Short summary of research 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/. The total number of

citations is 7685 (7645) by Inspire (Google) on March 23, 2024 and 6216 for journal publications.

Hadron resonances

1. ∆ electromagnetic moments: We proposed that accurate determination of the ∆ magnetic

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

[A. Bosshard et al., Phys. Rev. Lett. 64 (1990)

2619].

2. Exotic hadron candidates f

(980) and a

(980): We showed that ϕ radiative decays into the

scalar mesons f

(980) and a

(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 structure functions

and constituent counting rule of perturbative QCD (Chang, Kawamura, Kumano, Sekihara in 2013–

2016).

Structure functions

1. b

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

(Close, Ku-

mano in 1990). This sum rule was investigated experimentally by the HERMES collaboration

[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

: Two-loop anomalous dimensions of chiral-odd structure function

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

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 calculating obtained functions and they

were used as one of the world standard models.

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

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

∗

γ → π

cross section. From the GDAs,

we obtained gravitational form factors Θ

and Θ

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.

6. Structure functions of spin-1 hadrons: Possible transverse-momentum-dependent parton dis-

tribution functions (TMDs) were shown for for spin-1 hadrons by considering the Hermiticity and

parity invariance, and useful twist-2 and equation-of-motion relations were derived for the spin-1

PDFs (Kumano, Song in 2021-2022).