Hadronic Cross Sections Research Articles

Recent Hadronic Cross Section Measurements from BABAR

New hadronic cross sections measured by the BABAR experiment are presented: e+e−→ π+π−π0π0, e+ e−→ π+π−η, and the kaonic channels e+e−→ KS KLπ0 , KS KLπ0π0 , KS KLη, KS K±π+π0 , KS K±π+η.

Discrete symmetries studies at KLOE-2

The KLOE and KLOE-2 experiments at the Laboratori Nazionali di Frascati (Italy) collected almost 8 fb−1 of integrated luminosity at the energy equal to the mass of ϕ meson. The excellent time resolution of the electromagnetic calorimeter and the very good accuracy on both momentum and vertex reconstruction of the tracking system allow to study discrete symmetries to the utmost precision as well as light meson spectroscopy, dark forces searches, hadronic cross-section measurements and studies of γγ-physics. CPT symmetry test with the lepton charge asymmetry measured in KS semileptonic decays with 1.7 fb−1 of KLOE data, tests of time reversal and CPT in transitions in $\phi \to {K_S}{K_L} \to \pi ev,\,3{\pi ^0}(2{\pi ^0})$ decays with newly acquired data with the KLOE-2 detector will be presented and discussed.

Update on the hadronic vacuum polarisation contributions to muon g − 2 and α(mZ2)

An update of the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic couplings constant at the Z-boson mass is presented. Newest e+e−→ hadrons cross-section data mainly from the BABAR and VEPP-2000 experiments have been included. For the muon (g−2)/2, the lowest-order hadronic contribution is evaluated to be (693.1 ± 3.4) · 10−10, improving the precision of our previous evaluation by 21%. The full Standard Model prediction differs by 3.5 σ from the experimental value. The five-quark hadronic contribution to $ \alpha (\mathop m\nolimits_z^2 ) $ is evaluated to be (276.0 ± 0.9) · 10−4.

Total hadronic cross sections at high energies in holographic QCD

We present our analysis on high energy hadron–hadron scattering in the framework of the holographic QCD. Combining the Brower–Polchinski–Strassler–Tan Pomeron exchange kernel and gravitational form factors of the involved hadrons which are obtained by using the bottom-up AdS/QCD models in the five-dimensional AdS space, we calculate the total cross sections at high energies. We show that our calculations for the nucleon–nucleon scattering agree with the experimental data including the recent ones taken by the TOTEM collaboration at the LHC. The present framework is applicable to any high energy process, in which the strong interaction can be approximated by the Pomeron exchange. We present the results for the pion–nucleon and pion–pion scattering as examples, which can be obtained without any additional parameter because all the adjustable parameters are fixed via the analysis on the nucleon–nucleon scattering. The resulting total cross section ratios are σtotπN/σtotNN=0.63 and σtotππ/σtotNN=0.45, respectively.

Collider experiment SND and Precision Physics with hadronic e+e- cross sections

The Spherical Neutral Detector (SND) is an experiment for e+e− annihilation study at low energies 0.2−2 GeV. The light quark anti−quark bound states are the main subject of study at these energies. They express themselves as resonances in the e+e− hadronic cross sections. Hadronic cross sections could be recalculated to hadronic vacuum polarization (HVP). The Standard Model predictions today are limited by HVP which is not calculable with modern QCD theory. In this talk we present the review of the hadronic cross sections measurements at SND and new measurements: e+e− → π+π−, π0γ, π+π−π0, ωπ0, K+K−η, η, KsKLπ0, π+π−π0η, ωπ0η e.t.c.

An operational definition of quark and gluon jets

While “quark” and “gluon” jets are often treated as separate, well-defined objects in both theoretical and experimental contexts, no precise, practical, and hadron-level definition of jet flavor presently exists. To remedy this issue, we develop and advocate for a data-driven, operational definition of quark and gluon jets that is readily applicable at colliders. Rather than specifying a per-jet flavor label, we aggregately define quark and gluon jets at the distribution level in terms of measured hadronic cross sections. Intuitively, quark and gluon jets emerge as the two maximally separable categories within two jet samples in data. Benefiting from recent work on data-driven classifiers and topic modeling for jets, we show that the practical tools needed to implement our definition already exist for experimental applications. As an informative example, we demonstrate the power of our operational definition using Z+jet and dijet samples, illustrating that pure quark and gluon distributions and fractions can be successfully extracted in a fully well-defined manner.

