65 research outputs found
Noise reduction through joint processing of gravity and gravity gradient data
International audienceIn mineral and oil exploration, gravity gradient data can help to delineate small-scale features that cannot be retrieved from gravity measurements. Removing high-frequency noise while preserving the high-frequency real signal is one of the most challenging tasks associated with gravity gradi-ometry data processing. We present a method to reduce gravity and gravity gradient data noise when both are measured in the same area, based on a least-squares simultaneous inversion of observations and physical constraints, inferred from the gravity gradient tensor definition and its mathematical properties. Instead of handling profiles individually, our noise-reduction method uses simultaneously measured values of the tensor components and of gravity in the whole survey area, benefiting from all available information. Synthetic examples show that more than half of the random noise can be removed from all tensor components and nearly all the noise from the gravity anomaly without altering the high-frequency information. We apply our method to a set of marine gravity gradiometry data acquired by Bell Geospace in the Faroe-Shetland Basin to demonstrate its power to resolve small-scale features
Decays of the Exotic Hybrid and - Mixing
QCD sum-rules are used to calculate the decay widths of the exotic hybrid in two different
mixing schemes.
In the conventional flavour octet-singlet mixing scheme, the decay widths are
both found to be small, while in the recently-proposed quark mixing scheme, the
decay width is large compared with
the decay width . These
results provide some insight into - mixing and hybrid decay
features.Comment: latex2e, 11 pages with 4 embedded eps figures. v 2 corrects reference
[5] and minor error in equation (11
Decay of heavy-light hybrids in HQET sum rules
The decay widths of the 0^{++} and 1^{-+} heavy-light hybrids to B(D) and
pion are calculated by using the QCD sum rules. The interpolated current of the
hybrid is chosen as . In
order to simplify the calculation and avoid the ambiguity of three-point
correlation function, a two-point correlation function between the pion and
vacuum is used instead. The decay width of the is about 12(16)
MeV while the is around 0.4(1.8) MeV. We keep the leading
order of 1/M_Q expansion in our calculation for convenience.Comment: 14 pages, latex file, 4 ps figs, Published version, some numerical
results change
Hybrid configuration content of heavy S-wave mesons
We use the non-relativistic expansion of QCD (NRQCD) on the lattice to study
the lowest hybrid configuration contribution to the ground state of heavy
S-wave mesons. Using lowest-order lattice NRQCD to create the heavy-quark
propagators, we form a basis of ``unperturbed'' S-wave and hybrid states. We
then apply the lowest-order coupling of the quark spin and chromomagnetic field
at an intermediate time slice to create ``mixed'' correlators between the
S-wave and hybrid states. From the resulting amplitudes, we extract the
off-diagonal element of our two-state Hamiltonian. Diagonalizing this
Hamiltonian gives us the admixture of hybrid configuration within the meson
ground state. The present effort represents a continuation of previous work:
the analysis has been extended to include lattices of varying spacings, source
operators having better overlap with the ground states, and the pseudoscalar
(along with the vector) channel. Results are presented for bottomonium
(, ) using three different sets of quenched lattices. We
also show results for charmonium (, ) from one lattice set,
although we note that the non-relativistic approximation is not expected to be
very good in this case.Comment: 9 pages, 7 figures, version to appear in Phys Rev
Can the Mechanism for Hybrid Decays be Detected?
Two mechanisms for the () hybrid meson decay processes
are investigated. These mechanisms are applied to
and decays to
illustrate the validity of the decay mechanisms and to obtain independent
information on the coupling of to quark and gluonic operators.
