Event Topology Research Articles

On the magnetic topology of October/November 2003 events

We examine the topology of several magnetic ejecta events during October–November 2003. The Grad‐Shafranov reconstruction results from ACE magnetic and plasma data show magnetic flux rope configurations. Some are large scale, with sizes of tenths of an AU, typical of magnetic clouds. Some are of sizes hundredths of an AU. Their characteristic parameters are reported. Magnetic field data from Wind spacecraft are utilized to compare the prediction from numerical modeling with the actual measurement. Poor to good agreement is achieved. The deviations are discussed, particularly in the context of extremely high‐speed solar wind flows.

MACRO results on atmospheric neutrinos

We discuss the final results of the MACRO experiment on atmospheric neutrino oscillations. The data concern event topologies with average neutrino energies of ∼ 3 and ∼ 50 GeV. Multiple Coulomb Scattering of the high energy muons was used to estimate the neutrino energy event by event. The angular distributions, the L / E ν distribution, the particle ratios and the absolute fluxes all favor ν μ → ν τ oscillations with maximal mixing and Δ m 2 ≃ 0.0023 eV 2 . Emphasis is given to measured ratios which are not affected by Monte Carlo (MC) absolute normalization; a discussion is made on MC uncertainties. A preliminary search for possible Lorentz invariance violation contributions to atmospheric neutrino oscillations is presented and discussed.

Skeletal Muscle NAD(P)H Two-Photon Fluorescence Microscopy In Vivo: Topology and Optical Inner Filters

Two-photon excitation fluorescence microscopy (TPEFM) permits the investigation of the topology of intercellular events within living animals. TPEFM was used to monitor the distribution of mitochondrial reduced nicotinamide adenine dinucleotide (NAD(P)H) in murine skeletal muscle in vivo. NAD(P)H fluorescence emission was monitored (∼460nm) using 710–720nm excitation. High-resolution TPEFM images were collected up to a depth of 150μm from the surface of the tibialis anterior muscle. The NAD(P)H fluorescence images revealed subcellular structures consistent with subsarcolemmal, perivascular, intersarcomeric, and paranuclear mitochondria. In vivo fiber typing between IIB and IIA/D fibers was possible using the distribution and content of mitochondria from the NAD(P)H fluorescence signal. The intersarcomeric mitochondria concentrated at the Z-line in the IIB fiber types resulting in a periodic pattern with a spacing of one sarcomere (2.34±0.17μm). The primary inner filter effects were nearly equivalent to water, however, the secondary inner filter effects were highly significant and dynamically affected the observed emission frequency and amplitude of the NAD(P)H fluorescence signal. These data demonstrate the feasibility, and highlight the complexity, of using NAD(P)H TPEFM in skeletal muscle to characterize the topology and metabolic function of mitochondria within the living mouse.

Top Quark Mass Measurements at CDF

Recent measurements of the mass of the top quark (t) are presented using 162 pb−1 of data of pp¯ collisions at s=1.96 TeV collected by the CDF detector at the Tevatron collider during Run II. The analyses focus on the semi-leptonic decay mode tt¯→(blν)(b¯qq¯) with one or two identified bottom quarks (b). The Template Method reconstructs the invariant mass of the top quark in each event. The Multivariate Template Method enhances this approach by adding information on the event topology. The Dynamical Likelihood Method discriminates between possible mass values using top quark decay observables and attempts to use the maximum amount of information on top quarks provided by the Standard Model. All three methods produce similar results. The Dynamical Likelihood Method yields a top quark mass of 177.8−5.0+4.5(stat)±6.2(sys) GeV/c2.

