-
M. Röder,
E. Borodina,
H. Clement,
E. Doroshkevich,
R. Dzhygadlo,
K. Ehrhardt,
A. Erhardt,
W. Eyrich,
W. Gast,
A. Gillitzer, [......], K. Kilian,
M. Krapp,
M. Mertens,
J. Ritman,
E. Roderburg,
W. Schroeder,
T. Sefzick,
A. Sibirtsev,
P. Wintz,
P. Wüstner
[show abstract]
[hide abstract]
ABSTRACT: The possibility to determine the pLambda scattering length from the
final-state interaction in the reaction pp->pKLambda is investigated
experimentally. From a transversely polarized measurement, the K analyzing
power (A_N) which, in principle, allows one to extract the spin triplet
scattering length is studied. An unexpected energy dependence of the
forward/backward symmetric part of A_N is found. The influence of N*-resonances
on the pLambda invariant mass spectrum is investigated by exploiting the large
acceptance for the process pp->pKLambda->pKppi and is found to be the main
source of uncertainty for determining the pLambda scattering length.
05/2013;
-
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
-
H Machner,
M Betigeri,
J Bojowald,
A Budzanowski,
A Chatterjee,
J Ernst,
L Freindl,
D Frekers,
W Garske,
K Grewer, [......],
D Protić,
B Razen,
P Von Rossen,
BJ Roy,
R Siudak,
J Smyrski,
RV Srikantiah,
A Strzałkowski,
R Tsenov,
K Zwoll
[show abstract]
[hide abstract]
ABSTRACT: Total and differential cross sections for the reactions p + d → 3He + m
0 with m=π, η and p + d → 3H+π+ were measured with the GEM detector at COSY for beam momenta between threshold and the maximum of the corresponding baryon
resonance. For both reactions a strong forward-backward asymmetry was found. The data were compared with model calculations.
The aspect of isospin symmetry breaking is studied.
Pramana 04/2012; 57(2):399-416. · 0.57 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;
-
[show abstract]
[hide abstract]
ABSTRACT: For producing polarized antiproton beams the so called spin filter method is normally discussed. The method has been proven by the FILTEX collaboration with a proton beam and detailed studies are presently performed by the PAX collaboration at COSY. A well known source for polarized antiprotons is the antilambda decay. It was used in the only experiment with polarized antiprotons so far at FERMILAB. Furthermore the antiproton production process itself, if showing polarization, would be by far the simplest and best way to get polarized beams because one could use the existing antiproton facility. Up to now production has never been investigated in detail.
Journal of Physics Conference Series 06/2011; 295(1):012171.
-
A. Budzanowski,
A. Chatterjee,
H. Clement,
P. Hawranek,
F. Hinterberger,
R Jahn,
R Joosten, K. Kilian,
Da. Kirillov,
Di. Kirillov, [......],
J. Ritman,
P. von Rossen,
J. Roy,
A. Sibirtsev,
I. Sitnik,
R. Siudak,
R. Tsenov,
K. Ulbrich,
J. Urban,
G. J. Wagner
[show abstract]
[hide abstract]
ABSTRACT: The reaction pp -> K^+ + (Lambda p) has been measured at T_p = 1.953 GeV and
\Theta = 0 deg with a high missing mass resolution in order to study the Lambda
p final state interaction. Narrow S = -1 resonances predicted by bag model
calculations are not visible in the missing mass spectrum. Small structures
observed in a previous experiment are not confirmed. Upper limits for the
production cross section of a narrow resonance are deduced for missing masses
between 2058 and 2105 MeV/c^2.
05/2011;
-
A. Budzanowski,
A. Chatterjee,
P. Hawranek,
R. Jahn,
V. Jha, K. Kilian,
S. Kliczewski,
Da. Kirillov,
Di. Kirillov,
D. Kolev, [......],
N. Piskunov,
D. Protić,
J. Ritman,
P. von Rossen,
B. J. Roy,
I. Sitnik,
R. Siudak,
R. Tsenov,
J. Urban,
G. Vankova
[show abstract]
[hide abstract]
ABSTRACT: The cross section for the reaction $p+^6\text{Li}\to\eta+^7\text{Be}$ was
measured at an excess energy of 11.28 MeV above threshold by detecting the
recoiling $^7$Be nuclei. A dedicated set of focal plane detectors was built for
the magnetic spectrograph Big Karl and was used for identification and four
momentum measurement of the $^7$Be. A differential cross section of
$\frac{d\sigma}{d\Omega}=(0.69\pm{0.20}\text{(stat.)}\pm
0.20\text{(syst.)})\text{nb/sr}$ for the ground state plus the 1/2$^-$ was
measured. The result is compared to model calculations.
