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Author  |
Albandea, D.; Catumba, G.; Ramos, A. |
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Title |
Strong CP problem in the quantum rotor |
Type |
Journal Article |
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Year |
2024 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
110 |
Issue |
9 |
Pages |
094512 - 11pp |
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Abstract |
Recent studies have claimed that the strong CP problem does not occur in QCD, proposing a new order of limits in volume and topological sectors when studying observables on the lattice. In order to shed light on this issue, we study the effect of the topological theta-term on a simple quantum mechanical rotor that allows a lattice description. The topological susceptibility and the theta-dependence of the energy spectrum are both computed using local lattice correlation functions. The sign problem is overcome by considering Taylor expansions in theta, exploiting automatic differentiation methods for Monte Carlo processes. Our findings confirm the conventional wisdom on the strong CP problem. |
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Address |
[Albandea, D.; Catumba, G.; Ramos, A.] Inst Fis Corpuscular CSIC UVEG, Edificio Inst Invest,Apartado Correos 22085, E-46071 Valencia, Spain, Email: david.albandea@uv.es; |
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Amer Physical Soc |
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English |
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ISSN |
2470-0010 |
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Notes |
WOS:001365499800001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
6350 |
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Author |
Albandea, D.; Del Debbio, L.; Hernandez, P.; Kenway, R.; Marsh Rossney, J.; Ramos, A. |
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Title |
Learning trivializing flows |
Type |
Journal Article |
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Year |
2023 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
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Volume |
83 |
Issue |
7 |
Pages |
676 - 14pp |
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Abstract |
The recent introduction of machine learning techniques, especially normalizing flows, for the sampling of lattice gauge theories has shed some hope on improving the sampling efficiency of the traditional hybrid Monte Carlo (HMC) algorithm. In this work we study a modified HMC algorithm that draws on the seminal work on trivializing flows by L & uuml;scher. Autocorrelations are reduced by sampling from a simpler action that is related to the original action by an invertible mapping realised through Normalizing Flows models with a minimal set of training parameters. We test the algorithm in a f(4) theory in 2D where we observe reduced autocorrelation times compared with HMC, and demonstrate that the training can be done at small unphysical volumes and used in physical conditions. We also study the scaling of the algorithm towards the continuum limit under various assumptions on the network architecture. |
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Address |
[Albandea, D.; Hernandez, P.; Ramos, A.] Edificio Inst Invest, IFIC CSIC UVEG, Apt 22085, Valencia 46071, Spain, Email: david.albandea@uv.es |
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Springer |
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English |
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ISSN |
1434-6044 |
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Notes |
WOS:001066712500003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5698 |
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Author |
Albandea, D.; Hernandez, P.; Ramos, A.; Romero-Lopez, F. |
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Title |
Topological sampling through windings |
Type |
Journal Article |
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Year |
2021 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
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Volume |
81 |
Issue |
10 |
Pages |
873 - 12pp |
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Abstract |
We propose a modification of the Hybrid Monte Carlo (HMC) algorithm that overcomes the topological freezing of a two-dimensional U(1) gauge theory with and without fermion content. This algorithm includes reversible jumps between topological sectors – winding steps – combined with standard HMC steps. The full algorithm is referred to as winding HMC (wHMC), and it shows an improved behaviour of the autocorrelation time towards the continuum limit. We find excellent agreement between the wHMC estimates of the plaquette and topological susceptibility and the analytical predictions in the U(1) pure gauge theory, which are known even at finite beta. We also study the expectation values in fixed topological sectors using both HMC and wHMC, with and without fermions. Even when topology is frozen in HMC – leading to significant deviations in topological as well as non-topological quantities – the two algorithms agree on the fixed-topology averages. Finally, we briefly compare the wHMC algorithm results to those obtained with master-field simulations of size L similar to 8 x 10(3). |
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Address |
[Albandea, David; Hernandez, Pilar; Ramos, Alberto; Romero-Lopez, Fernando] UVEG, CSIC, IFIC, Edificio Inst Invest,Apt 22085, Valencia 46071, Spain, Email: David.Albandea@uv.es; |
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Springer |
