189 research outputs found
Detailed analysis of the cell-inactivation mechanism by accelerated protons and light ions
Published survival data for V79 cells irradiated by monoenergetic protons,
helium-3, carbon, and oxygen ions and for CHO cells irradiated by carbon ions
have been analyzed using the probabilistic two-stage model of cell
inactivation. Three different classes of DNA damages formed by traversing
particles have been distinguished, namely severe single-track damages which
might lead to cell inactivation directly, less severe damages where cell
inactivation is caused by their combinations, and damages of negligible
severity that can be repaired easily. Probabilities of single ions to form
these damages have been assessed in dependence on their linear energy transfer
(LET) values.
Damage induction probabilities increase with atomic number and LET. While
combined damages play crucial role at lower LET values, single-track damages
dominate in high-LET regions. The yields of single-track lethal damages for
protons have been compared with the Monte Carlo estimates of complex DNA
lesions, indicating that lethal events correlate well with complex DNA
double-strand breaks. The decrease in the single-track damage probability for
protons of LET above approx. 30 keV/m, suggested by limited experimental
evidence, is discussed, together with the consequent differences in the
mechanisms of biological effects between protons and heavier ions. Applications
of the results in hadrontherapy treatment planning are outlined.Comment: submitted to Physics in Medicine and Biolog
Physical theory of the twentieth century and contemporary philosophy
It has been shown that the criticism of Pauli as well as of Susskind and
Glogover may be avoided if the standard quantum-mechanical mathematical model
has been suitably extended. There is not more any reason for Einstein's
citicism, either, if in addition to some new results concerning Bell's
inequalities and Belifante's argument are taken into account. The ensemble
interpretation of quantum mechanics (or the hidden-variable theory) should be
preferred, which is also supported by the already published results of
experiments with three polarizers. Greater space in the text has been devoted
also to the discussion of epistemological problems and some philosophical
consequences.Comment: 12 page
Second specimen of the Late Cretaceous sauropod dinosaur Diamantinasaurus matildae provides new anatomical information on skull and neck evolution in early titanosaurs and the biogeographic origins of Australian dinosaur faunas
The titanosaurian sauropod dinosaur Diamantinasaurus matildae is represented by two individuals from the Cenomanian–lower Turonian ‘upper’ Winton Formation of central Queensland, north-eastern Australia. The type specimen has been described in detail, whereas the referred specimen, which includes several elements not present in the type series (partial skull, atlas, axis and postaxial cervical vertebrae), has only been described briefly. Herein, we provide a comprehensive description of this referred specimen, including a thorough assessment of the external and internal anatomy of the braincase, and identify several new autapomorphies of D. matildae. Via an expanded data matrix consisting of 125 taxa scored for 552 characters, we recover a close, well-supported relationship between Diamantinasaurus and its contemporary, Savannasaurus elliottorum. Unlike previous iterations of this data matrix, under a parsimony framework we consistently recover Diamantinasaurus and Savannasaurus as early-diverging members of Titanosauria using both equal weighting and extended implied weighting, with the overall topology largely consistent between analyses. We erect a new clade, named Diamantinasauria herein, that also includes the contemporaneous Sarmientosaurus musacchioi from southern Argentina, which shares several cranial features with the referred Diamantinasaurus specimen. Thus, Diamantinasauria is represented in the mid-Cretaceous of both South America and Australia, supporting the hypothesis that some titanosaurians, in addition to megaraptoran theropods and possibly some ornithopods, were able to disperse between these two continents via Antarctica. Conversely, there is no evidence for rebbachisaurids in Australia, which might indicate that they were unable to expand into high latitudes before their extinction in the Cenomanian–Turonian. Likewise, there is no evidence for titanosaurs with procoelous caudal vertebrae in the mid-Cretaceous Australian record, despite scarce but compelling evidence for their presence in both Antarctica and New Zealand during the Campanian–Maastrichtian. These later titanosaurs presumably dispersed into these landmasses from South America before the Campanian (~85 Mya), when seafloor spreading between Zealandia and Australia commenced. Although Australian mid-Cretaceous dinosaur faunas appear to be cosmopolitan at higher taxonomic levels, closer affinities with South America at finer scales are becoming better supported for sauropods, theropods and ornithopods
LHC Optics Measurement with Proton Tracks Detected by the Roman Pots of the TOTEM Experiment
Precise knowledge of the beam optics at the LHC is crucial to fulfil the
physics goals of the TOTEM experiment, where the kinematics of the scattered
protons is reconstructed with the near-beam telescopes -- so-called Roman Pots
(RP). Before being detected, the protons' trajectories are influenced by the
magnetic fields of the accelerator lattice. Thus precise understanding of the
proton transport is of key importance for the experiment. A novel method of
optics evaluation is proposed which exploits kinematical distributions of
elastically scattered protons observed in the RPs. Theoretical predictions, as
well as Monte Carlo studies, show that the residual uncertainty of this optics
estimation method is smaller than 0.25 percent.Comment: 20 pages, 11 figures, 5 figures, to be submitted to New J. Phy
Double diffractive cross-section measurement in the forward region at LHC
The first double diffractive cross-section measurement in the very forward
region has been carried out by the TOTEM experiment at the LHC with
center-of-mass energy of sqrt(s)=7 TeV. By utilizing the very forward TOTEM
tracking detectors T1 and T2, which extend up to |eta|=6.5, a clean sample of
double diffractive pp events was extracted. From these events, we measured the
cross-section sigma_DD =(116 +- 25) mub for events where both diffractive
systems have 4.7 <|eta|_min < 6.5 .Comment: 5 pages, 1 figure, submitted for publicatio
Diamond Detectors for the TOTEM Timing Upgrade
This paper describes the design and the performance of the timing detector
developed by the TOTEM Collaboration for the Roman Pots (RPs) to measure the
Time-Of-Flight (TOF) of the protons produced in central diffractive
interactions at the LHC. The measurement of the TOF of the protons allows the
determination of the longitudinal position of the proton interaction vertex and
its association with one of the vertices reconstructed by the CMS detectors.
