A
bstract
We consider a spin-1 resonance produced with an arbitrary spectrum of velocities and decaying into a pair of massless leptons, and we study the probability density function of the energy of ...the leptons in the laboratory frame. A special case is represented by the production of
W
bosons in proton-proton collisions, for which the energy of the charged lepton from the decaying
W
can be measured with sufficient accuracy for a high-precision measurement of
M
W
. We find that half of the resonance mass is a special value of the lepton energy, since the probability density function at this point is in general not analytic for a narrow-width resonance. In particular, the higher-order derivatives of the density function are likely to develop singularities, such as cusps or poles. A finite width of the resonance restores the regularity, for example by smearing cusps and poles into local stationary points. The quest for such points offers a handle to estimate the resonance mass with much reduced dependence on the underlying production and decay dynamics of the resonance.
Mt Somma-Vesuvius is a composite volcano on the southern margin of the Campanian Plain which has been active since 39
ka BP and which poses a hazard and risk for the people living around its base. ...The volcano last erupted in 1944, and since this date has been in repose. As the level of volcanic risk perception is very high in the scientific community, in 1995 a hazard and risk evaluation, and evacuation plan, was published by the Italian Department of Civil Protection (
Dipartimento della Protezione Civile)
. The plan considered the response to a worst-case scenario, taken to be a subplinian eruption on the scale of the 1631
AD eruption, and based on a volcanological reconstruction of this eruption, assumes that a future eruption will be preceded by about two weeks of ground uplift at the volcano's summit, and about one week of locally perceptible seismic activity. Moreover, by analogy with the 1631 events, the plan assumes that ash fall and pyroclastic flow should be recognized as the primary volcanic hazard. To design the response to this subplinian eruption, the emergency plan divided the Somma-Vesuvius region into three hazard zones affected by pyroclastic flows (Red Zone), tephra fall (Yellow and Green Zone), and floods (Blue Zone). The plan at present is the subject of much controversy, and, in our opinion, several assumptions need to be modified according to the following arguments: a) For the precursory unrest problem, recent scientific studies show that at present neither forecast capability is realistic, so that the assumption that a future eruption will be preceded by about two weeks of forecasts need to be modified; b) Regarding the exposure of the Vesuvius region to flow phenomena, the Red Zone presents much inconsistency near the outer border as it has been defined by the administrative limits of the eighteen municipality area lying on the volcano. As this outer limit shows no uniformity, a pressing need exists to define appropriately the flow hazard zone, since there are some important public structures not considered in the current Red Zone that could be exposed to flow risk; c) Modern wind records clearly indicate that at the time of a future eruption winds could blow not only from the west, but also from the east, so that the Yellow Zone (the area with the potential to be affected by significant tephra fall deposits) must be redefined. As a result the relationship between the Yellow Zone and Green Zone (the area within and beyond which the impact of tephra fall is expected to be insignificant) must be reconsidered mainly in the Naples area; d) The May 1998 landslide, caused in the Apennine region east of the volcano by continuous rain fall, led to the definition of a zone affected by re-mobilisation of tephra (Blue Zone), confined in the Nola valley. However, as described in the 1631 chronicles of the eruption, if generation of debris flows occurs during and after a future eruption, a much wider region east of the Somma-Vesuvius must be affected by events of this type.
A
bstract
W
bosons are produced at LHC from a forward-backward symmetric initial state. Their decay to a charged lepton and a neutrino has a strong spin analysing power. The combination of these ...effects results in characteristic distributions of the pseudorapidity of the leptons decaying from
W
+
and
W
−
of different helicity. This observation may open the possibility to measure precisely the
W
+
and
W
−
rapidity distributions for the two transverse polarisation states of W bosons produced at small transverse momentum.
