General Information
General Information
Abstract
Dark matter is one of the greatest mysteries of our Universe. We know less about its particle nature even though cosmological observations have confirmed its existence. The idea of the dark sector has recently drawn attention as particle physics models for the dark matter. The dark matter and associated particles (collectively named as the dark-sector particles) residing in the dark sector interact with each other, while the standard model particles have only feeble interactions with the dark-sector particles. The studies on the dark-sector models have intensively focused on simplified setups, where the dark sector consists of the dark matter and mediator particles (connecting the dark sector and the standard model sector). However, it is plausible that the dark sector has a complicated structure as with the standard model. In this project, I will focus on the dark-sector model with confining gauge dynamics, which lead to the dark sector composed of composite particles. There exist two dark matter candidates, dark baryon and dark pion, and the typical mass scale of the dark matter is similar to the masses of our hadrons (several hundred megaelectronvolts to several gigaelectronvolts). These dark matter candidates have self-interaction, which is preferred by the small-scale structure of galactic halos. Accidental global symmetries (such as dark baryon number and residual symmetry after the chiral symmetry breaking) ensure the stability of the dark matter.
Meanwhile, there also exist associated dark particles, whose decay or transition processes leave the standard model particles (such as electron-positron pair) via the mediator particles. These processes have characteristic signals that visible particles appear far from the production point of dark-sector particles due to the feeble connection between the dark sector and the standard model sector. Ongoing and future terrestrial experiments have explored these signals by putting the detectors away from the collision point of experiments, called long-lived particle searches. These future experiments will run on the time scale of the next decade, and it is timely to study the long-lived particle searches on the dark-sector models. However, the theoretical studies of long-lived particle searches have mainly focused on the dark-sector particle production via on-shell mediator particles (dark-sector particles are produced via the decay of mediator particles). My recent studies have focused on the dark-sector particle production via off-shell mediator particles, providing multiple visible signals with different decay lengths. These studies imply that various long-lived particle searches are essential for a model distinction.
In this project, I will study the dark-sector model with contact interactions. This model is an alternative to the dark-sector models with mediator particles, where the standard model matter fermions and the dark quarks have contact interaction. First, in this project, I will construct effective models of interactions among dark hadrons and standard model particles in the presence of contact interactions at the quark level. I will also study the constraints on the effective interaction between the standard model particles and the dark hadrons from cosmological observations, flavor physics, and CP-violating physics. This study will reveal the size of the contact interactions being consistent with observations and experiments. Next, I will apply the constructed effective models to the long-lived particle searches for the dark hadrons in the cases with dark-baryon dark matter and dark-pion dark matter. This project will focus on a specific production via interactions originating from the contact interactions. However, by combining this project and existing studies, we will cover the standard production mechanism for the dark-sector particles at the long-lived particle searches, particularly in composite dark matter models. Therefore, I am convinced that this project will be helpful to the theoretical study on the dark-sector searches and the experimental study in near future.
Budget
Budget
Budget Justification
(Please prepare the project budget in accordance with relevant requirements of the "Instruction of Budget Table Preparation of the Research Plan of NSFC-Awarded Project" following the principle of "policy compliance, relevant goals and economic rationality." When filling in the plan, the direct costs should be divided into three categories including equipment expenses, experimental and operating costs, and allowance, with explanations for each category specifying the purposes of expenditure in accordance with scientific research tasks. Explanations should be made for a single purchase of equipment totaling five hundred thousand yuan or above and for self-financing funds.)
(Please prepare the project budget in accordance with relevant requirements of the "Instruction of Budget Table Preparation of the Research Plan of NSFC-Awarded Project" following the principle of "policy compliance, relevant goals and economic rationality." When filling in the plan, the direct costs should be divided into three categories including equipment expenses, experimental and operating costs, and allowance, with explanations for each category specifying the purposes of expenditure in accordance with scientific research tasks. Explanations should be made for a single purchase of equipment totaling five hundred thousand yuan or above and for self-financing funds.)
I apply for the budget with two hundred thousand RMB. I assume China and other countries will relax COVID-19 restrictions on travel in twenty twenty-three. The followings are the detail:
Equipment expenses thirty-eight thousand RMB:
computing instruments (for analytical computations and numerical simulations) twenty thousand RMB, software tools (annual license for calculation tools) ten thousand RMB
supplies cost eight thousand RMB: Two HDDs for data storage (two thousand five hundred RMB per piece) and peripheral devices (such as connector and display) for computing instruments (three thousand RMB).