Cosmic Events Research Articles

Metallic microspheres and microparticles in lower Cenomanian sediments of the Crimea: Evidence for the cosmic dust event

Recently, significant attention has been paid to sedimentary rocks enriched in cosmic matter. Such interest in similar objects is connected with study of the problem concerning the influence of cosmic phe� nomena on the Earth and its biosphere: scientists want to know to what degree this influence may be cata� strophic. These objects also represent carriers of infor� mation on cosmic matter (its morphology, chemical composition), which has been falling on the Earth during its entire existence. The study of cosmic parti� cles allows atmospheric processes, owing to which compositionally different particles acquire different morphological features, to be better understood. Recently, some researchers have seen in such objects a tool for superaccurate stratigraphic correlations [1]. Previous studies revealed that the distribution of cosmic matter in sedimentary sections is extremely irregular at different stratigraphic levels [2, 3]. This communication is dedicated to one such for� merly unknown level. Materials collected and ana� lyzed during field works of 2008 served as the basis for this work. Thorough study of the upper Albian–lower Conia� cian section (over 200 samples were taken in total) outcropping on the southern slope of Mount Kremen� naya in the Bakhchisarai area of the Crimea ( N 44°046'589'', E 033°058'755'', h = 327 ± 7 m) revealed abundant metallic microspheres and microparticles of cosmic origin in the bed of basal Cenomanian greenish gray incoherent silty marl together with the typical low� ermost Cenomanian planktonic (Globigerinelloides ultra� micrus, Clavihedbergella (?) simplex, Thalmanninella greenhornensis (=brotzeni), T. appenninica, T. gandolfi) and benthic (Tritaxia pyramidata, Ataxophragmium byk� ovae) belonging to the Thalmanninella greenhornensis (=Rotalipora brotzeni) Zone. In the course of the study of these foraminifers in residues, it appeared that both foraminiferal tests and particles of preserved rocks are highly magnetic. This stimulated further more thorough examination of host rocks.

Commissioning of the ATLAS reconstruction software with first data

Looking towards first LHC collisions, the ATLAS detector is being commissioned using all types of physics data available: cosmic rays and events produced during a few days of LHC single beam operations. In addition to putting in place the trigger and data acquisition chains, commissioning of the full software chain is a main goal. This is interesting not only to ensure that the reconstruction, monitoring and simulation chains are ready to deal with LHC physics data, but also to understand the detector performance in view of achieving the physics requirements. The status of the integration of the complete software chain will be presented as well as the data analysis results.

The CMS tracker calibration workflow: Experience with cosmic ray data

During the second part of 2008 a CMS commissioning was performed with the acquisition of cosmic events in global runs. Cosmic rays detected in the muon chambers were used to trigger the readout of all CMS subdetectors in the general data acquisition system. A total of about 300M of tracks were collected by the CMS Muon Chambers with a 3.8T magnetic field produced by the CMS superconducting solenoid, 6M of which pointing to the tracker region and reconstructed by the Si-Strip Tracker (SST) detectors. Other 1M of cosmic tracks were collected with the magnetic field off. Using the cosmic data available it was possible to validate the performances of the CMS tracker calibration workflows. In this paper the adopted calibration workflow is described. In particular, the three main calibration workflows requested for the low level reconstruction of the SST, i.e. gain calibration, Lorentz angle calibration and bad components identification, are described. The results obtained using cosmic tracks for these three calibration workflows are also presented.

Design and construction of INGRID neutrino beam monitor for T2K neutrino experiment

The INGRID(Interactive Neutrino GRID) detector is designed to measure the neutrino beam direction with a precision better than 1mrad for T2K experiment. INGRID consists of 16 modules and placed around the beam center at 280m downstream of the proton beam target. The module is a sandwich of iron targets and scintillator tracking planes which consist of X–Y layers. We have constructed all scintillator tracking planes and measured light yield of all scintillators. Currently we install 1st module into the detector hall and cosmic events are observed. INGRID is ready for 1st neutrino event from April 2009.