The Campanian Plain in southern Italy has been volcanically active for at least the last 300ka. The Campanian Ignimbrite (CI) erupted at 39.3ka, has a volume of ≥310km3 and a great areal extent. ...However, significant, but scattered deposits of older ignimbrites underlie the CI and document a long history of volcanism. We examined the mineralogy and geochemistry of 11 older ignimbrite strata by optical petrography, electron microprobe, scanning electron microscope, X-ray diffraction, and various whole-rock geochemical techniques. We have analyzed strata at Durazzano (116.1ka), Moschiano (184.7ka), Seiano Valley (245.9 and 289.6ka), and Taurano — Acqua Feconia (157.4, 183.8, 205.6, and 210.4ka) that have been previously dated on unaltered sanidine. The older ignimbrites are highly altered with loss on ignition (LOI) that ranges from 17 to 8wt%. Whole-rock compositions reflect variable element mobility during weathering; e.g., CaO is enriched and Na2O depleted relative to hydration. X-ray diffraction identified major chabazite, kaolinite, and illite alteration products in some samples. Rhabdophane-(Nd), usually intergrown with chabazite and Mn-carbonate, indicates that some LREE were also mobilized during weathering. The phenocryst mineralogy is typical for Campanian Plain (CP) magmas and consists of plagioclase (An88 Ab11 Or1 to An32 Ab63 Or5), potassium feldspar (Or40 Ab57 An3 to Or79 Ab18 An3), biotite (TiO2=~4–7wt%, BaO=up to 2wt%, F=up to 2wt%), diopside (Ca47Mg47Fe6 to Ca48Mg29Fe23), and titaniferous magnetite. Relatively immobile trace elements Zr, Hf, Th, Ta, V, and Nb were used to investigate element abundance and ratio compared to the Campanian Ignimbrite and other CP magmas. Zr/Hf of the older ignimbrites is similar to that of the CI, but Ta is depleted relative to Th and V is enriched compared to CI. Th/Ta and Nb/V distributions for most of the older ignimbrites are similar to those in the Neapolitan Yellow Tuff with the exception of the sample MS-1 from Moschiano that is more evolved and similar to Campanian Ignimbrite. All older ignimbrite Zr/Hf (w/w) and many Nb/Ta (w/w) ratios are superchondritic that suggests that the older ignimbrites represent fractional crystallization products of parental magmas generated from enriched mantle without significant addition of continental crust.
This paper presents mineralogical, chemical, and textural data for the Mount Epomeo Green Tuff and an associated polymictic breccia on Ischia Island, Italy with the purpose of defining the alteration ...history of the two units and the emplacement origin of the polymictic breccia. Our results indicate that the Green Tuff trachytic ignimbrite experienced three alteration events that produced the following mineral assemblages: (1) phillipsite, randomly interstratified (R0) illite/smectite (I/S), Fe-illite, and smectite (in situ Green Tuff); (2) chabazite, phillipsite, R0 I/S, and Fe-illite (proximal facies Green Tuff at Scarrupata di Barano); and (3) analcime, authigenic K-feldspar, Fe-illite, R0 I/S, and smectite (clasts of Green Tuff in polymictic breccia). Phillipsite, chabazite, and R0 I/S within the in situ and proximal facies Green Tuff indicate low-temperature alteration (
T
< 70 °C). The proximal facies Green Tuff contains a vertical mineral zonation, suggesting alteration in an open hydrologic system. Analcime and authigenic K-feldspar assemblages in Green Tuff clasts within the polymictic breccia indicate higher temperature (
T
> 70 °C) alteration within a mostly closed chemical system. These data suggest that the polymictic breccia represents a debris avalanche deposit created by a catastrophic volcanic collapse, which was associated with low-temperature hydrothermal alteration and thus structural weakening of the volcano. The debris avalanche that produced the polymictic breccia on Ischia may be related to nearby massive debris avalanche deposits recently discovered offshore of southern Ischia. The young age of the polymictic breccia (5.7–8.6 ka) and the possibility of its catastrophic emplacement indicate an additional volcanic hazard for Ischia Island.
The CMS data analysis school experience De Filippis, N; Bauerdick, L; Chen, J ...
Journal of physics. Conference series,
10/2017, Letnik:
898, Številka:
10
Journal Article
Recenzirano
Odprti dostop
The CMS Data Analysis School is an official event organized by the CMS Collaboration to teach students and post-docs how to perform a physics analysis. The school is coordinated by the CMS schools ...committee and was first implemented at the LHC Physics Center at Fermilab in 2010. As part of the training, there are a number of "short" exercises on physics object reconstruction and identification, Monte Carlo simulation, and statistical analysis, which are followed by "long" exercises based on physics analyses. Some of the long exercises go beyond the current state of the art of the corresponding CMS analyses. This paper describes the goals of the school, the preparations for a school, the structure of the training, and student satisfaction with the experience as measured by surveys.
Diffusional smoothing of Fe–Mg compositional gradients in clinopyroxene crystals from the 1944 eruption of Vesuvius is used to determine the preeruption residence times of crystals at magmatic ...temperatures. The result is a distribution of crystal residence times from one sample that can be used to constrain magma chamber volumes. Diffusional zones between compositionally distinct cores and rims were observed by backscattered electron (BSE) imaging to vary in width from 1.6 to 11.9 μm and represent storage of crystals at magmatic temperatures for periods ranging from 4.5 months up to 9 years prior to eruption. The distribution of residence times is skewed to young ages and is best explained by the open-system behaviour of an 8.0×10
7 m
3 chamber that received an input of between 3.5×10
7 and 7.0×10
7 m
3 in the final 6 months prior to eruption. The calculated inputs, compared with contemporary observations of the emitted magma volumes, implies that some 3.0×10
7–6.5×10
7 m
3 of magma input did not erupt but was accommodated by chamber expansion before the 1944 eruption. This would place the preeruptive chamber volume between 1.15×10
8 and 1.5×10
8 m
3. The eruption was then triggered by a further input of ∼1.9×10
7 m
3 which forced the extrusion of a similar volume of relatively degassed magma as lava flows prior to the fire-fountaining episode. The backscattered electron imaging technique for residence time determination has great potential in unravelling the histories of populations of phenocrysts in many volcanic systems.
