-
X. Yuan,
M. Büscher,
D. Chiladze,
S. Dymov,
A. Dzyuba,
V. Yu. Grishina,
C. Hanhart,
M. Hartmann,
A. Kacharava,
A. Khoukaz, [......],
P. Kulessa,
M. Mielke,
S. Mikirtychiants,
M. Nekipelov,
M. Papenbrock,
K. Pysz,
V. Serdyuk,
H. Ströher,
C. Wilkin,
H. Xu
[show abstract]
[hide abstract]
ABSTRACT: The total cross-section for the dd
® \rightarrow 4HeK
+
K
- reaction has been measured at a beam momentum of 3.7GeV/c, corresponding to an excess energy of 39MeV, which is the maximum possible at the Cooler Synchrotron COSY-Jülich. A deuterium
cluster-jet target and the ANKE forward magnetic spectrometer, placed inside the storage ring, have been employed in this
investigation. We find a total cross-section of stot \sigma_{{{\rm tot}}}^{} < 14 pb, which brings into question the viability of investigating the dd
® \rightarrow 4Hea
0(980) reaction as a means of studying isospin violation.
European Physical Journal A 04/2012; 42(1):1-6. · 2.19 Impact Factor
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M. Hartmann,
Yu. T. Kiselev,
A. Polyanskiy,
E. Ya. Paryev,
M. Buescher,
D. Chiladze,
S. Dymov,
A. Dzyuba,
R. Gebel,
V. Hejny, [......],
V. Serdyuk,
A. Sibirtsev,
V. Y. Sinitsyna,
H. J. Stein,
H. Stroeher,
S. Trusov,
Yu. Valdau,
C. Wilkin,
P. Wuestner,
Q. J. Ye
[show abstract]
[hide abstract]
ABSTRACT: The production of phi mesons in proton collisions with C, Cu, Ag, and Au
targets has been studied via the phi -> K+K- decay at an incident beam energy
of 2.83 GeV using the ANKE detector system at COSY. For the first time, the
momentum dependence of the nuclear transparency ratio, the in-medium phi width,
and the differential cross section for phi meson production at forward angles
have been determined for these targets over the momentum range of 0.6 - 1.6
GeV/c. There are indications of a significant momentum dependence in the value
of the extracted phi width, which corresponds to an effective phi-N absorption
cross section in the range of 14 - 21 mb.
01/2012;
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Yu. Valdau, V. Koptev,
S. Barsov,
M. Buescher,
A. Dzyuba,
M Hartmann,
A. Kacharava,
I. Keshelashvili,
A. Khoukaz,
S. Mikirtychiants,
M. Nekipelov,
A. Polyanskiy,
F. Rathmann,
H. Stroeher,
Yu. N. Uzikov,
C. Wilkin
[show abstract]
[hide abstract]
ABSTRACT: The momentum spectra of K+ produced at small angles in proton-proton and
proton-deuteron collisions have been measured at four beam energies, 1.826,
1.920, 2.020, and 2.650 GeV, using the ANKE spectrometer at COSY-Juelich. After
making corrections for Fermi motion and shadowing, the data indicate that K+
production near threshold is stronger in pp- than in pn-induced reactions.
However, most of this difference could be made up by the unobserved K0
production in the pn case.
09/2011;
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A. Polyanskiy,
M Hartmann,
Yu. T. Kiselev,
E. Ya. Paryev,
M. Buescher,
D. Chiladze,
S. Dymov,
A. Dzyuba,
R. Gebel,
V. Hejny, [......],
H. Ohm,
H. Schade,
V. Serdyuk,
A. Sibirtsev,
H. J. Stein,
H. Stroeher,
S. Trusov,
Yu. Valdau,
C. Wilkin,
P. Wuestner
[show abstract]
[hide abstract]
ABSTRACT: The production of phi mesons in the collisions of 2.83 GeV protons with C,
Cu, Ag, and Au at forward angles has been measured via the phi -> K+K- decay
using the COSY-ANKE magnetic spectrometer. The phi meson production cross
section follows a target mass dependence of A^0.56+/-0.02 in the momentum
region of 0.6-1.6 GeV/c. The comparison of the data with model calculations
suggests that the in-medium phi width is about an order of magnitude larger
than its free value.
