Initial State Radiation Corrections Research Articles

Symmetry analysis of charmonium two-body decay

In the light of SU(3) flavor symmetry, the effective interaction Hamiltonian in tensor form is obtained by virtue of group representation theory. The strong and electromagnetic breaking effects are treated as a spurion octet so that the flavor singlet principle can be utilized as the criterion to determine the form of effective Hamiltonian. Two body decays of both baryonic and mesonic final states are parameterized in the uniform scheme, based on which the relative phase between the strong and electromagnetic amplitudes is studied for various charmonium decay modes, including psi' and/or J/jpsi decay to octet baryon pair, decuplet baryon pair, decuplet-octet baryon final state, and pseudoscalar-pseudoscalar meson final state. In data analysis of samples taken in $e^+e^-$ collider, the details of experimental effects, such as energy spread and initial state radiative correction are taken into consideration in order to make full use of experimental information and acquire the accurate and delicate results.

Symmetry analysis of charmonium decays to two-baryon final state

By virtue of SU(3) flavor symmetry, the effective interaction Hamiltonian is derived in tensor form. The strong and electromagnetic breaking effects are taken into account in a form of “spurion” octet, so that the systematical parametrization of all baryon pair final states is realized on basis of the flavor-singlet principle. As an application, the relative phase between the strong and electromagnetic amplitudes is studied in the light of this scenario. In analyzing the data taken at J/ψ resonance region in e+e− collider, the details of experimental effects, such as energy spread and initial state radiative correction are taken into consideration in order to obtain the correct results.

An iterative weighting method to apply ISR correction to e+e− hadronic cross-section measurements

Initial State Radiation (ISR) plays an important role in e+e− collision experiments such as the BESIII. To correct the ISR effects in measurements of hadronic cross-sections of e+e− annihilation, an iterative method that weights simulated ISR events is proposed here to assess the efficiency of event selection and the ISR correction factor for the observed cross-section. The simulated ISR events were generated only once, and the obtained cross-sectional line shape was used iteratively to weigh the same simulated ISR events to evaluate the efficiency and corrections until the results converge. Compared with the method of generating ISR events iteratively, the proposed weighting method provides consistent results, and reduces the computational time and disk space required by a factor of five or more, thus speeding-up e+e− hadronic cross-section measurements.

Full \(\mathcal{O}(\alpha)\) Electroweak Radiative Corrections to \(e^-e^+ \rightarrow W^-W^+\) with Initial Beam Polarization Effects

We calculate full \(\mathcal{O}(\alpha)\) electroweak radiative corrections and \(\mathcal{O}(\alpha^3)\) initial state radiation (ISR) corrections to \(e^-e^+ \rightarrow W^-W^+\) with initial beam polarization effects. In phenomenological results, we study the impact of electroweak and ISR corrections on cross-sections as well as their relevant distributions. We find that the corrections are order of 10% contributions. They are sizable contributions and should be taken into account at future lepton colliders.

The O(α2) initial state QED corrections to [formula omitted

We calculate the complete O(α2) initial state radiation corrections to e+e− annihilation into a neutral vector boson in a direct analytic computation without any approximation. The corrections are represented in terms of iterated incomplete (elliptic) integrals over alphabets of square-root valued letters. Performing the limit s≫me2, we find discrepancies with the earlier results of Ref. [1] and confirm results obtained in Ref. [2] where the effective method of massive operator matrix elements has been used, which works for all but the power corrections in me2/s. In this way, we also confirm the validity of the factorization of massive partons in the Drell-Yan process to O(α2). We add non–logarithmic terms at O(α2) which have not been considered in previous calculations. The final results in the limit s≫me2 can be given in terms of Nielsen integrals.

Subleading logarithmic QED initial state corrections to [formula omitted] to O(α6L5)

Using the method of massive operator matrix elements, we calculate the subleading QED initial state radiative corrections to the process e+e−→γ⁎/Z⁎ for the first three logarithmic contributions from O(α3L3),O(α3L2),O(α3L) to O(α5L5),O(α5L4),O(α5L3) and compare their effects to the leading contribution O(α6L6) and one more subleading term O(α6L5). The calculation is performed in the limit of large center of mass energies squared s≫me2. These terms supplement the known corrections to O(α2), which were completed recently. Given the high precision at future colliders operating at very large luminosity, these corrections are important for concise theoretical predictions. The present calculation needs the calculation of one more two–loop massive operator matrix element in QED. The radiators are obtained as solutions of the associated Callen–Symanzik equations in the massive case. The radiators can be expressed in terms of harmonic polylogarithms to weight w = 6 of argument z and (1−z) and in Mellin N space by generalized harmonic sums. Numerical results are presented on the position of the Z peak and corrections to the Z width, ΓZ. The corrections calculated result into a final theoretical accuracy for δMZ and δΓZ which is estimated to be of O(30keV) at an anticipated systematic accuracy at the FCC_ee of ∼100keV. This precision cannot be reached, however, by including only the corrections up to O(α3).

