16(1):127-137. · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The partition of excitation energy between fragments from reactions of 8 A MeV116Sn with48Ti was studied. The experimental setup rendered possible the unambiguous identification of primary fragments up to total excitation energies of 50 MeV. Neutron mulitplicities of both projectile-like and target-like fragments were experimentally determined as a function of excitation energy. Comparison of these quantities with the results of numerical calculations of sequential decay including rotation of the fragments allowed the determination of excitation energy partition and the associated fluctuations.
Zeitschrift für Physik A Hadrons and Nuclei 02/1992; 343(1):59-65.
-
[show abstract]
[hide abstract]
ABSTRACT: A plastic scintillator array of total area for the detection of neutrons in medium-energy nucleon–nucleon reactions was constructed and built. Calibration procedures for the detector were developed which allow the monitoring of gain shifts by means of muons from the cosmic radiation. Experiments were performed in order to calibrate the efficiency simulations and study the performance of the detector using the d+t→α+n reaction at neutron energy and proton-induced deuteron breakup at .
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 460:362-367. · 1.21 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Elastic and inelastic scattering of 575 MeV 36Ar on 208Pb to low-lying states of both target and projectile nucleus were studied. The measured cross sections were analyzed with coupled-channels calculations. A very satisfying description of the data was obtained by using B(EL) values from the literature and proper optical potential parameters. The latter were used as basis to estimate the cross sections for the excitation of the isovector giant dipole and isoscalar giant quadrupole resonances.
Phys. Rev. C. 42(1).
