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Toshiyuki Morii

Publications and source records attributed to Toshiyuki Morii.

At least 19 recordsLinked to original sources
arXiv2016

Approximate degeneracy of heavy-light mesons with the same $L$

Careful observation of the experimental spectra of heavy-light mesons tells us that heavy-light mesons with the same angular momentum $L$ are almost degenerate. The estimate is given how much this degeneracy is broken in our relativistic potential model, and it is analytically shown that expectation values of a commutator between the lowest order Hamiltonian and ${\vec L}^{~2}$ are of the order of $1/m_Q$ with a heavy quark mass $m_Q$. It turns out that nonrelativistic approximation of heavy quark system has a rotational symmetry and hence degeneracy among states with the same $L$. This feature can be tested by measuring higher orbitally and radially excited heavy-light meson spectra for $D/D_s/B/B_s$ in LHCb and forthcoming BelleII.

hep-ph↗
arXiv2010

Mixing angle between $^3P_1$ and $^1P_1$ in HQET

Some claim that there are two independent mixing angles ($θ= 35.3^\circ$, $-54.7^\circ$) between $^3P_1$ and $^1P_1$ states of heavy-light mesons in heavy quark symmetric limit, and others claim there is only one ($θ= 35.3^\circ$). We clarify the difference between these two and suggest which should be adopted. General arguments on the mixing angle between $^3L_L$ and $^1L_L$ of heavy-light mesons are given in HQET and a general relation is derived in heavy quark mass limit as well as that including the first order correction in $1/m_Q$.

hep-ph↗
arXiv2008

Is the Z^+(4430) a radially excited state of D_s?

We present the interpretation that the recently discovered Z^+(4430) by the Belle Collaboration can be a radial excitation of the cs-bar state. We give an explicit cs-bar candidate for this state by calculating the mass value in our semirelativistic quark potential model and also give a natural interpretation on the reason why the decay mode Z-> J/ψπ^+ has not yet been seen while Z-> ψ' πcan be seen.

hep-ph↗
arXiv2007

Study of Structure of the Mass Gap between Two Spin Multiplets

Studying our semirelativistic potential model and the numerical results, which succeeds in predicting and reproducing recently discovered higher resonances of $D$, $D_s$, $B$, and $B_s$, we find a simple expression for the mass gap between two spin multiplets of heavy-light mesons, $(0^-,1^-)$ and $(0^+,1^+)$. The mass gap between chiral partners defined by $ΔM=M(0^+)-M(0^-)$ and/or $M(1^+)-M(1^-)$ is given by $ΔM=M(0^+)-M(0^-)=M(1^+)-M(1^-)\approx Λ_{\rm Q}-m_q$ in the limit of heavy quark symmetry. We also study the case including $1/m_Q$ corrections.

hep-ph↗
arXiv2007

Structure of Mass Gap between Two Spin Multiplets

Studying our semirelativistic potential model and the numerical results, which succeeds in predicting and reproducing recently discovered higher resonances of $D$, $D_s$, $B$, and $B_s$, we find a simple expression for the mass gap between two spin multiplets of heavy-light mesons, $(0^-,1^-)$ and $(0^+,1^+)$. The mass gap between chiral partners defined by $ΔM=M(0^+)-M(0^-)$ and/or $M(1^+)-M(1^-)$ is given by $ΔM=M(0^+)-M(0^-)=M(1^+)-M(1^-)\approx Λ_{\rm Q}-m_q$ in the limit of heavy quark symmetry, and including $1/m_Q$ corrections, we have $ΔM\approx Λ_{\rm Q}-m_q+(1.28\times 10^{5}+4.26\times 10^{2}\cdot m_q)/m_Q$ with $Λ_{\rm Q}\approx 300$ MeV, a light quark mass $m_q$, and a heavy quark mass $m_Q$. This equation holds both for $D$ and $D_s$ heavy mesons. Our model calculations for the $B$ and $B_s$ also follow this formula.

