With the advent of the LHC there is widespread interest in the discovery potential for physics beyond the standard model. In TeV-scale open string theory, the new physics can be manifest in the excitation and decay of new resonant structures, corresponding to Regge recurrences of standard model particles. An essential input for the prediction of invariant mass spectra of the decay products (which could serve to identify the resonance as a string excitation) are the partial and total widths of the decay products. We present a parameter-free calculation of these widths for the first Regge recurrence of the SU(3) gluon octet, of the U(1) gauge boson which accompanies gluons in D-brane constructions, and of the quark triplet.
We consider string realizations of the Randall-Sundrum effective theory for electroweak symmetry breaking and explore the search for the lowest massive Regge excitation of the gluon and of the extra (color singlet) gauge boson inherent of D-brane constructions. In these curved backgrounds, the higher-spin Regge recurrences of Standard Model fields localized near the IR brane are warped down to close to the TeV range and hence can be produced at collider experiments. Assuming that the theory is weakly coupled, we make use of four gauge boson amplitudes evaluated near the first Regge pole to det…
The spectrum of the $s\bar s$ mesons is studied performing a phenomenological analysis of the Regge trajectories defined for the excitation energies. For the $ϕ(3 ^3S_1)$ state the mass $M(ϕ(3S))=2100(20)$ MeV and the leptonic width $Γ_{ee}(ϕ(3S))=0.27(2)$ keV are obtained, while the mass of the $2 ^3D_1$ state, $M(ϕ(2 ^3D_3))=2180(5)$ MeV, appears to be in agreement with the mass of the $ϕ(2170)$ resonance, and its leptonic width, $Γ_{ee}(2 ^3D_1)=0.20\pm 0.10$ keV, has a large theoretical uncertainty, depending on the parameters of the flattened confining potential.
We analyze the asymptotic behavior of Regge trajectories of non-strange mesons. In contrast to an existing belief, it is demonstrated that for the asymptotically linear Regge trajectories the width of heavy hadrons cannot linearly depend on their mass. Using the data on masses and widths of rho_J, omega_J, a_J and f_J mesons for the spin values J \leq 6, we extract the parameters of the asymptotically linear Regge trajectory predicted by the finite width model of quark gluon bags. As it is shown the obtained parameters for the data set B correspond to the cross-over temperature lying in the in…
Maximally complex Regge trajectories are introduced for which both Re $α(s)$ and Im $α(s)$ grow as $s^{1-ε}$ ($ε$ small and positive). Our expression reduces to the standard real linear form as the imaginary part (proportional to $ε$) goes to zero. A scaling formula for the total widths emerges: $Γ_{TOT}/M\to$ constant for large M, in very good agreement with data for mesons and baryons. The unitarity corrections also enhance the space-like slopes from their time-like values, thereby resolving an old problem with the $ρ$ trajectory in $πN$ charge exchange. Finally, the unitarily enhanced inter…
We calculate the mass of the lowest lying spin two glueball in N=1 super Yang-Mills from the dual Klebanov-Strassler background. We show that the Regge trajectory obtained is linear; the 0++, 1-- and 2++ states lie on a line of slope 0.23 -measured in units of the conifold deformation. We also compare mass ratios with lattice data and find agreement within one standard deviation.
It is shown that two physical phenomena are important for high excitations: (i) the screening of the universal gluon-exchange potential and (ii) the flattening of the confining potential owing to creation of quark loops, and both effects are determined quantitatively. Taking the first effect into account, we predict the masses of the ground states with $l=0,1,2$ in agreement with experiment. The flattening effect ensures the observed linear behaviour of the radial Regge trajectories $M^2(n)=m_0^2 + n_r μ^2$ GeV$^2$, where the slope $μ^2$ is very sensitive to the parameter $γ$, which determines…
A model for a Regge trajectory compatible with the threshold behavior required by unitarity and asymptotics in agreement with analyticity constraints is given in explicit form. The model is confronted in the time-like region with widths and masses of the mesonic resonances and, in the space-like region, the $ρ$ trajectory is compared with predictions derived from $π-N$ charge-exchange reaction. Breaking of the exchange degeneracy is studied in the model and its effect on both the masses and widths is determined.
