Search results for "Luminosity"
showing 10 items of 560 documents
Search for decays of stopped, long-lived particles from 7 TeV pp collisions with the ATLAS detector
2012
New metastable massive particles with electric and colour charge are features of many theories beyond the Standard Model. A search is performed for long-lived gluino-based R-hadrons with the ATLAS detector at the LHC using a data sample corresponding to an integrated luminosity of 31 pb[superscript −1]. We search for evidence of particles that have come to rest in the ATLAS detector and decay at some later time during the periods in the LHC bunch structure without proton–proton collisions. No significant deviations from the expected backgrounds are observed, and a cross-section limit is set. It can be interpreted as excluding gluino-based R-hadrons with masses less than 341 GeV at the 95 % …
Electron performance measurements with the ATLAS detector using the 2010 LHC proton-proton collision data
2012
Acknowledgements We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF, DNSRC and Lundbeck Foundation, Denmark; ARTEMIS, European Union; IN2P3-CNRS, CEA-DSM/IRFU, France; GNAS, Georgia; BMBF, DFG, HGF, MPG and AvH Foundation, Germany; GSRT, Greece; ISF, MINERVA, GIF, DIP and Benoziyo…
Radio source evolution
2016
Baldwin (1982) wrote that “the distribution of sources in the radio luminosity, P, overall physical size, D, diagram” could be considered as “the radio astronomer's H-R diagram”. However, unlike the case of stars, not only the intrinsic properties of the jets, but also those of the host galaxy and the intergalactic medium are relevant to explain the evolutionary tracks of radio radio sources. In this contribution I review the current status of our understanding of the evolution of radio sources from a theoretical and numerical perspective, using the P -D diagram as a framework. An excess of compact (linear size ≤10 kpc) sources could be explained by low-power jets being decelerated within t…
Evidence for the singly Cabibbo suppressed decayΛc+→pηand search forΛc+→pπ0
2017
We study the singly Cabibbo suppressed decays Lambda(+)(c) -> p eta and Lambda(+)(c) -> p pi(0) using Lambda(+)(c)(Lambda) over bar (-)(c) pairs produced by e(+)e(-) collisions at a center-of-mass energy of root s = 4.6 GeV. The data sample was collected by the BESIII detector at the BEPCII collider and corresponds to an integrated luminosity of 567 pb(-1). We find the first evidence for the decay Lambda(+)(c) -> p eta with a statistical significance of 4.2 sigma and measure its branching fraction to be B(Lambda(+)(c) -> p eta) = (1.24 +/- 0.28(stat) +/- 0.10(sys)) x 10(-3). No significant Lambda(+)(c) -> p pi(0) signal is observed. We set an upper limit on its branching fraction B(Lambda(+…
Measurement of the Absolute Branching Fraction of the Inclusive Decay Λc+ → Λ+X
2018
Physical review letters 121(6), 062003 (2018). doi:10.1103/PhysRevLett.121.062003
AGingaObservation of the X‐Ray Pulsar 4U 0352+30
1996
4U 0352 + 30 (X Persei) is a low-luminosity binary X-ray pulsar with a pulse period of 835 s. We present timing and spectral analysis of a Ginga observation of X Persei from 1990 January 26 to January 29. The observation shows the peculiar spectral behavior of X Persei: the pulse-averaged hardness ratio exhibits a sharp hardening episode at phase minimum of the light curve. In order to explain the shape of the observed hardness ratio, we discuss the possible geometry of the emitting region. Simple models of fan emission from a hollow accretion column can reproduce the qualitative features of the observed light curve and hardness ratio.
On the Optical Counterpart of SAX J1808.4-3658 during Quiescence: Evidence for an Active Radio Pulsar?
2003
The optical counterpart of the binary millisecond X-ray pulsar SAX J1808.4-3658 during quiescence was detected at V =21.5 mag, inconsistent with intrinsic emission from the faint companion star. We propose that the optical emission from this system during quiescence is due to the reprocessing by the companion star and a remnant accretion disk of the rotational energy released by the fast spinning neutron star, switched on, as magneto-dipole rotator (radio pulsar), during quiescence. In this scenario the companion behaves as a bolometer, reprocessing in optical the intercepted fraction of the power emitted by the pulsar. This reprocessed fraction depends only on known binary parameters. Thus…
ESO-Hα 574 and Par-Lup 3-4 jets: Exploring the spectral, kinematical, and physical properties
2014
In this paper a comprehensive analysis of VLT / X-Shooter observations of two jet systems, namely ESO-H$\alpha$ 574 a K8 classical T Tauri star and Par-Lup 3-4 a very low mass (0.13~\Msun) M5 star, is presented. Both stars are known to have near-edge on accretion disks. A summary of these first X-shooter observations of jets was given in a 2011 letter. The new results outlined here include flux tables of identified emission lines, information on the morphology, kinematics and physical conditions of both jets and, updated estimates of $\dot{M}_{out}$ / $\dot{M}_{acc}$. Asymmetries in the \eso flow are investigated while the \para jet is much more symmetric. The density, temperature, and ther…
X-ray emission from dense plasma in classical T Tauri stars: hydrodynamic modeling of the accretion shock
2008
Context: High spectral resolution X-ray observations of classical T Tauri stars (CTTSs) demonstrate the presence of plasma at temperature T~2-3×10^6 K and density n_e~10^11-10^13 cm^-3, which are unobserved in non-accreting stars. Stationary models suggest that this emission is due to shock-heated accreting material, but do not allow us to analyze the stability of the material and its position in the stellar atmosphere. Aims: We investigate the dynamics and stability of shock-heated accreting material in classical T Tauri stars and the role of the stellar chromosphere in determining the position and thickness of the shocked region. Methods: We perform one-dimensional hydrodynamic simulation…
MALTA: a CMOS pixel sensor with asynchronous readout for the ATLAS High-Luminosity upgrade
2018
Radiation hard silicon sensors are required for the upgrade of the ATLAS tracking detector for the High- Luminosity Large Hadron Collider (HL-LHC) at CERN. A process modification in a standard 0.18 μm CMOS imaging technology combines small, low-capacitance electrodes (∼2 fF for the sensor) with a fully depleted active sensor volume. This results in a radiation hardness promising to meet the requirements of the ATLAS ITk outer pixel layers (1.5 × 1015 neq /cm2 ), and allows to achieve a high signal-to-noise ratio and fast signal response, as required by the HL-LHC 25 ns bunch crossing structure. The radiation hardness of the charge collection to Non-Ionizing Energy Loss (NIEL) has been previ…