This paper gives a detailed description of an experiment which studies the interactions of muon-type neutrinos in hydrogen and deuterium. The experiment was performed at the Zero Gradient Synchrotron using the wide-band neutrino beam incident on the Argonne 12-foot bubble chamber filled with hydrogen and deuterium. The neutrino energy spectrum peaks at 0.5 GeV and has a tail extending to 6 GeV. The shape and intensity of the flux is determined using measurements of pion yields from beryllium. The produced pions are focused by one or (for the latter part of the experiment) two magnetic horns. A total of 364000 pictures were taken with a hydrogen filling of the bubble chamber and 903 000 with a deuterium filling. The scanning and other analyses of the events are described. The most abundant reaction occurs off neutrons and is quasi-elastic scattering νd→μ−pps. The separation of these events from background channels is discussed. The total and differential cross sections are analyzed to obtain the axial-vector form factor of the nucleon. Our result, expressed in terms of a dipole form factor, gives an axial-vector mass of 0.95±0.09 GeV. A comparison is made to previous measurements using neutrino beams, and also to determinations based upon threshold pion electroproduction experiments. In addition, the data are used to measure the weak vector form factor and so check the conserved-vector-current hypothesis.
Measured Quasi-Elastic total cross section.
A 12 event/μb bubble chamber experiment on K − p interactions at 3.95 GeV/ c yielded 1212 events including systems with strangeness S = −2. Results concerning cascade resonances with masses less than 2000 MeV are reported; in particular a determination of the mass and width of the Ξ o 1530 and an interpretation of the mass region (1700–/) 2000) MeV.
No description provided.
Interactions of 683-MeV/c negative pions with protons were investigated using the BNL 14-in. hydrogen bubble chamber in a 17-kG field. Two thousand elastic scatterings were analyzed, yielding a cross section of 18.9±1.0 mb. No evidence for powers of cosθ higher than the second was observed in the elastic angular distribution. The angular distribution obtained was dσdω=(0.384±0.026)+(1.70±0.06)cosθ+(3.36±0.11)cos2θ mb/sr. The single-pion production reactions π−+p→π−+π0+p and π−+p→π−+π++n were studied in detail. A total of 441 π0 productions and 833 π+ productions were analyzed giving cross sections of 3.99±0.50 and 7.50±0.80 mb, respectively. The differential distributions for these inelastic processes are presented and compared with the predictions of the model of Olsson and Yodh. The distribution of events on the Dalitz plots for π0 production is accounted for by the model. However, for the π+ reaction, the model (so far developed) does not describe adequately the distribution of events on the Dalitz plot. In particular, the model fails to account for the enhancement at high (π+π−) effective masses in ππ mass distribution. The center-of-mass angular distributions for π0 and π+ production reactions are presented and compared with the model.
No description provided.
No description provided.
No description provided.
Electroweak symmetry breaking explains the origin of the masses of elementary particles through their interactions with the Higgs field. Besides the measurements of the Higgs boson properties, the study of the scattering of massive vector bosons with spin one allows the nature of electroweak symmetry breaking to be probed. Among all processes related to vector-boson scattering, the electroweak production of two jets and a $Z$-boson pair is a rare and important one. Here we report the observation of this process from proton-proton collision data corresponding to an integrated luminosity of 139/fb recorded at a centre-of-mass energy of 13 TeV with the ATLAS detector at the Large Hadron Collider. We consider two different final states originating from the decays of the $Z$-boson pair - one containing four charged leptons and the other containing two charged leptons and two neutrinos. The hypothesis of no electroweak production is rejected with a statistical significance of 5.7 $\sigma$, and the measured cross-section for electroweak production is consistent with the standard model prediction. In addition, we report cross-sections for inclusive production of a $Z$-boson pair and two jets for the two final states.
Signal strength and significance of EW ZZjj processes
Signal strength and significance of EW ZZjj processes
Measured and predicted fiducial cross-sections in both the lllljj and ll$\nu\nu$jj channels for the inclusive ZZjj processes. Uncertainties due to different sources are presented
Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. In this Letter, results are presented of a search for such particles, which decay at a significant distance from their production point, using a final state containing charged hadrons and an associated muon. This analysis uses a data sample of proton-proton collisions at sqrt(s)= 7 TeV corresponding to an integrated luminosity of 4.4 fb-1 collected in 2011 by the ATLAS detector operating at the Large Hadron Collider. Results are interpreted in the context of R-parity violating supersymmetric scenarios. No events in the signal region are observed and limits are set on the production cross section for supersymmetric particles, multiplied by the square of the branching ratio for a neutralino to decay to charged hadrons and a muon, as a function of the neutralino lifetime. To allow these limits to be used in a variety of models, they are presented for a range of squark and neutralino masses.
Efficiency-vs-radial-vertex-position without re-tracking The efficiency for reconstructing a displaced vertex passing all cuts, as a function of radial distance from the z-axis to the vertex positon. The retrack and noretrack suffixes refer to whether or not the procedure known as re-tracking, where the tracking algorithm is re-run with looser cuts, on the leftover hits from standard tracking, was used to select the tracks that were input to the vertexing algorithm.
Efficiency-vs-radial-vertex-position with re-tracking The efficiency for reconstructing a displaced vertex passing all cuts, as a function of radial distance from the z-axis to the vertex positon. The retrack and noretrack suffixes refer to whether or not the procedure known as re-tracking, where the tracking algorithm is re-run with looser cuts, on the leftover hits from standard tracking, was used to select the tracks that were input to the vertexing algorithm.