Update of inclusive cross sections of single and pairs of identified light charged hadrons

We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a $558\,{\rm fb}^{-1}$ data sample collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider.

Initial state radiation correction and its effect on data-taking scheme for σB(e+e−→ ZH) measurement

The measurement of Born cross-section of [Formula: see text] process is one of the major goals of the future Circular Electron Positron Collider, which may reach a precision of 0.5% at 240 GeV. Such unprecedented precision must be guaranteed by both theoretical and experimental sides, such as the calculations of high order corrections, the knowledge of the [Formula: see text] line shape. Uncertainty of the radiative correction factor at 240 GeV caused by the [Formula: see text] line shape is evaluated in this work. Therefore, dedicated data-taking schemes are proposed in order to precisely calculate the ISR correction factor.

Status of R value measurement at BESIII

The dominant systematic error of R value measurement comes from the hadronic generator simulations. This paper reviews the present status of R value measurement from 2.232 to 3.671 GeV at 14 energy points, especially describes the calculations of initial state radiative correction and the issue of the parameter tuning for the Lund area law generator LUARLW.

A discussion on vacuum polarization correction to the cross-section of e+e−→γ*/ψ→μ+μ−**Supported by National Natural Science Foundation of China (11275211) and (11335008)

Vacuum polarization is a part of the initial-state radiative correction for the cross-section of e+e− annihilation processes. In the energy region in the vicinity of narrow resonances J/ψ and ψ(3686), the vacuum polarization contribution from the resonant component has a significant effect on the line-shape of the lepton pair production cross-section. This paper discusses some basic concepts and describes an analytical calculation of the cross-section of e+e− →γ*/ψ→μ+μ− considering the single and double vacuum polarization effect of the virtual photon propagator. Moreover, it presents some numerical comparisons with the traditional treatments.

ISR corrections to associated HZ production at future Higgs factories

We evaluate the QED corrections due to initial state radiation (ISR) to associated Higgs boson production in electron–positron (e+e−) annihilation at typical energies of interest for the measurement of the Higgs properties at future e+e− colliders, such as CEPC and FCC–ee. We apply the QED Structure Function approach to the four-fermion production process e+e−→μ+μ−bb¯, including both signal and background contributions. We emphasize the relevance of the ISR corrections particularly near threshold and show that finite third order collinear contributions are mandatory to meet the expected experimental accuracy. We analyze in turn the rôle played by a full four-fermion calculation and beam energy spread in precision calculations for Higgs physics at future e+e− colliders.

An exclusive event generator for e+e− scan experiments

An exclusive event generator is designed for e+e− scan experiments, including initial state radiation effects up to the second order correction. The generator is coded within the framework of BesEvtGen. There are seventy hadronic decay modes available, with effective center-of-mass energy coverage from the two pion mass threshold up to about 6 GeV. The accuracy achieved for the initial state radiation correction reaches the level achieved by the KKMC generator. The uncertainty associated with the calculation of the correction factor to the initial state radiation is dominated by the measurements of the energy-dependent Born cross section.

Initial state radiation effects in inclusive J/ψ production at B factories

Based on Monte Carlo techniques, we analyze the initial state radiation (ISR) effects in prompt $\jpsi$ inclusive production at B factories. ISR enhances cross section $\sigma(e^-e^+\to\jpsi+gg+X)$ by about $15-25\%$, which is almost the same size as the QCD and relativistic correction. Moreover, ISR slightly changes $\sigma(e^-e^+\to\jpsi+c\bar{c}+X)$. The $\jpsi$ momentum spectrum in $e^-e^+\to\jpsi+gg+X$ and in $e^-e^+\to\jpsi+c\bar{c}+X$ is softer after the photon showering from the initial $e^{\pm}$ beam radiation. After combining the QCD,relativistic, and ISR corrections,a more precise theoretical result is obtained. The new result provides a more stringent constraint of the color-octet contribution to $\sigma(e^-e^+\to\jpsi+X_{\rm{non-}c\bar{c}})$.

Fast computation of observed cross section for ψ′→PP decays

It has been conjectured that the relative phase between strong and electromagnetic amplitudes is universally −90° in charmonium decays. ψ′ decaying into a pseudoscalar pair provides a possibility to test this conjecture. However, the experimentally observed cross section for such a process is depicted by the two-fold integral, which takes into account the initial state radiative (ISR) correction and energy spread effect. Using the generalized linear regression approach, a complex energy-dependent factor is approximated by a linear function of energy. Taking advantage of this simplification, the integration of ISR correction can be performed and an analytical expression with accuracy at the level of 1% is obtained. Then, the original two-fold integral is simplified into a one-fold integral, which reduces the total computing time by two orders of magnitude. Such a simplified expression for the observed cross section usually plays an indispensable role in the optimization of scan data taking, the determination of systematic uncertainty, and the analysis of data correlation.

