ABSTRACT: New Crystal Barrel data are reported for pbar-p -> omega-eta and pbar-p ->
omega-pizero-pizero with omega decaying to piplus-piminus-pizero. The omega-eta
data confirm angular distributions obtained earlier from data where omega ->
pizero-gamma. The new omega-eta data provide accurate measurements of vector
and tensor polarisations of the omega and lead to considerable improvements in
masses and widths of s-channel resonances. A new J^PC = 3^+- I = 0 resonance is
observed with mass M = 2025+-20 MeV and width Gamma = 145+-30 MeV. Polarisation
is close to zero everywhere and tensor polarisations are large, as is the case
also for pbar-p -> omega-pizero.
ABSTRACT: New Crystal Barrel data are reported for pbar-p -> omega-pizero and pbar-p ->
omega eta-pizero with omega decaying to piplus-piminus-pizero. The shapes of
angular distributions agree well with those for data where omega ->
pizero-gamma; this is a valuable cross-check on systematic errors. The new data
provide good measurements of vector and tensor polarisations P_y, T20, T21 and
T22 of the omega. These lead to significant improvements in parameters of
several resonances reported earlier. New values of masses and widths (in Mev)
are: J^PC = 5^-- (2300+-45, 260+-75), J^PC = 3^-- (2260+-20, 160+-25), J^PC =
1^+- (2240+-35, 320+-85), and J^PC = 1^-- (2110+-35, 230+-50). A remarkable
feature of the data is that vector polarisation P_y is close to zero
everywhere. It follows that all interfering amplitudes have relative phases
close to 0 or 180 deg. Tensor polarisations are large.
ABSTRACT: Data are presented on the reaction pbar-p -> omega-omega-pizero at rest from
the Crystal Barrel detector. These data identify a strong signal due to
f2(1565) -> omega-omega. The relative production from initial pbar-p states
3P2, 3P1 and 1S0 is well determined from omega-omega decay angular
correlations; P-state annihilation dominates strongly. A combined fit is made
with data on pbar-p -> 3pizero at rest, where f2(1565) -> pizero-pizero is
ABSTRACT: Data on p¯p-->ηπ+π-
π+π- at rest show two resonant
/ρρ, (b) /η(1440)σ,
η(1440)-->ηπ+π-. The branching
>σσ]=0.98+/-0.25 in the mass range available here. Using
data on p¯p-->ηπ0π0, the ratio
f0(1370). The effects of the strongly /s-dependent width of
f0(1370) are discussed in some detail. The /η(1440) is
observed decaying to /ησ and a0(980)π, with
strong destructive interference between them. In its decay to
a0(980)π, a narrow peak appears in the /ηπ mass
spectrum, but 30-50 MeV above that usually attributed to
a0(980) and significantly above the /KK threshold. This
effect is explained naturally by a two-step process:
η(1440)-->K*(890)K followed by rescattering of the two
kaons through a0(980) to /ηπ above the /KK threshold.
Nuclear Physics A 06/2001; 690:567-594. · 1.54 Impact Factor
ABSTRACT: We discuss gamma gamma partial widths of pseudoscalar/isoscalar mesons eta(M) in the mass region M = 1000-1500 MeV. The transition amplitudes eta(1295) -> gamma gamma and eta(1440) -> gamma gamma are studied within an assumption that the decaying mesons are the members of the first radial excitation nonet 2^1S_0 q\bar q. The calculations show that partial widths being of the order of 0.1 keV are dominantly due to the n\bar n meson component while the contribution of the s\bar s component is small.
ABSTRACT: We discuss γγ partial widths of pseudoscalar/isoscalar mesons η:(M) in the mass region M∼ 1000–1500 MeV. The transition amplitudes η:(1295) →γγ and η:(1440) →γγ are studied within an assumption that the decaying
mesons are the members of the first radial excitation nonet 21
0q¯q. The calculations show that partial widths being of the order of 0.1 keV are dominantly due to the n¯n meson component
while the contribution of the s¯s component is small.
