3,257 research outputs found
Decoherence induced CPT violation and entangled neutral mesons
We discuss two classes of semi-microscopic theoretical models of stochastic
space-time foam in quantum gravity and the associated effects on entangled
states of neutral mesons, signalling an intrinsic breakdown of CPT invariance.
One class of models deals with a specific model of foam, initially constructed
in the context of non-critical (Liouville) string theory, but viewed here in
the more general context of effective quantum-gravity models. The relevant
Hamiltonian perturbation, describing the interaction of the meson with the foam
medium, consists of off-diagonal stochastic metric fluctuations, connecting
distinct mass eigenstates (or the appropriate generalisation thereof in the
case of K-mesons), and it is proportional to the relevant momentum transfer
(along the direction of motion of the meson pair). There are two kinds of
CPT-violating effects in this case, which can be experimentally disentangled:
one (termed ``omega-effect'') is associated with the failure of the
indistinguishability between the neutral meson and its antiparticle, and
affects certain symmetry properties of the initial state of the two-meson
system; the second effect is generated by the time evolution of the system in
the medium of the space-time foam, and can result in time-dependent
contributions of the $omega-effect type in the time profile of the two meson
state. Estimates of both effects are given, which show that, at least in
certain models, such effects are not far from the sensitivity of experimental
facilities available currently or in the near future. The other class of
quantum gravity models involves a medium of gravitational fluctuations which
behaves like a ``thermal bath''. In this model both of the above-mentioned
intrinsic CPT violation effects are not valid.Comment: 16 pages revtex, no figure
Accurate measurement of telemetry performance
Performance of high rate telemetry stations used in the Deep Space Network is verified. Measurement techniques are discussed
Explicit CP violation in the Dine-Seiberg-Thomas model
The possibility of explicit CP violation is studied in a supersymmetric model
proposed by Dine, Seiberg, and Thomas, with two effective dimension-five
operators. The explicit CP violation may be triggered by complex phases in the
coefficients for the dimension-five operators in the Higgs potential, and by a
complex phase in the scalar top quark masses. Although the scenario of explicit
CP violation is found to be inconsistent with the experimental data at LEP2 at
the tree level, it may be possible at the one-loop level. For a reasonable
parameter space, the masses of the neutral Higgs bosons and their couplings to
a pair of bosons are consistent with the LEP2 data, at the one-loop level.Comment: 5 pages, 2 figure
Spontaneous Violation of the CP Symmetry in the Higgs Sector of the Next-to-Minimal Supersymmetric Model
The spontaneous violation of the CP symmetry in the next-to-minimal
supersymmetric standard Model (NMSSM) is investigated. It is found that the
spontaneous violation of the CP symmetry can occur in the Higgs sector of the
NMSSM for a wide region of the parameter space of the model, at the 1-loop
level where the radiative corrections due to the top quark and scalar-top quark
loops are found to generate the scalar-pseudoscalar mixings between the two
Higgs doublets of the NMSSM. In our model, we assume that the masses of the
left-handed and the right-handed scalar-top quarks are not degenerate. And we
investigate our model anaytically: We derive analytical formulae of the 1-loop
mass matrix for the neutral Higgs bosons. We calculate the upper bound on the
lightest neutral Higgs boson mass under the assumption. It is found to be about
140 GeV for our choice of parameter values in the presence of the spontaneous
violation of the CP symmetry in the NMSSM. Thus, the possibility of the
spontaneous violation of the CP symmetry is not completely ruled out in the
Higgs sector of the NMSSM if the masses of the left-handed and the right-handed
scalar-top quarks are not degenerate. Further, the phenomenology of the
- mixing within the context of our model is studied. The lower
bound on CP violating phase in the - mixing is found to increase
if either decreases or increases.Comment: 21 pages, 5 figures, To appear in Phys. Rev.