Using an exactly solvable statistical model we discuss the equation of state of large/heavy and short-living quark gluon plasma (QGP) bags. We argue that the large width of the QGP bags explains not only the observed deficit in the number of hadronic resonances, but also clarifies the reason why the heavy QGP bags cannot be directly observed even as metastable states in a hadronic phase. Also the Regge trajectories of large and heavy QGP bags are established both in a vacuum and in a strongly interacting medium. It is shown that at high temperatures the average mass and width of the QGP bags b…
An empirical principle for the construction of a linear relationship between the total angular momentum and squared-mass of baryons is proposed. In order to examine linearity of the trajectories, a rigorous least-squares regression analysis was performed. Unlike the standard Regge-Chew-Frautschi approach, the constructed trajectories do not have non-linear behaviour. A similar regularity may exist for lowest-mass mesons. The linear baryonic trajectories are well described by a semi-classical picture based on a spinning relativistic string with tension. The obtained numerical solution of this m…
We discuss a possibility that linear Regge trajectories originate not from gluonic strings connecting quarks, as it is usually assumed, but from pion excitations of light hadrons. From this point of view, at large angular momenta both baryons and mesons lying on linear Regge trajectories are slowly rotating thick strings of pion field, giving rise to a universal slope computable from the pion decay constant. The finite resonance widths are mainly due to the semiclassical radiation of pion fields by the rotating elongated chiral solitons. Quantum fluctuations about the soliton determine a strin…
Two-body decay widths of lowest lying and next-to-lowest lying scalar and pseudoscalar mesons are studied in Generalized Linear Sigma Model (GLSM) of low-energy QCD. This model which considers mixing between "two quark" and "four quark" chiral nonets has been employed to investigate various decays and scatterings in low energy region of QCD. In this paper, $Γ[f_0(980) \rightarrow K \bar{K}]$ and $Γ[a_0(980) \rightarrow K \bar{K}]$ are obtained and it is shown that two-body decay widths of lowest lying mesons are well predicted by this model while for the next-to-lowest lying mesons, only some …
We demonstrate that near the threshold, the pi pi scattering amplitude contains a pole with the quantum numbers of the vacuum - commonly referred to as the sigma - and determine its mass and width within small uncertainties. Our derivation does not involve models or parametrizations, but relies on a straightforward calculation based on the Roy equation for the isoscalar S-wave.
I. Caprini's, G. Colangelo's, and H. Leutwyler's (CCL) article "Mass and Width of the Lowest Resonance in QCD", Phys. Rev. Lett. 96, 132001 (2006) [hep-ph/0512364], is critically reviewed. The present comment is devoted to complement a recent experimental discussion (D.V. Bugg, J. Phys. G 34, 151 (2007) [hep-ph/0608081]) of short-comings in the CCL analysis, by presenting theoretical arguments pointing at a serious flaw in the theoretical formalism used by CCL, and also at the unlikeliness of their tiny error bars in the sigma-meson mass and width. The criticism made in the comment applies ana…
Various string models of mesons and baryons include a string carrying 2 or 3 massive points (quarks or antiquarks). Rotational states (planar uniform rotations) of these systems generate quasilinear Regge trajectories and may be used for describing excited hadron states on these trajectories. For different string models of baryon we are to solve the problem of choice between them and the stability problem for their rotational states. An unexpected result is that for the Y string baryon model these rotations are unstable with respect to small disturbances on the classical level. This instabilit…
A QCD Laplace sum rule framework is employed to investigate the relationship between the mass and the decay width of the sigma, the lowest-lying isoscalar resonance in the spin-zero meson channel. Our analysis differs from prior analyses, not only by incorporating finite-width departures from the narrow resonance approximation, but also through the inclusion of direct-instanton contributions and three-loop-order perturbative effects. Assuming that the sigma is the dominant subcontinuum resonance in this channel, the least upper bound we obtain for the sigma-mass is shown to increase with the s…
We study higher level Regge resonances of open superstrings, focusing on the universal part of the Neveu-Schwarz sector common to all D-brane realizations of the standard model. For Regge states with masses far above the fundamental string scale, we discuss the spin-dependence of their decay rates into massless gauge bosons. Extending our previous work on lowest level string excitations, we study the second mass level at which spins range from 0 to 3. We construct the respective vertex operators and compute the amplitudes involving one massive particle and two or three gauge bosons. To illustr…
In the first part of this dissertation, we study two different aspects of string phenomenology. First we discuss the complementary signals of low mass superstrings at the proposed electron-positron facilities (ILC and CLIC), in e+e- and γ γ collisions. We examine all relevant four-particle amplitudes evaluated at the center of mass energies near the mass of lightest Regge excitations and extract the corresponding pole terms. Secondly, we consider string realizations of the Randall-Sundrum effective theory and explore the search for the lowest massive Regge excitation of the gluon and of the ex…
