arXiv subjects

K. Filimonov

Publications and source records attributed to K. Filimonov.

179 records · Page 10Linked to original sources

arXiv2010

Measurement of the atmospheric neutrino energy spectrum from 100 GeV to 400 TeV with IceCube

A measurement of the atmospheric muon neutrino energy spectrum from 100 GeV to 400 TeV was performed using a data sample of about 18,000 up-going atmospheric muon neutrino events in IceCube. Boosted decision trees were used for event selection to reject mis-reconstructed atmospheric muons and obtain a sample of up-going muon neutrino events. Background contamination in the final event sample is less than one percent. This is the first measurement of atmospheric neutrinos up to 400 TeV, and is fundamental to understanding the impact of this neutrino background on astrophysical neutrino observations with IceCube. The measured spectrum is consistent with predictions for the atmospheric muon neutrino plus muon antineutrino flux.

astro-ph.HE↗

arXiv2010

Search for a Lorentz-violating sidereal signal with atmospheric neutrinos in IceCube

A search for sidereal modulation in the flux of atmospheric muon neutrinos in IceCube was performed. Such a signal could be an indication of Lorentz-violating physics. Neutrino oscillation models, derivable from extensions to the Standard Model, allow for neutrino oscillations that depend on the neutrino's direction of propagation. No such direction-dependent variation was found. A discrete Fourier transform method was used to constrain the Lorentz and CPT-violating coefficients in one of these models. Due to the unique high energy reach of IceCube, it was possible to improve constraints on certain Lorentz-violating oscillations by three orders of magnitude with respect to limits set by other experiments.

astro-ph.HE↗

arXiv2010

The first search for extremely-high energy cosmogenic neutrinos with the IceCube Neutrino Observatory

We report on the results of the search for extremely-high energy (EHE) neutrinos with energies above $10^7$ GeV obtained with the partially ($\sim$30%) constructed IceCube in 2007. From the absence of signal events in the sample of 242.1 days of effective livetime, we derive a 90% C.L. model independent differential upper limit based on the number of signal events per energy decade at $E^2 ϕ_{ν_e+ν_μ+ν_τ}\simeq 1.4 \times 10^{-6}$ GeV cm$^{-2}$ sec$^{-1}$ sr$^{-1}$ for neutrinos in the energy range from $3\times10^7$ to $3\times10^9$ GeV.

astro-ph.CO↗

arXiv2010

IceCube Collaboration Contributions to the 2009 International Cosmic Ray Conference

astro-ph.HE↗

arXiv2010

Calibration and Characterization of the IceCube Photomultiplier Tube

Over 5,000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-inch diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts.

astro-ph.IM↗

arXiv2008

Azimuthal dependence of pion source radii in Pb+Au collisions at 158 A GeV

We present results of a two-pion correlation analysis performed with the Au+Pb collision data collected by the upgraded CERES experiment in the fall of 2000. The analysis was done in bins of the reaction centrality and the pion azimuthal emission angle with respect to the reaction plane. The pion source, deduced from the data, is slightly elongated in the direction perpendicular to the reaction plane, similarly as was observed at the AGS and at RHIC.

nucl-ex↗

arXiv2006

Strange baryon resonance production in $\sqrt{s_{NN}} = 200$ GeV $p+p$ and $Au+Au$ collisions

We report the measurements of $Σ(1385)$ and $Λ(1520)$ production in $p+p$ and $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV from the STAR collaboration. The yields and the $p_{T}$ spectra are presented and discussed in terms of chemical and thermal freeze-out conditions and compared to model predictions. Thermal and microscopic models do not adequately describe the yields of all the resonances produced in central $Au+Au$ collisions. Our results indicate that there may be a time-span between chemical and thermal freeze-out during which elastic hadronic interactions occur.

nucl-ex↗

arXiv2004

Jets as a Probe of Dense Matter at RHIC

Jet quenching in the matter created in high energy nucleus-nucleus collisions provides a tomographic tool to probe the medium properties. Recent experimental results on jet production at the Relativistic Heavy-Ion Collider (RHIC) are reviewed. Jet properties in p+p and d+Au collisions have been measured, establishing the baseline for studying jet modification in heavy-ion collisions. Current progress on detailed studies of high transverse momentum production in Au+Au collisions is discussed, with an emphasis on dihadron correlation measurements.

nucl-ex↗

arXiv2003

Elliptic flow contribution to two-particle correlations at different orientations to the reaction plane

Collective anisotropic particle flow, a general phenomenon present in relativistic heavy-ion collisions, can be separated from direct particle-particle correlations of different physics origin by virtue of its specific azimuthal pattern. We provide expressions for flow-induced two-particle azimuthal correlations, if one of the particles is detected under fixed directions with respect to the reaction plane. We consider an ideal case when the reaction plane angle is exactly known, as well as present the general expressions in case of finite event-plane resolution. We foresee applications for the study of generic two-particle correlations at large transverse momentum originating from jet fragmentation.

