Search

Data on p p→ηπ + π − π + π − at rest show two resonant processes: (a) f 0 (1370)η,f 0 (1370)→σσ and ρρ , (b) η(1440)σ , η(1440)→ηπ + π − . The branching ratio BR[f 0 (1370)→ρρ]/BR[f 0 (1370)→σσ]=0.98±0.25 in the mass range available here. Using data on p p→ηπ 0 π 0 , the ratio Γ 4π /Γ 2π ⩾5 for f 0 (1370) . The effects of the strongly s -dependent width of f 0 (1370) are discussed in some detail. The η(1440) is observed decaying to ησ and a 0 (980)π , with strong destructive interference between them. In its decay to a 0 (980)π , a narrow peak appears in the ηπ mass spectrum, but 30–50 MeV above that usually attributed to a 0 (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 a 0 (980) to ηπ above the KK threshold.

Measurements of two-body branching ratios for p p annihilations at rest in liquid and gaseous (12 ρ STP ) hydrogen are reported. Channels studied are p p →π 0 π 0 ,π 0 η , K 0 S K 0 L , K + K − . The branching ratio for the π 0 π 0 channel in liquid H 2 is measured to be ( 6.14±0.40)×10 −4 . The results are compared with those from other experiments. The fraction of P-state annihilation for a range of target densities from 0.002 ρ STP to liquid H 2 is determined. Values obtained include 0.11±0.02 in liquid H 2 and 0.48±0.04 in 12 ρ STP H 2 gas.

A combined fit is presented to data on pbar-p annihilation in flight to final states eta-pizero-pizero, pizero-pizero, eta-eta, eta-etaprime and piminus-piplus. The emphasis lies in improving an earlier study of eta-pizero-pizero by fitting data at nine pbar momenta simultaneously and with parameters consistent with the two-body channels. There is evidence for all of the I=0, C=+ q-qbar states expected in this mass range. New resonances are reported with masses and widths M,Gamma as follows: JPC = 4^{-+} (2328+-38, Gamma=240+-90) MeV, 1^{++} (1971+-15, 240+-45) MeV, 0^{-+} (2285+-20, 325+-30) MeV, and 0^{-+} (2010 ^{+35}_{-60}, 270+-60) MeV. Errors on the masses and widths of other resonances are also reduced substantially. All states lie close to parallel straight line trajectories of excitation number v. mass squared., Comment: 13 pages, 5 figures, pdflatex

Data on pbar-p -> etaprime(958)-pizero-pizero are presented at nine pbar momenta from 600 to 1940 MeV/c. Strong S-wave production of f_2(1270)-etaprime is observed, requiring a J^{PC} = 2^{-+} resonance with mass M = 2248+-20 MeV, Gamma = 280+-20 MeV.

Data are presented on p p→ωπ 0 π 0 π 0 at rest in gaseous and liquid hydrogen. These data fit naturally to 1 P 1 ( p p)→[ω′(1420)π 0 ] L=0 and 3 S 1 ( p p)→[ω′(1420)π 0 ] L=1 , with ω′→ωσ and b1(1235)π0. If a single ω′ is fitted, its optimum mass is 1370±25 MeV; the width Γ=360+100−60 MeV is larger than earlier estimates.

Data taken with the Crystal Barrel detector on p p → π 0 η , π 0 η ′ and 3 π 0 are presented at p momenta from 600 to 1940 MeV/c. We observe towers of I = 1 resonances up to J PC = 4 ++ at ∼ 2050 and ∼ 2300 MeV [1,2].

High statistics data on p p→ηπ 0 π 0 π 0 at nine beam momenta from 900 to 1940 MeV/c require the presence of three I=0, JPC=2−+ mesons with masses and widths (i) M=1645±6(stat)±20(syst) MeV, Γ=200±7±20 MeV, (ii) M=1860±5±15 MeV, Γ=250±25±25 MeV, (iii) M=2030±5±15 MeV, Γ=205±10±15 MeV. The η2(1645) and η2(2030), together with η2(2300) observed earlier, may be interpreted as a sequence of expected q q states. The η2 at 1860 MeV appears to be an extra state, hence a candidate for a hybrid. Decay branching ratios of all three states to a2(1320)π, f2(1270)η and a0(980)π are established. The η2 at 1860 MeV decays dominantly to f2η and a2π, as predicted for a hybrid. The η2(2030) decays dominantly to a2π with orbital angular momentum L=2 and slightly less strongly to a2π with L=0.

