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Kensuke Homma

Publications and source records attributed to Kensuke Homma.

33 records · Page 2Linked to original sources
arXiv2017

Exploring pseudo-Nambu--Goldstone bosons by stimulated photon colliders in the mass range 0.1~eV to 10~keV

Searching for pseudo-Nambu--Goldstone bosons (pNGBs) in weak-coupling domains is crucial for understanding the dark components in the universe. We propose searching for pNGBs coupled to two photons in the mass range from 0.1~eV to 10~keV. This could provide opportunities to test string-theory-based pNGBs beyond the GUT scale $M \sim 10^{16}$~GeV included in the weak coupling proportional to $M^{-1}$. We provide formulae that are applicable to photon--photon scattering via a pNGB resonance exchange with a stimulation process in an asymmetric head-on photon--photon collider by mixing three laser pulses in laboratory experiments. We discuss the quantum electrodynamic effects on the pNGB exchange in the same mass--coupling domain as a background process from the standard model. We find that a large unexplored mass--coupling domain is accessible by combining existing laser facilities, including free-electron lasers.

hep-ph↗
arXiv2015

Testing helicity dependent $γγ\rightarrowγγ$ scattering in the region of MeV

Light-by-light scatterings contain rich information on the photon coupling to virtual and real particle states. In the context of quantum electrodynamics (QED), photons can couple to a virtual $e^+e^-$ pair. Photons may also couple to known resonance states in the context of quantum chromodyanmics and electroweak dynamics in higher energy domains and possibly couple to unknown resonance states beyond the starndard model. The perturbative QED calculations manifestly predict the maximized cross section at the MeV scale, however, any example of the exact real-photon - real-photon scattering has not been observed hitherto. Hence, we propose the direct measurement with the maximized cross-section at the center-of-mass system energy of 1-2 MeV to establish the firm footing at the MeV scale. Given currently state-of-the-art high power lasers, the helicity dependent elastic scattering may be observed at a reasonable rate, if a photon-photon collider exploiting $γ$-rays generated by the inverse nonlinear Compton process with electrons delivered from laser-plasma accelerators (LPA) are properly designed. We show that such verification is feasible in a table-top scale collider which may be an unprecedented breakthrough in particle accelerators for basic physics research in contrast to energy frontier colliders.

hep-ex↗
arXiv2015

Search for sub-eV scalar and pseudoscalar resonances via four-wave mixing with a laser collider

The quasi-parallel photon-photon scattering by combining two-color laser fields is an approach to produce resonant states of low-mass fields in laboratory. In this system resonances can be probed via the four-wave mixing process in the vacuum. A search for scalar and pseudoscalar fields was performed by combining 9.3 $μ$J/0.9 ps Ti-Sapphire laser and 100 $μ$J/9 ns Nd:YAG laser. No significant signal of four-wave mixing was observed. We provide the upper limits on the coupling-mass relation for scalar and pseudoscalar fields, respectively, at a 95\% confidence level in the mass region below 0.15~eV.

hep-ex↗
arXiv2014

The first search for sub-eV scalar fields via four-wave mixing at a quasi-parallel laser collider

A search for sub-eV scalar fields coupling to two photons has been performed via four-wave mixing at a quasi-parallel laser collider for the first time. The experiment demonstrates the novel approach to search for resonantly produced sub-eV scalar fields by combining two-color laser fields in the vacuum. The aim of this paper is to provide the concrete experimental setup and the analysis method based on specific combinations of polarization states between incoming and outgoing photons, which is extendable to higher intensity laser systems operated at high repetition rates. No significant signal of four-wave mixing was observed by combining a $0.2μ$J/0.75ns pulse laser and a 2mW CW laser on the same optical axis. Based on the prescription developed for this particular experimental approach, we obtained the upper limit at a confidence level of 95% on the coupling-mass relation.

hep-ex↗
arXiv2013

Measurability of phi, omega and rho mesons via di-electron decays in high-temperature states produced in heavy-ion collisions