Performance of the CMS Level-1 trigger during commissioning with cosmic ray muons and LHC beams

The CMS Level-1 trigger was used to select cosmic ray muons and LHC beam events during data-taking runs in 2008, and to estimate the level of detector noise. This paper describes the trigger components used, the algorithms that were executed, and the trigger synchronisation. Using data from extended cosmic ray runs, the muon, electron/photon, and jet triggers have been validated, and their performance evaluated. Efficiencies were found to be high, resolutions were found to be good, and rates as expected.

Precise mapping of the magnetic field in the CMS barrel yoke using cosmic rays

The CMS detector is designed around a large 4 T superconducting solenoid, enclosed in a 12 000-tonne steel return yoke. A detailed map of the magnetic field is required for the accurate simulation and reconstruction of physics events in the CMS detector, not only in the inner tracking region inside the solenoid but also in the large and complex structure of the steel yoke, which is instrumented with muon chambers. Using a large sample of cosmic muon events collected by CMS in 2008, the field in the steel of the barrel yoke has been determined with a precision of 3 to 8% depending on the location.

BESIII barrel time-of-flight (TOF) calibration using cosmic ray data

The principle of the method for the BESIII TOF calibration using cosmic ray data without magnetic field are reported in this paper. After applying calibration constants, the single-end readout time resolution could reach about 150 ps, and the time resolution for one layer is achieved to be about 110 ps. The paper also described the extraction scheme for the event start time of cosmic events.

The Murray Springs Clovis site, Pleistocene extinction, and the question of extraterrestrial impact

Some of the evidence for the recent hypothesis of an extraterrestrial impact that caused late Pleistocene megafaunal extinctions [Firestone et al. (2007) Proc Natl Acad Sci USA 104:16016-16021] was based upon samples collected at Murray Springs, a Clovis archaeological site in southeastern Arizona. Here we describe sampling and analyses of magnetic separates from within, above, and below the lower Younger Dryas boundary (LYDB) black mat at Murray Springs, as well as radiation measurements from the LYDB at Murray Springs and two other well-stratified Clovis sites. The main magnetic fraction at Murray Springs is maghemite. Magnetic microspherules have terrestrial origins but also occur as cosmic dust particles. We failed to find iridium or radiation anomalies. The evidence for massive biomass burning at Murray Springs is addressed and found to be lacking. We could not substantiate some of the claims by Firestone and others, but our findings do not preclude a terminal Pleistocene cosmic event.

A LARGER ESTIMATE OF THE ENTROPY OF THE UNIVERSE

Using recent measurements of the supermassive black hole (SMBH) mass function, we find that SMBHs are the largest contributor to the entropy of the observable universe, contributing at least an order of magnitude more entropy than previously estimated. The total entropy of the observable universe is correspondingly higher, and is S_obs = 3.1+3.0-1.7x10^104 k. We calculate the entropy of the current cosmic event horizon to be S_CEH = 2.6+-0.3x10^122 k, dwarfing the entropy of its interior, S_CEHint = 1.2+1.1-0.7x10^103 k. We make the first tentative estimate of the entropy of weakly interacting massive particle dark matter within the observable universe, S_dm = 10^87-10^89 k. We highlight several caveats pertaining to these estimates and make recommendations for future work.

Discovery of a nanodiamond-rich layer in the Greenland ice sheet

AbstractWe report the discovery in the Greenland ice sheet of a discrete layer of free nanodiamonds (NDs) in very high abundances, implying most likely either an unprecedented influx of extraterrestrial (ET) material or a cosmic impact event that occurred after the last glacial episode. From that layer, we extracted n-diamonds and hexagonal diamonds (lonsdaleite), an accepted ET impact indicator, at abundances of up to about 5×106 times background levels in adjacent younger and older ice. The NDs in the concentrated layer are rounded, suggesting they most likely formed during a cosmic impact through some process similar to carbon-vapor deposition or high-explosive detonation. This morphology has not been reported previously in cosmic material, but has been observed in terrestrial impact material. This is the first highly enriched, discrete layer of NDs observed in glacial ice anywhere, and its presence indicates that ice caps are important archives of ET events of varying magnitudes. Using a preliminary ice chronology based on oxygen isotopes and dust stratigraphy, the ND-rich layer appears to be coeval with ND abundance peaks reported at numerous North American sites in a sedimentary layer, the Younger Dryas boundary layer (YDB), dating to 12.9 ± 0.1 ka. However, more investigation is needed to confirm this association.