Data on p p→ωπ 0 π 0 from the Crystal Barrel experiment are presented in the range of beam momenta 600 to 1940 MeV/c. A partial wave analysis finds structures which may be interpreted in terms of a number of q q resonances expected in this mass range. There is a well defined JPC=1+− resonance with mass and width M=2265±25 MeV, Γ=190±35 MeV, and a 3+− state with M=2275±35 MeV, Γ=180±35 MeV. There is a further well defined 1−− resonance with M=2145±20 MeV, Γ=200±25 making a natural I=0 partner for ρ(2150). In addition, there is evidence for a second, lower 1+− state and triplet 2−−, 1−− and 3−− states which are somewhat less well defined in masses and widths.

New data on p p→ηπ 0 π 0 π 0 at beam momenta 900–1200 MeV/c reveal evidence for a threshold enhancement in the f0(980)η channel. Quantum numbers JPC=0−+ are preferred strongly over 1++ and 2−+. The enhancement may be interpreted as the high mass tail of a resonance below threshold decaying to f0(980)η. The η(1440)π final state is observed with η(1440)→ησ and a0(980)π. It is produced dominantly from the p p 3P0 channel, and is consistent with S-wave decays from an I=1, JPC=0++ resonance observed earlier at 2025 MeV.

A partial wave analysis is presented of Crystal Barrel data on p p→π 0 π 0 , ηη and ηη′ from 600 to 1940 MeV/c, combined with earlier data on dσ/dΩ and P for p p→π − π + . The following s -channel I=0 resonances are identified: (i) J PC =5 −− with mass and width ( M , Γ ) at ( 2295±30 , 235 +65 −40 ) MeV, (ii) J PC =4 ++ at ( 2020±12 , 170±15 ) MeV and ( 2300±25 , 270±50 ) MeV, (iii) 3 D 3 J PC =3 −− at ( 1960±15 , 150±25 ) MeV and ( 2210±40 , 360±55 ) MeV, and a 3 G 3 state at ( 2300 +50 −80 ,340±150) MeV, (iv) J PC =2 ++ at ( 1910±30 , 260±40 ) MeV, ( 2020±30 , 275±35 ) MeV, ( 2230±30 , 245±45 ) MeV, and ( 2300±35 , 290±50 ) MeV, (v) J PC =1 −− at ( 2005±40 , 275±75 ) MeV, and ( 2165±40 , 160 +140 −70 ) MeV, and (vi) J PC =0 ++ at ( 2005±30 , 305±50 ) MeV, ( 2105±15 , 200±25 ) MeV, and ( 2320±30 , 175±45 ) MeV. In addition, there is a less well defined 6 ++ resonance at 2485±40 MeV, with Γ=410±90 MeV. For every J P , almost all these resonances lie on well defined linear trajectories of mass squared versus excitation number. The slope is 1.10±0.03 GeV 2 per excitation. The f 0 (2105) has strong coupling to ηη , but much weaker coupling to π 0 π 0 . Its flavour mixing angle between q q and s s is (59–71.6) ° , i.e. dominant decays to s s . Such decays and its strong production in p p interactions strongly suggest exotic character.

Data are reported on p p→π 0 π 0 , ηη and ηη′ over the range of laboratory momenta 600 to 1940 MeV/c. For the π0π0 data, there is a systematic disagreement in normalisation with earlier data of Dulude et al. [Phys. Lett. B 79 (1978) 329, 335]. The technicalities concerning this normalisation are described in full. An amplitude analysis, reported in an accompanying paper, favours the normalisation reported here. For ηη and ηη′ there is excellent agreement between 4γ and 8γ data.

The rho mass, width and line shape in p(over)-bar-p annihilation at rest into pi(+)pi(-)pi(0)

Data are reported on p p→π 0 π 0 over the range of laboratory momenta 600 to 1940 MeV/c. The shapes of angular distributions are similar to earlier data of Dulude et al. above 1100 MeV/c, but show some systematic disagreements. The absolute normalisation disagrees seriously. An amplitude analysis favours the normalisation reported here.

Data taken with the Crystal Barrel detector on p p→ηη and ηη′ are presented from 600 to 1940 MeV/c. The f0(2105) appears strongly in the ηη channel with mass and width consistent within errors with earlier data. It is produced strongly in p p interactions, but with large branching ratio to ηη compared with ππ. This is incompatible with an unmixed non-strange q q state.

