M. Monteno

We present a measurement of the flux of neutrino-induced upgoing muons (<Eν>∼ 100 GeV) using the MACRO detector. The ratio of the number of observed to expected events integrated over all zenith angles is 0.74 ±0.036 (stat) ±0.046 (systematic) ±0.13 (theoretical). The observed zenith distribution for −1.0≤cosθ≤−0.1 does not fit well with the no oscillation expectation, giving a maximum probability for χ2 of 0.1%. The acceptance of the detector has been extensively studied using downgoing muons, independent analyses and Monte Carlo simulations. The other systematic uncertainties cannot be the source of the discrepancies between the data and expectations. We have investigated whether the observed number of events and the shape of the zenith distribution can be explained by a neutrino oscillation hypothesis. Fitting either the flux or zenith distribution independently yields mixing parameters of sin22θ=1.0 and Δm2 of a few times 10−3 eV2. However, the observed zenith distribution does not fit well with any expectations, giving a maximum probability for χ2 of 5% for the best oscillation hypothesis, and the combined probability for the shape and number of events is 17%. We conclude that these data favor a neutrino oscillation hypothesis, but with unexplained structure in the zenith distribution not easily explained by either the statistics or systematics of the experiment.

The analysis of the data collected by the NA50 experiment in 1998, reported in this paper, extends and clarifies the pattern of the previously observed J/ψ anomalous suppression. This new measurement, besides providing a deeper understanding of the previous observations, reveals a steady significative decrease in the J/ψ production rate up to the most central Pb-Pb collisions. It clearly rules out the presently available conventional (hadronic) models of J/ψ suppression, which unanimously predict a saturation of the J/ψ rate for central Pb-Pb collisions. On the contrary and together with the sharp onset of the anomalous suppression previously reported, the new observation leads to a global production rate pattern which finds its natural explanation in the framework of the formation of a deconfined state of quarks and gluons.

The ratio of cross-sections for muon pair production through the Drell-Yan process in p − p and p − d reactions has been measured at y ≈ 0, with 450 GeVc incident protons. The asymmetry ADY = δpp − δpnδpp+δpn amounts to −0.09 ± 0.02 ± 0.025. The ratio ud of the nucleon sea structure functions derived from this measurement amounts to 0.51 ± 0.04 ± 0.05 at x = 0.18 and suggests that isospin symmetry is broken in the light quark sea of the nucleon.

We present a new measurement of J/psi production in Pb-Pb collisions at 158 GeV/nucleon, from the data sample collected in year 2000 by the NA50 Collaboration, under improved experimental conditions with respect to previous years. With the target system placed in vacuum, the setup was better adapted to study, in particular, the most peripheral nuclear collisions with unprecedented accuracy. The analysis of this data sample shows that the (J/psi)/Drell-Yan cross-sections ratio measured in the most peripheral Pb-Pb interactions is in good agreement with the nuclear absorption pattern extrapolated from the studies of proton-nucleus collisions. Furthermore, this new measurement confirms our previous observation that the (J/psi)/Drell-Yan cross-sections ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb collisions and that this ratio persistently decreases up to the most central collisions.

The propagation of the heavy quarks produced in relativistic nucleus-nucleus collisions at RHIC and LHC is studied within the framework of Langevin dynamics in the background of an expanding deconfined medium described by ideal and viscous hydrodynamics. The transport coefficients entering into the relativistic Langevin equation are evaluated by matching the hard-thermal-loop result for soft collisions with a perturbative QCD calculation for hard scatterings. The heavy-quark spectra thus obtained are employed to compute the differential cross sections, the nuclear modification factors R_AA and the elliptic flow coefficients v_2 of electrons from heavy-flavour decay.

A multi-step setup for heavy-flavor studies in high-energy nucleus-nucleus (AA) collisions—addressing within a comprehensive framework the initial $Q\overline{Q}$ production, the propagation in the hot medium until decoupling and the final hadronization and decays—is presented. The initial hard production of $Q\overline{Q}$ pairs is simulated using the POWHEG pQCD event generator, interfaced with the PYTHIA parton shower. Outcomes of the calculations are compared to experimental data in pp collisions and are used as a validated benchmark for the study of medium effects. In the AA case, the propagation of the heavy quarks in the medium is described in a framework provided by the relativistic Langevin equation. For the latter, different choices of transport coefficients are explored (either provided by a perturbative calculation or extracted from lattice-QCD simulations) and the corresponding numerical results are compared to experimental data from RHIC and the LHC. In particular, outcomes for the nuclear modification factor R AA and for the elliptic flow v 2 of D/B mesons, heavy-flavor electrons and non-prompt J/ψ's are displayed.

Recent experimental results on the ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}/{D}^{0}$ ratio in proton-proton ($pp$) collisions have revealed a significant enhancement compared to expectations based on universal fragmentation fractions/functions across different colliding systems, from ${e}^{+}{e}^{\ensuremath{-}}$ to $pp$. This unexpected enhancement has sparked speculation about the potential effects of a deconfined medium impacting hadronization, previously considered exclusive to heavy-ion collisions. In this study, we propose a novel approach that assumes the formation of a small, deconfined, and expanding fireball even in $pp$ collisions, where charm quarks can undergo rescattering and hadronization. We make use of the same in-medium hadronization mechanism developed for heavy-ion collisions, which involves local color-neutralization through recombination of charm quarks with nearby opposite color charges from the background fireball. Our model incorporates the presence of diquark excitations in the hot medium, which promotes the formation of charmed baryons. Moreover, the recombination process, involving closely aligned partons from the same fluid cell, effectively transfers the collective flow of the system to the final charmed hadrons. We show that this framework can qualitatively reproduce the observed experimental findings in heavy-flavor particle-yield ratios, ${p}_{T}$-spectra and elliptic-flow coefficients. Our results provide new, complementary supporting evidence that the collective phenomena observed in small systems naturally have the same origin as those observed in heavy-ion collisions.

The angular distribution of upward-going muons produced by atmospheric neutrinos in the rock below the MACRO detector show anomalies in good agreement with two flavor neutrino-mu ==> neutrino-tau oscillations with maximum mixing and Delta m**2 around 0.0024 eV**2. Exploiting the dependence of magnitude of the matter effect on oscillation channel, and using a set of 809 upward-going muons observed in MACRO, we show that the two flavor neutrino-mu ==> neutrino-sterile oscillation is disfavored with 99% C.L. with respect to neutrino-mu ==> neutrino-tau.

laboratory, using a large sample of data.These observations are used to compute the surface muon Qux and the primary "all-nucleon" spectrum.An analysis of systematic uncertainties introduced by the interaction models in the atmosphere and the underground propagation of muons is presented.A comparison of our results with published data is also presented.

In this paper the design, construction and performance of the lower part of the first supermodule of the MACRO detector is described.

We report on a search for a phase transition from ordinary nuclear matter to a state of deconfined quarks and gluons as predicted by lattice QCD calculations. A new measurement of charmonium production in Pb-Pb interactions at 158 GeV/c per nucleon agrees with our previous results and confirms the anomalous J/ψ suppression we had already observed on a significantly smaller data sample. New event selection and analysis techniques show that, for peripheral collisions, the J/ψ cross-section per nucleon-nucleon collision agrees with the precise suppression pattern inferred from a wide range of measurements extending from p-p up to S-U collisions. As the collisions become more central, the Pb-Pb cross-section exhibits a clear departure from this normal behaviour. The onset of the anomalous J/ψ suppression reported here is the first clear observation of a threshold effect in heavy ion collisions and can be considered as a strong indication of the production of a deconfined quark-gluon phase in central Pb-Pb collisions.

