109 research outputs found
The Nab Experiment: A Precision Measurement of Unpolarized Neutron Beta Decay
Neutron beta decay is one of the most fundamental processes in nuclear
physics and provides sensitive means to uncover the details of the weak
interaction. Neutron beta decay can evaluate the ratio of axial-vector to
vector coupling constants in the standard model, , through
multiple decay correlations. The Nab experiment will carry out measurements of
the electron-neutrino correlation parameter with a precision of and the Fierz interference term to
in unpolarized free neutron beta decay. These results, along with a more
precise measurement of the neutron lifetime, aim to deliver an independent
determination of the ratio with a precision of that will allow an evaluation of and sensitively
test CKM unitarity, independent of nuclear models. Nab utilizes a novel, long
asymmetric spectrometer that guides the decay electron and proton to two large
area silicon detectors in order to precisely determine the electron energy and
an estimation of the proton momentum from the proton time of flight. The Nab
spectrometer is being commissioned at the Fundamental Neutron Physics Beamline
at the Spallation Neutron Source at Oak Ridge National Lab. We present an
overview of the Nab experiment and recent updates on the spectrometer,
analysis, and systematic effects.Comment: Presented at PPNS201
Neutron Decay Correlations in the Nab Experiment
The Nab experiment will measure the correlation a between the momenta of the beta particle and antineutrino in neutron decay as well as the Fierz term b which distorts the beta spectrum
Self-Organization and Complex Networks
In this chapter we discuss how the results developed within the theory of
fractals and Self-Organized Criticality (SOC) can be fruitfully exploited as
ingredients of adaptive network models. In order to maintain the presentation
self-contained, we first review the basic ideas behind fractal theory and SOC.
We then briefly review some results in the field of complex networks, and some
of the models that have been proposed. Finally, we present a self-organized
model recently proposed by Garlaschelli et al. [Nat. Phys. 3, 813 (2007)] that
couples the fitness network model defined by Caldarelli et al. [Phys. Rev.
Lett. 89, 258702 (2002)] with the evolution model proposed by Bak and Sneppen
[Phys. Rev. Lett. 71, 4083 (1993)] as a prototype of SOC. Remarkably, we show
that the results obtained for the two models separately change dramatically
when they are coupled together. This indicates that self-organized networks may
represent an entirely novel class of complex systems, whose properties cannot
be straightforwardly understood in terms of what we have learnt so far.Comment: Book chapter in "Adaptive Networks: Theory, Models and Applications",
Editors: Thilo Gross and Hiroki Sayama (Springer/NECSI Studies on Complexity
Series
Fundamental Neutron Physics: a White Paper on Progress and Prospects in the US
Fundamental neutron physics, combining precision measurements and theory,
probes particle physics at short range with reach well beyond the highest
energies probed by the LHC. Significant US efforts are underway that will probe
BSM CP violation with orders of magnitude more sensitivity, provide new data on
the Cabibbo anomaly, more precisely measure the neutron lifetime and decay, and
explore hadronic parity violation. World-leading results from the US
Fundamental Neutron Physics community since the last Long Range Plan, include
the world's most precise measurement of the neutron lifetime from UCN,
the final results on the beta-asymmetry from UCNA and new results on hadronic
parity violation from the NPDGamma and n-He runs at the FNPB (Fundamental
Neutron Physics Beamline), precision measurement of the radiative neutron decay
mode and n-He at NIST. US leadership and discovery potential are ensured
by the development of new high-impact experiments including BL3, Nab, LANL nEDM
and nEDM@SNS. On the theory side, the last few years have seen results for the
neutron EDM from the QCD term, a factor of two reduction in the
uncertainty for inner radiative corrections in beta-decay which impacts CKM
unitarity, and progress on {\it ab initio} calculations of nuclear structure
for medium-mass and heavy nuclei which can eventually improve the connection
between nuclear and nucleon EDMs. In order to maintain this exciting program
and capitalize on past investments while also pursuing new ideas and building
US leadership in new areas, the Fundamental Neutron Physics community has