Cosmic ray interaction event generator SIBYLL 2.1

The cosmic ray interaction event generator Sibyll is widely used in extensive air shower simulations. We describe in detail the properties of Sibyll 2.1 and the differences with the original version 1.7. The major structural improvements are the possibility to have multiple soft interactions, introduction of new parton density functions, and an improved treatment of diffraction. Sibyll 2.1 gives better agreement with fixed target and collider data, especially for the inelastic cross sections and multiplicities of secondary particles. Shortcomings and suggestions for future improvements are also discussed.

JOINT SEARCHES BETWEEN GRAVITATIONAL-WAVE INTERFEROMETERS AND HIGH-ENERGY NEUTRINO TELESCOPES: SCIENCE REACH AND ANALYSIS STRATEGIES

Many of the astrophysical sources and violent phenomena observed in our Universe are potential emitters of gravitational waves (GWs) and high-energy neutrinos (HENs). A network of GW detectors such as LIGO and Virgo can determine the direction/time of GW bursts while the IceCube and ANTARES neutrino telescopes can also provide accurate directional information for HEN events. Requiring the consistency between both, totally independent, detection channels shall enable new searches for cosmic events arriving from potential common sources, of which many extra-galactic objects.

Detection of atmospheric muons with ALICE detectors

The calibration, alignment and commissioning of most of the ALICE (A Large Ion Collider Experiment at the CERN LHC) detectors have required a large amount of cosmic events during 2008. In particular two types of cosmic triggers have been implemented to record the atmospheric muons passing through ALICE. The first trigger, called ACORDE trigger, is performed by 60 scintillators located on the top of three sides of the large L3 magnet surrounding the central detectors, and selects atmospheric muons. The Silicon Pixel Detector (SPD) installed on the first two layers of the Inner Tracking System (ITS) gives the second trigger, called SPD trigger. This trigger selects mainly events with a single atmospheric muon crossing the SPD. Some particular events, in which the atmospheric muon interacts with the iron of the L3 magnet and creates a shower of particles crossing the SPD, are also selected. In this work the reconstruction of events with these two triggers will be presented. In particular, the performance of the ACORDE detector will be discussed by the analysis of multi-muon events. Some physical distributions are also shown.

Shock-synthesized hexagonal diamonds in Younger Dryas boundary sediments

The long-standing controversy regarding the late Pleistocene megafaunal extinctions in North America has been invigorated by a hypothesis implicating a cosmic impact at the Allerød-Younger Dryas boundary or YDB (approximately 12,900 +/- 100 cal BP or 10,900 +/- 100 (14)C years). Abrupt ecosystem disruption caused by this event may have triggered the megafaunal extinctions, along with reductions in other animal populations, including humans. The hypothesis remains controversial due to absence of shocked minerals, tektites, and impact craters. Here, we report the presence of shock-synthesized hexagonal nanodiamonds (lonsdaleite) in YDB sediments dating to approximately 12,950 +/- 50 cal BP at Arlington Canyon, Santa Rosa Island, California. Lonsdaleite is known on Earth only in meteorites and impact craters, and its presence strongly supports a cosmic impact event, further strengthened by its co-occurrence with other nanometer-sized diamond polymorphs (n-diamonds and cubics). These shock-synthesized diamonds are also associated with proxies indicating major biomass burning (charcoal, carbon spherules, and soot). This biomass burning at the Younger Dryas (YD) onset is regional in extent, based on evidence from adjacent Santa Barbara Basin and coeval with broader continent-wide biomass burning. Biomass burning also coincides with abrupt sediment mass wasting and ecological disruption and the last known occurrence of pygmy mammoths (Mammuthus exilis) on the Channel Islands, correlating with broader animal extinctions throughout North America. The only previously known co-occurrence of nanodiamonds, soot, and extinction is the Cretaceous-Tertiary (K/T) impact layer. These data are consistent with abrupt ecosystem change and megafaunal extinction possibly triggered by a cosmic impact over North America at approximately 12,900 +/- 100 cal BP.