We report a new measurement of J/psi, psi' and Drell-Yan cross-sections, in the kinematical domain $-0.425<y_{\rm cm}<0.575$ and $-0.5<\cos\theta_{\rm CS}<0.5$, performed at the CERN-SPS using 400 GeV/c incident protons on Be, Al, Cu, Ag, W and Pb targets. The dependence of the charmonia production cross-sections on the size of the target nucleus allows to quantify the so-called normal nuclear absorption. In the framework of the Glauber model, this new measurement is combined with results previously obtained with the same apparatus, under different experimental conditions, and leads to a precise determination of the J/psi and psi' absorption cross-sections in the surrounding nuclear matter.

The ALICE Collaboration has measured the inclusive production of muons from heavy-flavor decays at forward rapidity, 2.5<y<4, in pp and Pb-Pb collisions at sqrt[s(NN)]=2.76 TeV. The p(t)-differential inclusive cross section of muons from heavy-flavor decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of p(t) and collision centrality. A weak suppression is measured in peripheral collisions. In the most central collisions, a suppression of a factor of about 3-4 is observed in 6<p(t)<10 GeV/c. The suppression shows no significant p(t) dependence.

We present results for the quenching, elliptic flow and azimuthal correlations of heavy-flavor particles in high-energy nucleus-nucleus collisions obtained through the POWLANG transport setup, developed in the past to study the propagation of heavy quarks in the Quark–Gluon Plasma and here extended to include a modeling of their hadronization in the presence of a medium. Hadronization is described as occurring via the fragmentation of strings with endpoints given by the heavy (anti-) quark $$Q(\overline{Q})$$ and a thermal parton $$\overline{q}(q)$$ from the medium. The flow of the light quarks is shown to affect significantly the $$R_\mathrm{AA}$$ and $$v_2$$ of the final $$D$$ mesons, leading to a better agreement with the experimental data. The approach allows also predictions for the angular correlation between heavy-flavor hadrons (or their decay electrons) and the charged particles produced in the fragmentation of the heavy-quark strings.

Using 5.33 × 106 single muons collected in 1.46 × 104 live hours by MACRO during the period 1991–1994, we have searched for a correlation between variations in the underground muon rate, Nμ, and seasonal temperature variations in the atmosphere. These correlations are found to be present with high statistical significance. Analysis of the relatively complete December 1992–December 1994 subset of the data yields a value for the temperature coefficient, αT = (TNμ)(∂Nμ∂T) = 0.83±0.13. Analysis of the total data set gives consistent results. We have compared this result with the hypothesis that the muons observed in MACRO come from pion decays alone. Although our result is consistent with the 'pion only' hypothesis, a discussion of the sensitivity of our data sample to the kaon component of the cascades leading to observed muons underground will also be presented.

The energy of atmospheric neutrinos detected by MACRO was estimated using multiple coulomb scattering of upward throughgoing muons. This analysis allows a test of atmospheric neutrino oscillations, relying on the distortion of the muon energy distribution. These results have been combined with those coming from the upward throughgoing muon angular distribution only. Both analyses are independent of the neutrino flux normalization and provide strong evidence, above the 4 sigma level, in favour of neutrino oscillations.

.The production of \({\rm J}/\psi\) and \(\psi^\prime\) charmonium states in proton-nucleus interactions has been investigated by the NA50 experiment, at the CERN SPS. High statistics data sets were collected with collisions induced by 450 GeV protons incident on Be, Al, Cu, Ag and W targets. The \({\rm J}/\psi\) and \(\psi^\prime\) production cross-sections have been determined for each p-A system and their dependences on the nucleus size have been studied, leading to the so-called normal nuclear absorption. Comparing the two patterns we see that the nuclear absorption is stronger for the \(\psi^\prime\) than for the \({\rm J}/\psi\). Given the high statistics of the data samples, the \(x_{\rm F}\) (or rapidity) differential cross-sections of the \({\rm J}/\psi\) and \(\psi^\prime\) states have also been studied, for each of the target nuclei.

We report on the first measurement of the flux of upgoing muons resulting from interactions of atmospheric neutrinos in the rock below MACRO. The ratio of the observed to the expected number of events integrated over all nadir angles is 0.73 ± .09stat. ± .06sys. ± .12theor.. The flux of upgoing muons as a function of nadir angle is presented and compared to Monte Carlo expectations. At the 90% confidence level, the data are consistent with no neutrino oscillations or some possible oscillation hypothese with the parameters suggested by the Kamiokande contained-event analysis.

A bstract The effect of event background fluctuations on charged particle jet reconstruction in Pb-Pb collisions at $ \sqrt {{{s_{\text{NN}}}}} = {2}{.76}\,{\text{TeV}} $ has been measured with the ALICE experiment. The main sources of non-statistical fluctuations are characterized based purely on experimental data with an unbiased method, as well as by using single high p t particles and simulated jets embedded into real Pb-Pb events and reconstructed with the anti- k t jet finder. The influence of a low transverse momentum cut-off on particles used in the jet reconstruction is quantified by varying the minimum track p t between 0.15 GeV/ c and 2 GeV/ c . For embedded jets reconstructed from charged particles with p t &gt; 0 . 15 GeV/ c , the uncertainty in the reconstructed jet transverse momentum due to the heavy-ion background is measured to be 11.3 GeV/ c (standard deviation) for the 10% most central Pb-Pb collisions, slightly larger than the value of 11.0 GeV/ c measured using the unbiased method. For a higher particle transverse momentum threshold of 2 GeV/ c , which will generate a stronger bias towards hard fragmentation in the jet finding process, the standard deviation of the fluctuations in the reconstructed jet transverse momentum is reduced to 4.8-5.0 GeV/ c for the 10% most central events. A non-Gaussian tail of the momentum uncertainty is observed and its impact on the reconstructed jet spectrum is evaluated for varying particle momentum thresholds, by folding the measured fluctuations with steeply falling spectra.

We perform an indirect search for Weakly Interacting Massive Particles (WIMPs) using the MACRO detector to look for neutrino-induced upward-going muons resulting from the annihilation of WIMPs trapped in the Sun and Earth. The search is conducted in various angular cones centered on the Sun and Earth to accommodate a range of WIMP masses. No significant excess over the background from atmospheric neutrinos is seen and limits are placed on the upward-going muon fluxes from Sun and Earth. These limits are used to constrain neutralino particle parameters from supersymmetric theory, including those suggested by recent results from DAMA/NaI.

High-energy gamma-ray astronomy is now a well-established field, and several sources have been discovered in the region from a few giga-electron volts up to several tera-electron volts. 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 weakly interacting, massive particles (WIMPs) at the center of galaxies with black holes. We present the results of a search for pointlike sources using 1100 upward-going muons produced by neutrino interactions in the rock below and inside the Monopole Astrophysics and Cosmic Ray Observatory (MACRO) detector in the underground Gran Sasso Laboratory. These data show no evidence of a possible neutrino pointlike source or of possible correlations between gamma-ray bursts and neutrinos. They have been used to set flux upper limits for candidate pointlike sources which are in the range 10-14-10-15 cm-2 s-1.

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.

Muon pairs produced in Pb–Pb interactions at 158 GeV/c per nucleon are used to study the transverse momentum distributions of the J/ψ, ψ′ and dimuons in the mass continuum. In particular, the dependence of these distributions on the centrality of the Pb–Pb collision is investigated in detail.

The cosmic ray primary composition in the energy range between 1015 and 1016 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., 105 m2 collecting area) and the MACRO underground detector (963 m a.s.l., 3100 m w.e. of minimum rock overburden, 920 m2 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 (Nμ) 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°. 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 Nμ−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) of Δγ=0.7±0.4 at E0∼4×1015 eV. 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.

