Final state radiation and a possibility to test a pion-photon interaction model near two-pion threshold

Final state radiation in the process $e^+e^-\to\pi^+\pi^-$ is considered for the cuts used in the analysis of KLOE data at large angles. By means of a Monte Carlo event generator FEVA, effects of non-pointlike behaviour of pions are estimated in the framework of Resonance Perturbation Theory. An additional complication related with the $\phi$ meson intermediate state is taken into account and the corresponding contributions (the direct decay $\phi\to\pi^+\pi^-\gamma$ and the double resonance decay $\phi\to\rho^\pm\pi^\mp\to\pi^+\pi^-\gamma$) are added to FEVA. A method to test effects of non-pointlike behaviour of pions in a model-independent way is proposed.Comment: 16 pages, 6 figure

Test of FSR in the process e+e−→π+π−γe^+e^-\to\pi^+\pi^-\gamma at DAΦ\PhiNE

In this paper we consider the possibility to test the FSR model in the reaction $e^+e^-\to\pi^+\pi^-\gamma$ at DA$\Phi$NE. We propose to consider the low $Q^2$ region ($Q^2$ is the invariant mass squared of the di-pion system) to study the different models describing $gamma^*\to\pi^+\pi^-\gamma$ interaction. As illustration we compare the scalar QED and Resonance Perturbation Theory prediction for the $e^+e^-\to\pi^+\pi^-\gamma$ cross section. We also consider the contribution coming from the $\phi$ direct decay ($\phi\to\pi^+\pi^-\gamma$). We find the low $Q^2$ region is sensitive to FSR models.Comment: 7 pages, 4 figures, talk at EURIDICE Midterm Collaboration Meeting, Frascati, 8-12 Februar

FASTERD: a Monte Carlo event generator for the study of final state radiation in the process e+e−→ππγe^+e^-\to\pi\pi\gamma at DAΦ\PhiNE

FASTERD is a Monte Carlo event generator to study the final state radiation both in the $e^+e^-\to\pi^+\pi^-\gamma$ and $e^+e^-\to\pi^0\pi^0\gamma$ processes in the energy region of the $\phi$-factory DA$\Phi$NE. Differential spectra that include both initial and final state radiation and the interference between them are produced. Three different mechanisms for the $\pi\pi\gamma$ final state are considered: Bremsstrahlung process (both in the framework of sQED and Resonance Perturbation Theory), the $\phi$ direct decay ($e^+e^-\to\phi\to (f_0;f_0+\sigma)\gamma\to \pi\pi\gamma$) and the double resonance mechanism (as $e^+e^-\to\phi\to \rho^\pm\pi^\mp\to \pi^+\pi^-\gamma$ and $e^+e^-\to\rho\to \omega\pi^0\to \pi^0\pi^0\gamma$). Additional models can be incorporated as well.Comment: 24 pages, 9 figure

Test of FSR in the process e+e−→π+π−γe^+e^-\to\pi^+\pi^-\gamma at DAΦ\PhiNE and extraction of the pion form factor at threshold

Effects due to non-pointlike behaviour of pions in the process $e^+e^-\to\pi^+\pi^-\gamma$ can arise for hard photons in the final state. By means of a Monte Carlo event generator, which also includes the contribution of the direct decay $\phi\to\pi^+\pi^-\gamma$, we estimate these effects in the framework of Resonance Perturbation Theory. We consider angular cuts used in the KLOE analysis of the pion form factor at threshold. A method to reveal the effects of non-pointlike behaviour of pions in a model-independent way is proposed.Comment: 13 pages, 6 figure

Final-state radiation in electron-positron annihilation into pion pair

The process of $e^+ e^-$ annihilation into $\pi^+ \pi^-$ pair with radiation of the photon is considered. The amplitude of the reaction $e^+ e^- \to \pi^+ \pi^- \gamma$ consists of the model independent initial-state radiation (ISR) and model dependent final-state radiation (FSR). The general structure of the FSR tensor is constructed from Lorentz covariance, gauge invariance and discrete symmetries in terms of the three invariant functions. To calculate these functions we apply Chiral Perturbation Theory (ChPT) with vector and axial-vector mesons. The contribution of $e^+ e^- \to \pi^+ \pi^- \gamma$ process to the muon anomalous magnetic moment is evaluated, and results are compared with the dominant contribution in framework of a hybrid model, consisting of VMD and point-like scalar electrodynamics. The developed approach allows us also to calculate the $\pi^+ \pi^-$ charge asymmetry.Comment: 4 pages, 3 figures, poster contribution at DAFNE04 conference, 7-11 June,2004, Frascati, Ital

