D0 Data Research Articles

Large dimuon asymmetry in [formula omitted] mixing from unparticle induced [formula omitted

Exchange of unparticle stuff of dimension dU with FCNC interaction can induce M12,u and Γ12,u causing meson and antimeson mixing with the relation Γ12,u/M12,u=2tan(πdU). We show that this type of unparticle contribution can provide the much needed large Γs12 to explain the recently observed anomalously large dimuon asymmetry in Bs–B¯s system reported by D0 Collaboration. The same interaction can also accommodate large mixing induced CP violation in Bs→J/ψϕ indicated by CDF and D0 data. Experimental data can provide constraints on the unparticle dimension and scale.

Higgs-mediated FCNCs: natural flavour conservation vs. minimal flavour violation

We compare the effectiveness of two hypotheses, Natural Flavour Conservation (NFC) and Minimal Flavour Violation (MFV), in suppressing the strength of flavour-changing neutral-currents (FCNCs) in models with more than one Higgs doublet. We show that the MFV hypothesis, in its general formulation, is more stable in suppressing FCNCs than the hypothesis of NFC alone when quantum corrections are taken into account. The phenomenological implications of the two scenarios are discussed analysing meson-antimeson mixing observables and the rare decays B -> mu+ mu-. We demonstrate that, introducing flavour-blind CP phases, two-Higgs doublet models respecting the MFV hypothesis can accommodate a large CP-violating phase in Bs mixing, as hinted by CDF and D0 data and, without extra free parameters, soften significantly in a correlated manner the observed anomaly in the relation between epsilon_K and S_psi_K.

Fragmentation of a Single Molten Metal Droplet Penetrating Sodium Pool I Copper Droplet and the Relationship with Copper Jet

The progression of hypothetical core disruptive accidents in metallic fuel fast breeder reactors is strongly affected by the fragmentation of molten metallic fuels due to the molten fuel-coolant interaction (FCI). As a basic study of FCI, the present paper focuses on the fragmentation of a single molten copper droplet with mass from 1 to 5 g, whichpenetrated a sodium pool at instantaneous contact interface temperatures (Ti) from 995 to 1,342°C. Intensive fragmentation of a single molten copper droplet was clearly observed even if Ti values are below the melTsing point (1,083°C) of copper besides the higher Ti range. The intensive fragmentation shows that the mass median diameters (Dm) of copper droplets with a fivefold difference in mass or the same mass have little difference, i.e., they are nearly the same. Under the lower Ti condition, the Dm data of droplet fragments of both the same and different masses scatter widely. It is found that the present Dm/D0 data of mass median diameter normalized by the diameter before touching sodium (D0) give a distribution with larger values than those of molten copper jets with large mass from 20 to 300 g under the lower Ti condition, which were previously reported by the authors, because of the limited amount of heat of droplets. The present Dm=D0 data under the higher Ti condition are found to show an effecTive fragmentation compared with those of molten copper jets with a large mass of 4 kg.

Fragmentation of a Single Molten Metal Droplet Penetrating Sodium Pool I Copper Droplet and the Relationship with Copper Jet

The progression of hypothetical core disruptive accidents in metallic fuel fast breeder reactors is strongly affected by the fragmentation of molten metallic fuels due to the molten fuel-coolant interaction (FCI). As a basic study of FCI, the present paper focuses on the fragmentation of a single molten copper droplet with mass from 1 to 5 g, whichpenetrated a sodium pool at instantaneous contact interface temperatures (Ti) from 995 to 1,342°C. Intensive fragmentation of a single molten copper droplet was clearly observed even if Ti values are below the melTsing point (1,083°C) of copper besides the higher Ti range. The intensive fragmentation shows that the mass median diameters (Dm) of copper droplets with a fivefold difference in mass or the same mass have little difference, i.e., they are nearly the same. Under the lower Ti condition, the Dm data of droplet fragments of both the same and different masses scatter widely. It is found that the present Dm/D0 data of mass median diameter normalized by the diameter before touching sodium (D0) give a distribution with larger values than those of molten copper jets with large mass from 20 to 300 g under the lower Ti condition, which were previously reported by the authors, because of the limited amount of heat of droplets. The present Dm=D0 data under the higher Ti condition are found to show an effecTive fragmentation compared with those of molten copper jets with a large mass of 4 kg.

Diffractive hadroproduction ofW±andZ0bosons at high energies

Results from a phenomenological analysis of $W$ and $Z$ hard diffractive hadroproduction at high energies are reported. Using the Regge factorization approach, we consider the recent diffractive parton density functions extracted by the H1 Collaboration at DESY-HERA. In addition, we take into account multiple Pomeron exchange corrections considering a gap survival probability factor. It is found that the ratio of diffractive to nondiffractive boson production is in good agreement with the CDF and D0 data. We make predictions which could be compared to future measurements at the LHC.