08/2010;
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Yu. Valdau,
S. Barsov,
M. Büscher,
D. Chiladze,
S. Dymov,
A. Dzyuba,
M Hartmann,
A. Kacharava,
I. Keshelashvili,
A. Khoukaz, [......],
M. Mielke,
S. Mikirtychiants,
M. Nekipelov,
H. Ohm,
M. Papenbrock,
F. Rathmann,
V. Serdyuk,
H. Ströher,
S. Trusov,
C. Wilkin
[show abstract]
[hide abstract]
ABSTRACT: The production of the Sigma+ hyperon through the pp->K+nSigma+ reaction has been investigated at four energies close to threshold, 1.826, 1.920, 1.958, and 2.020 GeV. At low energies, correlated K+pi+ pairs can only originate from Sigma+ production so that their measurement allows the total cross section for the reaction to be determined. The results obtained are completely consistent with the values extracted from the study of the K+-proton correlation spectra obtained in the same experiment. These spectra, as well as the inclusive K+ momentum distributions, also provide conservative upper limits on the Sigma+ production rates. The measurements show a Sigma+ production cross section that varies roughly like phase space and, in particular, none of the three experimental approaches used supports the anomalously high near-threshold pp->K+ nSigma+ total cross section previously reported [T. Rozek et al., Phys. Lett. B 643, 251 (2006)]. Comment: Submitted to PRC
02/2010;
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Y Maeda,
M Hartmann,
I. Keshelashvili,
S. Barsov,
M. Buescher,
A. Dzyuba,
S. Dymov,
V. Hejny,
A. Kacharava,
V. Kleber, [......],
S. Mikirtytchiants,
A. Mussgiller,
M. Nekipelov,
H. Ohm,
K. Pysz,
H. J. Stein,
H. Stroeher,
Yu. Valdau,
C. Wilkin,
P. Wuestner
[show abstract]
[hide abstract]
ABSTRACT: Measurements of the pn -> p_spec dK^+K^- reaction, where p_spec is a spectator proton, have been undertaken at the Cooler Synchrotron COSY-Juelich by detecting a fast deuteron in coincidence with a K^+K^- pair in the ANKE facility. Although the proton beam energy was fixed, the moving target neutron allowed values of the non-resonant quasi-free pn -> dK^+K^- total cross section to be deduced up to an excess energy epsilon ~ 100 MeV. Evidence is found for the effects of K^-d and KKbar final state interactions. The comparison of these data with those of pp -> ppK^+K^- and pp -> dK^+Kbar shows that all the total cross sections are very similar in magnitude.
12/2008;
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[show abstract]
[hide abstract]
ABSTRACT: A combined analysis of the published data on the pp -> dK+K0bar reaction at excess energies of 47.4 MeV and 104.7 MeV is presented. Evidence is found for both the production of the a0+(980)scalar resonance and for a strong K0bar:d final state interaction.
05/2008;
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Y Maeda,
M Hartmann,
I. Keshelashvili,
S. Barsov,
M. Büscher,
M. Drochner,
A. Dzyuba,
V. Hejny,
A. Kacharava,
V. Kleber, [......],
A. Mussgiller,
M. Nekipelov,
H. Ohm,
D. Prasuhn,
R. Schleichert,
H. J. Stein,
H. Ströher,
Yu. Valdau,
C. Wilkin,
P. Wüstner
[show abstract]
[hide abstract]
ABSTRACT: The differential and total cross sections for kaon pair production in the pp->ppK+K- reaction have been measured at three beam energies of 2.65, 2.70, and 2.83 GeV using the ANKE magnetic spectrometer at the COSY-Juelich accelerator. These near-threshold data are separated into pairs arising from the decay of the phi-meson and the remainder. For the non-phi selection, the ratio of the differential cross sections in terms of the K-p and K+p invariant masses is strongly peaked towards low masses. This effect can be described quantitatively by using a simple ansatz for the K-p final state interaction, where it is seen that the data are sensitive to the magnitude of an effective K-p scattering length. When allowance is made for a small number of phi events where the K- rescatters from the proton, the phi region is equally well described at all three energies. A very similar phenomenon is discovered in the ratio of the cross sections as functions of the K-pp and K+pp invariant masses and the identical final state interaction model is also very successful here. The world data on the energy dependence of the non-phi total cross section is also reproduced, except possibly for the results closest to threshold.