From this information, we find that
is substantially different
in the two decay mechanisms, and hence future experimental measurements of this
ratio will provide valuable information for substantiating the hybrid nature of
these states and for determining the mechanism for these hybrid decays.Comment: 5 pages, revtex, 1 eps figure embedded in manuscript. Analysis and
references extended in v
A Study of the \eta \pi^{0} Spectrum and Search for a J^{PC} = 1^{-+} Exotic Meson
A partial wave analysis (PWA) of the of the system (where ) produced in the charge exchange reaction at an incident momentum of 18 GeV is presented as a function of
invariant mass, , and momentum transfer squared,
, from the incident to the outgoing system. , and waves were included in the PWA. The
and states are clearly observed in the overall
effective mass distribution as well as in the amplitudes associated with
wave and waves respectively after partial wave decomposition. The observed
distributions in moments (averages of spherical harmonics) were compared to the
results from the PWA and the two are consistent. The distribution in
for individual waves associated with natural and
unnatural parity exchange in the -channel are consistent with Regge
phenomenology. Of particular interest in this study is the wave since this
leads to an exotic for the system. A wave is
present in the data, however attempts to describe the mass dependence of the
amplitude and phase motion with respect to the wave as a Breit-Wigner
resonance are problematic. This has implications regarding the existence of a
reported exotic meson decaying into with a mass
near 1.4 GeV.Comment: 19 pages, 29 figures, to appear in Phys. Rev.
NS3 protease polymorphism and natural resistance to protease inhibitors in French patients infected with HCV genotypes 1â5
Background: Resistant HCV populations may pre-exist in patients before NS3 protease inhibitor therapy and would likely be selected under specific antiviral pressure. The higher prevalence and lower rate of response to treatment associated with HCV genotype 1 infections has led to drug discovery efforts being focused primarily on enzymes produced by this genotype. Protease inhibitors may also be useful for non-genotype-1-infected patients, notably for non-responders.Methods: We investigated the prevalence of dominant resistance mutations and polymorphism in 298 HCV protease-inhibitor-naive patients infected with HCV genotypes 1, 2, 3, 4 or 5. Genotype-specific NS3 primers were designed to amplify and sequence the NS3 protease gene. Results: None of the 233 analysed sequences contained major telaprevir (TVR) or boceprevir (BOC) resistance mutations (R155K/T/M, A156S/V/T and V170A). Some substitutions (V36L, T54S, Q80K/R, D168Q and V170T) linked to low or moderate decreases in HCV sensitivity to protease inhibitors were prevalent according to genotype (between 2% and 100%). Other than genotype signature mutations at positions 36, 80 and 168, the most frequent substitution was T54S (4 genotype 1 and 2 genotype 4 sequences). All genotype 2â5 sequences had the non-genotype-1 signature V36L mutation known to confer low-level resistance to both TVR and BOC. Conclusions: We have developed an HCV protease NS3 inhibitor resistance genotyping tool suitable for use with HCV genotypes 1â5. Polymorphism data is valuable for interpreting genotypic resistance profiles in cases of failure of anti-HCV NS3 protease treatment
Evidence for Exotic J^{PC}=1^{-+} Meson Production in the Reaction pi- p --> eta pi- p at 18 GeV/c
Details of the analysis of the eta pi- system studied in the reaction pi^{-}
p --> eta pi^{-} p at 18 GeV/c are given. Separate analyses for the 2 gamma and
pi+ pi- pi0 decay modes of the eta are presented. An amplitude analysis of the
data indicates the presence of interference between the a(2)(1320)- and a
J^{PC}=1^{-+} wave between 1.2 and 1.6 GeV/c^2. The phase difference between
these waves shows phase motion not attributable solely to the a(2)(1320)-. The
data can be fitted by interference between the a(2)(1320)- and an exotic 1^{-+}
resonance with M = 1370 +-16 +50 -30} MeV/c^2 and Gamma = 385 +- 40 +65 -105
MeV/c^2. Our results are compared with those of other experiments.Comment: 50 pages of text and 34 figure
Interpretation of Experimental J^PC Exotic Signals
We investigate theoretical interpretations of the 1.4 GeV J^PC exotic
resonance reported by the E852 collaboration. It is argued that interpretation
in terms of a hybrid meson is untenable. A K-matrix analysis shows that the 1.4
GeV enhancement in the E852 eta pi data can be understood as an interference of
a non-resonant Deck-type background and a resonance at 1.6 GeV. A final state
rescattering calculation shows that the 1.6 GeV hybrid has a eta pi width which
is bounded above by 57 \pm 14 MeV.Comment: 23 pages, LaTeX, 4 encapsulated postscript figures. Accepted for
publication by Physical Review
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