新物理的圈图效应在对撞机上的间接探测及暗能量的直接探测

by Dr Zhen Zhang (CHEP, PKU)

Tuesday 29 May 2018, 10:30 → 11:30 Asia/Shanghai

B105 (CHEP)

The beauty and cleaness of the modern physics are obscured by two new "clouds"，i.e, dark matter and dark energy. They account for 95% of the universe, but the mechanism of their interation is mysterious for us. To unravel this mystery faces two challenges: one is to find out observational evidences of their existence and another is to identify the right theory for describing them. In terms of above, the topic is organized as follows. （1）Probing New Physics Inside Loops at Electro-Positron Colliders When dark matter candidate and its parent particles are nearly degenerate, it would be difficult to probe them at the Large Hadron Collider directly. We propose to explore their quantum loop effects at future electro-positron colliders through three processes, i.e. e+ e− → ZH, e+ e− → W+ W− and e+ e− → μ+ μ− , with experimental constraints such as mono-jet/photon, relic abundance and EWPD taken into consideration. We use a renormalizable simplified model consisting of new scalars and fermions to describe new physics beyond the Standard Model. New particles are the general multiplets of the SU(2)L × U(1)Y symmetry plus an additional discrete Z2 symmetry, We calculate their loop contributions to anomalous couplings which can be applied to many new physics models. （2）Direct Probe of Dark Energy through Gravitational Lensing Effect So far all the existing evidences of dark energy are indirect. We demonstrate that gravitational lensing can provide a direct means to probe dark energy at astrophysical scales. For lensing system as an isolated astrophysical object, we derive the dark energy contribution to gravitational potential as a repulsive power-law term, containing a generic equation of state parameter w . We prove that it generates w-dependent and position-dependent modification to the light orbital equation. Under the modified post-Newtonian approximation, we compute its direct effect for such an isolated lensing system and derive light deflection by the dark energy force. This effect is distinctive because dark energy acts as a concave lens to diffuse light rays, in contrast to the conventional convex lensing effect by both visible and dark matter. Our new estimates show that the current gravitational lensing experiments are already sensitive to the direct probe of dark energy at astrophysical scales.