Search

"Resummed-Range Effective Field Theory" is a consistent nonrelativistic Effective Field Theory of contact interactions with large scattering length a and an effective range r 0 large in magnitude but negative. Its leading order is non-perturbative, and its observables are universal in the sense that they depend only on the dimensionless ratio ξ : = 2 r 0 / a once the overall distance scale is set by | r 0 | . In the two-body sector, the relative position of the two shallow S-wave poles in the complex plane is determined by ξ . We investigate three identical bosons at leading order for a two-body system with one bound and one virtual state ( ξ ≤ 0 ), or with two virtual states ( 0 ≤ ξ < 1 ). Such conditions might, for example, be found in systems of heavy mesons. We find that no three-body interaction is needed to renormalise (and stabilise) the leading order. A well-defined ground state exists for 0.366 ... ≥ ξ ≥ - 8.72 ... . Three-body excitations appear for even smaller ranges of ξ around the "quasi-unitarity point" ξ = 0 ( | r 0 | ≪ | a | → ∞ ) and obey discrete scaling relations. We explore in detail the ground state and the lowest three excitations. We parametrise their trajectories as function of ξ and of the binding momentum κ 2 - of the shallowest 2 B state. These stretch from the point where three- and two-body binding energies are identical to the point of zero three-body binding. As | r 0 | ≪ | a | becomes perturbative, this version turns into the "Short-Range EFT" which needs a stabilising three-body interaction and exhibits Efimov's Discrete Scale Invariance. By interpreting that EFT as a low-energy version of Resummed-Range EFT, we match spectra to determine Efimov's scale-breaking parameter Λ ∗ in a renormalisation scheme with a "hard" cutoff. Finally, we compare phase shifts for scattering a boson on the two-boson bound state with that of the equivalent Efimov system. [ABSTRACT FROM AUTHOR]

The flavor-changing neutral current (FCNC) decays of charmed hadrons with missing energy (Ɇ) can serve as potentially promising hunting grounds for hints of new physics, as the standard-model backgrounds are very suppressed. A few of such processes have been searched for in recent experiments, specifically D0→ Ɇ by Belle and D0→ π0Ɇ and Λ c + → pɆ by BESIII, resulting in upper bounds on their branching fractions. We consider them to illuminate the possible contributions of the quark transition c → uɆ with a couple of invisible spinless bosons carrying away the missing energy, assuming that they are not charge conjugates of each other and hence can have unequal masses. We find that these data are complementary in that they constrain different sets of the underlying operators and do not cover the same ranges of the bosons' masses, but there are regions not yet accessible. From the allowed parameter space, we show that other D-meson decays, such as D → ρɆ, and the charmed-baryon ones Ξc → (Σ, Λ)Ɇ can have sizable branching fractions and therefore may offer further probes of the new-physics interactions. We point out the importance of D0 → γɆ which are not yet searched for but could access parts of the parameter space beyond the reach of the other modes. In addition, we look at a scenario where the invisibles are instead fermionic, namely sterile neutrinos, and a scalar leptoquark mediates c → uɆ. We discuss the implications of the aforesaid bounds for this model. The predictions we make for the various charmed-hadron decays in the different scenarios may be testable in the near future by BESIII and Belle II. [ABSTRACT FROM AUTHOR]

The hadroproduction of a W boson in association with a charm quark at the Large Hadron Collider is at the centre of current investigations due to its potential to probe the strangeness content of the proton. In this paper we present an implementation of the W + c production process in the PowHel event generator matched to the PYTHIA8 parton shower approach, allowing to obtain predictions for differential cross-sections with NLO QCD accuracy matched to the accuracy of the Shower Monte Carlo event generator. Effects of non-diagonal CKM matrix elements, finite charm quark mass and off-shell W decays including spin correlations are taken into account. We investigate the production of a leptonically decaying W boson in association with either a charmed meson (W± + D∗∓) or a charmed jet (W± + jc) and compare our predictions with particle-level measurements by the ATLAS and CMS collaborations at s = 7 and 13 TeV. The role of the so-called "opposite sign" and "same sign" contributions to the theoretical cross-sections is presented and discussed, pointing out the importance of including parton shower effects for a reliable estimate of the latter and a faithful comparison with experimental data. [ABSTRACT FROM AUTHOR]

