A combined analysis technique for the search for fast magnetic monopoles with the MACRO detector

We describe a search method for fast moving ($\beta > 5 \times 10^{-3}$) magnetic monopoles using simultaneously the scintillator, streamer tube and track-etch subdetectors of the MACRO apparatus. The first two subdetectors are used primarily for the identification of candidates while the track-etch one is used as the final tool for their rejection or confirmation. Using this technique, a first sample of more than two years of data has been analyzed without any evidence of a magnetic monopole. We set a 90% CL upper limit to the local monopole flux of $1.5 \times 10^{-15} cm^{-2} s^{-1} sr^{-1}$ in the velocity range $5 \times 10^{-3} \le \beta \le 0.99$ and for nucleon decay catalysis cross section smaller than $\sim 1 mb$.Comment: 29 pages (12 figures). Accepted by Astroparticle Physic

Muon Energy Estimate Through Multiple Scattering with the Macro Detector

Muon energy measurement represents an important issue for any experiment addressing neutrino induced upgoing muon studies. Since the neutrino oscillation probability depends on the neutrino energy, a measurement of the muon energy adds an important piece of information concerning the neutrino system. We show in this paper how the MACRO limited streamer tube system can be operated in drift mode by using the TDC's included in the QTPs, an electronics designed for magnetic monopole search. An improvement of the space resolution is obtained, through an analysis of the multiple scattering of muon tracks as they pass through our detector. This information can be used further to obtain an estimate of the energy of muons crossing the detector. Here we present the results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines, to provide a full check of the electronics and to exploit the feasibility of such a multiple scattering analysis. We show that by using a neural network approach, we are able to reconstruct the muon energy for $E_\mu<$40 GeV. The test beam data provide an absolute energy calibration, which allows us to apply this method to MACRO data.Comment: 25 pages, 11 figures, Submitted to Nucl. Instr. & Meth.

Neutrino astronomy with the MACRO detector

High energy gamma ray astronomy is now a well established field and several sources have been discovered in the region from a few GeV up to several TeV. If sources involving hadronic processes exist, the production of photons would be accompanied by neutrinos too. Other possible neutrino sources could be related to the annihilation of WIMPs at the center of galaxies with black holes. We present the results of a search for point-like sources using 1100 upward-going muons produced by neutrino interactions in the rock below and inside the MACRO detector in the underground Gran Sasso Laboratory. These data show no evidence for a possible neutrino point-like source or for possible correlations between gamma ray bursts and neutrinos. They have been used to set flux upper limits for candidate point-like sources which are in the range 10^-14-10^-15 cm-2 s-1.Comment: 37 pages, 15 figures, replacement due to a typo in tab. 6, AASLaTex, submitted to Ap

Search for Nucleon Decays induced by GUT Magnetic Monopoles with the MACRO Experiment

The interaction of a Grand Unification Magnetic Monopole with a nucleon can lead to a barion-number violating process in which the nucleon decays into a lepton and one or more mesons (catalysis of nucleon decay). In this paper we report an experimental study of the effects of a catalysis process in the MACRO detector. Using a dedicated analysis we obtain new magnetic monopole (MM) flux upper limits at the level of $\sim 3\cdot 10^{-16} cm^{-2} s^{-1} sr^{-1}$ for $1.1\cdot 10^{-4} \le |\beta| \le 5\cdot 10^{-3}$, based on the search for catalysis events in the MACRO data. We also analyze the dependence of the MM flux limit on the catalysis cross section.Comment: 12 pages, Latex, 10 figures and 2 Table

Search for massive rare particles with MACRO

Massive rare particles have been searched for in the penetrating cosmic radiation using the MACRO apparatus at the Gran Sasso National Laboratories. Liquid scintillators, streamer tubes and nuclear track detectors have been used to search for magnetic monopoles (MMs). Based on no observation of such signals, stringent flux limits are established for MMs as slow as a few 10^(-5)c. The methods based on the scintillator and on the nuclear track subdetectors were also applied to search for nuclearites. Preliminary results of the searches for charged Q-balls are also presented.Comment: 20 pages, 9 EPS figures included with epsfi

Final results of magnetic monopole searches with the MACRO experiment

We present the final results obtained by the MACRO experiment in the search for GUT magnetic monopoles in the penetrating cosmic radiation, for the range $4\times 10^{-5}< \beta < 1$. Several searches with all the MACRO sub-detectors (i.e. scintillation counters, limited streamer tubes and nuclear track detectors) were performed, both in stand alone and combined ways. No candidates were detected and a 90% Confidence Level (C.L.) upper limit to the local magnetic monopole flux was set at the level of $1.4\times 10^{-16}$ cm$^{-2}$ s$^{-1}$ sr$^{-1}$. This result is the first experimental limit obtained in direct searches which is well below the Parker bound in the whole $\beta$ range in which GUT magnetic monopoles are expected.Comment: 12 pages, Latex, 9 figures and 2 Table