hep-ph↗
arXiv2007

Radial Excitations of Heavy Mesons

Recent discovery of D_s states suggests existence of radial excitations. Our semirelativistic quark potential model succeeds in reproducing these staes within one to two percent of accuracy compared with the experiments, D_s0(2860) and D_s^*(2715), which are identified as 0^+ and 1^- radial excitations (n=2). We also present calculations of radial excitations for B/B_s heavy mesons. Relation between our formulation and the modified Goldberger-Treiman relation is also described.

hep-ph↗
arXiv2007

New Heavy-Light Mesons $Q\bar q$

We succeed in reproducing the $\ell=1$ $B$ mesons, $B_1(5720)$, $B_2^*(5745)$, and $B_{s2}^*(5839)$ that are recently reported by D0 and CDF, by using our semirelativistic quark potentila model, which also succeeded in predicting the mass spectra of the narrow $D_{sJ}$ as well as broad $D_0^*(0^+)$ and $D_1'(1^+)$ particles a couple of years ago. Mass of higher excited states ($\ell=1, 2$) of $B$ and $B_s$ mesons, which are not yet observed, is also predicted at the first order in $p/m_b$. We find the corresponding $B_{sJ}$ are below $BK/B^*K$ threshold and should have narrow decay widths contrary to most other predictions. Also already established states ($\ell=0$ and $\ell=1$) of $D$, $D_s$, $B$, and $B_s$ heavy mesons are simultaneously reproduced in good agreement with experimental data within one percent of accuracy. To calculate these $D/D_s$ and $B/B_s$ heavy mesons we use different values of strong coupling $α_s$ which conforms to a notion of running coupling.

hep-ph↗
arXiv2006

Study of $B\to K^* ρ, K^*ω$ Decays with Polarization in Perturbative QCD Approach

The $B \to K^{*}ρ$, $ K^{*}ω$ decays are useful to determine the CKM angle $ϕ_3=γ$. Their polarization fractions are also interesting since the polarization puzzle of the $B\to ϕK^*$ decay. We study these decays in the perturbative QCD approach based on $k_T$ factorization. After calculating of the non-factorizable and annihilation type contributions, in addition to the conventional factorizable contributions, we find that the contributions from the annihilation diagrams are crucial. They give dominant contribution to the strong phases and suppress the longitudinal polarizations. Our results agree with the current existing data. We also predict a sizable direct CP asymmetries in $B^+ \to K^{*+}ρ^0$, $B^0 \to K^{*+}ρ^-$, and $B^+ \to K^{*+}ω$ decays, which can be tested by the oncoming measurements in the B factory experiments.

hep-ph↗
arXiv2005

Probing Polarized Gluon Distributions through Charmed Hadron Production in Polarized pp Collisions at BNL--RHIC Energy

In order to extract information about behavior of polarized gluons in the nucleon, charmed hadron productions, i.e. D* meson and Lambda_c baryon productions, are studied in polarized pp reactions at BNL-RHIC energy. For these processes, the spin correlation asymmetry D_{LL} between the target proton and the produced charmed hadron, and its statistical sensitivity delta D_{LL} are calculated. From analyses on these processes, we found that the pseudo-rapidity distribution of D_{LL} in the limited transverse momentum region is quite effective for distinguishing the model of polarized gluons as well as the model of spin-dependent fragmentation functions.

hep-ph↗
arXiv2002

Charmed Hadron Production in Polarized pp Collisions

To extract information about polarized gluons in the proton, production of charmed hadrons, in particular, Λ_c^+ baryon in pp collisions was studied. We calculated the transverse momentum distribution and the pseudo-rapidity distribution of the spin correlation asymmetry A_{LL} between the initial proton and the produced Λ_c^+. Those statistical sensitivities were also calculated under the condition of RHIC experiment. We found that the pseudo-rapidity distribution of A_{LL} is promising for testing the model of polarized gluons in the proton and also the spin-dependent fragmentation model of a charm quark decaying into Λ_c^+ baryon.

hep-ph↗
arXiv2002

Lambda_c^+ production in polarized pp scattering and polarized gluon distribution

