275 research outputs found
Monogenean gill parasites of Indian major carps from different fish farms of Mymensingh, Bangladesh
All together 148 fish host samples of Labeo rohira, Cirrhina mrigala, Catla catla and
Labeo gonius were collected from different fish farms of Mymensingh. The gill
monogeneans were then dislodged from the gill under dissecting microscope and fixed in
ammonium picrate. Five species of Dactylogyrus namely, Dactylogyrus mrigali, D.
chauhanus, D. yogendrai, D. labei and D. kalyanensis were recovered from sampled
fishes. All the parasites were studied and redescribed, and reported for the first time from
Bangladesh. The present investigation established Catla catla as a new host of D. labei
Some aspects of association and development of Lytocestus indicus Moghe in catfish Clarias batrachus (Lin.)
Some aspects of association and development of the caryophyllid cestode Lytocestus indicus Moghe, 1925 infecting the catfish Clarias batrachus (Linn.) from the Kailla Beel of Mymensingh, Bangladesh were studied. About 33.14% of Clarias batrachus were infected with a mean intensity of 3.75, mean density 1.25. The infection was not found throughout the year. Two seasonal occurrence of this cestode were observed, one in April-May and the other in August-September. However, maturation period of the worm coincided with the maturation of the host. The worm was found attached to the wall of the intestine of the host. At the site of attachment tissue layers were compressed due to mechanical injuries. Prevalence and mean intensity of infection increased with length groups. No variation in infection was significantly observed in different sexes of the host examined
The SNâIa runaway LPâ398-9 : detection of circumstellar material and surface rotation
A promising progenitor scenario for Type Ia supernovae (SNeIa) is the thermonuclear detonation of a white dwarf in a close binary system with another white dwarf. After the primary star explodes, the surviving donor can be spontaneously released as a hypervelocity runaway. One such runaway donor candidate is LPâ398-9, whose orbital trajectory traces back â105 yr to a known supernova remnant. Here, we report the discovery of carbon-rich circumstellar material around LPâ398-9, revealed by a strong infrared excess and analysed with follow-up spectroscopy. The circumstellar material is most plausibly composed of inflated layers from the star itself, mechanically and radioactively heated by the past companionâs supernova. We also detect a 15.4âh periodic signal in the UV and optical light curves of LPâ398-9, which we interpret as surface rotation. The rotation rate is consistent with theoretical predictions from this supernova mechanism, and the brightness variations could originate from surface inhomogeneity deposited by the supernova itself. Our observations strengthen the case for this double-degenerate SNIa progenitor channel, and motivate the search for more runaway SNIa donors
Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for the production of neutral Higgs bosons decaying into
tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The
data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by
the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the
95% C.L. on the product of production cross section and branching ratio for a
scalar resonance decaying into tautau pairs, and we then interpret these limits
as limits on the production of Higgs bosons in the minimal supersymmetric
standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL
Measurement of the photon-jet production differential cross section in collisions at \sqrt{s}=1.96~\TeV
We present measurements of the differential cross section dsigma/dpT_gamma
for the inclusive production of a photon in association with a b-quark jet for
photons with rapidities |y_gamma|< 1.0 and 30<pT_gamma <300 GeV, as well as for
photons with 1.5<|y_gamma|< 2.5 and 30< pT_gamma <200 GeV, where pT_gamma is
the photon transverse momentum. The b-quark jets are required to have pT>15 GeV
and rapidity |y_jet| < 1.5. The results are based on data corresponding to an
integrated luminosity of 8.7 fb^-1, recorded with the D0 detector at the
Fermilab Tevatron Collider at sqrt(s)=1.96 TeV. The measured cross
sections are compared with next-to-leading order perturbative QCD calculations
using different sets of parton distribution functions as well as to predictions
based on the kT-factorization QCD approach, and those from the Sherpa and
Pythia Monte Carlo event generators.Comment: 10 pages, 9 figures, submitted to Phys. Lett.
