T. Buran

ATLAS search for new phenomena in dijet mass and angular distributions using pp collisions at √s = 7 TeV

A bstractMass and angular distributions of dijets produced in LHC proton-proton collisions at a centre-of-mass energy

Search for resonances decaying into top-quark pairs using fully hadronic decays in pp collisions with ATLAS at √s = 7 TeV

\sqrt{s}=7

The inclusive single-particle spectra of π−, KS0 and Λ in proton-proton collisions at 19 GeV/c

TeV have been studied with the ATLAS detector using the full 2011 data set with an integrated luminosity of 4.8 fb−1. Dijet masses up to ~ 4.0 TeV have been probed. No resonance-like features have been observed in the dijet mass spectrum, and all angular distributions are consistent with the predictions of QCD. Exclusion limits on six hypotheses of new phenomena have been set at 95% CL in terms of mass or energy scale, as appropriate. These hypotheses include excited quarks below 2.83 TeV, colour octet scalars below 1.86 TeV, heavy W bosons below 1.68 TeV, string resonances below 3.61 TeV, quantum black holes with six extra space-time dimensions for quantum gravity scales below 4.11 TeV, and quark contact interactions below a compositeness scale of 7.6 TeV in a destructive interference scenario.

Search for the 1P1 charmonium state in pp annihilations at the CERN intersecting storage rings

A bstractA search for resonances produced in 7 TeV proton-proton collisions and decaying into top-quark pairs is described. In this Letter events where the top-quark decay produces two massive jets with large transverse momenta recorded with the ATLAS detector at the Large Hadron Collider are considered. Two techniques that rely on jet substructure are used to separate top-quark jets from those arising from light quarks and gluons. In addition, each massive jet is required to have evidence of an associated bottom-quark decay. The data are consistent with the Standard Model, and limits can be set on the production cross section times branching fraction of a Z′ boson and a Kaluza-Klein gluon resonance. These limits exclude, at the 95% credibility level, Z′ bosons with masses 0.70-1.00 TeV as well as 1.28-1.32 TeV and Kaluza-Klein gluons with masses 0.70-1.62 TeV.

The four-prong annihilation of 1.2 GeV/c antiprotons in hydrogen (II) π+π+π−π−π0 final state

Abstract Data on the inclusive production spectra of K S 0 and Λ from proton-proton collisions at 19 GeV are presented and discussed in connection with the earlier studied inclusive π − production spectrum. The three single-particle spectra are compared with a crude two-center thermal model for the average radiation from the pp collisions.

Direct observation and partial-width measurement of γγ decay of charmonium states

Abstract This experiment has been performed at the CERN Intersecting Storage Rings to study the direct formation of charmonium states in antiproton-proton annihilations. The experimental program has partly been devoted to an inclusive scan for p p → J /ψ + X in the range 3520–3530 MeV/c2. A cluster of five events has been observed in a narrow energy band, centred on the centre of gravity of the 3PJ states where the 1P1 is expected to be. When interpreted as a new resonace, these data yield a mass m = 3525.4±0.8 MeV/c2.

J/Ψ resonant formation and mass measurement in antiproton-proton annihilations

Abstract Approximately 17 000 four-prong annihilations of 1.2 GeV/ c antiprotons in hydrogen have been analyzed. The present report considers those events with one neutral pion (5π). The 5π events show production of ϱ 0 , ϱ ± , f 0 , ω 0 , η 0 mesons, and the possibility of a ϱϱ enhancement at 1400 MeV/ c and/or a ϱπ enhancement at 1080 MeV/ c is considered. The influence of the Bose-Einstein correlation function of Goldhaber et al. [6] is investigated. Centre-of-mass angular distributions of the pions and centre-of-mass opening angles between pairs of pions are presented. The production upper limits at the 95% confidence level, for several resonant states are given.

Formation of the χ1 and χ2 charmonium resonances in antiproton-proton annihilation and measurements of their masses and total widths

As part of the charmonium formation experiment at the CERN Intersecting Storage Rings, we studied the reaction pp→cc→γγ in an antiproton momentum scan through the ηc, χ1, and χ2 regions. We report events observed in the ηc and χ2 regions, whilst no event was observed in the χ1 region, as expected for a spin-1 state.

Search for direct chargino production in anomaly-mediated supersymmetry breaking models based on a disappearing-track signature in pp collisions at root s=7 TeV with the ATLAS detector

Abstract Experiment R704, the last to be performed at the CERN-ISR, has successfully applied a new method to study ( c c ) states formed directly in antiproton-proton annihilations. The novelty of the method rests on the capability to build a highly performing annihilation source by letting a cold

Upper limits of the proton magnetic form factor in the time-like region from p̄p→ e+e- at the CERN-ISR

In an experiment performed at the CERN-ISR the direct formation is observed of the χ1 and χ2 charmonium states in proton-antiproton annihiliation. A novel technique provided excellent energy resolution together with small background and reduced systematics. The following values for the masses and total widths of the states were obtained: Λχ1 <3 MeV (95% CL); mχ1 = (3511.3±0.4±0.4) MeV; Λχ2=(2.6 +1.4−1.0) MeV; mξ2=(3556.9±0.4±0.5) MeV. First measurements of the partial widths to antiproton-proton are also reported: Λ(χ1→pp)=57+13-11±11) and Λ(χ2→pp)=(233 +51-45±48) eV.