Particle Collisions on Stringy Black Hole Background

Abstract

The collision of two particles in the background of a Sen black hole is studied. With the equations of motion of the particles, the center-of-mass energy is investigated when the collision takes place at the horizon of a Sen black hole. For an extremal Sen black hole, we find that the center-of-mass energy will be arbitrarily high with two conditions: (1) spin $a\ne 0$ and (2) one of the colliding particles has the critical angular momentum $l_{\text{c}}=2$. For a nonextremal Sen black hole, we show that, in order to obtain an unlimited center-of-mass energy, one of the colliding particles should have the critical angular momentum $l_{\text{c}}^{\prime }=2r_{+}/a$ ($r_{+}$ is the radius of the outer horizon for a nonextremal black hole). However, a particle with the angular momentum $l=l_{\text{c}}^{\prime }$ could not approach the black hole from outside of the horizon through free fall, which implies that the collision with arbitrarily high center-of-mass energy could not take place. Thus, there is an upper bound of the center-of-mass energy for the nonextremal black hole. We also obtain the maximal center-of-mass energy for a near-extremal black hole and the result implies that the Planck-scale energy is hard to be approached. Furthermore, we also consider the back-reaction effects. The result shows that, neglecting the gravitational radiation, it has a weak effect on the center-of-mass energy. However, we argue that the maximum allowed center-of-mass energy will be greatly reduced to below the Planck-scale when the gravitational radiation is included.

17 pages, 4 figures, published version

References in corpus (3)

• Hidden symmetries, null geodesics, and photon capture in the Sen black hole
• Charged Spinning Black Holes as Particle Accelerators
• Generalized hidden symmetries and the Kerr-Sen black hole

Cited by in corpus (4)

• Particle Acceleration on the Background of the Kerr-Taub-NUT Spacetime
• Acceleration of particles by black holes -- general explanation
• Acceleration of colliding shells around a black hole: Validity of the test particle approximation in the Banados-Silk-West process
• Naked Singularities as Particle Accelerators II