Soft-hadron measurements in high-energy collisions of small systems like p-Pb and d-Au show peculiar qualitative features (long-range rapidity correlations, flattening of the p T -spectra with increasing hadron mass and centrality, non-vanishing Fourier harmonics in the azimuthal particle distributions) suggestive of the formation of a strongly-interacting medium displaying a collective behaviour, with a hydrodynamic flow as a response to the pressure gradients in the initial conditions. Hard observables (high-p T jet and hadron spectra) on the other hand, within the current large systematic uncertainties, appear only midly modified with the respect to the benchmark case of minimum-bias p-p collisions. What should one expect for heavy-flavour particles, initially produced in hard processes but tending, in the nucleus-nucleus case, to approach kinetic equilibrium with the rest of the medium? This is the issue we address in the present study, showing how the current experimental findings are compatible with a picture in which the formation of a hot medium even in proton-nucleus collisions modifies the propagation and hadronization of heavy-flavour particles.

We have analyzed 44.3M single muons collected by MACRO from 1991 through 2000 in 2145 live days of operation. We have searched for the solar diurnal, apparent sidereal, and pseudosidereal modulation of the underground muon rate by computing hourly deviations of the muon rate from 6 month averages. We find evidence for statistically significant modulations with the solar diurnal and the sidereal periods. The amplitudes of these modulations are <0.1%, and are at the limit of the detector statistics. The pseudosidereal modulation is not statistically significant. The solar diurnal modulation is due to the daily atmospheric temperature variations at 20 km, the altitude of primary cosmic ray interactions with the atmosphere; MACRO is the deepest experiment to report this result. The sidereal modulation is in addition to the expected Compton-Getting modulation due to solar system motion relative to the local standard of rest; it represents motion of the solar system with respect to the galactic cosmic rays toward the galactic plane.Received 5 August 2002DOI:https://doi.org/10.1103/PhysRevD.67.042002©2003 American Physical Society

psi' production is studied in Pb-Pb collisions at 158 GeV/c per nucleon incident momentum. Absolute cross-sections are measured and production rates are investigated as a function of the centrality of the collision. The results are compared with those obtained for lighter colliding systems and also for the J/psi meson produced under identical conditions.

Abstract We present a new model for the description of heavy-quark hadronization in relativistic heavy-ion collisions in the presence of a reservoir of lighter thermal particles with which recombination can occur leading to the formation of color-singlet clusters. Color neutralization is assumed to occur locally, within the same fluid cell occupied by the heavy quark and it proceeds via the recombination of the latter with light antiquarks (quarks) or diquarks (anti-diquarks), which are assumed to be present in the medium with thermal abundance as effective degrees of freedom around the QCD crossover temperature $$T_c$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> . Typically the resulting color-singlet clusters have quite low invariant mass, in most of the cases below 4 GeV, and in this case they are assumed to undergo an isotropic 2-body decay in their local rest-frame. Heavier clusters are instead fragmented as Lund strings. The possibility of recombination with light diquarks enhances the yields of charmed baryons, in qualitative agreement with recent measurements. The assumption of local color neutralization leads to a strong space-momentum correlation, which provides a substantial enhancement of the collective flow of the final-state charmed hadrons, affecting both their momentum and their angular distributions.

J/ψ and ψ′ production cross-sections are measured in pp and pd collisions at 450 GeV/c at the CERN-SPS. The Drell-Yan cross section for muon pairs in the mass range [4.3–8.0] GeV/c2 is also determined in the same experiment.

Charmonium production in p–A collisions is a unique tool for the study of the interaction of bound cc states in nuclear matter. It can provide details on the basic features of the resonance formation mechanism and, in particular, on its non-perturbative aspects. In this Letter, we present an experimental study of charmonia and Drell–Yan production in proton–nucleus collisions at 450 GeV/c. The results are analyzed in the framework of the Glauber model and lead to the values of the nuclear absorption cross-section σabspA for J/ψ and ψ′. Then, we compare the J/ψ absorption in proton–nucleus and sulphur–uranium interactions, using NA38 data. We obtain that, for the J/ψ, σabspA and σabsSU are compatible, showing that no sizeable additional suppression mechanism is present in S–U collisions, and confirming that the anomalous J/ψ suppression only sets in for Pb–Pb interactions.

The MACRO detector, located in the underground Gran Sasso Laboratory, had its initial data run from February 27 to May 30, 1989, using the first supermodule (SΩ∼800 m2sr). Approximately 245 000 muon events were recorded. Here are reported the results of the analysis of penetrating muons which determine the measured vertical muon flux at depths greater than 3000 m.w.e. In addition the data have been used to search for large scale anisotropies.

The production of vector mesons φ, ρ and ω has been measured in Pb–Pb collisions at 158 GeV/c per nucleon incident momentum at the CERN/SPS. The muon spectrometer of experiment NA50 detects φ, ρ and ω mesons via their μ+μ− decay channel in the collision center of mass rapidity range 0⩽yCM⩽1. The results reported here show that the relative production of the φ compared to the (ρ+ω) and the φ multiplicity per participant nucleon (Npart) increase with the centrality of the collision. On the other hand, the (ρ+ω) multiplicity per participant does not exhibit any Npart dependence within our errors. The inverse slope parameter as deduced from an exponential fit to the φ transverse mass distribution is 228±10 MeV. Our results are compared with those obtained by experiment NA49 and with theoretical calculations.

The primary cosmic ray (CR) proton, helium and CNO fluxes in the energy range 80–300 TeV are studied at the National Gran Sasso Laboratories by means of EAS-TOP (Campo Imperatore, 2005 m a.s.l.) and MACRO (deep underground, 3100 m w.e., the surface energy threshold for a muon reaching the detector being Eμth≈1.3 TeV). The measurement is based on: (a) the selection of primaries based on their energy/nucleon (i.e., with energy/nucleon sufficient to produce a muon with energy larger than 1.3 TeV) and the reconstruction of the shower geometry by means of the muons recorded by MACRO in the deep underground laboratories; (b) the detection of the associated atmospheric Cherenkov light (C.l.) signals by means of the C.l. detector of EAS-TOP. The C.l. density at core distance r>100 m is directly related to the total primary energy E0. Proton and helium (“p + He”) and proton, helium and CNO (“p + He + CNO”) primaries are thus selected at E0≃80 TeV, and at E0≃250 TeV, respectively. Their flux is measured: Jp+He(80TeV)=(1.8±0.4)×10−6 m−2 s−1 sr−1 TeV−1, and Jp+He+CNO(250TeV)=(1.1±0.3)×10−7 m−2 s−1 sr−1 TeV−1, their relative weights being: Jp+HeJp+He+CNO(250TeV)=0.78±0.17. By using the measurements of the proton spectrum obtained from the direct experiments and hadron flux data in the atmosphere, we obtain for the relative weights of the three components at 250 TeV: Jp:JHe:JCNO=(0.20±0.08):(0.58±0.19):(0.22±0.17). This corresponds to the dominance of helium over proton primaries at 100–1000 TeV, and a possible non-negligible contribution from CNO. The lateral distribution of Cherenkov light in Extensive Air Showers (EASs), which is related to the rate of energy deposit of the primary in the atmosphere, is measured for a selected proton and helium primary beam, and good agreement is found when compared with the one calculated with the CORSIKA/QGSJET simulation model.

The stochastic dynamics of c and b quarks in the fireball created in nucleus–nucleus collisions at the RHIC and LHC is studied employing a relativistic Langevin equation, based on a picture of multiple uncorrelated random collisions with the medium. Heavy-quark transport coefficients are evaluated within a pQCD approach, with a proper HTL resummation of medium effects for soft scatterings. The Langevin equation is embedded in a multi-step setup developed to study heavy-flavor observables in pp and AA collisions, starting from a NLO pQCD calculation of initial heavy-quark yields, complemented in the nuclear case by shadowing corrections, kT-broadening and nuclear geometry effects. Then, only for AA collisions, the Langevin equation is solved numerically in a background medium described by relativistic hydrodynamics. Finally, the propagated heavy quarks are made hadronize and decay into electrons. Results for the nuclear modification factor RAA of heavy-flavor hadrons and electrons from their semi-leptonic decays are provided, both for RHIC and LHC beam energies.