Interhemispheric observations of impulsive nitrate enhancements associated with the four large ground-level solar cosmic ray events (1940–1950)

We present a compelling similarity of impulsive nitrate enhancements observed in polar ice from the northern and southern hemispheres. This analysis concentrates on the period 1940–1950, during which time the first four recorded solar cosmic ray ground-level enhancements (GLEs) occurred. GLEs are strong solar proton events. We show that large and sudden enhancements in the nitrate records from both hemispheres were observed within weeks following the recorded solar cosmic ray ground-level event. The observation of impulsive nitrate enhancements simultaneously in both hemispheres shortly after a large fluence solar proton event is strong evidence in support of a causal connection and argues strongly for rapid transport of atmospheric nitrates generated through the polar atmosphere by energetic solar proton events.

Alignment of the CMS silicon strip tracker during stand-alone commissioning

The results of the CMS tracker alignment analysis are presented using the data from cosmic tracks, optical survey information, and the laser alignment system at the Tracker Integration Facility at CERN. During several months of operation in the spring and summer of 2007, about five million cosmic track events were collected with a partially active CMS Tracker. This allowed us to perform first alignment of the active silicon modules with the cosmic tracks using three different statistical approaches; validate the survey and laser alignment system performance; and test the stability of Tracker structures under various stresses and temperatures ranging from +15 °C to −15 °C. Comparison with simulation shows that the achieved alignment precision in the barrel part of the tracker leads to residual distributions similar to those obtained with a random misalignment of 50 (80) μm RMS in the outer (inner) part of the barrel.

Commissioning of the ATLAS detector with cosmic rays and first LHC beams

Looking towards first LHC collisions, the ATLAS detector is being commissioned using all types of physics data available: cosmic rays and events produced during a few days of LHC single beam operations. In addition to putting in place the trigger and data acquisition chains, commissioning of the full software chain is a main goal. This is interesting not only to ensure that the reconstruction, monitoring and simulation chains are ready to deal with LHC physics data, but also to understand the detector performance in view of achieving the physics requirements. The status of the integration of the complete software chain will be presented as well as the data analysis results.

Cataclysmic cosmic events and how to observe them

Cataclysmic cosmic events and how to observe them

Measuring Cosmic Elements with Gamma-Ray Telescopes

AbstractGamma-ray telescopes are capable of measuring radioactive trace isotopes from cosmic nucleosynthesis events. Such measurements address new isotope production rather directly for a few key isotopes such as 44Ti, 26Al, 60Fe, and 56Ni, as well as positrons from the β+-decay variety. Experiments of the past decades have now established an astronomy with γ-ray lines, which is an important part of the study of nucleosynthesis environments in cosmic sources. For massive stars and supernovae, important constraints have been set: Co isotope decays in SN1987A directly demonstrated the synthesis of new isotopes in core-collapse supernovae, 44Ti from the 340-year-old Cas A supernova supports the concept of α-rich freeze-out, but results in interesting puzzles pursued by theoretical studies and future experiments. 26Al and 60Fe has been measured from superimposed nucleosynthesis within our Galaxy, and sets constraints on massive-star interior structure through its intensity ratio of ∼15%. The 26Al γ-ray line is now seen to trace current star formation and even the kinematics of interstellar medium throughout the Galaxy. Positron annihilation emission from nucleosynthesis throughout the plane of our Galaxy appears to be mainly from 26Al and other supernova radioactivity, but the striking brightness of the Galaxy's bulge region in positron annihilation γ-rays presents a puzzle involving several astrophysics issues beyond nuclear astrophysics. This paper focuses mainly on a discussion of 26Al and 60Fe from massive-star nucleosynthesis.

Anaxagoras as Probability Theorist

A re-examination of the textual evidence supports the idea that Anaxagoras was in fact the inventor of the conception of probability as ‘the chance of an event’s occurring’. His cosmogony, therefore, does not clearly violate the principle of sufficient reason because the initial cosmic event was in effect bound, sooner or later, to happen to occur.