-
S. Dymov,
V. Shmakova,
T. Azaryan,
S. Barsov,
V. Baru,
P. Benati,
D. Chiladze,
A. Dzyuba,
R. Engels,
M. Gaisser, [......],
S. Trusov,
D. Tsirkov,
Yu. Uzikov,
Yu. Valdau,
Ch. Weidemann,
C. Wilkin,
P. Wüstner,
Q. J. Ye,
M. Zhabitsky,
for the ANKE Collaboration
[show abstract]
[hide abstract]
ABSTRACT: The transverse spin correlations A_{x,x} and A_{y,y} have been measured in
the pol{d} pol{p} -> p_spec {pp}_s pi- reaction at COSY-ANKE at 353 MeV per
nucleon. Here {pp}_s denotes a proton-proton pair with low excitation energy,
which is dominantly in the 1S0 state. By measuring three protons in the final
state it was possible to extract events where there was a spectator proton
p_spec so that the reaction could be interpreted in terms of quasi-free pol{n}
pol{p} -> {pp}_s pi-. The proton analyzing power in this reaction was also
deduced from this data set by averaging over the polarization of the deuteron
beam. The values of A_y^p were shown to be consistent with a refined analysis
of our earlier results obtained with a polarized proton incident on a deuterium
target. Taking these data in combination with our earlier measurements of the
differential cross sections and analyzing powers in the pol{p} p -> {pp}_s pi^0
reaction, a more robust partial wave decomposition was achieved. Three
different acceptable solutions were found and the only way of resolving this
ambiguity without further theoretical input would be through a measurement of
the mixed spin-correlation parameter A_{x,z}.
04/2013;
-
Q. J. Ye,
M. Hartmann,
D. Chiladze,
S. Dymov,
A. Dzyuba,
H. Gao,
R. Gebel,
V. Hejny,
A. Kacharava,
B. Lorentz, [......],
H. Ohm,
M. Papenbrock,
A. Polyanskiy,
V. Serdyuk, H. J. Stein,
H. Stroeher,
S. Trusov,
Yu. Valdau,
C. Wilkin,
P. Wuestner
[show abstract]
[hide abstract]
ABSTRACT: The pp -> ppK+K- reaction was measured below the phi threshold at a beam
energy of 2.568 GeV using the COSY-ANKE magnetic spectrometer. By assuming that
the four-body phase space is distorted only by the product of two-body final
state interactions, fits to a variety of one-dimensional distributions permit
the evaluation of differential and total cross sections. The shapes of the
distributions in the Kp and Kpp invariant masses are reproduced only if the K-p
interaction is even stronger than that found at higher energy. The cusp effect
in the K+K- distribution at the K0K0bar threshold is much more clear and some
evidence is also found for coupling between the K-p and K0bar n channels.
However, the energy dependence of the total cross section cannot be reproduced
by considering only a simple product of such pair-wise final state
interactions.
02/2013;
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D. Mchedlishvili,
S. Barsov,
J. Carbonell,
D. Chiladze,
S. Dymov,
A. Dzyuba,
R. Engels,
R. Gebel,
V. Glagolev,
K. Grigoryev, [......],
H. Seyfarth, H. J. Stein,
E. Steffens,
H. Stockhorst,
H. Stroeher,
M. Tabidze,
S. Trusov,
Yu. Uzikov,
Yu. Valdau,
C. Wilkin
[show abstract]
[hide abstract]
ABSTRACT: The unpolarised differential cross section and the two deuteron tensor
analysing powers A_{xx} and A_{yy} of the pol{d}p -> (pp)n charge-exchange
reaction have been measured with the ANKE spectrometer at the COSY storage
ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were
obtained for small momentum transfers to a (pp) system with low excitation
energy. The results at the three lower energies are consistent with impulse
approximation predictions based upon the current knowledge of the
neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far
more uncertain, agreement requires a reduction in the overall double-spin-flip
contribution, with an especially significant effect in the longitudinal
direction. These conclusions are supported by measurements of the
deuteron-proton spin-correlation parameters C_{x,x} and C_{y,y} that were
carried out in the pol{d}pol{p} -> (pp)n reaction at 1.2 and 2.27GeV. The
values obtained for the proton analysing power also suggest the need for a
radical re-evaluation of the neutron-proton elastic scattering amplitudes at
the higher energy. It is therefore clear that such measurements can provide a
valuable addition to the neutron-proton database in the charge-exchange region.
