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E decay to eta pi pi in anti-p p annihilation at rest

The Crystal Barrel collaboration Amsler, C. ; Armstrong, D.S. ; Baker, C.A. ; et al.

Phys.Lett.B 358 (1995) 389-398, 1995.

Inspire Record 407517 DOI 10.17182/hepdata.28511

We have observed the ηπ + π − and ηπ 0 π 0 decay modes of the E meson in p p annihilation at rest into π + π − π 0 π 0 η . The mass and width of the E meson are 1409 ± 3 and 86 ± 10 MeV. The production and decay branching ratio is B( p p → Eππ)B(E → ηππ) = (3.3 ± 1.0) × 10 −3 . With a spin-parity analysis we determine that J P = 0 − . The observation of the ηπ 0 π 0 decay mode establishes that E is isoscalar ( C = +1). We find that E decays to η ( ππ ) s (where ( ππ ) s is an S-wave dipion) and πa 0 (980)(→ πη ) with a relative branching ratio of (78 ± 16) %. Using the K K π production and decay branching ratio measured earlier we determine that B[E → K K π] B[E → ηππ] = 0.61 ± 0.19 . A comparison with observations in radiative J Ψ decays suggests that E and ι η (1416) are identical.

1 data table

Table 1

Unobserved channels (E --> ETA 2PI0)2PI0 and (E --> ETA PI+ PI-)PI+PI- was taken into account.

First observations of Pontecorvo reactions with a recoiling neutron

The Crystal Barrel collaboration Amsler, C. ; Armstrong, D.S. ; Augustin, I. ; et al.

Z.Phys.A 351 (1995) 325-331, 1995.

Inspire Record 407110 DOI 10.17182/hepdata.16505

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.

1 data table

Table 1

No description provided.

Polarized target asymmetry in pion proton bremsstrahlung at 298-MeV

Bosshard, A. ; Amsler, Claude ; Bistirlich, J.A. ; et al.

Phys.Rev.Lett. 64 (1990) 2619-2622, 1990.

Inspire Record 303404 DOI 10.17182/hepdata.22827

First data are presented for the polarized-target asymmetry in the reaction π+p→π+pγ at an incident pion energy of 298 MeV. The geometry was chosen to maximize the sensitivity to the radiation of the magnetic dipole moment μΔ of the Δ++(1232 MeV). A fit of the asymmetry in the cross section d5σ/dΩπ dΩγ dk as a function of the photon energy k to predictions from a recent isobar-model calculation with μΔ as the only free parameter yields μΔ=1.64(±0.19expΔ,±0.14 theor)μp. Though this value agrees with bag-model corrections to the SU(6) prediction μΔ=2μp, further clarifications on the model dependence of the result are needed, in particular since the isobar model fails to describe both the cross section and the asymmetry at the highest photon energies.

2 data tables

Table 1

No description provided.

Table 2

No description provided.

$\bar{p} p$ Annihilation Into $\pi^+ \pi^-$ and $K^+ K^-$ From Atomic $p$ States

The ASTERIX collaboration Doser, M. ; Botlo, M. ; Ahmad, S. ; et al.

Nucl.Phys.A 486 (1988) 493-511, 1988.

Inspire Record 261310 DOI 10.17182/hepdata.37012

We have obtained the branching ratios for p p annihilation at rest into π + π − and K + K − in a pure p p initial angular momentum state L = 1. A gaseous hydrogen target at normal pressure and temperature was used and events associated with transitions of the antiprotonic atom to the 2p level were selected by detecting the Balmer X-ray series. The branching ratios for p p annihilation into π + π − and K + K − from the 2p state are (4.81 ± 0.49) × 10 −3 and (2.87 ± 0.51) × 10 −4 , respect The pion yield is slightly larger than in liquid hydrogen, where L = 0 annihilation dominates, while the kaon yield is suppressed by a factor of four. Using these and previous data, we derive the branching ratios for pp annihilation into all ππ and K K modes from S and P states. A measurement in gaseous hydrogen, without X-ray requirement, yields the branching ratios (4.30 ± 0.14) × 10 −3 and (6.92 ± 0.41) × 10 −4 . With the known branching ratios of (3.33 ± 0.17) × 10 −3 and (1.01 ± 0.05) × 10 −3 in liquid hydrogen, we find that (50.3 ± 6.4)% of all annihilations in gas at NTP occur in the initial angular momentum state L = 1.

