scispace - formally typeset
Search or ask a question

Showing papers on "Pseudoscalar published in 2007"


Journal ArticleDOI
TL;DR: In this paper, the authors considered the production of a Higgs boson via gluon-fusion and its decay into two photons and computed the NLO virtual QCD corrections to these processes in a general framework in which the coupling of the Higgs particle to the external particles is mediated by a colored fermion and a colored scalar.
Abstract: We consider the production of a Higgs boson via gluon-fusion and its decay into two photons. We compute the NLO virtual QCD corrections to these processes in a general framework in which the coupling of the Higgs boson to the external particles is mediated by a colored fermion and a colored scalar. We present compact analytic results for these two-loop corrections that are expressed in terms of Harmonic Polylogarithms. The expansion of these corrections in the low and high Higgs mass regimes, as well as the expression of the new Master Integrals which appear in the reduction of the two-loop amplitudes, are also provided. For the fermionic contribution, we provide an independent check of the results already present in the literature concerning the Higgs boson and the production and decay of a pseudoscalar particle.

228 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the high temperature phase in which the D7-branes extend through the black hole horizon and computed the spectral function for vector, scalar and pseudoscalar modes on the probe.
Abstract: The holographic dual of large-Nc super-Yang-Mills coupled to a small number of flavours of fundamental matter, Nf << Nc, is described by Nf probe D7-branes in the gravitational background of Nc black D3-branes. This system undergoes a first order phase transition characterised by the `melting' of the mesons. We study the high temperature phase in which the D7-branes extend through the black hole horizon. In this phase, we compute the spectral function for vector, scalar and pseudoscalar modes on the D7-brane probe. We also compute the diffusion constant for the flavour currents.

221 citations


Journal ArticleDOI
H. Hansen1, W.M. Alberico1, A. Beraudo2, A. Molinari1, M. Nardi1, Claudia Ratti 
TL;DR: In this paper, the properties of scalar and pseudoscalar mesons at finite temperature and quark chemical potential were investigated in the framework of the Nambu-Jona-Lasinio (NJL) model coupled to the Polyakov loop (PNJL model) with the aim of taking into account features of both chiral symmetry breaking and deconfinement.
Abstract: We investigate the properties of scalar and pseudoscalar mesons at finite temperature and quark chemical potential in the framework of the Nambu-Jona-Lasinio (NJL) model coupled to the Polyakov loop (PNJL model) with the aim of taking into account features of both chiral symmetry breaking and deconfinement. The mesonic correlators are obtained by solving the Schwinger-Dyson equation in the RPA approximation with the Hartree (mean field) quark propagator at finite temperature and density. In the phase of broken chiral symmetry, a narrower width for the {sigma} meson is obtained with respect to the NJL case; on the other hand, the pion still behaves as a Goldstone boson. When chiral symmetry is restored, the pion and {sigma} spectral functions tend to merge. The Mott temperature for the pion is also computed.

164 citations


Journal ArticleDOI
TL;DR: An overview of the theory and phenomenology of hadrons and QCD from a Dyson-Schwinger equation viewpoint is provided in this paper, with details relating to the U_A(1) problem and calculated masses of the lightest J=0,1 states.
Abstract: An overview of the theory and phenomenology of hadrons and QCD is provided from a Dyson-Schwinger equation viewpoint. Following a discussion of the definition and realisation of light-quark confinement, the nonperturbative nature of the running mass in QCD and inferences from the gap equation relating to the radius of convergence for expansions of observables in the current-quark mass are described. Some exact results for pseudoscalar mesons are also highlighted, with details relating to the U_A(1) problem, and calculated masses of the lightest J=0,1 states are discussed. Studies of nucleon properties are recapitulated upon and illustrated: through a comparison of the ln-weighted ratios of Pauli and Dirac form factors for the neutron and proton; and a perspective on the contribution of quark orbital angular momentum to the spin of a nucleon at rest. Comments on prospects for the future of the study of quarks in hadrons and nuclei round out the contribution.

