We have studied the polarized image of an equatorial emitting ring around a rotating braneworld black hole. This black hole possesses a tidal charge parameter $\textit{b}$, which describes the effects of the free gravitational field in the bulk on the brane. Results show that the effects of the tidal charge parameter on the polarized image depend on the magnetic field structure, the observer inclination, the velocity of the fluid and the radii of the emitting ring. For a given value of the rotation parameter, the observed polarization intensity increases monotonously with $\textit{b}$ when the magnetic field lies in the equatorial plane, while it no longer changes monotonically with $\textit{b}$ when the magnetic field is perpendicular to the equatorial plane. The effect of parameter $\textit{b}$ on polarized images is similar in both stronger and weaker gravitational fields when the magnetic field is within the equatorial plane, and the differences in polarization vectors for different $\textit{b}$ become noticeable in stronger gravitational fields. We also probe the effects of $\textit{b}$ on the Stokes Q-U loops.

China

Xin Qin

Songbai Chen

Xiangyun Fu

Yang Huang

Jiliang Jing

Polarized image of an equatorial emitting ring around a rotating braneworld black hole

New vectorlike T-quarks (VLQ-T) have been predicted in many scenarios of new physics beyond the Standard Model, the current mass exclusion limits from LHC experiments will be relaxed by the presence of additional decay channels. In this work, we investigate the prospect of discovering the pair production of VLQ-T at the future 3 TeV Compact Linear Collider (CLIC), by focusing on the final signals via the standard decay channel <math><mi>T</mi><mo>→</mo><mi>W</mi><mi>b</mi></math> where one of the W bosons decays leptonically and the other decays hadronically. By performing a rapid detector simulation of the signal and background events as well as considering the initial state radiation and beamstrahlung effects, the exclusion limit at the 95% confidence level and the 5σ discovery prospects are, respectively, obtained on the integrated luminosity and the branching ratio of <math><mi>T</mi><mo>→</mo><mi>W</mi><mi>b</mi></math> for three typical VLQ-T masses.

Chang Wang

Pair production of the vectorlike top partner at the CLIC

We have studied the polarized image of an equatorial emitting ring around a rotating black hole surrounded by a cold dark matter (CDM) halo. Results show that the CDM halo density has the similar effects of the halo’s characteristic radius on the polarized image for the black hole. The effects of the CDM halo on the polarized image depend on the magnetic field configuration, the fluid velocity and the observed inclination. With the increase of the CDM halo parameters, the observed polarization intensity decreases when the magnetic field lies in equatorial plane, but in the case where the magnetic field is perpendicular to the equatorial plane, the change of the observed polarization intensity with CDM halo also depends on the position of the emitting point in the ring. The change of the electric vector position angle (EVPA) with the CDM halo becomes more complicated. Our results also show that the influence of the CDM halo on the polarized image is generally small, which are consistent with the effects of dark matter halo on black hole shadows. These results could help to further understand dark matter from black hole images.

Zelin Zhang

Polarized image of a rotating black hole surrounded by a cold dark matter halo

We have studied the polarized image of an equatorial emitting ring around a 4D Gauss–Bonnet black hole. Our results show that the effects of Gauss–Bonnet parameter on the polarized image depend on the magnetic field configuration, the observation inclination angle, and the fluid velocity. As the magnetic field lies in the equatorial plane, the observed polarization intensity increases monotonously with Gauss–Bonnet parameter in the low inclination angle case, and its monotonicity disappears in the case with high inclination angle. However, as the magnetic field is vertical to the equatorial plane, the polarization intensity is a monotonously increasing function of Gauss–Bonnet parameter in the high inclination angle case. The changes of the electric vector position angle with Gauss–Bonnet parameter in both cases are more complicated. We also probe the effects of Gauss–Bonnet parameter on the Strokes Q–U loops.