An anomaly observed in the 8Be nuclear transition by the Atomki collaboration hints at a light, neutral boson decaying into an e + e − pair with a mass of about 17 MeV. In this paper, we study the Atomki anomaly in the framework of axial (ABJ) anomaly. Some theoretical results indicate that the X17 particle is the color singlet pseudoscalar. We take the X17 particle as a pseudoscalar meson (u ū) system which has the axial (ABJ) anomaly, where u denotes the up quark. Besides this, we also give an interpretation for E38 particle with a mass of about 38 MeV as a pseudoscalar meson (d d ̄) system. We obtain the correct masses of the two pseudoscalars by a non-perturbative mass formula. [ABSTRACT FROM AUTHOR]

Experimental measurements collected by the BABAR, Belle, and LHCb experiments on different observables associated with the semileptonic transition , indicate the existence of disagreement respect with the Standard Model predictions. We analyze the charged scalar boson contributions to these charged-current B meson anomalies within the framework of two Higgs doublet model (2HDM) with the most general Yukawa couplings to quarks and leptons from the third generation, involving left-handed and right-handed (sterile) neutrinos. We perform a phenomenological study of the Yukawa couplings parameter space that accommodates these anomalies. We consider the most recent data from HFLAV world-average and Belle combination, and the upper limits and 10%. In addition, we include in our study the prospect measurements on R(D(*)) that the Belle II experiment could achieve and explore, for the first time, the future implications for the corresponding charged scalar Yukawa couplings. This analysis updates the existing literature and includes new important observables. Our results show that current experimental data and Belle II projection favor the interpretation of a charged scalar boson interacting with right-handed neutrinos. Furthermore, as a side analysis regarding the charged scalar boson interpretation, we revisit the relation between R(D*) and by investigating whether the claim that pseudoscalar new physics interpretations of R(D*) are implausible due to the Bc lifetime is still valid, to the light of the recent data and Belle II prospects on R(D*). Lastly, we reexamine addressing the R(D(*)) anomalies in the context of the 2HDM of type II. We show that with the current Belle combined data is possible to obtain an available parameter space on the plane for a simultaneous explanation of the anomalies, in consistency with and bounds from inclusive radiative B decays. Moreover, projections at the Belle II experiment suggest that the 2HDM of type II would be no longer disfavored. [ABSTRACT FROM AUTHOR]

The rare leptonic decays Bs, d → l+l− (l = e, μ, τ) present an important base to analyse the flavour structure of the standard model (SM) and also become a potential source to dig out possible signatures of new physics (NP) beyond the SM. The muonic decay Bs, d → μ+μ− has been observed at the LHC as well as the upper limits of branching ratios for other Bs, d → l+l− decays have been updated recently. In this paper, using the χ2 fitting method we have studied all these decay channels considering the effect of a Z′ boson. Our analysing method reproduces the result of the muonic channel of Bs meson, hence we have used the same strategy for the other Bs, d → l+l− decays. [ABSTRACT FROM AUTHOR]

Recently, some small hints of lepton flavor violating (LFV) decays have been probed in different colliders and accelerators. Although these processes are forbidden in the Standard Model (SM), observation of LFV decays are considered as good probes to test theory beyond the SM. In this paper, we study some LFV decays, e.g. three-body decay channels of μ lepton like μ → 3 e , μ → e ν ν ̄ and two-body decays of B meson and τ lepton like B s , d → μ ± e ∓ and τ → e ϕ in Z ′ model. We calculate the branching ratio of the above decays considering the effect of both Z and Z ′ -mediated flavor-changing neutral-current (FCNC). [ABSTRACT FROM AUTHOR]