We report a partial wave analysis of Crystal Barrel data on p p→π 0 π 0 , ηη and ηη′ from 600 to 1940 MeV/c, combined with earlier data on dσ/dΩ and P for p p→π − π + . Most of the q q resonances expected in this mass range and in these channels are identified. Observed masses follow a simple systematic pattern of linear trajectories of mass squared v. radial quantum number n, with a slope of 1.10±0.03 Gev2 per unit of n.

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 observed.

Data on pbar-b annihilation in flight into pizero-pizero-eta are presented for nine beam momenta 600 to 1940 MeV/c. The strongest four intermediate states are found to be f_2(1270)-eta, a_2(1320)-pi, sigma-eta and a_0(980)-pi. Partial wave analysis is performed mainly to look for resonances formed by pbar-p and decaying into pizero-pizero-eta through these intermediate states. There is evidence for the following s-channel I = 0 resonances : two 4^{++} resonances with mass and width (M,Gamma) at (2044, 208) MeV and (2320+-30, 220+-30) MeV; three 2^{++} resonances at (2020+-50, 200+-70) MeV, (2240+-40, 170+-50) MeV and (2370+-50, 320+-50) MeV; two 3^{++} resonances at (2000+-40, 250+-40) MeV and (2280+-30, 210+-30) MeV; a 1^{++} resonance at (2340+-40, 340+-40) MeV; and two 2^{-+} resonances at (2040+-40, 190+-40) MeV and (2300+-40, 270+-40) MeV.

Antiproton-proton annihilation into π 0 π 0 η has been studied with incident beam momenta of 0.6 to 1.94 GeV/c. The main aim is to look for resonances formed by p p and decaying into π 0 π 0 η . Resonances observed are: two 4 ++ resonances with mass and width (M, Γ ) at (2044, 208) MeV and (2320±30, 220±30) MeV; three 2 ++ resonances at (2020±50, 220±70) MeV, (2240±40, 170±50) MeV and (2370±50, 320±50) MeV; two 3 ++ resonances at (2000±40, 250±40) MeV and (2280±30, 210±30) MeV; a 1 ++ resonance at (2340±40, 340±40) MeV; and two 2 −+ resonances at (2040±40, 190±40) MeV and (2300±40, 270±40) MeV.

We present data on p p→3π 0 at nine p momenta from 600 to 1940 MeV/c. This process is dominated by the f2(1270)π0 channel, where we observe I=1 resonances with the following masses and widths: 4++(2260±15), Γ=180±20 MeV, 4++(2005±25), Γ=360±80 MeV, 3++(2310±40), Γ=180+120−60 MeV, 3++(2070±20), Γ=170±40 MeV, 2++(2280±30), Γ=280±50 MeV, 2++(2100+10−30), Γ=360+40−100 MeV, 1++(2100±20), Γ=300+30−60 MeV, and 1++(2340±40), Γ=230±70 MeV.

Data taken with the Crystal Barrel detector on p p→π 0 η and π 0 η ′ are presented at p momenta from 600 to 1940 MeV/c. A partial wave analysis finds two alternative solutions, one significantly preferred over the other. Both contain resonances of similar masses and widths, but different coupling constants and phases. The favoured solution contains a J PC =0 ++ resonance at 2025±30 MeV with Γ =330±75 MeV, and three 2 ++ resonances as follows: (i) at 1990 +15 −30 MeV with Γ =190±50 MeV (dominantly 3 P 2 ), (ii) at 2060±20 MeV with Γ =195±30 MeV (dominantly 3 F 2 ), (iii) at 2265±20 MeV with Γ =235 +60 −35 MeV (dominantly 3 F 2 ), There are two 4 ++ resonances at 2025±40 MeV with Γ =250 +80 −55 MeV and at 2300±20 MeV with Γ =230±40 MeV. Errors cover systematic errors and statistical fluctuations of 3 σ .

From an analysis of p p→4π 0 at a beam momentum of 1940 MeV/c, we find evidence for a J PC =1 ++ resonance at 1640 ±12( stat )±30( syst ) MeV with Γ =300±22±40 MeV; it is observed decaying both to σπ with L =1 and to f 2 (1270) π with L =1.