European Physical Journal A 01/1999; 6(3):247-249. · 2.19 Impact Factor
ABSTRACT: We present a measurement and partial wave analysis of the final state
KLK+/-π-/+ of p¯p annihilation
at rest in liquid hydrogen. This reaction is important for the study of
the K¯K decay mode of scalar resonances, in particular, the
isovectors a0(980) and a0(1450). The determination
of the a0(1450) production also fixes the K¯K coupling
of the isoscalar f0(1500) which is discussed as a glueball.
The mass and width of a0(1450) are m=1480+/-30
MeV/c2 and Γ=265+/-15 MeV/c2, respectively.
For a0(980) we determine the relative ratio
=0.23+/-0.05 and its relative coupling, K¯K to πη, is
Physical review D: Particles and fields 03/1998; 57:3860-3872.
Nuclear Physics A 01/1997; 625:899-900. · 1.54 Impact Factor
ABSTRACT: Crystal Barrel data on pp -> 5π0 at rest are presented.
Mass spectra for 2π0 combinations, 3π0 and
4π0 and decay angular distributions all differ
significantly from phase space. We present several ways of fitting the
data. All agree on the definite presence of the f0(1500),
observed in its 4π0 decay mode. It can decay into
ππ(1300) and into σσ where σ stands for the full
ππ S-wave amplitude.
Physics Letters B 01/1996; 380:453-460. · 3.95 Impact Factor
ABSTRACT: Data on
[`(p)]p ® hp0 p0 p0\bar pp \to \eta \pi ^0 \pi ^0 \pi ^0
taken at beam momenta of 1.2 and 1.94 GeV/c reveal evidence for twoI=0J
PC=2−+ resonances inηππ. The first, at 1645±14(stat.)±15(syst.) MeV with width 180
±25 MeV, decays toα
2(1320)π withL=0. It may be interpreted as the
2 partner ofπ
2(1670). A strong signal is also observed just above threshold inf
2(1270)η withL=0. It is 11–22 times stronger than is expected for the high mass tail of the 1645 MeV resonance. It can be fitted as a second
2−+ resonance at 1875±20±35 MeV with width 200±25±45 MeV. A third resonance havingJ
PC=2++ is observed at 2135±20±45 MeV withΛ=250±25±45 MeV, decaying to botha
2(1270)η withL=1. There is no evidence for resonances with decays toa
0(980)π, ση orf
Zeitschrift für Physik C 01/1996; 71(2):227-238.
ABSTRACT: We report the observation of nucleon resonances in the reaction pd ->
π0π0n for antiprotons stopping in liquid
deuterium. The process pd -> Δ(1232)π0 is
identified and its branching ratio determined to be (2.21 +/-
Physics Letters B 01/1995; 352:187-192. · 3.95 Impact Factor
ABSTRACT: We report the first observations of Pontecorvo reactions of the type pd Xn. We fully reconstruct the outgoing meson and, for antiprotons stopped in liquid deuterium, we measure: BR(pd0)=(7.030.72)10–6, BR(pdn)=(3.19+0.48)10–6, BR(pdn)=(22.8+4.1)10–6, BR(pdn)1410–6 (at 95% confidence level). Assuming charge independence, our result for pd0n is compatible with measurements of the only other observed Pontecorvo reaction pd –p. The experimental ratios between the above branching ratios are in fair agreement with both the statistical model and dynamical two-step models (assumingN N annihilation into two mesons, with subsequent absorption of one meson on the remaining nucleon). This agreement suggests that there may be appreciable rates for Pontecorvo reactions producing final state mesons with masses above 1 GeV.
Zeitschrift für Physik A Hadrons and Nuclei 01/1995; 351(3):325-331.
ABSTRACT: New branching ratios for
annihilation at rest into final states with a
pair or φ-meson are being measured with the Crystal Barrel detector at LEAR. The yield of φγ, relative to ωγ, appears to
violate the OZI rule as strongly as φπ relative to ωπ.
Il Nuovo Cimento A 10/1994; 107(11):2235-2242.
