1,720,996 research outputs found
Inclusive semileptonic B(s)-meson decays from Lattice QCD
No full textThe Standard Model (SM) is the most comprehensive framework to describe our current understanding of the known particle physics world. However, its limitations are well known as it cannot explain all observed phenomena. Discrepancies between measurements of SM observables and theoretical predictions guide us in the search for new physics and in extending the Standard Model. One intriguing puzzle is the long-standing tension between the inclusive and exclusive determinations of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements |Vcb| and |Vub|, respectively. Semileptonic decays of B mesons constitute the main channel for the extraction of these parameters, and therefore represent crucial processes to address and investigate this tension. As B-physics experiments perform measurements and collect new data to study the B-meson properties, it becomes essential to address and understand the tension, and to provide more precise theoretical inputs to further improve our predictions. In this work we address the nonperturbative calculation of the inclusive decay rate of semileptonic B(s)-meson decays from lattice QCD. This type of computation may eventually provide new insight into the aforementioned tension in the determination of |Vcb| and |Vub|. We also address the computation of lepton energy and hadronic mass moments, which may provide ground for comparing lattice techniques with continuum approaches such as OPE and perturbation theory. We present results from a pilot lattice computation for Bs → Xc lνl, where the initial b quark described by the relativistic-heavy-quark (RHQ) formalism on the lattice and other valence quarks discretised with domain-wall fermions are simulated approximately at their physical quark masses. We compare different methods for computing the decay rate and the moments from lattice data of Euclidean four-point functions, namely approaches based on expansions in Chebyshev polynomials, approaches based on the Backus-Gilbert technique and also combinations of both. We find that the results we obtain are in excellent agreement. We further test our setup studying the ground-state meson limit and how much it dominates the inclusive decay rate. We indicate possible strategies towards a computation with a more comprehensive error budget and leave a proper determination of the systematics effects for future studies
Dataset supporting the University of Southampton Doctoral Thesis "Inclusive semileptonic B(s)-meson decays from Lattice QCD"
No full textDataset supporting the Doctoral Thesis "Inclusive semileptonic B(s)-meson decays from Lattice QCD".
Dataset generated to study inclusive (and exclusive) semileptonic processes for B(s) mesons. Results obtained from these data have been published in https://link.springer.com/article/10.1007/JHEP07(2023)145, which represents the key publication of this PhD work.
This dataset contains data corresponding to the two-point, three-point and four-point correlation functions (correlators)
necessary to study the semileptonic decays of Bs mesons in Lattice QCD.
The data are generated through numerical simulations on a 24^3 X 64 Lattice using the ensemble configuration provided by the RBC/UKQCD collaboration.
The thesis provide more details as follows. A generic introduction to Lattice QCD is provided in Chapter 2 of the thesis.
The operators necessary to build the correlation functions for the process considered are discussed in Chapter 4. And the details of the actual simulation are listed in Chapter 5.
The data have been generated with the Grid (https://github.com/paboyle/Grid) and Hadrons (https://github.com/aportelli/Hadrons) software packages using the DiRAC Extreme Scaling service at the University of Edinburgh,
operated by the Edinburgh Parallel Computing Centre on behalf of the STFC DiRAC HPC Facility (www.dirac.ac.uk).</span
A variance reduction technique for hadronic correlators with partially twisted boundary conditions
No full textPartially twisted boundary conditions are widely used for improving the momentum resolution in lattice computations of hadronic correlation functions. The method is however expensive since every additional twist requires computing additional propagators. We propose a novel variance reduction technique that exploits statistical correlations to reduce the overall cost for computing correlators with additional twist angles. We explain and demonstrate the method for meson 2pt and 3pt functions.Partially twisted boundary conditions are widely used for improving the momentum resolution in lattice computations of hadronic correlation functions. The method is however expensive since every additional twist requires computing additional propagators. We propose a novel variance reduction technique that exploits statistical correlations to reduce the overall cost for computing correlators with additional twist angles. We explain and demonstrate the method for meson 2pt and 3pt functions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Inclusive semi-leptonic <i>B</i><sub>(s)</sub> mesons decay at the physical<i> b</i> quark mass
No full textWe address the non-perturbative calculation of the decay rate of inclusive semi-leptonic mesons decays from lattice QCD. Precise theoretical Standard Model predictions are key ingredients in searches for new physics. This type of computation may eventually provide new insight into the long-standing tension between the inclusive and exclusive determinations of the CKM matrix elements and . We perform a pilot lattice computation for and improve on existing techniques. The valence-quark masses in our simulations are approximately physical for the domain-wall strange and charm quarks as well as for the bottom quark, for which we use a relativistic heavy quark effective action. We report on our progress and discuss future plans towards a first study with fully controlled systematic effects
Studies on finite-volume effects in the inclusive semileptonic decays of charmed mesons
No full textWe report on the calculation of the inclusive semileptonic decay of the Ds meson on the lattice. We simulate the Ds→Xsℓνℓ process with Möbius domain-wall charm and strange quarks, whose masses were approximately tuned to the physical values. We cover the whole kinematical region. The focus of this work is on the systematic error due to finite-volume effects. We construct a model of two-body final states to describe the data on a finite volume lattice of L≃0.055fm to investigate the extrapolation to the infinite-volume limit
Allergists and COVID-vaccine: which is the actual risk of reactions in allergic patients?
No full textUpdates on inclusive charmed and bottomed meson decays from the lattice
No full textWith the development of lattice QCD in recent years, a determination of decay rates for inclusive semileptonic decays from lattice correlators now seems viable. We report on the calculation of the inclusive semileptonic decay of the meson on the lattice. We simulate the process with M\"obius domain-wall charm and strange quarks, whose masses were approximately tuned to the physical values. We cover the whole kinematical region. We present a general overview on how the inclusive decays are treated on the lattice and discuss ongoing challenges, such as the estimation of systematic errors and future prospects of the project
The risk of anaphylaxis on holidays
No full textPurpose of review: The goal of this review is to summarize the potential causes of anaphylaxis in the different holiday contexts, providing practical suggestions aimed to mitigate the stress challenged by allergic patients because of unfamiliar situations. Recent findings: A regard was reserved to potential food triggers, particularly uncommon ones and typical of certain destinations, and to arthropods responsible for anaphylaxis. Summary: This review highlights the potential risk of anaphylaxis due to the unusual contexts more experienced during holidays (i.e., travels, outdoor activities and eating out). Moreover, it underlines the need for a further allergological education in these cases, in order to prepare allergic patients to avoid and manage undesired situations
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