We discuss measurability of phi, omega and rho mesons via di-electron decays in high-temperature states produced in heavy-ion collisions, equivalently at different pion multiplicities per heavy-ion collision dN_{pi^{0} + pi^{+-}}/dy = 1000 and 2700 intended for the most central Au+Au collisions at sqrt(s_{NN}) = 200 GeV (RHIC) and the most central Pb+Pb collisions at sqrt(s_{NN}) = 5.5 TeV (LHC), by evaluating the signal-to-background ratios and the statistical significance for the idealized detection system in the numerical simulation. The simulation study provides a guideline to be applicable to a concrete detector design by focusing on only the key experimental issues relevant to the measurement of di-electrons. The results suggest that there are realizable parameter ranges to measure light vector mesons via di-electrons with the reasonable significance level, even in the highest multiplicity case.

nucl-ex↗
arXiv2012

Sensitivity to Dark Energy candidates by searching for four-wave mixing of high-intensity lasers in the vacuum

Theoretical challenges to understand Dark Matter and Dark Energy suggest the existence of low-mass and weakly coupling fields in the universe. The quasi-parallel photon-photon collision system (QPS) can provide chances to probe the resonant production of these light dark fields and the induced decay by the coherent nature of laser fields simultaneously. By focusing high-intensity lasers with different colors in the vacuum, new colors emerge as the signature of the interaction. Because four photons in the initial and final states interplay via the dark field exchange, this process is analogous to four-wave mixing in quantum optics, where the frequency sum and difference among the incident three waves generate the fourth wave with a new frequency via the nonlinear property of crystals. The interaction rate of the four-wave mixing process has the cubic dependence on the intensity of each wave. Therefore, if high-intensity laser fields are given, the sensitivity to the weakly coupling of dark fields to photons rapidly increases over the wide mass range below sub-eV. Based on the experimentally measurable photon energies and the linear polarization states, we formulate the relation between the accessible mass-coupling domains and the high-intensity laser parameters, where the effects of the finite spectrum width of pulse lasers are taken into account. The expected sensitivity suggests that we have a potential to explore interactions at the Super-Planckian coupling strength in the sub-eV mass range, if the cutting-edge laser technologies are properly combined.

hep-ph↗
arXiv2011

An approach toward the laboratory search for the scalar field as a candidate of Dark Energy

The observed accelerating universe indicates the presence of Dark Energy which is probably interpreted in terms of an extremely light gravitational scalar field. We suggest a way to probe this scalar field which contributes to optical light-by-light scattering through the resonance in the quasi-parallel collision geometry. As we find, the frequency-shifted photons with the specifically chosen polarization state can be a distinct signature of the scalar-field-exchange process in spite of the extremely narrow width due to the gravitationally weak coupling to photons. Main emphasis will be placed in formulating a prototype theoretical approach, then showing how the weak signals from the gravitational coupling are enhanced by other non-gravitational effects at work in laser experiments.

gr-qc↗
arXiv2011

Probing the semi-macroscopic vacuum by higher-harmonic generation under focused intense laser fields

The invention of the laser immediately enabled the detection of nonlinear photon-matter interactions, as manifested for example by Franken et al.'s detection of second-harmonic generation. With the recent advancement in high-power, high-energy lasers and the examples of nonlinearity studies of the laser-matter interaction by virtue of properly arranging lasers and detectors, we envision the possibility of probing nonlinearities of the photon interaction in vacuum over substantial space-time scales, compared to the microscopic scale provided by high-energy accelerators. Specifically, we introduce the photon-photon interaction in a quasi-parallel colliding system and the detection of higher harmonics in that system. The method proposed should realize a far greater sensitivity of probing possible low-mass and weakly coupling fields that have been postulated. With the availability of a large number of coherent photons, we suggest a scheme for the detection of higher harmonics via the averaged resonant production and decay of these postulated fields within the uncertainty of the center-of-mass energy between incoming laser photons. The method carves out a substantial swath of new experimental parameter regimes on the coupling of these fields to photons, under appropriate laser technologies, even weaker than that of gravity in the mass range well below 1 eV.

hep-ph↗
arXiv2011

Probing vacuum birefringence by phase-contrast Fourier imaging under fields of high-intensity lasers

In vacuum high-intensity lasers can cause photon-photon interaction via the process of virtual vacuum polarization which may be measured by the phase velocity shift of photons across intense fields. In the optical frequency domain, the photon-photon interaction is polarization-mediated described by the Euler-Heisenberg effective action. This theory predicts the vacuum birefringence or polarization dependence of the phase velocity shift arising from nonlinear properties in quantum electrodynamics (QED). We suggest a method to measure the vacuum birefringence under intense optical laser fields based on the absolute phase velocity shift by phase-contrast Fourier imaging. The method may serve for observing effects even beyond the QED vacuum polarization.

