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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 613 records · Page 34
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DOE OSTI2010

Implications of the Dimuon CP Asymmetry in B{sub d,s} Decays

The D0 Collaboration reported a 3.2{sigma} deviation from the standard model (SM) prediction in the like-sign dimuon asymmetry. Assuming that new physics contributes only to B{sub d,s} mixing, we show that the data can be analyzed without using the theoretical calculation of {Delta}{Gamma}{sub s}, allowing for robust interpretations. We find that this framework gives a good fit to all measurements, including the recent CDF Collaboration S{sub {psi}{phi}} result. The data allow universal new physics with similar contributions relative to the SM in the B{sub d} and B{sub s} systems, but favors a larger deviation in B{sub s} than in B{sub d} mixing. The general minimal flavor violation framework with flavor diagonal CP violating phases can account for the former case and remarkably even for the latter case. This observation makes it simpler to speculate about which extensions with general flavor structure may also fit the data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Search for R-Parity Violating Decays of Sneutrinos to e{mu}, {mu}{tau}, and e{tau} Pairs in pp Collisions at {radical}(s)=1.96 TeV

We present a search for supersymmetric neutrino {nu}-tilde production using the Tevatron pp collision data collected with the CDF II detector and corresponding to an integrated luminosity of 1 fb{sup -1}. We focus on the scenarios predicted by the R-parity violating (RPV) supersymmetric models in which sneutrinos decay to two charged leptons of different flavor. With the data consistent with the standard model expectations, we set upper limits on {sigma}(pp{yields}{nu}-tilde)xBR({nu}-tilde{yields}e{mu},{mu}{tau},e{tau}) and use these results to constrain the RPV couplings as a function of the sneutrino mass.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Improved Search for a Higgs Boson Produced in Association with Z{yields}l{sup +}l{sup -} in pp Collisions at {radical}(s)=1.96 TeV

We search for the standard model Higgs boson produced with a Z boson in 4.1 fb{sup -1} of integrated luminosity collected with the CDF II detector at the Tevatron. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electrons or muons, we set 95% credibility level upper limits on the ZH production cross section multiplied by the H{yields}bb branching ratio. Improved analysis methods enhance signal sensitivity by 20% relative to previous searches. At a Higgs boson mass of 115 GeV/c{sup 2} we set a limit of 5.9 times the standard model cross section.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Top Quark Mass Measurement in the lepton+jets Channel Using a Matrix Element Method and in situ Jet Energy Calibration

A precision measurement of the top quark mass m{sub t} is obtained using a sample of tt events from pp collisions at the Fermilab Tevatron with the CDF II detector. Selected events require an electron or muon, large missing transverse energy, and exactly four high-energy jets, at least one of which is tagged as coming from a b quark. A likelihood is calculated using a matrix element method with quasi-Monte Carlo integration taking into account finite detector resolution and jet mass effects. The event likelihood is a function of m{sub t} and a parameter {Delta}{sub JES} used to calibrate the jet energy scale in situ. Using a total of 1087 events in 5.6 fb{sup -1} of integrated luminosity, a value of m{sub t}=173.0{+-}1.2 GeV/c{sup 2} is measured.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Reconciling J/{psi} Production at HERA, RHIC, Tevatron, and LHC with Nonrelativistic QCD Factorization at Next-to-Leading Order

We calculate the cross section of inclusive direct J/{psi} hadroproduction at next-to-leading order within the factorization formalism of nonrelativistic quantum chromodynamics, including the full relativistic corrections due to the intermediate {sup 1}S{sub 0}{sup [8]}, {sup 3}S{sub 1}{sup [8]}, and {sup 3}P{sub J}{sup [8]} color-octet states. We perform a combined fit of the color-octet long-distance matrix elements to the transverse-momentum (p{sub T}) distributions measured by CDF at the Fermilab Tevatron and H1 at DESY HERA and demonstrate that they also successfully describe the p{sub T} distributions from PHENIX at BNL RHIC and CMS at the CERN LHC as well as the photon-proton c.m. energy and (with worse agreement) the inelasticity distributions from H1. This provides a first rigorous test of nonrelativistic QCD factorization at next-to-leading order. In all experiments, the color-octet processes are shown to be indispensable.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

