Search results for "PARTICLES"
showing 10 items of 8085 documents
TeV gamma-ray survey of the Northern sky using the ARGO-YBJ detector
2013
The ARGO-YBJ detector is an extensive air shower array that has been used to monitor the northern $\gamma$-ray sky at energies above 0.3 TeV from 2007 November to 2013 January. In this paper, we present the results of a sky survey in the declination band from $-10^{\circ}$ to $70^{\circ}$, using data recorded over the past five years. With an integrated sensitivity ranging from 0.24 to $\sim$1 Crab units depending on the declination, six sources have been detected with a statistical significance greater than 5 standard deviations. Several excesses are also reported as potential $\gamma$-ray emitters. The features of each source are presented and discussed. Additionally, $95\%$ confidence le…
Towards asteroseismology of core-collapse supernovae with gravitational-wave observations – I. Cowling approximation
2017
Gravitational waves from core-collapse supernovae are produced by the excitation of different oscillation modes in the protoneutron star (PNS) and its surroundings, including the shock. In this work we study the relationship between the post-bounce oscillation spectrum of the PNS–shock system and the characteristic frequencies observed in gravitational-wave signals from core-collapse simulations. This is a fundamental first step in order to develop a procedure to infer astrophysical parameters of the PNS formed in core-collapse supernovae. Our method combines information from the oscillation spectrum of the PNS, obtained through linear perturbation analysis in general relativity of a backgr…
Search for microscopic black holes in a like-sign dimuon final state using large track multiplicity with the ATLAS detector
2013
A search is presented for microscopic black holes in a like-sign dimuon final state in proton-proton collisions at √s= 8 TeV. The data were collected with the ATLAS detector at the Large Hadron Collider in 2012 and correspond to an integrated luminosity of 20.3 fb-1. Using a high track multiplicity requirement, 0.6±0.2 background events from Standard Model processes are predicted and none observed. This result is interpreted in the context of low-scale gravity models and 95% CL lower limits on microscopic black hole masses are set for different model assumptions.
Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC
2011
Measurements are presented from proton–proton collisions at centre-of-mass energies of \sqrt{s} = 0.9 , 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared…
ATLAS measurements of the properties of jets for boosted particle searches
2012
Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of √s=7 TeV. The data correspond to an integrated luminosity of 35 pb−1 and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-kt algorithm with distance parameters R=0.6 and 1.0, with transverse momentum pT>300 GeV and pseudorapidity |η|<2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describ…
Search for excited electrons and muons in root s=8 TeV proton-proton collisions with the ATLAS detector
2013
The ATLAS detector at the Large Hadron Collider is used to search for excited electrons and excited muons in the channel pp → ℓℓ* → ℓℓγ, assuming that excited leptons are produced via contact interactions. The analysis is based on 13 fb[superscript −1] of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95% credibility level on the cross section times branching ratio as a function of the excited-lepton mass m[subscript ℓ*]. For m[subscript ℓ*] ≥ 0.8 TeV, the respective upper limits on σB(ℓ* → ℓγ) are 0.75 and 0.90 fb for the e* and μ* searches. Limits on σB are converted into lower bounds on the compositeness scale Λ. In …
Search for strong gravity signatures in same-sign dimuon final states using the ATLAS detector at the LHC
2012
A search for microscopic black holes has been performed in a same-sign dimuon final state using 1.3 fb[superscript −1] of proton–proton collision data collected with the ATLAS detector at a centre of mass energy of 7 TeV at the CERN Large Hadron Collider. The data are found to be consistent with the expectation from the Standard Model and the results are used to derive exclusion contours in the context of a low scale gravity model.
Measurement of the distributions of event-by-event flow harmonics in lead-lead collisions at = 2.76 TeV with the ATLAS detector at the LHC
2013
We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWF and FWF, 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; EPLANET, ERC and NSRF, European Union; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, DFG, HGF, MPG and AvH Foundation, Germany; GSRT and NSRF, Greece; ISF, MINERVA, GIF, DIP and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; BRF and RCN, Norway; MNiSW, Poland; GRICES and FCT, Portu…
Vibronic structures in the visible luminescence of silica nanoparticles
2014
Time resolved photoluminescence investigation in air and in vacuum atmosphere of the visible luminescence related to silica surface defects is here reported. Two contributions can be singled out: one, observed both in air and in vacuum, is the well-known blue band, peaked around 2.8 eV decaying in ∼5 ns; the other, only observed in vacuum, is a structured emission in the violet range characterized by two vibronic progressions spaced 1370 cm−1 and 360 cm−1 decaying in ∼100 ns. In contrast with previous attribution, the well distinguishable spectroscopic properties together with the observation of the effects induced by the interaction with nitrogen allow to state that the emission bands orig…
Microphysical Properties of Ice Crystal Precipitation and Surface-Generated Ice Crystals in a High Alpine Environment in Switzerland
2017
AbstractDuring the Cloud and Aerosol Characterization Experiment (CLACE) 2013 field campaign at the High Altitude Research Station Jungfraujoch, Switzerland, optically thin pure ice clouds and ice crystal precipitation were measured using holographic and other in situ particle instruments. For cloud particles, particle images, positions in space, concentrations, and size distributions were obtained, allowing one to extract size distributions classified by ice crystal habit. Small ice crystals occurring under conditions with a vertically thin cloud layer above and a stratocumulus layer approximately 1 km below exhibit similar properties in size and crystal habits as Antarctic/Arctic diamond …