106 citations


Journal ArticleDOI
TL;DR: In this article, a chiral invariant Lagrangian describing the tetraquark-quark interaction is considered at the leading and sub-leading order in the large-${N}_{c}$ expansion.
Abstract: A chiral invariant Lagrangian describing the tetraquark-quarkonia interaction is considered at the leading and subleading order in the large-${N}_{c}$ expansion. Spontaneous chiral symmetry breaking generates mixing of scalar tetraquark and quarkonia states and nonvanishing tetraquark condensates. In particular, the mixing strength is related to the decay strengths of tetraquark states into pseudoscalar mesons. The results show that scalar states below 1 GeV are mainly four-quark states and the scalars between 1 and 2 GeV quark-antiquark states, probably mixed with the scalar glueball in the isoscalar sector.

95 citations


Journal ArticleDOI
TL;DR: In this article, the authors present the results of a lattice QCD calculation of the average up-down and strange quark masses and of the light meson pseudoscalar decay constants with Nf=2 dynamical fermions.
Abstract: We present the results of a lattice QCD calculation of the average up-down and strange quark masses and of the light meson pseudoscalar decay constants with Nf=2 dynamical fermions. The simulation is carried out at a single value of the lattice spacing with the twisted mass fermionic action at maximal twist, which guarantees automatic O(a)-improvement of the physical quantities. Quark masses are renormalized by implementing the non-perturbative RI-MOM renormalization procedure. Our results for the light quark masses are m_ud^{msbar}(2 GeV)= 3.85 +- 0.12 +- 0.40 MeV, m_s^{msbar}(2 GeV) = 105 +- 3 +- 9 MeV and m_s/m_ud = 27.3 +- 0.3 +- 1.2. We also obtain fK = 161.7 +- 1.2 +- 3.1 MeV and the ratio fK/fpi=1.227 +- 0.009 +- 0.024. From this ratio, by using the experimental determination of Gamma(K-> mu nu (gamma))/Gamma(pi -> mu nu (gamma)) and the average value of |Vud| from nuclear beta decays, we obtain |Vus|=0.2192(5)(45), in agreement with the determination from Kl3 decays and the unitarity constraint.

94 citations


Journal ArticleDOI
TL;DR: In this article, a light-cone quark model utilizing the soft collinear effective theory was constructed, and the form factors for pseudoscalar and vector mesons were reduced to three universal form factors which can be calculated as overlaps of hadron lightcone wave functions.
Abstract: The light-cone method provides a convenient nonperturbative tool to study the heavy-to-light form factors. We construct a light-cone quark model utilizing the soft collinear effective theory. In the leading order of effective theory, the form factors for $B$-to-light pseudoscalar and vector mesons are reduced to three universal form factors which can be calculated as overlaps of hadron light-cone wave functions. The numerical results show that the leading contribution is close to the results from other approaches. The ${q}^{2}$ dependence of the heavy-to-light form factors is also presented.

83 citations


Journal ArticleDOI
Yi Liao1, Ji-Yuan Liu1
TL;DR: The precisely measured long-ranged spin-spin interaction of electrons is used to constrain unparticle couplings to the electron, and bounds for other ranges of d exceed or are complementary to those obtained previously from exotic positronium decays.
Abstract: Unparticles as suggested by Georgi are identities that are not constrained by dispersion relations but are governed by their scaling dimension d. Their coupling to particles can result in macroscopic interactions between matter that are generally an inverse nonintegral power of distance. This is totally different from known macroscopic forces. We use the precisely measured long-ranged spin-spin interaction of electrons to constrain unparticle couplings to the electron. For 1

72 citations


Journal ArticleDOI
TL;DR: J. N. Hedditch, W. G. Kamleh, B. B. Leinweber, A. M. Williams, and J. Zanotti as mentioned in this paper
Abstract: J. N. Hedditch, W. Kamleh, B. G. Lasscock, D. B. Leinweber, A. G. Williams, and J. M. Zanotti