Data on the final state ηηπ 0 are presented for beam momenta of 1350, 1525, 1642, 1800 and 1940 MeV/ c . There is evidence for the presence of a broad high mass 2 + contribution in ηη ; the amplitude analysis fits it as a resonance with mass M =1980±50 MeV and width Γ =500±100 MeV. It has the curious feature that it is produced dominantly with orbital angular momentum L =1 in the final state and with component of spin ±1 along the beam direction. It contributes typically ∼15−20% of the integrated cross section. In addition, the presence of a 2 (1660) is confirmed at all beam momenta. Also f 0 (2100)→ ηη is confirmed.

We present data on pbar-p -> eta-eta-pizero at beam momenta of 600, 900, 1050, and 1200 MeV/c. At the higher three momenta, a signal is clearly visible due to pbar-p -> f_0(1770)-pizero, f_0(1770) -> eta-eta. It has mass 1770+-12 MeV and width 220+-40 MeV, where errors cover systematic uncertainties as well as statistics.

With antiprotons stopped in liquid deuterium, the p n annihilation channel π−π0η was studied using a final sample of 52 576 events obtained for a spectator proton momentum q q quantum numbers IG=1−, JPC=1−+. The extracted Breit-Wigner resonance parameters are m=(1400±20±20) MeV/c2 and Γ=(310±50+50−30) MeV/c2.

Background: Although previous studies have established the presence of an eosinophil-rich cellular infiltrate in the small airways of asthmatic lungs, the expression of cytokines within the peripheral airways has been largely unexplored. The purpose of our study was to test the hypothesis that T H2 -type cytokines are increased in the peripheral airways and parenchyma of asthmatic lungs. Methods: The presence of messenger ribonucleic acid (mRNA) encoding both T-helper (T H1 )-type (IL-2, interferon-γ) and T H2 -type (IL-4, IL-5) cytokines in surgically resected lungs from six asthmatic and 10 nonasthmatic subjects was determined by in situ hybridization. Colocalization of IL-5 mRNA within the large and small airways was performed by simultaneous in situ hybridization and immunocytochemistry. Results: Expression of IL-5 mRNA-positive cells was significantly increased in the large and small airways and in the lung parenchyma of asthmatic subjects compared with nonasthmatic subjects. In the asthmatic individuals, the expression of IL-5 mRNA was increased in the small airways compared with the large airways. There was also an increase in the number of cells expressing IL-4 mRNA in the large and small asthmatic airways compared with the nonasthmatic airways. In contrast, the numbers of IL-2 and interferon-γ mRNA-positive cells did not differ between asthmatic and nonasthmatic individuals. Conclusions: We conclude that there is an increased expression of T H2 -type cytokines within the peripheral airways of asthmatic lungs and suggest that the small airways contribute to the pathophysiology of asthma. (J Allergy Clin Immunol 1998;101:386-90.)

Crystal Barrel data are presented on p−p → ηπ0π0π0 at rest in liquid hydrogen and also in gaseous hydrogen at 12 bar. Annihilation from the initial 3P0 state relative to 3P2 is stronger in liquid than in gas by a factor 2.46 ± 0.15, in fair agreement with a prediction by Batty. There is a definite peak due to η(1440). Liquid data determine its mass as M = 1413 MeV, Γ = 49 ± 8 MeV. The mass is, however, lower in gas than in liquid by 12 ± 3 MeV; we attribute this mass shift to interference with broad background amplitudes. The η (1440) decays dominantly to ησ: BR [a0(980)π,a0 → ηπ]/BR[ησ] = 0.4 ± 0.2. However, there is strong destructive interference between these two decay modes. There is also a strong, broad ηππ component with JPC = 0−+, consistent with an earlier analysis proposing a very wide η(1800) resonance; it contributes 31% of the ηπ0π0π0 branching ratio in liquid. At the highest ηππ masses, there are definite 2−+ and l++ signals, but we cannot establish precise resonance masses or widths. There is also evidence for the production of f2 (1565), decaying to a2 (1320)π.

The π 0 momentum dependence of the decay η → π + π − π 0 has been measured with the Crystal Barrel detector. The analysis is based on 3230 events. The results of this independent measurement are compared to new chiral perturbation theory calculations and previous measurements.

