First results on
-dependence measurements in inclusive
meson production in
interactions (
, Al, Cu, Sn, and W) are presented at
GeV/
c
. The ratios of the differential cross sections of four of these ...nuclei to the differential cross section on aluminum were measured and the dependence of these cross sections on the atomic of the nucleus was studied. The measurements were carried out in the kinematic region of the Feynman variable
and transverse momentum
GeV/
c
.
mesons were detected in the decay mode
at the SPASCHARM experimental setup using negative charged beams at beamline 14 of the U-70 accelerator complex.
One of the main sources of the information about nuclear resonances are partial wave analyses (PWA) of pion-proton elastic scattering. Nearly all of the data available for PWA were obtained more than ...20 years ago with old measurement techniques. The talk presents new high precision data obtained recently by the EPECUR collaboration. The experiment features high statistics and better than 1 MeV resolution in the invariant mass thus allowing searches for narrow resonances with the coupling to the πp channel as low as 5%. The experimental setup consists of a 25 cm long liquid hydrogen target in a non-magnetic spectrometer of wire drift chambers with hexagonal structure. The measurements started in 2009. 3 billions of triggers are already collected with positive and negative pion beams in the beam momentum range 820-1330 MeV/c.
The reaction γp→pπ0η has been studied with the CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for incident photon energies from threshold up to 3.1 GeV. This paper has been ...motivated by the recently claimed observation of a narrow structure in the MNη invariant mass distribution at a mass of 1678MeV/c2. The existence of this structure cannot be confirmed in the present work. Instead, for Eγ = 1400–1500 MeV and the cut Mpπ0≤1190MeV/c2 a statistically significant structure in the Mpη invariant mass distribution near 1700 MeV/c2 is observed with a width of Γ≈35MeV/c2 while the mass resolution is σres = 5 MeV/c2. Increasing the incident photon energy from 1420 to 1540 MeV this structure shifts in mass from ≈ 1700 MeV/c2 to ≈ 1725 MeV/c2; the width increases to about 50 MeV/c2 and decreases thereafter. The cross section associated with this structure reaches a maximum of ≈ 100 nb around Eγ≈ 1490 MeV (W ≈ 1920 MeV), which coincides with the pa0 threshold. Three scenarios are discussed which might be the origin of this structure in the Mpη invariant mass distribution. The most likely interpretation is that it is due to a triangular singularity in the γp→pa0→pπ0η reaction.
The reaction
γ
p
→
p
π
0
η
has been studied with the CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for incident photon energies from threshold up to 3.1 GeV. This paper has ...been motivated by the recently claimed observation of a narrow structure in the
M
N
η
invariant mass distribution at a mass of
1678
MeV
/
c
2
. The existence of this structure cannot be confirmed in the present work. Instead, for
E
γ
= 1400–1500 MeV and the cut
M
p
π
0
≤
1190
MeV
/
c
2
a statistically significant structure in the
M
p
η
invariant mass distribution near 1700
MeV
/
c
2
is observed with a width of
Γ
≈
35
MeV
/
c
2
while the mass resolution is
σ
res
= 5
MeV
/
c
2
. Increasing the incident photon energy from 1420 to 1540 MeV this structure shifts in mass from
≈
1700
MeV
/
c
2
to
≈
1725
MeV
/
c
2
; the width increases to about 50
MeV
/
c
2
and decreases thereafter. The cross section associated with this structure reaches a maximum of
≈
100 nb around
E
γ
≈
1490 MeV (W
≈
1920 MeV), which coincides with the
p
a
0
threshold. Three scenarios are discussed which might be the origin of this structure in the
M
p
η
invariant mass distribution. The most likely interpretation is that it is due to a triangular singularity in the
γ
p
→
p
a
0
→
p
π
0
η
reaction.
The EPECUR collaboration presents new high precision data on the pion-proton elastic scattering in the second resonance region. The experiment EPECUR is placed on the universal beam channel of the ...accelerator ITEP. The setup features 0.1% beam pion momentum tagging system, 25 cm long liquid hydrogen target, placed in mylar container and beryllium outer shell, low material wire drift chambers and high performance DAQ. More than 3 billions of triggers have been collected. The data cover pion beam momentum range 0.8 - 1.3 GeV/c and 40-120 degrees center-of-mass scattering angle range for both positive and negative pions. The measured differential cross section has 2% statistical accuracy in 2 degrees angle and 5 MeV/c momentum intervals.
The ITEP-PNPI collaboration presents new results of the measurements of the spin rotation parameter A in the elastic scattering of negative pions on protons at Pbeam = 1.43 GeV/c. The results are ...compared to the predictions of the different partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow.
The ITEP-PNPI collaboration presents new results of the measurements of the spin rotation parameter A in the elastic scattering of negative pions on protons at Pbeam = 1.43 GeV/c. The results are ...compared to the predictions of several partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow.
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