The Campanian Plain is an 80x30km region of southern Italy, bordered by the Apennine Chain, that has experienced subsidence during the Quaternary. This region, volcanologically active in the last ...600ka, has been identified as the Campanian Volcanic Zone (CVZ). The products of three periods of trachytic ignimbrite volcanism (289-246ka, 157ka and 106ka) have been identified in the Apennine area in the last 300ka. These deposits probably represent distal ash flow units of ignimbrite eruptions which occurred throughout the CVZ. The resulting deposits are interstratified with marine sediments indicating that periods of repeated volcano-tectonic emergence and subsidence may have occurred in the past. The eruption, defined as the Campanian Ignimbrite (CI), with the largest volume (310km3), occurred in the CVZ 39ka ago. The products of the CI eruption consist of two units (unit-1 and unit-2) formed from a single compositionally zoned magma body. Slightly different in composition, three trachytic melts constitute the two units. Unit-1 type A is an acid trachyte, type B is a trachyte and type C of unit-2 is a mafic trachyte. The CI, vented from pre-existing neotectonic faults, formed during the Apennine uplift. Initially the venting of volatile-rich type A magma deposited the products to the N-NE of the CVZ. During the eruption, the Acerra graben already affected by a NE-SW fault system, was transected by E-W faults, forming a cross-graben that extended to the gulf of Naples. E-W faults were then further dislocated by NE-SW transcurrent movements. This additional collapse significantly influenced the deposition of the B-type magma of unit-1, and the C-type magma of unit-2 toward the E-SE and S, in the Bay of Naples. The pumice fall deposit underlying the CI deposits, until now thought to be associated with the CI eruption, is not a strict transition from plinian to CI-forming activity. It is derived instead from an independent source probably located near the Naples area. This initial volcanic activity is assumed to be a precursor to the CI trachytic eruptions, which vented along regional faults. PUBLICATION ABSTRACT
Between 1884 B.C. and A.D. 472, eruptive activity at Somma–Vesuvius was dominated by the three plinian eruptions of Avellino (3550 yr B.P.), Pompei (A.D. 79) and A.D. 472 and, as a result, little ...attention has been given to the intervening interplinian activity. The interplinian events are here reconstructed using new data from twenty stratigraphic sections around the lower flanks of the volcano. Three main eruptions have been identified for the protohistoric period (3550 yr B.P.–A.D. 79). The first two occurred shortly after the Avellino event and both show a progression from magmatic to phreatomagmatic behaviour. The third eruption (2700 B.P.) consisted of five phreatomagmatic episodes separated by the emplacement of mud flows. Only one event, the explosive eruption of A.D. 203, has been identified for the ancient historic period (A.D. 79–472). In contrast, the A.D. 472 eruption was followed during the medieval period (A.D. 472–1631) by comparatively vigorous interplinian activity, including four strombolian–phreatomagmatic events and extensive lava effusion, which formed a summit cone (destroyed in A.D. 1631) similar to that on Vesuvius today. Such regular alternations of plinian and interplinian events are evident only since 3550 yr B.P. and provide important constraints for forecasting future behaviour at Somma–Vesuvius.
The ∼ 150 km3 (DRE) trachytic Campanian Ignimbrite, which is situated north-west of Naples, Italy, is one of the largest eruptions in the Mediterranean region in the last 200 ky. Despite centuries of ...investigation, the age and eruptive history of the Campanian Ignimbrite is still debated, as is the chronology of other significant volcanic events of the Campanian Plain within the last 200-300 ky. New 40Ar/39Ar geochronology defines the age of the Campanian Ignimbrite at 39.28 ± 0.11 ka, about 2 ky older than the previous best estimate. Based on the distribution of the Campanian Ignimbrite and associated uppermost proximal lithic and polyclastic breccias, we suggest that the Campanian Ignimbrite magma was emitted from fissures activated along neotectonic Apennine faults rather than from ring fractures defining a Campi Flegrei caldera. Significantly, new volcanological, geochronological, and geochemical data distinguish previously unrecognized ignimbrite deposits in the Campanian Plain, accurately dated between 157 and 205 ka. These ages, coupled with a xenocrystic sanidine component > 315 ka, extend the volcanic history of this region by over 200 ky. Recent work also identifies a pyroclastic deposit, dated at 18.0 ka, outside of the topographic Campi Flegrei basin, expanding the spatial distribution of post-Campanian Ignimbrite deposits. These new discoveries emphasize the importance of continued investigation of the ages, distribution, volumes, and eruption dynamics of volcanic events associated with the Campanian Plain. Such information is critical for accurate assessment of the volcanic hazards associated with potentially large-volume explosive eruptions in close proximity to the densely populated Neapolitan region.
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