597 research outputs found
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 and states in the annihilations
Productions and decays of spin-singlet wave charmonium states,
and , in the 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 , , keV
and 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 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
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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 of the energy density between the metastable and the
stable vacua. It is shown that this factor is proportional to
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 . Thus the functional
dependence of the decay rate on is universally determined in the
considered limit of small .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' state of
neutral and 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 for different 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 and . The decays of the X into light hadrons and its
production in hadronic processes are also briefly discussed.Comment: 7 page
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