arXiv subjects

T. Morii

Publications and source records attributed to T. Morii.

At least 19 recordsLinked to original sources

arXiv2022

Measurement of the cluster position resolution of the Belle II Silicon Vertex Detector

The Silicon Vertex Detector (SVD), with its four double-sided silicon strip sensor layers, is one of the two vertex sub-detectors of Belle II operating at SuperKEKB collider (KEK, Japan). Since 2019 and the start of the data taking, the SVD has demonstrated a reliable and highly efficient operation, even running in an environment with harsh beam backgrounds that are induced by the world's highest instantaneous luminosity. In order to provide the best quality track reconstruction with an efficient pattern recognition and track fit, and to correctly propagate the uncertainty on the hit's position to the track parameters, it is crucial to precisely estimate the resolution of the cluster position measurement. Several methods for estimating the position resolution directly from the data will be discussed.

physics.ins-det↗

arXiv2021

The Silicon Vertex Detector of the Belle II Experiment

In 2019 the Belle II experiment started data taking at the asymmetric SuperKEKB collider (KEK, Japan) operating at the Y(4S) resonance. Belle II will search for new physics beyond the Standard Model by collecting an integrated luminosity of 50~ab$^{-1}$. The silicon vertex detector (SVD), consisting of four layers of double-sided silicon strip sensors, is one of the two vertex sub-detectors. The SVD extrapolates the tracks to the inner pixel detector (PXD) with enough precision to correctly identify hits in the PXD belonging to the track. In addition the SVD has standalone tracking capability and utilizes ionization to enhance particle identification in the low momentum region. The SVD is operating reliably and with high efficiency, despite exposure to the harsh beam background of the highest peak-luminosity collider ever built. High signal-to-noise ratio and hit efficiency have been measured, as well as the spatial resolution; all these quantities show excellent stability over time. Data-simulation agreement on cluster properties has recently been improved through a careful tuning of the simulation. The precise hit-time resolution can be exploited to reject out-of-time hits induced by beam background, which will make the SVD more robust against higher levels of background. During the first three years of running, radiation damage effects on strip noise, sensor currents and depletion voltage have been observed, as well as some coupling capacitor failure due to intense radiation bursts. None of these effects cause significant degradation in the detector performance.

physics.ins-det↗

arXiv2009

Derivation of a 1/r^2 potential term for QQ-bar in a potential model

We clarify the difference among potential models so far proposed to explain mass spectra of heavy-light mesons via transformations of the vacuum. Applying our idea to QQ-bar quarkonium, we obtain the extra term, 1/r^2 with positive coefficient, other than non-relativistic potential terms expected for quarkonium.

hep-ph↗

arXiv2008

Viable semi-relativistic quark model of heavy-light systems

The semi-relativistic quark potential model is surprisingly powerful for heavy-light systems if the bound state equation is treated correctly using 1/m_Q expansion with heavy quark mass m_Q. We elucidate the reasons why our semi-relativistic model succeeds in predicting and reproducing all the mass spectra of heavy-light systems so far reported, D/D_s/B/B_s, by reviewing and comparing recent experimental data with the results of our model and others. Especially the mass spectra of the so-called D_{sJ}, i.e., D_{s0}^* and D_{s1}', are successfully reproduced only by our model but not by other models.

hep-ph↗

arXiv2005

Solution to Trouble of D_sJ Particles

Recent discovery of D_sJ particles, which are considered to be a great trouble by experimentalists as well as theorists, had already been resolved by our potential model proposed some time ago by two of us (T.M. and T.M.), in which the Hamiltonian and wave functions are expanded in 1/(heavy quark mass) respecting heavy quark symmetry. Using our model, we explain how narrow states like D_sJ can be realized, predict properties of 0^+ and 1^+ states of B and B_s heavy mesons, and interpret how global SU(3) symmetry seems to be recovered for these 0^+ and 1^+ heavy mesons.

hep-ph↗

arXiv2004

0^+ and 1^+ States of B and B_s Mesons

Predicted masses of J^P=0^+ and 1^+ states of D_{sJ} and D by a potential model proposed some time ago by two of us (T.M. and T.M.), in which the Hamiltonian and wave functions are expanded in 1/m_Q with m_Q heavy quark mass respecting heavy quark symmetry, have recently been confirmed by BaBar and Belle experiments within one percent accuracy. In this Letter, decay modes of 0^+ and 1^+ states of B and B_s mesons are discussed using the predicted masses of this model.

hep-ph↗

arXiv2004

Spinor Operator Giving Both Angular Momentum and Parity

In heavy quark effective theory, heavy mesons which contain a heavy quark (or antiquark) are classified by $s_l^{pi_l}$, i.e., the total angular momentum $s_l$ and the parity $pi_l$ of the light quark degrees of freedom around a static heavy quark. In this case, however, one needs to separately estimate the parity other than the angular momentum of a light quark to describe heavy mesons. A new operator $K$ was proposed some time ago by two of us (T.M. and T.M.). In this Letter, we show that the quantum number $k$ of this operator is enough to describe both the total angular momentum of the light quark degrees of freedom and the parity of a heavy meson, and derive a simple relation between $k$ and $s_l^{pi_l}$.

hep-ph↗

arXiv2003

One-Loop Helicity Amplitudes for Parton Level Virtual Compton Scattering

We calculate the one-loop QCD virtual corrections to all helicity amplitudes for parton level virtual Compton scattering processes. We include the amplitudes both on quark target process $γ^* q\toγq$ and on gluon target process $γ^*g\toγg$. The infrared pole structure of the amplitudes is in agreement with the prediction of Catani's general formalism for the singularities of one-loop amplitudes, while expressions for the finite remainder are given in terms of logarithms and dilogarithms that are real in the physical region.