12/2012;
-
Q. J. Ye,
M. Hartmann,
Y. Maeda,
S. Barsov,
M. Buescher,
D. Chiladze,
S. Dymov,
A. Dzyuba,
H. Gao,
R. Gebel, [......],
H. Ohm,
E. Ya. Paryev,
A. Polyanskiy,
V. Serdyuk, H. J. Stein,
H. Stroeher,
S. Trusov,
Yu. Valdau,
C. Wilkin,
P. Wuestner
[show abstract]
[hide abstract]
ABSTRACT: Differential and total cross sections for the pp -> ppK+K- reaction have been
measured at a proton beam energy of 2.83 GeV using the COSY-ANKE magnetic
spectrometer. Detailed model descriptions fitted to a variety of
one-dimensional distributions permit the separation of the pp -> pp phi cross
section from that of non-phi production. The differential spectra show that
higher partial waves represent the majority of the pp -> pp phi total cross
section at an excess energy of 76 MeV, whose energy dependence would then seem
to require some s-wave phi-p enhancement near threshold. The non-phi data can
be described in terms of the combined effects of two-body final state
interactions using the same effective scattering parameters determined from
lower energy data.
02/2012;
-
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;
-
[show abstract]
[hide abstract]
ABSTRACT: At COSY, electron cooling is used after stripping injection of H- or D- ions
in order to prepare phase-space-dense ion beams before acceleration to a
requested energy. The electron-cooled beam has been successfully applied for
specific external experiments. The achievable beam intensity is limited by
instabilities during the cooling process. Besides initial losses after
injection, as long as the beam has still large emittances, the self-excitation
of coherent betatron oscillations is the dominating beam loss mechanism.
Perspectives for possible improvements are briefly addressed.
01/2011;
-
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;
-
S. Dymov,
V. Komarov,
G. Macharashvili,
Yu. Uzikov,
T. Azarian,
O. Imambekov,
A. Kulikov,
V. Kurbatov,
S. Merzliakov,
B. Zalikhanov, [......],
A. Khoukaz,
T. Mersmann,
T. Rausmann,
S. Barsov,
S. Mikirtychiants,
B. Kämpfer,
P. Kulessa,
M. Nioradze,
S. Trusov,
S. Yaschenko
[show abstract]
[hide abstract]
ABSTRACT: The deuteron breakup reaction pd→{pp}sn, where {pp}s is a fast proton pair emitted in forward direction with small excitation energy Epp<3 MeV, has been studied at proton beam energies of 0.5–2.0 GeV using the ANKE spectrometer at COSY-Jülich. The differential c.m. cross sections are measured in complete kinematics and provide angular distributions of the neutron emission angle in the range θn=168°–180°, the dependence on beam energy at θn=180°, angular distributions of the direction of the proton in the pp rest frame, and distributions of the excitation energy Epp of the proton pair. The obtained data are analyzed on the basis of theoretical models previously developed for the pd→dp process in a similar kinematics and properly modified for the diproton channel in pd→{pp}sn. It is shown that the measured observables are highly sensitive to the short-range part of the nucleon-nucleon interaction.
Phys. Rev. C. 04/2010; 81(4).