A general search for new phenomena in ep scattering at HERA

A model-independent search for deviations from the Standard Model prediction is performed in e+p and e−p collisions at HERA using H1 data corresponding to an integrated luminosity of 117pb−1. For the first time all event topologies involving isolated electrons, photons, muons, neutrinos and jets with high transverse momenta are investigated in a single analysis. Events are assigned to exclusive classes according to their final state. A statistical algorithm is developed to search for deviations from the Standard Model in the distributions of the scalar sum of transverse momenta or invariant mass of final state particles and to quantify their significance. A good agreement with the Standard Model prediction is observed in most of the event classes. The most significant deviation is found for a topology containing an isolated muon, missing transverse momentum and a jet, consistent with a previously reported observation.

Auger FD: Detector Response to Simulated Showers and Real Event Topologies

The performance of the Auger Fluorescence telescope is discussed on the basis of a mass production chain. In order to get a realistic estimate of the detector resolution, a large number of fully simulated CORSIKA [1] showers have been used for this study. The propagation through the atmosphere and the detector response are taken into account and simulated in detail. Results for the the case of monocular reconstruction are presented here. No quality cuts for the event reconstruction have been applied so far. Finally, a schematic overview of the expected event topologies is given together with the display of a real event recently collected.

A general search for new phenomena in ep scattering at HERA

A model-independent search for deviations from the Standard Model prediction is performed in e + p and e − p collisions at HERA using H1 data corresponding to an integrated luminosity of 117 pb − 1 . For the first time all event topologies involving isolated electrons, photons, muons, neutrinos and jets with high transverse momenta are investigated in a single analysis. Events are assigned to exclusive classes according to their final state. A statistical algorithm is developed to search for deviations from the Standard Model in the distributions of the scalar sum of transverse momenta or invariant mass of final state particles and to quantify their significance. A good agreement with the Standard Model prediction is observed in most of the event classes. The most significant deviation is found for a topology containing an isolated muon, missing transverse momentum and a jet, consistent with a previously reported observation.

Sensitivity of robust vertex fitting algorithms

Robust vertex fitting algorithms are expected to improve the knowledge of the vertex position and of its uncertainty in the presence of mismeasured or misassociated tracks. Such contaminations are likely to happen in real data as well as in realistic detector simulations. This paper describes a simulation study of the sensitivity of two types of robust algorithms: a trimmed least squares estimator and an adaptive estimator. The statistical properties of the algorithms are studied as a function of the source and the level of contamination, and compared to the results obtained with classical least squares estimators. Two typical event topologies are studied: one resembling a high multiplicity primary vertex with a possible contamination from a nearby vertex and one resembling a low multiplicity secondary vertex in a jet.

EVENTS WITH ISOLATED CHARGED LEPTONS AND LARGE MISSING TRANSVERSE MOMENTUM AT HERA

Striking events with isolated charged leptons, large missing transverse momentum and large transverse momentum of the hadronic final state [Formula: see text] were observed at the electron proton collider HERA in a data sample corresponding to an integrated luminosity of about 130 pb-1. The H1 collaboration observed 11 events with isolated electrons or muons and with [Formula: see text]. Only 3.4±0.6 events were expected from Standard Model (SM) processes. Six of these events have [Formula: see text], while 1.3±0.3 events were expected. The ZEUS collaboration observed good agreement with the SM. However, ZEUS found two events with a similar event topology, but tau leptons instead of electrons or muons in the final state. Only 0.2±0.05 events were expected from SM processes. For various hypotheses, the compatibility of the experimental results was investigated with respect to the SM and with respect to possible explanations beyond the SM. Prospects for the high-luminosity HERA-II data taking period are given.

New MACRO results on atmospheric neutrino oscillations

The final results of the MACRO experiment on atmospheric neutrino oscillations are presented and discussed. The data concern different event topologies with average neutrino energies of ~3 and ~50 GeV. Multiple Coulomb Scattering of the high energy muons in absorbers was used to estimate the neutrino energy of each event. The angular distributions, the L/E_nu distribution, the particle ratios and the absolute fluxes all favour nu_mu --> nu_tau oscillations with maximal mixing and Delta m^2 =0.0023 eV^2. A discussion is made on the Monte Carlos used for the atmospheric neutrino flux. Some results on neutrino astrophysics are also briefly discussed.