Like the two-photon and two-gluon decays of the P -wave χ c 0 , 2 and χ b 0 , 2 charmonium state for which the Born term produces a very simple decays amplitude in terms of an effective Lagrangian with two-quark local operator, the Born term for the processes c d ̄ → (π , K) ℓ ν and b d ̄ → (π , K) ℓ ν , could also produce the D and B meson semileptonic decays with the light meson π , K in the final state. In this approach to heavy-light meson form factors with the π , K meson treated as Goldstone boson, a simple expression is found for the decays form factors, given as: f + (0) / 1 − q 2 / m H 2 + m π 2 , with H = D , B for D , B → π form factors, and f + (0) / 1 − q 2 / m H 2 + m K 2 for B , D → K form factor. The purpose of this paper is to show that this expression for the form factors could describe rather well the q 2 -behavior observed in the BaBar, Belle and BESIII measurements and lattice simulation. In particular, the D → K form factors are in good agreement with the measured values in the whole range of q 2 showing evidence for S U (3) breaking with the presence of m K 2 term in the quark propagator, but some corrections to the Born term are needed at large q 2 for D , B → π form factors. [ABSTRACT FROM AUTHOR]

We proposed a global spin-dependent potential energy function which fits the description of the non-relativistic quark model. The spin dependencies of our model result from the harmonic approximation of the Gaussian function in the spin-spin component. The approximation enables us to obtain analytical solutions of the bound states for the heavy mesons singlet and triplet states using the conventional Nikiforov-Uvarov method. The obtained mass spectra and expectation values for the low through high-lying quantum states are in agreement with the results obtained for other potential functions in the existing literature. The splitting of the masses occurs at a distance greater than the obtained characteristic radius of the heavy mesons which were found to be within the experimentally observed 1 fm. The proposed potential model may be extended to obtain other meson spectroscopic parameters such as the decay constants, wave function at the origin and electromagnetic radiative transitions. [ABSTRACT FROM AUTHOR]

We present a construction of an improved two-mode model for modeling the dynamics of interacting ultra-cold bosons confined in a one-dimensional double well trap. Unlike in the typically used two-mode model based on the lowest single-particle eigenstates of the external potential, the improved model uses a basis of properly chosen effective wave functions originating in the many-body model. Accuracy of the improved model is examined and it is shown that within a certain limit of inter-particle interaction strength, the model recovers an exact evolution of the wells' populations much more closely than the traditional two-mode model. [ABSTRACT FROM AUTHOR]

We describe a method of the low-energy bosonization of quantum chromodynamics based on the chiral and scale anomalies. We give the values of structure coupling constants for the effective chiral Lagrangian of dimension four obtained by the method of low-energy bosonization and by various alternative approaches. Based on the method of quark bosonization in the meson sector of quantum chromodynamics and a set of other basic principles of quantum chromodynamics, we justify a possibility that spatial parity is broken in a hadron medium in heavy-ion collisions. [ABSTRACT FROM AUTHOR]

In the framework of the one-boson exchange model, we have calculated the effective potentials between two heavy mesons B ⁎ B ¯ ⁎ and D ⁎ D ¯ ⁎ from the t- and u-channel π -, η -, ρ -, ω - and σ -meson exchanges. We keep the recoil corrections to the B ⁎ B ¯ ⁎ and D ⁎ D ¯ ⁎ systems up to O ( 1 M 2 ) , which turns out to be important for the very loosely bound molecular states. Our numerical results show that the momentum-related corrections are favorable to the formation of the molecular states in the I G = 1 + , J PC = 1 + − in the B ⁎ B ¯ ⁎ and D ⁎ D ¯ ⁎ systems. [ABSTRACT FROM AUTHOR]

In the hot and dense hadronic sources formed in high-energy heavy-ion collisions, the particle interactions in medium might lead to a squeezed back-to-back correlation (BBC) of boson-antiboson pairs. We calculate the BBC functions of ϕϕ for sources evolving hydrodynamically in (2+1) dimensions and with longitudinal boost invariance. The BBC functions for hydrodynamic sources exhibit oscillations as a function of the particle momentum because the temporal distributions of hydrodynamic sources have sharp falls to 0 at large evolving times. The dependences of the BBC functions on the directions of the particle momentum are investigated. For transverse anisotropic sources, the BBC functions are minimum when the azimuthal angles of the particles reach 0. The BBC functions increase with decreasing absolute value of the particle pseudorapidity. The oscillations and the dependences on the particle azimuthal angle and pseudorapidity are the significant signatures for detecting the BBC in high-energy heavy-ion collisions. [ABSTRACT FROM AUTHOR]

