Inclusive jet cross sections for events with a large rapidity gap with respect to the proton direction from the reaction
ep → jet +
X with quasi-real photons have been measured with the ZEUS ...detector. The cross sections refer to jets with transverse energies
E
T
jet > 8 GeV. The data show the characteristics of a diffractive process mediated by pomeron exchange. Assuming that the events are due to the exchange of a pomeron with partonic structure, the quark and gluon content of the pomeron is probed at a scale ∼ (
E
T
jet)
2. A comparison of the measurements with model predictions based on QCD plus Regge phenomenology requires a contribution of partons with a hard momentum density in the pomeron. A combined analysis of the jet cross sections and recent ZEUS measurements of the diffractive structure function in deep inelastic scattering gives the first experimental evidence for the gluon content of the pomeron in diffractive hard scattering processes. The data indicate that between 30% and 80% of the momentum of the pomeron carried by partons is due to hard gluons.
Spin precession of channeled particles in bent crystals has been observed for the first time. Polarized Sigmasup + were channeled using bent Si crystals. These crystals provided an effective magnetic ...field of 45 T which resulted in a measured spin precession of 60plus minus17degree. This agrees with the prediction of 62plus minus2degree using the world average of Sigmasup + magnetic moment measurements. This new technique gives a Sigmasup + magnetic moment of (2.40plus minus0.46plus minus0.40)musub ital N, where the quoted uncertainties are statistical and systematic, respectively. We see no evidence of depolarization in the channeling process.
The production of Ds− relative to Ds+ as a function of xF with 600 GeV/c Σ− beam is measured in the interval 0.15<xF<0.7 by the SELEX (E781) experiment at Fermilab. The integrated charge asymmetries ...with 600 GeV/c Σ− beam (0.53±0.06) and π− beam (0.06±0.11) are also compared. The results show the Σ− beam fragments play a role in the production of Ds−, as suggested by the leading quark model.
We report the first observation of a charm-strange meson D(+)(sJ)(2632) at a mass of 2632.5+/-1.7 MeV/c(2) in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is ...seen in two decay modes, D(+)(s)eta and D0K+. In the D(+)(s)eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c(2). There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c(2) in the decay mode D0K+. The decay width of this state is <17 MeV/c(2) at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(D(+)(s)eta) is 0.14+/-0.06. The mechanism that keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the D(+)(s)eta decay mode.
Measurement of the Ds± lifetime Iori, M; Alkhazov, G; Atamantchouk, A.G ...
Physics letters. B,
12/2001, Letnik:
523, Številka:
1-2
Journal Article
Recenzirano
We report a precise measurement of the D±s meson lifetime. The data were taken by the SELEX experiment (E781) spectrometer using 600 GeV/cΣ−, π− and p beams. The measurement has been done using 918 ...reconstructed D±s. The lifetime of the D±s is measured to be 472.5±17.2±6.6 fs, using K∗(892)0K± and φπ± decay modes. The lifetime ratio of Ds± to D0 is 1.145±0.049.
CP Violation in τ Decays McCliment, Edward R.; Teeters, William D.
Physical review. D, Particles and fields,
01/1972, Letnik:
5, Številka:
3
Journal Article
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