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Yoshimasa Kurihara

Publications and source records attributed to Yoshimasa Kurihara.

At least 37 records · Page 2Linked to original sources

Stochastic Metric Space and Quantum Mechanics

A new idea for the quantization of dynamic systems, as well as space time itself, using a stochastic metric is proposed. The quantum mechanics of a mass point is constructed on a space time manifold using a stochastic metric. A stochastic metric space is, in brief, a metric space whose metric tensor is given stochastically according to some appropriate distribution function. A mathematically consistent model of a space time manifold equipping a stochastic metric is proposed in this report. The quantum theory in the local Minkowski space can be recognized as a classical theory on the stochastic Lorentz-metric-space. A stochastic calculus on the space time manifold is performed using white noise functional analysis. A path-integral quantization is introduced as a stochastic integration of a function of the action integral, and it is shown that path-integrals on the stochastic metric space are mathematically well-defined for large variety of potential functions. The Newton--Nelson equation of motion can also be obtained from the Newtonian equation of motion on the stochastic metric space. It is also shown that the commutation relation required under the canonical quantization is consistent with the stochastic quantization introduced in this report. The quantum effects of general relativity are also analyzed through natural use of the stochastic metrics. Some example of quantum effects on the universe is discussed.

gr-qc↗

Beam polarization effects on top-pair production at the ILC

Full one-loop electroweak-corrections for an $e^-e^+\rightarrow t \bar{t}$ process associated with sequential $t\rightarrow b μν_μ$ decay are discussed. At the one-loop level, the spin-polarization effects of the initial electron and positron beams are included in the total and differential cross sections. A narrow-width approximation is used to treat the top-quark production and decay while including full spin correlations between them. We observed that the radiative corrections due to the weak interaction have a large polarization dependence on both the total and differential cross sections. Therefore, experimental observables that depend on angular distributions such as the forward-backward asymmetry of the top production angle must be treated carefully including radiative corrections. We also observed that the energy distribution of bottom quarks is majorly affected by the radiative corrections.

hep-ph↗

Characteristic classes in general relativity on a modified Poincare curvature bundle

Characteristic classes in space-time manifolds are discussed for both even- and odd-dimensional spacetimes. In particular, it is shown that the Einstein--Hilbert action is equivalent to a second Chern-class on a modified Poincare bundle in four dimensions. Consequently, the cosmological constant and the trace of an energy-momentum tensor become divisible modulo R/Z.

gr-qc↗

One loop effects of natural SUSY in third generation fermion production at the ILC

Within the framework of the Minimal Supersymmetric Standard Model, we investigate the 1-loop effects of supersymmetric particles on the third-generation fermion-pair production at the ILC. Three sets of the SUSY parameters are proposed which are consistent with the observed Higgs mass, the muon g-2, the Dark Matter abundance and the decay branching ratio of B meson. We discuss on the possibility of discovering the signals consistent with SUSY as well as of experimentally distinguishing the proposed sets of SUSY parameters.

hep-ph↗

Compact Four-Dimensional Euclidean-Space Immersed in the Universe

A compact four-dimensional manifold whose metric tensor has a positive determinant (named the "Euclid ball") is considered. The Euclid ball can be immersed in the Minkovskian space (which has the negative determinant) and can exist stably through the history of the universe. Since the Euclid ball has the same solution as the Schwarzschild black hole on its three-dimensional surface, an asymptotic observer can not distinguish them. If large fraction of whole energy of the pre-universe was encapsulated in Euclid balls, they behave as the dark matter in the current universe. Euclid balls already existed at the end of the cosmological inflation, and can have a heavy mass in this model, they can be a seed of supper-massive black-holes, which are necessary to initiate a forming of galaxies in the early universe. The $γ$-ray burst at early universe is also a possible signal of the Euclidean ball.

physics.gen-ph↗

Consistent simulation of non-resonant diphoton production in hadron collisions including associated jet production up to two jets

An event generator for diphoton ($γγ$) production in hadron collisions that includes associated jet production up to two jets has been developed using a subtraction method based on the LLL subtraction. The parton shower (PS) simulation to restore the subtracted divergent components involves both QED and QCD radiation, and QED radiation at very small $Q^{2}$ are simulated by referring to a fragmentation function (FF). The PS/FF simulation has the ability to enforce the radiation of a given number of energetic photons. The generated events can be fed to PYTHIA to obtain particle (hadron)-level event information, which enables us to perform realistic simulations of photon isolation and hadron-jet reconstruction. The simulated events, in which the loop-mediated $gg \rightarrow γγ$ process is involved, reasonably reproduce the diphoton kinematics measured at the LHC. Using the developed simulation, we found that the 2-jet processes significantly contribute to diphoton production. A large 2-jet contribution can be considered as a common feature in electroweak-boson production in hadron collisions although the reason is yet to be understood. Discussion concerning the treatment of the underlying events in photon isolation is necessary for future higher precision measurements.

