We study heavy baryons with an exotic flavor quantum number formed by a heavy meson and a nucleon ( " DN and BN) through a long range one pion exchange interaction. The bound state found previously in the ðI; J P Þ ¼ ð0; 1=2 À Þ channel survives when short range interaction is included. In addition, we find a resonant state with ðI; J P Þ ¼ ð0; 3=2 À Þ as a Feshbach resonance predominated by a heavy vector meson and a nucleon ( " D Ã N and B Ã N). We find that these exotic states exist for the charm and heavier flavor region.

We study exotic mesons with double charm and bottom flavor, whose quark configuration is \bar{Q}\bar{Q}qq. This quark configuration has no annihilation process of quark and antiquark, and hence is a genuinely exotic states. We take a hadronic picture by considering the molecular states composed of a pair of heavy mesons, such as DD, DD* and D*D* for charm flavor, and BB, BB* and B*B* for bottom flavor. The interactions between heavy mesons are derived from the heavy quark effective theory. All molecular states are classified by I(J^P) quantum numbers, and are systematically studied up to the total angular momentum J \leq 2. By solving the coupled channel Schrodinger equations, due to the strong tensor force of one pion exchanging, we find bound and/or resonant states of various quantum numbers.Comment: 24 pages, 3 figure

We study heavy hadron spectroscopy near open bottom thresholds. We employ B and B* mesons as effective degrees of freedom near the thresholds, and consider meson exchange potentials between them. All possible composite states which can be constructed from the B and B* mesons are studied up to the total angular momentum J = 0, 1, 2. We consider, as exotic states, isosinglet states with exotic (J,PC) quantum numbers and isotriplet states. We solve numerically the Schrodinger equation with channel-couplings for each state. The masses of twin resonances Zb(10608) and Zb(10653) recently found by Belle are reproduced. We predict several possible bound and/or resonant states in other channels for future experiments.Comment: 27 pages, 2 figur

We study heavy baryons with exotic flavor quantum numbers formed by a heavy meson and a nucleon (DN and BN ) with positive parity. One pion exchange interaction, providing a tensor force, dominates as a long range force to bind theDN and BN systems. In the heavy quark mass limit, pseudoscalar meson and vector meson are degenerate and the binding mechanism by the tensor force analogous to that in the nuclear systems becomes important. As a result, we obtain theDN and BN resonant states in the J P = 1/2 + , 3/2 + and 5/2 + channels with I = 0.

We discuss the properties of hadronic systems containing one heavy quark in the heavy quark limit. The heavy quark symmetry guarantees the mass degeneracy of the states with total spin and parity (j -1 /2 ) p and (j + l / 2 ) p with j > 1/2, because the heavy quark spin is decoupled from the total spin j of the light components called brown muck. We apply this idea to heavy multihadron systems and formulate the general framework to analyze their properties. We demonstrate explicitly the spin degeneracy and the decomposition of the wave functions in exotic heavy hadron systems generated by the one-boson-exchange potential. The masses of the brown muck can be extracted from theoretical and experimental hadron spectra, leading to the color nonsinglet spectroscopy. L INTRODUCTIONT he study o f the exotic hadrons provides us w ith unique opportunities to explore fundam ental properties o f the low energy QCD, such as color confinem ent, the chiral sym m etry breaking, etc. Recently, in the heavy flavor (charm and bottom ) sectors, experim ental evidences for new candidates o f exotic hadrons, such as X , Y, Z , have been reported, and these states are extensively investi gated in theoretical w orks [1,2]. A lthough there have been m any theoretical studies based on various pictures such as m ultiquarks, hybrids o f quarks and gluons, m ultihadrons, and so on, we have not yet understood the essential features o f exotic heavy hadrons. In the present article, we approach the structure o f the hadronic m olecules w ith a heavy quark from the point o f view o f the heavy quark sym m etry (HQS) [3 -9 ], nam ely, the sym m etry o f the heavy quark spin, as the fundam ental property o f heavy hadrons.In general, for hadrons with a single heavy quark, the HQS leads to the m ass degeneracy o f tw o states with different total spin in the heavy quark limit. This is because the spin o f the heavy quark is decoupled from the total spin o f the other com ponents m ade o f light quarks and gluons. T he latter com ponent is called the brow n muck, w hich is everything but the heavy quark. It is im portant to note that the brow n m uck has the conserved total spin j , although the brow n m uck is a nonperturbative object w hich is dressed by m any quarks and gluons like qn + qnqq + q"g + ... with a net quark num ber n. For *yasuis@th. phys.titech.ac.jp j f 0, the spin degeneracy in the heavy hadrons is realized by the pair states with the total angular m om enta, Jj -1 /2 and j + 1/2. We call those two states the "HQS doublet." For j = 0, there is only one state with J = 1/2. We call this state the "HQS singlet."The HQS is seen in the mass spectrum of the charm and bottom hadrons. For example, the m ass splitting between D (J -0) and D* ( / = 1) m esons is 140 MeV, and that betw een B and B* m esons is 45 M eV [10]. Those mass splittings are smaller than the ones between n and p (~600 M eV) and that betw een K and K* (~400 MeV). Therefore, D and D* (B and B ' ) mesons are approxim ately regarded as the HQS doublet states. In those ca...