Limits on anomalous trilinear gauge boson couplings from WW, WZ and Wgamma production in pp-bar collisions at sqrt{s}=1.96 TeV
We present final searches of the anomalous gammaWW and ZWW trilinear gauge
boson couplings from WW and WZ production using lepton plus dijet final states
and a combination with results from Wgamma, WW, and WZ production with leptonic
final states. The analyzed data correspond to up to 8.6/fb of integrated
luminosity collected by the D0 detector in pp-bar collisions at sqrt{s}=1.96
TeV. We set the most stringent limits at a hadron collider to date assuming two
different relations between the anomalous coupling parameters
Delta\kappa_\gamma, lambda, and Delta g_1^Z for a cutoff energy scale Lambda=2
TeV. The combined 68% C.L. limits are -0.057<Delta\kappa_\gamma<0.154,
-0.015<lambda<0.028, and -0.008<Delta g_1^Z<0.054 for the LEP parameterization,
and -0.007<Delta\kappa<0.081 and -0.017<lambda<0.028 for the equal couplings
parameterization. We also present the most stringent limits of the W boson
magnetic dipole and electric quadrupole moments.Comment: 10 pages, 5 figures, submitted to PL
Measurement of three-jet differential cross sections d sigma-3jet / d M-3jet in p anti-p collisions at sqrt(s)=1.96 TeV
We present the first measurement of the inclusive three-jet differential
cross section as a function of the invariant mass of the three jets with the
largest transverse momenta in an event in p anti-p collisions at sqrt(s) = 1.96
TeV. The measurement is made in different rapidity regions and for different
jet transverse momentum requirements and is based on a data set corresponding
to an integrated luminosity of 0.7 fb^{-1} collected with the D0 detector at
the Fermilab Tevatron Collider. The results are used to test the three-jet
matrix elements in perturbative QCD calculations at next-to-leading order in
the strong coupling constant. The data allow discrimination between
parametrizations of the parton distribution functions of the proton.Comment: 10 pages, 4 figures, 2 tables, submitted to Phys. Lett. B, corrected
chi2 values for NNPD
Search for pair production of the scalar top quark in muon+tau final states
We present a search for the pair production of scalar top quarks
(), the lightest supersymmetric partners of the top quarks, in
collisions at a center-of-mass energy of 1.96 TeV, using data
corresponding to an integrated luminosity of {7.3 } collected with the
\dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is
assumed to decay into a quark, a charged lepton, and a scalar neutrino
(). We investigate final states arising from and
. With no significant excess of events observed above the
background expected from the standard model, we set exclusion limits on this
production process in the (,) plane.Comment: Submitted to Phys. Lett.
Measurement of spin correlation in ttbar production using dilepton final states
We measure the correlation between the spin of the top quark and the spin of
the anti-top quark in (ttbar -> W+ W- b bbar -> l+ nu b l- nubar bbar) final
states produced in ppbar collisions at a center of mass energy sqrt(s)=1.96
TeV, where l is an electron or muon. The data correspond to an integrated
luminosity of 5.4 fb-1 and were collected with the D0 detector at the Fermilab
Tevatron collider. The correlation is extracted from the angles of the two
leptons in the t and tbar rest frames, yielding a correlation strength C=
0.10^{+0.45}_{-0.45}, in agreement with the NLO QCD prediction within two
standard deviations, but also in agreement with the no correlation hypothesis.Comment: 10 pages, 3 figures, submitted to PL
Measurements of inclusive W+jets production rates as a function of jet transverse momentum in ppbar collisions at sqrt{s}=1.96 TeV
This Letter describes measurements of inclusive W (--> e nu) + n jet cross
sections (n = 1-4), presented as total inclusive cross sections and
differentially in the nth jet transverse momentum. The measurements are made
using data corresponding to an integrated luminosity of 4.2 fb-1 collected by
the D0 detector at the Fermilab Tevatron Collider, and achieve considerably
smaller uncertainties on W +jets production cross sections than previous
measurements. The measurements are compared to next-to-leading order
perturbative QCD (pQCD) calculations in the n =1-3 jet multiplicity bins and to
leading order pQCD calculations in the 4-jet bin. The measurements are
generally in agreement with pQCD predictions, although certain regions of phase
space are identified where the calculations could be improved
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