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Register a new userS-wave meson scattering up to sqrt{s} < 2 GeV from chiral Lagrangians
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The problem of scalar mesons still remains a challenging puzzle, for which we do not even know which are the right pieces to set up. The proliferation of resonances (some of them are very broad and appear on top of hadronic thresholds) and of coupled channels that interact strongly among each other makes the study of this sector a hard task. Our objective is the study of the strongly interacting mesons in coupled channels with quantum numbers J^{PC} = 0^{++} and I=0 and I=1/2, up to a center of mass energy sqrt{s} < 2 GeV. Our framework is based on Unitary Chiral Perturbation Theory. We include for I=0 the channels: pipi, Kbar{K}, etaeta, sigmasigma, etaeta, rhorho, omegaomega, etaeta, omegaphi, phiphi, K^ast bar{K}^ast, a_1(1260)pi and pi^{star}(1300)pi. In addition, and in order to constrain our fits, we also study the I=1/2, 3/2 channels given by Kpi, Keta and Keta. We finally present the resonant content of our fits with the $sigma$, $f_0(980)$, $f_0(1310)$, $f_(1500)$, $f_0(1710)$ and $f_0(1790)$.
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A recent analysis of data on the two photon production of the $eta_c$ and its decay to $K(Kpi)$ has determined the $Kpi$ $S$-wave amplitude in a model-independent way assuming primarily that the additional kaon is a spectator in this decay. The purpose of this paper is to fit these results, together with classic $Kpi$ production data from LASS, within a formalism that implements unitarity for the di-meson interaction. This fixes the $I=1/2$ $Kpito Kpi$ $S$-wave amplitude up to 2.4 GeV. This resolves the Barrelet ambiguity in the original LASS analysis, and constrains the amount of inelasticity in $Kpi$ scattering, highlighting that this becomes significant beyond 1.8 GeV. This result needs to be checked by experimental information on the many inelastic channels, in particular $Keta^prime$ and $Kpipipi$. Our analysis provides a single representation for the $Kpi$ $S$-wave from threshold, controlled by Chiral Perturbation Theory, through the broad $kappa$, $K_0^*(1430)$ and $K_0^*(1950)$ resonances. There is no arbitrary sum of Breit-Wigner forms and random backgrounds for real $Kpi$ masses. Rather the form provides a representation that can be translated to other processes with $Kpi$ interactions with their own coupling functions, while automatically maintaining consistency with the chiral dynamics near threshold, with the LASS data and the new results on $eta_c$ decay.
We consider meson-baryon interactions in S-wave with strangeness -1. This is a non-perturbative sector populated by plenty of resonances interacting in several two-body coupled channels.We study this sector combining a large set of experimental data. The recent experiments are remarkably accurate demanding a sound theoretical description to account for all the data. We employ unitary chiral perturbation theory up to and including cal{O}(p^2) to accomplish this aim. The spectroscopy of our solutions is studied within this approach, discussing the rise from the pole content of the two Lambda(1405) resonances and of the Lambda(1670), Lambda(1800), Sigma(1480), Sigma(1620) and Sigma(1750). We finally argue about our preferred solution.
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section of $phi$(1020)-meson production at forward rapidity in $p$$+$$p$ collisions at $sqrt{s}=$510 GeV via the dimuon decay channel. The partial cross section in the rapidity and $p_T$ ranges $1.2<|y|<2.2$ and $2<p_T<7$ GeV/$c$ is $sigma_phi=[2.28 pm 0.09,{rm (stat)} pm 0.14,{rm (syst)} pm 0.27, {rm (norm)}] times 10^{-2}$~mb. The energy dependence of $sigma_phi$ ($1.2<|y|<2.2, ; 2<p_T<5$ GeV/$c$) is studied using the PHENIX measurements at $sqrt{s}=$200 and 510 GeV and the Large-Hadron-Collider measurements at $sqrt{s}=$2.76 and 7 TeV. The experimental results are compared to various event generator predictions ({sc pythia6, pythia8, phojet, ampt, epos3,} and {sc epos-lhc}).
We study the semileptonic decays of $B_c$ meson to S-wave charmonium states in the framework of relativistic independent quark model based on an average flavor-independent confining potential $U(r)$ in the scalar-vector harmonic form $U(r)=frac{1}{2}(1+gamma^0)(ar^2+V_0)$, where ($a$, $V_0$) are the potential parameters.The form factors for $B_c^+to eta_c /psi e^+ u_e$ transitions are studied in the physical kinematic range. Our predicted branching ratios (BR) for transitions to ground state charmonia are found comparatively large $sim $ $10^{-2}$, compared to those for transitions to radially excited 2S and 3S states. Like all other mpdel predictions, our predicted BR are obtained in the hierarchy: BR($B_c^+to eta_c /psi (3S)$) $<$ BR($B_c^+to eta_c/ psi (2S)$) $<$ BR($B_c^+to eta_c /psi (1S)$). The longitudinal ($Gamma_L$) and transverse polarization ($Gamma_T$) for $B_c to psi(ns)$ decay modes are predicted in the small and large $q^2$ - region as well as in the whole physical region. The ratios for such transitions are obtained $frac {Gamma_L}{Gamma_T} < 1$ throughout the kinematic range which means the $B_c^+$ meson transitions to vector meson charmonium states take place predominantly in transverse polarization mode. The theoretical predictions on these transitions could be tested in the on-going and forthcoming experiments at LHCb.
The cross section for the process $e^+e^- to omegaeta$ is measured in the center-of-mass energy range 1.34--2.00 GeV. The analysis is based on data collected with the SND detector at the VEPP-2000 $e^+e^-$ collider. The measured $e^+e^- to omegaeta$ cross section is the most accurate to date. A significant discrepancy is observed between our data and previous BABAR measurement.
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