nucl-ex↗

arXiv2003

The Mini-Jet Scale and Energy Loss at RHIC in the HIJING and RQMD Models

The original default mini-jet scale p_0=2 GeV/c and energy loss, dE/dx=2 GeV/fm in HIJING lead to a too rapid growth of the multiplicity with energy. RQMD model without mini-jet leads on the other hand to a too slowly increasing multiplicity with energy. We show that a slight increase of p_0 from the default 2.0 GeV/c at sqrt(s)=130A GeV to 2.2 GeV/c at sqrt{s}=200A GeV is sufficient to account for the bulk observables. Jet quenching of pi^0 above p_T>4 GeV/c at 200A GeV is found to be well reproduced in central Au+Au by the original HIJING default prediction. However, the effective surface emission in the HIJING model formulation of energy loss over-predicts the quenching in more peripheral collisions. Neither HIJING nor HIJING/B{bar}B can account for the observed anomalous excess of moderate p_T<4 GeV/c baryons. The agreement of RQMD with data in this p_T region is shown to be fortuitous because, without mini-jets, it fails to reproduce the p+p spectrum.

nucl-th↗

arXiv2003

Overview of results from the STAR experiment at RHIC

The Relativistic Heavy-Ion Collider (RHIC) provides Au+Au collisions at energies up to \sqrtsNN=200 GeV. STAR experiment was designed and constructed to investigate the behavior of strongly interacting matter at high energy density. An overview of some of the recent results from the STAR collaboration is given.

hep-ex↗

arXiv2002

High $p_T$ hadrons in Au+Au collisions at RHIC

High pT hadrons produced in ultra-relativistic heavy-ion collisions at RHIC probe nuclear matter at extreme conditions of high energy density. Experimental measurements in Au+Au collisions at \sqrtsNN=130, 200 GeV establish the existence of strong medium effects on hadron production well into the perturbative regime.

hep-ex↗

arXiv2002

Azimuthal Anisotropy of Charged and Identified High $p_T$ Hadrons in Au+Au Collisions at RHIC

We report new results on $v_2(p_T)$ for Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV for charged hadrons, pions, kaons, (anti)protons, $K^0_s$, and $Λ$. The analysis is extended to $p_T=12$ GeV/c for charged hadrons and $p_T=4$ GeV/c for identified particles. A comparison of the azimuthal anisotropy of charged hadrons measured at \sqrtsNN=130 and 200 GeV is presented. The $p_T$-dependence of baryon versus meson elliptic flow is discussed.

nucl-ex↗

arXiv2001

New Results on Pb-Au Collisions at 40 AGeV from the CERES/NA45 Experiment

In 1999 the CERES/NA45 ran at the CERN SPS with a beam energy of 40 GeV/nucleon. The data set comprises about 8.7 millions Pb-Au events with a trigger selection corresponding to approximately the most central 30% of the geometrical cross section. Results on low-mass electron pair analysis are presented. The upgrade of the experimental setup with the radial drift TPC has allowed to enhance hadron physics capabilities of the experiment. New results on hadron spectra (including Lambda) and flow are presented.

nucl-ex↗

arXiv2000

Directed flow of antiprotons in Au+Au collisions at AGS

Directed flow of antiprotons is studied in Au+Au collisions at a beam momentum of 11.5A GeV/c. It is shown that antiproton directed flow is anti-correlated to proton flow. The measured transverse momentum dependence of the antiproton flow is compared with predictions of the RQMD event generator.

nucl-ex↗

arXiv1999

Recent results from E877 for Au+Au collisions at AGS energy

The E877 experiment was dedicated to the study of hadron distributions in Au+Au collisions at the AGS. Here, we will mainly present results from the analysis of the data obtained from the last data taking run, which took place in the fall of 1995 and recorded 46 millions Au+Au events at 11.5 AGeV/c. The improved experimental apparatus and large statistics allowed to extend our previous measurements of particle flow to K^+, K^-, pbar and lambda. We will also report our latest results on two-particle correlations of like and unlike particles, as well as the measurements of double differential multiplicities of lambda-hyperons.

nucl-ex↗

arXiv1998

Directed Flow of Light Nuclei in Au+Au Collisions at AGS Energies

Directed flow of deuterons, tritons, $^3$He, and $^4$He is studied in Au+Au collisions at a beam momentum of about 10.8 $A$ GeV/c. Flow of all particles is analyzed as a function of transverse momentum for different centralities of the collision. The directed flow signal, $v_1(p_t)$, is found to increase with particle mass. This mass dependence is strongest in the projectile rapidity region.

nucl-ex↗