473 research outputs found
The non-perturbative unquenched quark model
In recent years states in the quarkonium spectrum not expected in the naive quark model have appeared and created a lot of interest. In the theoretical side the study of the effect of meson-meson thresholds in the spectrum have been performed in different approximations. In a quark model framework, and in the spirit of the Cornell model, when a meson-meson threshold is included, the coupling to all the quark-antiquark states have to be considered. In practice only the closest states are included perturbatively. In this contribution we will present a framework in which we couple quark-antiquark states with meson-meson states non-perturbatively, taking into account effectively the coupling to all quark-antiquark states. The method will be applied to the study of the X(3872) and a comparison with the perturbative calculation will be performed
Bidecadal North Atlantic ocean circulation variability controlled by timing of volcanic eruptions
International audienceWhile bidecadal climate variability has been evidenced in several North Atlantic paleoclimaterecords, its drivers remain poorly understood. Here we show that the subset of CMIP5historical climate simulations that produce such bidecadal variability exhibits a robustsynchronization, with a maximum in Atlantic Meridional Overturning Circulation (AMOC) 15years after the 1963 Agung eruption. The mechanisms at play involve salinity advection fromthe Arctic and explain the timing of Great Salinity Anomalies observed in the 1970s and the1990s. Simulations, as well as Greenland and Iceland paleoclimate records, indicate thatcoherent bidecadal cycles were excited following five Agung-like volcanic eruptions of the lastmillennium. Climate simulations and a conceptual model reveal that destructive interferencecaused by the Pinatubo 1991 eruption may have damped the observed decreasing trend of theAMOC in the 2000s. Our results imply a long-lasting climatic impact and predictabilityfollowing the next Agung-like eruption
Impact of tetanus-diphtheria-acellular pertussis immunization during pregnancy on subsequent infant immunization seroresponses : follow-up from a large randomized placebo-controlled trial
Background: Pertussis immunization during pregnancy results in high pertussis antibody concentrations in young infants but may interfere with infant immune responses to post-natal immunization. Methods: This phase IV, multi-country, open-label study assessed the immunogenicity and safety of infant primary vaccination with DTaP-HepB-IPV/Hib and 13-valent pneumococcal conjugate vaccine (PCV13). Enrolled infants (6\u201314 weeks old) were born to mothers who were randomized to receive reduced-antigen-content diphtheria-tetanus-three-component acellular pertussis vaccine (Tdap group) or placebo (control group) during pregnancy (270/7\u2013366/7 weeks\u2019 gestation) with crossover immunization postpartum. All infants received 2 or 3 DTaP-HepB-IPV/Hib and PCV13 doses according to national schedules. Immunogenicity was assessed in infants pre- and 1 month post-primary vaccination. The primary objective was to assess seroprotection/vaccine response rates for DTaP-HepB-IPV/Hib antigens 1 month post-primary vaccination. Results: 601 infants (Tdap group: 296; control group: 305) were vaccinated. One month post-priming, seroprotection rates were 100% (diphtheria; tetanus), 6598.5% (hepatitis B), 6595.9% (polio) and 6594.5% (Hib) in both groups. Vaccine response rates for pertussis antigens were significantly lower in infants whose mothers received pregnancy Tdap (37.5\u201377.1%) versus placebo (90.0\u201399.2%). Solicited and unsolicited adverse event rates were similar between groups. Serious adverse events occurred in 2.4% (Tdap group) and 5.6% (control group) of infants, none were vaccination-related. Conclusions: Pertussis antibodies transferred during pregnancy may decrease the risk of pertussis infection in the first months of life but interfere with the infant's ability to produce pertussis antibodies, the clinical significance of which remains unknown. Safety and reactogenicity results were consistent with previous experience
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.
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