Bond analyses of borates from the Inorganic Crystal Structure Database

Various fundamental building blocks (FBBs) are observed in the crystallographic structures of oxoborates available in the Inorganic Crystal Structure Database, Version 1.3.3 (2004); the occurrence of borate groups with low complexity is dominant. Bond-valence parameters d(0) of B-O bonds in 758 oxoborates with various FBBs have been calculated using the bond-valence sum model. Some discrepancies in the d(0) values obviously occur if the detailed configurations of FBBs in borate crystals are considered; d(0) is sensitive to the chemical bonding structure of B atoms in the crystallographic framework. Moreover, d(0) values are affected by the existence of interstitial atoms and the substitution of other anionic groups. In addition, the d(0) parameters for B-N, B-S, B-P and B-F bonds are also calculated statistically. Some suitable d(0) data for various borate FBBs are recommended according to their particular configurations, especially for those with low complexity. On the basis of the proposed linear relationship between calculated nonlinear optical (NLO) coefficients of borates and the current d(0) values for various FBBs, it is found that the d(0) values may be regarded as a useful parameter for pre-investigating the NLO properties of borates, leading to an efficient structural evaluation and design of novel borates.

Probing a Very NarrowZ′Boson with CDF and D0 Data

The CDF and D0 data of nearly 475 pb(-1) in the dilepton channel is used to probe a recent class of models, Stueckelberg extensions of the standard model (StSM), which predict a Z' boson whose mass is of topological origin with a very narrow decay width. A Drell-Yan analysis for dilepton production via this Z' shows that the current data put constraints on the parameter space of the StSM. With a total integrated luminosity of 8 fb(-1), the very narrow can be discovered up to a mass of about 600 GeV. The StSM Z' will be very distinct since it can occur in the region where a Randall-Sundrum graviton is excluded.

Unintegrated CCFM parton distributions and transverse momentum of gauge bosons

Transverse momentum distribution of gauge bosons W ± and Z 0 is calculated using unintegrated parton distributions obtained by solving leading order CCFM equation(s) in the impact parameter space. For illustration we compare the results of the fixed-order collinear, soft-gluon resummation and CCFM approaches. A parameter of a nonperturbative form factor is adjusted to the D0 data. In contrast to the collinear approach, the leading order calculation based on the unintegrated CCFM parton distributions generates transverse momentum distributions of gauge bosons, which are almost consistent with experimental data provided the parameter of the nonperturbative form factor is appropriately adjusted. The W +– W − asymmetry is calculated as a function of the boson rapidity and transverse momentum. Predictions are given for RHIC and LHC.

Soft gluon resummation in transverse momentum space for electroweak boson production at hadron colliders

The distribution of W and Z bosons produced with small transverse momentum ( $p_{\rm T}$ ) at hadron colliders receives important contributions from large logarithms arising from soft gluon emission. Although conventionally the all-orders resummation of these ‘Sudakov’ logarithms is performed in impact parameter (Fourier transform) space, $p_{\rm T}$ -space resummation is also possible, and offers certain advantages. We present a detailed phenomenological analysis of W and Z production at small $p_{\rm T}$ at the Tevatron $p \bar p$ collider, using $p_{\rm T}$ -space resummation. A good description of the CDF and D0 data can be obtained provided a significant non-perturbative contribution is included. We also present predictions for the LHC.

Vector boson transverse momentum distributionsat the Tevatron

We show vector boson transverse momentum distributions at the Tevatronobtained by running the HERWIGMonte Carlo event generator with matrix-element corrections.We compare our results with some recent D0 and CDF data.

InclusiveJ/ψandψ(2S)production fromBdecay inpp¯collisions

Using information on B-meson fragmentation functions from CERN LEP 1 and adopting the nonrelativistic QCD factorization formalism proposed by Bodwin, Braaten, and Lepage, we predict the transverse-momentum distribution of J/psi mesons originating from the inclusive decays of b hadrons produced in p p-bar collisions at the Fermilab Tevatron. We determine the relevant colour-octet charmonium matrix elements from fits to CDF data on prompt charmonium hadroproduction and to CLEO data on charmonium production from B-meson decay. Our predictions are found to agree well with recent CDF and D0 data.

Activation barriers for oxygen diffusion in polystyrene and polycarbonate glasses: effects of codissolved argon, helium, and nitrogen

A recently developed spectroscopic technique was used to determine oxygen diffusion coefficients as a function of temperature for polystyrene and polycarbonate films. Data were recorded at total pressures <300 Torr over the temperature range 5–45 °C under conditions in which argon, helium, and nitrogen, respectively, were copenetrants. In all cases, the presence of the additional gas caused an increase in the oxygen diffusion coefficient. Arrhenius plots of the data yield (a) a diffusion activation barrier, Eact, and (b) a diffusion coefficient, D0, that represents the condition of "barrier-free" gas transport for the temperature domain over which the Arrhenius plot is linear. For all cases examined in both polystyrene and polycarbonate, D0 increased with an increase in the partial pressure of added gas. In polystyrene, the presence of an additional gas did not change Eact. In polycarbonate, Eact obtained in the presence of helium and argon likewise did not differ from that obtained in the absence of the copenetrant. When nitrogen was the added gas, however, a larger value of Eact was obtained. This latter observation is interpreted to reflect the plasticization of polycarbonate by nitrogen. Eact and D0 data are discussed within the context of a model that distinguishes between dynamic and static elements of free volume in the polymer matrix. Keywords: oxygen diffusion, polystyrene, polycarbonate, activation barrier.