67 citations


Journal ArticleDOI
TL;DR: In this article, sum rules for heavy-to-light transition form factors at large recoil derived from correlation functions with interpolating currents for light pseudoscalar or vector fields in softcollinear effective theory (SCET) were investigated.
Abstract: We investigate sum rules for heavy-to-light transition form factors at large recoil derived from correlation functions with interpolating currents for light pseudoscalar or vector fields in soft-collinear effective theory (SCET). We consider both, factorizable and non-factorizable contributions at leading power in the Lambda/m_b expansion and to first order in the strong coupling constant alpha_s, neglecting contributions from 3-particle distribution amplitudes in the B-meson. We pay particular attention to various sources of parametric and systematic uncertainties. We also discuss certain form factor ratios where part of the hadronic uncertainties related to the B-meson distribution amplitude and to logarithmically enhanced alpha_s corrections cancel.

53 citations


Journal ArticleDOI
TL;DR: In this paper, the mixing angle of the η and η' mesons has been investigated from a number of different processes: V→Pγ and P→Vγ (V and P are light vector and pseudoscalar mesons respectively).
Abstract: The composition of the η and η' mesons has long been a source of discussion and is of current interest with new experimental results appearing. We investigate what can be learnt from a number of different processes: V→Pγ and P→Vγ (V and P are light vector and pseudoscalar mesons respectively), P→γγ, J/ψ,ψ'→Pγ, J/ψ,ψ'→PV, and χc0,2→PP. These constrain the η−η' mixing angle to a consistent value, ≈ 42°; we find that the c components are 5% in amplitude. We also find that, while the data hint at a small gluonic component in the η', the conclusions depend sensitively on unknown form factors associated with exclusive dynamics. In addition, we predict BR(ψ'→η'γ) ≈ 1 × 10−5 and BR(χc0→ηη') ≈ 2 × 10−5−1 × 10−4. We provide a method to test the mixing using χc2→ηη, η'η' and ηη' modes and make some general observations on χc0,2 decays. We also survey the semileptonic and hadronic decays of bottom and charmed mesons and find some modes where the mixing angle can be extracted cleanly with the current experimental data, some where more data will allow this, and some where a more detailed knowledge of the different amplitudes is required.

Journal ArticleDOI
TL;DR: In this article, a phenomenological output of eight-quark interactions considering the mass spectra of pseudoscalar and scalar mesons is derived and their equivalence to the two angle approach is derived.

Journal ArticleDOI
TL;DR: In this paper, the pseudoscalar decay constant was determined from the dependence of the eigenvalues of the valence Dirac operator on an imaginary isospin chemical potential.
Abstract: Recent advances in random matrix theory enable one to determine the pseudoscalar decay constant from the dependence of the eigenvalues of the valence Dirac operator on an imaginary isospin chemical potential. We perform a pilot test of this idea, from simulations with two flavors of dynamical overlap fermions.

Proceedings ArticleDOI
21 Mar 2007
TL;DR: In this paper, the Bethe-Salpeter equation was used to calculate the ground state mesons from the chiral limit to bottomonium, with an effective interaction that was previously fitted to the pion decay constant.
Abstract: We use the Bethe‐Salpeter equation in rainbow‐ladder truncation to calculate the ground state mesons from the chiral limit to bottomonium, with an effective interaction that was previously fitted to the chiral condensate and pion decay constant. Our results are in reasonable agreement with the data, as are the vector and pseudoscalar decay constants. The meson mass differences tend to become constant in the heavy‐quark limit. We also present calculations for the pion and rho electromagnetic form factors, and for the single‐quark form factors of the ηc and J/ψ.

