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T. Morii

Publications and source records attributed to T. Morii.

35 records · Page 2Linked to original sources
arXiv2000

Polarized Parton Distribution Functions in the Nucleon

Polarized parton distribution functions are determined by using world data from the longitudinally polarized deep inelastic scattering experiments. A new parametrization of the parton distribution functions is adopted by taking into account the positivity and the counting rule. From the fit to the asymmetry data A_1, the polarized distribution functions of u and d valence quarks, sea quarks, and gluon are obtained. The results indicate that the quark spin content is ΔΣ=0.20 and 0.05 in the leading order (LO) and the next-to-leading-order (NLO) MS-bar scheme, respectively. However, if x dependence of the sea-quark distribution is fixed at small x by "perturbative QCD" and Regge theory, it becomes ΔΣ=0.24 ~ 0.28 in the NLO. The small-x behavior cannot be uniquely determined by the existing data, which indicates the importance of future experiments. From our analysis, we propose one set of LO distributions and two sets of NLO ones as the longitudinally-polarized parton distribution functions.

hep-ph↗
arXiv1999

Is there window for "supersoft" Pomeron in $J/ψ$ photoproduction at low energy?

The low energy $J/ψ$ photoproduction cross-section has been studied on the basis of the Pomeron model. To incorporate the discrepancy between experimental data and the predictionns by the conventional models, i.e. the sum of the soft Pomeron with intercept 1.08 and the hard Pomeron with intercept 1.418, a Regge trajectory associated with a scalar meson (f,a) exchange which we call "supersoft" Pomeron, is introduced additionally. To distinguish between the conventional model and this new additional Pomeron, observations related to other polarization observables in upcoming polarized experiments are discussed.

hep-ph↗
arXiv1999

Polarized light flavor sea-quark asymmetry in polarized semi-inclusive processes

We propose new formulas for extracting a difference of the polarized light sea-quark density, $Δ\bar d(x)-Δ\bar u(x)$, from polarized deep-inelastic semi-inclusive data. We have estimated the value of it from the present experimental data measured by SMC and HERMES groups. Although the data might suggest a violation of polarized light flavor sea-quark symmetry, the precision of the present data is not enough for confirming it.

hep-ph↗
arXiv1999

Pomeron Fusion and Central $η$ and $η'$ Meson Production

The contribution of pomeron fusion to the cross section of $η$ and $η'$ productions in double-diffractive scattering has been calculated within the Donnachie-Landshoff model of pomeron. It is shown that the double pomeron exchange mechanism does not explain the full set of the recent data of WA102 Collaboration, though it might not be inconsistent with $η'$ productions.

hep-ph↗
arXiv1998

A New Parametrization of Polarized Parton Distribution Functions

Requiring the positivity and counting rule, we propose a new parametrization of the polarized parton distribution which reproduce the data well. We found that the NLO analysis is absolutely necessary to extract the correct information on the polarized gluon distributions. The calculated results of $xΔd_v(x)$ and $Δd_v(x)/d_v(x)$ seem to be consistent with the SMC data at $Q^2=$10GeV$^2$.

hep-ph↗
arXiv1998

Heavy Quark Productions with Spin

Heavy quark productions in high energy polarized scatterings are reviewed from a personal point of view. After mentioning why heavy quark physics is so interesting, I concentrate on two rather specific subjects: (1) polarized $Λ_{c}^{+}$ productions in deep inelastic $\ell p$ scatterings and (2) $ψ^{\prime}$ productions in polarized $pp$ collisions. The first one is an interesting process for extracting the polarized gluon in the proton and the second one may give another test of the color-octet model of heavy quarkonium productions in high energy collisions.

hep-ph↗
arXiv1997

$ψ'$ productions as a test of color-octet mechanism

To test the color-octet model of heavy quarkonium productions, we propose $ψ'$-productions at small-$p_T$ regions in polarized $pp$ collisions for the forthcoming RHIC polarized experiments, whose experimental test at $\sqrt s=50$ GeV might be very promising.

hep-ph↗
arXiv1997

Review from theoretician

The talks presented at the conference are summarized from an angle of a particle theorist. After presenting a personal impression on the conference, particular emphasis is placed on the spin structure of nucleons and symmetry breaking test.

hep-ph↗
arXiv1997

Hard Processes with Spin-Dependent Parton Distributions

To test a possible color-octet contribution of heavy quarkonium productions, we propose $ψ$'-productions for small-$p_T$ regions, where the color-singlet $ψ$' state cannot be produced by the gluon-gluon fusion owing to charge conjugation. We also point out that these processes are very useful to deduce informations of spin-dependent gluon distributions $Δg$.

hep-ph↗
arXiv1997

Semi-inclusive Lambda_c^+ Leptoproductions and Polarized Gluon Distributions

In order to extract the behavior and magnitude of the spin-dependent gluon distribution, we propose a semi-inclusive $Λ_c^+$ production using unpolarized lepton beams and polarized proton targets. The correlation between the target proton spin and the spin of $Λ_c^+$ produced in the target fragmentation region might be very effective for testing various models of polarized gluons.

hep-ph↗
arXiv1996

Delta s density in a proton and unpolarized lepton - polarized proton scatterings

It is shown that the parity--violating deep--inelastic scatterings of unpolarized charged leptons on polarized protons, $\ell^{\mp} + \vec P\to \stackrel{\scriptscriptstyle(-)}{ν_{\ell}} + X$, could provide a sensitive test for the behavior and magnitude of the polarized strange--quark density in a proton. Below charm threshold these processes are also helpful to uniquely determine the magnitude of individual polarized parton distributions.

hep-ph↗
arXiv1995

Polarized Gluons in the Nucleon

QCD suggests that gluons in the nucleon play an important role in {\it so-called} ``the proton spin problem''. In this talk, the behavior of the polarized gluon distribution in the nucleon is discussed by using the positivity condition of distribution functions together with the unpolarized and polarized experimental data.

hep-ph↗
arXiv1995

TWO--SPIN ASYMMETRY OF HEAVY QUARKONIA PRODUCTIONS AT RHIC ENERGY

Hadroproductions of charmonium and bottomonium $χ_J$ in polarized $pp$ collisions at RHIC energies are studied. Two--spin asymmetries $A_{LL}^{χ_J}(pp)$ for these reactions are very good parameters for examining the polarized gluon distributions in a proton.

hep-ph↗
arXiv1994

The Shape of Polarized Gluon Distributions

The recent high precision SMC data on polarized $μp$ scatterings have again confirmed that very little of the proton spin is carried by quarks. To unravel the mystery of the proton spin structure, it is quite important to know the behavior of the polarized gluon distribution. By using the positivity condition of distribution functions together with the unpolarized and polarized experimental data, we restrict the $x$ dependence of the polarized gluon distribution.

hep-ph↗
arXiv1994

A Way to Measure Polarized Gluon Distributions

Effects of the spin-dependent gluon distributions on J/$ψ$ productions in polarized ep and pp collisions are investigated. These productions serve as a very clean probe of the spin-dependent gluon distributions in a proton.

hep-ph↗
arXiv1994

How to probe the spin-dependent gluon distributions

Two-spin asymmetries $A_{LL}^{π^0}$ are calculated for various types of spin-dependent gluon distributions. It is concluded that the E581/704 data on $A_{LL}^{π^0}$ do not necessarily rule out the large gluon polarization but restrict severely the $x$ dependence of its distribution. Moreover, $A_{LL}^{J/ψ}$ are calculated for the forthcoming test of spin-dependent gluon distributions.

hep-ph↗