118558798
A possible NN*(1440) quasi-molecular state
Inspired by the recent observation of a narrow resonance-like structure around 2360 MeV in the pn → dπ0π0 cross section, the possibility of forming a NN*(1440) quasi-molecular state is investigated by using a meson exchange model in which the π, σ, ρ and ω exchanges in t- and u-channels are considered. By adopting the coupling constants extracted from the relevant NN scattering and N*(1440) decay data, it is found that a deuteron-like quasi-molecular state of NN*(1440) with a binding energy in the range of 2 ∼ 67 MeV can be formed. Therefore, it is speculated that the observed structure around 2360 MeV might be or may have a large component of the NN*(1440) quasi-molecular state.
16933147
Possible S-wave Bound-States of Two Pseudoscalar Mesons
AbstractUsing the potentials derived from vector-meson-exchanges, the KK¯, DK, BK¯, DD¯,BB¯, BD, DK¯ , BKand BD¯ systems are studied. Possible S-wave bound-states of twopseudoscalar mesons are discussed. We ﬁnd that systems of DB, DD¯, BB¯ and DKwithisospin 0 are likely to form S-wavebound states via strong interactionswhile the othersareunlikely to be bound by the strong interaction sector alone. With the Coulomb potential,the K + K − system can form an atomic bound state - the kaonium. The inﬂuence of theone-meson-exchange potential on the ground state energy of the kaonium and its decaywidths to ππand πηare evaluated. 1 Introduction Since the 1970’s, the possible existence of the nuclear-like bound states of mesons has beenone of the interesting subjects in hadron physics. Some hardrons such as the ψ(4040) [1],η(1440) [2], f 1 (1420) [3], f J (1720) [4], and the f 0 (980) and a 0 (980) [5, 6, 7, 8] were explainedas the nuclear-like bound states of mesons. To¨rnqvist [9] argued that the one-pion-exchangepotential is likely to form a few states composed of two ground-state mesons. In 2003 the BelleCollaboration reported a new narrow charmonium state at 3872±0.6(stat)±0.5(syst) MeVand with a width <2.3MeV(95% C.L.), which has been conﬁrmed by several experiments[10, 11, 12, 13]. Almost immediately, To¨rnqvist [14] claimed that this state is the one hepredicted long ago. Indeed the proximity of the X to D
122512536
Loop Group-Valued CS and WZNW models, integrable systems, and self-dual Yang-Mills theory
Affine CS and WZNW theories with values in infinite-dimensional (loop) groups are proposed. It appears that the affine CS theory naturally introduces a spectral parameter into a CS theory. The Sinh-Gordon, KdV, and nonlinear Schrödinger equations are obtained, via Hamiltonian reductions, from the affine WZNW. It is shown that the self-dual Yang-Mills (SDYM) equation is related to the equation of motion of the affine WZNW and, thus, symmetry algebra underlying the SDYM can be identified with the affine two-loop Kac-Moody algebra of the affine WZNW.
118992053
Isospin-Violating Dark Matter and Neutrinos From the Sun
ux from their annihilation in the center of the Sun, in a class of theories where the dark matter-nucleon spin-independent interactions break the isospin symmetry. We point out that, while the direct detection bounds with heavy targets like Xenon are weakened and reconciled with the positive signals in DAMA and CoGeNT experiments, the indirect detection using neutrino telescopes can impose a relatively stronger constraint and brings tension to such explanation, if the annihilation is dominated by heavy quark or -lepton
121435769
Phase Structure of Strange Matter in a Non-topological Soliton Model
A non-topological soliton model with strange quarks is suggested to investigate the phase structure of strange matter. The results are qualitatively in agreement with that obtained by MIT bag model provided the ratio of coupling constants of different quarks to soliton scalar field chi(sigma) = g(s sigma)/g(q sigma) larger than a critical value chi(c) similar to 0.86, but as chi(sigma) gets smaller than chi(c), the phase structure may change.
30742433
Yukawa bound states of a large number of fermions
A bstractWe consider the bound state problem for a field theory that contains a Dirac fermion χ that Yukawa couples to a (light) scalar field ϕ. We are interested in bound states with a large number N of χ particles. A Fermi gas model is used to numerically determine the dependence of the radius R of these bound states on N and also the dependence of the binding energy on N. Since scalar interactions with relativistic χ’s are suppressed two regimes emerge. For modest values of N the state is composed of non-relativistic χ particles. In this regime as N increases R decreases. Eventually the core region becomes relativistic and the size of the state starts to increase as N increases. As a result, for fixed Yukawa coupling and χ mass, there is a minimum sized state that occurs roughly at the value of N where the core region first becomes relativistic. We also compute an elastic scattering form factor that can be relevant for direct detection if the dark matter is composed of such χ particles.
27700488
Long-lived Light Mediator to Dark Matter and Primordial Small Scale Spectrum
We calculate the early universe evolution of perturbations in the dark matter energy density in the context of simple dark sector models containing a GeV scale light mediator. We consider the case that the mediator is long-lived, with lifetime up to a second, and before decaying it temporarily dominates the energy density of the universe. We show that for primordial perturbations that enter the horizon around this period, the interplay between linear growth during matter domination and collisional damping can generically lead to a sharp peak in the spectrum of dark matter density perturbation. As a result, the population of the smallest DM halos gets enhanced. Possible implications of this scenario are discussed.