Domain Walls are Diamagnetic

It is shown that contrary to a recent claim in the literature, the domain walls made of scalar field are diamagnetic due to presence of massless fermionic modes on the wall. The diamagnetism vanishes at high temperature. Thus the domain walls could produce no effect on a primordial magnetic field in the early universe.Comment: 6 pages in LaTe

Search for ηc′\eta_{c}^{'} and hc(1P1)h_{c} (^{1}P_{1}) states in the e+e−e^+ e^- annihilations

Productions and decays of spin-singlet $S,P-$wave charmonium states, $\eta_{c}^{'}$ and $h_{c} (^{1}P_{1})$, in the $e^+ e^-$ annihilations are considered in the QCD multipole expansion with neglecting nonlocality in time coming from the color-octet intermediate states. Our approximation is opposite to the Kuang-Yan's model. The results are $B (\psi^{'} \rightarrow h_{c} + \pi^{0}) \approx 0.3 \%$, $B ( \psi^{'} \rightarrow \eta^{'} + \gamma ) \approx 0.34 \%$, $\Gamma (\eta_{c}^{'} \rightarrow J/\psi + \gamma) \approx 0.26$ keV and $\Gamma (h_{c} \rightarrow J/\psi + \pi^{0}) \approx 2.5$ keV.Comment: LaTeX file, to appear in Phys. Rev.

On intersection of domain walls in a supersymmetric model

We consider a classical field configuration, corresponding to intersection of two domain walls in a supersymmetric model, where the field profile for two parallel walls at a finite separation is known explicitly. An approximation to the solution for intersecting walls is constructed for a small angle at the intersection. We find a finite effective length of the intersection region and also an energy, associated with the intersection.Comment: 12 pages, LaTeX, 4 figures, ep

Interference and binding effects in decays of possible molecular component of X(3872)

It is pointed out that the internal structure of the narrow resonance X(3872) at the D^0 {\bar D}^{*0} threshold can be studied in some detail by measuring the rate and the spectra in the decays X(3872) \to D^0 {\bar D}^0 \pi^0 and X(3872) \to D^0 {\bar D}^0 \gamma. In particular, if this resonance contains a dominant `molecular' component D {\bar D^*} \pm {\bar D} D^*, this component can be revealed and studied by a distinct pattern of interference between the underlying decays of D^{*0} and {\bar D}^{*0} whose coherence is ensured by fixed (but yet unknown) C parity of the X(3872).Comment: 7 pages, 1 figur

Weak decays Xi_Q -> Lambda_Q pi

The weak decays Xi_b -> Lambda_b pi and Xi_c -> Lambda_c pi, in which the heavy quark is not destroyed, are discussed. The branching fractions for these decays, corresponding to an absolute rate of order 0.01 ps^{-1}, should be at a one percent level for the b hyperons and at a (few) per mill level for Xi_c, possibly making feasible their experimental study in future. It is shown, through an application of the heavy quark limit, the flavor SU(3) symmetry, and PCAC, that the Delta I = 1/2 rule should hold very well in these decays, and also that the Xi_b decays are purely S wave in the symmetry limit, while the difference between the $S$ wave amplitudes of the Xi_c decays and those for the Xi_b is related, in terms of the heavy quark expansion, to the difference of the total decay rates within the (Xi_c, Lambda_c) triplet of charmed hyperons. We also comment on the amplitudes of the semileptonic transitions Xi_Q -> Lambda_Q l nu and on the weak radiative decays Xi_Q -> Lambda_Q gamma.Comment: 8 page

No Primordial Magnetic Field from Domain Walls

It is pointed out that, contrary to some claims in the literature, the domain walls cannot be a source of a correlated at large scales primordial magnetic field, even if the fermionic modes bound on the wall had ferromagnetic properties. In a particular model with massive (2+1) dimensional fermions bound to a domain wall, previously claimed to exhibit a ferromagnetic behavior, it is explicitly shown that the fermionic system in fact has properties of a normal diamagnetic with the susceptibility vanishing at high temperature.Comment: 8 pages. Modified discussion of the baryon density on an axion domain wal

The enhancement of the decay Upsilon(1D) -> eta Upsilon(1S) by the axial anomaly in QCD

It is shown that the rates of the decays Upsilon(1^3D_1) -> eta Upsilon(1S) and Upsilon(1^3D_2) -> eta Upsilon(1S) should be comparable to and likely exceed that of the recently discussed in the literature two-pion transition Upsilon(1D) -> pi pi Upsilon(1S). The reason for this behavior is that the discussed eta transitions are enhanced by the contribution of the anomaly in the flavor singlet axial current in QCD.Comment: 11 page

The rate of metastable vacuum decay in (2+1) dimensions

The pre-exponential factor in the probability of decay of a metastable vacuum is calculated for a generic (2+1) dimensional model in the limit of small difference $\epsilon$ of the energy density between the metastable and the stable vacua. It is shown that this factor is proportional to $\epsilon^{-7/3}$ and that the power does not depend on details of the underlying field theory. The calculation is done by using the effective Lagrangian method for the relevant soft (Goldstone) degrees of freedom in the problem. Unlike in the (1+1) dimensional case, where the decay rate is completely determined by the parameters of the effective Lagrangian and is thus insensitive to the specific details of the underlying (microscopic) theory, in the considered here (2+1) dimensional case the pre-exponential factor is found up to a constant, which does depend on specifics of the underlying short-distance dynamics, but does not depend on the energy asymmetry parameter $\epsilon$. Thus the functional dependence of the decay rate on $\epsilon$ is universally determined in the considered limit of small $\epsilon$.Comment: 10 page

Electromagnetic leptogenesis at the TeV scale

We construct an explicit model implementing electromagnetic leptogenesis. In a simple extension of the Standard Model, a discrete symmetry forbids the usual decays of the right-handed neutrinos, while allowing for an effective coupling between the left-handed and right-handed neutrinos through the electromagnetic dipole moment. This generates correct leptogenesis with resonant enhancement and also the required neutrino mass via a TeV scale seesaw mechanism. The model is consistent with low energy phenomenology and would have distinct signals in the next generation colliders, and, perhaps even the LHC.Comment: 14 pages, 2 eps figure

Heavy quark spin selection rule and the properties of the X(3872)

The properties of the resonance X(3872) are discussed under the assumption that this resonance is dominantly a `molecular' $J^{PC}=1^{++}$ state of neutral $D$ and $D^*$ mesons. It is argued that in these properties should dominate the states with the total spin of the charmed quark-antiquark pair equal to one. As a practical application of this observation the ratio of the rates of the decays $X \to \pi^0 \chi_{cJ}$ for different $J$ is predicted. It is also pointed out that the total rate of these decays is likely to be comparable to that of the observed transitions $X \to \pi^+ \pi^- J\psi$ and $X \to \pi^+ \pi^- \pi^0 J\psi$. The decays of the X into light hadrons and its production in hadronic processes are also briefly discussed.Comment: 7 page