-
P. Goslawski,
A. Khoukaz,
R. Gebel,
M Hartmann,
A. Kacharava,
A. Lehrach,
B. Lorentz,
R. Maier,
M. Mielke,
M. Papenbrock,
D. Prasuhn,
R. Stassen, H. J. Stein,
H. Stockhorst,
H. Ströher,
C. Wilkin
[show abstract]
[hide abstract]
ABSTRACT: In order to measure the mass of the eta meson with high accuracy using the d+p -> 3He+eta reaction, the momentum of the circulating deuteron beam in the Cooler Synchrotron COSY of the Forschungszentrum Juelich has to be determined with unprecedented precision. This has been achieved by studying the spin dynamics of the polarized deuteron beam. By depolarizing the beam through the use of an artificially induced spin resonance, it was possible to evaluate its momentum p with a precision of dp/p < 10-4 for a momentum of roughly 3 GeV/c. Different possible sources of error in the application of the spin resonance method are discussed in detail and its possible use during a standard experiment is considered. Comment: 10 pages, 6 figures, 2 tables, published version
08/2009;
-
C. Barschel,
U. Bechstedt,
J Dietrich,
N. Dolfus,
R. Engels,
R. Gebel,
H. Hadamek,
J. Haidenbauer,
C. Hanhart,
A. Kacharava, [......],
K. Rathsman,
P. -E. Tegner,
P. Thoerngren Engblom,
R. De Leo,
G. Tagliente,
B. Kaempfer,
S. Trusov,
N. Buttimore,
H.O. Meyer,
for the PAX Collaboration
[show abstract]
[hide abstract]
ABSTRACT: We propose to use an internal polarized hydrogen storage cell gas target in the AD ring to determine for the first time the two total spin-dependent pbar-p cross sections sigma_1 and sigma_2 at antiproton beam energies in the range from 50 to 450 MeV. The data obtained are of interest by themselves for the general theory of pbar-p interactions since they will provide a first experimental constraint of the spin-spin dependence of the nucleon-antinucleon potential in the energy range of interest. In addition, measurements of the polarization buildup of stored antiprotons are required to define the optimum parameters of a future, dedicated Antiproton Polarizer Ring (APR), intended to feed a double-polarized asymmetric pbar-p collider with polarized antiprotons. Such a machine has recently been proposed by the PAX collaboration for the new Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, Germany. The availability of an intense stored beam of polarized antiprotons will provide access to a wealth of single- and double-spin observables, thereby opening a new window on QCD spin physics.
05/2009;
-
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;
-
D. Oellers,
L. Barion,
S. Barsov,
U. Bechstedt,
P. Benati,
S. Bertelli,
D. Chiladze,
G. Ciullo,
M. Contalbrigo,
P.F. Dalpiaz, [......],
M. Tabidze,
G. Tagliente,
P. Thörngren Engblom,
S. Trusov,
A. Vasilyev,
Chr. Weidemann,
D. Welsch,
P. Wieder,
P. Wüstner,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: We discuss polarizing a proton beam in a storage ring, either by selective removal or by spin flip of the stored ions. Prompted by recent, conflicting calculations, we have carried out a measurement of the spin-flip cross section in low-energy electron–proton scattering. The experiment uses the cooling electron beam at COSY as an electron target. The measured cross sections are too small for making spin flip a viable tool in polarizing a stored beam. This invalidates a recent proposal to use co-moving polarized positrons to polarize a stored antiproton beam.
Physics Letters B. 02/2009;
-
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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K. Grigoryev,
F. Rathmann,
R. Engels,
A. Kacharava,
F. Klehr,
B. Lorentz,
M. Mikirtytchiants,
D. Prasuhn,
J. Sarkadi,
H. Seyfarth, H. J. Stein,
H. Ströher,
A. Vasilyev
[show abstract]
[hide abstract]
ABSTRACT: In this paper, we describe a study to determine the transverse profiles of the COSY beam at the target interaction point at ANKE. The vertical and horizontal proton beam profiles were measured at injection energy (45 MeV), and after acceleration on flattop (2.65 GeV). The machine acceptance at 2.65 GeV was determined as well. The information is required to determine the dimensions of a storage cell for the double-polarized experiments with the polarized internal gas target at the ANKE spectrometer. The study resulted in a first storage cell with dimensions of 15mm x 20mm x 390mm (vertical x horizontal x longitudinal), which will provide luminosities of about 2.5*10^29 cm^-2*s^-1 with beams of 10^10 particles stored in COSY.