2 data tables

Table 1

Axis error includes +- 0.0/0.0 contribution (?////).

Table 2

Axis error includes +- 0.0/0.0 contribution (?////).

Measurement of Pion Proton Bremsstrahlung for Pions at 299-{MeV}

Meyer, C.A. ; Amsler, Claude ; Bosshard, A. ; et al.

Phys.Rev.D 38 (1988) 754-767, 1988.

Inspire Record 268867 DOI 10.17182/hepdata.23271

We have measured the fivefold differential cross section d5σ/dΩπdΩγdEγ for the process π+p→π+pγ with incident pions of energy 299 MeV. The angular regions for the outgoing pions (55°≤θlabπ≤95°), and photons (θlabγ=241°±10°) in coplanar geometry are selected to maximize the sensitivity to the radiation from the magnetic dipole moment of the Δ++(1232) resonance. At low photon energies, the data agree with the soft-photon approximation to pion-proton bremsstrahlung. At forward pion angles the data agree with older data and with the latest theoretical calculations for 2.3μp≤μΔ≤3.3μp. However at more backward pion angles where no data existed, the predictions fail.

2 data tables

Table 1

No description provided.

Table 2

No description provided.

Search for Monochromatic Pion Emission in $\bar{p} p$ Annihilation From Atomic $p$ States

The ASTERIX collaboration Ahmad, S. ; Amsler, Claude ; Armenteros, R. ; et al.

Phys.Lett.B 152 (1985) 135-139, 1985.

Inspire Record 207457 DOI 10.17182/hepdata.49644

Narrow states observable through the emission of monoenergetic charged pions have been searched for in p p annihilation at rest in a gaseous hydrogen target where annihilation from atomic angular momentum L = 1 states dominates. No structure is observed. The 5σ upper limit for the production of narrow states in the mass range 1100–1670 MeV is 2 × 10 −3 of all annihilations.

1 data table

Table 1

X means a narrow state.

SEARCH FOR STRUCTURE IN THE LOW-ENERGY ANTI-p p p ANNIHILATION CROSS-SECTION

Jastrzembski, E. ; Haik, N. ; McFarlane, W.K. ; et al.

Phys.Rev.D 23 (1981) 2784, 1981.

Inspire Record 159386 DOI 10.17182/hepdata.24081

Relative cross sections have been measured for p¯p annihilation by a new technique in the invariant-mass range 1920-1960 MeV. The 90%-confidence upper limit on simple Breit-Wigner enhancements in the S region (between 1930 and 1942 MeV) of width 4 MeV or narrower is 12 mb MeV, assuming a simple dependence with momentum of the nonresonant cross section.

1 data table

Table 1

No description provided.

The Normalization of p p Polarization Between 200-MeV and 520-MeV

Amsler, C. ; Bugg, D.V. ; Axen, D. ; et al.

J.Phys.G 4 (1978) 1047-1053, 1978.

Inspire Record 135489 DOI 10.17182/hepdata.38559

The absolute normalisation of the polarisation in pp elastic scattering at 24 degrees lab has been determined by means of a double-scattering experiment to an accuracy of +or-1.5% at five energies between 200 and 520 MeV.

1 data table

Table 1

No description provided.

Proton Proton Elastic Scattering from 150-MeV to 515-MeV

Bugg, D.V. ; Edgington, J.A. ; Amsler, Claude ; et al.

J.Phys.G 4 (1978) 1025, 1978.

Inspire Record 123232 DOI 10.17182/hepdata.38563

The parameters D, R, R' and P for pp elastic scattering have been measured in the centre-of-mass angular range 13 degrees to 58 degrees with an accuracy of about +or-0.02 at 209, 324, 379, 425 and 515 MeV. These results are incorporated with earlier data into a phase-shift analysis. Phase-shifts are generally in agreement with the theoretical predictions of the Paris group, although the F-wave spin-orbit combination is rather stronger than predicted. The fitted value for the pi 0pp coupling constant in g02=14.06+or-0.65.

6 data tables

Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.