Charged Higgs boson in the next-to-minimal supersymmetric standard model with explicit CP violation
The phenomenology of the explicit CP violation in the Higgs sector of the
next-to-minimal supersymmetric standard model (NMSSM) is investigated, with
emphasis on the charged Higgs boson. The radiative corrections due to both
quarks and scalar-quarks of the third generation are taken into account, and
the negative result of the search for the Higgs bosons at CERN LEP2, with the
discovery limit of 0.1 pb, is imposed as a constraint. It is found that there
are parameter regions of the NMSSM where the lightest neutral Higgs boson may
even be massless, without being detected at LEP2. This implies that the LEP2
data do not contradict the existence of a massless neutral Higgs boson in the
NMSSM. For the charged Higgs boson, the radiative corrections to its mass may
be negative in some parameter regions of the NMSSM. The phenomenological lower
bound on the radiatively corrected mass of the charged Higgs boson is increased
as the CP violation becomes maximal, i.e., as the CP violating phase becomes
. At the maximal CP violation, its lower bound is about 110 GeV for 5
40. The vacuum expectation value (VEV) of the
neutral Higgs singlet is shown to be no smaller than 16 GeV for any parameter
values of the NMSSM with explicit CP violation. This value of the lower limit
is found to increase up to about 45 GeV as the ratio () of the VEVs
of the two Higgs doublets decreases to smaller values ( 2). The discovery
limit of the Higgs boson search at LEP2 is found to cover about a half of the
kinematically allowed part of the whole parameter space of the NMSSM, and the
portion is roughly stable against the CP violating phase.Comment: Latex, 24 pages, 6 figure
Neutral Higgs sector of the next-to-minimal supersymmetric standard model with explicit CP violation
The neutral Higgs sector of the next-to-minimal supersymmetric standard model
(NMSSM) with explicit CP violation is investigated at the 1-loop level, using
the effective potential method; not only the loops involving the third
generation of quarks and scalar quarks, but also the loops involving boson,
charged Higgs boson, and chargino are taken into account. It is found that for
some parameter values of the NMSSM the contributions from the boson,
charged Higgs boson, and chargino loops may modify the masses of the neutral
Higgs bosons and the mixings among them significantly, depending on the CP
phase. In collisions, the prospects for discovering neutral Higgs
bosons are investigated within the context of the NMSSM with explicit CP
violation when the dominant component of the lightest neutral Higgs boson is
the Higgs singlet field of the NMSSM.Comment: Latex, 23 pages, 6 figure
Possibility of spontaneous CP violation in the nonminimal supersymmetric standard model with two neutral Higgs singlets
A supersymmetric standard model with two Higgs doublets and two Higgs
singlets is investigated if it can accommodate the possibility of spontaneous
CP violation. Assuming the degeneracy of the scalar quark masses of the third
generation, we find that spontaneous CP violation in the Higgs sector is viable
in our model. In the case of spontaneous CP violation, the masses of the
lightest two neutral Higgs bosons are estimated to be 80 and 125 GeV for some
parameter values in our model, which, are consistent with LEP2 data.Comment: 18 pages, 3figure
Method of extending hyperfine coherence times in Pr^3+:Y_2SiO_5
In this letter we present a method for increasing the coherence time of
praseodymium hyperfine ground state transitions in Pr^3+:Y_2SiO_5 by the
application of a specific external magnetic field. The magnitude and angle of
the external field is applied such that the Zeeman splitting of a hyperfine
transition is at a critical point in three dimensions, making the first order
Zeeman shift vanishingly small for the transition. This reduces the influence
of the magnetic interactions between the praseodymium ions and the spins in the
host lattice on the transition frequency. Using this method a phase memory time
of 82ms was observed, a value two orders of magnitude greater than previously
reported. It is shown that the residual dephasing is amenable quantum error
correction
Neutral Higgs bosons in the MNMSSM with explicit CP violation
Within the framework of the minimal non-minimal supersymmetric standard model
(MNMSSM) with tadpole terms, CP violation effects in the Higgs sector are
investigated at the one-loop level, where the radiative corrections from the
loops of the quark and squarks of the third generation are taken into account.
Assuming that the squark masses are not degenerate, the radiative corrections
due to the stop and sbottom quarks give rise to CP phases, which trigger the CP
violation explicitly in the Higgs sector of the MNMSSM. The masses, the
branching ratios for dominant decay channels, and the total decay widths of the
five neutral Higgs bosons in the MNMSSM are calculated in the presence of the
explicit CP violation. The dependence of these quantities on the CP phases is
quite recognizable, for given parameter values.Comment: 25 pages, 8 figure
Successive use of shared space by badgers and cattle: implications for Mycobacterium bovis transmission
Managing infectious disease demands understanding pathogen transmission. In Britain, transmission of Mycobacterium bovis from badgers (Meles meles) to cattle hinders the control of bovine tuberculosis (TB), but the mechanism of such transmission is uncertain. As badgers and cattle seldom interact directly, transmission might occur in their shared environment through contact with contamination such as faeces, urine and saliva. We used concurrent GPS collar tracking of badgers and cattle at four sites in Cornwall, southwest Britain, to test whether each species used locations previously occupied by the other species, within the survival time of M. bovis bacteria. Although analyses of the same data set showed that badgers avoided cattle, we found no evidence that this avoidance persisted over time: neither GPS-collared badgers nor cattle avoided space which had been occupied by the other species in the preceding 36 h. Defining a contact event as an animal being located <5 m from space occupied by the other species within the previous 36 h, we estimated that a herd of 176 cattle (mean herd size in our study areas) would contact badgers at least 6.0 times during an average 24-h period. Similarly, we estimated that a social group of 3.5 badgers (mean group size in our study areas) would contact cattle at least 0.76 times during an average night. Such frequent successive use of the same shared space, within the survival time of M. bovis bacteria, could potentially facilitate M. bovis transmission via the environment
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