π-μ IDENTIFICATION AND HADRON CALORIMETER ANALYSIS OF ALEPH EXPERIMENT WITH MULTIVARIATER STATISTICS METHOD

In this paper π-μ identification of the hadron calorimeter prototype and the real hadron calorimeter with muon detector of ALEPH experiment on LEP is investigated by using discriminant analysis method of multivariate statistics.     

Search for short-lived particles below charm threshold

We have searched for the production by virtual photons of short-lived particles that exhibit muonic decay. We used Brookhaven's 10.5 GeV/c muon beam and examined the two and three-muon final states. The sample of 158 trimuon events is due almost entirely to QED tridents. The sample of 673 dimuons can be accounted for in part by asymmetric tridents and in part by the decay of π and K mesons. We obtain an upper limit for the production of other short-lived particles of the order of Bδ < 150 pb/nucleon, where B is the branching ratio for muonic decay. From the trident sample we establish that muons obey Fermi-Dirac statistics at the level of 8 standard deviations.     

PLASTEX: the palermo-leeds air shower tracking experiment

Summary An experiment is described in which air shower measurement are carried out by means of a ?track detector? placed in a test location near the center of a conventional array telescope currently in use for gamma-ray astronomy. This array, consisting of scintillators (GREX, operated at Haverah Park (U.K.) by the Department of Physics of the University of Leeds), provides, in the usual way, for each shower it selects, its own estimates of shower direction and shower particle density at the test location. Estimates of the muon density at the test location are provided by a large muon detector in operation nearby. The scintillator array triggers this muon detector and it is able to provide flexibly tailored trigger signals for the track detector. This detector named PLASTEX (acronym for Palermo Leeds Air Shower Tracking Experiment), consisting of tracking chambers above and below a thin sheet of lead, designed to provide data on charged particles incident from the air, on the stopping, scattering and multiplication of these particles in the lead sheet and on charged particles created in the lead sheet by shower photons. From these data estimates are derived of the densities and directional properties of the electrons, photons and muons striking the track detector. These results are to be compared with those given by the conventional detectors and with theoretical predictions given by simulations that are being carried out. The objective is to develop and assess optimal procedures for employing clusters of PLASTEX-type detectors as telescopes for the observation of UHE cosmic rays, including cosmic gammarays, over a very wide energy range. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.     

First measurement of W boson production in association with a single Charm quark in pp collisions at sqrt(s)=1.96 TeV

We present the first measurement of the production cross section of a W boson with a single charm quark (c) in pp collisions at sqrt(s)=1.96 TeV, using soft muon tagging of c jets. In a data sample of approximately 1.8 fb(-1), recorded with the Collider Detector at Fermilab II detector at the Fermilab Tevatron, we select events with W+1 or 2 jets. We use the charge correlation between the W and the muon from the semileptonic decay of a charm hadron to extract the Wc signal. We measure sigma Wc(PTc >20 GeV/c,|eta c|<1.5) x BR(W-->l nu)=9.8+/-3.2 pb, in agreement with theoretical expectations.     

EMMA—a new underground cosmic-ray experiment

An experiment observing underground muons originating from cosmic-ray air showers is under preparation in the Pyhäsalmi mine, Finland. The aim is to cover an area of about 200–300 m², and the detector setup is capable of measuring the muon multiplicity and their lateral distribution. The detector is placed at a depth of about 85 m (corresponding about 240 m w.e.), which gives a threshold energy of muons of about 45 GeV. The detection of the multimuon events is motivated by partly unknown composition of the primary cosmic rays in the energy region of 10¹⁵–10¹⁶ eV, i.e., the knee region. In addition, by measuring only the higher energy muons of the air shower, the lowest energy muons being filtered out by the rock overburden, the data is sensitive also to the studies of the upper parts of the air shower. The experiment will be constructed mainly using drift chambers used previously in LEP detectors at CERN, but it can also be expanded using plastic scintillator detectors. The prototype detector is expected to be running in the beginning of 2006, and the full-size detector by the end of 2007.     

