Upper limits for the production of new light gauge bosons in 0 , and 0 decays have been obtained with the Crystal Barrel detector. The kinematically well-constrained reactions pp ! 0 0 P have been studied, where P 0 ; ; 0 decays through the emission of a single photon recoiling against a missing state X. X can be a long-lived weakly interacting particle or X !. This paper gives full detail of the analysis of our previous work and extends the search to 0 decay. No signal has been observed and branching ratio upper limits (90 % C:L:) of 6 10 ?5 have been obtained for masses of the gauge boson lying between 65 MeV and 125 MeV (0 decay), 6 10 ?5 , for X masses between 200 MeV and 525 MeV (decay), and 4 10 ?5 , for X masses between 50 MeV and 925 MeV (0 decay). The 0-decay limit represents a factor of 4 to 8 (depending on the X-mass) improvement when compared to the existing limit, whereas the and 0 decay limits have been measured for the rst time, thereby extending the M X range from 125 MeV up to 925 MeV.

A fresh analysis is reported of high statistics Crystal Barrel data on <(p)over bar p> --> 3 pi(0), eta eta pi(0), eta pi(0) pi(0) and eta eta'pi(0) at rest. This analysis is made fully consistent with CERN-Munich data on pi(+)pi(-) --> pi(+)pi(-) up to a mass of 1900 MeV, with GAMS data on pi(+)pi(-) --> pi(0) pi(0), and with BNL and ANL data on pi(+)pi(-) --> , which are fitted simultaneously. There is evidence for an I = 0, J(PC) = 2(++) resonance with weak (less than or equal to 7%) coupling to pi pi, strong coupling to both rho rho and omega omega and pole position 1534 - i90 MeV. This resonance agrees qualitatively with GAMS and VES data on pi pi --> omega omega, previously interpreted in terms of a resonance at 1590-1640 MeV. New masses and widths for (A) f(0)(1370) and (B) f(0)(1500), fitted to all eight data sets, are M(A) = 1300 +/- 15 MeV, Gamma(A) = 230 +/- 15 MeV, M(B) = 1500 +/- 8 MeV, Gamma(B) = 132 +/- 15 MeV. Branching ratios to pi pi and eta eta are given, and differ significantly from earlier determinations because of a new procedure.

A fresh analysis is reported of high statistics Crystal Barrel data on pp → 3π0, ηηπ0, ηπ0π0 and ηη′π0 at rest. This analysis is made fully consistent with CERN-Munich data on π+π− → π+π− up to a mass of 1900 MeV, with GAMS data on π+π− → π0π0, and with BNL and ANL data on π+π− → KK, which are fitted simultaneously. There is evidence for an I = 0, JPC = 2++ resonance with weak (≤ 7%) coupling to ππ, strong coupling to both ϱϱ and ωω and pole position 1534 - i90 MeV. This resonance agrees qualitatively with GAMS and VES data on ππ → ωω, previously interpreted in terms of a resonance at 1590–1640 MeV. New masses and widths for (A) ƒ0(1370) and (B) ƒ0(1500), fitted to all eight data sets, are MA = 1300 ± 15 Mev, ΓA = 230 ± 15 MeV, MB = 1500 ± 8 MeV, ΓB = 132 ± 15 MeV. Branching ratios to ππ and ηη are given, and differ significantly from earlier determinations because of a new procedure.

Data on\(\bar pp \to \eta \pi ^0 \pi ^0 \pi ^0 \) 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 −21 +40 ±25 MeV, decays toα 2(1320)π withL=0. It may be interpreted as the\(q\bar q^1 \) D 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(1320)π andf 2(1270)η withL=1. There is no evidence for resonances with decays toa 0(980)π, ση orf 0(980)η.

(p) over bar p annihilation is a very promising field in searches for interesting mesonic states. A wide variety of different mesonic final states is found with the Crystal Barrel detector. Many of these channels can be traced back to original (p) over bar p transitions into two mesons. This report summarizes Crystal Barrel results on two-body reactions found in (p) over bar p annihilation in flight into all neutral final states. The final states (p) over bar p --> 0(-)0(-) and (p) over bar p --> 0(-)omega (0(-) = pi(0), eta) for which partial wave analyses have been performed will be emphasized. The highest contributing angular momenta found in these analyses are J(max) = 3HBAR for 600 MeV/c, J(max) = 4HBAR for 1200 MeV/c, and J(max) = 6HBAR for 1940 MeV/c.