We employ the POWLANG transport setup, developed over the last few years, to provide new predictions for several heavy-flavour observables in relativistic heavy-ion collisions from RHIC to LHC center-of-mass energies. In particular, we focus on the development of the flow-harmonics v2 and v3 arising from the initial geometric asymmetry in the initial conditions and its associated event-by-event fluctuations. Within the same transport framework, for the sake of consistency, we also compare the nuclear modification factor of the p T spectra of charm and beauty quarks, heavy hadrons and their decay electrons. We compare our findings to the most recent data from the experimental collaborations. We also study in detail the contribution to the flow harmonics from the quarks decoupling from the fireball during the various stages of its evolution: although not directly accessible to the experiments, this information can shed light on the major sources of the final measured effect.

The observation of an anomalous J/ψ suppression in Pb–Pb collisions by the NA50 Collaboration can be considered as the most striking indication for the deconfinement of quarks and gluons at SPS energies. In this Letter, we determine the J/ψ suppression pattern as a function of the forward hadronic energy EZDC measured in a Zero Degree Calorimeter (ZDC). The direct connection between EZDC and the geometry of the collision allows us to calculate, within a Glauber approach, the precise relation between the number of participant nucleons Npart and EZDC. Then, we check if the experimental data can be better explained by a sudden or a smooth onset of the anomalous J/ψ suppression as a function of the number of participants.

A kinetic equation approach is applied to model anomalous J/ψ suppression at RHIC and SPS by absorption in a hadron resonance gas which successfully describes statistical hadron production in both experiments. The puzzling rapidity dependence of the PHENIX data is reproduced as a geometric effect due to a longer absorption path for J/ψ production at forward rapidity.

The charged particle multiplicity distribution dNch/dη has been measured by the NA50 experiment in Pb–Pb collisions at the CERN SPS. Measurements were done at incident energies of 40 and 158 GeV per nucleon over a broad impact parameter range. The multiplicity distributions are studied as a function of centrality using the number of participating nucleons (Npart), or the number of binary nucleon–nucleon collisions (Ncoll). Their values at midrapidity exhibit a power law scaling behaviour given by Npart1.00 and Ncoll0.75 at 158 GeV. Compatible results are found for the scaling behaviour at 40 GeV. The width of the dNch/dη distributions is larger at 158 than at 40 GeV/nucleon and decreases slightly with centrality at both energies. Our results are compared to similar studies performed by other experiments both at the CERN SPS and at RHIC.

A comprehensive formalism for the description of neutrino oscillations in the Earth in a general scheme with three massive neutrinos and the mass hierarchy m_1<<m_2<<m_3 is presented. Using this formalism, which is valid both in vacuum and in a medium, the matter effect on the oscillations of low-energy neutrinos is discussed, pointing out the existence of very long oscillations which are independent of the neutrino masses and the neutrino energy, and are very sensitive to the matter density along the neutrino trajectory. As an example of application of the formulation, a fit of the Kamiokande atmospheric neutrino data with the matter effect taken into account for neutrinos propagating in the Earth is presented. The results of the fit indicate that 4*10^{-3} eV^2 < m_3^2 < 4*10^{-2} eV^2 and the oscillation amplitudes in all channels (nu_mu<->nu_e, nu_mu<->nu_tau, nu_e<->nu_tau) could be large. Hence, long-baseline experiments with reactor (CHOOZ and Palo Verde) and accelerator (K2K, MINOS and ICARUS) neutrinos could observe neutrino oscillations in all channels with a relatively large statistics.

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 × 106 single muons, corresponding to a detector lifetime of 1.55y, 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 νμ 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.

We present the analysis of multiple-muon events collected with one supermodule (1013 h live time) and two supermodules (1195 h live time) of the MACRO detector at Gran Sasso, Italy.Multimuon rates are shown to be sensitive to primary-cosmic-ray energies between -50 TeV and several thousand TeV.Experimental data are compared with the expected rates from two composition models: a light (i.e. , proton-rich) and a heavy (i.e. , Fe-rich) composition.The predictions are based on a Monte Carlo simulation of the hadronic interactions of cosmic-ray nuclei, followed by a detailed tracking of the muons through the rock and the experimental apparatus.The results show good sensitivity of the MACRO detector to primary composition.The data exhibit a preference towards the light composition model.

Many galactic and extragalactic astrophysical sources are currently considered promising candidates as high-energy neutrino emitters. Astrophysical neutrinos can be detected as upward-going muons produced in charged-current interactions with the medium surrounding the detector. The expected neutrino fluxes from various models start to dominate on the atmospheric neutrino background at neutrino energies above some tens of TeV. We present the results of a search for an excess of high-energy upward-going muons among the sample of data collected by MACRO during ∼5.8 years of effective running time. No significant evidence for this signal was found. As a consequence, an upper limit on the flux of upward-going muons from high-energy neutrinos was set at the level of 1.7×10−14 cm−2 s−1 sr−1. The corresponding upper limit for the diffuse neutrino flux was evaluated assuming a neutrino power law spectrum. Our result was compared with theoretical predictions and upper limits from other experiments.

A negative search using, '& of the eventual MACRO detector has yielded nuclearite flux limits of 1.1&&10 ' cm sr 's ' for 10 ' & ni (0.1 g, and 5.5x 10 ' cm sr 's ' for m )O.l g.We have modified the formula of De Rujula and Glashow for the light yield of nuclearites to include the uv light absorbed and reemitted in the visible region, and proved that the MACRO sensitivity extends almost to the escape velocity of the Earth.Our Aux limit, therefore, can be used to address nuclearites that are possibly trapped in the solar system.

The MACRO detector was located in the Hall B of the Gran Sasso underground laboratories under an average rock overburden of 3700 hg/cm2. A transition radiation detector composed of three identical modules, covering a total horizontal area of 36 m2, 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/cm2.

Traditionally, events collected at relativistic heavy-ion colliders are classified according to some centrality estimator (e.g. the number of produced charged particles) related to the initial energy density and volume of the system. In a naive picture the latter are directly related to the impact parameter of the two nuclei, which sets also the initial eccentricity of the system: zero in the case of the most central events and getting larger for more peripheral collisions. A more realistic modelling requires to take into account event-by-event fluctuations, in particular in the nucleon positions within the colliding nuclei: collisions belonging to the same centrality class can give rise to systems with different initial eccentricity and hence different flow harmonics for the final hadron distributions. This issue can be addressed by an event-shape-engineering analysis, consisting in selecting events with the same centrality but different magnitude of the average bulk anisotropic flow and therefore of the initial-state eccentricity. In this paper we present the implementation of this analysis in the POWLANG transport model, providing predictions for the transverse-momentum and angular distributions of charm and beauty hadrons for event-shape selected collisions. In this way it is possible to get information on how the heavy quarks propagating (and hadronizing) in a hot environment respond both to its energy density and to its geometric asymmetry, breaking the perfect correlation between eccentricity and impact parameter which characterizes a modelling of the medium based on smooth average initial conditions

We study heavy-flavor hadron production in high-energy pp collisions, assuming the formation of a small, deconfined and expanding fireball where charm quarks can undergo rescattering and hadronization. We adopt the same in-medium hadronization mechanism developed for heavy-ion collisions, which involves Local Color-Neutralization (LCN) through recombination of charm quarks with nearby opposite color charges from the background fireball. Diquark excitations in the hot medium favor the formation of charmed baryons. The recombination process, involving closely aligned partons from the same fluid cell, effectively transfers the collective flow of the system to the final charmed hadrons. This framework can qualitatively reproduce the observed experimental findings in heavy-flavor particle-yield ratios, $p_T$-spectra and elliptic-flow coefficients. Our results provide new, complementary support to the idea that the collective phenomena observed in small systems have the same origin as those observed in heavy-ion collisions.