The phenomenological implications to the decay of the neutral pion from the introduction of new dark particles are discussed. We calculate the contribution to the π 0 decay width and then we extend the theory by adding dark sector vector particles which interact through γ μ , σ μ ν and σ μ ν γ 5. We calculate the total decay width of π 0 → γ e + e − where the electron-positron pair is produced through a decay of a dark meson. The implication of the presented model on the present and future searches for new dark particles is also discussed. [ABSTRACT FROM AUTHOR]

We show that both flavor-conserving and flavor-violating Yukawa couplings of the Higgs boson to-first- and second-generation quarks can be probed by measuring rare decays of the form h → MV, where M denotes a vector meson and V indicates either y, W or Z. We calculate the branching ratios for these processes in both the standard model and its possible extensions. We discuss the experimental prospects for their observation. The possibility of accessing these Higgs couplings appears to be unique to the high-luminosity LHC and future hadron colliders, providing further motivation for those machines. [ABSTRACT FROM AUTHOR]

Data on the form factors for K decay make it possible to fix the value of a parameter that is not determined by the theory itself and which is contained in the Lagrangian for the system formed by 0 and 0 mesons. This makes it possible to find the mass of the lightest σ meson: mσ = 663 MeV. As for the nature of spin-1 mesons, which also contribute to the form factors for K decay, data on them give no way to interpret spin-1 mesons as gauge bosons of chiral theory [ABSTRACT FROM AUTHOR]

Within the QCD factorization framework, we investigate the branching fractions and the direct CP asymmetries of decays B → K*0 (1430)ρ(ω) and B → K*0 (1430)ϕ under two different scenarios in the standard model and the family nonuniversal Z' model. We find that the annihilation terms play crucial roles in these decays and lead to the major uncertainties. For decays B- → K*-0 (1430)ρ0 (ω), the new Z' boson could change the branching fractions remarkably. However, for other decays, its contribution might be clouded by large uncertainties from annihilations. Unfortunately, neither the standard model nor the Z' model can reproduce all experimental data simultaneously under one certain scenario. We also noted that the direct CP asymmetries of B- → K*-0 (1430)ρ0(ω) could be used to identify the K*0 (1430) meson and search for the contribution of new Z' boson. [ABSTRACT FROM AUTHOR]

We study the photoproduction of $ \rho$ -mesons in a model of hidden local symmetry. For this purpose, the $ \rho$ -meson is introduced as a hidden-gauge boson in a non-linear sigma model. For charged $ \rho$ -meson photoproduction, the model takes into account the $ \rho$ -meson magnetic moments from the three-point vertex in the kinetic terms. We show that the magnetic interaction of the charged $ \rho$ -meson has a significant effect on the total cross-sections through the $ \rho$ -meson exchange process, which is proportional to the energy of the photon. The t -channel dominance may be used for the study of structures of various unstable particles. [ABSTRACT FROM AUTHOR]

Abstract: The existence of a light dark force mediator has been tested with the KLOE detector at DAΦNE. This particle, called U, is searched for using the decay chain , , . No evidence is found in 1.5 fb−1 of data. The resulting exclusion plot covers the mass range , setting an upper limit on the ratio between the U boson coupling constant and the fine structure constant, , of at 90% C.L. for . [Copyright &y& Elsevier]

The heavy-ion program at the Large Hadron Collider has been commenced in November 2010 by three experiments including ATLAS, a multipurpose detector. It was originally constructed to study high-energy proton-proton collisions but now it also proves to be an excellent tool for studying nuclear interactions. In these proceedings results from the lead- lead run at √sNN = 2:76 TeV based on the minimum-bias data sample are reviewed. In particular, an observation of the centrality-dependent dijet asymmetry is reported. Also a centrality-dependent suppression in the yield of J/ψ mesons decaying to μ+μ- pairs is discussed along with an observation of the Z boson production. These evidences may bring new insight to the dynamics of heavy-ion collisions. [ABSTRACT FROM AUTHOR]