Phenomenology of excited doubly charged heavy leptons at LHC

We consider the production at the LHC of exotic composite leptons of charge Q=+2e. Such states are allowed in composite models which contain extended isospin multiplets (Iw=1 and Iw=3/2). These doubly charged leptons couple with Standard Model [SM] fermions via gauge interactions, thereby delineating and restricting their possible decay channels. We discuss the production cross section at the LHC of L++ (p p --> L++, l-) and concentrate on the leptonic signature deriving from the cascade decays L++ --> W+, l+ --> l+, l+, \nu_l i.e. p p --> l-, l+, l+, \nu_l showing that the invariant mass distribution of the like-sign dilepton has a sharp end point corresponding to excited lepton mass m*. We find that the sqrt{s}=7 TeV run is sensitive at the 3-sigma (5-sigma) level to a mass of the order of 600 GeV if L=10 fb^-1 (L=20 fb^-1). The sqrt{s}=14 TeV run can reach a sensitivity at 3-sigma (5-sigma) level up to m*=1 TeV for L=20 fb^-1 (L=60 fb^-1).Comment: Contains a new section (section IV) that discusses pair production of the exotic doubly charged leptons. Version to appear in the Physical Review

Infrared Gluon Resummation and pp total cross-sections

We address here the problem of describing both the total and the elastic proton-proton cross-section, through the four outstanding features of hadron scattering: (i) the optical point; (ii) the forward peak, (iii) the dip and (iv) the subsequent descent at larger momentum transfers. These issues are discussed through an eikonal model for the elastic amplitude where the matter distribution in impact parameter space is given by resummed soft gluons down into the infrared (IR) region. The asymptotic growth of the total cross-section is obtained in a mini-jet model and the taming (saturation) at high energies is related to confinement realized here through an IR singular strong coupling constant alpha_s(Q^2). We present an ansatz that links the IR singularity of alpha_s(Q^2) to that of asymptotic freedom (AF) (at lowest order). Through this model, we illustrate the problems that arise in a generic one-channel eikonal model employed for a description of the measured differential elastic cross-section at LHC7.Comment: 11 pages, 9 figures, presented at Photon 2013, May 20-24, May 2013, Paris, Franc

The non-diffractive pp cross-section and Survival Probabilities at LHC

We present an estimate of survival probability from an eikonal mini- jet model implemented with a proposal for soft gluon resummation to all orders. We compare it with experimental data for diffractive di-jet production from LHC experiments, CMS and ATLAS, both at LO and NLO order.Comment: 6 pages, 2 figures, Presented at EDS Blois 2017, Prague, Czech Republic, June 26-30, 201

Soft edge of hadron scattering and mini-jet models for the total and inelastic pp cross-sections at LHC and beyond

We show that the onset and rise of QCD mini-jets provide the dynamical mechanism behind the appearance of a soft edge in pp collisions around ISR energies and thus such a soft edge is built in our mini-jet model with soft gluon resummation. Here the model is optimized for LHC at $\sqrt{s} = 7, 8 TeV$ and predictions made for higher LHC and cosmic ray energies. Further, we provide a phenomenological picture to discuss the breakup of the total cross-section into its elastic, uncorrelated and correlated inelastic pieces in the framework of a one-channel eikonal function.Comment: 16 pages, 11 figures. This version includes typos corrected, references updated, a small change in the title, already present in version v2. In the present version two computer errors in Table I and one in Table II have been corrected, a typo in Eq.(12) has been corrected, all indicated in footnotes. Figures and conclusions are unchange

Production of exotic composite quarks at the LHC

We consider the production at the LHC of exotic composite quarks of charge $Q=+(5/3) e$ and $Q=-(4/3) e$. Such states are predicted in composite models of higher isospin multiplets ($I_W=1$ or $I_W=3/2$). Given their exotic charges (such as $5/3$), their decays proceed through the electroweak interactions. We compute decay widths and rates for resonant production of the exotic quarks at the LHC. Partly motivated by the recent observation of an excess by the CMS collaboration in the $e\not p_T jj$ final state signature we focus on $pp \to U^+ j \to W^+ + j\, j\, \to \ell^+\not p_T jj$ and then perform a fast simulation of the detector reconstruction based on DELPHES. We then scan the parameter space of the model ($m_*=\Lambda$) and study the statistical significance of the signal against the relevant standard model background ($Wjj$ followed by leptonic decay of the $W$ gauge boson) providing the luminosity curves as function of $m_*$ for discovery at 3- and 5-$\sigma$ level.Comment: 14 pages, 10 figure