Double pole structures of X₁ (2900) as the P-wave D^*K^* resonances

We reveal the double pole structures of the manifestly exotic tetraquark state X₁ (2900) in the scenario of P-wave D^*K^* dimeson resonance. We find that the observed enhancement signal associated with X₁ (2900) in B^+ D^+D^-K^+ by LHCb contains two P-wave poles denoted as T₂ₒ₁- (2900) and T^₂ₒ₁- (2900), respectively. After considering the channel couplings among the DK, D^*K, DK^* and D^*K^* and the width of the K^* meson, the masses and widths of the S-wave pole T₂ₒ₀+ (2900) and two P-wave poles T₂ₒ₁- (2900) and T^₂ₒ₁- (2900) coincide with those of the X₀ (2900) and X₁ (2900) remarkably, which provides strong support for identifying X₀ (2900) and X₁ (2900) as D^ (*) K^ (*) dimeson states. Furthermore, we extensively calculate all S-wave and P-wave D^ (*) K^ (*) systems up to J=3 and predict four new isoscalar charmed-strange dimeson-type tetraquark states: an S-wave state T₂ₒ₁+ (2900) with quantum number JP=1^+, three P-wave states T₂ₒ₁- (2760) with JP=1^-, T₂ₒ₀- (2760) with JP=0^- and T₂ₒ₂- (2900) with JP=2^-. These near-threshold poles can be searched for at LHCb, Belle II and BESIII.