Abstract: The production in collisions is studied in the framework of a constituent quark model which incorporates Goldstone boson exchanges between quarks and has successfully described the interactions. We focus on depolarization and spin transfer observables measured by the PS185 Collaboration. Theoretical predictions for both observables differ greatly according whether quark–gluon or meson exchange models are employed. The model shares properties of both types and is able to describe the data. The inclusion of the scalar strange κ exchange at the quark level improves the description of the experimental data. [ABSTRACT FROM AUTHOR]

Abstract: The is a flavor partner of the meson which contains the strange quark. Because of the quasi-bound state which lies below the threshold, the interaction of the and the nucleon is considered to be strongly attractive, leading to the possibility of the bound nuclei. On the other hand, the is the Nambu–Goldstone boson of spontaneous breaking of chiral SU(3)×SU(3) symmetry in QCD. We discuss the dynamics of the interaction and the systems from the viewpoint of chiral symmetry. [ABSTRACT FROM AUTHOR]

We calculate the S -wave scattering lengths for charmed mesons scattering off Goldstone bosons and explore their quark mass dependence using the chiral perturbation theory up to next-to-leading order as well as a unitarized version of it. The quark mass dependence of all scattering lengths determined in a recent lattice calculation can be reproduced by the unitarized version. We also discuss signals of possible bound states in these observables. [ABSTRACT FROM AUTHOR]

Meson-baryon potentials are proposed as an extension of baryon-baryon one-boson-exchange potentials. All coupling constants satisfy the SU(3) symmetry and all mesons and baryons are assumed to have physical masses and widths and to behave as gaussian sources of meson fields. Assuming the parameters determined so as to reproduce the πN and K N scattering, our model inevitably predicts a strongly attractive S-wave $\bar K N$ interaction both in isospin 0 and 1 states. [ABSTRACT FROM AUTHOR]

By describing within the chiral unitary approach the s -wave interaction of the vector meson nonet with the octet of pseudoscalar Goldstone bosons, we find that the main component of the axial-vector mesons -- b1(1235) , h1(1170) , h1(1380) , a1(1260) , f1(1285) and the two states associated to the K1(1270) -- does not follow the QCD dependence on the number of colors for ordinary q $ \bar{{q}}$ mesons. [ABSTRACT FROM AUTHOR]

The chiral effective Lagrangian for pseudoscalar meson nonet including eight Goldstone bosons and a SU(3) singlet η0 is constructed with the breaking effect of chiral symmetry in both quark condensate and quark mass differences taken into account. The $\tilde{\pi}^0-\eta-\eta^\prime$ mixing is discussed. By solving the mass equations of pseudoscalar mesons, the quark mass ratios are obtained and the quark condensate ratios are constrained in ranges. The mass split of π0-π± is discussed. [ABSTRACT FROM AUTHOR]

We discuss a left-right symmetric model with two Higgs bi-doublet and spontaneous P and CP violation. The flavor changing neutral currents is suppressed by assuming approximate global U(1) family symmetry. We calculate the constraints from neural K meson mass difference ΔmK and demonstrate that a right-handed gauge boson W2 contribution in box-diagrams with mass around 600 GeV is allowed due to a negative interference with a light charged Higgs boson around 150 ~ 300 GeV. The W2 contribution to ɛK is suppressed from appropriate choice of additional CP phases appearing in the right-handed Cabbibo-Kobayashi-Maskawa(CKM) matrix. The model is found fully consistent with B0 mass difference and the mixing-induced CP asymmetry measurements. [ABSTRACT FROM AUTHOR]