hep-ph↗

arXiv2003

Production of (super)heavy quarkonia and new Higgs physics at hadron colliders

Based on the two Higgs doublet model, we study the effect of Higgs-boson exchange on the (super)heavy quarkonium \bar QQ, which induces a strong attractive force between a (super)heavy quark Q and an antiquark \bar Q. An interesting application is the decay of (super)heavy quarkonia \bar QQ into a Higgs boson associated with gauge bosons. The criterion for making the \bar QQ bound state is studied. We also show that non-perturbative effects due to gluonic field fluctuations are rather small in such a heavy quark sector. Possible enhancement for productions and decays of \bar QQ bound states made from the fourth generation quark Q is discussed for \bar p p (at the Tevatron) and pp (at the LHC) collisions.

hep-ph↗

arXiv2002

Photoproduction of $ψ'$ as a Test of Color-Octet Model

We have calculated the cross section of $ψ'$ photoproduction at small-$p_{T}$ regions in polarized $γp$ collisions for testing the color-octet model, which is based on NRQCD factorization formalism. We show that the measurement of the two-spin asymmetry of this process might be effective to constrain the value of NRQCD matrix elements.

hep-ph↗

arXiv2002

On search for new Higgs physics in CDF at the Tevatron

We discuss the Higgs boson mass sum rules in the Minimal Supersymmetric Standard Model in order to estimate the upper limits on the masses of stop quarks as well as the lower bounds on the masses of the scalar Higgs boson state. The bounds on the scale of quark-lepton compositeness derived from the CDF Collaboration (Fermilab Tevatron) data and applied to new extra gauge boson search is taken into account. These extra gauge bosons are considered in the framework of the extended SU(2)_h \times SU(2)_l model. In addition, we discuss the physics of rare decays of the MSSM Higgs bosons in both CP-even and CP-odd sectors and also some extra gauge bosons.

hep-ph↗

arXiv2002

Higgs mass sum rule in the light of searching for $Z^{\prime}$ boson at the Tevatron

We discuss the Higgs boson mass sum rules in the Minimal Supersymmetric Standard Model in order to estimate the upper limits on the masses of stop quarks as well as the lower bounds on the masses of the scalar Higgs boson states. The investigation of the bounds on the scale of quark-lepton compositeness derived from the CDF Collaboration (Fermilab Tevatron) data and applied to new extra gauge bosons is taken into account. These extra gauge bosons are considered in the framework of the extended $SU(2)_{h}\times SU(2)_{l}$ interaction model.

hep-ph↗

arXiv2002

Semi-inclusive large-$p_T$ light hadron pair production as a probe of polarized gluons

We propose a new formula for extracting the polarized gluon distribution $Δg$ in the proton from the large--$p_T$ light hadron pair production in deep inelastic semi-inclusive reactions. Though the process dominantly occurs via photon--gluon fusion(PGF) and QCD Compton, we can remove an effect of QCD Compton from the combined cross section of light hadron pair production by using symmetry relation among fragmentation functions and thus, rather clearly extract information of $Δg$.

hep-ph↗

arXiv2001

Perturbative and non-perturbative QCD corrections to wide-angle Compton scattering

We investigate corrections to the handbag approach for wide-angle Compton scattering off protons at moderately large momentum transfer: the photon-parton subprocess is calculated to next-to-leading order QCD and contributions from the generalized parton distribution E} are taken into account. Photon and proton helicity flip amplitudes are non-zero due to these corrections which leads to a wealth of polarization phenomena in Compton scattering. Thus, for instance, the incoming photon asymmetry or the transverse polarization of the proton are non-zero although small.

hep-ph↗

arXiv2001

Extraction of Polarized Gluon Distributions from Large-pt Light Hadron Pair Production

We propose a new formula for extracting the polarized gluon distribution from the large-$p_T$ light hadron pair production for semi-inclusive processes in polarized deep inelastic scattering. In general, a large-$p_T$ hadron pair is produced via photon-gluon fusion(PGF) and QCD Compton at the lowest order of QCD. The PGF gives us a direct information on $Δg$ in the nucleon, while QCD Compton becomes background to the signal process for extracting $Δg$. We show that the contribution from this background, i.e. the QCD Compton process, can be removed by using symmetry relation among fragmentation functions and taking an appropriate combination of various light hadron pair production processes, and thus the double spin asymmetry can be described in terms of $Δg/g$ alone.

hep-ph↗

arXiv2000

The role of secondary Reggeons in central meson production

We estimate the contribution of f_2 trajectory exchange to the central ηand η^\prime production. It is shown that secondary Reggeons may give a large contribution to processes of double diffractive meson production at high energy.

hep-ph↗

arXiv2000

Spectra of Doubly Heavy Quark Baryons

Baryons containing two heavy quarks are treated in the Born-Oppenheimer approximation. Schrödinger equation for two center Coulomb plus harmonic oscillator potential is solved by the method of ethalon equation at large intercenter separations. Asymptotical expansions for energy term and wave function are obtained in the analytical form. Using those formulas, the energy spectra of doubly heavy baryons with various quark compositions are calculated analytically.

hep-ph↗

arXiv2000

Diffractive Lambda_c^+ Productions in Polarized pp Reactions and Polarized Gluon Distribution

To test the model of the polarized gluon distribution $ΔG(x, Q^2)$ in the proton, we propose a new process, diffractive $Λ_c^+$ productions in polarized $pp$ reactions, which will be observed in the forthcoming RHIC and also the proposed HERA-$\vec {\rm N}$ experiments. The spin correlation between the target proton and the $Λ_c^+$ produced in the target fragmentation region largely depends on $ΔG(x, Q^2)$ and thus, the process is quite promising for testing the models of $ΔG(x, Q^2)$.

hep-ph↗