ABSTRACT: This is an overview of the preliminary results of
annihilation at incident
momenta of 600, 1200 and 1940 MeV/c(*). The data was taken at LEAR with the Crystal Barrel Detector (E. Aker
et al.:Nucl. Instrum. Methods A,321, 108 (1992)). In the two pseudoscalar final states seven different channels are observable and their angular distributions
are measured. They are compared to older data, if existent, and are found to be equal within the experimental errors. In the
three-meson final states, an overview of the already examined final states is given. Striking signals in the Dalitz plots
and invariant-mass projections for a set of final states are observed. In the final states ηηπ0 and ηηη a signal ηη with the invariant mass of 1480 MeV/c2 and a width of aboutΓ≈≈70 MeV/c2 is visible. In the final-state ωηπ0 a signal in the ωη invariant-mass spectrum at 1680 MeV/c2 with a widthΓ≈150 MeV/c2 is observed. Finally, in the final-state ωωπ0 two visible structures in the Dalitz plot are detected at 1600 MeV/c2 (Γ≈90 MeV/c2) and 1900 MeV/c2 (Γ≈150 MeV/c2).
Il Nuovo Cimento A 10/1994; 107(11):2305-2313.
ABSTRACT: The decay of the η-meson into three pions plays an important role as a test of low-energy QCD calculations in the framework
of chiral perturbation theory. Previous experiments show results that are inconclusive or even contradictory. The Crystal
Barrel experiment at LEAR has determined the braching ratiosΓ(η→3π0)/Γ(η→π+π−π0)=1.47±0.09±0.15 andΓ(η→γγ)/Γ(η→π+π−π0)=1.88±0.10±0.17 using its unique features to detect charged particles as well as neutral particles. The value for the first
ratio agrees nicely with the theoretical predictions and solves previous experimental uncertainties. The second value, which
yields a partial width ofΓ(η→π+π−π0)=(0.24±0.03) keV, shows that the same next-to-leading order chiral perturbation theory calculations still have some problems.
Il Nuovo Cimento A 01/1994; 107(11):2589-2594.
ABSTRACT: Antiproton-proton annihilation at rest into 3π0 is analysed based on a data sample of about 500 000 high-quality 3π0 events. In this high-statistics Dalitz plot two structures in the region of π0π0 invariant masses of about 1500 MeV show up, a small band and a blob at higher masses. In a first attempt to describe the
data two different models are used to parametrize the dynamical amplitudes leading to the same conclusion: the data require
a 0+ + and also a 2+ + resonance in the 1500 MeV region.
Il Nuovo Cimento A 01/1994; 107(11):2227-2233.
ABSTRACT: Results are presented on meson spectroscopy, two-body final states and meson decay modes observed in
annhilation at rest by the Crystal Barrel experiment at LEAR.
Il Nuovo Cimento A 01/1994; 107(10):1815-1823.
ABSTRACT: We report measurements of branching ratios for production of a series of two meson final states in
p annihilations at rest in liquid hydrogen. We find:
BR([`(p)]p ® p+ p- ) = (3.07 ±0.13) 10 - 3 BR([`(p)]p ® K+ K- ) = (0.99 ±0.05) 10 - 3 BR([`(p)]p ® p0 p0 ) = (6.93 ±0.43) 10 - 4 BR([`(p)]p ® p0 h) = (2.12 ±0.12) 10 - 4 BR([`(p)]p ® p0 w) = (5.73 ±0.47) 10 - 3 BR([`(p)]p ® p0 h¢) = (1.23 ±0.13) 10 - 4 BR([`(p)]p ® hh) = (1.64 ±0.10) 10 - 4 BR([`(p)]p ® hw) = (1.51
Zeitschrift für Physik C 05/1993; 58(2):175-189.
Nuclear Physics B - Proceedings Supplements 05/1989; 8:65-68. · 0.88 Impact Factor
ABSTRACT: We report an analysis of annihilation at rest into ϱ+ϱ−π0 leading to the final state π+π−3π0. A strong signal is observed for a scalar resonance with mass 1374 ± 38 MeV/c2 and width 375 ± 61 MeV/c2, decaying to ϱ+ϱ−. The resonance in ϱ+ϱ− represents 2.0 ± 0.3% of all annihilation at rest. It is also observed to decay into two S-wave dipions (π+π−) (π0π0)). Under the assumption of isospin 0, this is probably , seen for the first time in its 4π decay mode.
Physics Letters B.