1,721,113 research outputs found
Fragmentation patterns of jets in pPb collisions in CMS
No full textThe nuclear parton distribution function and flavor composition of hard scattering processes can be accurately studied using the jet fragmentation functions. Recent measurements of the pPb nuclear modification factor (), with diverging values for inclusive jets and charged hadrons, have raised question on jet fragmentation properties in pPb collisions. These spectra measurements are performed with pp reference at 5.02 TeV constructed by interpolation or extrapolation from different , and on steeply falling power-law spectra. As the jet fragmentation function is only evolving logarithmically with , this further underscores the importance of a direct measurement. Together with the CMS results in pPb inclusive jets and charge hadron , we introduce the new CMS measurement of fragmentation function in pPb collisions, where within our uncertainties, jets in pPb is found to have identical fragmentation property vs. pp jets. We will further discuss the consistency and tension among the results, and their possible origins. This measurement also gives important reference for the interpretation of the fragmentation function in PbPb collisions
Molecular Dynamics Simulation of the Transport Properties of Molten Transuranic Chloride Salts
Get PDFThe Accelerator Research Laboratory at Texas A&M is proposing a design for accelerator-driven subcritical fission in molten salt (ADSMS), a system that destroys the transuranic elements in used nuclear fuel. The transuranics (TRU) are the most enduring hazard of nuclear power. TRU contain high radiotoxicity and have half-lives of a thousand to a million years. The ADSMS core is fueled by a homogeneous chloride-based molten salt mixture containing TRUCl3 and NaCl. Certain thermodynamic properties are critical to modeling both the neutronics and heat transfer of an ADSMS system. There is a lack of experimental data on the density, heat capacity, electrical and thermal conductivities, and viscosity of TRUCl3 salt systems. Molecular dynamics simulations using a polarizable ion model (PIM) are employed to determine the density and heat capacity of these melts as a function of temperature. Green-Kubo methods are implemented to calculate the electrical conductivity, thermal conductivity, and viscosity of the salt using the outputs of the simulations. Results for pure molten salt systems are compared to experimental data when possible to validate the potentials used. Here I discuss chloride salt systems of interest, their calculated properties, and possible sources of error for our simulations
10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions
No full textThe differential yields of Z bosons decaying to lepton pairs are measured in PbPb collisions collected in 2018 by the CMS experiment at the LHC. The measurement uses 1.8 nb of 5.02~TeV data. The yields in various centrality bins are compared to the HG-PYTHIA model, which indicates that geometric and selection biases could be present for peripheral events. In some cases, the uncertainties of the measurement are smaller than the modeling uncertainties of the Glauber model, showing that Z-counting could be a preferred experimental measure of effective nucleon-nucleon luminosity. Additionally, a high precision measurement of the Z boson azimuthal anisotropy () is presented. This observable provides a second method to study whether Z bosons reconstructed in the leptonic decay channel experience significant final-state modifications. This is relevant for measurements in which a high- Z boson is used as a tag of a recoiling jet’s . The final state modification of these jets is quantified by examining the imbalance of Z boson + jet pairs. A new measurement of the Drell-Yan (DY) process is also presented in pPb collision at the center of mass energy of 8.16 TeV with the CMS detector. The rapidity dependence of this process is particularly sensitive to nPDFs, but further information can be gained by studying the mass dependence of DY production, measured for the first time in pPb collisions at 8.16 TeV, down to 15 GeV. In addition, differential measurements in the dimuon or (an angular variable correlated with measured for the first time in pPb) provide insights on soft gluon emission at low
Observation of enhanced long-range elliptic anisotropies inside high-multiplicity jets in pp collisions at the LHC, with the CMS detector
No full textIt has been postulated that nonperturbative quantum chromodynamics (QCD) evolution of a single parton in the vacuum can develop long-range collective effects of a multiparton system, reminiscent of those observed in high-energy nuclear interactions from the formation of a quark-gluon plasma. For the first time, a search for such QCD collective effects is performed via correlation measurements of charged constituents inside jets produced in high-pileup proton-proton (pp) collisions. The data set used corresponds to the full LHC Run-2 sample, with an integrated luminosity of 138 fb recorded by the CMS experiment at TeV. For charged constituents within a reconstructed jet of cone radius 0.8, two-particle correlations as functions of relative azimuthal angle () and pseudorapidity () are performed in a novel "jet frame'', where constituent kinematics are defined relative to the jet direction being the axis. The correlation functions are studied in classes of in-jet charged multiplicity up to nearly 100 for different ranges of transverse momentum in the jet frame. Anisotropy Fourier harmonics are extracted from long-range azimuthal correlation functions for \left|\Delta\eta^\ast\right|>2. A striking rising trend for the long-range elliptic anisotropy harmonic is found to emerge at in-jet charged multiplicity above about 80 in the data but not reproduced by MC models. This observed enhancement might indicate new dynamics of the parton fragmentation process in the vacuum, and potentially opening up a new experimental direction for studying QCD emergent phenomena using high-luminosity pp data sets.PLEASE NOTE THIS SEMINAR WILL BE VIA ZOOM ONLY</p
Initial Stages 2021
No full textThe electroweak process is often used to probe the parton distribution functions (PDFs) in a proton and the nuclear parton distribution functions (nPDFs) in heavy ions. In this presentation, the measurements of the Drell-Yan process in pPb collisions at 8.16 TeV and of Z bosons decaying to pairs of leptons in PbPb collisions using data collected at 5.02 TeV from the CMS experiment at the LHC will be summarized.
In pPb collisions, the dimuon rapidity, mass, , and (which is an angular variable correlated with measured for the first time in pPb collisions) dependences are shown. In addition, comparisons to theoretical proton PDF and nPDF models show that the data are sensitive to the presence of nuclear modifications to the parton distributions in the lead nucleus, and can help improve and constrain theoretical calculations.
In PbPb collisions, the differential cross-sections of Z bosons decaying to pairs of leptons are measured as a function of transverse momentum \pt and rapidity . The measurements are performed with an integrated luminosity of 1.7 nb, using the dimuon and dielectron decay channels. High precision measurement of the Z boson elliptic azimuthal anisotropy is found to be compatible with zero, showing that Z bosons do not experience a significant final-state modification in heavy-ion collisions. Yields of Z bosons in various centrality bins are compared to Glauber model predictions for the production rates of hard probes not modified by the presence of initial collision geometry and centrality selection effects
CMS Heavy-Ion Overview
No full textRecent results from the CMS Collaboration are presented. These measurements include a full physics program using ultraperipheral collisions such as photon-photon and photon-ion interactions, small collision systems including proton-proton and proton-lead collisions, and many measurements of hadronic ion-ion collisions. The properties of the quark-gluon plasma produced in ion-ion collisions are studied in detail. The measurements examine the number of degrees of freedom of the medium, the strength of jet quenching effects in the medium, the role of heavy flavor in hadronization processes, and more
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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