Pseudoscalar States Research Articles

Quantum algebra in mixed light pseudoscalar meson states

In this paper, we investigate the entanglement degrees of pseudoscalar meson states via Yangian algebra Y(SU(3)). By making use of the transition effect of generators J of Y(SU(3)), we construct various transition operators, and act with them on the η–π 0–η′ mixing meson state. The entanglement degrees of both the initial state and final state are calculated with the help of entropy theory. The diagrams of entanglement degrees are presented. Our result shows that a state with the desired entanglement degree can be achieved by acting with a properly chosen transition operator on an initial state. Some combinations of generators of Y(SU(3)) make the constitutions of the initial state change, and lead to superpositions of particles with different electrical charges. This sheds new light on the connections among quantum information, particle physics and Yangian algebra.

Analysis of the X(1835) as a Baryonium State with the Bethe—Salpeter Equation

We take the X(1835) as a pseudoscalar baryonium state, and calculate the mass spectrum of the baryon-antibaryon bound states pp̄, ΣΣ̄, ΞΞ̄, and ΛΛ̄ in the framework of the Bethe—Salpeter equation with a phenomenological potential. The numerical results indicate the pp̄, ΣΣ̄ and ΞΞ̄ bound states may exist, and the X(1835) can be tentatively identified as the pp̄ bound state.

Simulation of 4d $\mathcal{N}=1$ supersymmetric Yang–Mills theory with Symanzik improved gauge action and stout smearing

We report on the results of a numerical simulation concerning the low-lying spectrum of four-dimensional N=1 SU(2) Supersymmetric Yang-Mills (SYM) theory on the lattice with light dynamical gluinos. In the gauge sector the tree-level Symanzik improved gauge action is used, while we use the Wilson formulation in the fermion sector with stout smearing of the gauge links in the Wilson-Dirac operator. The ensembles of gauge configurations were produced with the Two-Step Polynomial Hybrid Monte Carlo (TS-PHMC) updating algorithm. We performed simulations on large lattices up to a size of 24^3 x 48 at $\beta=1.6$. Using QCD units with the Sommer scale being set to r_0 = 0.5 fm, the lattice spacing is about a ~ 0.09 fm, and the spatial extent of the lattice corresponds to 2.1 fm. At the lightest simulated gluino mass the spin-1/2 gluino-glue bound state appeared to be considerably heavier than its expected super-partner, the pseudoscalar bound state. Whether supermultiplets are formed remains to be studied in upcoming simulations.

Glueball mass measurements from improved staggered fermion simulations

We present the first $2+1$ flavor spectrum measurements of glueball states using high statistics simulations with improved staggered fermions. We find a spectrum consistent with quenched measurements of scalar, pseudoscalar, and tensor glueball states. The measurements were made using 5000 configurations at a lattice spacing of 0.123 fm and pion mass of 280 MeV and 3000 configurations at 0.092 fm with a pion mass of 360 MeV. We see some evidence of coupling to $2\ensuremath{\pi}$ states. We compare our results with the experimental glueball candidate spectrum as well as quenched glueball estimates.

Investigation of P-wave scalar and S-wave pseudo-scalar charmonia semileptonic transitions to the Ds(D) meson in QCD

In this work, the semileptonic decays of the scalar charmonium state Xc0 and the pseudo scalar charmonia states ηc(1s) and ηc(2s) into Ds and D mesons are analyzed. The form factors of the transitions Xc0 → Ds(D)ℓν and ηc(1s, 2s) → Ds(D)ℓν are calculated within the framework of the three-point QCD sum rules. The results of the form factors are used to estimate the decay widths of the charmonia states into and .

Analysis of the pseudoscalar partner of the Y(4660) and related bound states

In this article, we study the pseudoscalar bound state $\eta_c'f_0(980)$ (irrespective of the hadro-charmonium and the molecular state) with the QCD sum rules. Considering the SU(3) symmetry of the light flavor quarks and the heavy quark symmetry, we also study the bound states $\eta_c'\sigma(400-1200)$, $\eta_b'''f_0(980)$ and $\eta_b'''\sigma(400-1200)$, and make reasonable predictions for their masses.

