arXiv subjects

M. Anselmino

Publications and source records attributed to M. Anselmino.

112 records · Page 7Linked to original sources

arXiv1994

An Interesting Charmonium State Formation and Decay : $p \bar p \to ^1D_2 \to ^1P_1 γ$

Massless perturbative QCD forbids, at leading order, the exclusive annihilation of proton-antiproton into some charmonium states, which, however, have been observed in the $p\bar p$ channel, indicating the significance of higher order and non perturbative effects in the few GeV energy region. The most well known cases are those of the $^1S_0$ ($η_c$) and the $^1P_1$. The case of the $^1D_2$ is considered here and a way of detecting such a state through its typical angular distribution in the radiative decay $^1D_2 \to$ $^1P_1 γ$ is suggested. Estimates of the branching ratio $BR(^1D_2 \to p\bar p)$, as given by a quark-diquark model of the nucleon, mass corrections and an instanton induced process are presented.

hep-ph↗

arXiv1993

$χ_{c2} \to ρρ$ Decay and the $ρ$ Polarization in Inclusive Processes: A Test of Mass Effects

We compute the helicity density matrix of $ρ$ vector mesons produced in the two-body decays of $χ_{c2}$'s in the framework of perturbative QCD, allowing for mass corrections. The $χ_{c2}$'s are inclusively produced in hadronic interactions via gluon fusion and are shown to be strongly polarized. Both the case in which the light quarks inside the final mesons are treated as massless current quarks and the case in which they are seen as constituent massive ones are considered. Our results show significant differences between the two cases; the measurement of the $ρ$ helicity density matrix should allow a test of the importance of these mass effects.

hep-ph↗

arXiv1993

Perturbative QCD Forbidden Charmonium Decays and Gluonia

We address the problem of observed charmonium decays which should be forbidden in perturbative QCD. We examine the model in which these decays proceed through a gluonic component of the $J/Ψ$ and the $η_c$, arising from a mixing of $(c\bar c)$ and glueball states. We give some bounds on the values of the mixing angles and propose the study of the $p \bar{p} \to ϕϕ$ reaction, at $\sqrt{s} \simeq 3$ GeV, as an independent test of the model.

hep-ph↗

arXiv1993

On the Parton Interpretation of Quark Fragmentation into Hadrons with Different Spins

We calculate the spin density matrix of the hadron $h$ created via quark fragmentation in the process $e^-e^+ \to q\bar q \to h + X$. In the case of $h=Λ$ the experimental data could possibly elucidate the problem of $s$-quark contribution to the spin of the $Λ$-hyperon, to be compared with the case of the proton (``spin crisis''). Generally we find that for hadrons with spin 1/2 the parton description, using only probabilities, works much better than for vector particles, since in the former case the non diagonal matrix elements of the hadron spin density matrix are suppressed by a small factor $p_T/(z\sqrt s)$, where $p_T$ is the hadron transverse momentum inside the jet.

hep-ph↗