10/2010;
-
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;
-
A. Budzanowski,
A. Chatterjee,
H. Clement,
E. Dorochkevitch,
P. Hawranek,
F. Hinterberger,
R Jahn,
R Joosten, K. Kilian,
S. Kliczewski, [......],
D. Protic,
J. Ritman,
P. von Rossen,
A. Sibirtsev,
I. Sitnik,
R. Siudak,
R. Tsenov,
K. Ulbrich,
J. Urban,
G. J. Wagner
[show abstract]
[hide abstract]
ABSTRACT: We have measured inclusive data on $K^+$-meson production in $pp$ collisions at COSY J\"ulich close to the hyperon production threshold and determined the hyperon-nucleon invariant mass spectra. The spectra were decomposed into three parts: $\Lambda p$, $\Sigma^0p$ and $\Sigma^+n$. The cross section for the $\Sigma^+n$ channel was found to be much smaller than a previous measurement in that excess energy region. The data together with previous results at higher energies are compatible with a phase space dependence. Comment: accepted by Phys. lett. B some typos corrected
07/2010;
-
COSY-TOF Collaboration: S. AbdEl-Samad,
M. Abdel-Bary,
K. Brinkmann,
H. Clement,
J Dietrich,
E. Dorochkevitch,
S. Dshemuchadse,
K. Ehrhardt,
A Erhardt,
W Eyrich, [......],
W. Ullrich,
J. Waechter,
G. J. Wagner,
M Wagner,
R. Wenzel,
A. Wilms,
P. Wintz,
S Wirth,
P. Wuestner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Hyperon production in the threshold region was studied in the reaction pp -> K+Lp using the time-of-flight spectrometer COSY-TOF. Exclusive data, covering the full phase-space, were taken at the three different beam momenta of p_beam=2.95, 3.20 and 3.30 GeV/c, corresponding to excess energies of epsilon=204, 285 and 316 MeV, respectively. Total cross-sections were deduced for the three beam momenta to be 23.9+/-0.8 +/-2.0 ub, 28.4+/-1.3 +/-2.2 ub and 35.0+/-1.3 +/-3.0 ub. Differential observables including Dalitz plots were obtained. The analysis of the Dalitz plots reveals a strong influence of the N(1650)-resonance at p_beam=2.95 GeV/c, whereas for the higher momenta an increasing relative contribution of the N(1710)- and/or of the N(1720)-resonance was observed. In addition, the pL-final-state interaction turned out to have a significant influence on the Dalitz plot distribution. Comment: accepted for publication at Physics Letters B; some minor text changes were done; also the scale of the ordinates of figure 9 has been changed;
03/2010;
-
A. Budzanowski,
A. Chatterjee,
H. Clement,
E. Dorochkevitch,
P. Hawranek,
F. Hinterberger,
R Jahn,
R Joosten, K. Kilian,
S. Kliczewski, [......],
J. Ritman,
P. von Rossen,
B. J. Roy,
A. Sibirtsev,
I. Sitnik,
R. Siudak,
R. Tsenov,
K. Ulbrich,
J. Urban,
G. J. Wagner
[show abstract]
[hide abstract]
ABSTRACT: The reaction pp -> K+ + (Lambda p) was measured at Tp=1.953 GeV and Theta = 0 deg with a high missing mass resolution in order to study the Lambda p final state interaction. The large final state enhancement near the Lambda p threshold can be described using the standard Jost-function approach. The singlet and triplet scattering lengths and effective ranges are deduced by fitting simultaneously the Lambda p invariant mass spectrum and the total cross section data of the free Lambda p scattering. Comment: submitted to Physics Letters B, 10 pages, 3 figures
03/2010;
-
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;
-
The HIRES Collaboration,
A. Budzanowski,
A. Chatterjee,
H. Clement,
E. Dorochkevitch,
P. Hawranek,
F. Hinterberger,
R Jahn,
R Joosten, K. Kilian, [......],
J. Ritman,
P. von Rossen,
B. J. Roy,
A. Sibirtsev,
I. Sitnik,
R. Siudak,
R. Tsenov,
K. Ulbrich,
J. Urban,
G. J. Wagner
11/2009;
-
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;
-
A. Budzanowski,
A. Chatterjee,
P. Hawranek,
R Jahn,
V. Jha, K. Kilian,
Da. Kirillov,
Di. Kirillov,
S. Kliczewski,
D Kolev, [......],
J. Ritman,
P. von Rossen,
B. J. Roy,
I. Sitnik,
R. Siudak,
H. J. Stein,
R. Tsenov,
J. Urban,
G. Vankova,
C. Wilkin
[show abstract]
[hide abstract]
ABSTRACT: Inclusive measurements of pion production in proton--proton collisions in the forward direction were undertaken at 400 and 600 MeV at COSY using the Big Karl spectrograph. The high resolution in the $\pi^+$ momentum ensured that there was an unambiguous separation of the $pp\to {\pi}^+d/\pi^+pn$ channels. Using these and earlier data, the ratio of the production cross sections could be followed through the $\Delta$ region and compared with the predictions of final state interaction theory. Deviations are strongly influenced by long-range terms in the production operator and the tensor force in the final $pn$ system. These have been investigated in a realistic $pp\to\pi^+d/\pi^+pn$ calculation that includes $S \rightleftharpoons D$ channel coupling between the final nucleons. A semi-quantitative understanding of the observed effects is achieved. Comment: 10 pages, 3 figures
04/2009;
-
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
-
P. Moskal,
R. Czyżykiewicz,
H.-H. Adam,
S. D. Bass,
A. Budzanowski,
E. Czerwiński,
D. Gil,
D. Grzonka,
M. Janusz,
L. Jarczyk, [......],
T. Sefzick,
M. Siemaszko,
M. Silarski,
J. Smyrski,
A. Täschner,
M. Wolke,
P. Wüstner,
M. Zieliński,
W. Zipper,
J. Zdebik
[show abstract]
[hide abstract]
ABSTRACT: Total cross sections for the quasifree pn→pnη reaction in the range from the kinematical threshold up to 20 MeV excess energy have been determined. At threshold they exceed corresponding cross sections for the pp→ppη reaction by a factor of about 3 in contrast to the factor of 6 established for higher excess energies. To large extent, the observed decrease of the ratio σ(pn→pnη)/σ(pp→ppη) toward threshold may be assigned to the different energy dependence of the proton-proton and proton-neutron final-state interactions. The experiment was conducted using a proton beam of the cooler synchrotron COSY and a cluster jet deuteron target. The proton-neutron reactions were tagged by the spectator proton whose momentum was measured for each event. Protons and neutron outgoing from the pn→pnη reaction have been registered by means of the COSY-11 facility, an apparatus dedicated for threshold meson production.
Phys. Rev. C. 01/2009; 79(1).