identified a number of priorities and opportunities for our sub-field covering
the time-frame of the last Long Range Plan (LRP) under development. This white
paper elaborates on these priorities.Comment: arXiv admin note: text overlap with arXiv:2304.0345
Recommended from our members
Chamber-based insights into the factors controlling epoxydiol (IEPOX) secondary organic aerosol (SOA) yield, composition, and volatility
We present measurements utilizing the Filter Inlet for Gases and Aerosols (FIGAERO) applied to chamber measurements of isoprene-derived epoxydiol (IEPOX) reactive uptake to aqueous acidic particles and associated secondary organic aerosol (SOA) formation. Similar to recent field observations with the same instrument, we detect two molecular components desorbing from the IEPOX SOA in high abundance: C5H12O4 and C5H10O3. The thermal desorption signal of the former, presumably 2-methyltetrols, exhibits two distinct maxima, suggesting it arises from at least two different SOA components with significantly different effective volatilities. Isothermal evaporation experiments illustrate that the most abundant component giving rise to C5H12O4 is semi-volatile, undergoing nearly complete evaporation within 1 h while the second, less volatile component remains unperturbed and even increases in abundance. We thus confirm, using controlled laboratory studies, recent analyses of ambient SOA measurements showing that IEPOX SOA is of very low volatility and commonly measured IEPOX SOA tracers such as C5H12O4 and C5H10O3, presumably 2-methyltetrols and C5-alkene triols or 3-MeTHF-3,4-diols, result predominantly from thermal decomposition in the FIGAERO-CIMS. We infer that other measurement techniques using thermal desorption or prolonged heating for analysis of SOA components may also lead to reported 2-methyltetrols and C5-alkene triols or 3-MeTHF-3,4-diol structures. We further show that IEPOX SOA volatility continues to evolve via acidity-enhanced accretion chemistry on the timescale of hours, potentially involving both 2-methyltetrols and organosulfates.Peer reviewe
Fundamental Symmetries, Neutrons, and Neutrinos (FSNN): Whitepaper for the 2023 NSAC Long Range Plan
This whitepaper presents the research priorities decided on by attendees of
the 2022 Town Meeting for Fundamental Symmetries, Neutrons and Neutrinos, which
took place December 13-15, 2022 in Chapel Hill, NC, as part of the Nuclear
Science Advisory Committee (NSAC) 2023 Long Range Planning process. A total of
275 scientists registered for the meeting. The whitepaper makes a number of
explicit recommendations and justifies them in detail
The present and future of QCD
This White Paper presents an overview of the current status and future perspective of QCD research, based on the community inputs and scientific conclusions from the 2022 Hot and Cold QCD Town Meeting. We present the progress made in the last decade toward a deep understanding of both the fundamental structure of the sub-atomic matter of nucleon and nucleus in cold QCD, and the hot QCD matter in heavy ion collisions. We identify key questions of QCD research and plausible paths to obtaining answers to those questions in the near future, hence defining priorities of our research over the coming decades
Patellofemoral pain syndrome (PFPS): a systematic review of anatomy and potential risk factors
Patellofemoral Pain Syndrome (PFPS), a common cause of anterior knee pain, is successfully treated in over 2/3 of patients through rehabilitation protocols designed to reduce pain and return function to the individual. Applying preventive medicine strategies, the majority of cases of PFPS may be avoided if a pre-diagnosis can be made by clinician or certified athletic trainer testing the current researched potential risk factors during a Preparticipation Screening Evaluation (PPSE). We provide a detailed and comprehensive review of the soft tissue, arterial system, and innervation to the patellofemoral joint in order to supply the clinician with the knowledge required to assess the anatomy and make recommendations to patients identified as potentially at risk. The purpose of this article is to review knee anatomy and the literature regarding potential risk factors associated with patellofemoral pain syndrome and prehabilitation strategies. A comprehensive review of knee anatomy will present the relationships of arterial collateralization, innervations, and soft tissue alignment to the possible multifactoral mechanism involved in PFPS, while attempting to advocate future use of different treatments aimed at non-soft tissue causes of PFPS
- …