Calculation of diffusion coefficients for aqueous organic species at temperatures from 0 to 350 °C

Evaluation of hydrocarbon transport through the pore spaces of saturated rock in the subsurface as a function of time and distance requires accurate values of diffusion coefficients for aqueous organic species. Analysis of aqueous tracer diffusion coefficients (D0) for normal alkanes, alcohols, amides, carboxylic acids, alkylbenzenes, and alkylnaphthalenes reported in the literature indicates that diffusional activation energies decrease with increasing temperature, reaching a constant limiting value of ~3300 cal mol−1 at temperatures a: 1̆00°C. This observation is consistent with the modified Arrhenius expression reported by Oelkers and Helgeson (1988). The Kirkwood-Riseman equation is used to predict D0 values as a function of the polymer chain length of hydrocarbons. Regression of experimental D0 data with a combined expression of the Kirkwood-Riseman and modified Arrhenius equations yields parameters which permit calculation of tracer diffusion coefficients for over 50 aqueous organic species at temperatures from 0° to 350°C and Psat. (psat refers to pressures corresponding to the liquid-vapor equilibrium curve for H2O at temperatures greater than 100°C and 1 bar at lower temperatures.) Resulting values of D0 permit evaluation of the extent of diffusional mass transfer in both contaminated near-surface environments and in the porewater adjoining oil field reservoirs. The computed tracer diffusion coefficients, which are qualitatively similar to D0 values previously calculated for aqueous ions, increase substantially with increasing temperature. For example, the tracer diffusion coefficient of aqueous toluene increases from 0.36 to 27.1 × 10−5 cm2sec−1 in response to increasing temperature from 0 to 350°C.

Neural networks for event filtering at D0

Neural networks may provide important tools for pattern recognition in high energy physics. We discuss an initial exploration of these techniques, presenting the result of network simulations of several filter algorithms. The D0 data acquisition system, a MicroVAX farm, will perform critical event selection; we describe a possible implementation of neural network algorithms in this system.

The use of neural networks in the D0 data acquisition system

The possible application of algorithms derived from neural networks to the D0 experiment is discussed. The D0 data acquisition system is based on a large farm of MicroVaxes, each independently performing real-time event filtering. Advanced multiport memories in each MicroVAX node will enable special function processors to have direct access to event data. An exploratory study of back-propagation neural networks, such as might be configured in the nodes, for more efficient event filtering is described. >

InclusiveD0andD+Production ine+e−Annihilation at 29 GeV

We have observed inclusive production of D0 and D+ mesons, and their charge conjugates, in e+e− annihilation at 29 GeV on the basis of a data sample of 106 pb−1. These signals correspond to R values of R(D0+D―0)=1.8±0.5 and R(D++D−)=1.2±0.4. Taking the D+ and D0 data together, we measure a charge asymmetry of A=−0.08±0.12 for charmed quarks. A comparison of R(D+D―) with R(D*+D―*) obtained via the process D*+→D0π+ gives a DD* ratio of 1.0−0.2+0.3, indicating that direct D* production dominates over direct D production.

CH stretching frequencies, bond lengths and dissociation energies

Correlations between CH bond stretching frequencies, bond lengths and dissociation energies, previously studied by Bernstein, are reexamined with fresh data of all kinds. The introduction of vCH values from CHD2 substitution is helpful in all cases of CH3 compounds, and vital where the latter contain non-equivalent CH bonds. Predictions of rCH0 are made for a wide range of CH3 and CH2 compounds with a likely error of less than 0·002 Å. The former include CH3NO2, CH3F, PhCH3, (CH3)4M, where MC, Sn, Ge, Sn, Pb, containing symmetrical CH3 groups, and for CH3NH2, (CH3)2NH, (CH3)2N SiF3, CH3OH, CH3OPCl2, HCOOCH3, CH3COOCH3, (CH3)2CH2, (CH3)2CO and (CH3)3CCl where non-equivalent bonds are present. Differences in bond length as small as 0·0005 Å can in principle be distinguished. The existing rCH0 value for CH3CN is seriously wrong. The correlation between vCH and JCH is considered briefly. The correlation between vCH and D0298 is good for most compounds which are likely to dissociate into σ radicals where the stabilization energy is small. In CH3 compounds containing non-equivalent bonds. D0 correlates excellently with the frequency for the weaker bond, as expected. “Radical stabilization energy” is conveniently measured using the correlation graph and vCH value, together with the observed D0. unusually large experimental errors appear to be present in D0 data for c-C3H6, c-C4H8, C2H2 and HCOOH.