view Abstract Citations (27) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Muon Astronomy with the MACRO Detector Ahlen, S. ; Ambrosio, M. ; Antolini, R. ; Auriemma, G. ; Baldini, A. ; Bam, B. ; Barbarino, G. ; Barish, B. ; Battistoni, G. ; Bellotti, R. ; Bemporad, C. ; Bernardini, P. ; Bilokon, H. ; Bisi, V. ; Bloise, C. ; Bussino, S. ; Cafagna, F. ; Calicchio, M. ; Campana, P. ; Campana, D. ; Carboni, M. ; Cecchini, S. ; Cei, F. ; Chiarella, V. ; Chiera, C. ; Cobis, A. ; Cormack, R. ; Corona, A. ; Coutu, S. ; Decataldo, G. ; Dekhissi, H. ; Demarzo, C. ; de Vincenzi, M. ; di Credico, A. ; Diehl, E. ; Erriquez, O. ; Favuzzi, C. ; Ficenec, D. ; Forti, C. ; Foti, L. ; Fusco, P. ; Giacomelli, G. ; Giannini, G. ; Giglietto, N. ; Giubellino, P. ; Grassi, M. ; Green, P. ; Grillo, A. ; Guarino, F. ; Gustavino, C. and 75 more Abstract We have analyzed a sample of 1.8 x 10 exp 6 muons with E(mu) greater than about 1.3 TeV collected by the first and second supermodules of the MACRO detector at Gran Sasso during the period 1989 February to 1991 February. We have searched for an excess of muons of celestial origin over cosmic-ray background. Our search for steady sources in solid angle bins of 3.0 x 3.0 deg in the declination range -5 to 90 deg was negative; the upper limit with 95 percent C.L. to the muon flux at midlatitudes is less than about 2 x 10 exp -12/sq cm s. In addition, we have searched for muon excesses modulated by the orbital period of selected X-ray sources, including Cyg X-3, Cyg X-1, Her X-1, 4U 0115 + 63, and 4U 1907 + 09. We have no evidence of any bursting activity from Cyg X-3, during our search period, which includes the radio outburst of 1991 January. Publication: The Astrophysical Journal Pub Date: July 1993 DOI: 10.1086/172921 Bibcode: 1993ApJ...412..301A Keywords: Muons; Nuclear Astrophysics; Radiation Detectors; Relic Radiation; Frequency Distribution; Monte Carlo Method; Point Sources; Sky Surveys (Astronomy); X Ray Sources; Space Radiation; ELEMENTARY PARTICLES; GAMMA RAYS: OBSERVATIONS full text sources ADS | data products SIMBAD (8)

A search for slowly moving magnetic monopoles in the cosmic radiation was conducted from October 1989 to November 1991 using the large liquid scintillator detector subsystem of the first supermodule of the MACRO detector at the Gran Sasso underground laboratory.The absence of candidates established an upper limit on the monopole Aux of 5.6 x 10 cm sr s at 90% confidence level in the velocity range of 10 ~P ( 4 x 10 .This result places a new constraint on the abundance of monopoles trapped in our solar system.

We have measured directly the residual energy of cosmic ray muons crossing the MACRO detector at the Gran Sasso Laboratory. For this measurement we have used a transition radiation detector consisting of three identical modules, each of about 12 m^2 area, operating in the energy region from 100 GeV to 1 TeV. The results presented here were obtained with the first module collecting data for more than two years. The average single muon energy is found to be 320 +/- 4 (stat.) +/- 11 (syst.) GeV in the rock depth range 3000-6500 hg/cm^2. The results are in agreement with calculations of the energy loss of muons in the rock above the detector.

Multimuon data from the MACRO experiment at Gran Sasso have been analyzed using a new method, which allows one to estimate the primary cosmic ray fluxes. The estimated all-particle spectrum is higher and flatter than the one obtained from direct measurements but is consistent with EAS array measurements. The spectral indexes of the fitted energy spectrum are 2.56$\ifmmode\pm\else\textpm\fi{}$0.05 for $E&lt;$500 TeV and 2.9$\ifmmode\pm\else\textpm\fi{}$0.3 for $E&gt;$5000 TeV with a gradual change at intermediate energies. The average mass number shows little dependence on the primary energy below 1000 TeV, with a value of 10.1$\ifmmode\pm\else\textpm\fi{}$2.5 at 100 TeV. At higher energies the best fit average mass shows a mild increase with energy, even though no definite conclusion can be reached taking into account errors. The fitted spectra cover a range from $\ensuremath{\sim}$ 50 TeV up to several thousand TeV.

In this letter we present the results of the search for massive magnetic monopoles in the penetrating cosmic ray radiation using the various subdetectors of the MACRO apparatus, during the period 1989–1995. Flux limits are given for the β = vc range 4 × 10−5 < β < 1; for 10−4 < β < 10−1 the limits are below the Parker bound, ∼ 10−15 cm−2s−1sr−1.

We describe the techniques chosen to search tor magnetic monopoles using the MACRO streamer tube sub-system. The hardware and the details of the analysis procedures will be discussed also. The results for slowly moving monopoles are reported from a first data taking period using only part of the detector.

A measurement of the underground muon decoherence function has been performed using the multiple muon events collected by the MACRO detector at the Gran Sasso National Laboratory. A detector-independent analysis is presented for different zenith regions and rock depths; this allows direct comparison with any model of hadronic interactions. The measured decoherence function is compared with the predictions of a Monte Carlo simulation based on data taken by recent collider experiments.

MACRO was an experiment that ran in the Laboratori Nazionali del Gran Sasso from 1988 to 2000. Its principal goal was to observe magnetic monopoles or set significantly lower experimental flux limits than had been previously available in the velocity range from about β=10−4 to unity. In addition it made a variety of other observations. Examples are: setting flux limits on other so far unobserved particles such as nuclearites and lightly ionizing particles, searching for WIMP annihilations in the Earth and the Sun and for neutrino bursts from stellar collapses in or near our Galaxy, and making measurements relevant to high energy muon and neutrino astronomy and of the flux of up-going muons as a function of nadir angle showing evidence for neutrino oscillations.The apparatus consisted of three principal types of detectors: liquid scintillator counters, limited streamer tubes, and nuclear track etch detectors. In addition, over part of its area it contained a transition radiation detector. The general design philosophy emphasized redundancy and complementarity. This paper describes the technical aspects of the complete MACRO detector, its operational performance, and the techniques used to calibrate it and verify its proper operation. It supplements a previously published paper which described the first portion of the detector that was built and operated.

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.

Muon pairs produced in PbPb interactions at 158 GeV/c per nucleon and in p-A interactions at 400 GeV/c, together with older S-U results obtained at 200 GeV/c are used to study the transverse momentum and transverse mass distributions of the J/Ψ.

We extend our POWLANG transport setup for the modelling of heavy-flavour production in heavy-ion collisions to the case of full 3+1 simulations, dropping the approximation of longitudinal boost-invariance of the background medium. This enables us to provide predictions for observables for which the rapidity dependence is essential in order to obtain a non-vanishing signal, like the directed flow $v_1$, and to get reliable results also for kinematic distributions of heavy-flavour particles at forward rapidity. We compare our predictions with experimental data obtained in Au-Au and Pb-Pb collisions at RHIC and at the LHC.