11/2007;
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I. Zychor,
M. Büscher,
M Hartmann,
A. Kacharava,
I. Keshelashvili,
A. Khoukaz,
V. Kleber, V. Koptev,
Y Maeda,
T. Mersmann,
S. Mikirtychiants,
R. Schleichert,
H. Ströher,
Y. Valdau,
C. Wilkin
[show abstract]
[hide abstract]
ABSTRACT: The pp -> p K+ Y0 reaction has been studied for hyperon masses m(Y0)<1540 MeV/c2 at COSY-Juelich by using a 3.65 GeV/c circulating proton beam incident on an internal hydrogen target. Final states comprising two protons, one positively charged kaon and one negatively charged pion have been identified with the ANKE spectrometer. Such configurations are sensitive to the production of the ground state Lambda and Sigma0 hyperons as well as the Sigma0(1385) and Lambda(1405) resonances. Applying invariant- and missing-mass techniques, the two overlapping excited states could be well separated, though with limited statistics. The shape and position of the Lambda(1405) distribution, reconstructed cleanly in the Sigma0 pion0 channel, are similar to those found from other decay modes and there is no obvious mass shift. This finding constitutes a challenging test for models that predict Lambda(1405) to be a two-state resonance.
06/2007;
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Yu. Valdau, V. Koptev,
S. Barsov,
M. Büscher,
S. Dymov,
M Hartmann,
A. Kacharava,
S. Merzliakov,
S. Mikirtychyants,
A. Mussgiller,
M. Nekipelov,
R. Schleichert,
H. Ströher,
C. Wilkin
[show abstract]
[hide abstract]
ABSTRACT: Inclusive K+ production in proton-proton collisions has been measured at a beam energy of 2.16 GeV using the COSY-ANKE magnetic spectrometer. The resulting spectrum, as well as those corresponding to K+ p and K+ pi+ correlated pairs, can all be well described using consistent values of the total cross sections for the pp->K+ p Lambda, pp->K+ p Sigma0, and pp->K+ n Sigma+ reactions. While the resulting values for Lambda and Sigma0 production are in good agreement with world data, our value for the total Sigma+ production cross section, sigma(pp->K+ n Sigma+) = 2.5+/-0.6(stat)+/-0.4(syst) mkb at an excess energy of epsilon=129 MeV, could only be reconciled with other recently published data if there were a highly unusual near--threshold behaviour.
04/2007;
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M Nekipelov,
M Büscher,
M Hartmann,
I Keshelashvili,
V Kleber, V Koptev,
Y Maeda,
S Mikirtychiants,
R Schleichert,
A Sibirtsev,
H Ströher,
Yu Valdau
[show abstract]
[hide abstract]
ABSTRACT: The reaction pp → pK0π+Λ has been studied with the ANKE spectrometer at COSY-Jülich at a beam momentum of 3.65 GeV/c in order to search for a possible signal of the pentaquark Θ+(1540), decaying into the pK0 system. By detecting four charged particles in the final state (π+, π− and two protons), the K0 and the Λ have been reconstructed to tag strangeness production. It has been found that the π+Λ missing-mass spectrum displays no significant signal expected from the Θ+(1540) excitation. The total cross section for the reaction pp → pK0π+Λ has been deduced, as well as an upper limit for the Θ+ production cross section. The intermediate Δ++K0Λ state seems to provide a significant contribution to the reaction.
Journal of Physics G Nuclear and Particle Physics 03/2007; 34(4):627. · 4.18 Impact Factor
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M. Nekipelov,
M. Buescher,
M Hartmann,
I. Keshelashvili,
V. Kleber, V. Koptev,
Y Maeda,
S. Mikirtychiants,
R. Schleichert,
A. Sibirtsev,
H. Stroeher,
Yu. Valdau
[show abstract]
[hide abstract]
ABSTRACT: The reaction pp->p K0 pi+ Lambda has been studied with the ANKE spectrometer at COSY-Juelich at a beam momentum of 3.65 GeV/c in order to search for a possible signal of the pentaquark Theta+(1540), decaying into the p K0 system. By detecting four charged particles in the final state, the K0 and the Lambda have been reconstructed to tag strangeness production. It has been found that the pi+ Lambda missing-mass spectrum displays no significant signal expected from the Theta+(1540) excitation. The total cross section for the reaction pp->p K0 pi+ Lambda has been deduced, as well as an upper limit for the Theta+ production cross section. The intermediate Delta++ K0 Lambda state is found to provide a significant contribution to the reaction.
