L. Stanco

A measurement of e+e− → pp for (1975 ⩽ s ⩽ 2250) MeV

The e+e− → pp cross section has been measured in the energy interval (1975 ⩽ 2E ⩽ 2250) MeV for |cosθ| < 0.7. The measurement is based on ∼ 100 events, thus improving by a factor 3 on the previous existing statistics in this energy interval. The form factor |G|2 is given as a function of energy under the assumption |GE| = |GM|. We also give the first measurement of the differential cross section, averaged over the energy interval, and estimate the ratio GM|/|GE| from it.

>A Measurement of

The e+e− → pp cross section has been measured in the energy interval (1975 ⩽ 2E ⩽ 2250) MeV for |cosθ| < 0.7. The measurement is based on ∼ 100 events, thus improving by a factor 3 on the previous existing statistics in this energy interval. The form factor |G|2 is given as a function of energy under the assumption |GE| = |GM|. We also give the first measurement of the differential cross section, averaged over the energy interval, and estimate the ratio GM|/|GE| from it.

e^+ e^- \to \bar{p} p

Abstract The e+e− → π+π− cross section has been measured from about 280 events (an order of magnitude more than the previous world statistics) in the energy interval 1.35 ⩽ s ⩽ 2.4 GeV with the DM2 detector at DCI. The pion squared form factor |Fπ|2 shows a deep minimum around 1.6 GeV/c2 and is better fit under the hypothesis of two ϱ-like resonance ⋍0.25 GeV/c2 wide with 1.42 and 1.77 GeV/c2 masses.

for 1975-{MeV}

Branching ratios of {ital J}/{psi} decays into {omega}{pi}{sup 0},{omega}{eta},{omega}{eta}{prime},{rho}{eta},{rho}{eta}{prime},{phi}{eta},{phi}{eta}{prime}, and {ital K}{sup *}(892){bar K}+charge conjugate are measured from the 8.6{times}10{sup 6} {ital J}/{psi}s produced by the DM2 experiment at the Orsay {ital e}{sup +}{ital e}{sup {minus}} storage ring DCI. The {eta} and {eta}{prime} mesons are found consistent with a {ital q{bar q}} structure and a mixing angle {theta}{sub {ital P}}=({minus}19.1{plus minus}1.4){degree}.

\le \sqrt{s} \le

The Inner Tracker system of the spectrometers of the OPERA experiment makes use of Resistive Plate Chambers (RPC) in a large-scale application. We present here the definition of the project and the full design of the Inner Tracker. Specific performances for the OPERA-RPC in the spectrometer are also reported. Particle detection, muon identification and trigger capability are discussed, in particular. Some results from test beam (T9 and T7 lines at the CERN PS) and measurements from laboratory test (CERN, Frascati, Padova, Gran Sasso) with prototype detectors are discussed, as well as specific solutions developed for the final set-up in OPERA. Full Monte Carlo simulations of the experimental set-up have been also developed.

2250-{MeV}

OPERA is part of the CNGS project and it is an experiment dedicated to the observation of long-baseline numu into nutau oscillations through tau appearance. Resistive Plate Chambers (RPCs) with bakelite electrodes are used to instrument the 2 cm gaps between the magnetized iron slabs of the two spectrometers. The RPC installation ended in may 2004 on the first spectrometer and in march 2005 on the second one. Before the installation, every RPC is subjected to a complete test chain in order to reject the poorer quality detectors. The tests are performed in dedicated facilities to ensure the proper RPC gluing, to measure its electrical properties and to verify the response to cosmic rays and the intrinsic noise levels. We have also tested the long term stability of real size OPERA RPC prototypes operated at cosmic ray fluxes for more than one year. On small size prototypes we are performing studies on the gas mixtures in order to reduce the total charge released in the gas for each detector count. The validation of the installed RPCs has been performed with pure nitrogen. A small part of them has been also tested with the gas mixture Ar/C2H2F4/i-C4H10 /SF6=75.4/20/4/0.6

The Pion Electromagnetic Form-factor in the Timelike Energy Range 1.35-{GeV}

Abstract The J /Ψ→Λ Λ → p π − p π + decay is used to test the CP invariance in the Λ hyperon decays by measuring A=(α Λ +α Λ )/(α Λ −α Λ ) where α Λ (α Λ ) is the decay asymmetry parameter asymmetry parameter of the Λ( Λ ) . The obtained value A=0.01±0.10 is in agreement with CP invariance. The used formalism would permit to check quantum mechanics, assuming CP invariance.

\le \sqrt{s} \le

The OPERA spectrometer is built from two large dipoles instrumented with around 1000 Resistive Plate Chambers (RPCs), covering a surface of about 3350 m2, and digitally read out by means of almost 27000 strips. The huge number of channels, the inaccessibility of many parts of the detector and the wide uncertainty about the signal amplitude pushed to study a low cost, high sensitivity discriminator, and a very carefully designed layout for the read out system. Here we will present a novel application of LVDS line receiver as discriminator, showing that it exceeds the requirements of a large RPC based detector and offers the intrinsic advantages of a mature technology in terms of costs, reliability and integration scale. We will also present the layout of the read out system showing as the sensitivity and the noise immunity were preserved in a system where the front end electronics is far away from the detector.

2.4-{GeV}

Neutrino physics is nowadays receiving more and more attention as a possible source of information for the long standing problem of new Physics beyond the Standard Model. The recent measurements of the third mixing angle

J/ psi -->vector+pseudoscalar decays and the quark content of eta and eta '

\theta_{13}