Search for WW and WZ production in lepton plus jets final state at CDF

We present a search for WW and WZ production in final states that contain a charged lepton (electron or muon) and at least two jets, produced in sqrt(s) = 1.96 TeV ppbar collisions at the Fermilab Tevatron, using data corresponding to 1.2 fb-1 of integrated luminosity collected with the CDF II detector. Diboson production in this decay channel has yet to be observed at hadron colliders due to the large single W plus jets background. An artificial neural network has been developed to increase signal sensitivity, as compared with an event selection based on conventional cuts. We set a 95% confidence level upper limit of sigma_{WW}* BR(W->lnu,W->jets)+ sigma_{WZ}*BR(W->lnu,Z->jets)We present a search for WW and WZ production in final states that contain a charged lepton (electron or muon) and at least two jets, produced in √s=1.96  TeV pp̅ collisions at the Fermilab Tevatron, using data corresponding to 1.2  fb-1 of integrated luminosity collected with the CDF II detector. Diboson production in this decay channel has yet to be observed at hadron colliders due to the large single W plus jets background. An artificial neural network has been developed to increase signal sensitivity, as compared with an event selection based on conventional cuts. We set a 95% confidence level upper limit of σWW×BR(W→ℓνℓ,W→jets)+σWZ×BR(W→ℓνℓ,Z→jets)<2.88  pb, which is consistent with the standard model next-to-leading-order cross section calculation for this decay channel of 2.09±0.12  pb.Peer reviewe

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Searching the inclusive l γe T+b-quark signature for radiative top quark decay and non-standard-model processes

We compare the inclusive production of events containing a lepton (á), a photon (γ), significant transverse momentum imbalance (E T), and a jet identified as containing a b-quark, to SM predictions. The search uses data produced in proton-antiproton collisions at s=1.96TeV corresponding to 1.9fb-1 of integrated luminosity taken with the CDF detector. We find 28 áγbET events versus an expectation of 31.0-3.5+4.1 events. If we further require events to contain at least three jets and large total transverse energy, the largest SM source is radiative top-quark pair production, tt̄+γ. In the data we observe 16 tt̄γ candidate events versus an expectation from SM sources of 11.2-2.1+2.3. Assuming the difference between the observed number and the predicted non-top-quark total of 6.8-2.0+2.2 is due to SM top-quark production, we estimate the tt̄γ cross section to be 0.15±0.08pb. © 2009 The American Physical Society

Study of DsJ(*) + mesons decaying to D∗ +KS0 and D*0K+ final states

A search is performed for D sJ (*) + mesons in the reactions pp → D ∗ + K S 0 X and pp → D *0 K + X using data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb detector. For the D ∗ + K S 0 final state, the decays D *+ → D 0 π + with D 0 → K − π + and D 0 → K − π + π + π − are used. For D *0 K +, the decay D *0 → D 0 π 0 with D 0 → K − π + is used. A prominent D s1(2536)+ signal is observed in both D ∗ + K S 0 and D *0 K + final states. The resonances D s1 * (2700)+ and D s3 * (2860)+ are also observed, yielding information on their properties, including spin-parity assignments. The decay D s2 * (2573)+ → D ∗ + K S 0 is observed for the first time, at a significance of 6.9 σ, and its branching fraction relative to the D s2 * (2573)+ → D + K S 0 decay mode is measured

Observations of Lambda(0)(b) -&gt; Lambda K+pi(-) and Lambda(0)(b) -&gt; Lambda K+K- decays and searches for other Lambda(0)(b) and Xi(0)(b) decays to Lambda h(+)h '(-) final states

See paper for full list of authors - All figures and tables, along with any supplementary material and additional information, are available at this https URLInternational audienceA search is performed for the charmless three-body decays of the Λ0b and Ξ0b baryons to the final states Λh+h′−, where h(′)=π or K. The analysis is based on a data sample, corresponding to an integrated luminosity of 3fb−1 of pp collisions, collected by the LHCb experiment. The Λ0b→ΛK+π− and Λ0b→ΛK+K− decays are observed for the first time and their branching fractions and CP asymmetry parameters are measured. Evidence is seen for the Λ0b→Λπ+π− decay and limits are set on the branching fractions of Ξ0b baryon decays to the Λh+h′− final states

Search for Violations of Lorentz Invariance and CPT Symmetry in B-(s)(0) Mixing

Violations of CPT symmetry and Lorentz invariance are searched for by studying interference effects in B^{0} mixing and in B_{s}^{0} mixing. Samples of B^{0}→J/ψK_{S}^{0} and B_{s}^{0}→J/ψK^{+}K^{-} decays are recorded by the LHCb detector in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3  fb^{-1}. No periodic variations of the particle-antiparticle mass differences are found, consistent with Lorentz invariance and CPT symmetry. Results are expressed in terms of the standard model extension parameter Δa_{μ} with precisions of O(10^{-15}) and O(10^{-14})  GeV for the B^{0} and B_{s}^{0} systems, respectively. With no assumption on Lorentz (non)invariance, the CPT-violating parameter z in the B_{s}^{0} system is measured for the first time and found to be Re(z)=-0.022±0.033±0.005 and Im(z)=0.004±0.011±0.002, where the first uncertainties are statistical and the second systematic

Search for standard-model Z and Higgs bosons decaying into a bottom-antibottom quark pair in proton-antiproton collisions at 1.96 TeV SEARCH for STANDARD-MODEL Z and HIGGS ... T. AALTONEN et al

The Collider Detector at Fermilab collected a unique sample of jets originating from bottom-quark fragmentation ($b$-jets) by selecting online proton-antiproton ($p\bar{p}$) collisions with a vertex displaced from the $p\bar{p}$ interaction point, consistent with the decay of a bottom-quark hadron. This data set, collected at a center-of-mass energy of $\sqrt{s}=$1.96 TeV, and corresponding to an integrated luminosity of $5.4~\rm{fb}^{-1}$, is used to measure the $Z$-boson production cross section times branching ratio into $b\bar{b}$. The number of $Z\rightarrow b\bar{b}$ events is determined by fitting the dijet-mass distribution while constraining the dominant $b$-jet background, originating from QCD multijet events, with data. The result, $\sigma(p\bar{p} \rightarrow Z) \times \mathcal{B}(Z \rightarrow b\bar{b})= 1.11\pm 0.08(\text{stat}) \pm 0.14(\text{syst})~\text{nb}$, is the most precise measurement of this process, and is consistent with the standard-model prediction. The data set is also used to search for Higgs-boson production. No significant signal is expected in our data and the first upper limit on the cross section for the inclusive $p\bar p \rightarrow H\rightarrow b\bar b$ process at $\sqrt{s}=$1.96 TeV is set, corresponding to 33 times the expected standard-model cross section, or $\sigma = 40.6$ pb, at the 95\% confidence level

Search for the Exotic Meson X(5568) with the Collider Detector at Fermilab

A search for the exotic meson X(5568) decaying into the B[subscript s][superscript 0]π[superscript ±] final state is performed using data corresponding to 9.6  fb[superscript -1] from pp[over ¯] collisions at sqrt[s]=1960  GeV recorded by the Collider Detector at Fermilab. No evidence for this state is found and an upper limit of 6.7% at the 95% confidence level is set on the fraction of B[subscript s][superscript 0] produced through the X(5568)→B[subscript s][superscript 0]π[superscript ±} process