arXiv subjects

M. Ibe

Publications and source records attributed to M. Ibe.

At least 19 recordsLinked to original sources

arXiv2022

Japan's Strategy for Future Projects in High Energy Physics

The current strategy for future projects of the Japanese high energy physics community, Japan Association of High Energy Physicists (JAHEP), remains as described in the Final Report of the Committee on Future Projects in High Energy Physics, published in 2017. The Recommendation part of the Final Report is excerpted in the following page. This document updates the Final Report by adding developments and advances that have occurred since 2017.

hep-ex↗

arXiv2018

Automatic Peccei-Quinn symmetry

We present a dynamical (composite) axion model where the Peccei-Quinn (PQ) symmetry arises automatically as a consequence of chirality and gauge symmetry. The Standard Model is simply extended by a confining and chiral $SU(5)$ gauge symmetry. The PQ symmetry coincides with a $B-L$ symmetry of the exotic sector. The theory is protected by construction from quantum gravitational corrections stemming from operators with mass dimension lower than nine.

hep-ph↗

arXiv2009

Strongly Coupled Semi-Direct Mediation of Supersymmetry Breaking

Strongly coupled semi-direct gauge mediation models of supersymmetry breaking through massive mediators with standard model charges are investigated by means of composite degrees of freedom. Sizable mediation is realized to generate the standard model gaugino masses for a small mediator mass without breaking the standard model symmetries.

hep-ph↗

arXiv2009

Studying Gaugino Mass in Semi-Direct Gauge Mediation

We study gaugino mass generation in the context of semi-direct gauge mediation models, where the messengers are charged under both the hidden sector and the standard model gauge groups while they do not play important roles in dynamical supersymmetry breaking. We clarify the cancellation of the leading contributions of the supersymmetry breaking effects to the gaugino mass in this class of models in terms of the macroscopic effective theory of the hidden sector dynamics. We also consider how to retrofit the model so that we obtain the non-vanishing leading contribution to the gaugino mass.

hep-ph↗

arXiv2008

Conformal Supersymmetry Breaking and Dynamical Tuning of the Cosmological Constant

We propose "conformal supersymmetry breaking" models, which tightly relate the conformal breaking scale (i.e. R-symmetry breaking scale) and the supersymmetry breaking scale. The both scales are originated from the constant term in the superpotential through the common source of the R-symmetry breaking. We show that dynamical tuning between those mass scales significantly reduces the degree of fine-tuning necessary for generating the almost vanishing cosmological constant.

hep-th↗

arXiv2008

Conformal Gauge Mediation and Light Gravitino of Mass m_{3/2} <O(10) eV

We discuss a class of gauge mediated supersymmetry breaking models with conformal invariance above the messenger mass scale (conformal gauge mediation). The spectrum of the supersymmetric particles including the gravitino is uniquely determined by the messenger mass. When the conformal fixed point is strongly interacting, it predicts a light gravitino of mass m_{3/2}<O(10) eV, which is attractive since such a light gravitino causes no problem in cosmology.

hep-ph↗

arXiv2007

R-invariant New Inflation Model vs Supersymmetric Standard Model

We revisit the implications of the R-invariant New Inflation model to the supersymmetric standard model in light of recent discussion of gravitino production processes by the decay of the inflaton or the supersymmetry breaking field. We show that the models with supergravity mediation do not go well with the R-invariant New Inflation model, where the gravitino abundance produced by the decay of the inflaton or the supersymmetry breaking field significantly exceeds the bounds from cosmological observations without fine-tuning. We also show that the models with gauge mediation can go together with R-invariant New Inflation model, where the dark matter and the baryon asymmetry are consistently explained without severe fine-tuning.

hep-ph↗

arXiv2007

Conformal Gauge Mediation

We propose a one-parameter theory for gauge mediation of supersymmetry (SUSY) breaking. The spectrum of SUSY particles such as squarks and sleptons in the SUSY standard-model and the dynamics of SUSY-breaking sector are, in principle, determined only by one parameter in the theory, that is, the mass of messengers. Above the messenger threshold all gauge coupling and Yukawa coupling constants in the SUSY-breaking sector are on the infrared fixed point. We find that the present theory may predict a split spectrum of the standard-model SUSY particles, m_{gaugino} < m_{sfermion}, where m_{gaugino} and m_{sfermion} are SUSY-breaking masses for gauginos and squarks/sleptons, respectively.

hep-ph↗

arXiv2006

Possible Signals of Wino LSP at the Large Hadron Collider

We consider a class of anomaly-mediated supersymmetry breaking models where gauginos acquire masses mostly from anomaly mediation while masses of other superparticles are from Kahler interactions, which are as large as gravitino mass, O(10-100) TeV. In this class of models, the neutral Wino becomes the lightest superparticle in a wide parameter region. The mass splitting between charged and neutral Winos are very small and experimental discovery of such Winos is highly non-trivial. We discuss how we should look for Wino-induced signals at Large Hadron Collider.