Pseudoscalar glueball in a chiral Lagrangian model with instanton effect

We study the pseudoscalar glueball ground state in a chiral effective Lagrangian model proposed by 't Hooft, motivated by taking into account the instanton effects, which can describe not only the chiral symmetry breaking, but also the solution of ${U}_{A}(1)$. We study the parameter space allowed by constraints from vacuum conditions and unitary bounds. By considering two scenarios in the ${0}^{++}$ sector, we find that parameter space which can accommodate the ${0}^{\ensuremath{-}+}$ sector is sensitive to the conditions in ${0}^{++}$ sector. From our analysis, it is found that three $\ensuremath{\eta}$ states, i.e. $\ensuremath{\eta}(1295)$, $\ensuremath{\eta}(1405)$, $\ensuremath{\eta}(1475)$, can be the pseudoscalar glueball ground state if we assume that the lightest ${0}^{++}$ glueball ground state has a mass 1710 (or 1500) MeV. While there will be no ${0}^{\ensuremath{-}+}$ glueball candidate ground state found in experiments if we assume that the lightest ${0}^{++}$ glueball ground state has a mass 660 MeV. We also point out the determined instanton density (i.e. the parameter ${k}_{t}$) is consistent with those determined from other methods, e.g. instanton liquid approximation and lattice simulations.

10.1007/s11450-008-3014-3

The process e + e − → τ + τ − v $$ \bar \nu $$ , which is highly sensitive to anomalous Hττ interaction, is investigated within a model involving a new pseudoscalar Higgs boson. It is shown that the problem of separating the contributions of the scalar and pseudoscalar states of the Higgs boson can be solved via taking into account the polarizations of final-state particles. The inclusion of cascade tau-lepton decays makes it possible to determine reliably the CP state of the Higgs boson and to pinpoint the magnitude and sign of respective coupling constants.

Unconventional phenomenology of a minimal two-Higgs-doublet model

Two-Higgs-doublet models (2HDM) are simple extensions of the Standard Model (SM) where the scalar sector is enlarged by adding a weak doublet. As a result, the Higgs potential depends in general on several free parameters which have to be carefully chosen to give predictions consistent with the current precision data. We consider a 2HDM invariant under a twisted custodial symmetry and depending only on three extra parameters beyond the SM ones. This model naturally features an inverted mass spectrum with a light pseudoscalar state and a heavy SM-like Higgs boson. We thoroughly analyze direct and indirect constraints and present a few unconventional though promising signatures at the LHC.

Radiative and leptonic decays of the pseudoscalar charmonium stateηc

The radiative and leptonic decays of ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ and ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}$ are studied. For a ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ decay, the second-order electromagnetic tree-level diagram gives the leading contribution. The decay rate of ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ is calculated, the prediction is in good agreement with the experimental data. For ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}$, both the tree and loop diagrams are calculated. The analysis shows that the loop contribution dominates; the contribution of tree diagram with a ${Z}^{0}$ intermediate state can only modify the decay rate by less than 1%. The prediction of the branching ratios of ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ and ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ are very tiny within the standard model. The smallness of these predictions within the standard model makes the leptonic decays of ${\ensuremath{\eta}}_{c}$ sensitive to physics beyond the standard model. Measurement of the leptonic decay may give information about new physics.

Determining the CP parity of Higgs bosons at the LHC in the τ to 1-prong decay channels

We propose a method for determining the CP nature of a neutral Higgs boson or spin-zero resonance ϕ at the CERN Large Hadron Collider (LHC) in its ϕ → τ − τ + decay channel. The method can be applied to any 1-prong τ-decay mode, which comprise the majority of the τ-lepton decays. The proposed observables allow to discriminate between pure scalar and pseudoscalar Higgs-boson states and/or between a CP-conserving and CP-violating Higgs sector. We show for the decays τ → π ν τ that the method maintains its discriminating power when measurement uncertainties are taken into account. The method will be applicable also at a future linear e + e − collider.

Exploration of a physical picture for the QCD scalar channel

A generalized linear sigma model is employed to study the quark structure of low lying scalar as well as pseudoscalar states. The model allows the possible mixing of quark anti-quark states with others made of two quarks and two antiquarks but no a priori assumption is made about the quark contents of the predicted physical states. Effects of SU(3) symmetry breaking are included. The lighter conventional pseudoscalars turn out to be primarily of two quark type whereas the lighter scalars have very large four quark admixtures.

Some consequences of a Higgs triplet

We consider an extension of the scalar sector of the Standard Model with a single complex Higgs triplet X. Such extensions are the most economic, model-independent way of generating neutrino masses through triplet interactions. We show that a term like a0ΦΦX† must be included in the most general potential of such a scenario in order to avoid a massless neutral physical scalar. We also demonstrate that a0 must be real, thus ruling out any additional source of CP violation. We then examine the implications of this term in the mass matrices of the singly and doubly charged scalar, neutral scalar and pseudoscalar fields. We find that, for small values of a0/v2, where v2 is the triplet vev, the spectrum allows the decay of heavier scalars into lighter ones via gauge interactions. For large a0/v2, the doubly charged, singly charged and neutral pseudoscalar bosons become practically degenerate, while the even-parity neutral scalars remain considerably lighter, thus emphasizing the possibility of decay of the singly charged or neutral pseudoscalar states into the neutral scalars. Constraints from the ρ-parameter are used to find nontrivial limits on the charged Higgs mass depending on a0. We also study the couplings of the various physical states in this scenario. For small values of |a0|/v2, we find the lightest neutral scalar field to be triplet dominated, and thus having extremely suppressed interactions with fermion as well as gauge–boson pairs.

