We present the QCD simulation of the first gauge ensemble of two degenerate light quarks, a strange and a charm quark with all quark masses tuned to their physical values within the twisted mass ...fermion formulation. Results for the pseudoscalar masses and decay constants confirm that the produced ensemble is indeed at the physical parameters of the theory. This conclusion is corroborated by a complementary analysis in the baryon sector. We examine cutoff and isospin breaking effects and demonstrate that they are suppressed through the presence of a clover term in the action.
We present a comprehensive investigation of light meson physics using maximally twisted mass fermions for
N
f
= 2 mass-degenerate quark flavours. By employing four values of the lattice spacing, ...spatial lattice extents ranging from 2.0 fm to 2.5 fm and pseudo scalar masses in the range 280 ≲
m
PS
≲ 650MeV we control the major systematic effects of our calculation. This enables us to confront our
N
f
= 2 data with SU(2) chiral perturbation theory and extract low energy constants of the effective chiral Lagrangian and derived quantities, such as the light quark mass.
Orbital inflammatory pseudotumor is considered a non-neoplastic inflammatory process. The finding of clonality of B or T-cell receptors in cases pathologically diagnosed as orbital inflammatory ...pseudotumor has unknown clinicopathologic significance. We sought to investigate potential B and T-cell clonality and concomitant diseases in cases pathologically diagnosed as orbital inflammatory pseudotumor.
Cases diagnosed as orbital inflammatory pseudotumor at our institution were retrospectively analyzed. Hematoxylin and eosinstained slides, immunohistochemically stained slides and polymerase chain reactions on cell block material for the investigation of clonality of B and T-cell receptors were evaluated, to confirm the diagnosis and investigate the prevalence of concomitant diseases.
A total of 13 cases showing characteristic histopathologic features of orbital inflammatory pseudotumor were identified. CD138, IgG, and IgG4 showed varying numbers of plasma cells in each case, with 5 cases (5/13, 38%) exhibiting relative increase in the presence of IgG4 plasma cells. However, no cases showed diagnostic findings of IgG4-related disease (IgG4-RD). polymerase chain reactions analysis showed clonal B-cell populations in 2 cases (2/13, 15%). No cases showed anaplastic lymphoma kinase expression by immunohistochemistry. There were no clinical reports of progression to lymphoma or development of systemic IgG4-RD in any of the patients (average follow-up of 300 days), with 38% of patients showing systemic autoimmune conditions.
A small but significant percentage of typical orbital inflammatory pseudotumor on histology showed B-cell clonality on polymerase chain reactions analysis of B-cell receptors, or features suggestive, but not diagnostic of IgG4-RD. Close follow-up of these patients to identify development of lymphoma, systemic IgG4-RD, or other rheumatologic conditions may be clinically warranted.
We present a general strategy aimed at generating Nf = 2+1+1 configurations with quarks at their physical mass using maximally twisted mass fermions to ensure automatic O(a) improvement, in the ...presence of a clover term tuned to reduce the charged to neutral pion mass difference. The target system, for the moment, is a lattice of size 643 × 128 with a lattice spacing a ~ 0:08 fm. We show preliminary results on the pion and kaon mass and decay constants.
In this contribution we lay down a lattice setup that allows for the nonperturbative study of a field theoretical model where a SU(2) fermion doublet, subjected to non-Abelian gauge interactions, is ...also coupled to a complex scalar field doublet via a Yukawa and an “irrelevant” Wilson-like term. Using naive fermions in quenched approximation and based on the renormalizedWard identities induced by purely fermionic chiral transformations, lattice observables are discussed that enable: a) in theWigner phase, the determinations of the critical Yukawa coupling value where the purely fermionic chiral transformation become a symmetry up to lattice artifacts; b) in the Nambu-Goldstone phase of the resulting critical theory, a stringent test of the actual generation of a fermion mass term of non-perturbative origin. A soft twisted fermion mass term is introduced to circumvent the problem of exceptional configurations, and observables are then calculated in the limit of vanishing twisted mass.
Based on a recent proposal according to which elementary particle masses could be generated by a non-perturbative dynamical phenomenon, alternative to the Higgs mechanism, we carry out lattice ...simulations of a model where a non-abelian strongly interacting fermion doublet is also coupled to a doublet of complex scalar fields via a Yukawa and an “irrelevant" Wilson-like term. In this pioneering study we use naive fermions and work in the quenched approximation. We present preliminary numerical results both in the Wigner and in the Nambu-Goldstone phase, focusing on the observables relevant to check the occurrence of the conjectured dynamical fermion mass generation effect in the continuum limit of the critical theory in its spontaneously broken phase.
We present a first-principles lattice QCD investigation of the R ratio between the e^{+}e^{-} cross section into hadrons and into muons. By using the method of Ref. 1, that allows one to extract ...smeared spectral densities from Euclidean correlators, we compute the R ratio convoluted with Gaussian smearing kernels of widths of about 600 MeV and central energies from 220 MeV up to 2.5 GeV. Our theoretical results are compared with the corresponding quantities obtained by smearing the KNT19 compilation 2 of R-ratio experimental measurements with the same kernels and, by centering the Gaussians in the region around the ρ-resonance peak, a tension of about 3 standard deviations is observed. From the phenomenological perspective, we have not included yet in our calculation QED and strong isospin-breaking corrections, and this might affect the observed tension. From the methodological perspective, our calculation demonstrates that it is possible to study the R ratio in Gaussian energy bins on the lattice at the level of accuracy required in order to perform precision tests of the standard model.
We present results for the renormalization constants of bilinear quark operators obtained by using the tree-level Symanzik improved gauge action and the N f = 2 twisted mass fermion action at maximal ...twist, which guarantees automatic O(a)-improvement. Our results are also relevant for the corresponding standard (un-twisted) Wilson fermionic action since the two actions only differ, in the massless limit, by a chiral rotation of the quark fields. The scale-independent renormalization constants Z V , Z A and the ratio Z P /Z S have been computed using the RI-MOMapproach, as well as other alternative methods. For Z A and Z P /Z S , the latter are based on both standard twisted mass and Osterwalder-Seiler fermions, while for Z V a Ward Identity has been used. The quark field renormalization constant Z q and the scale dependent renormalization constants Z S , Z P and Z T are determined in the RI-MOM scheme. Leading discretization effects of O(g 2 a 2 ), evaluated in one-loop perturbation theory, are explicitly subtracted from the RI-MOM estimates
Phase Transitions in Particle Physics Aarts, Gert; Aichelin, Joerg; Allton, Chris ...
Progress in particle and nuclear physics,
November 2023, 2023-11-00, Letnik:
133
Journal Article
Recenzirano
Odprti dostop
Phase transitions in a non-perturbative regime can be studied by ab initio Lattice Field Theory methods. The status and future research directions for LFT investigations of Quantum Chromo-Dynamics ...under extreme conditions are reviewed, including properties of hadrons and of the hypothesized QCD axion as inferred from QCD topology in different phases. We discuss phase transitions in strong interactions in an extended parameter space, and the possibility of model building for Dark Matter and Electro-Weak Symmetry Breaking. Methodological challenges are addressed as well, including new developments in Artificial Intelligence geared towards the identification of different phases and transitions.
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