Journal ArticleDOI
TL;DR: In this paper, the authors show that the warped deformed conifold has two bosonic massless modes, a pseudoscalar and a scalar, that are dual to the phase and the modulus of the baryonic condensates in the cascading gauge theory.
Abstract: As shown in arXiv:hep-th/0405282, the warped deformed conifold has two bosonic massless modes, a pseudoscalar and a scalar, that are dual to the phase and the modulus of the baryonic condensates in the cascading gauge theory. We reconsider the scalar mode sector, mixing fluctuations of the NS-NS 2-form and the metric, and include non-zero 4-d momentum $k_\mu$. The resulting pair of coupled equations produce a discrete spectrum of $m_4^2=- k_\mu^2$ which is interpreted as the spectrum of $J^{PC}= 0^{+-}$ glueballs in the gauge theory. Similarly, we derive the spectrum of certain pseudoscalar glueballs with $J^{PC}= 0^{--}$, which originate from the decoupled fluctuations of the RR 2-form. We argue that each of the massive scalar or pseudoscalar modes we find belongs to a 4-d massive axial vector or vector supermultiplet. We also discuss our results in the context of a finite length throat embedded into a type IIB flux compactification.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated a model that contains an additional SU(2) singlet and triplet scalar fields than the standard model, which allows the radiative generation of Majorana neutrino masses at two-loop order with the help of doubly charged Higgs bosons that arise from the extended Higgs sector.
Abstract: We have investigated in detail a model that contains an additional SU(2) singlet and triplet scalar fields than the Standard Model (SM). This allows the radiative generation of Majorana neutrino masses at two-loop order with the help of doubly charged Higgs bosons that arise from the extended Higgs sector. We studied in detail the phenomenology of the Higgs and neutrino sectors of the model. We give the analytical form of the masses of scalar and pseudoscalar bosons and their mixings, and the structure of the active neutrino mass matrix. It is found that the model accommodates only normal neutrino mass hierarchy, and that there is a large parameter space where the doubly charged Higgs can be observed at the LHC, thereby making it testable at the LHC. Furthermore, the neutrino-less double beta ($ onu$) decays arise predominantly from exchange processes involving the doubly charged Higgs, whose existence is thus unmistakable if $ onu$ decays are observed. The production and decays of the doubly charged Higgs are analyzed, and distinct and distinguishing signals are discussed.

Journal ArticleDOI
TL;DR: In this article, a tridiagonal matrix representation for the Dirac-Coulomb Hamiltonian was constructed, which provides a simple and straightforward relativistic extension of the complex scaling method.
Abstract: We construct a tridiagonal matrix representation for the three-dimensional Dirac-Coulomb Hamiltonian that provides for a simple and straightforward relativistic extension of the complex scaling method. Besides the Coulomb interaction, additional vector, scalar, and pseudoscalar coupling to short-range potentials are also included in the same representation. Using that, we are able to obtain highly accurate values for the relativistic bound states and resonance energies. A simple program code is developed to perform the calculation for a given charge, angular momentum, and potential configuration. The resonance structure in the complex relativistic energy plane is also shown graphically. Illustrative examples are given and we verify that in the nonrelativistic limit one obtains known results. As an additional advantage of this tridiagonal representation, we use it to obtain highly accurate evaluation of the relativistic bound state energies for the Woods-Saxon potential (as a model of nuclear interaction) with the nucleus treated as a solid sphere of uniform charge distribution.

