arXiv subjects

R. Ammar

Publications and source records attributed to R. Ammar.

5 recordsLinked to original sources

arXiv2002

Observation of the Decay Omega_C^0 --> Omega- e+ nu_e

Using the CLEO detector at the Cornell Electron Storage Ring, we have observed the Omega_c (css ground state) in the decay Omega_c -> Omega- e+ nu. We find a signal of 11.4 +- 3.8 (stat) events. The probability that we have observed a background fluctuation is 7.6 x 10-5. We measure BF(Omega_c -> Omega- e+ nu) x sigma(e+ e- -> Omega_c X) = (42.2 +- 14.1 (stat) +- 5.7 (syst)) fb and R = Gamma(Omega_c -> Omega- pi+)/Gamma(Omega_c -> Omega- e+ nu) = 0.41 +- 0.19 (stat) +- 0.04 (syst). This is the first statistically significant observation of an individual decay mode of the Omega_c in e+ e- annhiliation, and the first example of a baryon decaying via beta-emmision, where no quarks from the first generation participate in the reaction.

hep-ex↗

arXiv2001

Search for the Familon via $B^{\pm}\to π^{\pm}X^{0}$, $B^{\pm}\to K^{\pm}X^{0}$, and $B^{0}\to K_{S}^{0} X^{0}$ Decays

We have searched for the two-body decay of the B meson to a light pseudoscalar meson $h = π^+, K^+, K^0_S$ and a massless neutral weakly-interacting particle $X^0$ such as the familon, the Nambu-Goldstone boson associated with a spontaneously broken global family symmetry. We find no significant signal by analyzing a data sample containing 9.7 million $B\bar{B}$ mesons collected with the CLEO detector at the Cornell Electron Storage Ring, and set a 90% C.L. upper limit of $4.9 \times 10^{-5}$ and $5.3 \times 10^{-5}$ on the branching fraction for the decays $B^+ \to h^+ X^0$ and $B^0 \to K^0_S X^0$, respectively. These upper limits correspond to a lower bound of about $10^{8}$ GeV on the family symmetry breaking scale involving the third generation of quarks.

hep-ex↗

arXiv2000

First Observation of the $Σ_{c}^{*+}$ Baryon and a New Measurement of the $Σ_{c}^{+}$ Mass

Using data recorded with the CLEO II and CLEO II.V detector configurations at the Cornell Electron Storage Rings, we report the first observation and mass measurement of the $Σ_c^{*+}$ charmed baryon, and an updated measurement of the mass of the $Σ_c^+$ baryon. We find $M(Σ_c^{*+})-M(Λ_c^+)$= 231.0 +- 1.1 +- 2.0 MeV, and $M(Σ_c^{+})-M(Λ_c^+)$= 166.4 +- 0.2 +- 0.3 MeV, where the errors are statistical and systematic respectively.

hep-ex↗

arXiv2000

Measurement of the product branching fraction B(c->Theta_c)*B(Theta_c->/\X)

Based on an a high statistics e+e- -> ccbar data sample, we report on the inclusive rate for charmed baryons to decay into / particles using charm-event tagging. We select e+e- -> ccbar events which have a clear anti-charm tag and measure the / content in the hemisphere opposite the tag (charge conjugate modes are implicit). This allows us to determine the product branching fraction: B(/)=B(c->Theta_c)*B(Theta_c->/\X), where Theta_c represents a sum over all charmed baryons produced in e+e- fragmentation at sqrt(s)=10.5 GeV, given our specific tags. We obtain B(/)=(1.87+/-0.03+/-0.33)%

hep-ex↗

arXiv1998

A Limit on the Mass of the $ν_τ$

A limit on the mass of the tau neutrino is derived from 4.5 million tau pairs produced in an integrated luminosity of 5.0 fb^{-1} of electron-positron annihilation to tau pairs at center of mass energies near 10.6 GeV. The measurement technique involves a two-dimensional extended likelihood analysis, including the dependence of the end-point population on the neutrino mass, and allows for the first time an explicit background contribution. We use the decays of the tau to five charged pions and a neutrino as well as the decay to three charged pions, two neutral pions and a neutrino to obtain an upper limit of 30 MeV/c^2 at 95% C.L.

hep-ex↗