1,138 research outputs found
Proton-antiproton annihilation into massive leptons
We extend previous calculations of polarization observables for the
annihilation reaction to the case of heavy
leptons, such as the -lepton. We consider the case when the beam and/or
the target are polarized, as well as the polarization of the outgoing leptons.
We give the dependence of the unpolarized cross section, angular asymmetry, and
various polarization observables on the relevant kinematical variables in the
center of mass and in the laboratory system, with particular attention to the
effect of the mass induced terms.Comment: 25 pages, 8 figure
Indication on the universal hadron substructure - constituent quarks
The universality of single-spin asymmetry on inclusive pi-meson production is
discussed. This universality can be related to the hadron substructure -
constituent quarks.Comment: 3 pages, 3 figures, references adde
An absolute polarimeter for high energy protons
A study of the spin asymmetries for polarized elastic proton proton
collisions in the electromagnetic hadronic interference (CNI) region of
momentum transfer provides a method of self calibration of proton polarization.
The method can be extended to non-identical spin half scattering so that, in
principle, the polarization of a proton may be obtained through an analysis of
its elastic collision with a different polarized particle, helium 3 for
instance. Sufficiently large CNI spin asymmetries provide enough information to
facilitate the evaluation of nearly all the helicity amplitudes at small t as
well as the polarization of both initial spin half fermions. Thus it can serve
equally well as a polarimeter for helium 3
Parity Violation in Proton-Proton Scattering
Measurements of parity-violating longitudinal analyzing powers (normalized
asymmetries) in polarized proton-proton scattering provide a unique window on
the interplay between the weak and strong interactions between and within
hadrons. Several new proton-proton parity violation experiments are presently
either being performed or are being prepared for execution in the near future:
at TRIUMF at 221 MeV and 450 MeV and at COSY (Kernforschungsanlage Juelich) at
230 MeV and near 1.3 GeV. These experiments are intended to provide stringent
constraints on the set of six effective weak meson-nucleon coupling constants,
which characterize the weak interaction between hadrons in the energy domain
where meson exchange models provide an appropriate description. The 221 MeV is
unique in that it selects a single transition amplitude (3P2-1D2) and
consequently constrains the weak meson-nucleon coupling constant h_rho{pp}. The
TRIUMF 221 MeV proton-proton parity violation experiment is described in some
detail. A preliminary result for the longitudinal analyzing power is Az = (1.1
+/-0.4 +/-0.4) x 10^-7. Further proton-proton parity violation experiments are
commented on. The anomaly at 6 GeV/c requires that a new multi-GeV
proton-proton parity violation experiment be performed.Comment: 13 Pages LaTeX, 5 PostScript figures, uses espcrc1.sty. Invited talk
at QULEN97, International Conference on Quark Lepton Nuclear Physics --
Nonperturbative QCD Hadron Physics & Electroweak Nuclear Processes --, Osaka,
Japan May 20--23, 199
Measurement of Inverse Pion Photoproduction at Energies Spanning the N(1440) Resonance
Differential cross sections for the process pi^- p -> gamma n have been
measured at Brookhaven National Laboratory's Alternating Gradient Synchrotron
with the Crystal Ball multiphoton spectrometer. Measurements were made at 18
pion momenta from 238 to 748 MeV/c, corresponding to E_gamma for the inverse
reaction from 285 to 769 MeV. The data have been used to evaluate the gamma n
multipoles in the vicinity of the N(1440) resonance. We compare our data and
multipoles to previous determinations. A new three-parameter SAID fit yields 36
+/- 7 (GeV)^-1/2 X 10^-3 for the A^n_1/2 amplitude of the P_11.Comment: 14 pages, 8 figures, submitted to PR
New anomalous trajectory in Regge theory
We show that a new Regge trajectory with \alpha_{f_1} (0) \approx 1 and slope
\alpha_{f_1}'(0) \approx 0 explains the features of hadron-hadron scattering
and photoproduction of the rho and phi mesons at large energy and momentum
transfer. This trajectory with quantum numbers P = C = +1 and odd signature can
be considered as a natural partner of the Pomeron which has even signature. The
odd signature of the new exchange leads to contributions to the spin-dependent
cross sections, which do not vanish at large energy. The links between the
anomalous properties of this trajectory, the axial anomaly and the flavor
singlet axial vector f_1 (1285) meson are discussed.Comment: 20 pages, REVTeX, 8 figures (9 eps files), version to appear in Phys.
Rev.
Polarizing a stored proton beam by spin flip?
We discuss polarizing a proton beam in a storage ring, either by selective
removal or by spin flip of the stored ions. Prompted by recent, conflicting
calculations, we have carried out a measurement of the spin flip cross section
in low-energy electron-proton scattering. The experiment uses the cooling
electron beam at COSY as an electron target. The measured cross sections are
too small for making spin flip a viable tool in polarizing a stored beam. This
invalidates a recent proposal to use co-moving polarized positrons to polarize
a stored antiproton beam.Comment: 18 pages, 6 figure
Recommended from our members
Measurements of the transverse-momentum-dependent cross sections of J /ψ production at mid-rapidity in proton+proton collisions at s =510 and 500 GeV with the STAR detector
We present measurements of the differential cross sections of inclusive J/ψ meson production as a function of transverse momentum (pTJ/ψ) using the μ+μ- and e+e- decay channels in proton+proton collisions at center-of-mass energies of 510 and 500 GeV, respectively, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The measurement from the μ+μ- channel is for
- …