1,824 research outputs found
A low energy ion beamline for TwinEBIS
No full textA low energy beamline has been designed for the TwinEBIS setup. The beamline will be used to transport ions extracted from the electron beam ion source into an accelerating radio frequency quadrupole or into secondary devices, like a time of flight-mass spectrometer, attached to the beamline via a fast three way
20° ion switchyard. Optional injection of ions from an external source into the electron beam ion source is foreseen. In this article the general layout of the
beamline is presented and supported with simulations of the ion-optical matching. Furthermore, the switchyard and gridded electrostatic lenses, chosen as the main focusing elements, have been
simulated to assess their impact on the beam quality and the dynamics of secondary electrons emitted by the gridded lenses. In addition, the beamline includes general diagnostic devices, including a
bidirectional pepperpot beam profiler. An overview of the diagnostic elements is given
Freedom Bid
No full textPhotograph used for a story in the Daily Oklahoman newspaper. Caption: "Aging convict Orville J. Pitters is escourted to court Thursday by Oklahoma County Deputy Carey Canady.
High Frequency RFQ Design and LEBT Matching for the CERN TwinEBIS Ion Source
No full textAn Electron Beam Ion Source (EBIS) is being developed at CERN for production of highly charged ions, for instance fully stripped C. The focus has so far been on the electron gun design, aiming for a high current compression, which results in a rapid ionisation process and thereby high repetition rate. Initial commissioning tests of such an electron gun, the so-called MEDeGUN, have already been performed and we are now in the process of designing a multi-purpose ion extraction and diagnostics line. The Low Energy Beam Transport (LEBT) line will transport the ions into the downstream Radio Frequency Quadrupole (RFQ) with a nominal energy of 15 keV/u. The 750 MHz RFQ is designed to accelerate ions from 15 keV/u up to the final energy of 2.5 MeV/u. After the RFQ design was finalized and its acceptance calculated, the beam matching to the RFQ was studied, finding a set of parameters for the LEBT that maximize the transmission through the RFQ. Details of the RFQ design, of the LEBT matching procedure and its final results are illustrated in this paper
[Manila envelope with pencil writing on it]
No full textManila envelope that contained one 8 x 10 photograph 2000.057.063b. The front of the envelope has pencil writing that reads: "12 - 8 x 10 nights of Pitters (?) 105 Bouth (?)". Written on back of envelope in pencil: "Due 10 00 [line] x x goe 4261 180 2 [line] 360 180 [line] 540 3 3 3 3 x 3 J"
Fragmentation of jets containing a prompt J/ψ meson in PbPb and pp collisions at √sNN = 5.02 TeV
No full textCopyright © 2021 The Author(s). Jets containing a prompt J/ψ meson are studied in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV, using the CMS detector at the LHC. Jets are selected to be in the transverse momentum range of 30 < pT < 40 GeV. The J/ψ yield in these jets is evaluated as a function of the jet fragmentation variable z, the ratio of the J/ψ pT to the jet pT. The nuclear modification factor, RAA, is then derived by comparing the yield in lead-lead collisions to the corresponding expectation based on proton-proton data, at the same nucleon-nucleon center-of-mass energy. The suppression of the J/ψ yield shows a dependence on z, indicating that the interaction of the J/ψ with the quark-gluon plasma formed in heavy ion collisions depends on the fragmentation that gives rise to the J/ψ mesonFunded by SCOAP3
Aspects of exchangeable coalescent processes
No full textIn mathematical population genetics a multiple merger n-coalescent process, or Λ n-coalescent process, {Πn(t) t ≥ 0} models the genealogical tree of a sample of size n (e.g. of DNA sequences) drawn from a large population of haploid individuals. We study various properties of Λ coalescents. Novel in our approach is that we introduce the partition lattice as well as cumulants into the study of functionals of coalescent processes. We illustrate the success of this approach on several examples. Cumulants allow us to reveal the relation between the tree height, Tn, respectively the total branch length, Ln, of the genealogical tree of Kingman’s n-coalescent, arguably the most celebrated coalescent process, and the Riemann zeta function. Drawing on results from lattice theory, we give a spectral decomposition for the generator of both the Kingman and the Bolthausen-Sznitman n-coalescent, the latter of which emerges as a genealogy in models of populations undergoing selection. Taking mutations into account, let Mj count the number of mutations that are shared by j individuals in the sample. The random vector (M1,...,Mn-1), known as the site frequency spectrum, can be measured from genetical data and is therefore an important statistic from the point of view of applications. Fu worked out the expected value, the variance and the covariance of the marginals of the site frequency spectrum. Using the partition lattice we derive a formula for the cumulants of arbitrary order of the marginals of the site frequency spectrum. Following another line of research, we provide a law of large numbers for a family of Λ coalescents. To be more specific, we show that the process {#Πn(t), t ≥ 0} recording the number #Πn(t) of individuals in the coalescent at time t, coverges, after a suitable rescaling, towards a deterministic limit as the sample size n grows without bound. In the statistical physics literature this limit is known as a hydrodynamic limit. Up to date the hydrodynamic limit was known for Kingman’s coalescent, but not for other Λ coalescents. We work out the hydrodynamic limit for beta coalescents that come down from infinity, which is an important subclass of the Λ coalescents
Fragmentation of jets containing a prompt J/psi meson in PbPb and pp collisions at root s(NN)=5.02 TeV
No full textJets containing a prompt J/ψ meson are studied in lead-lead collisions at a nucleon-nucleon center-ofmass energy of 5.02 TeV, using the CMS detector at the LHC. Jets are selected to be in the transverse
momentum range of 30 < pT < 40 GeV. The J/ψ yield in these jets is evaluated as a function of the jet
