26 research outputs found
Backward single-pion production in the reaction with WASA-at-COSY
New data on the production of single neutral pions in the
reaction are presented. For fifteen
proton beam momenta between and
, differential cross sections are determined over a
large fraction of the backward hemisphere. Since the only previous systematic
measurements of single-pion production at these energies were made in collinear
kinematics, the present work constitutes a significant extension of the current
knowledge on this reaction. Even this far above the production threshold,
significant changes are found in the behaviour of the angular distributions
over small intervals in beam momentum.Comment: 9 pages, 5 figures, 3 tables submitted to EPJ
Isotensor Dibaryon in the pp →ppπ+π- Reaction?
Exclusive measurements of the quasifree pp→ppπ+π- reaction have been carried out at WASA@COSY by means of pd collisions at Tp=1.2 GeV. Total and differential cross sections have been extracted covering the energy region Tp=1.08-1.36 GeV, which is the region of N∗(1440) and Δ(1232)Δ(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor ΔN dibaryon resonance with I(JP)=2(1+) produced associatedly with a pion is able to overcome these deficiencies
Search for C violation in the decay η → π0e+e− with WASA-at-COSY
We report on the search for the rare decay η→π0e+e− which is of interest to study C violation in the electromagnetic interaction which would indicate contributions from physics beyond the Standard Model, since the allowed decay via a two-photon intermediate state is strongly suppressed. The experiment has been performed using the WASA-at-COSY installation, located at the COSY accelerator of the Forschungszentrum Jülich, Germany. In total 3×107 events of the reaction pd→3Heη have been recorded at an excess energy of Q=59.8MeV. Based on this data set the C parity violating decay η→π0γ⁎→π0e+e− via a single-photon intermediate state has been searched for, resulting in new upper limits of Γ(η→π0e+e−)/Γ(η→π+π−π0)<3.28×10−5 and Γ(η→π0e+e−)/Γ(η→all)<7.5×10−6 (CL=90%), respectively
Total and differential cross sections of η-production in proton–deuteron fusion for excess energies between Qη = 13 MeV and Qη = 81 MeV
New data on both total and differential cross sections of the production of η mesons in proton–deuteron fusion to He3η in the excess energy region 13.6MeV≤Qη≤80.9MeV are presented. These data have been obtained with the WASA-at-COSY detector setup located at the Forschungszentrum Jülich, using a proton beam at 15 different beam momenta between pp=1.60GeV/c and pp=1.74GeV/c. While significant structure of the total cross section is observed in the energy region 20MeV≲Qη≲60MeV, a previously reported sharp variation around Qη≈50MeV cannot be confirmed. Angular distributions show the typical forward-peaking that was noted earlier. For the first time, it is possible to study the development of these angular distributions with rising excess energy over a wide interval
Measurement of the _np → dπ0π0 reaction with polarized beam in the region of the d*(2380) resonance
We report on a high-statistics measurement of the most basic double-pionic fusion reaction _np 2192 dπ0π0 over the energy region of the d*(2380) resonance by use of a polarized deuteron beam and observing the double fusion reaction in the quasifree scattering mode. The measurements were performed with the WASA detector setup at COSY. The data reveal substantial analyzing powers and confirm conclusions about the d* resonance obtained from unpolarized measurements. We also confirm the previous unpolarized data obtained under complementary kinematic conditions
Determination of the COSY Proton Beam Polarization Using the WASA Detector
The dynamics of η-meson production and the interaction of η mesons with nucleons can be studied using the ⃗p p → ppη reaction via measurements of the analyzing power Ay. To this end, we have performed a measurement of the ⃗p p → ppη reaction using the WASA-at-COSY detector, which provides large acceptance and is φ-symmetric. The experiment was carried out for the beam momenta of 2026 MeV/c and 2188 MeV/c. In this article, we present a method and results for the determination of the degree of the beam polarization
Determination of the analysing power for the See Formula in PDF → ppη reaction using the WASA-at-COSY detector system
High statistics measurements of the analyzing power for the
See Formula in PDF
→ ppη reaction were performed with the WASA-at-COSY detector at the Cooler Synchrotron COSY. The η meson was produced at two excess energies: Q = 15 MeV and Q = 72 MeV, and it was registered using the missing and invariant mass techniques. The determined analyzing power is consistent with zero for Q = 15 MeV implying the dominance of s wave and an insignificant contribution of the S d partial wave. However, at Q = 72 MeV the angular distribution of the analyzing power reveals a strong interference of Ps and Pp partial waves. Moreover, the available theoretical predictions for the angular dependence of the analyzing power strongly deviate from our experimental results
円管内流れにおけるパフ発生の初期過程 (組織的渦構造 : その乱流力学における役割 )
Various theoretical calculations based on QCD or hadronic interactions predict that in addition to the recently observed dibaryon resonance d*(2380) with I(J(P)) = 3(0(+)) there should also exist a dibaryon resonance with mirrored quantum numbers I(J(P)) = 3(0(+)). We report here on a search for such a NN-decoupled state in data on the pp -> pp pi(+) pi(+) pi(-) pi(-) reaction. Since no clear-cut evidence has been found, we give upper limits for the production cross section of such a resonance in the mass range 2280-2500 MeV