We present a measurement of the underground decoherence function using multi-muon events observed in the MACRO detector at Gran Sasso at an average depth of $3800 \mathrm{hg}/{\mathrm{cm}}^{2}.$ Muon pair separations up to 70 m have been measured, corresponding to parent mesons with ${P}_{\ensuremath{\perp}}&lt;~1$--$2 \mathrm{GeV}/c.$ Improved selection criteria are used to reduce detector effects mainly in the low distance separation region of muon pairs. Special care is given to a new unfolding procedure designed to minimize systematic errors in the numerical algorithm. The accuracy of the measurement is such that the possible contribution of rare processes, such as ${\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}+\stackrel{\ensuremath{\rightarrow}}{N}{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}+N+{\ensuremath{\mu}}^{+}+{\ensuremath{\mu}}^{\ensuremath{-}},$ can be experimentally studied. The measured decoherence function is compared with the predictions of the hadronic interaction model of the HEMAS Monte Carlo code. Good agreement is obtained. We interpret this agreement to indicate that no anomalous ${P}_{\ensuremath{\perp}}$ components in soft hadron-nucleus and nucleus-nucleus collisions are required by the MACRO experimental data. Preliminary comparisons with other Monte Carlo codes point out that the uncertainties associated with the hadronic interaction model may be as large as 20%, depending on the energy. MACRO data can be used as a benchmark for future work on the discrimination of shower models in the primary energy region around and below the knee of the spectrum.

The charged particle distributions dNch/dη have been measured by the NA50 experiment in Pb–Pb collisions at the CERN SPS. Measurements have been done at incident energies of 158 and 40 GeV per nucleon over a broad impact parameter range. Results obtained with two independent centrality estimators, namely the neutral transverse energy ET and the forward energy EZDC, are reported.

We discuss the preparation of different samples of the CR39 polymer and a number of tests performed with high energy heavy ions. The quality and reproducibility of the manufactured CR39 is discussed as well as the implications for a large area detector (MACRO) used for a search for cosmic magnetic monopoles.

Combined measurements of extensive air showers at the surface and high-energy muons deep underground have been initiated at the Gran Sasso Laboratory. The underground detector is the first supermodule of MACRO (area = 140 m2, depth = 3100 m of water equivalent, Eμ>1.3 TeV) and the surface detector is the EAS-TOP array (altitude 2000 m above sea level, total enclosed area A∼105 m2). We discuss the correlation technique, the comparison between the shower parameters as determined by the two detectors, and some of the characteristics of the reconstructed events.Received 12 February 1990DOI:https://doi.org/10.1103/PhysRevD.42.1396©1990 American Physical Society

In this paper, the first of a two-part work, we present the reconstruction and measurement of muon events detected underground by the MACRO experiment at Gran Sasso ${(E}_{\ensuremath{\mu}}&gt;~$ 1.3 TeV in atmosphere). The main aim of this work is to discuss the muon multiplicity distribution as measured in the detector. The data sample analyzed consists of $4.4\ifmmode\times\else\texttimes\fi{}{10}^{6}$ muon events, of which $\ensuremath{\sim}$ 263 000 are multiple muons, corresponding to a total live time of 5850 h. In this sample, the observed multiplicities extend above ${N}_{\ensuremath{\mu}}$=35, with intermuon separations up to 50 m and beyond. Additional complementing measurements, such as the inclusive muon flux, the angular distribution, and the muon separation distribution (decoherence), are also included. The physical interpretation of the results presented here is reported in the following companion paper.

MACRO is designed to make a multiply redundant search for GUT magnetic monopoles over a wide velocity range. The 100 MHz pulse height recorder and synchronous encoder (PHRASE) and the energy reconstruction processor (ERP) are two components of that search, both based on the MACRO liquid scintillator. They are sensitive to monopoles with or without captured nuclei in the range β ∼ 10−3 to β ∼ 1. Here, the performance of these systems is discussed, including also analysis methods and background evaluations.

Using data collected by the MACRO experiment during the years 1989-1996, we show evidence for the shadow of the moon in the underground cosmic ray flux with a significance of 3.6σ.This detection of the shadowing effect is the first by an underground detector.A maximum-likelihood analysis is used to determine that the angular resolution of the apparatus is 0.9 • ± 0.3 • .These results demonstrate MACRO's capabilities as a muon telescope by confirming its absolute pointing ability and quantifying its angular resolution.

A search for lightly ionizing particles has been performed with the MACRO detector. This search was sensitive to particles with charges between $\fractional{5}$$e$ and close to the charge of an electron, with $\beta$ between approximately 0.25 and 1.0. Unlike previous searches both single track events and tracks buried within high multiplicity muon showers were examined. In a period of approximately one year no candidates were observed. Assuming an isotropic flux, for the single track sample this corresponds to a 90% C.L. upper flux limit $\Phi \leq 9.2 \times 10^{-15} cm^{-2} sec^{-1} sr^{-1}$ .

The MACRO experiment has been running as a supernova neutrino detector since 1989 and is sensitive to the whole galaxy since the beginning of 1992. A galactic supernova would produce some hundreds of νe events in the detector. We describe our stellar gravitational collapse online monitors and alarm system, and present the results of a search for neutrino bursts from supernovae during a period of 1.5 yr.

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.

P. Cortese’) for the NA50 Collaboration: B. Alessandrol’) C. Alexa4) R. Arnaldi M. Bedjidian”),‘S. Beole hglin’), A. Baldit3), ‘ll) ‘V. Boldea4), P. Bordalo’y@, S.R. Boreusteinlo~b), G. Borges7), A. Bussiere’), L. Capelli “),‘C. Castanier3), J. Castor 3), B. Chaurandl”), B. Cheynis12), E. Chiavassa”), C. Cicalb5), T. Claudino ‘) M.P. Cometsg), S. Constantinescu , 4), P. Cortesel), J. Cruz’), A. de Falco’), N. de Marco”), G. Dellacasa’), A. Devaux3), S. Dita4), 0. Drapier”), B. Espagnon3), J. Fargeix3), P. Force3), M. Gallio 11), Y.K. Gavrilov’), C. Gerschelg), P. Giubellinoll>c), M.B. Golubeva’), M. Gonin”), A.A. Grigorian13) S. Grigorian13), J Y Grossiord12) F.F. Guber’) A. Guichard . . 12), H. Gulkanyan 13), R. Haroutunian”), M. Idzikl’~d~, D. Jouan’), T.L. Karavitchew?) R. Hakobyan’3), L. Kluberg’O) A.B. Kurepin8), Y. Le Bornecg), C. Lourenqo’) P. Macciotta5), M. Mac Cormick;) A. Marzari-Chiesa”), M. Masera”), A. Masoni5), M. Mouteno”), A. Musso~~), P. Petiau”), A. Piccotti”), J.R. Pizzi”), W.L. Prado da Silvall*e), F. Prino”), G. Puddu’), C. Quintans’), L. Ramello’), S. Ftarno~~~~), P. Rata Mendes ‘), L. Riccati”), A. Romana’O), H. Santos’), P. Saturnini3), E. Scala& E. Scomparin 11), S. Serci5), R. Shahoyan7f), F. Sigaudo”), M. Sitta’), P. Sonderegger’+), X. Tarragog), N.S. Topilskaya8), G.L. Usai5), E. Vercellin”), L. Villatteg), N. Willisg), T. Wug). i) Univ. de1 Piemonte Orientale, Alessaudria and INFN-Torino, Italy. 2, LAPP, CNRSIN2P3, Annecy-le-Vieux, France. 3, LPC, Univ. Blaise Pascal and CNRSIN2P3, Aubiere, France. 4, IFA, Bucharest, Romania. 5, Univ. di Cagliari and INFN, Cagliari, Italy. 6, CERN, Geneva, Switzerland. ?) LIP, Lisbon, Portugal. 8, INR, Moscow, Russia. ‘1 IPN, Univ. de Paris-Sud and CNRS-IN2P3, Orsay, France. lo) Laboratoire Leprince-Ringuet, Ecole Polytechnique and CNRS-INZPS, Palaiseau, France. ii) Univ. di Torino and INFN, Torino, Italy. 12) IPN, Univ. Claude Bernard Lyon-I and CNRSIN2P3, Villeurbaune, France. i3) YerPhI, Yerevan, Armenia. a) Also at IST, Lisbon, Portugal. b, On leave from York College, CUNY, New York, USA. =) Also at CERN, Geneva, Switzerland. d, Also at FPNT, Cracow, Poland. e, Now at UERJ, Rio de Janeiro, Brazil. ‘) On leave from YerPhI, Yerevan, Armenia.

