Open-charm tetraquark Xc and open-bottom tetraquark Xb

Motivated by the LHCb observation of exotic states X 0 , 1 ( 2900 ) with four open quark flavors in the D - K + invariant mass distribution in the decay channel B ± → D + D - K ± , we study the spectrum and decay properties of the open charm tetraquarks. Using the two-body chromomagnetic interactions, we find that the two newly observed states can be interpreted as a radial excited tetraquark with J P = 0 + and an orbitally excited tetraquark with J P = 1 - , respectively. We then explore the mass and decays of the other flavor-open tetraquarks made of s u d ¯ c ¯ and d s u ¯ c ¯ , which are in the 6 ¯ or 15 representation of the flavor SU(3) group. We point that these two states can be found through the decays: X d s u ¯ c ¯ ( ′ ) → ( D - K - , D s - π - ) , and X s u d ¯ c ¯ ( ′ ) → D s - π + . We also apply our analysis to open bottom tetraquark X b and predict their masses. The open-flavored X b can be discovered through the following decays: X u d s ¯ b ¯ → B 0 K + , X d s u ¯ b ¯ ( ′ ) → ( B 0 K - , B s 0 π - ) , and X s u d ¯ b ¯ ( ′ ) → B s 0 π + .