To extract information about the polarized gluon distribution, $\dg$, in the nucleons, we propose Lambda_c^+ productions in polarized pp scattering, p + \vec{p} \to \vec{Lambda_c^+} + X, which will be observed at RHIC experiment starting soon. For this process, we have calculated the spin correlation differential cross section, dΔσ/d\pt, and the spin correlation asymmetry defined by \A_ll \equiv [ d Δσ/ d \pt ] / [ d σ/ d\pt ]. We have found that the \A_ll is sensitive to the polarized gluon distribution in the nucleon and thus the process is promising for testing ΔG(x,Q^2).

hep-ph↗
arXiv2002

Single Diffractive Lambda_c^+ Production in Polarized pp Scattering with Polarized Gluon Distribution in the Proton

Based on the hard-scattering factorization which decomposes the diffractive structure function into a pomeron flux and a pomeron structure function, we study the single diffractive Lambda_c^+ production in polarized pp scattering: p + p -> p + Lambda_c^+ + X, which will be observed at forthcoming RHIC experiment. By analyzing the cross section and correlation of the spin polarization between the initial proton and produced Lambda_c^+, we found that the process is quite effective for testing both hard-scattering factorization and models of the polarized gluon distribution in the proton.

hep-ph↗
arXiv2002

Charmed Hadron Production at RHIC

To extract information about polarized gluon distribution in the proton, charmed hadron, actually Λ_c^+, productions at RHIC experiment are studied. We found that the spin correlation asymmetry between the initial proton and the produced Λ_c^+ is enable us to distinguish parameterization models of polarized gluons.

hep-ph↗
arXiv2001

Charmed Hadron Production in Neutrino Reactions and Polarized s-quark Distribution

In order to obtain information about the polarized strange quark distribution, we studied the semi-inclusive $Λ_c / \barΛ_c$ production in neutrino and polarized proton collisions. We found that these reactions are effective to clearly extract the polarization of strange quark by measuring the spin correlation between the target proton and the produced $Λ_c / \barΛ_c$ baryon.

hep-ph↗
arXiv2001

Electroproduction of psi' and polarized gluon distribution in a proton

In order to get information about the polarized gluon distribution in a proton, we studied the electroproduction of ψ' in polarized electron and polarized proton collisions in the framework of the NRQCD factorization approach. The value of the cross section dΔσ/ dp_T^2 for color-octet mechanism is about 5 times larger than that for color-singlet one, and it might be another test of the color-octet model if the polarized gluon distribution Δg(x) is well known. Furthermore, we found that this reaction is quite effective for testing the model of gluon polarization by measuring the double spin asymmetry A_{LL} for the initial electron and proton. Though the shape of p_T^2 distribution of A_{LL} is quite similar for the production mechanism with color-octet and color-singlet, we can see a big difference in A_{LL} among various models of the polarized gluon distribution function Δg(x).

hep-ph↗
arXiv2001

On a possible manifestation of f_1 trajectory in J/psi photoproduction

We analyze a possible manifestation of f_1-trajectory in elastic J/psi photoproduction at high energy and large momentum transfer. Inspite of the small contribution of f_1-trajectory in total cross sections, it becomes significant in various spin observables. In particular, we show that the crucial test for f_1-exchange can be made by measuring the single beam- and double parity- and beam-target asymmetries at large momentum transfers, where a strong deviation from the exchange of conventional Pomerons is expected. This effect is caused by the interference of natural (Pomeron) and unnatural (f_1) parity exchange parts of amplitude in the region where their contributions become comparable to each other and might be interesting to observe in forthcoming experiments, if feasible. .

hep-ph↗
arXiv2000

Probing nucleon strangeness in phi electroproduction

We investigate $ϕ$ meson electroproduction to probe the hidden strangeness content of the nucleon. We found that even a small amount of the $s\bar{s}$ admixture in the nucleon wavefunction can lead to a significant change in several double polarization asymmetries in $ϕ$ electroproduction, which can be tested experimentally at current electron facilities.

nucl-th↗