We present a study of the correlations in the arrival times of about 1016 single and multiple muons detected by the first two MACRO supermodules. The time correlations, from milliseconds to several hundrends of seconds, have been analyzed in terms of the random distribution, with which they are consistent. An analysis of the arrival times (up to 180 ns) of the muons from the same multimuon event is also given.

We have studied the constraints imposed by the results of neutrino oscillation experiments on the effective Majorana mass |<m>| that characterizes the contribution of Majorana neutrino masses to the matrix element of neutrinoless double-beta decay. We have shown that in a general scheme with three Majorana neutrinos and a hierarchy of neutrino masses (which can be explained by the see-saw mechanism), the results of neutrino oscillation experiments imply rather strong constraints on the parameter |<m>|. From the results of the first reactor long-baseline experiment CHOOZ and the Bugey experiment it follows that |<m>| < 3x10^{-2} eV if the largest mass-squared difference is smaller than 2 eV^2. Hence, we conclude that the observation of neutrinoless double-beta decay with a probability that corresponds to |<m>| > 10^{-1} eV would be a signal for a non-hierarchical neutrino mass spectrum and/or non-standard mechanisms of lepton number violation.

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 $\sim 1 mb$.

We have designed a silicon detector to measure the angular distribution and the multiplicity of charged secondaries produced in high-energy PbPb interactions. It will be used to characterize the events in the NA50 experiment. The experiment will have to function at very high rate, and the silicon detectors will have to operate in the high-radiation area close to the target. Therefore, the detector will have to be very fast (dead time below 50 ns), radiation resistant (up to the Mrad level as dose and up to more than 1013 particles/cm2 as non-ionizing damage) and of high granularity. The conditions on noise, speed and radiation hardness are comparable to the ones foreseen at the future Large Hadron Collider at CERN. We present here the detector design, discuss some of the solutions which have been investigated and report first results on the components of the system which have been designed and produced up to now.

The MACRO underground detector at Gran Sasso Laboratory recorded 60 million secondary cosmic ray muons from February 1989 until December 2000. Different techniques were used to analyze this sample in search for density excesses from astrophysical point-like sources. No evidence for DC excesses for any source in an all-sky survey is reported. In addition, searches for muon excess correlated with the known binary periods of Cygnus X-3 and Hercules X-1, and searches for statistically significant bursting episodes from known γ-ray sources are also proved negative.

We present the set of measurements carried out by the NA50 experiment to study J/ψ production in proton- and ion-induced reactions. We also make use of results obtained previously under similar conditions by experiments NA51, NA38 and NA3. All these measurements were performed in fixed target experiments at the CERN SPS. Due to accelerator constraints, momentum was 450, 400 and 200 GeV/c for incident proton beams (corresponding to √s = 29.0, 27.4, 19.4 GeV respectively) whereas, for ion beams, incident momentum was 200 GeV/nucleon for oxygen and sulfur and 158 GeV/nucleon for Pb beams (√s = 19.4 and √s = 17.2 GeV respectively). The p-A data allow us to determine with high accuracy the absorption cross section of the (pre-)resonant cc state with nuclear matter. The J/ψ production cross section normally expected for ion-induced reactions can then be determined and compared to the results obtained from the data collected for oxygen- and sulfur-induced collisions. Finally, we also present the most recent results on J/ψ production in Pb-Pb interactions. They are based on the last data sample collected with an improved experimental set-up and are compared with the expectations inferred from similar measurements on lighter nuclei collisions.

The J/ψ azimuthal distribution relative to the reaction plane has been measured by the NA50 experiment in Pb-Pb collisions at 158 GeV/nucleon. Various physical mechanisms related to charmonium dissociation in the medium created in the heavy ion collision are expected to introduce an anisotropy in the azimuthal distribution of the observed J/ψ mesons at SPS energies. Hence, the measurement of J/ψ elliptic anisotropy, quantified by the Fourier coefficient v 2 of the J/ψ azimuthal distribution relative to the reaction plane, is an important tool to constrain theoretical models aimed at explaining the anomalous J/ψ suppression observed in Pb-Pb collisions. We present the measured J/ψ yields in different bins of azimuthal angle relative to the reaction plane, as well as the resulting values of the Fourier coefficient v 2 as a function of the collision centrality and of the J/ψ transverse momentum. The reaction plane has been estimated from the azimuthal distribution of the neutral transverse energy detected in an electromagnetic calorimeter. The analysis has been performed on a data sample of about 100 000 events, distributed in five centrality or p T sub-samples. The extracted v 2 values are significantly larger than zero for non-central collisions and are seen to increase with p T.

The calibration and performance of the Silicon Drift Detector of the ALICE experiment during the 2008 cosmic ray run will be presented. In particular the procedures to monitor the running parameters (baselines, noise, drift speed) are detailed. Other relevant parameters (SOP delay, time-zero, charge calibration) were also determined.

The NA50 Collaboration has measured heavy-quarkonium production in p-A collisions at 450 GeV incident energy (sqrt(s) = 29.1 GeV). We report here results on the production of the Upsilon states and of high-mass Drell-Yan muon pairs (m > 6 GeV). The cross-section at midrapidity and the A-dependence of the measured yields are determined and compared with the results of other fixed-target experiments and with the available theoretical estimates. Finally, we also address some issues concerning the transverse momentum distributions of the measured dimuons.

These proceedings collect the presentations given at the first three meetings of the INFN "Workshop on Monte Carlo's, Physics and Simulations at the LHC", held at the Frascati National Laboratories in 2006. The first part of these proceedings contains pedagogical introductions to several basic topics of both theoretical and experimental high pT LHC physics. The second part collects more specialised presentations.

The NA50 experiment at the CERN SPS has been equipped with a Cerenkov quartz detector to measure the charge of projectilelike fragments emitted in interactions of the lead beam of 158AGeV with a 12 mm thick lead target. A clear fission peak has been observed in the light output distribution of the fragment detector and the measured number of fission events per incident Pb ion is (1.26±0.16)×10−2. The information provided by the NA50 zero-degree calorimeter has allowed us to check that fission occurs in extremely peripheral collisions. To provide the first information about the fission mechanism, the expected yield of electromagnetic fission events in our experimental conditions has been computed: it turns out to be about 40% smaller than the observed one. The approximations necessarily made in our calculation as well as the contribution due to fission induced by nuclear interaction could account for such a difference.Received 22 July 1998DOI:https://doi.org/10.1103/PhysRevC.59.876©1999 American Physical Society

Two methods of folding a distribution of simulated muon bundle events underground with a finite size detector are compared. A general strategy to fully exploit the statistics produced by the event generator is described. The aim is to minimize the amount of computing time required in the analysis of data taken by large area detectors. The method presented here can also be used for other applications typical of cosmic ray physics.

The NA50 and NA38 experiments have studied muon pair production in p-A and nucleus-nucleus collisions at the CERN SPS. Results on dimuons in the invariant mass region between the and the J/ψ masses (IMR) are presented. The standard sources of muon pairs in the IMR are the Drell-Yan process and the semileptonic decay of charmed mesons. A new four-dimensional unfolding method is applied to the data. The p-A results are well described in terms of these known sources, which, in contrast, fail to explain nucleus-nucleus data: an extra yield of muon pairs is observed. Although this excess is compatible with an enhanced production of charmed hadrons, other possible sources cannot be excluded. In particular, a comparison between data and predictions from a theoretical model which calculates the production of thermal dimuons is presented in this paper.