Upper limits for the production of new light gauge bosons in pi(0), eta and eta' decays have been obtained with the Crystal Barrel detector. The kinematically well-constrained reactions <(p)over bar p> --> eta(0) eta(0) P have been studied, where P = eta(0), eta eta' decays through the emission of a single photon recoiling against a missing state X. X can be a long-lived weakly interacting particle or it decays into <nu(nu)over bar>. The resulting branching ratio upper limits (90% C.L.) are: 6 x 10(-5) for masses M(X) of the missing particle X lying between 65 MeV/c(2) and 125 MeV/c(2) (pi(0) decay), 6 x 10(-5) for M(X) between 200 MeV/c(2) and 525 MeV/c(2) (eta decay), and 4 x 10(-5) for M(X) between 50 MeV/c(2) and 925 MeV/c(2) (eta/decay). The eta(0)-decay limit represents an improvement by a factor of 4 to 8 (depending on M(X)) when compared to the existing limit, whereas the eta and eta' decay limits have been measured the first time, thereby extending the M(X) range from 125MeV/c(2) up to 925 MeV/c(2).

A partial-wave analysis of the reaction p $($) over bar$$ p-->pi(0) pi(0) pi(0) has been performed using a high-quality high-statistics data set of 712 000 events. In addition to the f(0)(975) and f(0)(1300), the scalar resonance with mass m = (1500 +/- 15) MeV and width Gamma = (120 +/- 25) MeV is necessary to describe the data.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Curtis A. Meyer; New crystal barrel results in the scalar meson sector. AIP Conf. Proc. 10 July 1995; 338 (1): 465–470. https://doi.org/10.1063/1.48513 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

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(¯pd→π0)=(7.03±0.72)×10−6, BR(¯pd→ηn)=(3.19+0.48)×10−6, BR(¯pd→ωn)=(22.8+4.1)×10−6, BR(¯pd→η′n)14×10−6 (at 95% confidence level). Assuming charge independence, our result for¯ pd→π0n is compatible with measurements of the only other observed Pontecorvo reaction ¯pd → π−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.

We have observed the eta pi(+)pi(-) and eta pi(0) pi(0) decay modes of the E meson in ($) over bar pp annihilation at rest into pi(+)pi(-)pi(0) pi(0) eta. The mass and width of the E meson are 1409 +/- 3 and 86 +- 10 MeV. The production and decay branching ratio is B(($) over bar pp --> E pi pi)B(E --> eta pi pi = (3.3 +/- 1.0) x 10(-3). With a spin-parity analysis we determine that J(p) = 0(-). The observation of the eta pi(0) phi(0) decay mode establishes that E is isoscalar (C = + 1). We find that E decays to eta(pi pi)(s) (where (pi pi)(s) is an S-wave dipion) and pi alpha(0)(980)(--> pi eta) with a relative branching ratio of (78 +/- 16)%. Using the K ($) over bar K pi production and decay branching ratio measured earlier we determine that B[E --> $($) over bar$$ KK pi]/B[E --> eta pi pi] = 0.61 +/- 0.19. A comparison with observations in radiative J/psi decays suggests that E and iota/eta(1416) are identical.

We report the observation of nucleon resonances in the reaction ($) over bar d --> pi(0) pi(0) n for antiprotons stopping in liquid deuterium. The process p ($) over bar d --> Delta (1232) pi(0) is identified and its branching ratio determined to be (2.21 +/- 0.24). 10(-5).

Pontecorvo reactions are antiproton annihilations on nuclei in which the final states are of a type not attainable from annihilations on free nucleons, for example p̄d→Xn, where X is a single meson. We report on the first observations of Pontecorvo reactions with a recoiling neutron, from p̄ annihilation at rest in liquid deuterium. The results are B.R.(p̄d→π0n)=(6.63±0.59)×10−6, B.R.(p̄d→ηn)=(2.99±0.42)×10−6, B.R.(p̄d→ωn)=(21.2×3.5)×10−6, and B.R.(p̄d→η′n) ≤12×10−6 (at 90% C.L.). The result for p̄d→π0n is compatible with the only previously observed Pontecorvo reaction p̄d→π−p, assuming charge independence. The ratios of these branching ratios are compared to predictions based on dynamical models of the annihilation process which reproduce the general features of the data.

The branching ratios Gamma(eta --> 3 pi(0))/Gamma(eta --> pi(+)pi(-)pi(0)) = 1.44 +/- 0.09 +/- 0.10 and Gamma(eta --> gamma gamma)/Gamma(eta --> pi(+)pi(-)pi(0)) = 1.78 +/- 0.10 +/- 0.13 have been determined using the Crystal Barrel detector at LEAR. The latter ratio yields a partial width of Gamma(eta --> pi(+)pi(-)pi(0)) = 0.26 +/- 0.03 keV using the known value for Gamma(eta -->gamma gamma). The eta --> pi(+)pi(-)pi(0). Dalitz plot is compared to the predictions of chiral perturbation theory.