We study aspects of TeV string scale models of intersecting D-branes. The gauge bosons arise from strings ending on stacks of D-branes, whereas chiral matter arises from strings stretched between intersecting D-branes. Our focus is on scattering amplitudes (at tree-level), Regge states (string excitations), and collider phenomenology. Achieving a low string scale is possible in models of Large extra dimensions. At the LHC, a low enough string scale implies that cross sections will deviate from their standard model predictions. Moreover, Regge states as well as Kaluza-Klein states and winding s…
The framework of phenomenological quark-antiquark potential (Coulomb plus linear confinement) model with the Gaussian wave function is used for detailed study of masses of the ground, orbitally and radially excited states of heavy-light $Q\overline{q}$, $\left(Q=c,q=u/d,s\right)$ mesons. We incorporate $\mathcal{O}(1/m)$ correction to the potential energy term and relativistic corrections to the kinetic energy term of the hamiltonian. The spin-hyperfine, the spin-orbit and the tensor interactions incorporating the effect of mixing are employed to obtained the pseudoscalar, the vector, radially…
By exploring heavy quark effective theory (HQET), we use theoretical available data for bottom mesons to analysis the masses and decays for n = 3 charm mesons. From the predicted masses, we studied ground state strong decay modes in terms of couplings. Comparing the decays with available total decay widths, we provide upper bounds on the associated couplings. We also plot Regge trajectories for our predicted data in planes (J, $M^2$ ) and ($n_r$, $M^2$ ) and estimated higher masses (n = 4) by fixing Regge slopes and intercepts. These Regge trajectories are used to clarify $D_2^*(3000)$ state's…
Widths of the rapidity distributions of various identified hadrons generated with the UrQMD-3.4 event generator at all the Super Proton Synchrotron (SPS) energies have been presented and compared with the existing experimental results. An increase in the width of the rapidity distribution of $Λ$ could be seen with both Monte Carlo (MC) and experimental data for the studied energies. Using MC data, the study has been extended to Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. A similar jump, as observed in the plot of rapidity width versus rest mass at Alternati…
We study the eta' to eta pi pi decay within an effective chiral Lagrangian approach in which the lowest lying scalar meson candidates sigma(560) and kappa(900) together with the f0(980) and a0(980) are combined into a possible nonet. We show that there exists a unique choice of the free parameters of this model which, in addition to fitting the pi pi and pi K scattering amplitudes, well describes the experimental measurements for the partial decay width of eta' to eta pi pi and the energy dependence of this decay. As a by-product, we estimate the a0(980) width to be 70 MeV, in agreement with a…
We first derive the mass sum rules for the heavy hybrid mesons to obtain the binding energy and decay constants in the leading order of HQET. The pionic couplings between the lightest $1^{-+}$ hybrid $(Q\bar q g)$ and the lowest three heavy meson doublets are calculated with the light cone QCD sum rules. With $SU_f (3)$ flavor symmetry we calculate the widths for all the possible two-body decay processes with a Goldstone boson in the final state. The total width of the $1^{-+}$ hybrid is estimated to be 300 MeV. We find the dominant decay mode of the $1^{-+}$ hybrid is $1^{-+}\to π+ 1^+$ where…
We consider some radiative corrections to the lowest order annihilation diagram for the orthopositronium decay rate. The insertion of the renormalized vertex correction in the annihilation graph gives $1.6283 (α/π)^2 Γ_0$. We compute also the contribution of the square of the lowest order annihilation amplitude, which turns out to be $0.1702 (α/π)^2 Γ_0$. Finally, we obtain a term $α^2 \lnαΓ_0$ arising from the correction to the light-light scattering block due to the exchange of one coulombic photon, in agreement with earlier computations.
We compute the electroweak corrections due to the light fermions to the production cross section $σ(g g \to H)$ and to the partial decay widths $Γ(H \to γγ)$ and $Γ(H \to g g)$. We present analytic results for these corrections that are expressed in terms of Generalized Harmonic Polylogarithms. We find that for the gluon fusion production cross section and for the decay width $Γ(H \to g g)$ the corrections are large in the Higgs mass region below 160 GeV where they reach up to 9% of the lowest order term. For the decay width $Γ(H \to γγ)$ the corrections for Higgs mass above 160 GeV can reach …
The energy and decay width of the pi-K atom are evaluated in the framework of the quasipotential-constraint theory approach. The main electromagnetic and isospin symmetry breaking corrections to the lowest-order formulas for the energy shift from the Coulomb binding energy and for the decay width are calculated. They are estimated to be of the order of a few per cent. We display formulas to extract the strong interaction S-wave pi-K scattering lengths from future experimental data concerning the pi-K atom.