hep-ph↗

Consistent simulation of direct-photon production in hadron collisions including associated two-jet production

We have developed an event generator for direct-photon production in hadron collisions, including associated two-jet production in the framework of the GR@PPA event generator. The event generator consistently combines $γ$ + 2-jet production processes with the lowest-order $γ$ + jet and photon-radiation (fragmentation) processes from QCD 2-jet production using a subtraction method. The generated events can be fed to general-purpose event generators to facilitate the addition of hadronization and decay simulations. Using the obtained event information, we can simulate photon isolation and hadron-jet reconstruction at the particle (hadron) level. The simulation reasonably reproduces measurement data obtained at the LHC concerning not only the inclusive photon spectrum, but also the correlation between the photon and jet. The simulation implies that the contribution of the $γ$ + 2-jet is very large, especially in low photon-$p_{T}$ ($\lesssim$ 50 GeV) regions. Discrepancies observed at low $p_{T}$, although marginal, may indicate the necessity for the consideration of further higher-order processes. Unambiguous particle-level definition of the photon-isolation condition for the signal events is desired to be given explicitly in future measurements.

hep-ph↗

ME-PS matching in the simulation of multi-jet production in hadron collisions using a subtraction method

The subtraction method for the matching between the matrix element (ME) and parton shower (PS), that has been developed for combining 0-jet and 1-jet production processes in association with electroweak-boson production in hadron collisions, is extended to multi-jet production. In order to include multi-jet MEs, we have to address the soft-gluon divergence together with the collinear divergence. We introduce an approximation which simultaneously reproduces both divergences in a form suitable for application to our subtraction method. The alteration in the subtraction can be compensated by applying an appropriate correction to corresponding non-radiative events. We demonstrate that $W$ + 0, 1, and 2 jet production processes can be consistently combined using the developed matching method.

hep-ph↗

Thermodynamics for Trajectories of a Mass Point

On the basis of information theory, a new formalism of classical non-relativistic mechanics of a mass point is proposed. The particle trajectories of a general dynamical system defined on an (1+n)-dimensional smooth manifold are treated geometrically as dynamical variables. Statistical mechanics of particle trajectories are constructed in a classical manner. Thermodynamic variables are introduced through a partition function based on a canonical ensemble of trajectories. Within this theoretical framework, classical mechanics can be interpreted as an equilibrium state of statistical mechanics. The relationships between classical and quantum mechanics are discussed from this statistical mechanical viewpoint. The maximum entropy principle is shown to provide a unified view of both classical and quantum mechanics.

quant-ph↗

Higgs production in $e$ and real $γ$ collision

We investigate the Standard Model Higgs boson production in $e^-γ$ collision. The electroweak one-loop contributions to the scattering amplitude for $e^-γ\rightarrow e^-H$ are calculated and expressed in analytical form. We analyze the cross section for the Higgs production in $e^-γ$ collision for each combination of polarizations of the initial electron and photon beams. The feasibility of observing the Higgs boson in $e^-+γ\rightarrow e^-+b+{\overline b}$ channel is examined.

hep-ph↗

Advantages of the probability amplitude over the probability density in quantum mechanics

We discuss reasons why a probability amplitude, which becomes a probability density after squaring, is considered as one of the most basic ingredients of quantum mechanics. First, the Heisenberg/Schrodinger equation, an equation of motion in quantum mechanics, describes a time evolution of the probability amplitude rather than of a probability density. There may be reasons why dynamics of a physical system are described by amplitude. In order to investigate one role of the probability amplitude in quantum mechanics, specialized codeword-transfer experiments are designed using classical information theory. Within this context, quantum mechanics based on probability amplitude provides the following: i) a minimum error of the codeword transfer; ii) this error is independent of coding parameters; and iii) nontrivial and nonlocal correlation can be realized. These are considered essential advantages of the probability amplitude over the probability density.