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English |
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Edition |
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ISSN |
1434-6044 |
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Conference |
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Notes |
WOS:000703880600001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
4979 |
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Author |
Bribian, E.I.; Dasilva Golan, J.; Garcia Perez, M.; Ramos, A. |
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Title |
Memory efficient finite volume schemes with twisted boundary conditions |
Type |
Journal Article |
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Year |
2021 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
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Volume |
81 |
Issue |
10 |
Pages |
951 - 25pp |
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Abstract |
In this paper we explore a finite volume renormalization scheme that combines three main ingredients: a coupling based on the gradient flow, the use of twisted boundary conditions and a particular asymmetric geometry, that for SU (N) gauge theories consists on a hypercubic box of size l(2) x (Nl)(2), a choice motivated by the study of volume independence in large N gauge theories. We argue that this scheme has several advantages that make it particularly suited for precision determinations of the strong coupling, among them translational invariance, an analytic expansion in the coupling and a reduced memory footprint with respect to standard simulations on symmetric lattices, allowing for a more efficient use of current GPU clusters. We test this scheme numerically with a determination of the A parameter in the SU (3) pure gauge theory. We show that the use of an asymmetric geometry has no significant impact in the size of scaling violations, obtaining a value Lambda((MS) over bar)root 8t(0) = 0.603(17) in good agreement with the existing literature. The role of topology freezing, that is relevant for the determination of the coupling in this particular scheme and for large N applications, is discussed in detail. |
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Address |
[Bribian, Eduardo, I; Dasilva Golan, Jorge; Garcia Perez, Margarita] UAM CSIC, Inst Fis Teor, Nicolas Cabrera 13-15,Campus Cantoblanco, Madrid 28049, Spain, Email: jorge.dasilva@uam.es; |
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Springer |
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English |
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ISSN |
1434-6044 |
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Notes |
WOS:000712577800001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
5011 |
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Author |
Catumba, G.; Hiraguchi, A.; Hou, W.S.; Jansen, K.; Kao, Y.J.; Lin, C.J.D.; Ramos, A.; Sarkar, M. |
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Title |
Lattice study of SU(2) gauge theory coupled to four adjoint Higgs fields |
Type |
Journal Article |
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Year |
2024 |
Publication |
Physical Review Research |
Abbreviated Journal |
Phys. Rev. Res. |
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Volume |
6 |
Issue |
4 |
Pages |
043172 - 12pp |
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Abstract |
Gauge theories with matter fields in various representations play an important role in different branches of physics. Recently, it was proposed that several aspects of the pseudogap phase of cuprate superconductors near optimal doping may be explained by an emergent SU(2) gauge symmetry. Around the transition with positive hole doping, one can construct a (2 + 1)-dimensional SU(2) gauge theory coupled to four adjoint scalar fields which gives rise to a rich phase diagram with a myriad of phases having different broken symmetries. We study the phase diagram of this model on the Euclidean lattice using the hybrid Monte Carlo algorithm. We find the existence of multiple broken phases as predicted by previous mean-field studies. Depending on the quartic couplings, the SU(2) gauge symmetry is broken down either to U(1) or Z2 in the perturbative description of the model. We further study the confinement-deconfinement transition in this theory, and find that both the broken phases are deconfining in the range of volumes that we studied. However, there exists a marked difference in the behavior of the Polyakov loop between the two phases. |
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Address |
[Catumba, Guilherme; Ramos, Alberto] Univ Valencia, Inst Fis Corpuscular IFIC, CSIC, Valencia 46071, Spain |
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Publisher |
Amer Physical Soc |
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English |
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Notes |
WOS:001361869800007 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
6351 |
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Author |
Catumba, G.; Ramos, A.; Zaldivar, B. |
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Title |
Stochastic automatic differentiation for Monte Carlo processes |
Type |
Journal Article |
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Year |
2025 |
Publication |
Computer Physics Communications |
Abbreviated Journal |
Comput. Phys. Commun. |
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Volume |
307 |
Issue |
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Pages |
109396 - 13pp |
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Keywords |
Automatic differentiation; Monte Carlo; Lattice field theory; Optimization; Bayesian inference |