We analyze the decays of the theoretically predicted lowest bottomonium hybrid $H(1P)$ to open bottom two-meson states. We do it by embedding a quark pair creation model into the Born-Oppenheimer framework which allows for a unified, QCD-motivated description of bottomonium hybrids as well as bottomonium. A new $^{1}\!P_{1}$ decay model for $H(1P)$ comes out. The same analysis applied to bottomonium leads naturally to the well-known $^{3}\!P_{0}$ decay model. We show that $H(1P)$ and the theoretically predicted bottomonium state $Υ(5S)$, whose calculated masses are close to each other, have ve…
The widths for pionic decays of lowest two excited doublets (0^+,1^+) and (1^+,2^+) of heavy mesons are studied with QCD sum rules in the leading order of heavy quark effective theory. The ambiguity due to presence of two distinct 1^+ states are solved. The soft pion approximation is not used.
We study the width of a two-body resonance in a coupled-channel system. We demonstrate how the width does not come only determined by the available phase space for its decay to the detection channel, but it greatly depends on the relative position of the mass of the resonance with respect to the masses of the coupled-channels generating the state. Our results are consistent with the experimental observation of narrow hadrons lying well above their lowest decay threshold.
In this paper we further develop a string model of hadrons by computing their strong decay widths and comparing them to experiment. The main decay mechanism is that of a string splitting into two strings. The corresponding total decay width behaves as $Γ=\frac\pi2 ATL$ where $T$ and $L$ are the tension and length of the string and $A$ is a dimensionless universal constant. We show that this result holds for a bosonic string not only in the critical dimension. The partial width of a given decay mode is given by $Γ_i/Γ=Φ_i\exp(-2πCm_{sep}^2/T)$ where $Φ_i$ is a phase space factor, $m_{sep}$ is t…
The partial decay widths of lowest lying negative parity baryons belonging to the 70-plet of SU(6) are analyzed in the framework of the 1/Nc expansion The channels considered are those with single pseudo-scalar meson emission. The analysis is carried out to sub-leading order in 1/Nc and to first order in SU(3) symmetry breaking. Conclusions about the magnitude of SU(3) breaking effects along with predictions for some unknown or poorly determined partial decay widths of known resonances are obtained.
Inspired by the recent observations of $B$ and $B_s$ meson states at LHCb\cite{Aaij:2020hcw} we calculate the masses of ground, orbitally, and radially excited states. Also, we estimate the mixing parameters, decay constant, leptonic decay width, and corresponding branching ratios, as well as electromagnetic transition widths. ${\cal{O}}\left(\frac{1}{m}\right)$ and ${\cal{O}}(p^{10})$ relativistic corrections to potential and kinetic energy terms have been added to the Hamiltonian. The screening potential employed is solved by applying the gaussian wave function. The estimated masses are used…
The static properties and semileptonic decays of ground-state doubly heavy baryons are studied working in the framework of a non-relativistic quark model. Using a phenomenological potential model, we calculate the ground-state masses and magnetic moments of doubly heavy $ Ω$ and $ Ξ$ baryons. In the heavy quark limit, we introduce a simple form of the universal Isgur-Wise function used as the transition form factor and then investigate the exclusive $ b \rightarrow c $ semileptonic decay widths and branching ratios for $ \frac{1}{2}\rightarrow \frac{1}{2} $ baryon transitions. Our obtained res…
We describe the the improved properties of the NMHDECAY program, that is designed to compute Higgs and sparticle masses and Higgs decay widths in the NMSSM. In the version 2.0, Higgs decays into squarks and sleptons are included, accompagnied by a calculation of the squark, gluino and slepton spectrum and tests against constraints from LEP and the Tevatron. Further radiative corrections are included in the Higgs mass calculation. A link to MicrOMEGAs allows to compute the dark matter relic density, and a rough (lowest order) calculation of the BR(s -> b gamma) is performed.