quant-ph↗

Higgs Production in Two-Photon Process and Transition Form Factor

The Higgs production in the two-photon fusion process is investigated where one of the photons is off-shell while the other one is on-shell. This process is realized in either electron-positron collision or electron-photon collision where the scattered electron or positron is detected (single tagging) and described by the transition form factor. We calculate the contributions to the transition form factor of the Higgs boson coming from top-quark loops and W-boson loops. We then study the $Q^2$ dependence of each contribution to the total transition form factor and also of the differential cross section for the Higgs production.

hep-ph↗

Classical Information-Theoretical View of Physical Measurements and Generalized Uncertainty Relations

General characterizations of physical measurements are discussed within the framework of the classical information theory. The uncertainty relation for simultaneous measurements of two physical observables is defined in this framework for generalized dynamic systems governed by a Sturm--Liouville type of equation of motion. In the first step, the reduction of Kennard--Robertson type uncertainties due to boundary conditions with a mean-square error is discussed quantitatively with reference to the information entropy. Several concrete examples of generalized uncertainty relations are given. Then, by considering disturbance effects, a universally valid uncertainty relation is investigated for the generalized equation of motion with a certain boundary condition. Necessary conditions for violation (reduction) of the Heisenberg-type uncertainty relation are discussed in detail. The reduction of the generalized uncertainty relation due to the boundary condition is then tested experimentally by re-analyzing data for measured electron densities in a hydrogen molecule encapsulated in a fullerene C60 cage.

quant-ph↗

Three Essential Reasons Why Nature Chose Quantum Mechanics

We discuss the reason why quantum mechanics is chosen as the most basic law of nature. Probability amplitude, which becomes a probability density after square it, is considered as one of the most essential ingredient of quantum mechanics. Code transfer experiments based on the probability amplitude is proved to be i) error of code transfer is minimum, ii) that error is independent of coding parameters and iii) non-trivial and non-local correlation is possible.

quant-ph↗

Classical-Information Theoretical View of Physical Measurements and Generalized Uncertainty Relations

General characterization of physical measurements is discussed within the framework of a classical information theory. Uncertainty relation for simultaneous measurements of two physical observables is defined in this framework for generalized dynamic systems controlled under general kinds of equations of motion. We have treated only a mean-square error of the Gauss(-like) distributions in this report. Lessening of the Kennard-Robertson type uncertainties due to boundary conditions are quantitatively discussed using the information entropy.

quant-ph↗

A Universally Valid Uncertainty Relation Revisited

A universally valid uncertainty relation proposed by Ozawa is re-investigated under for the generalized equation of motion with some boundary condition. Necessary conditions for violation (lessening) of the Heisenberg-type uncertainty relation is discussed in detail. An experimental test of lessening of the generalized uncertainty relation due to the boundary condition is shown by re-analyzing the data measuring electron densities of hydrogen molecule encapsulated in a cage of fullerene C60.

quant-ph↗

A feasibility study of the measurement of Higgs pair creation at a Photon Linear Collider

We studied the feasibility of the measurement of Higgs pair creation at a Photon Linear Collider (PLC). From the sensitivity to the anomalous self-coupling of the Higgs boson, the optimum $γγ$ collision energy was found to be around 270 GeV for a Higgs mass of 120 GeV/$c^2$. We found that large backgrounds such as $γγ\rightarrow W^+W^-, ZZ,$ and $b\bar{b}b\bar{b}$, can be suppressed if correct assignment of tracks to parent partons is achieved and Higgs pair events can be observed with a statistical significance of $\sim 5 σ$ by operating the PLC for 5 years.

hep-ph↗

Consistent simulation of non-resonant diphoton production at hadron collisions with a custom-made parton shower

We have developed a Monte Carlo event generator for non-resonant diphoton ($γγ$) production at hadron collisions in the framework of GR@PPA, which consistently includes additional one-jet production. The jet-matching method developed for initial-state jet production has been extended to the final state in order to regularize the final-state QED divergence in the $qg \rightarrow γγ+ q$ process. A QCD/QED-mixed parton shower (PS) has been developed to complete the matching. The PS has the capability of enforcing hard-photon radiation, and small-$Q^{2}$ photon radiations that are not covered by the PS are supplemented by using a fragmentation function. The generated events can be passed to general-purpose event generators in order to perform the simulations down to the hadron level. Thus, we can simulate the isolation requirements that must be applied in experiments at the hadron level. The simulation results are in reasonable agreement with the predictions from RESBOS and DIPHOX. The simulated hadron-level events can be further fed to detector simulations in order to investigate the detailed performance of experiments.

hep-ph↗