Search

The implementation of the Schwinger mechanism endows gluons with a nonperturbative mass through the formation of special massless poles in the fundamental QCD vertices; due to their longitudinal character, these poles do not cause divergences in on-shell amplitudes, but induce detectable effects in the Green's functions of the theory. Particularly important in this theoretical setup is the three-gluon vertex, whose pole content extends beyond the minimal structure required for the generation of a gluon mass. In the present work we analyze these additional pole patterns by means of two distinct, but ultimately equivalent, methods: the Slavnov-Taylor identity satisfied by the three-gluon vertex, and the nonlinear Schwinger-Dyson equation that governs the dynamical evolution of this vertex. Our analysis reveals that the Slavnov-Taylor identity imposes strict model-independent constraints on the associated residues, preventing them from vanishing. Approximate versions of these constraints are subsequently recovered from the Schwinger-Dyson equation, once the elements responsible for the activation of the Schwinger mechanism have been duly incorporated. The excellent coincidence between the two approaches exposes a profound connection between symmetry and dynamics, and serves as a nontrivial self-consistency test of this particular mass generating scenario., Comment: 39 pages, 10 figures

We study a special Schwinger-Dyson equation in the context of a pure SU(3) Yang-Mills theory, formulated in the background field method. Specifically, we consider the corresponding equation for the vertex that governs the interaction of two background gluons with a ghost-antighost pair. By virtue of the background gauge invariance, this vertex satisfies a naive Slavnov-Taylor identity, which is not deformed by the ghost sector of the theory. In the all-soft limit, where all momenta vanish, the form of this vertex may be obtained exactly from the corresponding Ward identity. This special result is subsequently reproduced at the level of the Schwinger-Dyson equation, by making extensive use of Taylor's theorem and exploiting a plethora of key relations, particular to the background field method. This information permits the determination of the error associated with two distinct truncation schemes, where the potential advantage from employing lattice data for the ghost dressing function is quantitatively assessed., Comment: 29 pages, 9 figures

DIS2022 conference presentation

During LHC's Run-2 the MoEDAL experiment, the LHC's first dedicated search experiment, took over 6 fb^-1 of data at IP8, with p-p and Pb-Pb collisions, operating with 100% efficiency. The LHCC has endorsed the LoI of the MoEDAL Collaboration describing an exciting program to expand the search for Highly Ionizing Particles (HIPs) in p-p and heavy-ion collisions to include feebly ionizing and Long Lived Particle (LLP) messengers of new physics (NP) at LHC's RUN-3 and eventually HL-LHC. In 2021, as part of Phase-1 of the program, the baseline MoEDAL detector was approved by CERN for reinstallation for Run-3 with increased efficiency, lower threshold, a factor of 5 increase in instantaneous luminosity, and, a higher Ecm. MoEDAL will continue the search for HIP avatars of NP with an emphasis on the search for massive, single and multiply electrically charged avatars of BSM physics arising from, eg, supersymmetry, neutrino mass models, L-R symmetry, etc. As part of Phase-1 of the MoEDAL-MAPP project CERN also approved in 2021 the installation of the MoEDAL Apparatus for Penetrating Particles (MAPP) in the UA83 tunnel 100m away from IP8. The MAPP detector has sensitivity to feebly-interacting particles with charge, or effective charge, as low as 10^-3e. Additionally, the MAPP detector, in conjunction with MoEDAL's trapping detector, gives us a unique sensitivity to charged LLPs. MAPP also has some sensitivity to neutral LLPs. In Phase-2 of the project we will instal the MAPP-2 upgrade for the HL-LHC. We envisage that this detector will be deployed in the UGC1 gallery near to IP8. This phase of the experiment is designed to ensure that MoEDAL-MAPP's sensitivity to neutral LLP messengers of BSM physics is competitive and complementary to other planned projects in this arena. Initial MoEDAL plans for the MEDICI facility at the 100 TeV FCC-hh machine will also be briefly presented., Comment: Contribution to Snowmass 2021

We discuss the demise of flavour tagging due to the loss of the particle-antiparticle identity of neutral B-mesons in the Einstein-Podolsky-Rosen correlated states. Such a situation occurs in cases where the CPT operator is ill-defined, as happens, for example, in quantum gravity models with induced decoherence in the matter sector. The time evolution of the perturbed B0-B0bar initial state, as produced in B-factories, is sufficient to generate new two-body states. For flavour specific decays at equal times, we discuss two definite tests of the two body entanglement: (i) search for the would-be forbidden B0 B0 and B0bar B0bar states; (ii) deviations from the indistinguishable probability between the permuted states B0bar B0 and B0 B0bar., Comment: 12 pages LATEX, one eps figure incorporated

