Response to electrons and pions of the calorimeter for the CHORUS experiment

We built and tested on charged particle beams the high energy-resolution calorimeter for the CHORUS experiment, which searches for nu(mu)-nu(tau) oscillations in the CERN Wide Band Neutrino Beam. This calorimeter is longitudinally divided into three sectors: one electromagnetic and two hadronic. The first two upstream sectors are made of lead and plastic scintillating fibers in the volume ratio of 4/1, and they represent the first large scale application of this technique for combined electromagnetic and hadronic calorimetry. The third sector is made of a sandwich of lead plates and scintillator strips and complements the measurement of the hadronic energy flow. In this paper, we briefly describe the calorimeter design and we show results on its response to electrons and pions, obtained from tests performed at the CERN SPS and PS. An energy resolution of sigma(E)/E=(32.3+/-2.4)%/root E(GeV)+(1.4+/-0.7)% was achieved for pions, and sigma(E)/E=(13.8+/-0.9)%/root V(GeV)+(-0.2+/-0.4)% for electrons

Leading-order QCD Analysis of Neutrino-Induced Dimuon Events

The results of a leading-order QCD analysis of neutrino-induced charm production are presented. They are based on a sample of 4111 \numu- and 871 \anumu-induced opposite-sign dimuon events with $E_{\mu 1},E_{\mu 2} > 6~{\rm GeV}$, $35 5.5\,{\rm GeV^2}$, observed in the CHARM~II detector exposed to the CERN wideband neutrino and antineutrino beams. The analysis yields the value of \linebreak the charm quark mass $m_c=1.79\pm0.38\,{\rm GeV}/c^2$ and the Cabibbo--Kobayashi--Maskawa matrix element $|V_{cd}|=0.219\pm0.016$. The strange quark content of the nucleon is found to be suppressed with respect to non-strange sea quarks by a factor $\kappa =0.39\pm0.09$

Experimental search for muonic photons

We report new limits on the production of muonic photons in the CERN neutrino beam. The results are based on the analysis of neutrino production of dimuons in the CHARM II detector. A $90\%$ CL limit on the coupling constant of muonic photons, $\alpha_{\mu} / \alpha < (1.5 \div 3.2) \times10^{-6}$ is derived for a muon neutrino mass in the range $m_{\nu_{\mu}} = (10^{-20} \div 10^5)$ eV. This improves the limit obtained from a precision measurement of the anomalous magnetic moment of the muon $(g-2)_\mu$ by a factor from 8 to 4

The CHORUS neutrino oscillation search experiment

The CHORUS experiment has successfully finished run I (320~000 recorded \numu\ CC in 94/95) and performed half of run II (225~000 \numu\ CC in 96). The analysis chain was exercised on a small data sample for the muonic \tdecay\ search using for the first time fully automatic emulsion scanning. This pilot analysis, resulting in a limit \sintth \leq 3 \cdot 10^{-2}, confirms that the CHORUS proposal sensitivity (\sintth \leq 3 \cdot 10^{-4}) is within reach in two years

The CHORUS calorimeter: test results

In the framework of the CHORUS experiment for the search of nu(mu) nu(tau) oscillations at CERN, we have built the high resolution calorimeter, intended for the measurement of the energy of hadronic showers produced in neutrino interactions. The calorimeter consists of three parts. The first two are made of lead and plastic scintillating fibers in the volume ratio 4:1, such as to achieve compensation. The third is a sandwich of lead plates and scintillator strips in the same volume ratio. The techniques used for the construction of the calorimeter are described, as well as its performance in shower and muon detection. We used electron, pion and muon beams in the energy range 2-100 GeV for this purpose

Construction and test of calorimeter modules for the CHORUS experiment

The construction of modules and the assembly of the calorimeter for CHORUS, an experiment that searches for nu(mu) nu(tau) oscillation, have been completed. Within the experiment, the calorimeter is required to measure the energy of hadronic showers produced in neutrino interactions with a resolution of similar to 30%/root E(GeV). To achieve this performance, the technique, developed in recent years, of embedding scintillating fibers of 1 mm diameter into a lead matrix has been adopted for the most upstream part of the calorimeter. A more conventional system, of alternating layers of lead and scintillator strips, was used for the rest. Details of module construction as well as results obtained when modules were exposed to electron and muon beams are presented