Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe Xi(2230) Meson and The Pomeron Trajectory
50
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We examine the possibility that the xi(2230) meson is a member of the Pomeron trajectory. A method of connecting the xi --> p pbar decay width and the pp cross sections through the Pomeron residue function is presented. We have used a relativistic, singularity-free form factor to make the analytic continuation of the residue function between crossed channels. We predict that if the xi(2230) meson is a Pomeron, then it should have a xi --> p pbar decay width of about 2 MeV.
rate research
Read More
A lower bound of 135 MeV for the width of the xi meson is obtained from analyzing the pp and pbar-p interactions by use of Regge theory. The pp data exclude a narrow xi as the latter would lead to total pbar-p cross sections far exceeding the measured ones. The broad width explains why the xi may not be seen in pbarp-p experiments.
We investigate the reaction mechanism of the $phi$-meson photoproduction off the proton target, i.e., $gamma ptophi p$, up to $sqrt{s}=2.8$ GeV. For this purpose, we employ an effective Lagrangian approach in the tree-level Born approximation, and we employ various experimental and theoretical inputs. As a theoretical setup, the vectorlike Pomeron ($C=+1$) is taken into account as a parameterized two-gluon exchange contribution. We also consider $f_1(1285)$ axial-vector-meson, ($pi,eta$) pseudoscalar-meson, and ($a_0,f_0$) scalar-meson exchanges in the $t$ channel, in addition to the experimentally confirmed nucleon resonances, such as $N^*(2000,5/2^+)$ and $N^*(2300,1/2^+)$, for the direct $phi$-meson radiations in the $s$ and $u$ channels. We provide numerical results for the total and differential cross sections as well as the spin-density matrices in the Gottfried-Jackson, Adair, and helicity frames. We observe that, together with the universally accepted pomeron contribution, the considered meson and nucleon-resonance contributions play significant roles in reproducing the experimental data for the forward and backward $phi$-meson scattering-angle regions, respectively, indicating the nontrivial interferences between mesonic and baryonic contributions.
A Regge pole model for Pomeron-Pomeron total cross section in the resonance region $sqrt{M^2}le$ 5 GeV is presented. The cross section is saturated by direct-channel contributions from the Pomeron as well as from two different $f$ trajectories, accompanied by the isolated f$_0(500)$ resonance which dominates the $sqrt{M^{2}}lesssim 1$ GeV region. A slowly varying background is taken into account. The calculated Pomeron-Pomeron total cross section cannot be measured directly, but is an essential part of central diffractive processes. In preparation of future calculations of central resonance production at the hadron level, and corresponding measurements at the LHC, we normalize the Pomeron-Pomeron cross section at large masses $sigma_{t}^{PP} (sqrt{M^2}rightarrow infty) approx$ 1 mb as suggested by QCD-motivated estimates.
A model for Pomeron-Pomeron total cross section in the resonance region $sqrt{M^{2}} le$ 5 GeV is presented. This model is based on Regge poles from the Pomeron and two different $f$ trajectories, and includes the isolated f$_{0}(500)$ resonance in the region $sqrt{M^{2}}lesssim 1$ GeV. A slowly varying background is included. The presented Pomeron-Pomeron cross section is not directly measurable, but is an essential ingredient for calculating exclusive resonance production at the LHC.
We ask the question whether the quark and gluon distributions in the Pomeron obtained from QCD fits to hard diffraction processes at HERA can be dynamically generated from a state made of ``valence-like gluons and sea quarks as input. By a method combining backward Q^2-evolution for data exploration and forward Q^2-evolution for a best fit determination, we find that the diffractive structure functions published by the H1 collaboration at HERA can be described by a simple ``valence-like input at an initial scale of order mu^2 ~ 2.3-2.7 GeV^2. The parton number sum rules at the initial scale mu^2 for the H1 fit gives 2.1pm .1pm .1 and .13pm .01 pm .02 for gluon and sea quarks respectively, corresponding to an initial Pomeron state made of (almost) only two gluons. It has flat gluon density leading to a plausible interpretation in terms of a gluonium state.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