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Abstract |
Monte Carlo methods represent a cornerstone of computer science. They allow sampling high dimensional distribution functions in an efficient way. In this paper we consider the extension of Automatic Differentiation (AD) techniques to Monte Carlo processes, addressing the problem of obtaining derivatives (and in general, the Taylor series) of expectation values. Borrowing ideas from the lattice field theory community, we examine two approaches. One is based on reweighting while the other represents an extension of the Hamiltonian approach typically used by the Hybrid Monte Carlo (HMC) and similar algorithms. We show that the Hamiltonian approach can be understood as a change of variables of the reweighting approach, resulting in much reduced variances of the coefficients of the Taylor series. This work opens the door to finding other variance reduction techniques for derivatives of expectation values. |
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Address |
[Catumba, Guilherme; Ramos, Alberto; Zaldivar, Bryan] UVEG, CSIC, IFIC, Edificio Inst Invest,Apt 22085, E-46071 Valencia, Spain, Email: gtelo@ific.uv.es |
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Publisher |
Elsevier |
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English |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0010-4655 |
ISBN |
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Conference |
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Notes |
WOS:001337289000001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
6297 |
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Author |
Dalla Brida, M.; Hollwieser, R.; Knechtli, F.; Korzec, T.; Nada, A.; Ramos, A.; Sint, S.; Sommer, R. |
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Title |
Determination of a(s )(mZ) by the non-perturbative decoupling method |
Type |
Journal Article |
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Year |
2022 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
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Volume |
82 |
Issue |
12 |
Pages |
1092 - 38pp |
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Abstract |
We present the details and first results of a new strategy for the determination of alpha s(mZ) (ALPHA Collaboration et al. in Phys. Lett. B 807:135571, 2020). By simultaneously decoupling 3 fictitious heavy quarks we establish a relation between the A-parameters of three-flavor QCD and pure gauge theory. Very precise recent results in the pure gauge theory (Dalla Brida and Ramos in Eur. Phys. J. C 79(8):720, 2019; Nada and Ramos in Eur Phys J C 81(1):1, 2021) can thus be leveraged to obtain the three flavour A-parameter in units of a common decoupling scale. Connecting this scale to hadronic physics in 3-flavour QCD leads to our result in physical units, A(3)/MS = 336(12) MeV, which translates to alpha s(m(Z)) = 0.11823(84). This is compatible with both the FLAG average (Aoki et al. in FLAG review 2021. arXiv:2111.09849 [hep-lat]) and the previous ALPHA result (ALPHA Collaboration et al., Phys. Rev. Lett. 119(10):102001, 2017), with a comparable, yet still statistics dominated, error. This constitutes a highly non-trivial check, as the decoupling strategy is conceptually very different from the 3-flavour QCD step-scaling method, and so are their systematic errors. These include the uncertainties of the combined decoupling and continuum limits, which we discuss in some detail. We also quantify the correlation between both results, due to some common elements, such as the scale determination in physical units and the definition of the energy scale where we apply decoupling. |
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Address |
[Dalla Brida, Mattia] CERN, Theoret Phys Dept, CH-1211 Geneva 23, Switzerland, Email: alberto.ramos@ific.uv.es |
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Publisher |
Springer |
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Language |
English |
Summary Language |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1434-6044 |
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Conference |
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Notes |
WOS:000893933600003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5448 |
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Author |
Del Debbio, L.; Ramos, A. |
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Title |
Lattice determinations of the strong coupling |
Type |
Journal Article |
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Year |
2021 |
Publication |
Physics Reports |
Abbreviated Journal |
Phys. Rep.-Rev. Sec. Phys. Lett. |
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Volume |
920 |
Issue |
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Pages |
1-71 |
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Keywords |
QCD; Renormalization; Strong coupling; Lattice field theory |
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Abstract |