hep-ph↗

arXiv2006

A New Inflation Model with Anomaly-mediated Supersymmetry Breaking

If there are a large number of vacua, multi-inflation may be a more mediocre phenomenon rather than a single inflation. In the multi-inflation scenario, new inflation is most likely the last inflation, since its energy scale is naturally low. Furthermore, it may explain the observed spectral index of the cosmic microwave background radiations. We show, in this letter, that a new inflation model proposed in supergravity accounts for all the present observations assuming anomaly mediation of supersymmetry breaking. As a result, we find that the relic density of the winos is consistent with the observed dark matter density in a wide range of the wino mass, 100 GeV lsim m_{tilde{w}} lsim 2 TeV, albeit for a low reheating temperature T_{R} simeq 10^{6-7},GeV.

hep-ph↗

arXiv2006

The Polonyi Problem and Upper bound on Inflation Scale in Supergravity

We reconsider the Polonyi problem in gravity-mediation models for supersymmetry (SUSY) breaking. It has been argued that there is no problem in the dynamical SUSY breaking scenarios, since the Polonyi field acquires a sufficiently large mass of the order of the dynamical SUSY-breaking scale Lamada_{SUSY}. However, we find that a linear term of the Polonyi field in the Kahler potential brings us back to the Polonyi problem, unless the inflation scale is sufficiently low, H_{inf} < 10^{8} GeV, or the reheating temperature is extremely low, T_{R} < 100 GeV. Here, this Polonyi problem is more serious than the original one, since the Polonyi field mainly decays into a pair of gravitinos.

hep-ph↗

arXiv2006

Eluding the BBN constraints on the stable gravitino

We investigate how late-time entropy production weakens the Big-Bang Nucleosynthesis (BBN) constraints on the gravitino as lightest superparticle with a charged slepton as next-to-lightest superparticle. We find that with a moderate amount of entropy production, the BBN constraints can be eluded for most of the parameter space relevant for the discovery of the gravitino. This is encouraging for experimental tests of supergravity at LHC and ILC.

hep-ph↗

arXiv2006

Minimal Supergravity, Inflation, and All That

We consider an inflationary model in the hidden-sector broken supergravity with an effectively large cutoff. The inflaton decay into right-handed neutrinos naturally causes the observed baryon asymmetry of the universe with a reheating temperature low enough to avoid the gravitino overproduction. We emphasize that all the phenomenological requirements from cosmology and particle physics are satisfied in the large-cutoff theory.

hep-ph↗

arXiv2006

Conformally Sequestered SUSY Breaking in Vector-like Gauge Theories

We provide, in a framework of vector-like gauge theories, concrete models for conformal sequestering of dynamical supersymmetry (SUSY) breaking in the hidden sector. If the sequestering is sufficiently strong, anomaly mediation of the SUSY breaking may give dominant contributions to the mass spectrum of SUSY standard-model particles, leading to negative slepton masses squared. Thus, we also consider a model with gravitational gauge mediation to circumvent the tachyonic slepton problem in pure anomaly mediation models.

hep-ph↗

arXiv2005

More on Conformally Sequestered SUSY Breaking

We extend our models for conformal sequestering of dynamical supersymmetry breaking with decoupling vector-like matter in several different ways. These extensions enable us to simplify concrete model building, in particular, rendering large gauge group and ad hoc global symmetry for sequestering unnecessary. Conformal sequestering appears highly natural in such circumstances.

hep-ph↗

arXiv2005

Dark Matter and Baryon Asymmetry of the Universe in Large-Cutoff Supergravity

We propose a consistent scenario of the evolution of the universe based on the large cutoff supergravity (LCSUGRA) hypothesis of supersymmetry breaking, where the gravitino and sfermion become as heavy a $\sim O(1-10 {\rm TeV})$. With such a heavy gravitino, baryon asymmetry of the universe can be generated by the non-thermal leptogenesis via an inflaton decay without conflicting the serious gravitino problem. We also see that, in the LCSUGRA scenario, relic density of the lightest superparticle becomes consistent with the WMAP value of the dark matter density in the parameter region required for the successful non-thermal leptogenesis.

hep-ph↗

arXiv2004

Realization of Minimal Supergravity

Minimal supergravity mediation of supersymmetry breaking has attracted much attention due to its simplicity, which leads to its predictive power. We consider how Nature possibly realizes minimal supergravity through inflationary selection of the theory. Minimality is impressively consistent with the present observational bounds and it might be tested with the aid of low-energy soft parameters obtained in future experiments.

hep-ph↗

arXiv2004

A solution to the baryon and dark-matter coincidence puzzle in a $\tilde{N}$ dominated early universe

If a bosonic partner of a right-handed neutrino dominates the early universe sufficiently before its decay, important ingredients in the present universe are related to physics of the right-handed neutrino sector. In particular, we find that the ratio of the baryon to the dark-matter densities is given only by low-energy parameters such as a neutrino mass and a gravitino mass if the reheating temperature of inflation is much higher than $10^{12}$ GeV. Here, the gravitino is assumed to be the lightest supersymmetric particle and the dominant component of the dark matter. The observed ratio, $Ω_{B}/Ω_{DM} \simeq 0.21\pm 0.04$, suggests the mass of the gravitino to be in the range of $\cal O$(10) MeV provided the CP violating phase is of the order 1.

hep-ph↗