Results are presented on measured asymmetry parameter in the cross sections of the deuteron photodesintegration by linearly polarized photon beam in the energy range 40-70 MeV for the proton emission angles of 75 and 90 deg in the c. m. s. The experimental data are compared with the theoretical calculations by Partovi, Arenhovel, as well as with calculations performed within an invariant approach with gauge-invariant amplitudes in the pole approximation. The results of the calculation by Arenhovel and the present calculations satisfactorily agree with the experimental data, while the Partovi theory does not describe the asymmetry parameter measurements for photon energies above 40 MeV
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THE ASYMMETRY SIGMA HAS BEEN DETERMINED BY THE FORMULA: D(SIG)/D(OMEGA)=D(SIG0)/D(OMEGA)*(1+P*SIGMA*COS(PHI)), WHERE D(SIG0)/D(OMEGA) - CROSS SECTION ON U NPOLARIZED PHOTON BEAM, P - BEAM POLARIZATION, PHI - ASIMUTHAL ANGLE BETWEEN POLARIZATION VECTOR OF BEAM AND THE PLANE OF THE REACTION.
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A search for pair-produced third generation scalar leptoquarks is presented, using proton-proton collisions at $\sqrt{s}$= 7 TeV at the LHC. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 4.7 fb$^{-1}$. Each leptoquark is assumed to decay to a tau lepton and a b-quark with a branching fraction equal to 100%. No statistically significant excess above the Standard Model expectation is observed. Third generation leptoquarks are therefore excluded at 95% confidence level for masses less than 534 GeV.
The expected and observed 95% credibility upper limits on the cross-section of third generation leptoquark pair-production for the electron channel assuming a branching fraction LQ->tau b of 1.0, as a function of leptoquark mass. The 1(2) sigma errors on the expected limit represent all sources of systematic and statistical uncertainty. The expected NLO production cross-section for third generation scalar leptoquarks and its corresponding theoretical uncertainty is also included.
The expected and observed 95% credibility upper limits on the cross-section of third generation leptoquark pair-production for the muon channel assuming a branching fraction LQ->tau b of 1.0, as a function of leptoquark mass. The 1(2) sigma errors on the expected limit represent all sources of systematic and statistical uncertainty. The expected NLO production cross-section for third generation scalar leptoquarks and its corresponding theoretical uncertainty is also included.
The expected and observed 95% credibility upper limits on the cross-section of third generation leptoquark pair-production for the combined assuming a branching fraction LQ->tau b of 1.0, as a function of leptoquark mass. The 1(2) sigma errors on the expected limit represent all sources of systematic and statistical uncertainty. The expected NLO production cross-section for third generation scalar leptoquarks and its corresponding theoretical uncertainty is also included.
A search has been performed for the experimental signature of an isolated photon with high transverse momentum, at least one jet identified as originating from a bottom quark, and high missing transverse momentum. Such a final state may originate from supersymmetric models with gauge-mediated supersymmetry breaking in events in which one of a pair of higgsino-like neutralinos decays into a photon and a gravitino while the other decays into a Higgs boson and a gravitino. The search is performed using the full dataset of 7 TeV proton-proton collisions recorded with the ATLAS detector at the LHC in 2011, corresponding to an integrated luminosity of 4.7 fb-1. A total of 7 candidate events are observed while 7.5 pm 2.2 events are expected from the Standard Model background. The results of the search are interpreted in the context of general gauge mediation to exclude certain regions of a benchmark plane for higgsino-like neutralino production.
Missing ET distribution.
Signal Point Information: (1) Number of Monte Carlo events generated (2) Total signal cross section (pb) (3) Signal acceptance (4) Relative uncertainty on acceptance (5) CLs expected (6) CLs observed.
The observed limit contour in the GLUINO-NEUTRALINO plane.
A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton, with zero or one additional light lepton (e/mu), has been performed using 4.7 fb-1 of proton-proton collision data at sqrt(s) = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed and a 95% confidence level visible cross-section upper limit for new phenomena is set. In the framework of gauge-mediated SUSY-breaking models, lower limits on the mass scale Lambda are set at 54 TeV in the regions where the stau is the next-to-lightest SUSY particle (tan(beta) > 20). These limits provide the most stringent tests to date of GMSB models in a large part of the parameter space considered.
The observed number of signal events as a function of Lambda and Tan(Beta).
The Acceptance, Efficiency and Acceptance x Efficiency for the single tau channel as a function of Lambda and Tan(Beta).
The Acceptance, Efficiency and Acceptance x Efficiency for the two tau channel as a function of Lambda and Tan(Beta).
A search for new phenomena in final states with four or more leptons (electrons or muons) is presented. The analysis is based on 4.7 fb^-1 of sqrt(s) = 7 TeV proton-proton collisions delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in two signal regions: one that requires moderate values of missing transverse momentum and another that requires large effective mass. The results are interpreted in a simplified model of R-parity-violating supersymmetry in which a 95% CL exclusion region is set for charged wino masses up to 540 GeV. In an R-parity-violating MSUGRA/CMSSM model, values of m_1/2 up to 820 GeV are excluded for 10<tan(beta)<40.
The transverse momentum distribution of the leading lepton for events with at least 4 leptons and no Z-boson candidate.
The transverse momentum distribution of the sub-leading lepton for events with at least 4 leptons and no Z-boson candidate.
The transverse momentum distribution of the 3rd-leading lepton for events with at least 4 leptons and no Z-boson candidate.
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.
A search for diphoton events with large missing transverse momentum has been performed using proton-proton collision data at sqrt(s) = 7 TeV recorded with the ATLAS detector, corresponding to an integrated luminosity of 4.8 fb^-1. No excess of events was observed above the Standard Model prediction and model-dependent 95% confidence level exclusion limits are set. In the context of a generalised model of gauge-mediated supersymmetry breaking with a bino-like lightest neutralino of mass above 50 GeV, gluinos (squarks) below 1.07 TeV (0.87 TeV) are excluded, while a breaking scale Lambda below 196 TeV is excluded for a minimal model of gauge-mediated supersymmetry breaking. For a specific model with one universal extra dimension, compactification scales 1/R < 1.40 TeV are excluded. These limits provide the most stringent tests of these models to date.
Observeded limit on gluino mass as function of LSP mass for the GGM model.
Limit on squark mass as function of LSP mass for the GGM model.
Cross section limit for the SPS8 model.
A search is presented for the pair production of light scalar top quarks in sqrt(s) = 7 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. This analysis uses the full data sample collected during 2011 that corresponds to a total integrated luminosity of 4.7 fb-1. Light scalar top quarks are searched for in events with two opposite-sign leptons (e, mu), large missing transverse momentum and at least one jet in the final state. No excess over Standard Model expectations is found, and the results are interpreted under the assumption that the light scalar top decays to a b-quark in addition to an on-shell chargino whose decay occurs through a virtual W boson. If the chargino mass is 106 GeV, light scalar top quark masses up to 130 GeV are excluded for neutralino masses below 70 GeV.
Distribution of the PT of the leading electron for E-E events in the Signal Region, before the application of the leading lepton PT cut.
Distribution of the PT of the leading muon for MU-MU events in the Signal Region, before the application of the leading lepton PT cut.
Distribution of the PT of the leading electron for E-MU events in the Signal Region, before the application of the leading lepton PT cut.
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