5,732 research outputs found
Three-generation neutrino oscillations in curved spacetime
Three-generation MSW effect in curved spacetime is studied and a brief
discussion on the gravitational correction to the neutrino self-energy is
given. The modified mixing parameters and corresponding conversion
probabilities of neutrinos after traveling through celestial objects of
constant densities are obtained. The method to distinguish between the normal
hierarchy and inverted hierarchy is discussed in this framework. Due to the
gravitational redshift of energy, in some extreme situations, the resonance
energy of neutrinos might be shifted noticeably and the gravitational effect on
the self-energy of neutrino becomes significant at the vicinities of spacetime
singularities.Comment: 25 pages, 5 figures, 2 tables. Some changes are made according to
referee's suggestions. The final version is to be published at Nuclear
Physics
Estimating decay rate of while assuming them to be molecular states
Discovery of brings up a tremendous interest because it is very
special, i.e. made of four different flavors. The D0 collaboration claimed that
they observed this resonance through portal , but
unfortunately, later the LHCb, CMS, CDF and ATLAS collaborations' reports
indicate that no such state was found. Almost on the Eve of 2017, the D0
collaboration reconfirmed existence of via the semileptonic decay of
. To further reveal the discrepancy, supposing as a molecular
state, we calculate the decay rate of in an
extended light front model. Numerically, the theoretically predicted decay
width of is MeV which is
consistent with the result of the D0 collaboration
( MeV). Since the
resonance is narrow, signals might be drowned in a messy background. In analog,
two open-charm molecular states and named as and , could
be in the same situation. The rates of and
are estimated as about 30 MeV and 20 MeV respectively. We suggest the
experimental collaborations round the world to search for these two modes and
accurate measurements may provide us with valuable information.Comment: 13 pages and 4 figures, accepted by EPJ
How can escape detection?
Multi-quark states were predicted by Gell-Mann when the quark model was first
formulated. Recently, numerous exotic states that are considered to be
multi-quark states have been experimentally confirmed (four-quark mesons and
five-quark baryons). Theoretical research indicates that the four-quark state
might comprise molecular and/or tetraquark structures. We consider that the
meson containing four different flavors should exist and decay
via the channel. However, except for the D0 collaboration,
all other experimental collaborations have reported negative observations for
in this golden portal. This contradiction has stimulated the interest
of both theorists and experimentalists. To address this discrepancy, we propose
that the assumed is a mixture of a molecular state and tetraquark,
which contributes destructively to . The cancellation may be
accidental and it should be incomplete. In this scenario, there should be two
physical states with the same flavor ingredients, with spectra of
and . lies in the error range of the first state. We
predict the width of the second state (designated as ) as
MeV. We strongly suggest searching for it
in future experiments.Comment: pages 4. Accepted by phys. lett.
Unparticle Physics Effects on D0-anti-D0 Mixing
The mixing of , and
provides a sensitive probe to explore new physics
beyond the Standard Model. The scale invariant unparticle physics recently
proposed by Georgi can induce flavor-changing neutral current and contribute to
the mixing at tree level. We investigate the unparticle effects on
and mixing. Especially, the newly observed
mixing sets the most stringent constraints on the coupling of
the unparticle to quarks.Comment: 9 pages, some errors corrected, published versio
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