11/2006;
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S. Barsov,
M. Büscher,
M Hartmann,
V. Hejny,
A. Kacharava,
I. Keshelashvili,
A. Khoukaz, V. Koptev,
P. Kulessa,
A. Kulikov, [......],
H. Ohm,
F. Rathmann,
R. Schleichert,
H. Seyfarth,
H. Ströher,
S. Trusov,
Y. Valdau,
P. Wüstner,
S. Yaschenko,
C. Wilkin
[show abstract]
[hide abstract]
ABSTRACT: The production of omega-mesons in the pp->pp omega reaction has been investigated with the COSY-ANKE spectrometer for excess energies of 60 and 92MeV by detecting the two final protons and reconstructing their missing mass. The large multipion background was subtracted using an event-by-event transformation of the proton momenta between the two energies. Differential distributions and total cross sections were obtained after careful studies of possible systematic uncertainties in the overall ANKE acceptance. The results are compared with the predictions of theoretical models. Combined with data on the phi-meson, a more refined estimate is made of the Okubo-Zweig-Iizuka rule violation in the phi/omega production ratio.
10/2006;
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Y Maeda,
M Hartmann,
I Keshelashvili,
S Barsov,
M Büscher,
A Dzyuba,
S Dymov,
V Hejny,
A Kacharava,
V Kleber, [......],
A Mussgiller,
M Nekipelov,
H Ohm,
R Schleichert,
H J Stein,
H Ströher,
Yu Valdau,
K H Watzlawik,
C Wilkin,
P Wüstner
[show abstract]
[hide abstract]
ABSTRACT: The quasifree pn-->dvarphi reaction has been studied at the Cooler Synchrotron COSY-Jülich, using the internal proton beam incident on a deuterium cluster-jet target and detecting a fast deuteron in coincidence with the K+K- decay of the varphi meson. The energy dependence of the total and differential cross sections are extracted for excess energies up to 80 MeV by determining the Fermi momentum of the target neutron on an event-by-event basis. Though these cross sections are consistent with s-wave production, the kaon angular distributions show the presence of p waves at quite a low energy. Production on the neutron is found to be stronger than on the proton but not by as much as for the eta meson.
Physical Review Letters 10/2006; 97(14):142301. · 7.37 Impact Factor
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M Hartmann,
Y Maeda,
I Keshelashvili,
S Barsov,
W Borgs,
M Büscher,
V I Dimitrov,
S Dymov,
A Dzyuba,
V Hejny, [......],
M Nioradze,
H Ohm,
K Pysz,
R Schleichert,
H J Stein,
H Ströher,
Yu Valdau,
H Watzlawik,
C Wilkin,
P Wüstner
09/2006; 1729.
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M Büscher,
K Sistemich,
V Abaev,
U Bechstedt,
P Birien,
W Borgs,
W Cassing,
S Dienel,
H Dombrowski,
S V Dshemuchadze, [......],
Chr Schneidereit,
O W B Schult,
H Seyfarth,
V Shelkov,
J Smyrski,
A Strzalkowski,
K -H Watzlawik,
B Zh Zalyhanov,
N I Zhuravlev,
P Zolnierczuk
[show abstract]
[hide abstract]
ABSTRACT: A universal facility is in preparation for the study of particle production in proton-nucleus reactions below the nucleon-nucleon threshold. The device will be located at the internal target position TP2 at COSY-Jülich and will consist of three dipole magnets. This 0° Facility will separate ejectiles from the circulating proton beam and allow momentum and angle analysis both for positively and negatively charged particles. A major goal of the experimental program is the investigation of the K+-meson production at projectile energies below the NN threshold. The detector concept for these studies is described and also an overview over further planned experiments is given.
