312 research outputs found
Baryon Inhomogeneity Generation in the Quark-Gluon Plasma Phase
We discuss the possibility of generation of baryon inhomogeneities in a
quark-gluon plasma phase due to moving Z(3) interfaces. By modeling the
dependence of effective mass of the quarks on the Polyakov loop order
parameter, we study the reflection of quarks from collapsing Z(3) interfaces
and estimate resulting baryon inhomogeneities in the context of the early
universe. We argue that in the context of certain low energy scale inflationary
models, it is possible that large Z(3) walls arise at the end of the reheating
stage. Collapse of such walls could lead to baryon inhomogeneities which may be
separated by large distances near the QCD scale. Importantly, the generation of
these inhomogeneities is insensitive to the order, or even the existence, of
the quark-hadron phase transition. We also briefly discuss the possibility of
formation of quark nuggets in this model, as well as baryon inhomogeneity
generation in relativistic heavy-ion collisions.Comment: 11 pages, 2 figures, revtex4, more detailed discussion added about
formation and evolution of Z(3)domain walls in the univers
Effects of quarks on the formation and evolution of Z(3) walls and strings in relativistic heavy-ion collisions
We investigate the effects of explicit breaking of Z(3) symmetry due to the
presence of dynamical quarks on the formation and evolution of Z(3) walls and
associated QGP strings within Polyakov loop model. We carry out numerical
simulations of the first order quark-hadron phase transition via bubble
nucleation (which may be appropriate, for example, at finite baryon chemical
potential) in the context of relativistic heavy-ion collision experiments.
Using appropriate shifting of the order parameter in the Polyakov loop
effective potential, we calculate the bubble profiles using bounce technique,
for the true vacuum as well as for the metastable Z(3) vacua, and estimate the
associated nucleation probabilities. These different bubbles are then nucleated
and evolved and resulting formation and dynamics of Z(3) walls and QGP strings
is studied. We discuss various implications of the existence of these Z(3)
interfaces and the QGP strings, especially in view of the effects of the
explicit breaking of the Z(3) symmetry on the formation and dynamical evolution
of these objects.Comment: 17 pages, 9 figures, PDFLate
Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)
The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the
India-based Neutrino Observatory (INO) is designed to study the atmospheric
neutrinos and antineutrinos separately over a wide range of energies and path
lengths. The primary focus of this experiment is to explore the Earth matter
effects by observing the energy and zenith angle dependence of the atmospheric
neutrinos in the multi-GeV range. This study will be crucial to address some of
the outstanding issues in neutrino oscillation physics, including the
fundamental issue of neutrino mass hierarchy. In this document, we present the
physics potential of the detector as obtained from realistic detector
simulations. We describe the simulation framework, the neutrino interactions in
the detector, and the expected response of the detector to particles traversing
it. The ICAL detector can determine the energy and direction of the muons to a
high precision, and in addition, its sensitivity to multi-GeV hadrons increases
its physics reach substantially. Its charge identification capability, and
hence its ability to distinguish neutrinos from antineutrinos, makes it an
efficient detector for determining the neutrino mass hierarchy. In this report,
we outline the analyses carried out for the determination of neutrino mass
hierarchy and precision measurements of atmospheric neutrino mixing parameters
at ICAL, and give the expected physics reach of the detector with 10 years of
runtime. We also explore the potential of ICAL for probing new physics
scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration,
Contents identical with the version published in Pramana - J. Physic
Evaluation of individual and ensemble probabilistic forecasts of COVID-19 mortality in the United States
Short-term probabilistic forecasts of the trajectory of the COVID-19 pandemic in the United States have served as a visible and important communication channel between the scientific modeling community and both the general public and decision-makers. Forecasting models provide specific, quantitative, and evaluable predictions that inform short-term decisions such as healthcare staffing needs, school closures, and allocation of medical supplies. Starting in April 2020, the US COVID-19 Forecast Hub (https://covid19forecasthub.org/) collected, disseminated, and synthesized tens of millions of specific predictions from more than 90 different academic, industry, and independent research groups. A multimodel ensemble forecast that combined predictions from dozens of groups every week provided the most consistently accurate probabilistic forecasts of incident deaths due to COVID-19 at the state and national level from April 2020 through October 2021. The performance of 27 individual models that submitted complete forecasts of COVID-19 deaths consistently throughout this year showed high variability in forecast skill across time, geospatial units, and forecast horizons. Two-thirds of the models evaluated showed better accuracy than a naĂŻve baseline model. Forecast accuracy degraded as models made predictions further into the future, with probabilistic error at a 20-wk horizon three to five times larger than when predicting at a 1-wk horizon. This project underscores the role that collaboration and active coordination between governmental public-health agencies, academic modeling teams, and industry partners can play in developing modern modeling capabilities to support local, state, and federal response to outbreaks
The United States COVID-19 Forecast Hub dataset
Academic researchers, government agencies, industry groups, and individuals have produced forecasts at an unprecedented scale during the COVID-19 pandemic. To leverage these forecasts, the United States Centers for Disease Control and Prevention (CDC) partnered with an academic research lab at the University of Massachusetts Amherst to create the US COVID-19 Forecast Hub. Launched in April 2020, the Forecast Hub is a dataset with point and probabilistic forecasts of incident cases, incident hospitalizations, incident deaths, and cumulative deaths due to COVID-19 at county, state, and national, levels in the United States. Included forecasts represent a variety of modeling approaches, data sources, and assumptions regarding the spread of COVID-19. The goal of this dataset is to establish a standardized and comparable set of short-term forecasts from modeling teams. These data can be used to develop ensemble models, communicate forecasts to the public, create visualizations, compare models, and inform policies regarding COVID-19 mitigation. These open-source data are available via download from GitHub, through an online API, and through R packages
Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV
A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe
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