J/{psi}({psi}{sup '}) Production at the Tevatron and LHC at O({alpha}{sub s}{sup 4}v{sup 4}) in Nonrelativistic QCD

We present a complete evaluation for J/{psi}({psi}{sup '}) prompt production at the Tevatron and LHC at next-to-leading order in nonrelativistic QCD, including color-singlet, color-octet, and higher charmonia feeddown contributions. The short-distance coefficients of {sup 3}P{sub J}{sup [8]} at next-to-leading order are found to be larger than leading order by more than an order of magnitude but with a minus sign at high transverse momentum p{sub T}. Two new linear combinations of color-octet matrix elements are obtained from the CDF data, and used to predict J/{psi} production at the LHC, which agrees with the CMS data. The possibility of {sup 1}S{sub 0}{sup [8]} dominance and the J/{psi} polarization puzzle are also discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Measurement of b Hadron Lifetimes in Exclusive Decays Containing a J/{psi} in pp Collisions at {radical}(s)=1.96 TeV

We report on a measurement of b-hadron lifetimes in the fully reconstructed decay modes B{sup +}{yields}J/{psi}K{sup +}, B{sup 0}{yields}J/{psi}K{sup *}(892){sup 0}, B{sup 0}{yields}J/{psi}K{sub s}{sup 0}, and {Lambda}{sub b}{sup 0}{yields}J/{psi}{Lambda}{sup 0} using data corresponding to an integrated luminosity of 4.3 fb{sup -1}, collected by the CDF II detector at the Fermilab Tevatron. The measured lifetimes are {tau}(B{sup +})=[1.639{+-}0.009(stat){+-}0.009(syst)] ps, {tau}(B{sup 0})=[1.507{+-}0.010(stat){+-}0.008(syst)] ps, and {tau}({Lambda}{sub b}{sup 0})=[1.537{+-}0.045(stat){+-}0.014(syst)] ps. The lifetime ratios are {tau}(B{sup +})/{tau}(B{sup 0})=[1.088{+-}0.009(stat){+-}0.004(syst)] and {tau}({Lambda}{sub b}{sup 0})/{tau}(B{sup 0})=[1.020{+-}0.030(stat){+-}0.008(syst)]. These are the most precise determinations of these quantities from a single experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Measurement of the Mass Difference between t and t Quarks

We present a direct measurement of the mass difference between t and t quarks using tt candidate events in the lepton+jets channel, collected with the CDF II detector at Fermilab's 1.96 TeV Tevatron pp Collider. We make an event by event estimate of the mass difference to construct templates for top quark pair signal events and background events. The resulting mass difference distribution of data is compared to templates of signals and background using a maximum likelihood fit. From a sample corresponding to an integrated luminosity of 5.6 fb{sup -1}, we measure a mass difference, {Delta}M{sub top}=M{sub t}-M{sub t}=-3.3{+-}1.4(stat){+-}1.0(syst) GeV/c{sup 2}, approximately 2 standard deviations away from the CPT hypothesis of zero mass difference.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

First Search for Multijet Resonances in $\sqrt{s} = 1.96$ TeV $ p\bar{p}$ Collisions

We present the first model independent search for three-jet hadronic resonances within multijet events in $\sqrt{s} = 1.96$ TeV $ p\bar{p}$ collisions at the Fermilab Tevatron using the CDF II detector. Pair production of supersymmetric gluinos and squarks with hadronic R-parity violating decays is employed as an example of a new physics benchmark for this signature. Selection criteria based on the kinetmatic properties of an ensemble of jet combinations within each event help to extract signal from copious QCD background. Our background estimates include all-hadronic t{anti t} decays that have a signature similar to the signal. No significant excess outside the top quark mass window is observed in data with an integrated luminosity of 3.2 fb{sup -1}. We place 95% confidence level limits on the production cross section {sigma}(p{anti p} {yields} X X') x BR ((tilde gg) {yields} 3 jet + 3 jet) where X, X' = {tilde g}, {tilde q}, or {tilde {anti q}}, with {tilde q}, {tilde {anti q}} {yields} {tilde g} + jet, as a function of gluino mass, in the range of 77 GeV/c{sup 2} to 240 GeV/c{sup 2}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for new T' particles in final states with large jet multiplicities and missing transverse energy in pp collisions at √s=1.96 TeV