Analytical Method for Next-to-Leading-Order QCD Corrections to Double-Higgs Production.

We propose a new method to calculate analytically higher-order perturbative corrections and we apply it to the calculation of the two-loop virtual corrections to Higgs pair production through gluon fusion. The method is based on the expansion of the amplitudes in terms of a small Higgs transverse momentum. This approach gives a very good approximation (better than per mille) of the partonic cross section in the center-of-mass energy region sqrt[s[over ^]]≲750 GeV, where ∼95% of the total hadronic cross section is concentrated. The presented method is general and can be applied in a straightforward way to the computation of virtual higher-order corrections to other 2→2 processes, representing an improvement with respect to calculations based on heavy mass expansions.

Complete electroweak two-loop corrections to Z boson production and decay

This article presents results for the last unknown two-loop contributions to the Z-boson partial widths and Z-peak cross-section. These are the so-called bosonic electroweak two-loop corrections, where “bosonic” refers to diagrams without closed fermion loops. Together with the corresponding results for the Z-pole asymmetries Al,Ab, which have been presented earlier, this completes the theoretical description of Z-boson precision observables at full two-loop precision within the Standard Model. The calculation has been achieved through a combination of different methods: (a) numerical integration of Mellin–Barnes representations with contour rotations and contour shifts to improve convergence; (b) sector decomposition with numerical integration over Feynman parameters; (c) dispersion relations for sub-loop insertions. Numerical results are presented in the form of simple parameterization formulae for the total width, ΓZ, partial decay widths Γe,μ,Γτ,Γν,Γu,Γc,Γd,s,Γb, branching ratios Rl,Rc,Rb and the hadronic peak cross-section, σhad0. Theoretical intrinsic uncertainties from missing higher orders are also discussed.

A statistical method to estimate low-energy hadronic cross sections

In this article we propose a model based on the Statistical Bootstrap approach to estimate the cross sections of different hadronic reactions up to a few GeV in c.m.s energy. The method is based on the idea, when two particles collide a so called fireball is formed, which after a short time period decays statistically into a specific final state. To calculate the probabilities we use a phase space description extended with quark combinatorial factors and the possibility of more than one fireball formation. In a few simple cases the probability of a specific final state can be calculated analytically, where we show that the model is able to reproduce the ratios of the considered cross sections. We also show that the model is able to describe proton\,-\,antiproton annihilation at rest. In the latter case we used a numerical method to calculate the more complicated final state probabilities. Additionally, we examined the formation of strange and charmed mesons as well, where we used existing data to fit the relevant model parameters.

Exploring Partonic Structure of Hadrons Using abinitio Lattice QCD Calculations.

Following our previous proposal, we construct a class of good "lattice cross sections" (LCSs), from which we can study the partonic structure of hadrons from abinitio lattice QCD calculations. These good LCSs, on the one hand, can be calculated directly in lattice QCD, and on the other hand, can be factorized into parton distribution functions (PDFs) with calculable coefficients, in the same way as QCD factorization for factorizable hadronic cross sections. PDFs could be extracted from QCD global analysis of the lattice QCD generated data of LCSs. We also show that the proposed functions for lattice QCD calculation of PDFs in the literature are special cases of these good LCSs.

Measurement of the hadronic cross sections with the CMD-3 and SND detectors at the VEPP-2000 collider

Since December 2010 the CMD-3 and SND detectors detectors collect data at the VEPP-2000 electron-positron collider. In 2013-2015 the injection facility of the collider has undergone an upgrade of the injection system. The new BINP injection complex has been connected to the VEPP-2000 collider, so the restrictions connected to the lack of positrons and limited beam energy transfer do not apply any more. The collider luminosity in whole energy range is restricted now only by beam-beam effects. VEPP-2000 collider started to collect data with two detectors at 2016 year. The collected data sample since 2010 corresponds more than 100 pb-1 of integrated luminosity per detector in the c.m. energy between 0.32 and 2GeV. We will report here results of analysis of various hadronic cross sections from detectors both published and preliminary. These measurements are important by themselves and also because of the implications for anomaly of the magnetic moment of a muon (g-2) discrepancy.