We present a new model for the description of heavy-flavor hadronization in relativistic heavy-ion collisions. We explore its effect on the charmed hadron yields and kinematic distributions once the latter is applied at the end of transport calculations used to simulate the propagation of heavy quarks in the deconfined fireball produced in the collision. The model is based on the formation of color-singlet clusters through the recombination of charm quarks with light antiquarks or diquarks from the same fluid cell. This local mechanism of color neutralization leads to a strong space-momentum correlation, which provides a substantial enhancement of charmed baryon production and of the collective flow of all charmed hadrons.

Recent experimental results on the Lambda_c/D^0 ratio in proton-proton collisions have revealed a significant enhancement compared to expectations based on universal fragmentation fractions/functions across different colliding systems, from e+e- to pp. This unexpected enhancement has sparked speculation about the potential effects of a deconfined medium impacting hadronization, previously considered exclusive to heavy-ion collisions. In this study, we propose a novel approach that assumes the formation of a small, deconfined, and expanding fireball even in pp collisions, where charm quarks can undergo rescattering and hadronization. We make use of the same in-medium hadronization mechanism developed for heavy-ion collisions, which involves local color-neutralization through recombination of charm quarks with nearby opposite color charges from the background fireball. Our model incorporates the presence of diquark excitations in the hot medium, which promotes the formation of charmed baryons. Moreover, the recombination process, involving closely aligned partons from the same fluid cell, effectively transfers the collective flow of the system to the final charmed hadrons. We show that this framework can qualitatively reproduce the observed experimental findings in heavy-flavor particle-yield ratios, $p_T$-spectra and elliptic-flow coefficients. Our results provide new, complementary supporting evidence that the collective phenomena observed in small systems naturally have the same origin as those observed in heavy-ion collisions

The design, operation and performance of the silicon strip Multiplicity Detector for the heavy-ion experiment NA50 at CERN are presented. The main features of the detector are high speed (50MHz sampling frequency), high granularity (more than 13,000 strips), and good radiation resistance. The detector provided a measurement of event centrality in Pb–Pb collisions, as well as target identification and the measurement of charged particle pseudorapidity distributions as a function of centrality.

The fission of lead projectiles has been investigated at the CERN SPS by the NA50 experiment. For this study, a Cherenkov quartz detector was added to the standard NA50 setup to measure the charge of projectilelike fragments. The data collected on different targets at 40 and $158\phantom{\rule{0.3em}{0ex}}\text{GeV}∕c$ per nucleon are presented here. The contributions arising from the nuclear and the electromagnetic fission mechanism are extracted from the measured fission cross sections; the electromagnetic contribution is then compared to the Weizs\"acker-Williams predictions.

From proton, deuteron, S- and Pb-induced reactions, experiments NA38 and NA50 have measured muon pair production with various targets. In particular, the production rates of the , ω and ρ mesons have been simultaneously extracted and compared. Preliminary partial results of the most recent Pb–Pb measurement done in year 2000 by NA50 are presented here. They are also included in the comparison with the results obtained with lighter interacting nuclei.

The study of muon pairs in the mass region 1.5 < Mμμ < 2.5 GeV/c2 in 450 GeV/c p-A, 200 GeV/nucleon S-U and 158 GeV/nucleon Pb-Pb collisions is presented. In p-A interactions, the dimuon signal mass spectra are well described by a superposition of Drell-Yan and charmed meson semi-leptonic decay contributions, in agreement with previous experiments when considering a linear A dependence. In nucleus-nucleus reactions, taking only into account these two physical ingredients, a dimuon enhancement both with increasing A·B and centrality is observed.

The most recent and final results from the NA50 experiment on charmonia production in Pb-Pb interactions at 158 GeV/c per nucleon are presented. A strong J/ψ suppression is observed, which increases with the centrality of the collisions.

Charmonium suppression in Pb-Pb collisions at 158 GeV/c per nucleon is investigated in detail with the study of the transverse momentum distributions of J/ψ as a function of the centrality of the collision. It is shown that the observed J/ψ suppression in Pb-Pb interactions is particularly significant mainly at low transverse momentum where it strongly depends on centrality. For peripheral Pb-Pb collisions, the transverse momentum dependence of the J/ψ cross section is, as a function of centrality, qualitatively similar to the dependence observed in p-A and S-U collisions. Comparing peripheral and central Pb-Pb collisions, the data show a relative suppression in the whole pT range although its amplitude significantly decreases with increasing pT and becomes almost pT independent for the highest pT values.

Predictions for heavy-flavour production in relativistic heavy-ion experiments provided by the POWLANG transport setup, including now also an in-medium hadronization model, are displayed, After showing some representative findings for the Au-Au and Pb-Pb cases, a special focus will be devoted to the results obtained in the small systems formed in proton(deuteron)-nucleus collisions, where recent experimental data suggest the possible formation of a medium featuring a collective behaviour.

Abstract A new set of results obtained by the NA50 experiment for the J/ψ production at the CERN SPS is presented. Peripheral PbPb collisions benefit from an improved setup, confirming the departure from ordinary production observed for the most central collisions, which has suggested the occurrence of a quark gluon plasma formation. Improved comparative analyses of older datas confirms the θ meson yield increase with centrality and between systems. The interest of the ratio θ ω as a direct measurement of the strangeness increase is underlined.

We present a study of the transverse momentum and transverse mass of Jψ mesons produced in nucleus-nucleus and p-nucleus reactions. They include the most recent data collected by the NA50 experiment in PbPb and p-A reactions at 158 GeV/c and 400 GeV/c incident momentum respectively. Together with S-U results previously published by experiment NA38, the mean squared transverse momentum of Jψ mesons exhibit a scaling behaviour which could result from initial state parton interaction. However, for the most central PbPb collisions a saturation effect is observed as a function of centrality.

We study the stochastic dynamics of c and b quarks in the hot plasma produced in nucleus-nucleus collisions at RHIC and LHC, providing results for the nuclear modification factor R_AA and the elliptic flow coefficient v_2 of the single-electron spectra arising from their semi-leptonic decays. The initial QQbar pairs are generated using the POWHEG code, implementing pQCD at NLO. For the propagation in the plasma we develop a relativistic Langevin equation (solved in a medium described by hydrodynamics) whose transport coefficients are evaluated through a first-principle calculation. Finally, at T_c, the heavy quarks are made hadronize and decay into electrons: the resulting spectra are then compared with RHIC results. Predictions for LHC are also attempted.

We present recent results for heavy-flavor observables in nucleus-nucleus collisions at LHC energies, obtained with the POWLANG transport setup. The initial creation of c-cbar and b-bbar pairs is simulated with a perturbative QCD approach (POWHEG+PYTHIA); their propagation in the medium (created in the nucleus-nucleus or in proton-nucleus collision) is studied with the relativistic Langevin equation, here solved using weak-coupling transport coefficients. Successively, the heavy quarks hadronize in the medium. We compute the nuclear modification factor and the elliptic flow parameter of the final D mesons both in nucleus-nucleus and in (for the first time, in the POWLANG setup) proton-nucleus collisions and compare our results to experimental data.

We report on the simultaneous observation of atmospheric \ifmmode \check{C}\else \v{C}\fi{}erenkov light by a prototype five telescope array, GRACE, (Gran Sasso Air \ifmmode \check{C}\else \v{C}\fi{}erenkov Experiment) with deep underground muons in the MACRO (Monopole Astrophysics and Cosmic Ray Observatory). The telescope array was deployed at Campo Imperatore above the Gran Sasso Laboratory for a run completed in the fall of 1992. The total live time for the combined surface-underground operation was \ensuremath{\sim}100 h during which more than 300 events were seen in coincidence. The efficacy of this technique to monitor the electromagnetic and penetrating muon components of a cosmic-ray-induced cascade is discussed.