Journal ArticleDOI
TL;DR: In this paper, the form factors for semileptonic decays of heavy-light pseudoscalar mesons in partially quenched staggered chiral perturbation theory (S Χ PT), working to leading order in 1/m Q, where m Q is the heavy-quark mass.
Abstract: We calculate the form factors for the semileptonic decays of heavy-light pseudoscalar mesons in partially quenched staggered chiral perturbation theory (S Χ PT), working to leading order in 1/m Q , where m Q is the heavy-quark mass. We take the light meson in the final state to be a pseudoscalar corresponding to the exact chiral symmetry of staggered quarks. The treatment assumes the validity of the standard prescription for representing the staggered "fourth-root trick" within S Χ PT by insertions of factors of 1/4 for each sea-quark loop. Our calculation is based on an existing partially quenched continuum chiral perturbation theory calculation with degenerate sea quarks by Becirevic, Prelovsek, and Zupan, which we generalize to the staggered (and nondegenerate) case. As a byproduct, we obtain the continuum partially quenched results with nondegenerate sea quarks. We analyze the effects of nonleading chiral terms, and find a relation among the coefficients governing the analytic valence mass dependence at this order. Our results are useful in analyzing lattice computations of form factors B → π and D → K, when the light quarks are simulated with the staggered action.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the high temperature phase in which the D7-branes extend through the black hole horizon and computed the spectral function for vector, scalar and pseudoscalar modes on the probe.
Abstract: The holographic dual of large-Nc super-Yang-Mills coupled to a small number of flavours of fundamental matter, Nf << Nc, is described by Nf probe D7-branes in the gravitational background of Nc black D3-branes. This system undergoes a first order phase transition characterised by the `melting' of the mesons. We study the high temperature phase in which the D7-branes extend through the black hole horizon. In this phase, we compute the spectral function for vector, scalar and pseudoscalar modes on the D7-brane probe. We also compute the diffusion constant for the flavour currents.

Journal ArticleDOI
TL;DR: In this paper, the two-loop renormalization functions in the $R{I}^{\ensuremath{'}}$ scheme of local bilinear quark operators were shown to be polynomial in terms of both the renormalized and bare coupling constants.
Abstract: We compute the two-loop renormalization functions, in the $R{I}^{\ensuremath{'}}$ scheme, of local bilinear quark operators $\overline{\ensuremath{\psi}}\ensuremath{\Gamma}\ensuremath{\psi}$, where $\ensuremath{\Gamma}$ denotes the scalar and pseudoscalar Dirac matrices, in the lattice formulation of QCD. We consider both the flavor nonsinglet and singlet operators; the latter, in the scalar case, leads directly to the two-loop fermion mass renormalization, ${Z}_{m}$. As a prerequisite for the above, we also compute the quark field renormalization, ${Z}_{\ensuremath{\psi}}$, up to two loops. We use the clover action for fermions and the Wilson action for gluons. Our results are given as a polynomial in ${c}_{\mathrm{SW}}$, in terms of both the renormalized and bare coupling constants, in the renormalized Feynman gauge. We also confirm the one-loop renormalization functions, for generic gauge. Finally, we present our results in the $\overline{MS}$ scheme, for easier comparison with calculations in the continuum. The corresponding results, for fermions in an arbitrary representation, are included in the Appendix.

Journal ArticleDOI
TL;DR: In this article, a non-perturbative renormalization of the chromo-magnetic operator in heavy quark effective theory was carried out, and the authors obtained its two-loop anomalous dimension in a Schrodinger functional scheme by successive one-loop conversions to the lattice MS scheme.
Abstract: We carry out the non-perturbative renormalization of the chromo-magnetic operator in Heavy Quark Effective Theory. At order 1/m of the expansion, the operator is responsible for the mass splitting between the pseudoscalar and vector B mesons. We obtain its two-loop anomalous dimension in a Schrodinger functional scheme by successive one-loop conversions to the lattice MS scheme and the scheme. We then compute the scale evolution of the operator non-perturbatively in the Nf = 0 theory between μ ≈ 0.3 GeV and μ ≈ 100 GeV, where contact is made with perturbation theory. The overall renormalization factor that converts the bare lattice operator to its renormalization group invariant form is given for the Wilson gauge action and two standard discretizations of the heavy-quark action. As an application, we find that this factor brings the previous quenched predictions of the B*–B mass splitting closer to the experimental value than found with a perturbative renormalization. The same renormalization factor is applicable to the spin-dependent potentials of Eichten and Feinberg.