In this review we discuss novel phases (quantum critical points occurring only for T=0) in (2+1)-dimensional Abelian gauge theories, which may serve as prototypes for studying the physics of nodal excitations in (underdoped) high temperature superconductors. We pay particular attention to describing the existence of novel phases related to the anomalous breaking of certain symmetries, including unconventional superconducting properties. Although some of the results are rather old, we present them here from a physical perspective not discussed previously in the literature. In this respect we also explore the (in)applicability of some non perturbative approaches on the existence of a critical number of fermion flavours for chiral symmetry breaking in our specific models, which is an issue closely related to the existence of the novel phases mentioned above., Comment: 46 pages, 10 figures. Invited review to appear in 'Recent Research Developments in Physics' (TRN)

The generalization of the pinch technique to all orders in perturbation theory is presented. The effective Green's functions constructed with this procedure are singled out in a unique way through the full exploitation of the underlying Becchi-Rouet-Stora-Tyutin symmetry. A simple all-order correspondence between the pinch technique and the background field method in the Feynman gauge is established., Comment: 10 pages, 4 figures; one reference added, typos corrected; final version to match the pubblished one

We study, at the one loop level, the dominant contributions from a single universal extra dimension to the process (Z\to b\bar{b}). By resorting to the gaugeless limit of the theory we explain why the result is expected to display a strong dependence on the mass of the top-quark, not identified in the early literature. A detailed calculation corroborates this expectation, giving rise to a lower bound for the compactification scale which is comparable to that obtained from the $��$ parameter. An estimate of the subleading corrections is furnished, together with a qualitative discussion on the difference between the present results and those derived previously for the non-universal case., 16 pages, 4 figures, revtex4

Using the pinch technique we construct at one-loop order a neutrino charge radius, which is finite, depends neither on the gauge-fixing parameter nor on the gauge-fixing scheme employed, and is process-independent. This definition stems solely from an effective proper photon-neutrino one-loop vertex, with no reference to box or self-energy contributions. The role of the $WW$ box in this construction is critically examined. In particular it is shown that the exclusion of the effective WW box from the definition of the neutrino charge radius is not a matter of convention but is in fact dynamically realized when the target-fermions are right-handedly polarized. In this way we obtain a unique decomposition of effective self-energies, vertices, and boxes, which separately respect electroweak gauge invariance. We elaborate on the tree-level origin of the mechanism which enforces at one-loop level massive cancellations among the longitudinal momenta appearing in the Feynman diagrams, and in particular those associated with the non-abelian character of the theory. Various issues related to the known connection between the pinch technique and the Background Field Method are further clarified. Explicit closed expressions for the neutrino charge radius are reported., Comment: 26 pages, plain Latex, 7 Figures in a separate ps file

We present a new, model independent method for extracting bounds for the anomalous $��WW$ couplings from hadron collider experiments. At the partonic level we introduce a set of three observables which are constructed from the unpolarized differential cross-section for the process $d\bar{u}\to W^{-}��$ by appropriate convolution with a set of simple polynomials depending only on the center-of-mass angle. One of these observables allows for the direct determination of the anomalous coupling usually denoted by $����$, without any simplifying assumptions, and without relying on the presence of a radiation zero. The other two observables impose two sum rules on the remaining three anomalous couplings. The inclusion of the structure functions is discussed in detail for both $p\bar{p}$ and $pp$ colliders. We show that, whilst for $p\bar{p}$ experiments this can be accomplished straightforwardly, in the $pp$ case one has to resort to somewhat more elaborate techniques, such as the binning of events according to their longitudinal momenta., 15 pages, Latex, 1 figure, uses axodraw

The authors indicate a micromethod for the simultaneous examination of PPA and urease using a modification of the technique of Vassiliadis and Politi [1968]. The micromethod gave satisfactory results for the PPA test; 95 strains of Proteus and 35 strains of Providencia showed positive PPA tests within 4 h. The urease test was also positive for 95 strains of Proteus within 4 h. Strains of Klebsiella and Cloaca producing urease within 4 days by standard tests gave a positive result, by the micromethod, in 5 to 22 h. False positive tests were not observed. The micromethod is useful for the rapid differentiation of Proteus and Providencia. © 1970 S. Karger AG, Basel.

In a previous study (Papavassiliou 1960) it was reported that colicinogenic enterobacteria are rarely found in guinea pig, white rat and white mice faeces. A similar study in dog, sheep and hen faeces showed that no essential differences exist in the distribution of colicinogenic enterobacteria between human, dog, sheep and hen faeces. Some possible explanations of the differences are discussed and methods for ecological study of the colicinogenic enterobacteria in faeces are described in detail. The general conclusions from our studies until now are the following: 1. The frequency of colicinogenic enterobacteria in some groups of animals may be considerably low. 2. The types of colicines produced by animal strains of E. coli do not differ essentially from the types of colicines produced by human strains. © 1963 Springer-Verlag.