Search for pair-produced long-lived neutral particles decaying to jets in the ATLAS hadronic calorimeter in ppcollisions at √s=8TeV

The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3fb−1of data collected in proton–proton collisions at √s=8TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeVto 900 GeV, and a long-lived neutral particle mass from 10 GeVto 150 GeV

Measurement of the reaction gamma*p->phi p in deep, inelastic e(+)p scattering at HERA

The production of phi mesons in the reaction e(+)p --> e(+)phi p (phi --> K+K-), for 7 phi p cross section rises strongly with W. This behaviour is similar to that previously found for the gamma*p --> rho(0)p cross section. This strong dependence cannot be explained by production through soft pomeron exchange, It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small x. The ratio of sigma(phi)/sigma(rho(0)), which has previously been determined by ZEUS to be 0.065 +/- 0.013 (stat.) in photoproduction at a mean W of 70 GeV, is measured to be 0.18 +/- 0.05 (stat.) +/- 0.03 (syst.) at a mean Q(2) of 12.3 GeV2 and mean W of approximate to 100 GeV and is thus approaching at large Q(2) the value of 2/9 predicted from the quark charges of the vector mesons and a flavour independent production mechanism

EXPERIMENTAL-STUDY OF JET MASSES IN E+E- ANNIHILATION AT CM ENERGIES BETWEEN 12-GEV AND 43.5-GEV

Data on jet masses, resulting from the decomposition of e+e- hadronic final states into two hemispheres, are presented at centre of mass energies between 12 and 43.5 GeV. Comparisons are made with bare O(αs2) QCD predictions as well as with QCD based fragmentation models. Values for αs and {Mathematical expression} are determined, both with and without hadronization effects included. Upper and lower limits for {Mathematical expression} independent of fragmentation models have been determined to be 0.480±0.025 GeV and 0.047±0.007 GeV respectively. © 1989 Springer-Verlag

COMPARISON OF INCLUSIVE FRACTIONAL MOMENTUM DISTRIBUTIONS OF QUARK AND GLUON JETS PRODUCED IN E+E- ANNIHILATION

Inclusive charged particle production in e+e- annihilation into hadrons is studied in terms of the particle fractional momentum xp. The xp distribution for gluon jets is extracted by comparing two data samples measured in the TASSO detector: nearly symmetric three jet events at centre-of-mass energy W∼35 GeV and two jet events at W∼22 GeV, yielding quark and gluon jets of similar energies (∼11.5 GeV). No significant difference is observed between quark and gluon jets. Monte Carlo models based on parton showers describe the trend and energy variation of the data better than a model with second order matrix element in αs. © 1989 Springer-Verlag

A measurement of the Ds lifetime

The lifetime of the Ds meson has been measured using the TASSO detector at PETRA and found to be (5.7-2.6+3.6±0.9)×10-13 s. The method used was to reconstruct fully the decay vertex of the channel Ds→φ{symbol}π±, φ{symbol}→K+K-. © 1987 Springer-Verlag

A MEASUREMENT OF THE TAU-LIFETIME

We have reconstructed 695 three-track τ decay vertices using a high resolution drift chamber close to the interaction point. From the distribution of decay lengths we measure the lifetime to be (3.06 ±0.20±0.14)×10-13 s. Using this result we find that the ratio of charged weak coupling constant for the τ to that of the μ, G τ/G μ=0.967±0.040 consistent with the concept of lepton universality. © 1988 Springer-Verlag