06/2008;
-
H. J. Stein,
M Hartmann,
I. Keshelashvili,
Y Maeda,
C. Wilkin,
S. Dymov,
A. Kacharava,
A. Khoukaz,
B. Lorentz,
R. Maier,
T. Mersmann,
S. Mikirtychiants,
D. Prasuhn,
R. Stassen,
H. Stockhorst,
H. Ströher,
Yu. Valdau,
P. Wüstner
[show abstract]
[hide abstract]
ABSTRACT: The repeated passage of a coasting ion beam of a storage ring through a thin target induces a shift in the revolution frequency due to the energy loss in the target. Since the frequency shift is proportional to the beam-target overlap, its measurement offers the possibility of determining the target thickness and hence the corresponding luminosity in an experiment. This effect has been investigated with an internal proton beam of energy 2.65 GeV at the COSY-J\"ulich accelerator using the ANKE spectrometer and a hydrogen cluster-jet target. Possible sources of error, especially those arising from the influence of residual gas in the ring, were carefully studied, resulting in a accuracy of better than 5%. The luminosity determined in this way was used, in conjunction with measurements in the ANKE forward detector, to determine the cross section for elastic proton-proton scattering. The result is compared to published data as well as to the predictions of a phase shift solution. The practicability and the limitations of the energy-loss method are discussed.
02/2008;
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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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T Mersmann,
A Khoukaz,
M Büscher,
D Chiladze,
S Dymov,
M Hartmann,
V Hejny,
A Kacharava,
I Keshelashvili,
P Kulessa, [......],
F Rathmann,
T Rausmann,
R Schleichert,
V Serdyuk, H-J Stein,
H Ströher,
A Täschner,
Yu Valdau,
C Wilkin,
A Wrońska
[show abstract]
[hide abstract]
ABSTRACT: The differential and total cross sections for the dp--> 3Heeta reaction have been measured in a high precision high statistics COSY-ANKE experiment near threshold using a continuous beam energy ramp up to an excess energy Q of 11.3 MeV with essentially 100% acceptance. The kinematics allowed the mean value of Q to be determined to about 9 keV. Evidence is found for the effects of higher partial waves for Q >or= 4 MeV. The very rapid rise of the total cross section to its maximum value within 0.5 MeV of threshold implies a very large eta3He scattering length and hence the presence of a quasibound state extremely close to threshold.
Physical Review Letters 06/2007; 98(24):242301. · 7.37 Impact Factor
-
T Mersmann,
A Khoukaz,
M Büscher,
D Chiladze,
S Dymov,
M Hartmann,
V Hejny,
A Kacharava,
I Keshelashvili,
P Kulessa, [......],
F Rathmann,
T Rausmann,
R Schleichert,
V Serdyuk, H.-J Stein,
H Ströher,
A Täschner,
Yu Valdau,
C Wilkin,
A Wroska
[show abstract]
[hide abstract]
ABSTRACT: The differential and total cross sections for the dp → 3 He η reaction have been measured in a high precision high statistics COSY–ANKE experiment near threshold using a continuous beam energy ramp up to an excess energy Q of 11.3 MeV with essentially 100% acceptance. The kinematics allowed the mean value of Q to be determined to about 9 keV. Evidence is found for the effects of higher partial waves for Q 4 MeV. The very rapid rise of the total cross section to its maximum value within 0.5 MeV of threshold implies a very large η 3 He scattering length and hence the presence of a quasi–bound state extremely close to threshold.
03/2007;
-
T. Mersmann,
A. Khoukaz,
M. Büscher,
D. Chiladze,
S. Dymov,
M Hartmann,
V. Hejny,
A. Kacharava,
I. Keshelashvili,
P. Kulessa, [......],
F. Rathmann,
T. Rausmann,
R. Schleichert,
V. Serdyuk, H. J. Stein,
H. Ströher,
A. Täschner,
Yu. Valdau,
C. Wilkin,
A. Wrońska
[show abstract]
[hide abstract]
ABSTRACT: The differential and total cross sections for the d+p->3He+eta reaction have been measured in a high precision high statistics COSY-ANKE experiment near threshold using a continuous beam energy ramp up to an excess energy Q of 11.3 MeV with essentially 100% acceptance. The kinematics allowed the mean value of Q to be determined to about 9 keV. Evidence is found for the effects of higher partial waves for Q>4 MeV. The very rapid rise of the total cross section to its maximum value within 0.5 MeV of threshold implies a very large eta-3He scattering length and hence the presence of a quasi-bound state extremely close to threshold.
03/2007;
-
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