Journal ArticleDOI
TL;DR: In this article, the pseudoscalar mesons of QCD through a dual embedding in a strongly curved extra dimensional spacetime were studied and their decay rates into photons were also computed and found to be in good agreement with data.
Abstract: Inspired by the AdS/CFT correspondence, we study the pseudoscalar mesons of QCD through a dual embedding in a strongly curved extra dimensional spacetime. This model incorporates the consequences of symmetry and has very few free parameters, due to constraints from five-dimensions and the operator product expansion of QCD. Using as inputs fπ and the pion, kaon, and rho masses, we compute the eta and eta prime masses to be 520 and 867 MeV, respectively. Their decay rates into photons are also computed and found to be in good agreement with data.

Journal ArticleDOI
TL;DR: In this paper, a unitarized nonrelativistic meson model was proposed for the description of the heavy and light vector and pseudoscalar mesons, which yields, in its extension to the scalar meson but for the same model parameters, a complete nonet below 1 GeV.
Abstract: A unitarized nonrelativistic meson model which is successful for the description of the heavy and light vector and pseudoscalar mesons yields, in its extension to the scalar mesons but for the same model parameters, a complete nonet below 1 GeV. In the unitarization scheme, real and virtual meson-meson decay channels are coupled to the quark-antiquark confinement channels. The flavor-dependent harmonic-oscillator confining potential itself has bound states epsilon(1.3 GeV), S(1.5 GeV), delta(1.3 GeV), kappa(1.4 GeV), similar to the results of other bound-state qqbar models. However, the full coupled-channel equations show poles at epsilon(0.5 GeV), S(0.99 GeV), delta(0.97 GeV), kappa(0.73 GeV). Not only can these pole positions be calculated in our model, but also cross sections and phase shifts in the meson-scattering channels, which are in reasonable agreement with the available data for pion-pion, eta-pion and Kaon-pion in S-wave scattering.

Journal ArticleDOI
TL;DR: In this paper, a generalized linear sigma model is proposed to give a physical picture of possible mixing between qq and qqq q low lying spin zero states, and the tree-level spectrum is calculated based on the leading terms in their approach.
Abstract: We propose a systematic procedure to study a generalized linear sigma model which can give a physical picture of possible mixing between qq and qqq q low lying spin zero states. In the limit of zero quark masses, we derive the model independent results for the properties of the Nambu-Goldstone pseudoscalar particles. For getting information on the scalars it is necessary to make a specific choice of terms. We impose two plausible physical criteria-the modeling of the axial anomaly and the suppression of effective vertices representing too many fermion lines-for limiting the large number of terms which are allowed on general grounds. We calculate the tree-level spectrum based on the leading terms in our approach and find that it prominently exhibits a very low mass isosinglet scalar state. Finally we point out that the low energy result for scattering of pions continues to hold in the general version of the model.

Journal ArticleDOI
TL;DR: In this article, the problem of fermions in the presence of a pseudoscalar plus a mixing of vector and scalar potentials which have equal or opposite signs is investigated.
Abstract: The problem of fermions in the presence of a pseudoscalar plus a mixing of vector and scalar potentials which have equal or opposite signs is investigated. We explore all the possible signs of the potentials and discuss their bound-state solutions for fermions and antifermions. The cases of mixed vector and scalar Poschl–Teller-like and pseudoscalar kink-like potentials, already analyzed in previous works, are obtained as particular cases.

Journal ArticleDOI
TL;DR: In this paper, the spinor-spinor Bethe-Salpeter equation is solved in Euclidean space using hyperspherical harmonics. But the authors do not discuss the properties of the solution for the scalar, pseudoscalar and vector meson exchange kernels including the stability of bound states.
Abstract: To solve the spinor-spinor Bethe-Salpeter equation in Euclidean space we propose a novel method related to the use of hyperspherical harmonics. We suggest an appropriate extension to form a new basis of spin-angular harmonics that is suitable for a representation of the vertex functions. We present a numerical algorithm to solve the Bethe-Salpeter equation and investigate in detail the properties of the solution for the scalar, pseudoscalar and vector meson exchange kernels including the stability of bound states. We also compare our results to the non relativistic ones and to the results given by light front dynamics.

