Summary of academic achievements Shunzo Kumano

I have been working in theoretical hadron and nuclear physics. My studies are classiﬁed into

two categories. One is on properties of hadron resonances, and the other is on structure functions

of hadrons and nuclei. In the following, I explain several major results. The detailed explanation

of my research history is given in my home page at https://research.kek.jp/people/kumanos/

(→ Research history).

Hadron resonances

1. ∆ electromagnetic moments: We prop osed that accurate determination of the ∆ mag-

netic moment can be done by the polarized pion-nucleon bremsstrahlung (Heller, Kumano,

Martinez, Moniz in 1987). Based on this idea, experimentalists proposed an experiment at

the Paul Scherrer Institute, and they determined µ

∆

++

= 1.64 µ

p

[A. Bosshard et al., Phys.

Rev. Lett. 64 (1990) 2619].

2. Exotic hadron candidates f

0

(980) and a

0

(980): We showed that ϕ radiative decays

into the scalar mesons f

0

(980) and a

0

(980) could provide important clues on their internal

structure (Close, Isgur, Kumano in 1993) by showing that the radiative decay widths varied

widely depending on their substructures, q¯q, qq ¯q ¯q, K

¯

K, and glueball.

3. Constituent counting rule for exotic hadrons: For ﬁnding internal conﬁgurations of

exotic hadron candidates, we proposed to use hadron tomography by three-dimensional struc-

ture functions and constituent counting rule of perturbative QCD (Chang, Kawamura, Ku-

mano, Sekihara in 2013–2016).

Structure functions

1. b

1

sum rule: We proposed a sum rule for the tensor-polarized structure function b

1

(Close,

Kumano in 1990). This sum rule was investigated experimentally by the HERMES collabo-

ration [A. Airapetian et al., Phys. Rev. Lett. 95 (2005) 242001], and they obtained a ﬁnite

sum, which indicated an existence of ﬁnite tensor-polarized antiquark distributions.

2. Anomalous dimensions of h

1

: Two-lo op anomalous dimensions of chiral-odd structure

function h

1

were calculated in the minimal subtraction scheme by using the dimensional

regularization and Feynman gauge (Kumano, Miyama in 1997). Because of this work, it

became possible to investigate h

1

in the next-to-leading-order level.

3. Flavor asymmetric antiquark distributions: We showed that meson-cloud eﬀects could

explain the Gottfried-sum-rule violation and the ﬂavor asymmetric antiquark distribution

¯u −

¯

d in the nucleon (Kumano in 1991). A theoretical and experimental summary paper was

written on this topic in Physics Reports (Kumano in 1998).

4. Global analyses of parton distribution functions: From global analyses of world high-

energy hadron cross section data, we determined polarized parton distribution functions

(PDFs), nuclear PDFs, and fragmentation functions (Asymmetry Analysis Collaboration,

Hirai, Kumano, Miyama, Nagai, Sudoh in 2000-2016). We provided useful codes for calcu-

lating obtained functions and they were used as one of the world standard models.

5. Gravitational form factors of hadron: We determined generalized distribution ampli-

tudes (GDAs) of the pion from KEKB measurements on the γ

∗

γ → π

0

π

0

cross section.

From the GDAs, we obtained gravitational form factors Θ

1

and Θ

2

and estimated the mass

and mechanical rms radii (Kumano, Song, Teryaev in 2018). This is the ﬁrst report on the

gravitational radius of a hadron from actual experimental measurements.