Polarized image of an equatorial emitting ring around a 4D Gauss–Bonnet black hole

Based on a model-independent framework including <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><mo>)</mo></math> singlet vector-like top partner (VLQ-T), we investigate the prospect of discovering the single production of VLQ-T decaying into Wb in <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></math> collisions at 3 TeV Compact Linear Collider (CLIC). By carrying out a full simulation for the signal and the relevant SM backgrounds, we find that for the high integrated luminosity of 3 (5) ab$^{−1}$, the singlet VLQ-T could be excluded in the correlated region of the coupling parameter <math><msup><mrow><mi>g</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>∈</mo><mo>[</mo><mn>0.17</mn><mo>,</mo><mn>0.5</mn><mo>]</mo><mspace width="0.25em"></mspace><mo>(</mo><mo>[</mo><mn>0.15</mn><mo>,</mo><mn>0.4</mn><mo>]</mo><mo>)</mo></math> and mass <math><msub><mrow><mi>m</mi></mrow><mrow><mi>T</mi></mrow></msub><mo>∈</mo></math> [1500 GeV, 2600 GeV] at 2σ level, and the discovered correlation region is <math><msup><mrow><mi>g</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>∈</mo><mo>[</mo><mn>0.27</mn><mo>,</mo><mn>0.5</mn><mo>]</mo><mspace width="0.25em"></mspace><mo>(</mo><mo>[</mo><mn>0.24</mn><mo>,</mo><mn>0.44</mn><mo>]</mo><mo>)</mo></math> and <math><msub><mrow><mi>m</mi></mrow><mrow><mi>T</mi></mrow></msub><mo>∈</mo></math> [1500 GeV, 2400 GeV]. The future 3 TeV CLIC is a promising hunting ground for such new particles with electroweak strength interactions.

Liu-Feng Du

Jie-Fen Shen

Single production of vector-like Quark Decaying Into at the CLIC

We have studied polarized image of a Schwarzschild black hole with an equatorial thin accretion disk as photon couples to Weyl tensor. The birefringence of photon originating from the coupling affect the black hole shadow, the thin disk pattern and its luminosity distribution. We also analyze the observed polarized intensity in the sky plane. The observed polarized intensity in the bright region is stronger than that in the darker region. The stronger effect of the coupling on the observed polarized vector appears only in the bright region close to black hole. These features in the polarized image could help us to understand black hole shadow, the thin accretion disk and the coupling between photon and Weyl tensor.

Polarized image of a Schwarzschild black hole with a thin accretion disk as photon couples to Weyl tensor

We investigate the prospect of discovering the <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><mo>)</mo></math> singlet vector-like bottom quark (VLQ-B) in <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></math> collisions at future Compact Linear Collider (CLIC) at the 3 TeV stage. As signal process, we focus on single production of the VLQ-B with 4b final state, namely, <math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>→</mo><mi>B</mi><mover><mrow><mi>b</mi></mrow><mrow><mo>¯</mo></mrow></mover><mo>→</mo><mi>h</mi><mi>b</mi><mover><mrow><mi>b</mi></mrow><mrow><mo>¯</mo></mrow></mover></math> followed by <math><mi>h</mi><mo>→</mo><mi>b</mi><mover><mrow><mi>b</mi></mrow><mrow><mo>¯</mo></mrow></mover></math>. By carrying out a full detector simulation for the signals and the relevant SM backgrounds, the 2σ exclusion limit and 5σ discovery prospects are, respectively, obtained on the coupling strength <math><msub><mrow><mi>κ</mi></mrow><mrow><mi>B</mi></mrow></msub></math> and the integrated luminosity. For the medium (loose) working point with 70% (90%) b-tagging efficiency, the VLQ-B quark can be excluded in the region of <math><msub><mrow><mi>κ</mi></mrow><mrow><mi>B</mi></mrow></msub><mo>∈</mo><mo>[</mo><mn>0.125</mn><mo>,</mo><mn>0.24</mn><mo>]</mo><mspace width="0.25em"></mspace><mo>[</mo><mn>0.09</mn><mo>,</mo><mn>0.15</mn><mo>]</mo></math> and <math><msub><mrow><mi>m</mi></mrow><mrow><mi>B</mi></mrow></msub><mo>∈</mo><mo>[</mo><mn>1.3</mn><mo>,</mo><mn>2.0</mn><mo>]</mo></math> TeV, while the discovered region can reach to <math><msub><mrow><mi>κ</mi></mrow><mrow><mi>B</mi></mrow></msub><mo>∈</mo><mo>[</mo><mn>0.19</mn><mo>,</mo><mn>0.32</mn><mo>]</mo><mspace width="0.25em"></mspace><mo>(</mo><mo>[</mo><mn>0.14</mn><mo>,</mo><mn>0.24</mn><mo>]</mo><mo>)</mo></math>. Finally, we also analyze the projected sensitivity in terms of the production cross section times branching fraction at the future 3 TeV CLIC.