The TOF detector is based on single crystal Chemical Vapor Deposition (scCVD)
diamond plates and is designed to measure the protons TOF with about 50 ps time
precision. This upgrade to the TOTEM apparatus will be used in the LHC run 2
and will tag the central diffractive events up to an interaction pileup of
about 1. A dedicated fast and low noise electronics for the signal
amplification has been developed. The digitization of the diamond signal is
performed by sampling the waveform. After introducing the physics studies that
will most profit from the addition of these new detectors, we discuss in detail
the optimization and the performance of the first TOF detector installed in the
LHC in November 2015.Comment: 26 pages, 18 figures, 2 tables, submitted for publication to JINS
Evidence for non-exponential elastic proton-proton differential cross-section at low |t| and sqrt(s) = 8 TeV by TOTEM
The TOTEM experiment has made a precise measurement of the elastic
proton-proton differential cross-section at the centre-of-mass energy sqrt(s) =
8 TeV based on a high-statistics data sample obtained with the beta* = 90
optics. Both the statistical and systematic uncertainties remain below 1%,
except for the t-independent contribution from the overall normalisation. This
unprecedented precision allows to exclude a purely exponential differential
cross-section in the range of four-momentum transfer squared 0.027 < |t| < 0.2
GeV^2 with a significance greater than 7 sigma. Two extended parametrisations,
with quadratic and cubic polynomials in the exponent, are shown to be well
compatible with the data. Using them for the differential cross-section
extrapolation to t = 0, and further applying the optical theorem, yields total
cross-section estimates of (101.5 +- 2.1) mb and (101.9 +- 2.1) mb,
respectively, in agreement with previous TOTEM measurements.Comment: Final version published in Nuclear Physics
Performance of the TOTEM Detectors at the LHC
The TOTEM Experiment is designed to measure the total proton-proton
cross-section with the luminosity-independent method and to study elastic and
diffractive pp scattering at the LHC. To achieve optimum forward coverage for
charged particles emitted by the pp collisions in the interaction point IP5,
two tracking telescopes, T1 and T2, are installed on each side of the IP in the
pseudorapidity region 3.1 < = |eta | < = 6.5, and special movable beam-pipe
insertions - called Roman Pots (RP) - are placed at distances of +- 147 m and
+- 220 m from IP5. This article describes in detail the working of the TOTEM
detector to produce physics results in the first three years of operation and
data taking at the LHC.Comment: 40 pages, 31 figures, submitted to Int. J. Mod. Phys.
Elastic Scattering and Total Cross-Section in p+p reactions measured by the LHC Experiment TOTEM at sqrt(s) = 7 TeV
Proton-proton elastic scattering has been measured by the TOTEM experiment at
the CERN Large Hadron Collider at TeV in special runs with the
Roman Pot detectors placed as close to the outgoing beam as seven times the
transverse beam size. The differential cross-section measurements are reported
in the |t|-range of 0.36 to 2.5 GeV^2. Extending the range of data to low t
values from 0.02 to 0.33 GeV^2,and utilizing the luminosity measurements of
CMS, the total proton-proton cross section at sqrt(s) = 7 TeV is measured to be
(98.3 +- 0.2(stat) +- 2.8(syst)) mb.Comment: Proceedings of the XLI International Symposium on Multiparticle
Dynamics. Accepted for publication in Prog. Theor. Phy
Proton-proton elastic scattering at the LHC energy of {\surd} = 7 TeV
Proton-proton elastic scattering has been measured by the TOTEM experiment at
the CERN Large Hadron Collider at {\surd}s = 7 TeV in dedicated runs with the
Roman Pot detectors placed as close as seven times the transverse beam size
(sbeam) from the outgoing beams. After careful study of the accelerator optics
and the detector alignment, |t|, the square of four-momentum transferred in the
elastic scattering process, has been determined with an uncertainty of d t =
0.1GeV p|t|. In this letter, first results of the differential cross section
are presented covering a |t|-range from 0.36 to 2.5GeV2. The differential
cross-section in the range 0.36 < |t| < 0.47 GeV2 is described by an
exponential with a slope parameter B = (23.6{\pm}0.5stat {\pm}0.4syst)GeV-2,
followed by a significant diffractive minimum at |t| =
(0.53{\pm}0.01stat{\pm}0.01syst)GeV2. For |t|-values larger than ~ 1.5GeV2, the
cross-section exhibits a power law behaviour with an exponent of -7.8_\pm}
0.3stat{\pm}0.1syst. When compared to predictions based on the different
available models, the data show a strong discriminative power despite the small
t-range covered.Comment: 12pages, 5 figures, CERN preprin
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