hep-ph↗
arXiv2010

Probing semi-macroscopic vacua by high fields of lasers

The invention of laser immediately enabled us to detect nonlinearities of photon interaction in matter, as manifested for example by Franken et al.'s detection of second harmonic generation and the excitation of the Brillouin forward scattering process. With the recent advancement in high power high energy laser and the examples of the nonlinearity study of laser-matter interaction by virtue of properly arranging laser and detectors, we envision the possibility of probing nonlinearities of photon interaction in vacuum over substantial spacetime scales compared with the microscopic scale provided by high energy accelerators. The hithertofore never detected Euler-Heisenberg nonlinearities in quantum electrodynamics (QED) in vacuum should come within our reach of detection using intense laser fields. Also our method should put us in a position with a far greater sensitivity of probing possible light-mass fields that have been postulated. With the availability of a large number of coherent photons our suggested measurement methods include the phase sensitive (contrast) imaging that avoids the pedestal noise and the scheme of second harmonic detection of photon nonlinearities in vacuum over a long co-propagating distance incurring resonance excitation. These methods carve out a substantial swath of new experimental parameter regimes of the exploration of photon nonlinearities in vacuum covering the force range from the electron mass scale to below neV.

quant-ph↗
arXiv2010

A Laboratory Search for Dark Energy

The discovery of the accelerating universe indicates strongly the presence of a scalar field which is not only expected to solve today's version of the cosmological constant problem, or the fine-tuning and the coincidence problems, but also provides a way to understand dark energy. It has also been shown that Jordan's scalar-tensor theory is now going to be re-discovered in the new lights. In this letter we suggest a way to search for the extremely light scalar field by means of a laboratory experiment on the low-energy photon-photon interactions with the quasi-parallel incident beams.

gr-qc↗
arXiv2009

Fundamental physics on natures of the macroscopic vacuum under high intense electromagnetic fields with accelerators

High intense electromagnetic fields can be unique probes to study natures of macroscopic vacua by themselves. Combining accelerators with the intense field can provide more fruitful probes which can neither be achieved by only intense fields nor only high energy accelerators. We will overview the natures of vacua which can be accessible via intense laser-laser and intense laser-electron interactions. In the case of the laser-laser interaction, we propose how to observe nonlinear QED effects and effects of new fields like light scalar and pseudo scalar fields which may contribute to a macroscopic nature of our universe such as dark energy. In the case of the laser-electron interaction, in addition to nonlinear QED effects, we can further discuss the nature of accelerating field in the vacuum where we can access physics related with event horizons such as Hawking-Unruh radiations. We will introduce a recent experimental trial to search for this kind of odd radiations.

quant-ph↗
arXiv2007

Search for critical points by measuring spatial correlation lengths via multiplicity density fluctuations

The nature of phase boundaries in the QCD phase diagram has not been satisfactorily explored by experiments. Based on the Ginzburg-Landau free energy with a spatially inhomogeneous term as a function of a scalar order parameter, it is possible to determine spatial correlation lengths from measured two point correlation functions in general, where a spatially dependent multiplicity fluctuation from the mean value is taken as the order parameter. The divergence of the correlation lengths can be a robust signature of a critical system as well as the disappearance of $ $ condensations. Simultaneous observations of such observables can probe the nature of the phase boundary conclusively. In this letter, a present result from the PHENIX experiment will be reported. We will focus whether a critical behavior of the phase transition exists or not by searching for increases of pseudo-rapidity correlation lengths as a function of the number of participant nucleons with dominantly low $p_t$ charged particles where instant fluctuations such as high $p_t$ jets are expected to be negligible. The result shows a non monotonic increase in the correlation lengths which can be a symptom of the critical behavior.

nucl-ex↗
arXiv2003

Cherenkov radiations from Quark Plasma

I propose an observable to declare the formation of Quark Plasma (QP) without any doubts. It is the observation of Cherenkov photon radiations of the order of 100 MeV associated with fast light charged particles while they are penetrating hot dense mediums produced in high energy heavy ion collisions. Direct observations of Cherenkov rings associated with charged leptons decayed from $Z^0$ boson or Drell-Yang process which occur earlier than the QCD medium formation or photon emissions associated with high $p_t$ hadrons would be a definite signature of QP formation.

hep-ph↗