Production and constraints for a massive dark photon at electron-positron colliders *

Abstract

Dark sectors may couple to the Standard Model via one or more mediator particles. In this paper, we discuss two types of mediators: the dark photon A and the dark scalar mediator φ. The total cross sections and various differential distributions of signal processes of e + e − → qqA and e + e − → qqφ (q = u, d, c, s and b quarks) are discussed, and then we focus on an invisible A study due to the cleaner background processes at future e + e − colliders. It is found that kinematic distributions of the two-jet system can be used to identify or exclude the dark photon and dark scalar mediator, as well as distinguish between them. We further study the possibility of the search for dark photon at future CEPC experiment with √ s = 91.2 GeV and 240 GeV. Running at √ s = 91.2 GeV, it is possible for CEPC to perform a decisive measurement on dark photon (20 GeV < m A < 60 GeV) in less than one operating year. The lower limits of integrated luminosity for significance S/ √ B = 2σ, 3σ and 5σ are presented. * Given the intricate structure of the Standard Model (SM), which describes only a sub-dominant component of the universe, it would not be too surprising if the dark sector contains a rich structure itself, with DM making up parts of it. In the dark sector, the DM particles do not interact directly to the known strong, weak and electromagnetic forces except for gravitational force. However, there is typically one or more mediator particles which are coupled with SM as the "portal" [16][17][18][19][20][21]. Such extended interactions associating dark sector and SM depend on the spin and parity: mediators can be vector A , scalar φ, pseudoscalar a, axial-vector Z and even fermions N .A new force mediated by dark photons has a subject of deep interest in the high energy particle physics. The existence of the dark photon [22][23][24], associated to a hidden U (1) gauge interaction, has been the object of many investigations, both theoretically and experimentally. Substantial efforts have been put by several authors into the search for a dark photon through various processes including bremsstrahlung process e − Z → e − ZA [25-28], meson decays process π 0 /η/η → γA , [32,33], annihilation process e + e − → γA [34-38], etc., and physicists have obtained stringent limits of the kinetic mixing parameter ε for a given dark photon mass m A [17,18,24,39,40]. For m A 1 GeV, only limited values of ε are allowed. For the heavy massive dark photon, a wide range is still not excluded by current ongoing experiments.The future high energy electron-positron colliders can provide an opportunity to search for the dark sector mediators. This kind of colliders include CEPC [41], ILC [42], FCC-ee [43] and CLIC [44] with the center-of-energy √ s varying from 91.2 GeV to 1 TeV. In this paper, assuming that dark mediators interact only with quarks, we investigate the production of dark photon A and dark scalar mediator φ at electron-positron colliders with √ s = 91.2 GeV, 240 GeV, 500GeV and 1 TeV. We analyze the cross sections and the normalized ki...

Production of tachyonic neutrino in matter

“…In a more speculative framework, we can assume that the Bremsstrahlung process leads to the formation of a massive dark photon. Recently, this hypothetical particle, mediator of a force not contemplated by the standard model, has attracted the attention of theoretical physicists since, weakly interacting with both ordinary and dark matter, it could explain some experimental phenomena to which physics is not still able to answer (for instance, neutrino oscillation and baryon asymmetry) [52][53][54]. In such a case, the first term of the Lagrangian (44) must be replaced by a new one given by the following: A is the dark photon field, m D P .…”

Busca pela matéria escura: fótons escuros e áxions solares no experimento COSINE-100

“…A lagrangiana que descreve o sistema composto pelo fóton ordinário e o fóton escuro é dada por [71]: A principal fonte de fótons escuros com massa abaixo de 100 keV seriam estrelas, nas quais a taxa de fótons escuros produzidos pela oscilação de fótons ordinários seria elevada, e dependeria da massa do fóton escuro, e da composição e temperatura das estrelas estudadas [72]. Para massas acima de 1 MeV, a principal fonte de fótons escuros seria a aniquilação de partículas de matéria escura fermiônica que estaria acumulada em poços gravitacionais, como os centros galácticos [73].…”

“…Também é possível, para energias da ordem de centenas de keV, a procura através do efeito Compton [74]. Entretanto, para massas maiores que 2 m e , a probabilidade do fóton escuro ser absorvido no detector é muito baixa, e a técnica de procura mais eficiente passa a ser a detecção de seu decaimento em um par partículaantipartícula do modelo padrão [75].…”