122062912
Measurement of single charged pion production in the charged-current interactions of neutrinos in a 1.3-GeV wide band beam
Single charged pion production in charged-current muon neutrino interactions with carbon is studied using data collected in the K2K long-baseline neutrino experiment. The mean energy of the incident muon neutrinos is 1.3 GeV. The data used in this analysis are mainly from a fully active scintillator detector, SciBar. The cross section for single {pi}{sup +} production in the resonance region (W<2 GeV/c{sup 2}) relative to the charged-current quasielastic cross section is found to be 0.734{sub -0.153}{sup +0.140}. The energy-dependent cross section ratio is also measured. The results are consistent with a previous experiment and the prediction of our model.
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.
54821283
Limit on B(s)0 oscillation using a jet charge method
A lower limit is set on the B_{s}^{0} meson oscillation parameter \Delta m_{s} using data collected from 1991 to 1994 by the ALEPH detector. Events with a high transverse momentum lepton and a reconstructed secondary vertex are used. The high transverse momentum leptons are produced mainly by b hadron decays, and the sign of the lepton indicates the particle/antiparticle final state in decays of neutral B mesons. The initial state is determined by a jet charge technique using both sides of the event. A maximum likelihood method is used to set a lower limit of \, \Delta m_{s}. The 95\% confidence level lower limit on \Delta m_s ranges between 5.2 and 6.5(\hbar/c^{2})~ps^{-1} when the fraction of b quarks from Z^0 decays that form B_{s}^{0} mesons is varied from 8\% to 16\%. Assuming that the B_{s}^{0} fraction is 12\%, the lower limit would be \Delta m_{s} 6.1(\hbar/c^{2})~ps^{-1} at 95\% confidence level. For x_s = \Delta m_s \, \tau_{B_s}, this limit also gives x_s 8.8 using the B_{s}^{0} lifetime of \tau_{B_s} = 1.55 \pm 0.11~ps and shifting the central value of \tau_{B_s} down by 1\sigma.
16654679
Indication of electron neutrino appearance from an accelerator-produced off-axis muon neutrino beam.
The T2K experiment observes indications of ν(μ) → ν(e) appearance in data accumulated with 1.43×10(20) protons on target. Six events pass all selection criteria at the far detector. In a three-flavor neutrino oscillation scenario with |Δm(23)(2)| = 2.4×10(-3)  eV(2), sin(2)2θ(23) = 1 and sin(2)2θ(13) = 0, the expected number of such events is 1.5±0.3(syst). Under this hypothesis, the probability to observe six or more candidate events is 7×10(-3), equivalent to 2.5σ significance. At 90% C.L., the data are consistent with 0.03(0.04) < sin(2)2θ(13) < 0.28(0.34) for δ(CP) = 0 and a normal (inverted) hierarchy.
125825698
Improved measurement of the $\bar{B}^0$ and $B^{-}$ meson lifetimes
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.
15076787
MOLECULAR GAS STREAMERS FEEDING AND OBSCURING THE ACTIVE NUCLEUS OF NGC 1068
We report the first direct observations of neutral, molecular gas streaming in the nucleus of NGC 1068 on scales of <30 pc using SINFONI near-infrared integral field spectroscopy. At a resolution of 0075, the flux map of 2.12 μm 1-0 S(1) molecular hydrogen emission around the nucleus in the central arcsec reveals two prominent linear structures leading to the active galactic nucleus from the north and south. The kinematics of the gas in these features are dominated by noncircular motions and indicate that material streams toward the nucleus on highly elliptical or parabolic trajectories, whose orientations are compatible with that of the disk plane of the galaxy. We interpret the data as evidence for fueling of gas to the central region. The radial transport rate from ~30 pc to a few parsecs from the nucleus is ~15 M ☉ yr–1. One of the infalling clouds lies directly in front of the central engine. We interpret it as a tidally disrupted streamer that forms the optically thick outer part of an amorphous clumpy molecular/dusty structure which contributes to the nuclear obscuration.
18042352
Near IR diffraction-limited integral-field SINFONI spectroscopy of the Circinus galaxy
Abstract Using the adaptive optics assisted near infrared integral field spectrometer SINFONI on the VLT, we have obtained observations of the Circinus galaxy on parsec scales. The morphologies of the H2 (1-0)S(1) 2.12 μm and Brγ 2.17 μm emission lines are only slightly different, but their velocity maps are similar and show a gradient along the major axis of the galaxy, consistent with rotation. Since Vrot/σ ≈ 1 suggests that random motions are also important, it is likely that the lines arise in a rotating spheroid or thickened disk around the AGN. Comparing the Brγ flux to the stellar continuum indicates that the star formation in this region began ∼108 yr ago. We also detect the [Si vi ] 1.96 μm, [Al ix ] 2.04 μm and [Ca viii ] 2.32 μm coronal lines. In all cases we observe a broad blue wing, indicating the presence of two or more components in the coronal line region. A correlation between the ionisation potential and the asymmetry of the profiles was found for these high excitation species.
12218218
A close look at star formation around active galactic nuclei
We analyze star formation in the nuclei of nine Seyfert galaxies at spatial resolutions down to 0.085'', corresponding to length scales of order 10 pc in most objects. Our data were taken mostly with the near-infrared adaptive optics integral field spectrograph SINFONI. The stellar light profiles typically have size scales of a few tens of parsecs. In two cases there is unambiguous kinematic evidence for stellar disks on these scales. In the nuclear regions there appear to have been recent, but no longer active, starbursts in the last 10-300 Myr. The stellar luminosity is less than a few percent of the AGN in the central 10 pc, whereas on kiloparsec scales the luminosities are comparable. The surface stellar luminosity density follows a similar trend in all the objects, increasing steadily at smaller radii up to ~1013 L☉ kpc−2 in the central few parsecs, where the mass surface density exceeds 104 M☉ pc−2. The intense starbursts were probably Eddington limited and hence inevitably short lived, implying that the starbursts occur in multiple short bursts. The data hint at a delay of 50-100 Myr between the onset of star formation and subsequent fueling of the black hole. We discuss whether this may be a consequence of the role that stellar ejecta could play in fueling the black hole. While a significant mass is ejected by OB winds and supernovae, their high velocity means that very little of it can be accreted. On the other hand, winds from AGB stars ultimately dominate the total mass loss, and they can also be accreted very efficiently because of their slow speeds.
119301588
The Impact of Nuclear Star Formation on Gas Inflow to AGN
Our adaptive optics observations of nearby AGN at spatial resolutions as small as 0.085arcsec show strong evidence for recent, but no longer active, nuclear star formation. We begin by describing observations that highlight two contrasting methods by which gas can flow into the central tens of parsecs. Gas accumulation in this region will inevitably lead to a starburst, and we discuss the evidence for such events. We then turn to the impact of stellar evolution on the further inflow of gas by combining a phenomenological approach with analytical modelling and hydrodynamic simulations. These complementary perspectives paint a picture in which all the processes are ultimately regulated by the mass accretion rate into the central hundred parsecs, and the ensuing starburst that occurs there. The resulting supernovae delay accretion by generating a starburst wind, which leaves behind a clumpy interstellar medium. This provides an ideal environment for slower stellar outflows to accrete inwards and form a dense turbulent disk on scales of a few parsecs. Such a scenario may resolve the discrepancy between the larger scale structure seen with adaptive optics and the small scale structure seen with VLTI.
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.