The decay p p ( at rest ) → K L o K ± π ∓ π o , studied on a sample of more than 14000 events, is found to proceed dominantly via two-body channels containing resonances with open strangeness. Contributions from K 1 (1270) K and K 1 (1400) K , branching into the successive K1-decay modes, and from K ∗ K ∗ , K ∗ ( K π) s and (Kπ) s ( K π) s are extracted by means of a partial-wave analysis which accounts well for the data and also allows a search for weak contributions from other (Kππ) and from ( K K π ) resonances. Striking asymmetries between the charged and the neutral kaonic resonances give evidence for interfering isospin 0 and 1 annihilation amplitudes.

The annihilation channel p p →K + K − π 0 in liquid hydrogen at rest has been studied with the Crystal Barrel detector at LEAR. The measured branching ratio is: BR ( p p → K + K − π 0 )=(2.37±0.15)×10 −3 . A partial wave analysis shows that this reaction is dominated by the π (K K ) S , K K ∗ (892) and π φ (1020) intermediate states. Weak signals are observed for π a 2 (1320), π f 2 (1270), π f 2 ′(1525) and K(Kπ) S . A satisfactory description of the Dalitz plot requires the introduction of π (K K ) P intermediate states with at least one pole.

We have measured the branching ratio for the radiative decay ω → ηγ with ω mesons produced in antiproton-proton annihilation at rest into π0ω and ηω. Taking into account ϱ - ω mixing we find a branching ratio B(ω → ηγ) = (6.6 ± 1.7) × 10−4, in accord with the constructive interference solution in other experiments. The upper-limit for the direct radiative decay ω → 3γ is 1.9 × 10−4 at 95% confidence level.

The π + π − invariant mass distribution produced in p p annihilation at rest and recoiling against η mesons exhibits large interference between the amplitudes for ϱη and ωη production. The interference can be quantitatively described within the framework of ϱ-ω interference. We find full coherence between the ϱω-ωη production amplitudes and a vanishing relative production phase. The implications of this result for p p annihilation dynamics are discussed.

A partial wave analysis of pp → π0π0η′ has been performed using the η′ → π0π0η and η′ → γγ decay modes. The data are dominated by an η′ recoiling against the (ππ) S-wave. In addition, α2 (1320) → η′π0 is needed. There is evidence for contributions from α0(1450) → η′π0. The branching ratio of α0(1450) → η′π0 with respect to ηπ0 is consistent with the prediction of SU(3).

The distribution of m ( π + π − ) in the decay η ′ → π + π − γ has been measured with the Crystal Barrel detector. The results are based on a total of 7392 observed η′ decays. The box anomaly constant is extracted from this and its value is found to agree well with theoretical expectations. The pseudoscalar nonet parameters ( f 1 , f 8 and θ PS ) are determined. Finally, we find that there is a problem of consistency between QCD and the standard VDM assumption.

We report on a measurement of the branching ratio of the rare decay $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\omega}}\ensuremath{\eta}\ensuremath{\gamma}$ relative to the well known decay $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\omega}}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}.$ The \ensuremath{\omega}'s are produced in $p\overline{p}\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\omega}$ and $p\overline{p}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\omega}.$ Eigenstate mixing and interference effects of the \ensuremath{\omega} and ${\ensuremath{\rho}}^{0}$ are taken into account, as well as coherent interference with the background. We find evidence for the non-resonant annihilation channel $B(p\overline{p}\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\eta}\ensuremath{\gamma})=(3.5\ifmmode\pm\else\textpm\fi{}1.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ and limit the value of $B(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\omega}}\ensuremath{\eta}\ensuremath{\gamma})$ to the range of $(0.7\mathrm{to}5.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ depending on the degree of coherence with the background.

The annihilation channel pp to K/sup +/K/sup -/ pi /sup 0/ in liquid hydrogen at rest has been studied with the Crystal Barrel detector at LEAR. The measured branching ratio is: BR(pp to K/sup +/K/sup -/ pi /sup 0/)=(2.37+or-0.15)*10/sup -3/. A partial wave analysis shows that this reaction is dominated by the pi (KK)/sub S/, KK*(892) and pi phi (1020) intermediate states. Weak signals are observed for pi a /sub 2/(1320), pi f/sub 2/(1270), pi f/sub 2/'(1525) and K(K pi )/sub S/. A satisfactory description of the Dalitz plot requires the introduction of pi (KK)/sub P/ intermediate states with at least one pole. (25 refs).