L. E. Price

The Atmospheric Neutrino Flavor Ratio from a 3.9 Fiducial Kiloton-Year Exposure of Soudan 2

Abstract We report a measurement of the atmospheric neutrino flavor ratio, R, using a sample of quasi-elastic neutrino interactions occurring in an iron medium. The flavor ratio (tracks/showers) of atmospheric neutrinos in a 3.9 fiducial kiloton-year exposure of Soudan 2 is 0.64±0.11(stat.)±0.06(syst.) of that expected. Important aspects of our main analysis have been checked by carrying out two independent, alternative analyses; one is based upon automated scanning, the other uses a multivariate approach for background subtraction. Similar results are found by all three approaches.

Measurement of the atmospheric neutrino flavour composition in Soudan 2

Abstract The atmospheric neutrino flavour ratio measured using a 1.52 kton-year exposure of Soudan 2 is found to be 0.72 ± 0.19−0.07+0.05 relative to the expected value from a Monte Carlo calculation. The possible background of interactions of neutrons and photons produced in muon interactions in the rock surrounding the detector has been investigated and is shown not to produce low values of the ratio.

Rapidity Dependence of the Charged Particle Multiplicity Distributions in e+ e- Annihilation at 29-GeV

Abstract The charged particle multiplicity distribution for e+e− annihilations at s = 29 GeV has been measured using the High Resolution Spectrometer at PEP. The multiplicity distribution, expressed as a function of the mean, shows KNO scaling when compared to e+e− data at other energies. Multiplicity distributions for particles selected in different central rapidity spans are presented. All of these are well presented by the Negative binomial distribution. As the rapidity span is narrowed, the distributions become broader and approach a constant value of the parameter k.

Study of cosmic ray composition in the knee region using multiple muon events in the Soudan 2 detector

Deep underground muon events recorded by the Soudan 2 detector, located at a depth of 2100 m of water equivalent, have been used to infer the nuclear composition of cosmic rays in the ``knee`` region of the cosmic ray energy spectrum. The observed muon multiplicity distribution favors a composition model with a substantial proton content in the energy region 8{times}10{sup 5}{endash}1.3{times}10{sup 7} GeV/nucleus. {copyright} {ital 1997} {ital The American Physical Society}

The SOUDAN 2 detector: The design and construction of the tracking calorimeter modules

SOUDAN 2 is a 960-ton tracking calorimeter which has been constructed to search for nucleon decay and other phenomena. The full detector consists of 224 calorimeter modules each weighing 4.3 tons. The design and construction of the modules are described. The modules consist of finely segmented iron instrumented with 1 m long drift tubes of 15 mm internal diameter. The tubes enable three spatial coordinates and dE/dx to be recorded for charged particles traversing the tubes.

Measurement of the lifetime of hadrons containing the b-quark

Data collected with the High Resolution Spectrometer at PEP, corresponding to an integrated luminosity of 200 pb- 1 ofe+e annihilation at 29 GeV, were used to measure the mean hfetlme of hadrons containing the bottom quark. The hfetlme was determined using the impact parameter method on events containing a high-transverse-momentum electron The result, based on a sample of 301 events, is vB = 102~039042 ps, where the Indicated errors include both statistics and systematlcs In the context of the standard model, the lifetime of hadrons containing a bottom quark is determined by the electroweak coupling between the b and the c and u quarks. In the Kobayashi-Maskaw a scheme, the lifetime constrains the values of the matrix elements [ Vbc [ and ] Vbu [ [ 11. This letter presents a measurement of the lifetime of a mixture of hadrons containing the b-quark. The data sample consists of e+e---}bb annihilations at x/~=29 GeV, tagged by a high-PT electron coming from the semileptonic decay of the b-quark. Two different analysis techniques are used, but the quoted result is based on a maximum likelihood fit to the measured impact parameter distribution. A detailed description of the High Resolution Spectrometer can be found elsewhere [2]. For this analysis, the tracking system is essential. It consists

New results from Bhabha scattering at 29 GeV

New results are given on Bhabha scattering at the center-of-mass energy of 29 GeV, based on a sample having an integrated luminosity of 165 pb/sup -1/ observed in the High Resolution Spectrometer (HRS) at the PEP colliding beam facility. The measured differential cross sections are used to evaluate Standard Model parameters, lower bound limts on QED cutoff parameters, and lower bound limits on composite model parameters. 10 refs., 1 fig., 3 tabs.

The observation of underground muons from the direction of Cygnus X-3 during the January 1991 radio flare

Abstract Muons recorded in the Soudan 2 underground nucleon decay detector from January 1989 to February 1991 have been examined for any correlation with the radio flares of Cygnus X-3 observed during this period. On two nearby days during the radio flare of January 1991 a total of 32 muons within 2.0° of the Cygnus X-3 direction were observed when 11.4 were expected.

Observation of a shadow of the Moon in the underground muon flux in the Soudan 2 detector

A shadow of the moon, with a statistical significance of 5 sigma, has been observed in the underground muon flux at a depth of 2090 mwe using the Soudan 2 detector. The angular resolution of the detector is well described by a Gaussian with a sigma of less than 0.3 degrees. The position of the shadow confirms that the alignment of the detector is known to better than 0.15 degrees and has remained stable during ten years of data taking.

Search for nucleon decay with final states [formula presented] and [formula presented] using Soudan 2

We have searched for nucleon decay into five two-body final states using a 4.4 kiloton-year fiducial exposure of the Soudan 2 iron tracking calorimeter. For proton decay into the fully visible final states mu+ eta and e+ eta, we observe zero and one event, respectively, that satisfy our search criteria for nucleon decay. The lifetime lower limits (tau/B) thus implied are 89 x 10^30 years and 81 x 10^30 years at 90% confidence level. For neutron decay into nubar eta, we obtain the lifetime lower limit 71 x 10^30 years. Limits are also reported for neutron decay into nubar pi0, and for proton decay into nubar pi+.