arXiv subjects

Y. Kanazawa

Publications and source records attributed to Y. Kanazawa.

11 recordsLinked to original sources

arXiv2016

Measurement of $σ_{\mathrm{ABS}}$ and $σ_{\mathrm{CX}}$ of $π^+$ on carbon by DUET

The DUET Collaboration reports on the measurements of the absorption ($σ_{\mathrm{ABS}}$) and charge exchange ($σ_{\mathrm{CX}}$) cross sections of positively charged pions on carbon nuclei for the momentum range 201.6 MeV$/c$ to 295.1 MeV$/c$. The uncertainties on the absorption and charge exchange cross sections are $\sim$9.5\% and $\sim$18\%, respectively. The results are in good agreement with previous experiments. A covariance matrix correlating the 5 $σ_{\mathrm{ABS}}$ and 5 $σ_{\mathrm{CX}}$ measured data points is also reported

hep-ex↗

arXiv2015

Measurement of absorption and charge exchange of $π^+$ on carbon

The combined cross section for absorption and charge exchange interactions of positively charged pions with carbon nuclei for the momentum range 200 MeV/c to 300 MeV/c have been measured with the DUET experiment at TRIUMF. The uncertainty is reduced by nearly half compared to previous experiments. This result will be a valuable input to existing models to constrain pion interactions with nuclei.

hep-ex↗

arXiv2001

Polarization in Hadronic ΛHyperon Production and Chiral-Odd Twist-3 Distribution

Polarization of the Λhyperon produced with a large transverse momentum in the unpolarized nucleon-nucleon collision is analyzed in the framework of QCD factorization. We focus on the mechanism in which the soft-gluon component of the chiral-odd spin-independent twist-3 quark distribution E_F(x,x) becomes a source of the polarized quark fragmenting into the polarized Λ. Our simple model estimate for this contribution indicates that it gives rise to a significant Λpolarization at large x_F. This is in parallel with the observation that the soft gluon pole mechanism gives rise to a large single transverse spin asymmetry in the pion production at x_F\to 1.

hep-ph↗

arXiv2000

Hyperon Polarization in Inclusive Hadronic Production

A QCD formula for the polarization in the large-p_T Λhyperon production in the unpolarized nucleon-nucleon collision at large x_F is derived. We focus on the mechanism in which the chiral-odd spin-independent twist-3 quark distribution E_F(x,x) becomes the source of the transversely polarized quarks fragmenting into the polarized Λ. A simple model estimate for that contribution shows the possibility that it gives rise to a sizable Λpolarization.

hep-ph↗

arXiv2000

Estimate of a Chiral-Odd Contribution to Single Transverse-Spin Asymmetry in Hadronic Pion Production

We present an estimate of a chiral-odd contribution to the single transverse-spin asymmetry in the large-$p_T$ pion production in the nucleon-nucleon collision. In this contribution the transversity distribution and the chiral-odd spin-independent twist-3 distribution appear. Because of the smallness of the corresponding hard cross section, this term turned out to be negligible in all kinematic regions compared with the chiral-even contribution.

hep-ph↗

arXiv2000

Chiral-Odd Contribution to Single-Transverse Spin Asymmetry in Hadronic Pion Production

A formula for the single transverse spin asymmetry in the large-$p_T$ pion production in the nucleon-nucleon collision is derived. We focuss on the chiral-odd contribution where the transversity distribution and the chiral-odd spin-independent twist-3 distribution contributes. This contribution is expected to give rise to a large effect at $x_F\to -1$.

hep-ph↗

arXiv1999

A_{LT} in the Nucleon-Nucleon Polarized Drell-Yan Process

We present a leading order (LO) estimate for the longitidinal-transverse spin asymmetry (A_{LT}) in the nucleon-nucleon polarized Drell-Yan process at RHIC and HERA-$\vec{N}$ energies in comparison with A_{LL} and A_{TT}. A_{LT} receives contribution from g_1, the transversity ditribution h_1, and the twist-3 distributions g_T and h_L. For the twist-3 contribution we use the bag model prediction evolved to a high energy scale by the large-N_c evolution equation. We found that A_{LT} (normalized by the asymmetry in the parton level) is much smaller than the corresponding A_{TT}. Twist-3 contribution given by the bag model also turned out to be negligible.

hep-ph↗

arXiv1998

A_{LT} in the polarized Drell-Yan process at RHIC and HERA energies

hep-ph↗

arXiv1998

NLO $Q^2$-evolution of the nucleon's transversity distribution $h_1(x, Q^2)$

We present a calculation of the two-loop anomalous dimension for the transversity distribution $h_1(x,Q^2)$, $γ^{h(1)}_n$, in the MS scheme of the dimensional regularization. Because of the chiral-odd nature, $h_1$ does not mix with the gluon distributions, and thus our result is the same for the flavor-singlet and nonsinglet distributions. At small $n$ (moment of $h_1$), $γ^{h(1)}_n$ is significantly larger than $γ^{f,g(1)}_n$ (the anomalous dimension for the nonsinglet $f_1$ and $g_1$), but approaches $γ^{f,g(1)}_n$ very quickly at large $n$, keeping the relation $γ^{h(1)}_n > γ^{f,g(1)}_n$. This feature is in parallel to the relation between the one-loop anomalous dimension for $f_1$ $(g_1)$ and $h_1$. We also show that this difference in the anomalous dimension between $h_1$ and $g_1$ leads to a drastic difference in the $Q^2$-evolution of those distributions in the small $x$ region.

hep-ph↗

arXiv1997

Next-to-leading order Q^2-evolution of the transversity distribution h_1(x, Q^2)

We present a calculation of the two-loop anomalous dimension for the transversity distribution h_1(x,Q^2), $γ^{h(1)}_n$, in the MS scheme of the dimensional regularization. Due to the chiral-odd nature, h_1 does not mix with the gluon distributions, and thus our result is the same for the flavor-singlet and nonsinglet distributions. At small n (moment of h_1), $γ^{h(1)}_n$ is significantly larger than $γ^{f(1)}_n$ (the anomalous dimension for the nonsinglet f_1), but approaches $γ^{f(1)}_n$ very quickly at large n, keeping the relation $γ^{h(1)}_n > γ^{f(1)}_n$. This feature is in parallel to the relation between the one-loop anomalous dimension for f_1 and h_1.

hep-ph↗

arXiv1997

Bag Model Prediction for the Nucleon's Chiral-odd Twist-3 Distribution h_L(x,Q^2) at High Q^2

We study the Q^2 evolution of the nucleon's chiral-odd twist-3 distribution h_L(x,Q^2) starting from the MIT bag model calculation. A simple GLAP equation for h_L(x,Q^2) obtained at large N_c is used for the Q^2 evolution. The correction due to the finite value of N_c is O(1/N_c^2)\sim 10% level. It turns out that the twist-3 contribution to h_L(x,Q^2) is significantly reduced at Q^2=10 GeV^2 in contrast to the g_2(x,Q^2) case. This is due to the fact that the corresponding anomalous dimension for h_L is larger than that for g_2 at small n (spin).

hep-ph↗