The new LHCb trigger and DAQ strategy: a system architecture based on gigabit-ethernet

The LHCb software trigger has two levels: a high-speed trigger running at 1 MHz with strictly limited latency and a second level running below 40 kHz without latency limitations. The trigger strategy requires full flexibility in the distribution of the installed CPU power to the two software trigger levels because of the unknown background levels and event topology distribution at the time the LHC accelerator will start its operation. This requirement suggests using a common CPU farm for both trigger levels fed by a common data acquisition (DAQ) infrastructure. The limited latency budget of the first level of software trigger has an impact on the organization of the CPU farm performing the trigger function for optimal usage of the installed CPU power. We will present the architecture and the design of the hardware infrastructure for the entire LHCb software triggering system based on Ethernet as link technology that fulfills these requirements. The performance of the event-building of the combined traffic of both software trigger levels, as well as the expected scale of the system will be presented.

Search for neutral Higgs bosons in CP-conserving and CP-violating MSSM scenarios

This report summarizes the final results from the OPAL collaboration on searches for neutral Higgs bosons predicted by the Minimal Supersymmetric Standard Model (MSSM). CP-conserving and, for the first time at LEP, CP-violating scenarios are studied. New scenarios are also included, which aim to set the stage for Higgs searches at future colliders. The results are based on the data collected with the OPAL detector at e+e- centre-of-mass energies up to 209 GeV. The data are consistent with the prediction of the Standard Model with no Higgs boson produced. Model-independent limits are derived for the cross-sections of a number of event topologies motivated by predictions of the MSSM. Limits on Higgs boson masses and other MSSM parameters are obtained for a number of representative MSSM benchmark scenarios. For example, in the CP-conserving scenario m h-max where the MSSM parameters are adjusted to predict the largest range of values for mh at each tan β, and for a top quark mass of 174.3GeV, the domain 0.7 84.5GeV and mA > 85.0 GeV are obtained. For the CP-violating benchmark scenario CPX which, by construction, enhances the CP-violating effects in the Higgs sector, the domain tan β < 2.8 is excluded but no universal limit can be set on the Higgs boson masses. © Springer-Verlag / Societa Italiana di Fisica 2004.

MACRO results on atmospheric neutrino oscillations

The final results of the MACRO experiment on atmospheric neutrino oscillations are presented. The data concern different event topologies with average neutrino energies of ~ 3 and ~ 50 GeV. Multiple Coulomb Scattering of the high energy muons was used to estimate the neutrino energy event by event. The angular distributions, the L/E_nu distribution, the particle ratios and the absolute fluxes all favour nu_mu --> nu_tau oscillations with maximal mixing and Delta m^2 ~ 0.0023 eV^2. Emphasis is given to measured ratios which are not affected by Monte Carlo (MC) absolute normalization; a discussion is made on MC uncertainties.

General search for new phenomena in ep scattering at HERA

A model-independent search for deviations from the Standard Model prediction has been performed in e+p and e-p collisions at HERA using H1 data. All experimentally measurable event topologies involving isolated electrons, photons, muons, neutrinos and jets with high transverse momenta have been investigated. A good agreement with the Standard Model prediction is found in most of the event classes. A new algorithm has been developed to look for regions with large deviations from the Standard Model in the invariant mass and sum of transverse momenta distributions and to quantify the significance of the fluctuations observed. The largest deviation is found in topologies with an isolated muon, missing transverse momentum and a jet which confirms previous observations. About 2% of hypothetical Monte Carlo experiments would produce deviations more significant than the one observed in the corresponding distribution of sum of transverse momenta.