Determination of the [formula omitted], [formula omitted], [formula omitted] and [formula omitted] resonance parameters

R values measured with the BESII detector at center-of-mass energies between 3.7 and 5.0 GeV are fitted to determine resonance parameters (mass, total width, electron width) of the high mass charmonium states, ψ(3770), ψ(4040), ψ(4160) and ψ(4415). Various effects, including the interferences and relative phases between the resonances, the energy-dependence of the full widths, and the initial state radiative correction, are examined. The results are compared to previous studies.

Monte Carlo generator for full simulation ofe+e−→hadronscross section scan experiment

A generator with {alpha}{sup 2} order radiative correction effects, including both the initial state radiative corrections and the photon vacuum polarization corrections, is built for the full simulation of e{sup +}e{sup -}{yields}hadrons in a cross section scan experiment in the quarkonium energy region. The contributions from the hadron production structures including the resonances of 1{sup --} quarkonium families and the light hadrons spectrum below 2 GeV as well as the QED continuum hadron spectrum are all taken into account in the event generation. It was employed successfully to determine the detection efficiency for selection of the events of e{sup +}e{sup -}{yields}hadrons from the data taken in the energy region from 3.650 GeV to 3.872 GeV covering both the {psi}(3686) and {psi}(3770) resonances in BES experiment. The generator reproduces the properties of hadronic event production and inclusive decays well.

Measuring ψ″→ρπ in e+e− experiment

In S- and D-wave mixing scheme, the branching ratio of ψ″→ρπ is estimated. Together with the continuum cross section of ρπ estimated by form factor, the observed cross section of ρπ production at ψ″ in e+e− experiment is calculated taking into account the interference effect between the resonance and continuum amplitudes and the initial state radiative correction. The behavior of the cross section reveals that the disappearance of ρπ signal just indicates the existence of the corresponding branching ratio Bψ″→ρπ at the order of 10−4.

SUSYGEN 2.2 — A Monte Carlo event generator for MSSM sparticle production at e +e − colliders

SUSYGEN is a Monte Carlo program designed for computing distributions and generating events for MSSM sparticle production in e +e − collisions. The Supersymmetric (SUSY) mass spectrum may either be supplied by the user, or can alternatively be calculated in two different models of SUSY breaking: gravity mediated supersymmetry breaking (SUGRA), and gauge mediated supersymmetry breaking (GMSB). The program incorporates the most important production processes and decay modes, including the full set of R-parity violating decays, and the decays to the gravitino in GMSB models. Initial state radiation corrections take into account PT/PL effects in the Structure Function formalism, and an optimised hadronisation interface to JETSET 7.4 including final state radiation is also provided.

Grc4f v1.1: a four-fermion event generator for e +e − collisions

grc4f is a Monte Carlo package for generating e + e −→4-fermion processes in the standard model. All of the 76 LEP-2 allowed fermionic final state processes evaluated at tree level are included in version 1.1 grc4f addresses event simulation requirements at e + e − colliders such as LEP and upcoming linear colliders. Most of the attractive aspects of grc4f come from its link to the GRACE system: a Feynman diagram automatic computation system. The GRACE system has been used to produce the computational code for all final states, giving a higher level of confidence in the calculation correctness. Based on the helicity amplitude calculation technique, all fermion masses can be kept finite and helicity information can be propagated down to the final state particles. The phase space integration of the matrix element gives the total and differential cross sections, then unweighted events are generated. Initial state radiation (ISR) corrections are implemented in two ways, one is based on the electron structure function formalism and the second uses the parton shower algorithm called QEDPS. The latter can also be applied for final state radiation (FSR) though the interference with the ISR is not yet taken into account. Parton shower and hadronization of the final quarks are performed through an interface to JETSET. Coulomb correction between two intermediate W's, anomalous coupling as well as gluon contributions in the hadronic processes are also included.

FiniteW-width and initial-state radiative corrections to the reactione+e−→W+W−→l+l−νν

Lepton-inclusive cross sections for the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{W}^{+}{W}^{\ensuremath{-}}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}\ensuremath{\nu}\ensuremath{\nu}$ are calculated. The influence of the radiative corrections and a finite decay W width is considered. Its large contribution to the total and, especially, differential cross sections of the final decay leptons is shown. The method to extract ${\ensuremath{\Gamma}}_{W},$ using the leptonic channel of W decay, is proposed.