109321144
HERA-B data acquisition system
Abstract The HERA-B Data Acquisition System implements a 50 kHz dead-timeless readout of 500 kB events requiring unprecedented speed of storing and data processing. The system is based on Digital Signal Processors (DSP) minimizing the number of components. A high bandwidth, low-latency DSP switching network provides full connectivity between the readout buffers and a PC farm which runs the higher level trigger. The design of the system and the achieved performance are described in this paper.
16373353
Mass limit for the lightest neutralino
AbstractIndirect limits on the mass of the lightest neutralino are derived from the results of searches for charginos, neutralinos, and sleptons performed with data taken by the ALEPH Collaboration at centre-of-mass energies near the Z peak and at 130 and 136 GeV. Within the context of the Minimal Supersymmetric Standard Model and when
$$M_{\tilde \nu } \geqslant 200 GeV/c^2 $$
, the boundMx> 12.8 GeV/c2 at the 95% confidence level applies for any tanβ. The impact of lighter sneutrinos is presented in the framework of SUSY grand unified theories; a massless neutralino is allowed only for a narrow range of tanβ,μ, and the scalar mass parameterm0. Finally, by including Higgs mass constraints and requiring that radiative electroweak symmetry breaking occur, more stringent bounds onMx as a function of tanβ are derived.
125825698
Improved measurement of the $\bar{B}^0$ and $B^{-}$ meson lifetimes
121018557
Measurement of triple gauge-boson couplings at 172 GeV
The triple gauge-boson couplings, αWΦ, αW and αBΦ, have been measured using 34 semileptonically and 54 hadronically decaying W+W− candidate events. The events were selected in the data recorded during 1996 with the ALEPH detector at 172 GeV, corresponding to an integrated luminosity of 10.65 pb−1. The triple gauge-boson couplings have been measured using optimal observables constructed from kinematic information of W+W− events. The results are in agreement with the Standard Model expectation.
120102665
Search for neutrino-induced charged current coherent pion production with carbon in a 1.3 GeV wide band muon neutrino beam
The search for charged-current coherent pion production induced by neutrinos with a mean energy of 1.3 GeV is discussed. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed and an upper limit of 0.60 × 10−2 is set on the cross section ratio of coherent pion production to the total charged current interaction at the 90% confidence level.
110110190
Architecture of the HERA-B data acquisition system
The HERA-B experiment was dedicated for the measurement of CP-violation in decays of neutral B-mesons and for investigating the physics of charmed particles. One of the experimental requirements is a highly selective on-line filtering of data due to high interaction rates and a low signal-to-background ratio. This demands a hierarchical trigger and a high bandwidth data acquisition system. The challenge for the DAQ system is a readout free of deadtime, which requires an unprecedent speed of storing and processing the data. In this paper we will outline the general architecture and hardware implementation of the HERA-B DAQ.
53998055
Ultrahigh Energy Neutrinos at the Pierre Auger Observatory
The observation of ultrahigh energy neutrinos (UHE nu s) has become a priority in experimental astroparticle physics. UHE nu s can be detected with a variety of techniques. In particular, neutrinos can interact in the atmosphere (downward-going nu) or in the Earth crust (Earth-skimming nu), producing air showers that can be observed with arrays of detectors at the ground. With the surface detector array of the Pierre Auger Observatory we can detect these types of cascades. The distinguishing signature for neutrino events is the presence of very inclined showers produced close to the ground (i.e., after having traversed a large amount of atmosphere). In this work we review the procedure and criteria established to search for UHE nu s in the data collected with the ground array of the Pierre Auger Observatory. This includes Earth-skimming as well as downward-going neutrinos. No neutrino candidates have been found, which allows us to place competitive limits to the diffuse flux of UHE nu s in the EeV range and above.
118466336
Precise measurement of the radial baryon acoustic oscillation scales in galaxy redshift surveys
In this paper we present a new method to extract cosmological parameters using the radial scale of the Baryon Acoustic Oscillations as a standard ruler in deep galaxy surveys. The method consists in an empirical parametrization of the radial 2-point correlation function, which provides a robust and precise extraction of the sound horizon scale. Moreover, it uses data from galaxy surveys in a manner that is fully cosmology independent and therefore, unbiased. A study of the main systematic errors and the validation of the method in cosmological simulations are also presented, showing that the measurement is limited only by cosmic variance. We then study the full information contained in the Baryon Acoustic Oscillations, obtaining that the combination of the radial and angular determinations of this scale is a very sensitive probe of cosmological parameters, able to set strong constraints on the dark energy properties, even without combining it with any other probe.
117442387
Star Formation and Molecular Gas in AGN
We present initial results from a survey of nearby AGN using the near infrared adaptive optics integral field spectrograph SINFONI. These data enable us to probe the distribution and kinematics of the gas and stars at spatial resolutions as small as 0.085arcsec, corresponding in some cases to less than 10pc. In this contribution we present results concerning (1) the molecular gas in the nucleus of NGC1068 and its relation to the obscuring torus; and (2) the stars which exist on spatial scales of a few tens of parsecs around the AGN, the evidence for their remarkably young age and extreme intensities, and their relation to the AGN.
17413031
SINFONI’s take on Star Formation, Molecular Gas, and Black Hole Masses in AGN
We present some preliminary (half-way) results on our adaptive optics spectroscopic survey of AGN at spatial scales down to 0.085”. Most of the data were obtained with SINFONI which provides integral field capability at a spectral resolution of R ∼ 4000. The themes on which we focus in this contribution are: star formation around the AGN, the properties of the molecular gas and its relation to the torus, and the mass of the black hole.
12537917
The Role of Molecular Gas in Obscuring Seyfert AGN
In a sample of local active galactic nuclei studied at a spatial resolution on the order of ten parsecs we show that the interstellar medium traced by the molecular hydrogen ν=1-0 S(1) line at 2.1 μm forms a geometrically thick, clumpy disk. The kinematics of the molecular gas reveals general rotation, although an additional significant component of random bulk motion is required by the high local velocity dispersion. The size scale of the typical gas disk is found to have a radius of ∼30 pc with a comparable vertical height. Within this radius the average gas mass is estimated to be ∼10 M⊙ based on a typical gas mass fraction of 10%, which suggests column densities of NH ∼ 5 × 10 23 cm. Extinction of the stellar continuum within this same region suggest lower column densities of NH ∼ 2 × 10 cm, indicating that the gas distribution on these scales is dominated by dense clumps. In half of the observed Seyfert galaxies this lower column density is still great enough to obscure the AGN at optical/infrared wavelengths. We conclude, based on the spatial distribution, kinematics, and column densities that the molecular gas observed is spatially mixed with the nuclear stellar population and is likely to be associated with the outer extent of any smaller-scale nuclear obscuring structure. Furthermore, we find that the velocity dispersion of the molecular gas is correlated with the star formation rate per unit area, suggesting a link between the two phenomena, and that the gas surface density follows known “Schmidt-Kennicutt” relations. The molecular/dusty structure on these scales may be dynamic since it is possible that the velocity dispersion of the gas, and hence the vertical disk height, is maintained by a short, massive inflow of material into the nuclear region and/or by intense, short-lived nuclear star formation. Subject headings: galaxies: active — galaxies: kinematics and dynamics — galaxies: nuclei — galaxies: Seyfert — infrared: galaxies