Measurement of hadronic cross sections with BABAR

The BABAR Collaboration pursues an intensive program studying hadronic cross sections in low-energy electron-positron annihilations, accessible via initial-state radiation. Our measurements allow significant improvements in the precision of the predicted value of the muon anomalous magnetic moment. These improvements are necessary for shedding light on the current 3 σ difference between the predicted and the experimental values. We have published results on a number of processes with from two to six hadrons in the final state and other final states are currently under investigation. We report here on the most recent results obtained by analysing the entire BABAR dataset. We present in particular the measurement of the mode with two charged pions and two neutral pions and the measurement of the full set of final states with two kaons and one or two pions.

Initial State Radiation Measurements at BESIII

A difference of more than three standard deviations between is currently observed between the direct experimental measurement and the Standard Model prediction of the anomalous magnetic moment of the muon (g−2)μ. The hadronic vacuum polarization contributions can be related to hadronic cross sections using the optical theorem. Precision measurements of the hadronic cross sections e+e−→π+π−, π+π−π0, π+π−2π0, ωπ0 and π+π−3π0 are performed at the BESIII experiment located in Beijing, China. The initial state radiation method is used to access the energy regions of interest for (g−2)μ. Our results will improve the precision of the Standard Model prediction of (g−2)μ.

Hadronic cross sections with the CMD-3 detector at the VEPP-2000

This paper reports measurements of the hadronic cross sections with the CMD-3 detector at the VEPP-2000 electron-positron collider. The overall size of the data sample analyzed is about 60 pb-1, collected by the CMD- 3 running since December 2010 up to June 2013 in the c.m. energy range from 0.32 to 2.0 GeV. The preliminary results of data analysis for various modes of e+e−→hadrons are discussed.

ϕ Meson Measurements at RHIC with the PHENIX Detector

The measurement of ϕ mesons provides key information on the phase of the hot and dense medium created in the relativistic heavy ion collisions. It has a relatively small hadronic interaction cross section and is sensitive to the increase of strangeness (strangeness enhancement), a phenomenon associated with soft particles in bulk matter. Measurements in the dilepton channels are especially interesting since leptons interact only electromagnetically, thus carrying the information from their production phase directly to the detector. Measurements in different nucleus-nucleus collisions allow us to perform a systematic study of the nuclear medium effects on ϕ meson production. The PHENIX detector provides the capabilities to measure the ϕ meson production in a wide range of transverse momentum and rapidity to study these effects. In this proceeding, we present measurements of the ϕ mesons in a variety of collision systems at [see formula in PDF] = 200 GeV. In case of small systems, the data are compared with AMPT calculations to study the various cold nuclear medium effects involved in ϕ meson production.

Form Factor Measurements at BESIII for an Improved Standard Model Prediction of the Muon g-2

The anomalous part of the magnetic moment of the muon, (g-2)[Formula: see text], allows for one of the most precise tests of the Standard Model of particle physics. We report on recent results by the BESIII Collaboration of exclusive hadronic cross section channels, such as the 2[Formula: see text], 3[Formula: see text], and 4[Formula: see text] final states. These measurements are of utmost importance for an improved calculation of the hadronic vacuum polarization contribution of (g-2)[Formula: see text], which currenty is limiting the overall Standard Model prediction of this quantity. BESIII has furthermore also intiatated a programme of spacelike transition form factor measurements, which can be used for a determination of the hadronic light-by-light contribution of (g-2)[Formula: see text] in a data-driven approach. These results are of relevance in view of the new and direct measurements of (g-2)[Formula: see text] as foreseen at Fermilab/USA and J-PARC/Japan.