Journal ArticleDOI
TL;DR: In this paper, the amplitudes for low-energy ππ and πK scatterings within ReχPT were analyzed in sub-threshold regions with dispersive representations obtained from the solutions of the Roy and Roy-Steiner equations.
Abstract: Chiral symmetry breaking may exhibit significantly different patterns in two chiral limits: Nf=2 massless flavours (mu=md=0, ms physical) and Nf=3 massless flavours (mu=md=ms=0). Such a difference may arise due to vacuum fluctuations of ss pairs related to the violation of the Zweig rule in the scalar sector, and it could yield numerical competition between contributions counted as leading and next-to-leading order in the chiral expansions of the observables. We recall and extend resummed chiral perturbation theory (ReχPT), a framework that we introduced previously to deal with such instabilities: it requires a more careful definition of the relevant observables and their one-loop chiral expansions. We analyse the amplitudes for low-energy ππ and πK scatterings within ReχPT, which we match in subthreshold regions with dispersive representations obtained from the solutions of the Roy and Roy–Steiner equations. Using a frequentist approach, we constrain the quark mass ratio as well as the quark condensate and the pseudoscalar decay constant in the Nf=3 chiral limit. The results mildly favour significant contributions of vacuum fluctuations suppressing the Nf=3 quark condensate compared to its Nf=2 counterpart.

Journal ArticleDOI
TL;DR: In this article, the amplitudes for low-energy pi-pi and pi-K scatterings within ReChPT were analyzed in sub-threshold regions with dispersive representations obtained from the solutions Roy and Roy-Steiner equations.
Abstract: Chiral symmetry breaking may exhibit significantly different patterns in two chiral limits: N_f=2 massless flavours (m_u=m_d=0, m_s physical) and N_f=3 massless flavours (m_u=m_d=0=m_s=0). Such a difference may arise due to vacuum fluctuations of s-bar{s} pairs related to the violation of the Zweig rule in the scalar sector, and could yield a numerical competition between contributions counted as leading order and next-to-leading in the chiral expansions of observables. We recall and extend Resummed Chiral Perturbation Theory (ReChPT), a framework that we introduced previously to deal with such instabilities: it requires a more careful definition of the relevant observables and their one-loop chiral expansions. We analyse the amplitudes for low-energy pi-pi and pi-K scatterings within ReChPT, which we match in subthreshold regions with dispersive representations obtained from the solutions Roy and Roy-Steiner equations. Using a frequentist approach, we constrain the quark mass ratio as well as the quark condensate and the pseudoscalar decay constant in the N_f=3 chiral limit. The results mildly favour significant contributions of vacuum fluctuations suppressing the N_f=3 quark condensate compared to its N_f=2 counterpart.

Journal ArticleDOI
TL;DR: In this article, two variants of quenched twisted mass QCD (tmQCD) with degenerate Wilson quarks of masses equal to or heavier than half the strange quark mass were simulated.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the associated production of a very light pseudoscalar Higgs boson with a pair of charginos, which can be used to distinguish the next-to-minimal supersymmetric standard model (NMSSM) from MSSM.
Abstract: In the next-to-minimal supersymmetric standard model (NMSSM), the unique λSHuHd in the superpotential gives rise to a coupling involving the lighter pseudoscalar Higgs boson and a pair of charged or neutral Higgsinos, even in the limit of zero mixing between the two pseudoscalar Higgs bosons. We study the associated production of a very light pseudoscalar Higgs boson with a pair of charginos. The novel signature involves a pair of charged leptons from chargino decays and a pair of photons from the pseudoscalar Higgs boson decay, plus large missing energy at the LHC and ILC. The signal may help us to distinguish the NMSSM from MSSM, provided that the experiment can resolve the two photons from the decay of the pseudoscalar Higgs boson.