Total cross sections for the
pp→
ppη′ reaction have been measured in the excess energy range from
Q=1.53 MeV to
Q=23.64 MeV. The experiment has been performed at the internal installation COSY-11
1 ...using a stochastically cooled proton beam of the COoler SYnchrotron COSY
2 and a hydrogen cluster target
3, 4. The determined energy dependence of the total cross section weakens the hypothesis of the S-wave repulsive interaction between the
η′ meson and the proton
5, 6. New data agree well with predictions based on the phase-space distribution modified by the proton-proton final-state-interaction (FSI) only.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The production of
η mesons has been measured in the proton-proton interaction close to the reaction threshold using the COSY-11 internal facility at the cooler synchrotron COSY. Total cross sections ...were determined for eight different excess energies (
ϵ) in the range from
ϵ=0.5 MeV to
ϵ=5.4 MeV. The energy dependence of the total cross section is well described by the available phase–space volume weighted by FSI factors for the proton–proton and proton–
η pairs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Two-pion production reactions in proton–proton collisions have been studied using the PROMICE/ WASA detector and an internal cluster gas-jet target at the CELSIUS storage ring in Uppsala. The total ...cross sections for the
pp→ppπ
+π
−
,
pp→ppπ
0π
0
and the
pp→pnπ
0π
+
reactions are presented at beam energies ranging from 650 to 775 MeV. An isospin analysis of the amplitudes involved in these three reactions indicates that the excitation of the
N
∗(1440)
followed by direct two pion emission can be the most important amplitude when allowed. However, large contributions from other production mechanisms must also be prevalent to explain the large
pp→pnπ
0π
+
cross section. The data are compared to an extensive model including non-resonant as well as resonant production via
N
∗
and
Δ excitation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Exclusive and kinematically complete high-statistics measurements of quasifree polarized np scattering have been performed in the energy region of the narrow resonancelike structure d* with I(JP) = ...0(3 super(+)), M approximately 2380 MeV, and Gamma approximately 70 MeV observed recently in the double-pionic fusion channels pn arrow right dpi super(0)pi super(0) and pn arrow right dpi super(+)pi super(-). The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process dp arrow right np + p sub(spectator). This allowed the np analyzing power, A sub(y) to be measured over a broad angular range. The obtained A sub(y)angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new A sub(y)data into the SAID analysis produces a pole in the super(3)D sub(3) - super(3)G sub(3) waves in support of the d* resonance hypothesis.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
We observe a deuteron beam polarization lifetime near 1000 s in the horizontal plane of a magnetic storage ring (COSY). This long spin coherence time is maintained through a combination of beam ...bunching, electron cooling, sextupole field corrections, and the suppression of collective effects through beam current limits. This record lifetime is required for a storage ring search for an intrinsic electric dipole moment on the deuteron at a statistical sensitivity level approaching 10^{-29} e cm.
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Drift chamber with a c-shaped frame Smyrski, J.; Kolf, Ch; Adam, H.-H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2005, Volume:
541, Issue:
3
Journal Article
Peer reviewed
Open access
We present the construction of a planar drift chamber with wires stretched between two arms of a c-shaped aluminum frame. The special shape of the frame allows to extend the momentum acceptance of ...the COSY-11 detection system towards lower momenta without suppressing the high-momentum particles. The proposed design allows for construction of tracking detectors covering small angles with respect to the beam, which can be installed and removed without dismounting the beam-pipe. For a three-dimensional track reconstruction a computer code was developed using a simple algorithm of hit pre-selection.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The near threshold total cross section and angular distributions of K+K− pair production via the reaction pp→ppK+K− have been studied at an excess energy of Q=17 MeV using the COSY-11 facility at the ...cooler synchrotron COSY. The obtained cross section as well as an upper limit at an excess energy of Q=3 MeV represent the first measurements on the K+K− production in the region of small excess energies where production via the channel pp→ppΦ →ppK+K− is energetically forbidden. The possible influence of a resonant production via intermediate scalar states f0(980) and a0(980) is discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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