Physica Scripta 08/2006; 48(1):50. · 1.20 Impact Factor
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Y Maeda,
M Hartmann,
I. Keshelashvili,
S. Barsov,
M. Buescher,
A. Dzyuba,
S. Dymov,
V. Hejny,
A. Kacharava,
V. Kleber, [......],
S. Mikirtytchiants,
A. Mussgiller,
M. Nekipelov H. Ohm,
R. Schleichert,
H. J. Stein,
H. Stroeher,
Yu. Valdau,
K.-H. Watzlawik,
C. Wilkin,
P. Wuestner
[show abstract]
[hide abstract]
ABSTRACT: The quasi-free pn->dphi reaction has been studied at the Cooler Synchrotron COSY-Juelich, using the internal proton beam incident on a deuterium cluster-jet target and detecting a fast deuteron in coincidence with the K+K- decay of the phi-meson. The energy dependence of the total and differential cross sections are extracted for excess energies up to 80 MeV by determining the Fermi momentum of the target neutron on an event-by-event basis. Though these cross sections are consistent with s-wave production, the kaon angular distributions show the presence of p waves at quite low energy. Production on the neutron is found to be stronger than on the proton but not by as much as for the eta-meson.
08/2006;
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[show abstract]
[hide abstract]
ABSTRACT: In a series of measurements with the ANKE spectrometer at COSY-Jülich, the production of K+-mesons in pA (A = C, Cu, Ag and Au) collisions in a wide range of beam energies, Tp = 1.0 ... 2.3 GeV, has been investigated. Double differential cross sections d2σ/dΩdp have been evaluated. The strong suppression in the ratios of K+ production on copper, silver and gold targets to that on carbon observed for pK < 200–250 MeV/c may be ascribed to a combination of Coulomb and nuclear repulsion in the K+A system. Our data are consistent with a K+A nuclear potential of VK0 ≈ 20 MeV at low kaon momenta and normal nuclear density. First momentum spectra of protons and deuterons measured in coincidence with the K+-mesons have been obtained at Tp = 1.2 GeV. These data supply direct evidence for the two-step reaction mechanism, with formation of intermediate pions, leading to kaon production.
Physica Scripta 07/2006; 2003(T104):40. · 1.20 Impact Factor
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M Hartmann,
Y Maeda,
I Keshelashvili,
H R Koch,
S Mikirtytchiants,
S Barsov,
W Borgs,
M Büscher,
V I Dimitrov,
S Dymov, [......],
A Mussgiller,
M Nekipelov,
M Nioradze,
H Ohm,
K Pysz,
R Schleichert,
H J Stein,
H Ströher,
K-H Watzlawik,
P Wüstner
[show abstract]
[hide abstract]
ABSTRACT: The pp-->ppphi reaction has been studied at the Cooler Synchrotron COSY-Jülich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energies epsilon near the production threshold. The differential cross section closest to threshold at epsilon=18.5 MeV exhibits a clear S wave dominance as well as a noticeable effect due to the proton-proton final-state interaction. Taken together with data for ppomega production, a significant enhancement of the phi/omega ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.
Physical Review Letters 07/2006; 96(24):242301. · 7.37 Impact Factor
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A. Dzyuba,
V. Kleber,
M. Buescher,
V. P. Chernyshev,
S. Dymov,
P. Fedorets,
V. Grishina,
C. Hanhart,
M Hartmann,
V. Hejny, [......],
Y Maeda,
T. Mersmann,
S. Mikirtychyants,
M. Nekipelov,
D. Prasuhn,
R. Schleichert,
A. Sibirtsev,
H. J. Stein,
H. Stroeher,
I. Zychor
[show abstract]
[hide abstract]
ABSTRACT: The reaction pp -> d K^+ K^0-bar has been investigated at excess energies Q = 47.4 and 104.7 MeV above the K^+ K^0-bar threshold at COSY-Juelich. Coincident dK^+ pairs were detected with the ANKE spectrometer, and events with a missing K^0-bar invariant-mass subsequently identified. The joint analysis of invariant-mass and angular distributions reveals s-wave dominance between the two kaons, in conjunction with a p-wave between the deuteron and the kaon pair, i.e. K K-bar production via the a_0^+(980) channel. Integration of the differential distributions yields total cross sections of sigma(pp -> d K^+ K^0-bar) = (38 +/- 2(stat) +/- 14(syst)) nb and 190 +/- 4(stat) +/- 39(syst)) nb for the low and high Q values, respectively.
06/2006;