In a previous work we have studied the isospin 1/2 lowest positive and negative parity states of the pentaquark $uudc\overline{c}$, in a constituent quark model with a linear confinement and an SU(4) flavor-spin hyperfine interaction and we compared the results with the $P^+_c(4312)$, $P^+_c(4440)$ and $P^+_c(4457)$ pentaquarks observed at LHCb in 2019. Here we extend the previous work by calculating ratios of decay rates of the $P_c$ pentaquarks to $J/Ψ$ and $η_c$ and similarly the ratio of decay rates to $Λ_c {\bar D}^*$ and $Λ_c \bar D$. Our predictions are based on the SU(4)$\times$SU(2) s…
Using the QCD string theory, we investigate the physical reason of the narrow width of penta-quark baryons in terms of the large gluonic-excitation energy. In the QCD string theory, the penta-quark baryon decays via a gluonic-excited state of a baryon and meson system, where a pair of Y-shaped junction and anti-junction is created. On the other hand, we find in lattice QCD that the lowest gluonic-excitation energy takes a large value of about 1 GeV. Therefore, in the QCD string theory, the decay of the penta-quark baryon near the threshold is considered as a quantum tunneling process via a hig…
We compute the next-to-next-to-leading order (NNLO) QCD corrections to the hadronic decay rates of the pseudoscalar quarkonia, at the lowest order in velocity expansion. The validity of NRQCD factorization for inclusive quarkonium decay process, for the first time, is verified to relative order $α_s^2$. As a byproduct, the renormalization group equation (RGE) of the leading NRQCD 4-fermion operator ${\cal O}_1({}^1S_0)$ is also deduced to this perturbative order. By incorporating this new piece of correction together with available relativistic corrections, we find that there exists severe ten…
Within the nonrelativistic QCD (NRQCD) factorization framework, we compute the order-$α_s^3$ perturbative corrections to the leptonic decay of the $Υ$ and $J/ψ$ with high numerical accuracy, at the lowest order in velocity expansion. We confirm the existing three-loop results in literature. Furthermore, we explicitly consider the complex-valued light-by-light (singlet) contributions. We for the first time also consider the finite charm quark mass effect for $Υ$ leptonic decay, and obtain a new piece of 3-loop contribution to the anomalous dimension related to the composite NRQCD bilinear of ve…
We study the narrow decay width of low-lying penta-quark baryons in the QCD string theoryin terms of gluonic excitations. In the QCD string theory, the penta-quark baryon decays via a gluonic-excited state of a baryon and meson system, where a pair of Y-shaped junction and anti-junction is created. Since lattice QCD shows that the lowest gluonic-excitation energy takes a large value of about 1 GeV, the decay of the penta-quark baryon near the threshold is considered as a quantum tunneling process via a highly-excited state (a gluonic-excited state) in the QCD string theory. This mechanism stro…
The widths for $ππ$ decay of the L=1 charm mesons are calculated by describing the pion coupling to light constituents quarks by the lowest order chiral interaction. The wavefunctions of the charm mesons are obtained as solutions to the covariant Blankenbecler-Sugar equation. These solutions correspond to an interaction Hamiltonian modeled as the sum of a linear scalar confining and a screened one-gluon exchange (OGE) interaction. This interaction induces a two-quark contribution to the amplitude for two-pion decay, which is found to interfere destructively with the single quark amplitude. For…
We study gluonic excitations inside a $B_{c} $ meson in the constituent gluon model, treating a bottom-charm hybrid meson $ c \bar{b} g $ as a three-body system. We obtain the mass spectra for the hybrid mesons with magnetic gluon and electric gluon and see that their lowest states appear above the $ D B $ threshold. Also, we consider the decays of the low-lying states of the hybrid meson into $ DB , \; D^{*} B, DB^{*} $, $ D^{*}B^{*} $, $ D_{s} B_{s} $, and $D_{s} B_{s}^{*} $ mesons, developing an existing model for the strong decays. We estimate their partial decay widths and find that the w…
We show that the infrared dynamics of string modes dual to $q\bar q$ states within a Dynamical AdS/QCD model of coupled dilaton-gravity background gives the Reggelike spectrum of $f0's$ scalars and higher spin mesons consistent with experimental data. The pion mass and its trajectory were also described with a scale deformation of the metric and a rescaled string mass. The available experimental decay widths of the $S\to PP$ decays provided a complementary check of the proposed classification scheme for$f_0(980)$, $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$ as radial excitations of $f_0(600)$. Fo…