fragmentation variable z, the ratio of the J/ψ pT to the jet pT. The nuclear modification factor, RAA,
is then derived by comparing the yield in lead-lead collisions to the corresponding expectation based
on proton-proton data, at the same nucleon-nucleon center-of-mass energy. The suppression of the J/ψ
yield shows a dependence on z, indicating that the interaction of the J/ψ with the quark-gluon plasma
formed in heavy ion collisions depends on the fragmentation that gives rise to the J/ψ meson
Author Correction: A portrait of the Higgs boson by the CMS experiment ten years after the discovery
No full textIn the version of this article initially published, CMS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the articl
Study of meson production from jet fragmentation in pp collisions at 8 TeV
No full textA study of the production of prompt mesons as fragmentation products of jets in proton-proton collisions at 8 TeV is presented. The analysis is based on data corresponding to an integrated luminosity of 19.1 fb collected with the CMS detector at the LHC. For events with at least one observed jet, the angular separation between the meson and the jet is used to test whether the meson is a jet fragment. The analysis shows that most prompt mesons with energy above 15 GeV and rapidity 1 are fragments of jets with pseudorapidity 1. The differential distributions of the jet fragmentation probability as a function of jet energy for a fixed energy fraction are compared to a theoretical model using the fragmenting jet function approach. The data agree best with fragmenting jet function calculations that use a long-distance matrix element parameter set in which prompt mesons are unpolarized. This technique demonstrates a new way to test predictions for prompt production using nonrelativistic quantum chromodynamics.A study of the production of prompt J/ψ mesons contained in jets in proton-proton collisions at s=8TeV is presented. The analysis is based on data corresponding to an integrated luminosity of 19.1 fb −1 collected with the CMS detector at the LHC. For events with at least one observed jet, the angular separation between the J/ψ meson and the jet is used to test whether the J/ψ meson is part of the jet. The analysis shows that most prompt J/ψ mesons having energy above 15 GeV and rapidity |y|<1 are contained in jets with pseudorapidity |ηjet|<1 . The differential distributions of the probability to have a J/ψ meson contained in a jet as a function of jet energy for a fixed J/ψ energy fraction are compared to a theoretical model using the fragmenting jet function approach. The data agree best with fragmenting jet function calculations that use a long-distance matrix element parameter set in which prompt J/ψ mesons are predicted to be unpolarized. This technique demonstrates a new way to test predictions for prompt J/ψ production using nonrelativistic quantum chromodynamics.A study of the production of prompt J/ mesons contained in jets in proton-proton collisions at 8 TeV is presented. The analysis is based on data corresponding to an integrated luminosity of 19.1 fb collected with the CMS detector at the LHC. For events with at least one observed jet, the angular separation between the J/ meson and the jet is used to test whether the J/ meson is part of the jet. The analysis shows that most prompt J/ mesons with energy above 15 GeV and rapidity 1 are contained in jets with pseudorapidity 1. The differential distributions of the probability to have a J/ meson contained in a jet as a function of jet energy for a fixed J/ energy fraction are compared to a theoretical model using the fragmenting jet function approach. The data agree best with fragmenting jet function calculations that use a long-distance matrix element parameter set in which prompt J/ mesons are predicted to be unpolarized. This technique demonstrates a new way to test predictions for prompt J/ production using nonrelativistic quantum chromodynamics
Study of the decay in proton-proton collisions at 8 TeV
No full textA study of the decay using proton-proton collision data collected at 8 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.6 fb, is presented. The ratio of branching fractions is measured to be (1.054 0.057 (stat) 0.035 (syst) 0.011 () )%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of and decays to reconstructed final states. The invariant mass distributions of the , , and systems produced in the decay are investigated and found to be inconsistent with the pure phase space hypothesis. The analysis is extended by using a model-independent angular amplitude analysis, which shows that the inclusion of contributions from excited kaons decaying to the system improves the description of the observed invariant mass distributions.A study of the decay using proton-proton collision data collected at = 8 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.6 fb, is presented. The ratio of branching fractions is measured to be (1.054 ± 0.057(stat) ± 0.035(syst) ± 0.011())%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of and K(892) decays to reconstructed final states. The invariant mass distributions of the , J/ψp, and systems produced in the decay are investigated and found to be inconsistent with the pure phase space hypothesis. The analysis is extended by using a model-independent angular amplitude analysis, which shows that the observed invariant mass distributions are consistent with the contributions from excited kaons decaying to the system.A study of the BJp decay using proton-proton collision data collected at 8 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.6 fb, is presented. The ratio of branching fractions (BJp )(BJK(892)) is measured to be (1.054 0.057 (stat) 0.035 (syst) 0.011 ())%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of and K(892) decays to reconstructed final states. The invariant mass distributions of the J, Jp, and p systems produced in the BJp decay are investigated and found to be inconsistent with the pure phase space hypothesis. The analysis is extended by using a model-independent angular amplitude analysis, which shows that the inclusion of contributions from excited kaons decaying to the p system improves the description of the observed invariant mass distributions
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