| Home | << 1 2 3 4 5 6 7 8 9 10 >> [11–20] |
|
Guo, F. K., Hidalgo-Duque, C., Nieves, J., & Pavon Valderrama, M. (2013). Consequences of heavy-quark symmetries for hadronic molecules. Phys. Rev. D, 88(5), 054007–5pp.
Abstract: Among the newly observed structures in the heavy-quarkonium mass region, some have been proposed to be hadronic molecules. We investigate the consequences of heavy- quark flavor symmetry on these heavy meson hadronic molecules. The symmetry allows us to predict new hadronic molecules on one hand, and test the hadronic molecular assumption of the observed structures on the other hand. We explore the consequences of the flavor symmetry assuming the X(3872) and Z(b)(10 610) as an isoscalar D (D) over bar* and isovector B (B) over bar* hadronic molecule, respectively. A series of hadronic molecules composed of heavy mesons are predicted. In particular, there is an isoscalar 1(++) B (B) over bar* bound state with a mass about 10 580 MeV which may be searched for in the Y(1S, 2S)pi(+) pi(-) pi(0) mass distribution; the isovector charmonium partners of the Z(b)(10 610) and the Z(b)(10 650) are also predicted, which probably corresponds to the very recently observed Z(c)(3900) and Z(c)(4025) resonances by the BESIII Collaboration.
|
|
Xiao, C. W., Nieves, J., & Oset, E. (2013). Combining heavy quark spin and local hidden gauge symmetries in the dynamical generation of hidden charm baryons. Phys. Rev. D, 88(5), 056012–20pp.
Abstract: We present a coupled channel unitary approach to obtain states dynamically generated from the meson-baryon interaction with hidden charm, using constraints of heavy quark spin symmetry. As a basis of states, we use (D) over barB, (D) over bar *B states, with B baryon charmed states belonging to the 20 representations of SU(4) with J(P) = 1/2(+), 3/2(+). In addition we also include the eta N-c and J/psi N states. The inclusion of these coupled channels is demanded by heavy quark spin symmetry, since in the large m(Q) limit the D and D* states are degenerate and are obtained from each other by means of a spin rotation, under which QCD is invariant. The novelty in the work is that we use dynamics from the extrapolation of the local hidden gauge model to SU(4), and we show that this dynamics fully respects the constraints of heavy quark spin symmetry. With the full space of states demanded by the heavy quark spin symmetry and the dynamics of the local hidden gauge, we look for states dynamically generated and find four basic states that are bound, corresponding to (D) over bar Sigma(c), (D) over bar Sigma(c)*, (D) over bar*Sigma(c) and (D) over bar*Sigma*(c) decaying mostly into eta N-c and J/psi N. All the states appear in isospin I = 1/2, and we find no bound states or resonances in I = 3/2. The (D) over bar Sigma(c) state appears in J = 1/2 and the (D) over bar Sigma*(c) in J = 3/2; the (D) over bar*Sigma(c) appears nearly degenerate in J = 1/2, 3/2 and the (D) over bar*Sigma*(c) appears nearly degenerate in J = 1/2, 3/2, 5/2, with the peculiarity that in J = 5/2 the state has zero width in the space of states chosen. All the states are bound with about 50 MeV with respect to the corresponding (D) over barB thresholds, and the width, except for the J = 5/2 state, is also of the same order of magnitude. Finally, we discuss the uncertainties stemming from the expected breaking of SU(4) and the heavy quark spin symmetry.
|
|
Guo, F. K., Hidalgo-Duque, C., Nieves, J., & Pavon Valderrama, M. (2013). Heavy-antiquark-diquark symmetry and heavy hadron molecules: Are there triply heavy pentaquarks? Phys. Rev. D, 88(5), 054014–6pp.
Abstract: We explore the consequences of heavy flavor, heavy quark spin, and heavy antiquark-diquark symmetries for hadronic molecules within an effective field theory framework. Owing to heavy antiquark-diquark symmetry, the doubly heavy baryons have approximately the same light-quark structure as the heavy antimesons. As a consequence, the existence of a heavy meson-antimeson molecule implies the possibility of a partner composed of a heavy meson and a doubly heavy baryon. In this regard, the D (D) over bar* molecular nature of the X(3872) will hint at the existence of several baryonic partners with isospin I = 0 and J(P) = 5(-)/2 or 3(-)/2. Moreover, if the Z(b)(10650) turns out to be a B*(B) over bar* bound state, we can be confident of the existence of Xi(bb)*(B) over bar* hadronic molecules with quantum numbers I(J(P)) = 1(1(-)/2) and I(J(P)) = 1(3/2(-)). These states are of special interest since they can be considered to be triply heavy pentaquarks.
|
|
Gran, R., Nieves, J., Sanchez, F., & Vicente Vacas, M. J. (2013). Neutrino-nucleus quasi-elastic and 2p2h interactions up to 10 GeV. Phys. Rev. D, 88(11), 113007–10pp.
Abstract: We extend to 10 GeV results from a microscopic calculation of charged-current neutrino-nucleus reactions that do not produce a pion in the final state. For the class of events coming from neutrino interactions with two nucleons producing two holes (2p2h), limiting the calculation to three-momentum transfers less than 1.2 GeV produces a two-dimensional distribution in momentum and energy transfer that is roughly constant as a function of energy. The cross section for 2p2h interactions approximately scales with the number of nucleons for isoscalar nuclei, similar to the quasi-elastic cross section. When limited to momentum transfers below 1.2 GeV, the cross section is 26% of the quasi-elastic cross section at 3 GeV, but 14% if we neglect a Delta(1232) resonance absorption component. The same quantities are 33% and 17% for antineutrinos. For the quasi-elastic interactions, the full nuclear model with long range correlations produces an even larger, but approximately constant distortion of the shape of the four-momentum transfer at all energies above 2 GeV. The 2p2h enhancement and long-range correlation distortions to the cross section for these interactions are significant enough they should be observable in precision experiments to measure neutrino oscillations and neutrino interactions at these energies, but also balance out and produce less total distortion than each effect does individually.
|
|
Xie, J. J., Wang, E., & Nieves, J. (2014). Re-analysis of the A(1520) photoproduction reaction. Phys. Rev. C, 89(1), 015203–10pp.
Abstract: Based on previous studies that support the important role of the N*(2120)D-13 resonance in the gamma p -> K+ A(1520) reaction, we make a re-analysis of this A(1520) photoproduction reaction taking into account the recent CLAS differential cross-section data. In addition to the contact, t-channel (K) over bar exchange, s-channel nucleon pole, and N*(2120) [previously called N*(2080)] resonance contributions, which have been considered in previous works, we also study the u-channel A(1115) hyperon pole term. The latter mechanism has always been ignored in all theoretical analysis, which has mostly relied on the very forward K+ angular LEPS data. It is shown that when the contributions from the N*(2120) resonance and the A(1115) hyperon are taken into account, both the new CLAS and the previous LEPS data can be simultaneously described. We also show that the contribution from the u-channel A(1115) pole term produces an enhancement for large K+ angles, and it becomes more and more relevant as the photon energy increases, being essential to describe the CLAS differential cross sections at backward angles. Furthermore, we find that the new CLAS data also favor the existence of the N*(2120) resonance and that these measurements can be used to further constrain its properties.
|