Observation of doubly-charmed B decays at LEP

A search for doubly-charmed B decays with both charmed mesons reconstructed is performed, using about 3.8 million hadronic Z decays recorded with the ALEPH detector at LEP. A clear signal is observed in the channels and (where D can be either a D, a D or a D), providing the first direct evidence for doubly-charmed B decays involving no production. Evidence for associated and production in the decays is also presented and some candidates for completely reconstructed decays , and are observed. Furthermore, candidates for the two-body Cabibbo suppressed decays and are also observed. Measurements of the corresponding branching fractions are extracted. Received: 6 March 1998 / Published online: 23 June 1998     

Measurement of open beauty production at HERA in the D*μ final state

The production of beauty quarks with a and a muon in the final state has been measured with the ZEUS detector at HERA using an integrated luminosity of 114 pb^-1. Low transverse-momentum thresholds for the muon and D^* meson allow for a measurement of beauty production closer to the production threshold than previous measurements. The beauty signal was extracted using the charge correlations and angular distributions of the muon with respect to the D^* meson. Cross sections for photoproduction and deep inelastic scattering are somewhat higher than, but compatible with, next-to-leading-order QCD predictions, and compatible with other measurements.     

Single- and multi-photon production in ee collisions at $\sqrt{s}$ up to 209 GeV

Events containing only energetic photons are analysed in a sample of of data recorded from collisions at centre-of-mass energies between 189 and 209 GeV by the ALEPH detector at LEP. The and cross sections are measured and found to be in agreement with the standard model predictions. The number of light neutrino generations is determined to be . Upper limits are derived on the cross sections for photon production in the context of several supersymmetric models. Limits are also set on the parameters of models with extra spatial dimensions, with contact interactions and with excited electrons. Received: 27 May 2002 / Published online: 14 March 2003     

Parameter optimization of a stationary deepwater amplitude cerenkov muon detector

A condition that should be met in the design of both amplitude and temporal detectors for the muon track azimuth to be uniquely recovered is analytically found. An optimal algorithm for muon track reconstruction with an amplitude Cerenkov detector is elaborated. The optimization involves not only the design of the detector but also statistical methods for estimating auxiliary muon track parameters. An original procedure for computing the confidence interval of the muon track parameters is suggested. This procedure is based on the algorithm used for solving the nonlinear programming problem.     

Search for coherent charged pion production in neutrino-carbon interactions

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed, and an upper limit of is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.     

Investigating hadronic cores of exstensive air showers at the CARPET-2 array

Characteristics of the hadronic component of exstensive air shower (EAS) trunks are investigated at the CARPET-2 array of the Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences. In this work, we study showers with axes that located within its muon detector (MD). We discuss the procedure for selecting such showers in our experiment. The relationship between the number of thermal neutrons detected by heat detectors installed in the muon detector’s tunnel and the total energy of a cascade generated by hadrons in the magnetic detector’s absorbent matter is presented.     

Potential of the ATLAS detector for studying high-energy solar cosmic rays

The ATLAS detector is intended for testing the Standard Model and for seeking new physics at the Large Hadron Collider (LHC). In addition, it permits detecting cosmic-ray muons. At the same time, unusual bursts of the muon intensity that correlate with powerful solar flares were recorded and investigated earlier at the Baksan underground scintillation telescope in the period spanning 1981 and 2006 (2.5 solar cycles). The nature of these muon bursts and their relation to solar cosmic rays have so far remained not quite clear. The ATLAS detector possesses an excellent muon system that allows searches for similar muon bursts. Within the next few years, when the LHC and ATLAS should start operating, one expects an increase in the solar activity in the new 24th cycle. Owing to this, the probability of observing muon bursts may become higher.     

Energy release of inclined muon groups in the nevod water Cherenkov detector

The results of the analysis of the first experimental data on the energy release of inclined muon groups of cosmic rays in the water Cherenkov detector, obtained at the NEVOD-DECOR complex, are presented. It was found that the average specific energy release in the Cherenkov calorimeter (normalized to the muon densitymeasured by the data of the coordinate detector)weakly depends on the muon density; however, the significant dependence on the zenith angle is observed, which indicates an increase in the average muon energy in groups with an increase in the zenith angle.     