Development of a TPC for the future linear collider

A Time Projection Chamber is the primary option for the main tracker of the detector at a future e+e– linear collider. The tracking system has to face significantly more complicated event topologies and higher backgrounds compared to previous e+e– colliders, which puts stringent requirements on its overall design. The design issues and R&D plans for developing such a high performance TPC are presented. Particular emphasis is put on the R&D for a new type of gas amplification system, based on micro pattern gas detectors.

A variable for measuring masses at hadron colliders when missing energy is expected; mT2: the truth behind the glamour

We present the kinematic variable,mT2, which is in some ways similar to the more familiar ‘transverse mass’, but which can be used in events where two or more particles have escaped detection. We define this variable and describe the event topologies to which it applies, then present some of its mathematical properties. We then briefly discuss two case studies which show how mT2 is vital when reconstructing the masses of supersymmetric particles in mSUGRA-like and AMSB-like scenarios at the large hadron collider.

The TOTEM/CMS forward experiment at the LHC

At the CERN Large Hadron Collider (LHC) proton-proton and heavy ion collisions will be studied at energies corresponding to E lab = 10 17 eV cosmic-ray interactions. The possibilities to measure event topologies in these interactions that are relevant for the interpretation of cosmic-ray data are described. Minimum bias events are best studied in low luminosity ( L = 10 28 cm −2 s −1) runs with a beam optic with β ∗ of 1100 m. In particular, the combination of the TOTEM and CMS experiments allow a large pseudorapidity coverage for charged and neutral particles with simultaneous measurement of diffractive protons. The total cross-section will be determined to within 1%.

Magnetic topology of coronal mass ejection events out of the ecliptic: Ulysses/HI-SCALE energetic particle observations

Abstract. Solar energetic particle fluxes (Ee &gt; 38 keV) observed by the ULYSSES/HI-SCALE experiment are utilized as diagnostic tracers of the large-scale structure and topology of the Interplanetary Magnetic Field (IMF) embedded within two well-identified Interplanetary Coronal Mass Ejections (ICMEs) detected at 56° and 62° south heliolatitudes by ULYSSES during the solar maximum southern high-latitude pass. On the basis of the energetic solar particle observations it is concluded that: (A) the high-latitude ICME magnetic structure observed in May 2000 causes a depression in the solar energetic electron intensities which can be accounted for by either a detached or an attached magnetic field topology for the ICME; (B) during the traversal of the out-of-ecliptic ICME event observed in July 2000 energetic electrons injected at the Sun are channeled by the ICME and propagate freely along the ICME magnetic field lines to 62° S heliolatitude.Key words. Interplanetary physics (energetic particles; interplanetary magnetic fields)

Neutrino physics and astrophysics with the MACRO experiment at the Gran Sasso lab

The results of the MACRO experiment on atmospheric neutrino oscillations are presented and discussed. The data concern different event topologies with average neutrino energies of ~ 4 and ~ 50 GeV. The Multiple Coulomb Scattering of muons in the MACRO absorbers was used to estimate the neutrino energy of each event of the higher energy sample. The angular distributions, the absolute fluxes and the L/E distribution favour nu_mu <--> nu_tau oscillations with maximal mixing and Delta m^2=0.0025 eV^2. Results are presented on the searches for astrophysical sources of high energy muon neutrinos, for bursts of electron antineutrinos from stellar gravitational collapses and on indirect searches for WIMPs from the Earth and from the Sun.

Searching for a light fermiophobic Higgs boson at the Fermilab Tevatron

We propose new production mechanisms for light fermiophobic Higgs bosons ($h_f$) with suppressed couplings to vector bosons ($V$) at the Fermilab Tevatron. These mechanisms (e.g. $qq'\to H^\pm h_f$) are complementary to the conventional process $qq'\to Vh_f$, which suffers from a strong suppression of $1/\tan^2\beta$ in realistic models with a $h_f$. The new mechanisms extend the coverage at the Tevatron Run II to the larger $\tan\beta$ region, and offer the possibility of observing new event topologies with up to 4 photons.