We present a search for a new particle T decaying to a top quark via T = t + X, where X goes undetected. We use a data sample corresponding to 5.7 fb -1 of integrated luminosity of pp collisions with √s = 1.96 TeV, collected at Fermilab Tevatron by the CDF II detector. Our search for pair production of T' is focused on the hadronic decay channel, pp = TT= tt+XX=bqqbqq + XX. We interpret our results in terms of a model where T is an exotic fourth generation quark and X is a dark matter particle. The data are consistent with standard model expectations. We set a limit on the generic production of TT = tt =+ XX, excluding the fourth generation exotic quarks T at 95% confidence level up to m T = 400 GeV/c 2 for m X ≤ 70 GeV/c 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Observation of the Baryonic Flavor-Changing Neutral Current Decay Λ b 0 → Λµ + µ -

The authors report the first observation of the baryonic flavor-changing neutral current decay Λ b 0 → Λµ + µ - with 24 signal events and a statistical significance of 5.8 Gaussian standard deviations. This measurement uses a pp¯ collisions data sample corresponding to 6.8 fb -1 at √s = 1.96 TeV collected by the CDF II detector at the Tevatron collider. The total and differential branching ratios for Λ b 0 → Λµ + µ - are measured. They find Β(Λ b 0 → Λµ + µ - ) = [1.73 ± 0.42(stat) ± 0.55(syst)] x 10 -6 . They also report the first measurement of the differential branching ratio of B s 0 →φµ + µ - using 49 signal events. In addition, they report branching ratios for B + →K + µ + µ - , B 0 →K 0 µ + µ - and Β→ K*(892)µ + µ - decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for a Heavy Toplike Quark in pp Collisions at {radical}(s)=1.96 TeV

We present the results of a search for pair production of a heavy toplike (t') quark decaying to Wq final states using data corresponding to an integrated luminosity of 5.6 fb{sup -1} collected by the CDF II detector in pp collisions at {radical}(s)=1.96 TeV. We perform parallel searches for t'{yields}Wb and t'{yields}Wq (where q is a generic down-type quark) in events containing a lepton and four or more jets. By performing a fit to the two-dimensional distribution of total transverse energy versus reconstructed t{sup '} quark mass, we set upper limits on the t't' production cross section and exclude a standard model fourth-generation t' quark decaying to Wb (Wq) with mass below 358 (340) GeV/c{sup 2} at 95% C.L.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Measurements of the Angular Distributions of Muons from Υ Decays in pp̄ Collisions at √s=1.96 TeV

The angular distributions of muons from Υ(1S,2S,3S)→μ⁺μ⁻ decays are measured using data from pp̄ collisions at √s=1.96 TeV corresponding to an integrated luminosity of 6.7 fb⁻¹ and collected with the CDF II detector at the Fermilab Tevatron. This analysis is the first to report the full angular distributions as functions of transverse momentum p T for Υ mesons in both the Collins-Soper and s-channel helicity frames. This is also the first measurement of the spin alignment of Υ(3S) mesons. Within the kinematic range of Υ rapidity |y|<0.6 and p T up to 40 GeV/c, the angular distributions are found to be nearly isotropic.

Aaltonen, T.↗
DOE OSTI2012

Search for Dark Matter in Events with One Jet and Missing Transverse Energy in pp̄ Collisions at √s=1.96 TeV

We present the results of a search for dark matter production in the monojet signature. We analyze a sample of Tevatron pp̄ collisions at √s=1.96 TeV corresponding to an integrated luminosity of 6.7 fb⁻¹ recorded by the CDF II detector. In events with large missing transverse energy and one energetic jet, we find good agreement between the standard model prediction and the observed data. We set 90% confidence level upper limits on the dark matter production rate. The limits are translated into bounds on nucleon-dark matter scattering rates which are competitive with current direct detection bounds on spin-independent interaction below a dark matter candidate mass of 5 GeV/c², and on spin-dependent interactions up to masses of 200 GeV/c².

Aaltonen, T.↗