Search for R-parity violating production of single sneutrinos in ee collisions at $\sqrt{s}$ = 189-209 GeV

A search for single sneutrino production under the assumption that R-parity is violated via a single dominant coupling is presented. This search considers the process and is performed using the data collected by the ALEPH detector at centre-of-mass energies from 189 GeV up to 209 GeV corresponding to an integrated luminosity of 637.1 pb^-1. The numbers of observed candidate events are in agreement with Standard Model expectations and 95% confidence level upper limits on five of the couplings are given as a function of the assumed sneutrino mass. Received: 19 December 2001 / Published online: 26 July 2002     

K^0_S production in \tau decays

From a sample of about 160k candidates collected with the ALEPH detector at LEP between 1991 and 1995, lepton decays involving are studied. The associated production in decays is also investigated. The branching ratios are measured for the inclusive decay , where can be anything, and for the exclusive decays The decay is studied for the first time, giving a branching ratio The channels , , , , and are also investigated. In addition, mass spectra in the and final states are analysed to provide information on the intermediate states produced in the decays. Received: 6 January 1998 / Published online: 15 May 1998     

Determination of {\rm |V_{ub}|} from the measurement of the inclusive charmless semileptonic branching ratio of b hadrons

From a study of the kinematic properties of the final state produced in the semileptonic decays , the inclusive charmless semileptonic branching ratio of b hadrons is measured. With a sample of 3.6 million hadronic Z decays recorded between 1992 and 1995 with the ALEPH detector at LEP, the value is determined to be , where represents any charmless hadronic state and b is a mixture of b hadrons weighted by their production rates. This measurement yields the result where the last error comes from the conversion of the branching ratio to the CKM matrix element squared. Received: 6 May 1998 / Published online: 14 December 1998     

Study of charm production in Z decays

The production rates of , , , , , and in decays are measured using the LEP I data sample recorded by the ALEPH detector. The fractional energy spectrum of the is well described as the sum of three contributions: charm hadronisation, b hadron decays and gluon splitting into a pair of heavy quarks. The probability for a c quark to hadronise into a is found to be . The average fraction of the beam energy carried by mesons in events is measured to be The energy and the hemisphere mass imbalance distributions are simultaneously used to measure the fraction of hadronic Z decays in which a gluon splits to a pair: The ratio of the Vector/(Vector+Pseudoscalar) production rates in charmed mesons is found to be . The fractional decay width of the Z into pairs is determined from the sum of the production rates for various weakly decaying charmed states to be Received: 21 September 1999 / Published online: 8 June 2000     

Specific features of studying Forbush decreases in the muon flux

The variations in the cosmic ray (CR) muon flux during the Forbush decreases (FDs), registered by the DECOR muon detector and the URAGAN muon hodoscope during the periods of their operation from 2004 to 2006, are analyzed. The unified method for determining the parameters of variations in the CR flux during FDs has been developed, and the dependences of the FD characteristics on the rigidity of primary CRs and information about the spatial-angular dynamics of the muon flux during FDs have been obtained.     

Measurement of triple gauge-boson couplings at LEP energies up to 189 GeV

The triple gauge-boson couplings involving the W are determined using data samples collected with the ALEPH detector at mean centre-of-mass energies of 183 GeV and 189 GeV, corresponding to integrated luminosities of 57 pb and 174 pb, respectively. The couplings, , and , are measured using W-pair events, single-{\it W} production and single- production. Each coupling is measured individually with the other two couplings fixed at their standard model value. Including ALEPH results from lower energies, the 95% confidence level intervals for the deviation to the standard model are , , and . Fits are also presented where two or all three couplings are allowed to vary. In addition, W-pair events are used to set limits on the C- or P-violating couplings , , , and , where V denotes either or Z. No deviations from the standard model expectations are observed. Received: 28 February 2001 / Published online: 24 August 2001     

Uncertainties in underground muon flux calculations

Influence of various theoretical and experimental uncertainties on results of underground muon flux calculations is estimated on the basis of a semi-analytical solution of muon spectrum transport equation. Status and accuracies of theoretical formulae for muon interaction cross sections and energy loss rate are discussed. A brief review of recent improvements in theoretical treatment of muon interactions is given. A necessity of a comprehensive verification of different muon transport codes is stressed.