952 research outputs found
The gluon content of the and mesons and the , electromagnetic transition form factors
We compute power-suppressed corrections to the \eta\gamma and
\eta^{\prime}\gamma transition form factors
Q^2F_{\eta(\eta^{\prime})\gamma}(Q^2) arising from the end point regions x \to
0,1 by employing the infrared-renormalon approach. The contribution to the form
factors from the quark and gluon content of the \eta,\eta^{\prime} mesons is
taken into account using for the \eta-\eta^{\prime} mixing the SU_f(3) singlet
\eta_1 and octet \eta_8 basis. The theoretical predictions obtained this way
are compared with the corresponding CLEO data and restrictions on the input
parameters (Gegenbauer coefficients) B_2^q(\eta_1), B_2^g(\eta_1), and
B_2^q(\eta_8) in the distribution amplitudes for the \eta_1,\eta_8 states with
one nonasymptotic term are deduced. Comparison is made with the results from
QCD perturbation theory.Comment: 25 pages, RevTeX4 used. 9 figures as EPS files. Text significantly
changed to include variation of theoretical parameters. Figures modified.
Corrected typo in equation (34) and trivial mistake in -coefficient.
References added. Conclusions unchange
Results of Radiation Tests of the Anode Front-End Boards for the CMS Endcap Muon Cathode Strip Chambers
Recommended from our members
Performance of the E715 Transition Radiation Detector
The transition radiation detector (TRD) consisted of 12 identical modules, each containing a radiator and a multiwire proportional counter (MWPC). A TRD is found to be an effective device for the identification of electrons in a large hadron background at Tevatron energies. The TRD proved to be a stable and reliable device with performance parameters in close agreement with theoretical predictions. The combination of a TRD with a lead glass calorimeter proved to be a very powerful method of electron identification. (LEW
First observation of a narrow charm-strange meson DsJ(2632) -> Ds eta and D0 K+
We report the first observation of a charm-strange meson DsJ(2632) at a mass
of 2632.6+/-1.6 MeV/c^2 in data from SELEX, the charm hadro-production
experiment E781 at Fermilab. This state is seen in two decay modes, Ds eta and
D0 K+. In the Ds eta decay mode we observe an excess of 49.3 events with a
significance of 7.2sigma at a mass of 2635.9+/-2.9 MeV/c^2. There is a
corresponding peak of 14 events with a significance of 5.3sigma at 2631.5+/-1.9
MeV/c^2 in the decay mode D0 K+. The decay width of this state is <17 MeV/c^2
at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(Dseta)
is 0.16+/-0.06. The mechanism which keeps this state narrow is unclear. Its
decay pattern is also unusual, being dominated by the Ds eta decay mode.Comment: 5 pages, 3 included eps figures. v2 as accepted for publication by
PR
First Observation of the Doubly Charmed Baryon Xi_cc^+
We observe a signal for the doubly charmed baryon Xi_cc^+ in the charged
decay mode Xi_cc^+ --> Lambda_c^+ K- pi+ in data from SELEX, the charm
hadro-production experiment at Fermilab. We observe an excess of 15.9 events
over an expected background of 6.1 +/- 0.5 events, a statistical significance
of 6.3sigma. The observed mass of this state is (3519 +/- 1) MeV/c^2. The
Gaussian mass width of this state is 3MeV/c^2, consistent with resolution; its
lifetime is less than 33fsec at 90% confidence.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
Observation of the Cabibbo-suppressed decay Xi_c+ -> p K- pi+
We report the first observation of the Cabibbo-suppressed charm baryon decay
Xi_c+ -> p K- pi+. We observe 150 +- 22 events for the signal. The data were
accumulated using the SELEX spectrometer during the 1996-1997 fixed target run
at Fermilab, chiefly from a 600 GeV/c Sigma- beam. The branching fractions of
the decay relative to the Cabibbo-favored Xi_c+ -> Sigma+ K- pi+ and Xi_c+ ->
X- pi+ pi+ are measured to be B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> Sigma+ K- pi+) =
0.22 +- 0.06 +- 0.03 and B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> X- pi+ pi+) = 0.20 +-
0.04 +- 0.02, respectively.Comment: 5 pages, RevTeX, 3 figures (postscript), Submitted to Phys. Rev. Let
- …