Lattice QCD has reached a mature status. State of the art lattice computations include u, d, s (and even the c) sea quark effects, together with an estimate of electromagnetic and isospin breaking corrections for hadronic observables. This precise and first principles description of the standard model at low energies allows the determination of multiple quantities that are essential inputs for phenomenology and not accessible to perturbation theory. One of the fundamental parameters that are determined from simulations of lattice QCD is the strong coupling constant, which plays a central role in the quest for precision at the LHC. Lattice calculations currently provide its best determinations, and will play a central role in future phenomenological studies. For this reason we believe that it is timely to provide a pedagogical introduction to the lattice determinations of the strong coupling. Rather than analysing individual studies, the emphasis will be on the methodologies and the systematic errors that arise in these determinations. We hope that these notes will help lattice practitioners, and QCD phenomenologists at large, by providing a self-contained introduction to the methodology and the possible sources of systematic error. The limiting factors in the determination of the strong coupling turn out to be different from the ones that limit other lattice precision observables. We hope to collect enough information here to allow the reader to appreciate the challenges that arise in order to improve further our knowledge of a quantity that is crucial for LHC phenomenology. Crown Copyright & nbsp;(c) 2021 Published by Elsevier B.V. All rights reserved. |
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Address |
[Del Debbio, Luigi] Univ Edinburgh, Sch Phys & Astron, Edinburgh EH9 3JZ, Midlothian, Scotland, Email: luigi.del.debbio@ed.ac.uk; |
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Elsevier |
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English |
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ISSN |
0370-1573 |
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Notes |
WOS:000659901700001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4843 |
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Author |
Dorigo, T. et al; Ramos, A.; Ruiz de Austri, R. |
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Title |
Toward the end-to-end optimization of particle physics instruments with differentiable programming |
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Journal Article |
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Year |
2023 |
Publication |
Reviews in Physics |
Abbreviated Journal |
Rev. Phys. |
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Volume |
10 |
Issue |
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Pages |
100085 - pp |
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Abstract |
The full optimization of the design and operation of instruments whose functioning relies on the interaction of radiation with matter is a super-human task, due to the large dimensionality of the space of possible choices for geometry, detection technology, materials, data-acquisition, and information-extraction techniques, and the interdependence of the related parameters. On the other hand, massive potential gains in performance over standard, “experience-driven” layouts are in principle within our reach if an objective function fully aligned with the final goals of the instrument is maximized through a systematic search of the configuration space. The stochastic nature of the involved quantum processes make the modeling of these systems an intractable problem from a classical statistics point of view, yet the construction of a fully differentiable pipeline and the use of deep learning techniques may allow the simultaneous optimization of all design parameters. |
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Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
6096 |
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Author |
Encarnacion, P.; Feijoo, A.; Mantovani Sarti, V.; Ramos, A. |
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Title |
Femtoscopic study of the S =-1 meson-baryon interaction: K – p, π – Λ, and K plus Ξ – correlations |
Type |
Journal Article |
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Year |
2025 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
111 |
Issue |
11 |
Pages |
114013 - 16pp |
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Abstract |
We study the femtoscopic correlation functions of meson-baryon pairs in the strangeness S = -1 sector, employing unitarized s-wave scattering amplitudes derived from the chiral Lagrangian up to next-to-leading order. For the first time, we deliver predictions on the pi-A and K+E-correlation functions which are feasible to be measured at the Large Hadron Collider. We also demonstrate that the employed model is perfectly capable of reproducing the K-p correlation function data measured by the same collaboration, without the need to modify the coupling strength to the K<overline>0n channel, as has been recently suggested. In all cases, the effects of the source size on the correlation are tested. In addition, we present detailed analysis of the different coupled-channel contributions, together with the quantification of the relative relevance of the different terms in the interaction. These calculations require the knowledge of the so-called production weights, for which we present two novel methods to compute them. |
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Address |
[Encarnacion, P.; Ramos, A.] Univ Barcelona, Dept Fis Quant & Astrofis, Fac Fis, Barcelona, Spain, Email: Pablo.Encarnacion@ific.uv.es; |
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Amer Physical Soc |
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English |
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Series Volume |
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ISSN |
2470-0010 |
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Conference |
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Notes |
WOS:001520726900010 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
6744 |
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