From Hadronic Cross Section to the measurement of the Vacuum Polarization at KLOE: a fascinating endeavour

The KLOE experiment at the ϕ-factory DAΦNE in Frascati is the first to have employed Initial State Radiation (ISR) to precisely determine the e+e− → π+π−(γ) cross section below 1 GeV. Such a measurement is particularly important to test the Standard Model (SM) calculation for the (g – 2) of the muon, where a long standing 3σ discrepancy is observed. I will review the ISR activity in KLOE in the last 20 years from the measurement of the hadronic cross section to the first direct determination of the time-like complex running α(s) in the region below 1 GeV.

Holographic description of total hadronic cross sections at high energies

We investigate the hadron-hadron total cross sections at high energies in the framework of holographic QCD. In our model setup, the involved strong interaction is described by the Brower-Polchinski-Strassler-Tan Pomeron exchange kernel, and the two form factors are obtained from the bottom-up AdS/QCD models. We show that the resulting nucleon-nucleon total cross section is consistent with the experimental data recently measured by the TOTEM collaboration at the LHC. As examples to see the general versatility of the model, we also present our analysis on the pion-nucleon and pion-pion cases, which can be predicted because all the adjustable parameters are fixed by the nucleon-nucleon data.

Reevaluation of the hadronic vacuum polarisation contributions to the Standard Model predictions of the muon g-2 and {alpha (m_Z^2)} using newest hadronic cross-section data

We reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the Z-boson mass. We include newest e^+e^- rightarrow mathrm{hadrons} cross-section data (among others) from the BABAR and VEPP-2000 experiments. For the muon (g-2)/2 we find for the lowest-order hadronic contribution (693.1 pm 3.4)times 10^{-10}, improving the precision of our previous evaluation by 21%. The full Standard Model prediction differs by 3.5,sigma from the experimental value. The five-quark hadronic contribution to alpha (m_Z^2) is evaluated to be (276.0pm 0.9)times 10^{-4}.

Leading components in forward elastic hadron scattering: Derivative dispersion relations and asymptotic uniqueness

Forward amplitude analyses constitute an important approach in the investigation of the energy dependence of the total hadronic cross-section [Formula: see text] and the [Formula: see text] parameter. The standard picture indicates for [Formula: see text] a leading log-squared dependence at the highest c.m. energies, in accordance with the Froissart–Lukaszuk–Martin bound and as predicted by the COMPETE Collaboration in 2002. Beyond this log-squared (L2) leading dependence, other amplitude analyses have considered a log-raised-to-gamma form [Formula: see text], with [Formula: see text] as a real free fit parameter. In this case, analytic connections with [Formula: see text] can be obtained either through dispersion relations (derivative forms), or asymptotic uniqueness (Phragmén–Lindelöff theorems). In this work, we present a detailed discussion on the similarities and mainly the differences between the Derivative Dispersion Relation (DDR) and Asymptotic Uniqueness (AU) approaches and results, with focus on the [Formula: see text] and L2 leading terms. We also develop new Regge–Gribov fits with updated dataset on [Formula: see text] and [Formula: see text] from [Formula: see text] and [Formula: see text] scattering, including all available data in the region 5 GeV–8 TeV. The recent tension between the TOTEM and ATLAS results at 7 TeV and mainly at 8 TeV is discussed and considered in the data reductions. Our main conclusions are the following: (1) all fit results present agreement with the experimental data analyzed and the goodness-of-fit is slightly better in case of the DDR approach; (2) by considering only the TOTEM data at the LHC region, the fits with L[Formula: see text] indicate [Formula: see text] (AU approach) and [Formula: see text] (DDR approach); (3) by including the ATLAS data the fits provide [Formula: see text] (AU) and [Formula: see text] (DDR); (4) in the formal and practical contexts, the DDR approach is more adequate for the energy interval investigated than the AU approach. A pedagogical and detailed review on the analytic results for [Formula: see text] and [Formula: see text] from the Regge–Gribov, DDR and AU approaches is presented. Formal and practical aspects related to forward amplitude analyses are also critically discussed.