We present the observation of doubly produced J/psi mesons with the D0 detector at Fermilab in p (p) over bar collisions at root s = 1.96 TeV. The production cross section for both singly and doubly ...produced J/psi mesons is measured using a sample with an integrated luminosity of 8.1 fb(-1). For the first time, the double J/psi production cross section is separated into contributions due to single and double parton scatterings. Using these measurements, we determine the effective cross section seff, a parameter characterizing an effective spatial area of the parton-parton interactions and related to the parton spatial density inside the nucleon.
This paper discusses the use of 3-D computational fluid dynamics (CFD) software for simulation of explosive detonations against the wearer of a typical bomb suit. The focus is to demonstrate the ...utility of the model to assess the differential overpressure loads on the various bomb suit components protecting critical body parts. Since overpressures can vary significantly depending on the position and orientation of the wearer, simulations are performed for a range of orientations including kneeling and standing at common standoff distances. Overpressure loads on the head, neck, and torso regions are predicted for each orientation, capturing ground and other surface reflections that can enhance effects of the blast. This is not normally observed during tests of individual bomb suit components. Direct correlations between the suit orientation and environmental factors to load enhancements are documented, and an effort to address probable injury is made.
We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset ...corresponding to an integrated luminosity of 5.4 fb-1, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
We present evidence for the exotic charged charmoniumlike state Zc±(3900) decaying to J/ψπ± in semi-inclusive weak decays of b-flavored hadrons. The signal is correlated with a parent J/ψπ+π− system ...in the invariant-mass range 4.2–4.7 GeV that would include the exotic structure Y(4260). The study is based on 10.4 fb−1 of pp¯ collision data collected by the D0 experiment at the Fermilab Tevatron collider.
We measure the charge asymmetry A of like-sign dimuon events in 6.1 fb(-1) of p (p) over bar collisions recorded with the D0 detector at a center-of-mass energy root s = 1.96 TeV at the Fermilab ...Tevatron collider. From A, we extract the like-sign dimuon charge asymmetry in semileptonic b-hadron decays: A(sl)(b) = -0.00957 +/- 0.00251 (stat) +/- 0.00146 (syst). This result differs by 3.2 standard deviations from the standard model prediction A(sl)(b)(SM) = (-2.3(0.6)(+0.5)) x 10(-4) and provides first evidence of anomalous CP violation in the mixing of neutral B mesons.
► An appropriate analytical method for predicting the spread of LNG on water is preseuted. ► A Semi-empirical method useful in analyzing pool fires is presented. ► A computational fluid dynamics ...model useful in calculating LNG vapor dispersion is validated against test data.
A methodology to perform consequence analysis associated with liquefied natural gas (LNG) for a deepwater port (DWP) facility has been presented. Analytical models used to describe the unconfined spill dynamics of LNG are discussed. How to determine the thermal hazard associated with a potential pool fire involving spilled LNG is also presented. Another hazard associated with potential releases of LNG is the dispersion of the LNG vapor. An approach using computational fluid dynamics tools (CFD) is presented. The CFD dispersion methodology is benchmarked against available test data. Using the proposed analysis approach provides estimates of hazard zones associated with newly proposed LNG deepwater ports and their potential impact to the public.
This paper discusses a new reduced model for vapor cloud explosions (VCEs) which incorporates some factors found in more complex models such as three-dimensional effects. The common foundation of all ...VCE analysis models is discussed and a simplified model based on a set of blast curves is reviewed to highlight the differences in the various model assumptions. Output from the reduced model is compared to experimental data and results from the simplified model. It is shown that the reduced model captures critical factors such as cloud shape and flame dynamics.
Computational modeling is routinely used in the design and development of explosive systems but is not typically applied in performing hazard assessments related to explosives. Typically simplified ...models are used to perform analysis related to safety and security applications involving explosives. These models can misrepresent the destructive output from explosive devices because they do not resolve many of the aspects of the scenarios such as wave reflection, channeling and focusing of blast waves. Here a computational model developed specifically for explosive hazard assessments is reviewed and the advantages as compared to simple models are highlighted. Some of the obstacle to applying computational modeling to routine explosive hazard assessment problems is the ability to perform analysis in a timely manner and address the wide range of explosives encountered. Here techniques being developed to increase flexibility in application and increase efficiency are presented.
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