Measurement of the residual energy of muons in the Gran Sasso underground Laboratories

The MACRO detector was located in the Hall B of the Gran Sasso underground Laboratories under an average rock overburden of 3700 hg/cm^2. A transition radiation detector composed of three identical modules, covering a total horizontal area of 36 m^2, was installed inside the empty upper part of the detector in order to measure the residual energy of muons. This paper presents the measurement of the residual energy of single and double muons crossing the apparatus. Our data show that double muons are more energetic than single ones. This measurement is performed over a standard rock depth range from 3000 to 6500 hg/cm^2.Comment: 28 pages, 9 figure

The Observation of Up-going Charged Particles Produced by High Energy Muons in Underground Detectors

An experimental study of the production of up-going charged particles in inelastic interactions of down-going underground muons is reported, using data obtained from the MACRO detector at the Gran Sasso Laboratory. In a sample of 12.2 10^6 single muons, corresponding to a detector livetime of 1.55 y, 243 events are observed having an up-going particle associated with a down-going muon. These events are analysed to determine the range and emission angle distributions of the up-going particle, corrected for detection and reconstruction efficiency. Measurements of the muon neutrino flux by underground detectors are often based on the observation of through-going and stopping muons produced in $\nu_\mu$ interactions in the rock below the detector. Up-going particles produced by an undetected down-going muon are a potential background source in these measurements. The implications of this background for neutrino studies using MACRO are discussed.Comment: 18 pages, 9 figures. Accepted by Astrop. Physic

The primary cosmic ray composition between 10**15 and 10**16 eV from Extensive Air Showers electromagnetic and TeV muon data

The cosmic ray primary composition in the energy range between 10**15 and 10**16 eV, i.e., around the "knee" of the primary spectrum, has been studied through the combined measurements of the EAS-TOP air shower array (2005 m a.s.l., 10**5 m**2 collecting area) and the MACRO underground detector (963 m a.s.l., 3100 m w.e. of minimum rock overburden, 920 m**2 effective area) at the National Gran Sasso Laboratories. The used observables are the air shower size (Ne) measured by EAS-TOP and the muon number (Nmu) recorded by MACRO. The two detectors are separated on average by 1200 m of rock, and located at a respective zenith angle of about 30 degrees. The energy threshold at the surface for muons reaching the MACRO depth is approximately 1.3 TeV. Such muons are produced in the early stages of the shower development and in a kinematic region quite different from the one relevant for the usual Nmu-Ne studies. The measurement leads to a primary composition becoming heavier at the knee of the primary spectrum, the knee itself resulting from the steepening of the spectrum of a primary light component (p, He). The result confirms the ones reported from the observation of the low energy muons at the surface (typically in the GeV energy range), showing that the conclusions do not depend on the production region kinematics. Thus, the hadronic interaction model used (CORSIKA/QGSJET) provides consistent composition results from data related to secondaries produced in a rapidity region exceeding the central one. Such an evolution of the composition in the knee region supports the "standard" galactic acceleration/propagation models that imply rigidity dependent breaks of the different components, and therefore breaks occurring at lower energies in the spectra of the light nuclei.Comment: Submitted to Astroparticle Physic

Low energy atmospheric muon neutrinos in MACRO

We present the measurement of two event samples induced by atmospheric $\nu_\mu$ of average energy $\bar {E}_\nu \sim 4 GeV$. In the first sample, the neutrino interacts inside the MACRO detector producing an upward-going muon leaving the apparatus. The ratio of the number of observed to expected events is $0.57 \pm0.05_{stat} \pm0.06_{syst} \pm0.14_{theor}$ with an angular distribution similar to that expected from the Bartol atmospheric neutrino flux. The second is a mixed sample of internally produced downward-going muons and externally produced upward-going muons stopping inside the detector. These two subsamples are selected by topological criteria; the lack of timing information makes it impossible to distinguish stopping from downgoing muons. The ratio of the number of observed to expected events is $0.71 \pm 0.05_{stat} \pm0.07_{syst} \pm0.18_{theor}$ . Using the ratio of the two subsamples (for which most theoretical uncertainties cancel) we can test the pathlength dependence of the oscillation hypothesis. The probability of agreement with the no-oscillation hypothesis is 5% . The deviations of our observations from the expectations has a preferred interpretation in terms of $\nu_\mu$ oscillations with maximal mixing and $\Delta m^2 \sim 10^{-3} \div 10^{-2} eV^2$. These parameters are in agreement with our results from upward throughgoing muons, induced by $\nu_\mu$ of much higher energies.Comment: 7 pages, 6 figures. Submitted to Phys. Lett.