We present a new model for the hyperon-nucleon (Λ N , Σ N interaction, derived within the meson exchange framework. The model incorporates the standard one-boson exchanges of the lowest pseudoscalar and vector meson multiplets with coupling constants fixed by SU(6) flavor symmetry relations. As a new feature, the contribution in the scalar-isoscalar (σ sector is derived from a microscopic model of correlated ππ and K¯ exchange. The same model is also used to constrain the interaction resulting from the vector-isovector (ρ exchange channel. Additional short-ranged ingredients of the model in the scalar-isovector (a0) and scalar-isospin-1/2 (κ channels are likewise viewed as arising from meson-meson correlations but are treated phenomenologically. With this model a satisfactory reproduction of the available hyperon-nucleon data is achieved. [ABSTRACT FROM AUTHOR]

Being reformulated in the color dipole basis of small- x QCD, Adler’s theorem establishes a connection between perturbative and nonperturbative descriptions of deep inelastic scattering and quantifies the effect of nonperturbative dynamics on would-be perturbative observables. In particular, it provides a quantitative measure of the nonperturbative influence on the longitudinal structure function in charged current deep inelastic scattering and imposes stringent constraints on nonperturbative parameters of color dipole models. Our analysis calls for new experimental tests of Adler’s theorem in diffractive neutrino scattering. [ABSTRACT FROM AUTHOR]

Abstract: In thermal field theory selfconsistent (Φ-derivable) approximations are used to improve (resum) propagators at the level of two-particle irreducible diagrams. At the same time vertices are treated at the perturbative level. Therefore such approximations typically violate the Ward identities connected to internal symmetries. Examples are presented how such violations can be tamed by a proper choice of representation for the fields which describe the system under consideration. These examples cover the issue of massless Goldstone bosons in the linear sigma model and the Nambu–Jona-Lasinio model and the problem of current conservation in theories with massive vector mesons. [Copyright &y& Elsevier]

In the framework of the Nambu-Jona-Lasinio model with two quark flavors, we investigate the spectrum of meson and diquark excitations of dense quark matter in the phase with color superconductivity. The color SUc(3) symmetry is spontaneously broken to SUc(2) in this phase. But instead of the expected five Goldstone bosons in the mass spectrum, we observe only three, among which two bosons obey the quadratic dispersion law. We find the doublet of light diquark states with the mass ∼ 15 MeV and also the heavy diquark resonance (SUc(2) singlet) with the mass ∼ 1100 MeV. The π-and σ-mesons have the mass ∼ 330 Mev in the phase with color superconductivity. The π-mesons are then stable particles, while the σ-meson is stable only in the chiral limit in which the current quark mass m0 becomes zero. If m0 ≠ 0, then the σ-meson mixes with diquarks in the phase with color superconductivity and becomes a resonance with the width ∼ 30 MeV. [ABSTRACT FROM AUTHOR]

In the context of the Quantum Cromodynamics, a low energy phenomena as it is the quark confinement cannot be described by the perturbation theory. In this paper, we consider the quark confinement for mesons through the exact spherical symmetric solutions of the movement equations of the SU(3) Yang-Mills theory. The obtained potential has a behavior which is lineal with the distance sigma and it also has a term of the form α/r. This behavior is consistent with the bosonic string model [ABSTRACT FROM AUTHOR]

The functional integration over the auxiliary bosonic variables of cubic order related with the effective action of the Nambu–Jona–Lasinio model with ’t Hooft term has recently been obtained in the form of a loop expansion. Even numbers of loops contribute to the action, while odd numbers of loops are assigned to the measure. We consider the two-loop corrections and analyse their effect on the low-lying pseudoscalar and scalar mass spectra, quark condensates and weak decay constants. The results are compared to the leading order calculations and other approaches. [ABSTRACT FROM AUTHOR]

A current algebra based effective chiral theory of pseudoscalar, vector, axial-vector mesons is reviewed. A new mechanism generating the masses and guage fixing terms of gauge boson is revealed from this effective theory. A EW theory without Higgs is proposed. The masses and gauge fixing terms of W and Z are dynamically generated. Three heavy scalar fields are dynamically generated too. They are ghosts. [ABSTRACT FROM AUTHOR]