On the distances between entangled pseudoscalar mesons states

Entangled states of pseudoscalar mesons represent a very interesting tool for studying foundations of quantum mechanics, e.g. for testing Bell inequalities. Recently, they also emerged as a test bench for quantum information protocols. On the other hand, from a quantum information point of view, the characterization of the distance between two quantum states is a topic of the utmost importance. In this letter, with the purpose of providing a useful tool for further investigations, we address the problem of which distance allows a better discrimination between density matrices appearing in pseudoscalar phenomenology.

Determination of the CP properties of the Higgs boson from data on tau-lepton-decay products in the process e + e − → τ + τ − ν % MathType!MTEF!2!1!+- % feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqeduuDJXwAKb % Yu51MyVXgaiuaacuWF9oGBgaqeaaaa!3CC5! $$ \bar \nu $$

The process e+e− → τ+τ−v\( \bar \nu \), which is highly sensitive to anomalous Hττ interaction, is investigated within a model involving a new pseudoscalar Higgs boson. It is shown that the problem of separating the contributions of the scalar and pseudoscalar states of the Higgs boson can be solved via taking into account the polarizations of final-state particles. The inclusion of cascade tau-lepton decays makes it possible to determine reliably the CP state of the Higgs boson and to pinpoint the magnitude and sign of respective coupling constants.

Quenched lattice calculation of semileptonic heavy-light meson form factors

We calculate, in the continuum limit of quenched lattice QCD, the matrix elements of the heavy-heavy vector current between heavy-light pseudoscalar meson states. We present the form factors for different values of the initial and final meson masses at finite momentum transfer. In particular, we calculate the non-perturbative correction to the differential decay rate of the process B → Dlν including the case of a non-vanishing lepton mass.

Anomaly holography

We consider, in the effective field theory context, anomalies of gauge field theories on a slice of a five-dimensional, anti-de Sitter geometry and their four-dimensional, holographic duals. A consistent effective field theory description can always be found, notwithstanding the presence of the anomalies and without modifying the degrees of freedom of the theory. If anomalies do not vanish, the d = 4 theory contains additional pseudoscalar states, which are either present in the low-energy theory as physical, light states, or are eaten by (would-be massless) gauge bosons. We show that the pseudoscalars ensure that global anomalies of the four-dimensional dual satisfy the 't Hooft matching condition and comment on the relevance for warped models of electroweak symmetry breaking.

Study of resonant processes for multi-pion production in [formula omitted] annihilation

In frame of a phenomenological approach based on Compton-like Feynman amplitudes, we study multi-pion production in antiproton nucleon collisions. The main interest of this reaction is related to the possibility to study the properties of the presumable N¯N atom and of its resonances. For the case of formation of a scalar or pseudoscalar resonant state, with IG(JP)=1−(0±), 0+(0−) numerical results are obtained. The differential cross section in an experimental set-up where the pions invariant mass is measured, is given with explicit dependence on the lepton pair and pions invariant mass.

CALCULATION OF THE Bc LEPTONIC DECAY CONSTANT USING THE SHIFTED N-EXPANSION METHOD

We give a review and present a comprehensive calculation for the leptonic constant fBc of the low-lying pseudoscalar and vector states of Bc-meson in the framework of static and QCD-motivated nonrelativistic potential models taking into account the one-loop and two-loop QCD corrections in the short distance coefficient that governs the leptonic constant of Bc quarkonium system. Further, we use the scaling relation to predict the leptonic constant of the nS-states of the [Formula: see text] system. Our results are compared with other models to gauge the reliability of the predictions and point out differences.

Flavor changing neutral currents in supersymmetric multi-Higgs doublet models

We conduct a general discussion of supersymmetric models with three families in the Higgs sector. We analyse the scalar potential, and investigate the minima conditions, deriving the mass matrices for the scalar, pseudoscalar and charged states. Depending on the Yukawa couplings and the Higgs spectrum, the model might allow the occurrence of potentially dangerous flavour changing neutral currents at the tree-level. We compute model-independent contributions for several observables, and as an example we apply this general analysis to a specific model of quark-Higgs interactions, discussing how compatibility with current experimental data constrains the Higgs sector.