1,721,179 research outputs found
Masses and decay constants of D*(s) and B*(s) mesons with Nf=2+1+1 twisted mass fermions
No full textWe present a lattice calculation of the masses and decay constants of D*(s) and B*(s) mesons using the gauge configurations produced by the European Twisted Mass Collaboration (ETMC) with Nf=2+1+1 dynamical quarks at three values of the lattice spacing a~(0.06-0.09) fm. Pion masses are simulated in the range Mpi=(210-450) MeV, while the strange and charm sea-quark masses are close to their physical values. We compute the ratios of vector to pseudoscalar masses and decay constants for various values of the heavy-quark mass mh in the range 0.7mcphysmh3mcphys. In order to reach the physical b-quark mass, we exploit the heavy quark effective theory prediction that, in the static limit of infinite heavy-quark mass, the considered ratios are equal to one. At the physical point our results are MD*/MD=1.0769(79), MD*sMDs=1.0751(56), fD*/fD=1.078(36), fD*s/fDs=1.087(20), MB*/MB=1.0078(15), MB*s/MBs=1.0083(10), fB*/fB=0.958(22) and fB*s/fBs=0.974(10). Combining them with the experimental values of the pseudoscalar meson masses (used as input to fix the quark masses) and the values of the pseudoscalar decay constants calculated by ETMC, we get MD*=2013(14), MD*s=2116(11), fD*=223.5(8.4), fD*s=268.8(6.6), MB*=5320.5(7.6), MB*s=5411.36(5.3), fB*=185.9(7.2) and fB*s=223.1(5.4) MeV
Thermodynamics and microscopic theory: an educational proposal for the high school
Full text linkWe present an educational proposal which aims to illustrate the elegant,
refined and coherent physics contained in Thermodynamics, through a path which
assigns to the microscopic description of the physical systems a constantly
privileged role. This approach allows to reach a simple and, at the same time,
deep understanding of the laws of Thermodynamics, while still emphasizing their
great generality, which permits their application to all macroscopic systems,
from simple gases to black holes, arriving to characterize the evolution of the
entire Universe.Comment: Communications: SIF Congress 2022. 6 page
Electromagnetic and strong isospin-breaking corrections to the muon g-2 from lattice QCD+QED
Full text linkWe present a lattice calculation of the leading-order electromagnetic and strong isospin-breaking corrections to the hadronic vacuum polarization (HVP) contribution to the anomalous magnetic moment of the muon. We employ the gauge configurations generated by the European Twisted Mass Collaboration with Nf=2+1+1 dynamical quarks at three values of the lattice spacing (a≃0.062,0.082,0.089 fm) with pion masses between ≃210 and ≃450 MeV. The results are obtained by adopting the RM123 approach in the quenched-QED approximation, which neglects the charges of the sea quarks. Quark disconnected diagrams are not included. After the extrapolations to the physical pion mass and to the continuum and infinite-volume limits the contributions of the light, strange, and charm quarks are, respectively, equal to δaμHVP(ud)=7.1(2.5)×10-10, δaμHVP(s)=-0.0053(33)×10-10, and δaμHVP(c)=0.0182(36)×10-10. At leading order in αem and (md-mu)/ΛQCD we obtain δaμHVP(udsc)=7.1(2.9)×10-10, which is currently the most accurate determination of the isospin-breaking corrections to aμHVP
Tensor form factor of D →π (K) ν and D →π (K) decays with Nf=2+1+1 twisted-mass fermions
No full textWe present the first lattice Nf=2+1+1 determination of the tensor form factor fTDπ(K)(q2) corresponding to the semileptonic D→π(K) nu; and rare D→π(K) decays as a function of the squared four-momentum transfer q2. Together with our recent determination of the vector f+Dπ(K)(q2) and scalar f0Dπ(K)(q2) form factors, we complete the set of hadronic matrix elements regulating the semileptonic D→π(K) ν and rare D→π(K) transitions within and beyond the standard model, when a nonzero tensor coupling is possible. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with Nf=2+1+1 flavors of dynamical quarks, which include in the sea, besides two light mass-degenerate quarks, also the strange and charm quarks with masses close to their physical values. We simulated at three different values of the lattice spacing and with pion masses as small as 220 MeV and with the valence heavy quark in the mass range from ≃0.7mcphys to ≃1.2mcphys. The matrix elements of the tensor current are determined for a plethora of kinematical conditions in which parent and child mesons are either moving or at rest. As in the case of the vector and scalar form factors, Lorentz symmetry breaking due to hypercubic effects is clearly observed also in the data for the tensor form factor and included in the decomposition of the current matrix elements in terms of additional form factors. After the extrapolations to the physical pion mass and to the continuum and infinite volume limits, we determine the tensor form factor in the whole kinematical region from q2=0 up to qmax2=(MD-Mπ(K))2 accessible in the experiments. A set of synthetic data points, representing our results for fTDπ(K)(q2) for several selected values of q2, is provided and the corresponding covariance matrix is also available. At zero four-momentum transfer, we get fTDπ(0)=0.506 (79) and fTDK(0)=0.687 (54), which correspond to fTDπ(0)/f+Dπ(0)=0.827 (114) and fTDK(0)/f+DK(0)=0.898 (50)
Masses, decay constants and HQE matrix elements of pseudoscalar and vector heavy-light mesons in LQCD
No full textWe present a precise lattice computation of masses and decay constants of pseudoscalar and vector heavy-light mesons with m l = m u/d, m s and m h in the range (m c, ∼ 3m c). We employ the ETMC gauge configurations with both N f = 2 and N f = 2 + 1 + 1 dynamical quarks and the ETMC ratio method to reach the b-quark mass. In the case of the vector decay constants an unusual quenching effect of the strange quark is observed. Specific masses combinations are then analyzed in terms of the Heavy Quark Expansion (HQE) to extract matrix elements up to dimension-6, including , and and with a good precision. These parameters play a crucial role in the inclusive determination of the V ub and V cb matrix elements
Rotated twisted-mass: a convenient regularization scheme for isospin breaking QCD and QED lattice calculations
Full text linkWe propose a scheme of lattice twisted-mass fermion regularization which is particularly convenient for application to isospin breaking (IB) QCD and QED calculations, based in particular on the so called RM123 approach, in which the IB terms of the action are treated as a perturbation. The main, practical advantage of this scheme is that it allows the calculation of IB effects on some mesonic observables, like e.g. the pi+ - pi0 mass splitting, using lattice correlation functions in which the quark and antiquark fields in the meson are regularized with opposite values of the Wilson parameter r. These correlation functions are found to be affected by much smaller statistical fluctuations, with respect to the analogous functions in which quark and antiquark fields are regularized with the same value of r. Two numerical application of this scheme, that we call "rotated twisted-mass", within pure QCD and QCD+QED respectively, are also provided for illustration
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 hadronic decay rate of the τ lepton from lattice QCD
Full text linkInclusive hadronic decays of the τ lepton are very interesting from the phenomenological point of view since they give access to the Cabibbo-Kobayashi-Maskawa matrix elements Vud and Vus. In this paper, for the first time, by employing the method of [M. Hansen, A. Lupo, and N. Tantalo, Phys. Rev. D 99, 094508 (2019)] for hadronic smeared spectral densities, we compute on the lattice the inclusive decay rate of the processes τ→Xudντ, where Xud is a generic hadronic state with u ̄d flavor quantum numbers. Our computation, which avoids any recourse to operator product expansion and/or perturbative approximations, is carried out in isospin symmetric Nf=2+1+1 lattice QCD at physical quark masses, using ensembles produced by the Extended Twisted Mass Collaboration at three lattice spacings and two volumes. All uncertainties, except for isospin breaking effects, are taken into account and a result with a subpercent error is obtained for |Vud|, which is nicely consistent with the current world average. These findings validate our approach and also motivate the inclusion of isospin breaking corrections and its extension to the inclusive decay τ→Xusντ, paving the way toward a high-precision first-principles determination of |Vus| and |Vud| from inclusive τ decay
Variations on the Author
Full text link“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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