Event selection efficiency vs mean proper decay length The MH, HH, ML suffix used for overlaying the graphs refers to the combinations of squark and neutralino masses in the signal MC sample: MH is 700GeV squarks and 494GeV neutralinos, HH is 1.5TeV squarks and 494GeV neutralinos, and ML is 700GeV squarks and 108GeV neutralinos. The tables show the efficiency for reconstructing a signal event, where at least one vertex candidate passes all selection requirements, as a function of the proper decay length c*tau of the neutralino.
Using 1.8 fb-1 of pp collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the Large Hadron Collider, we present measurements of the production cross sections of Upsilon(1S,2S,3S) mesons. Upsilon mesons are reconstructed using the di-muon decay mode. Total production cross sections for p_T<70 GeV and in the rapidity interval |Upsilon|<2.25 are measured to be 8.01+-0.02+-0.36+-0.31 nb, 2.05+-0.01+-0.12+-0.08 nb, 0.92+-0.01+-0.07+-0.04 nb respectively, with uncertainties separated into statistical, systematic, and luminosity measurement effects. In addition, differential cross section times di-muon branching fractions for Upsilon(1S), Upsilon(2S), and Upsilon(3S) as a function of Upsilon transverse momentum p_T and rapidity are presented. These cross sections are obtained assuming unpolarized production. If the production polarization is fully transverse or longitudinal with no azimuthal dependence in the helicity frame the cross section may vary by approximately +-20%. If a non-trivial azimuthal dependence is considered, integrated cross sections may be significantly enhanced by a factor of two or more. We compare our results to several theoretical models of Upsilon meson production, finding that none provide an accurate description of our data over the full range of Upsilon transverse momenta accessible with this dataset.
Corrected cross-section measurements in the isotopic spin-alignment scenario. The second (sys) error is the uncertainty in the luminosity.
Fiducial Upsilon(1S) production cross-section, where pT>4 GeV and |eta|<2.3 for both muons, as a function of Upsilon(1S) pT in the Upsilon(1S) rapidity (|y|) bins 0-1.2 and 1.2-2.25. The first uncertainty is statistical, the second is systematic.
Fiducial Upsilon(2S) production cross-section, where pT>4 GeV and |eta|<2.3 for both muons, as a function of Upsilon(2S) pT in the Upsilon(2S) rapidity (|y|) bins 0-1.2 and 1.2-2.25. The first uncertainty is statistical, the second is systematic.
This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark (\={t}) in the emu continuum using 2.1/fb of data collected by the ATLAS detector in sqrt(s) = 7 TeV pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-violating couplings at 95% C.L. are calculated as a function of the scalar top mass (m_{\={t}}). The upper limits on the production cross section for pp->emuX, through the t-channel exchange of a scalar top quark, ranges from 170 fb for m_{\={t}}=95 GeV to 30 fb for m_{\={t}}=1000 GeV.
The observed E-MU invariant mass distribution plus SM background and signal predicitons for a n stop mass of 95 GeV.
Information about the signal samples used.
The ratios of the observed and expected upper cross section limits to the theoretical cross sections as a function of the scalar top mass.
The results of a search for supersymmetry in events with large missing transverse momentum and heavy flavour jets using an integrated luminosity corresponding to 2.05 fb^-1 of pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider are reported. No significant excess is observed with respect to the prediction for Standard Model processes. Results are interpreted in a variety of R-parity conserving models in which scalar bottoms and tops are the only scalar quarks to appear in the gluino decay cascade, and in an SO(10) model framework. Gluino masses up to 600-900 GeV are excluded, depending on the model considered.
Acceptance in the GLUINO-NEUTRALINO plane in the Gbb model for the 1 btag signal region with Meff > 500 GeV.
Acceptance in the GLUINO-NEUTRALINO plane in the Gbb model for the 2 btags signal region with Meff > 500 GeV.
Acceptance in the GLUINO-NEUTRALINO plane in the Gbb model for the 1 btag signal region with Meff > 700 GeV.
A study of WZ production in proton-proton collisions at sqrt(s) = 7 TeV is presented using data corresponding to an integrated luminosity of 4.6 fb^-1 collected with the ATLAS detector at the Large Hadron Collider in 2011. In total, 317 candidates, with a background expectation of 68+/-10 events, are observed in double-leptonic decay final states with electrons, muons and missing transverse momentum. The total cross-section is determined to be sigma_WZ(tot) = 19.0+1.4/-1.3(stat.)+/-0.9(syst.)+/-0.4(lumi.) pb, consistent with the Standard Model expectation of 17.6+1.1/-1.0 pb. Limits on anomalous triple gauge boson couplings are derived using the transverse momentum spectrum of Z bosons in the selected events. The cross section is also presented as a function of Z boson transverse momentum and diboson invariant mass.
The measured fiducial cross section.
The measured total cross section.
Normalised fiducial cross section in bins of the PT of the Z0.
This paper presents a search for a new heavy particle produced in association with a top or antitop quark. Two models in which the new heavy particle is a color singlet or a color triplet are considered, decaying respectively to tbarq or tq, leading to a resonance within the ttbar + jets signature. The full 2011 ATLAS pp collision dataset from the LHC (4.7 fb-1) is used to search for ttbar events produced in association with jets, in which one of the W bosons from the top quarks decays leptonically and the other decays hadronically. The data are consistent with the Standard Model expectation, and a new particle with mass below 430 GeV for both W boson and color triplet models is excluded at 95% confidence level, assuming unit right-handed coupling.
Upper limits of the cross sections and couling (g_R) in the WPRIME colour singlet model.
Upper limits of the cross sections and couling (g_R) in the PHI colour triplet model.
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